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Electric Motor-Driven Mine Equipment and Accessories and High- Voltage Longwall Equipment Standards for Underground Coal Mines [03/11/2002]
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Volume 67, Number 47, Page 10971-11005
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Part II
Department of Labor
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Mine Safety and Health Administration
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30 CFR Parts 18 and 75
Electric Motor-Driven Mine Equipment and Accessories and High-Voltage
Longwall Equipment Standards for Underground Coal Mines; Final Rule
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DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 18 and 75
RIN 1219-AA75
Electric Motor-Driven Mine Equipment and Accessories and High-
Voltage Longwall Equipment Standards for Underground Coal Mines
AGENCY: Mine Safety and Health Administration (MSHA), Labor.
ACTION: Final rule.
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SUMMARY: This final rule establishes MSHA's new mandatory electrical
safety standards for the installation, use, and maintenance of high-
voltage longwall mining systems used in underground coal mines. The
final rule also includes design approval requirements for high-voltage
equipment operated in longwall face areas of underground mines. These
provisions allow the use of high-voltage longwall face equipment with
enhanced safety protection from fire, explosion, and shock hazards. In
addition to providing a safer mining environment and facilitating the
use of advanced equipment designs, the final rule reduces paperwork
requirements by eliminating the need for petitions for modification
(variances).
DATES: This regulation is effective May 10, 2002. The incorporation by
reference of certain publications listed in the rule is approved by the
Director of the Federal Register May 10, 2002.
FOR FURTHER INFORMATION CONTACT: Marvin W. Nichols, Jr., Director,
Office of Standards, Regulations and Variances, MSHA, 4015 Wilson
Boulevard, Arlington, Virginia 22203-1984. Mr. Nichols can be reached
at nichols-marvin@msha.gov (Internet
e-mail), 703--235-1910 (voice), or 703-235-5551 (fax). You may obtain
copies of the final rule in alternative formats by calling this number.
The alternative formats available are either a large print version of
the final rule or the final rule in an electronic file on computer
disk. The final rule also is available on the Internet at http://
www.msha.gov/REGSINFO.HTM.
SUPPLEMENTARY INFORMATION:
I. Background
On December 4, 1989, the Mine Safety and Health Administration
(MSHA) published a proposed rule (54 FR 50062) to revise its electrical
safety standards for underground coal mines. That proposed rule
addressed all of the Agency's electrical standards for underground coal
mines and allowed the use of high-voltage longwall equipment. However,
it did not specifically focus on the safety issues related to the use
of high-voltage longwall equipment. The Agency published a new proposed
rule (57 FR 39036) on August 27, 1992, related specifically to the safe
use of high-voltage longwall equipment in underground coal mines. These
rules also specifically addressed approval requirements for high-
voltage electrical equipment operated in longwall face areas of
underground coal mines. The comment period on the proposed rule was
scheduled to close on October 23, 1992, but was extended to November
13, 1992 (57 FR 48350). On October 18, 1995, (60 FR 53891), MSHA
reopened the rulemaking record for additional comments to the proposed
rule to provide all interested parties an opportunity to submit
additional comments. The comment period was scheduled to close on
November 14, 1995, but was extended to December 18, 1995 (60 FR 57203).
The Agency received no requests for a public hearing on the proposed
rule. The record was reopened December 28, 1999, for comments on the
updated Preliminary Regulatory Impact Analysis (PRIA). The record
closed February 28, 2000. Only one comment was received. The commenter
agreed with our economic analysis of the cost impact of the proposed
rule.
These revised standards allow the use of high-voltage longwall
mining systems. Longwall mining methods have undergone numerous
advances in technology during the past 25 years. These technological
advances have led to improved and safer systems. The additional
requirements under 30 CFR part 18 provide enhanced safety protections
that are consistent with advances in mine technology that allows high-
voltage switchgear to be used on face equipment. Title 30 CFR parts 18
and 75 of this final rule implements a number of changes to approval
and safety requirements for high-voltage equipment to accommodate the
advances in technology in a manner that protects the safety of miners.
A. Part 18 Electric Motor-Driven Mine Equipment and Accessories
Electrical equipment horsepower in mines has increased over the
years. The voltages required to operate this equipment have also
increased to accommodate the design of practical and efficient
equipment. The design of safe, efficient, and practical high-voltage
electric equipment has improved dramatically in recent years. Because
of the industry's need for higher voltages and the marked improvement
in the design and manufacturing technology of high-voltage components,
MSHA developed rules that establish requirements for safe high-voltage
electric equipment use. This rule provides improved design requirements
for longwall equipment, consistent with existing requirements in 30 CFR
part 18, and contains provisions that accommodate new design
technology, are practical, and lessen burdens on the mining community,
while preserving safety and health protections for miners.
The safety criteria supporting the rule are based on research
conducted over the past 18 years by the former U.S. Bureau of Mines
(USBM) and MSHA. USBM functions are now a part of the National
Institute of Occupational Safety and Health. This research included the
following: (1) Foster-Miller research, under USBM contract No.
H0308093, which developed a recommended high-voltage permissible
loadcenter criteria; (2) MSHA research, under USBM contract No.
J0333909, which resulted in modified criteria to address high-voltage
permissible switchgear enclosures and the development of test
facilities for acceptance of high-voltage permissible loadcenters and
switchgear enclosures; (3) Follow-up MSHA inspections on high-voltage
machines and longwall mining systems operating under experimental
permits to confirm design requirements and operational safety; (4) MSHA
internal research and review of engineering reports for further
analysis of hazards relating to explosion-proof enclosures which
contain high-voltage switching; and, (5) Input from various technical
experts throughout the mining community. These criteria are technically
sound and have the general consensus of the mining community, including
equipment manufacturers and other interested parties.
The first high-voltage longwall system started operating in 1985.
Since that time we have issued approximately 130 system design
approvals for high-voltage longwall equipment. Over the last 16 years,
no electrical-type fatalities or serious injuries occurred to miners
because of high-voltage equipment used in accordance with over 100
granted high-voltage petitions for modification (petitions). Because of
this new improved high-voltage technology, the designed safety benefits
and the observed use experience, MSHA is revising its existing 30 CFR
part 18 electric motor-driven mine equipment and accessories approval
requirements by adding specific design requirements
[[Page 10973]]
for high-voltage longwall equipment in underground mines.
MSHA received comments from all segments of the mining industry,
and the final rule addresses these comments. Many commenters were in
favor of the new approval requirements and were in agreement on the
majority of the provisions in the proposed rule. MSHA carefully
reviewed all of the comments. This resulted in the modification of four
of the sixteen technical requirements addressed in the proposed rule.
We considered the views of all interested parties, including: mine
operators; equipment manufacturers; miners' representatives; and other
government agencies in developing this final rule.
MSHA is publishing this high-voltage longwall approval rule (30 CFR
part 18) along with mandatory safety standards regarding high-voltage
longwall equipment (30 CFR part 75). This new 30 CFR part 18 rule
provides additional high-voltage equipment specifications that must be
followed by the manufacturer in order to obtain MSHA approval of the
equipment. The new 30 CFR part 75 rule provides installation, use, and
maintenance requirements for high-voltage longwalls in underground coal
mines.
B. Part 75 High-Voltage Longwall Equipment Safety Standards
This part of the final rule provides safety requirements for
underground high-voltage longwall systems. Currently, longwall mining
is permitted under MSHA's existing standards only if it uses low- or
medium-voltage electrical power. High-voltage longwall systems are
being used, but only when approved by MSHA through the petition for
modification process under Sec. 101(c) of the Federal Mine Safety and
Health Act of 1977 (Mine Act). During the last 15 years, MSHA has
evaluated the safe use of high-voltage longwall equipment, under a
petition process that permits a mine operator to request that the
application of a safety standard be modified at a particular mine. MSHA
grants a petition when it determines that a mine operator has an
alternative method which provides the same measure of safety protection
as the existing standard, or when the existing standard would result in
diminished safety protection to miners. Over the past 15 years, MSHA
has granted over 100 petitions for modification to use high-voltage
electrical power with longwalls. In the Agency's evaluation of the use
of high-voltage longwall mining systems, MSHA concluded that they can
be safely used, provided that certain conditions are met. Specifically,
the Agency found that the previous safety concerns about explosion,
fire and shock hazards initially associated with high-voltage use are
sufficiently addressed by this newly-developed technology. In each of
the petition cases the Agency granted, MSHA performed a specific on-
site investigation to verify this finding. For example, we recognized
that high-voltage electric equipment and circuit design improvements in
combination with sensitive electrical circuit protections reduce fire,
explosion and shock hazards. Newly designed cable handling systems
provide additional safety protections against electrical shock, fire
and explosion hazards when the cable is moved. Further, lighter power
cables are available which reduce back strain and other injury risks to
miners from the heavier cable lifting and hauling often associated with
the moving or lifting of low- to medium-voltage cables. Moreover, there
have been no electrical fatalities and no serious electrical injuries
to miners from high-voltage equipment used under the granted
modifications.
Because of the new improved high-voltage technology, with its
attendant safety benefits, MSHA is revising its existing 30 CFR part 75
electrical safety standards. This final rule does not reduce the
protection afforded by existing 30 CFR part 75 standards. It does,
however, provide increased protection from electrical hazards, and
reduces paperwork burden. It also reduces the time and cost to all
parties associated with the petition for modification process. This
final rule is implemented in conjunction with revisions to 30 CFR part
18, that address approval requirements for high-voltage equipment. The
additional requirements under 30 CFR part 18 are also consistent with
advances in mine technology, allowing high-voltage switchgear to be
used on face equipment with enhanced safety protection from fire,
explosion and shock hazards.
MSHA received comments from all segments of the mining community.
Comments from labor, industry and manufacturers generally agree with
the proposed rule. The final rule, to the extent feasible and
appropriate, responds to commenters' concerns and reflects general
consensus of various parties. However, MSHA did not adopt all comments
received.
Joint commenters representing both industry and labor recommended
that operators mining under granted high-voltage petitions containing
non-electrical provisions continue to comply with such provisions.
Labor commenters requested that standards addressing high-voltage
longwalls also include provisions addressing non-electrical safety and
health areas. Specifically, they noted that high-voltage longwall
systems of extended widths and lengths can adversely affect not only
ventilation, but shearer mounted methane monitors, intake escapeways,
exposure to respirable dust, tailgate travelways, and storage plans for
self-contained self-rescuers (SCSR's), as well as return entry
rockdusting during mining.
It is the Agency's view that non-electrical safety and health
issues related to the use of high-voltage longwalls are fully addressed
by existing safety and health standards under 30 CFR parts 70 and 75.
This view has been upheld by administrative law judge, Assistant
Secretary and Court of Appeals decisions. UMWA v. Federal Mine Safety
and Health Administration, 931 F. 2d 908,913 (D.C. Cir. 1991). The
promulgated standards relating to ventilation and escapeways under 30
CFR 75.300 et seq. (61 FR 9764, March 11, 1996) provide protection with
respect to ventilation and escapeways. Mandatory health standards under
part 70 address exposures to respirable dust. Section 75.215--Longwall
mining systems--addresses longwall tailgate travelway protection.
Storage plans for SCSRs may be approved by MSHA District Managers in
accordance with the specific conditions at each mine under
Sec. 75.1714-2--Self-rescue devices; use and location requirements.
Existing Sec. 75.400--Accumulation of combustible materials--provides
protection against float coal dust and Sec. 75.402--Rock dusting--
requires adequate rockdusting measures. MSHA continues to work on
improved respirable dust protection requirements in response to
recommendations made by the Secretary of Labor's Advisory Committee on
the Elimination of Pneumoconiosis Among Coal Mine Workers.
MSHA is aware that several granted modifications for high-voltage
longwalls contain non-electrical requirements specific to the affected
mine. These requirements are the result of settlement negotiations
arising out of the petition process and are not required as part of
this electrical standard. Parties to the current petition process may,
through a voluntary, cooperative effort, continue to follow the non-
electrical provisions after this final rule becomes effective.
Moreover, as indicated above, existing and new standards substantially
address these concerns and result in no diminution of safety and health
protection currently afforded to miners. Moreover, the Agency
continually reviews existing standards for
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improvements that will enhance miner safety.
Some commenters suggested that the final rule allow a longer phase-
in period, where equipment modifications are necessary. The Agency does
not believe that a delayed effective date is necessary. Many operators
are already complying with these requirements under the petition for
modification process and the modern technology necessary to implement
the final rule is readily available.
II. Discussion of Final Rule
The following section-by-section portion of the preamble discusses
each provision affected, starting with the provisions in part 18. The
text of the final rule is included at the end of the document.
Part 18 Electric Motor-Driven Mine Equipment and Accessories
This final rule addresses only those areas where specific additions
to 30 CFR part 18 are necessary for the approval of high-voltage
longwalls. The existing requirements of 30 CFR part 18 that apply to
this equipment have not been revised. Examples of these types of
requirements are the general construction requirements of the high-
voltage enclosures and the short-circuit and overload protection to be
provided. The overload and short-circuit protective device settings
were not revised and will continue to be evaluated under existing
requirements and Agency policy.
The main safety protections addressed in the final rule are
summarized into four areas: (1) Prevention of a high-voltage arc from
occurring; (2) Prevention of the resulting heat or flame from igniting
a methane-air mixture surrounding the machine if an arc or methane
explosion occurs; (3) Prevention of enclosure failure from an increased
pressure rise if an arc or methane explosion occurs within the
explosion-proof enclosure; and, (4) Personal protection for miners from
electrical shock hazards when working in or around the high-voltage
equipment.
Section 18.53 High Voltage Longwall Mining Systems (Nameplate Ratings
From 1,001 Volts Through 4,160 Volts)
Paragraph (a) of this final rule requires the separation of
compartments containing low- and medium-voltage circuits from those
with high-voltage circuits in each motor-starter enclosure by location,
partitions or barriers. Partitions and barriers, under this final rule,
like the proposed rule, are required to be constructed of grounded
metal or nonconductive insulating board. These requirements protect
against shock hazards which may arise from inadvertent contact with
energized high-voltage circuits. With the exception of a controller on
a shearer, compliance with this section requires the components within
each high-voltage motor-starter enclosure be segregated into separate
compartments by voltage classification. The installation of the
barriers and partitions provides separation of components in each high-
voltage motor-starter enclosure. When complete separation of voltage
classifications is not possible with barriers or partitions where both
medium- and high-voltage circuits or both low- and high-voltage
circuits are connected to a component or device, that component is
required to be located in the motor contactor or disconnect device
compartment.
This rule covers both explosion-proof and nonexplosion-proof motor-
starter enclosures that are presently used by the mining industry.
MSHA's policy has been to require barriers and partitions to separate
the disconnect device compartment, control/communications compartment
and motor contactor compartment in both power centers and motor-starter
enclosures. If a motor-starter enclosure is part of a power center,
then the partitions and barriers required by this rule only apply to
barriers and partitions for the disconnect device compartment, control/
communications compartment, and motor-starter compartment of the power
center. This rule does not apply to other parts of the power center or
to separate power centers that supply power to motor-starter
enclosures. The mining industry presently provides barriers for power
centers to separate high-voltage components from low- and medium-
voltage circuits and equipment. MSHA encourages the industry to
continue to provide barriers and partitions in power centers to
minimize shock hazards by limiting exposure of personnel to high-
voltage components when troubleshooting and testing low- and medium-
voltage circuits. If barriers and partitions are not provided on power
centers, the power center must be deenergized from an outby set of
high-voltage visible disconnects and the high-voltage circuit grounded
before troubleshooting and testing is performed on low- or medium-
voltage circuits or equipment in the same compartment with high-voltage
circuits or equipment.
Commenters suggested that, because of overall machine design
considerations, an exception be provided for the controller on a
shearer. In response to this comment, MSHA acknowledges that a shearer
is a special case. The shearer is not required under Sec. 18.53(f) to
have a disconnect switch. Therefore, in an effort to address this
issue, the final rule has been modified exempting the requirements of
paragraph (a) when applied to a shearer.
One commenter recommended that the term ``location'' be deleted
from the final rule, suggesting that there must be a physical
separation within compartments to prevent accidental contact with a
high-voltage circuit while troubleshooting low- and medium-voltage
circuits. Another commenter proposed the use of separate compartments
having explosion-proof walls between one compartment and the next. As
noted in the proposed rule, the intent of this provision is to minimize
shock hazards by preventing exposure of personnel to high-voltage
components when troubleshooting and testing low- and medium-voltage
circuits in accordance with Sec. 75.820. MSHA believes that this can be
accomplished by various types of partitions or barriers, including
designing the enclosure into several separate explosion-proof
compartments. When designing the partitions or barriers, however,
consideration should be given to possible effects of pressure-piling
within the enclosure. The use of the word ``location'', in the proposed
rule allowed the option of having separate enclosures to house the
various compartments, as noted by the commenter. In response to these
comments, the final rule removes the word ``location'' to provide for
flexibility, but clarifies that the requirement applies to each motor-
starter enclosure.
Comments were also received suggesting that we change the word
``board'' to ``material'' in regard to construction of barriers and
partitions. Since the word ``board'' suggests a more sturdy barrier
than ``material,'' the final rule remains as proposed.
Paragraph (b) of the final rule, like the proposed rule, requires
motor-starter enclosure compartment(s) containing high-voltage
components be provided with cover interlock switches. These interlock
switches will protect miners entering enclosures from shock hazards
resulting from accidental contact with energized circuits. A minimum of
two interlock switches per cover is required and must be wired into the
circuitry so that operation of either switch will deenergize the
incoming high-voltage circuits. The Agency believes that a second
switch coupled with required maintenance under 30 CFR 75.512 will
provide the necessary protection to ensure that the high-voltage
circuits are deenergized whenever a cover is
[[Page 10975]]
removed. MSHA recommends either a magnetic or a whisker-type switch.
MSHA's follow-up inspections of high-voltage equipment with plunger-
operated switches reveal that these switches may stick and not operate
effectively after exposure to the mine environment.
This rule covers both explosion-proof and nonexplosion-proof high-
voltage motor-starter enclosures. MSHA's high-voltage longwall
petitions require interlock switches for high-voltage compartments in
both power centers and motor-starter enclosures. When a motor-starter
enclosure is part of a power center, the interlock switches required by
this rule only apply to motor-starter compartments of the power center.
This rule does not apply to other parts of the power center or to
separate power centers that supply power to motor-starter enclosures.
The mining industry presently provides interlock switches for high-
voltage compartments on power centers. MSHA encourages the industry to
continue to provide interlocks switches for high-voltage compartments
of power centers.
There were no comments on this paragraph. However, the last
sentence of the proposed rule was deleted to clarify the Agency's
intent that at least two switches be used to satisfy 30 CFR part 18.53
(b) requirements.
Paragraph (c) of the final rule, like the proposed rule, requires
that circuit-interrupting devices installed in motor-starter enclosures
be designed and installed to prevent automatic reclosure. Compliance
with this provision protects miners working on the circuit or in other
hazardous situations from unanticipated reenergization of the circuit.
For example, faults occur in underground electrical systems as a result
of roof fall damage or equipment insulation failure. Under such
circumstances, the use of automatic reclosing circuit-interrupting
devices would create shock and fire hazards should the devices reclose
automatically when a short-circuit or ground-fault condition exists in
the circuit. There were no comments on this paragraph. Therefore, the
language in the final rule has not been changed from the proposed rule.
Paragraph (d) of the final rule, like the proposed rule, specifies
that control transformers installed in each longwall motor-starter
enclosure or control transformers that supply control power to each
longwall motor-starter enclosure, must have electrostatic (Faraday)
shielding, grounded by at least a No. 12 American Wire Gauge (AWG)
grounding conductor, installed between the primary and secondary
windings. Compliance with this provision protects against shock hazards
should a fault develop between the primary and secondary windings.
Faraday shielding provides electrical isolation between the high-
voltage primary and low-voltage secondary windings of these
transformers. As a secondary benefit, Faraday shielding of control
transformers assures that transients occurring on the primary circuit
are not transferred to the secondary circuit. Such transients could
cause premature damage to electrical control equipment and create an
economic burden for the mining industry.
This rule requires Faraday shielding for control transformers
located in both explosion-proof and nonexplosion-proof motor-starter
enclosures that are presently used by the mining industry. Also, this
rule requires Faraday shielding for control transformers that supply
motor-starter compartments, even if the control transformer is located
in a separate power center. This rule does not cover control
transformers for power centers that do not supply power to the motor-
starter enclosure.
Paragraph (d) also requires the secondary nominal voltage of the
control transformer be no more than 120 volts, line-to-line. This is
consistent with the existing policy interpretation of 30 CFR part 18
control voltage limitations under Sec. 18.47. There were no comments on
this paragraph and therefore, the wording remains the same as the
proposed rule.
Paragraph (e) of the final rule, like the proposed rule, requires
test circuits to verify the integrity and proper operation of the
ground-wire monitors and ground-fault protective devices. Test circuits
for ground-wire monitors and ground-fault circuits assure that the
circuits can be tested frequently in a manner that minimizes the
hazards to personnel conducting the tests. Incorporating these test
circuits into the longwall circuitry eliminates the need to test these
protective devices by other means that could result in a shock hazard
by placing personnel in close proximity to exposed energized
conductors.
Some commenters noted that the testing of backup ground-fault
devices located across the grounding resistor would require the
application of an actual phase-to-ground fault, which could be
hazardous. These commenters suggested that the ground-fault test
circuit inject a primary current into the transformer and not subject
the equipment to an actual phase-to-ground fault. In addition, another
commenter supported the opinion that it is a dangerous practice to test
ground-fault protection by making direct connections between phase and
ground, and stated that MSHA should establish a policy on this so that
the matter is resolved.
In response to these comments, unlike the proposed rule, the final
rule includes a requirement that each ground-fault test circuit be
designed to inject a primary current of 50 percent or less of the
maximum ground-fault current through the current transformer to cause
the corresponding circuit-interrupting device to open. This requirement
is necessary to reduce the likelihood of a hazardous condition
resulting from a phase-to-ground fault. A similar requirement is added
to the final rule under 30 CFR 75.814(c).
Paragraph (f) of the final rule requires each longwall motor-
starter enclosure, with the exception of a controller on a shearer, to
be equipped with a disconnect device. Opening of the device deenergizes
all high-voltage power conductors extending from the enclosure, except
the conductors supplying power to the enclosure. Compliance with this
paragraph provides for convenient and safe deenergization of high-
voltage circuits and other components during testing and
troubleshooting work, thus minimizing shock hazards.
A joint industry commenter suggested that the word ``incoming'' be
inserted before the phrase ``disconnect device''. MSHA believes this is
implied, since the device must deenergize all high-voltage power
conductors extending from the enclosure. Therefore, the language of
final rule remains as proposed.
Paragraph (f)(1) of the final rule, like the proposed rule,
specifies that a single handle provide for simultaneous operation
through a mechanical connection of multiple switches located within an
enclosure. The simultaneous operation of multiple disconnect devices by
the use of a single handle ensures that all high-voltage conductors
extending from the enclosure are deenergized when the disconnect device
is in the open position. This arrangement ensures that personnel
entering other enclosures are protected from a shock hazard resulting
from accidental contact with energized circuits in the event the wrong
circuit is disconnected.
The words ``isolator switch'' and ``switches'' were removed in the
final rule to minimize confusion. There were no comments on this
paragraph and the language in the proposed rule remains unchanged
except for the above clarifications.
[[Page 10976]]
Paragraph (f)(2) of the final rule, like the proposed rule, further
defines the requirements of a disconnect device. The switch must be
rated for the maximum phase-to-phase circuit voltage of the system. The
ability to verify, by visual observation, that the switch's contacts
are opened is also required. This verification must be determined
without the removal of any enclosure cover. The removal of an enclosure
cover to verify opening of the contacts presents an increased shock
hazard to miners because of exposed energized high-voltage components.
Also included under this paragraph are the requirements that all
load-side power conductors be grounded and the device be provided with
a means to be locked when the device is in the ``open'' position. These
requirements guard against the hazard of maintenance personnel being
exposed to high-voltage energized parts due to residual voltage or
inadvertent energization of the circuit.
The final requirements of this paragraph address the interrupting
capability of the disconnect device. A disconnect device installed in
an explosion-proof enclosure must be designed and installed to cause
the current to be interrupted automatically prior to the opening of the
device. This requirement addresses the concern about an explosion-proof
enclosure failure because of an increased pressure rise. This pressure
rise can result when an arc or methane explosion occurs within the
explosion-proof enclosure. When the enclosure is not explosion-proof,
as in outby switching, the device is required to either be installed in
the circuit so that the circuit is automatically interrupted prior to
the opening of the device or the device is required to be capable of
interrupting the full-load current of the circuit. There were no
comments on this paragraph and the language in the proposed rule
remains unchanged in the final rule.
Paragraph (g) of the final rule addresses the interlocking of the
disconnect device. These interlocking requirements reduce shock hazards
by increasing the probability that the high-voltage circuits will be
isolated and deenergized prior to performing testing and
troubleshooting on the low- and medium-voltage circuits and ensure that
high-voltage circuits may only be energized at the proper time
following this activity.
This rule covers both explosion-proof and nonexplosion-proof motor-
starter enclosures that are presently used by the mining industry.
MSHA's policy has been to interlock disconnects with the control
circuit in both power centers and motor-starter enclosures. If a motor-
starter enclosure is part of a power center, then this rule covers the
power center. This rule does not apply to separate power centers that
supply power to motor-starter enclosures. The mining industry presently
provides this interlocking of the disconnect device for power centers.
MSHA encourages the industry to continue to interlock disconnects with
the control circuits to facilitate troubleshooting and testing high-
voltage circuits and equipment while the high-voltage circuits are
disconnected. This maintains the existing level of protection because
the interlock disconnects provide an additional safeguard against
inadvertent exposure to energized high-voltage circuits.
One commenter noted that the proposed rule calls for deenergizing
the incoming high-voltage circuit if the normal/test auxiliary switch
is not in the normal position while closing the main circuit-
interrupting device and the disconnect device (isolator switch). This
commenter stated that this requirement would necessitate a retrofit in
existing longwall controllers since the normal/test switch must be in
the normal position when the disconnect switch is closed in order for
the control circuit to function at all. This would prohibit the closing
of the circuit-interrupting device and would disable the control
circuitry. With the disconnect device in the open/grounded position,
the test circuitry cannot be used unless the normal/test switch is in
the test position. The commenter further indicated that, in either
case, the incoming high voltage does not present a hazard.
Other commenters recommended that the control circuits within each
high-voltage motor-starter enclosure be interlocked with the disconnect
device, except for the controller on a shearer, so that the control
circuit can be powered with an auxiliary test switch when the
disconnect device is in the open and grounded position; and the
disconnect device cannot be closed without de-energizing the incoming
high-voltage circuit unless the auxiliary test switch is in the normal
operating position. These commenters stated that, in many cases, it is
necessary to close the main circuit-interrupting device with the
auxiliary switch in the test position.
MSHA has carefully reviewed and considered these comments. The
final rule retains the requirement that the control circuit for high-
voltage motor-starters can only be energized through an auxiliary test
switch when the disconnect switch is open and the load power conductors
of the high-voltage circuit are grounded. The proposed requirement that
neither the main circuit-interrupting device nor the disconnect device
can be closed without deenergizing the incoming high-voltage circuit
unless the auxiliary test switch is in the normal operating position,
has been replaced with a requirement which more clearly states the
expected performance of the control interlock circuit. The final rule
requires high-voltage control circuits to be interlocked so they can be
energized only when the disconnect switch is either in the ``closed''
or the ``open and grounded'' positions. High-voltage control circuits
may not be operated in any other intermediate positions of the
disconnect switch or auxiliary switch. This requirement will prevent
unintentional energization of high-voltage components. The control
circuit can be energized only when the disconnect switch is ``open and
grounded'' with the auxiliary switch in the ``test'' position, or when
it is closed with the auxiliary switch in the ``normal'' position. MSHA
has not included language in this paragraph to specifically exclude the
controller on a shearer from these interlock requirements, as suggested
by some commenters. Shearers are not required to be equipped with a
disconnect device as stated in Sec. 18.53(f) of this final rule and
MSHA does not intend that this provision be applicable to shearers.
Therefore, except for the above stated clarifications, the final rule
remains as proposed.
Paragraph (h) of the final rule requires that the electrical
protection be set at an appropriate value to provide protection for the
size and length of the longwall motor and shearer cable used, based on
an ``available fault current'' study that must be submitted to MSHA.
Proper electrical protection is essential in preventing a fire,
explosion or shock hazard resulting from inadequate sizing of
electrical cables.
Appendix I of existing 30 CFR part 18 includes maximum trailing
cable protective device settings and trailing cable length restrictions
as specified in Table 8 and in Table 9. These have, in the past, been
used as guidance in evaluating cables on longwalls rated at less than
1,000 volts. Under this final rule and consistent with agency policy,
the length restrictions and device settings do not apply to high-
voltage longwall motor and shearer cables. The procedures used in
evaluating high-voltage longwalls cables and settings include a review
of the applicant's fault-current study to determine the minimum
expected short-circuit currents available at the farthest projected
installation in the electrical system.
[[Page 10977]]
This paragraph of the final rule has been clarified, in response to
a proposed 1989 electrical rule comment, to indicate that trailing
cables would also be included in the required evaluation to ensure
adequate protection for the length and conductor size of all cables,
including longwall motor, shearer and trailing cables. However, MSHA
does not intend to specify a fixed maximum setting for short-circuit
protective devices, as noted by the commenter. MSHA intends to be
flexible by assessing each installation individually. The submitted
fault study is the basis in determining the settings, and for
permitting higher trailing cable circuit protective device settings and
cable lengths than specified by 30 CFR part 18. MSHA recognizes that it
is practical to design longwall systems with higher circuit protective
device settings and longer cable lengths in order to lessen economic
burdens on the mining community while preserving safety and health
protections for miners. Some commenters noted that the fault study is
unique to each mine and that this requirement should not be included in
30 CFR part 18. They suggested that the regulation is more suitable for
inclusion in part 75. MSHA disagrees. In order for a longwall mining
system to be safely designed, the designer must know the parameters
under which the longwall will be operated. These parameters would
include available fault currents. The final rule requires that this
information be provided to MSHA to determine whether cables are
adequately protected. Historically, longwalls are custom-made systems
and are not designed for more than one mining company. The fault study
should take into account worst-case projections (i.e., longest cable
lengths, smallest Kilo-Volt Amperes (KVA) Power Center). Enforcement
personnel will also use this information to ensure compliance with
Sec. 75.518-1--Electric equipment and circuits; overload and short
circuit protection; minimum requirements. Except as clarified above,
the final rule remains as proposed.
Paragraph (i) of the final rule requires all longwall motor and
shearer cables with nominal voltages greater than 660 volts to have a
cable construction with a grounded metallic shield around each power
conductor. This regulation requires the incorporation of the grounded
shield around each power conductor providing additional personnel
protection against shock and electrocution hazards. This is necessary
because any cable faults would cause phase-to-ground short-circuit
currents to flow. An extra level of protection is achieved because the
phase-to-ground short-circuit currents, unlike the phase-to-phase
short-circuit currents that may flow from faults in other cable
constructions, are limited in magnitude by the grounding circuit
components.
Some commenters suggested that these cables should be assembled
with a grounded shield around each power conductor but that the shield
should not be specified as metallic since these power systems restrict
ground-fault current to reduced values and the cables are constantly
flexed. They believed that an improved cable could be developed with a
nonmetallic shielding material around each power conductor. In response
to this comment, MSHA believes that this technology has not been
demonstrated or shown to provide equivalent safety in underground coal
mines. Although MSHA supports the application of new technology,
questions such as splicing reliability would need to be addressed
before incorporating these types of cables on longwalls. If a reliable
system using this type of cable were developed and equivalent safety
were demonstrated, it could be addressed under existing
Secs. 18.20(b)--Quality of material, workmanship, and design and/or
18.47(d)(6)--Voltage limitation through the construction and design
requirements for MSHA approval. The final rule has not been modified,
as suggested by commenters, and remains as proposed.
Paragraph (j) of the final rule specifies that high-voltage motor
and shearer circuits be provided with instantaneous ground-fault
protection set at not more than 0.125-amperes. The current transformers
(CT) used for ground-fault protection are required to be of the single
window-type and installed to encircle all three phase conductors. This
will provide highly sensitive and responsive ground-fault detection
systems, using new technology such as solid state relays, for high-
voltage circuits supplying electric face equipment. The protective
devices are required to operate instantaneously when exposed to ground
faults that exceed the trip setting of the ground-fault protective
device. Therefore, compliance with this standard will greatly reduce
the likelihood of fires and shock hazards that result from ground
faults on the high-voltage circuits or equipment.
The use of the single window-type current transformer encircling
all three phase conductors is the most reliable method for detection of
ground faults in mine power systems. This type of relaying (zero-
sequence) is not affected by CT error and gives very sensitive
tripping. This scheme is widely used in mining at all voltages.
Requiring all three phase conductors to be encircled by the CT
prohibits the equipment safety grounding conductors from passing
through or being connected in series with the CT. If the safety
grounding conductor passes through or is connected in series with the
CT, it is possible for the fault currents to flow through parallel
paths, thereby reducing the reliability of the ground fault protection.
Some commenters suggested that if the full-load current of the
circuit exceeds 200 amperes, the instantaneous ground-fault protection
be set at not more than 0.200-amperes. They stated that it is very
difficult to produce ground-fault current transformers that can
reliably discriminate between small ground-fault currents and larger
motor starting currents and that when the full-load current of a
circuit exceeds 200 amperes, it is reasonable to expect motor starting
currents in excess of 2,000 amperes. They asserted that a small
increase in the setting of the ground-fault protection is justified for
certain high-current circuits and that the suggested 0.200-ampere
setting would still be less than 40 percent of the maximum ground-fault
current. They noted that the specification of the current transformers
is very rigid and stated that the regulation should allow for new
technology if it can provide equal or improved protection. In relation
to ground-fault protection, a commenter focused on MSHA's statement
that zero sequence type relaying ``is not affected by CT error.'' The
commenters stated that, in their experience, erroneous signals are
produced in the CT's if the current levels are sufficiently high. They
noted that when starting currents flowing in the power circuit are in
excess of 2000A it is possible that an ``error current'' exceeding
100mA may be fed to the relay, causing nuisance tripping. For this
reason, it is their belief that the relays on the power center output
cables to the longwall controls are now set to a higher current of 200-
300mA and these cables carry the combined starting currents of two or
three motors. They concluded that as a result, when the size of
individual motors gets larger, this problem will be experienced on
motor cables.
MSHA has reviewed these issues and determined that reliable,
sensitive ground-fault protective devices are commercially available
and that they have been successfully used to correct the problems
described by the commenters. These devices can safely and reliably
operate at 0.125-ampere or
[[Page 10978]]
less. The use of a single window-type current transformer to encircle
only the three phase conductors assures that sensitive ground-fault
devices will detect all ground faults exceeding the setting of the
device. Detection devices inserted in the ground wire may not detect
all ground-fault currents and could compromise the integrity of the
ground circuit. Therefore, the final rule has not been modified and
remains as proposed.
Paragraph (k) of the final rule, like the proposed rule, requires
safeguards against corona to be provided on all 4,160 volt circuits in
explosion-proof enclosures. Corona is a luminous discharge that occurs
around electrical conductors that are subject to high electrical
stress. One danger inherent with high-voltage equipment is that
excessive electrical stress can cause premature breakdown of insulating
materials, which could result in arcing, thus creating an explosion
hazard in the presence of corona. Corona usually doesn't present a
hazard until voltage of 8kV are reached. However, even at 4,160 volts,
safeguards should be taken. This would include using cables with a
corona resistant insulation such as ethylene propylene, to avoid small
nicks or cuts in the cable insulation and to minimize high-voltage
transients. This provision is not intended to require stress cones or
similar termination schemes. There were no comments on this paragraph.
The final rule has not been modified and remains as proposed.
Paragraph (l) of the final rule, like the proposed rule, requires
limiting the maximum explosion pressure rise within an enclosure to
0.83 times the design pressure for any explosion-proof enclosure
containing high-voltage switchgear. This requirement protects against
explosion hazards that may arise from the effects of a sustained high-
voltage arcing fault. This arcing fault may significantly contribute to
the pressure rise created in an explosion-proof enclosure during an
internal methane-air explosion. Research conducted by the former U.S.
Bureau of Mines and MSHA on effects of high-voltage arcing in
explosion-proof enclosures concluded that this potential increased
pressure rise can be safely addressed through a combination of
designing the enclosure for the increased pressure and providing
electrical protective devices set to deenergize the incoming circuit
before the pressure rise becomes excessive. This provision requires
that the maximum explosion pressure rise must be limited to a value
that can be safely contained within the explosion-proof enclosure (83
percent of the design pressure). The final rule's performance-oriented
language permits compliance through any achievable means. Protective
methods used in previously issued approvals and experimental permits
consisted of electrical devices with rapid clearing times. However, the
rule provides for flexibility and permits alternative methods that may
provide equal protection, such as pressure switches or special pressure
release devices. There were no comments on this paragraph. The final
rule remains as proposed.
Paragraph (m) of the final rule, like the proposed rule, requires
that high-voltage electrical components located in high-voltage
explosion-proof enclosures cannot be coplanar with a single-plane
flame-arresting path. This protective measure will further prevent the
heat or flame from an arc or methane explosion in an explosion-proof
enclosure from igniting a methane-air mixture surrounding the
enclosure. This requirement addresses the possibility of conductor
material particles being expelled from the enclosure through the flame-
arresting path. Particles of molten material are emitted from the
conductors whenever a short-circuit occurs. Expulsion of these
particles from the enclosure can occur if their source is in the same
plane as the flame-arresting path and a pressure rise coincides with
the short circuit. Once these particles are expelled from the
explosion-proof enclosure, they can ignite an explosive atmosphere
should one be present. This possibility does not arise with multi-plane
flame-arresting path surfaces because a deflection in the path would
prevent ignitions by expelled particles. There were no comments on this
paragraph. The final rule remains as proposed.
Paragraph (n) of the final rule, like the proposed rule, addresses
MSHA's concern with the decomposition of insulating materials due to
tracking. In the presence of surface contaminants, small levels of
current can flow between conductors. As the currents flow, the
insulation may carbonize and produce conducting tracks. The conducting
tracks may grow progressively across the surface eventually bridging
between conductors and causing complete breakdown. Using insulation
with an adequate Comparative Tracking Index (CTI) rating can prevent
tracking, thus minimizing potential arcing that could lead to an
explosion hazard. Paragraph (n) requires that rigid insulation between
high-voltage terminals or between high-voltage terminals and ground be
designed with creepage distances in accordance with the table labeled
``Minimum Creepage Distances'' included in this section. The required
creepage distances are determined based upon the phase-to-phase use
voltage and the CTI of the insulation to be used. Creepage distance is
based in part on the CTI of the electrical insulating material. An
appropriate method of determining the CTI of the electrical insulating
material is described in the American Society for Testing and Materials
Standard, ASTM D3638 ``Standard Test Method For Comparative Tracking
Index of Electrical Insulating Materials.'' The MSHA derived creepage
distances in the table are consistent with most commercially available
high-voltage components to which this provision applies. There were no
comments on this paragraph. The final rule remains as proposed.
Paragraph (o) of the final rule addresses a requirement for Minimum
Free Distance (MFD) within an explosion-proof motor-starter enclosure.
MSHA's Internal Engineering Report Number 87021701 (available in the
rulemaking record) determined that if phase-to-phase arcing occurred,
there may be adequate arc energy to heat the walls of the enclosure
beyond the safe working temperature. This could cause failure of the
enclosure and create an explosion hazard. Distances between the wall or
cover of an enclosure and uninsulated electrical conductors inside the
enclosure were established to prevent wall or cover damage from phase-
to-phase arcing.
Some commenters suggested that the last sentence of the proposed
paragraph (o) be revised as follows: ``If a grounded \1/4\-inch thick
steel shield is installed between the area of potential arcing and the
adjacent wall/cover area, the minimum free distance requirement is
satisfied.'' MSHA believes that this comment was based on a footnote
present in the part 18 approval criteria established by MSHA for high-
voltage equipment containing on-board switching of high-voltage
circuitry. This criteria indicates that the specified MFDs may be
reduced if a \1/4\" thick steel shield is used between the area of
potential arcing and the adjacent wall/cover area. Since this footnote
did not cite a MFD or qualify the circumstances under which this shield
could be used, MSHA did clarify this criteria exception in the proposed
rule, and the final rule remains unchanged with respect to this
clarification. A commenter also stated that a steel shield could be
mounted in conjunction with an aluminum wall or cover to reduce the
required minimum free distance and that the thickness of this steel
shield would be used to determine the required minimum free
[[Page 10979]]
distance. MSHA has determined that a \1/4\" thick steel shield, mounted
to maintain a minimum electrical clearance, as suggested by the
commenter, would not provide sufficient protection if a phase-to-phase
arc occurred. The final rule also permits the use of steel shields
greater than \1/4\" thick to provide for flexibility and
diversification in enclosure design.
Some commenters noted that the proposed regulation classified all
enclosures in one of two groups: those with short-circuit currents less
than 10,000 amperes and those with short-circuit currents between
10,000 and 20,000 amperes. It was their view that because of the
substantial increase in minimum free distance between these groups,
MSHA should permit a manufacturer to calculate the appropriate MFD when
the short circuit current is between 10,000 amperes and 20,000 amperes.
They also recommended that MSHA include a provision that would permit
the minimum free distances to be revised based on future research in
this area. Finally, they noted that the MFD for a 1-inch thick cover
under Column A was omitted.
In response to these comments, MSHA has revised the Minimum Free
Distance Table by adding minimum free distance information for short-
circuit currents of 15,000 amperes. Additionally under the final rule
in paragraph (o)(1), MSHA allows for values not presented in the table
provided that they meet the specific engineering formulas on which the
table is based. These formulas were developed by MSHA engineers with
standard engineering calculations using data obtained from high-energy
arc testing. This testing was performed during Foster-Miller research,
under USBM Contract No. H0308093. The MSHA research reports and data
are part of the rulemaking record and are available for review.
Equipment approved under these circumstances will be limited to
equipment used only with power systems that do not generate short-
circuit currents that exceed the design parameters used for
establishing minimum free distance. In addition, MSHA will consider the
use of shields constructed with alternate materials and the use of
alternate techniques and methods that preclude the possibility of high-
energy arcs heating the walls of explosion-proof enclosures beyond safe
working temperatures. If upon evaluation, equivalent safety is
demonstrated, MSHA will address these technological advances and the
results of additional research in this area, if warranted, under
Secs. 18.20(b) and/or 18.47(d)(6). MSHA intentionally omitted the MFD
value for a 1" thick steel wall/cover under Column A to minimize
confusion. MSHA calculated this value to be 0.3", which is less than
the minimum electrical clearance that must be maintained under
Sec. 18.24 for high-voltage equipment. As indicated above, the proposed
rule has been modified in part, and adopted in part.
Paragraph (p) of the final rule, like the proposed rule, requires a
static pressure test to be performed on each prototype design of
explosion-proof enclosure housing high-voltage switchgear prior to
explosion tests. The manufacturer is also required to use this test as
a routine test on every explosion-proof enclosure housing high-voltage
switchgear, at the time of manufacture, or follow an MSHA accepted
quality assurance procedure covering the inspection of the enclosure.
These quality assurance procedures must include a detailed check of
parts against the drawings to determine: (1) That the parts and the
drawings coincide and (2) that the minimum requirements stated in 30
CFR part 18 have been followed with respect to materials, dimensions,
configuration and workmanship.
MSHA is concerned about the specified design pressure of an
enclosure. Presently, an enclosure that is designed for 150 pounds per
square inch gauge (PSIG) is tested with a methane explosion. Normally,
these pressures do not exceed 100 pounds per square inch (PSI). Since
the protective method to prevent over-pressurization in these
enclosures would be directly related to the design pressure, MSHA has
developed the static pressure test with its acceptable performance
criteria to ensure each enclosure design would be capable of
withstanding its design pressure. By requiring static pressure testing
on each enclosure prototype, MSHA believes that the adequacy of
enclosure design would be verified. Additionally, to require either
subsequent static pressure testing on each enclosure manufactured or an
acceptable quality assurance program guarantees the integrity of later
manufactured units.
The static test procedure specifies that the enclosure be
internally pressurized to a pressure no less than the design pressure,
with the pressure maintained for a minimum of 10 seconds. Following the
pressure hold, the pressure is removed and the pressurizing agent
removed from the enclosure.
Acceptable performance criteria are provided in this final rule.
Acceptable performance is achieved if the enclosure, during
pressurization, does not exhibit leakage through welds or casting or
rupture of any part that affects the explosion-proof integrity of the
enclosure. Further, the enclosure, following removal of the
pressurizing agents, must not exhibit visible cracks in welds,
permanent deformation exceeding 0.040 inches per linear foot, or
excessive clearances along flame-arresting paths following retightening
of fastenings, as necessary. Any of the above conditions would
constitute unacceptable performance.
There were no comments on this paragraph. However, the final rule
is modified to clearly state the type and nature of quality assurance
inspections that qualify as an MSHA accepted quality assurance
procedure.
Part 75 Mandatory Safety Standards--Underground Coal Mines
The final rule revises existing standard Sec. 75.1002--Location of
trolley wires, trolley feeder wires, high-voltage cables and
transformers, and adds Secs. 75.813 through 75.822 to set out
additional safety precautions that allow the use of available
technology. These new safety precautions address the use of high-
voltage longwall equipment in face (production) areas. As stated
earlier, MSHA previously included these safety precautions in petitions
granted for Sec. 75.1002. Based on its experience with petitions for
modification, the agency expects the final rule to improve safety for
underground coal mining.
Under the final rule, the risk of injury related to lifting and
handling of cables should be reduced since the use of high-voltage
cables can reduce the weight and size of a cable used in longwall face
systems.
The final rule also provides the following protection against fire,
explosions, and/or shock hazards:
(1) Improved short-circuit and ground fault protection;
(2) A means to easily test the effectiveness of ground fault
protection;
(3) Use of manufactured cable support systems for cables extending
from the power center to the headgate;
(4) Use of insulated cable-handling equipment;
(5) Use of protective gloves to troubleshoot and test low- and
medium-voltage circuits associated with high-voltage circuits;
(6) Use of additional protection for cables at points where cables
leave support systems;
(7) Use of more improved ``quick handle'' disconnect devices for
the purpose of performing work; and
(8) The use of barriers and interlock switches to help guard
against contact
[[Page 10980]]
with energized circuits. The final rule requires the use of cables
containing metallic shielding (SHD) around each power conductor.
Many of these final rule safety improvements are required
conditions for granted modifications of Sec. 75.1002. However the final
rule, like the proposed rule, provides two additional requirements.
These are gloves for troubleshooting and testing, and test circuits for
ground-fault protection.
The final rule, in response to commenters' suggestions, also
provides two provisions not included in the proposed rule,
Secs. 75.814(e) and 75.822. Section 75.814(e) requires a single circuit
interrupting device for cables connected in parallel or permits
parallel circuits-interrupting devices to protect parallel cables when
the parallel circuit-interrupting devices are electrically and
mechanically interlocked. Section 75.822 allows the use of No. 16 AWG
ground-monitor conductors. These additional provisions are a logical
outgrowth of the proposed rule and notice and comment process,
reflecting the primary purpose of the proposed rule by allowing the use
of high voltage on longwalls in a safe and efficient manner. The new
provisions are in response to specific joint industry and labor
comments received about parallel circuit use, and industry comments
about the size of ground-check conductors. These additional provisions
permit the use of high-voltage longwall systems that are safe,
effective and efficient and reflect the mining community's experience
with granted modifications. The ground-monitor conductor size and the
multiple parallel circuit provisions are not requirements but are
offered to give flexibility to mine operators to use available
technology and to minimize cost burdens where feasible.
Section 75.814(e) of the final rule requires that multiple
(parallel) circuits be protected by a single circuit-interrupting
device rather than parallel connected circuit-interrupting devices,
except when parallel devices are mechanically and electrically
interlocked. This requirement is based on MSHA electrical safety
experience, and experience in granting high-voltage longwall petitions
for modification, and is consistent with requirements under nationally
recognized consensus standards. Although multiple parallel circuits are
not necessary for safe high-voltage longwall systems, they do present
certain safety and cost efficiency advantages to some longwall high-
voltage systems as demonstrated under MSHA's and the mining industry's
petition experience. Higher currents can be used without increasing
voltage levels which helps minimize cable over-heating and reduces
cable insulation deterioration. Multiple parallel circuits in these
systems are a logical option that resulted from this high-voltage
longwall petition experience. As noted above, industry and labor
suggested multiple parallel circuit use during the rulemaking comment
process.
Section 75.822 allows the use of high-voltage longwall cables with
a minimum No. 16 AWG center ground-monitor conductor. This provision
eliminates the need for petitions for modification of Sec. 75.804(a).
It allows the use of improved high-voltage cable designs that provide
increased protection against fire and shock hazards. It reduces inter-
machine arcing from induced currents which can result in an ignition
hazard. The cable designs were initially developed for high-voltage
longwall equipment under previously granted petitions.
The cable design requirements were also requested by labor and
industry during the comment period of the proposed rule. Since 1992,
under MSHA-approved petitions, these cable designs have been safely
used.
These new requirements not only permit multiple parallel cable use
and the use of No. 16 AWG ground-monitor conductors but also minimize
industry paperwork requirements. With this new technology, the final
rule results in improved safety and savings for both the mining
community and MSHA. Cable replacement and maintenance costs will be
reduced. Also, mine operators will not need to file petitions for
modification; therefore, costs associated with the petition process
will be eliminated. Legal costs are incurred by all segments of the
mining community in the administrative review process associated with
petitions. Agency costs associated with publication, processing,
investigation and review of high-voltage longwall petitions will also
be eliminated.
The final rule increases safety protections and does not reduce the
protections currently afforded miners.
Section 75.2 Definitions
The definitions in this section are key to proper interpretation of
the electrical standards. Upon review, the Agency concluded that these
definitions should also be used to describe these terms wherever they
appear in 30 CFR part 75 and proposed such an approach. This approach
will provide clarity and consistency in the use of these terms where
they appear in all underground safety standards. All underground coal
mine operators and miners representatives were sent copies of these
proposed definitions as part of the complete longwall high-voltage
proposed rule. There were no comments opposing this approach.
The definitions are derived from consensus standards, including the
Institute of Electronic and Electrical Engineers, The New Standards
Dictionary of Electrical and Electronics Terms--Standard 100-1992, and
the National Electrical Code (NEC). Definitions found in 30 CFR part 18
of MSHA's regulations were also used as a source for this final rule.
In some instances, definitions taken from these sources were changed to
apply to electric circuits and equipment used in the coal mining
industry.
MSHA proposed that the term ``adequate interrupting capacity'' be
defined as the ability of an electrical protective device to safely
interrupt all values of current which can occur at its location in
excess of its trip setting or melting point. A commenter suggested that
this term be defined as the ability of an electrical protective device,
based upon its required and intended application, to safely interrupt
values of current in excess of its trip setting or melting point. MSHA
agrees and has changed the proposed definition to reflect this
suggestion. This commenter suggested that the proposed definition would
cause a problem, since in motor-starter enclosures of the type
presently used for high-voltage longwalls, short-circuit protection is
provided by a single circuit breaker common to all motor circuits,
whereas overload, ground fault, and ground-monitor protection trips
individual motor contactors. According to this commenter, this could
result in the interruption of the intended protected circuits at a
higher current value than was intended or required for that circuit,
therefore, affording less protection against overheating, shock and
fire hazards. The commenter further suggested that in applying the
revised definition, the short-circuit relay signals the circuit breaker
to interrupt the short-circuit current, whereas the ground-fault relay
signals the contactor to interrupt the restricted ground-fault current.
Under the final rule, adequate interrupting capacity is determined by
comparing the interrupting rating of the device with the actual
characteristics of the circuit to be protected. Thus, interruption of
the circuit occurs at the current rating required or intended for that
circuit rather than all values of current which can occur at its
location.
The final rule defines ``approval documentation'' to mean formal
papers issued by the Mine Safety and Health Administration which
illustrate and
[[Page 10981]]
describe the complete assembly of electrical machinery or accessories
that have complied with the applicable approval requirements of 30 CFR
part 18. The rule retains the meaning of the proposed rule but, for
clarification purposes, replaces ``formal document'' with the words
``formal papers'' and the verb ``document'' with the words ``describe
and illustrate''. The proposed language was also changed to accurately
reflect that ``approval documentation'' refers to those papers that
illustrate and describe equipment meeting the ``applicable requirements
of 30 CFR part 18.'' This change clarifies that approval documentation
must be submitted under part 18. MSHA received no comments in regard to
this definition.
Like the proposed rule, the final rule defines ``circuit-
interrupting device'' as a device designed to open and close a circuit
by nonautomatic means and to open the circuit automatically at a
predetermined overcurrent value without damage to the device when
operated within its rating. The Agency received no comments on this
definition and it is unchanged from the proposed rule. This definition
clarifies that circuit-interrupting devices be designed for manual
closure rather than automatic, to protect against safety hazards which
could result in severe bodily injury and death if unexpected automatic
energization of equipment were to occur. Conversely, the device must be
capable of opening the circuit automatically upon the occurrence of an
electrical fault. The rating of the device must be at a value that
would protect the device from damage during the automatic
deenergization of the circuit.
``Ground fault or grounded phase'' is defined to mean an
unintentional connection between an electric circuit and the grounding
system. MSHA received no comments on this definition and it remains
unchanged from the proposed rule.
Like the proposed rule, the final rule defines ``motor-starter
enclosure'' to mean an enclosure containing motor starting circuits and
equipment. This term describes equipment commonly used to house
longwall motor-starting equipment. No comments were received on this
definition and it remains unchanged.
Also like the proposed rule, the final rule defines ``nominal
voltage'' to mean the phase-to-phase or line-to-line root-mean-square
value assigned to a circuit or system to conveniently designate its
voltage class, such as 480 or 4,160 volts. The definition clarifies
that the actual operating voltage of a system or circuit may vary from
its nominal voltage within a range that permits satisfactory operation
of equipment. The Agency received no comments on this definition and it
has not been changed.
The final rule, like the proposed rule, defines ``short circuit''
to mean an abnormal connection of relatively low impedance, whether
made accidentally or intentionally, between two points of different
potential. There were no comments on this definition so it remains
unchanged.
Definitions of low voltage, medium voltage, and high voltage were
inadvertently included in the proposed rule. No comments were received
on these definitions. These terms are defined in existing rules and are
not addressed in this final rule.
One commenter suggested that ``cable handling and support system'',
a phrase used frequently in Sec. 75.817--Cable handling and support
systems, should be defined. Section 75.817 contains the performance
goals that cable handling and support systems must achieve, by
minimizing the possibility of miners coming into contact with cables
and protecting the high-voltage cables from damage. The Agency does not
believe that a definition is necessary for this term. Specifically
defining a cable handling and support system would limit operator
flexibility with respect to cable handling and support systems that may
be designed in the future and provide equal or greater safety
protection. Cable handling and support systems are understood by the
plain meaning of the words.
Section 75.813 High-Voltage Longwalls; Scope
Section 75.813 describes the scope of this final rule; it
identifies new Secs. 75.814 through 75.822 as electrical standards that
apply only to the use of high-voltage longwall circuits and equipment.
The final rule, unlike the proposed rule, expands the scope to include
new Sec. 75.822. As explained below, Sec. 75.822 is included in the
final rule in response to a comment regarding the size of ground-
monitor conductors in cables. This provision also eliminates the need
for petitions for modification related to ground-monitor conductor
size. This section also clarifies that all other existing standards in
30 CFR that are applicable to the use of high-voltage longwall circuits
and equipment continue to apply. For example, safety standards, such as
grounding and ground-monitor requirements contained in subparts H and I
of part 75 that are currently applicable to high-voltage installations
are also applicable to high-voltage longwall equipment.
Some commenters suggested that an exception should be made in the
standard for shearing machines that have been previously evaluated by
MSHA under part 18, using non-high-voltage criteria. However, such an
exemption would exclude shearing machines from the general safety
requirements contained in the final rule. Safety requirements
pertaining to electrical work, such as troubleshooting and testing, and
installation, examination and maintenance, contain provisions that
apply to all equipment on the high-voltage longwall, including shearing
machines. Other provisions relating to disconnect devices and cable
handling and support systems are applicable to the equipment they
address. Therefore, the Agency does not believe that a general
exemption for shearing machines would promote safety.
Section 75.814 Electrical Protection
This section of the final rule is derived in part from existing
Secs. 75.518-1--Electric equipment and circuits; overload and short
circuit protection; minimum requirements, 75.800--High-voltage
circuits; circuit breakers, and 75.800-2--Approved circuit schemes and
addresses electrical protection methods for longwall equipment supplied
by high-voltage systems. The effects of ground faults, electrical
arcing, heating of conductors, and short circuits can have adverse
consequences to the safety of miners. Effective electrical protection
for longwall equipment will reduce the potential for ignitions, fires,
and miner exposure to energized equipment frames. The final rule
incorporates the latest technology and provides increased worker
protection for high-voltage longwall mining equipment.
Paragraph (a) of the final rule addresses requirements for short-
circuit, overload, ground fault, and undervoltage protection for high-
voltage cables extending from the section power center, the shearer
motor cable(s), and the remaining motor cables. Short-circuit and
overload protection prevent damage to cables and motors due to
overheating. Ground-fault protection minimizes the risk of shock
injuries and ignition hazards to miners. Under-voltage protective
devices prevent automatic restarting of equipment following a loss of
power.
The final rule also requires circuit-interrupting devices for high-
voltage circuits that supply power to longwall equipment be properly
rated to safely interrupt the current to which it may be exposed
without damage. The adequacy of the circuit-interrupting device assures
that the device will remain undamaged by overcurrents and faults in the
system.
[[Page 10982]]
One commenter requested clarification regarding whether vacuum
contactors can be used to provide ground-fault and overload protection
since some have been approved for use on longwall controllers. Vacuum
contactors are a vacuum sealed system as opposed to a circuit breaker,
which interrupts the arc in air or oil. The final rule permits the use
of vacuum contactors as long as these contactors meet the definition of
a ``circuit-interrupting device.''
Some commenters submitted sketches of high-voltage longwall
circuits, and requested an evaluation of whether the circuits would
comply with the standard. It is beyond the scope of this rulemaking for
MSHA to evaluate and approve such submissions. Systems and wiring
designs can vary from mine to mine and from section to section within
the same mine, depending on factors such as control circuit
configuration, load terminations, and available fault current. MSHA
will evaluate these designs on a case-by-case basis as mine operators
plan to implement high-voltage longwalls at their mines and during the
approval process under the applicable 30 CFR part 18 provisions.
Paragraph (a)(1) of the final rule, like the proposed rule,
specifies a current setting for short-circuit protective devices. The
devices, whether located in the section power center or the longwall
motor-starter enclosure, are required to be set at the lower value of
either the setting specified in the approval documentation pertaining
to the longwall system, or 75 percent of the minimum available phase-
to-phase short-circuit current. The short-circuit current settings
specified during MSHA's approval process are based on the calculation
of fault currents at various key locations in the system.
The results of a 1992 Agency study of fault current levels in 30
high-voltage longwall systems indicate that phase-to-phase short-
circuit currents range between 1,500 and 9,000 amperes at the various
motor locations. (A copy of this study is available as part of the
record.) Therefore, current (ampere) settings of 75 percent of the
minimum phase-to-phase short-circuit currents will establish maximum
limits for trip settings of short-circuit current devices. As equipment
is used and moved from one location to another in a mine, changes take
place in both the equipment and electrical system that indicate a need
for a change in settings for short-circuit protective devices. Some
commenters suggested that a statement be added to this provision
indicating that the minimum available short-circuit current be
determined by calculations and not by actual in-mine short-circuit
tests.
To date, it has not been necessary to conduct in-mine testing for
the purpose of making determinations of proper settings of short-
circuit protective devices. However, the method used to make these
determinations should not be restricted to calculations, since unusual
or unanticipated conditions, such as high motor starting currents, may
require in-mine testing.
Paragraph (a)(2) of the final rule specifies short-circuit time
delay settings for protective devices. Short-circuit devices protecting
cables extending from section power centers to motor-starter enclosures
may incorporate time delays limited to the settings specified in the
approval documentation or 0.25-second, whichever is less. This
paragraph revises the proposed rule to allow short-circuit devices
protecting motor or shearer circuits to incorporate intentional time
delays. The time delays may be limited to the settings specified in the
approval documentation, or up to three cycles (0.050-seconds),
whichever is less. The purpose of permitting a time delay is to prevent
nuisance tripping during motor starting. When high-voltage longwall
equipment was introduced to the mining industry, nuisance tripping
problems were experienced. This nuisance tripping was caused by motor
starting currents. In order to solve these problems, it may be
necessary to incorporate time delays into the short-circuit protective
devices. Currently, electronic relays that have a time delay to
override motor starting currents are commonly used to provide short-
circuit protection for high-voltage longwall circuits.
The proposed rule allowed time delays for short-circuit devices
protecting cables extending from power centers to motor-starter
enclosures. The maximum value of the time delay was limited to the
smaller of the value specified in the approval documentation or 0.25-
second (15 cycles). However, the proposed rule did not provide for time
delays to be incorporated into short-circuit devices protecting motor
or shearer cables. The Agency specifically solicited comments regarding
elimination of intentional time delays and allowing higher short-
circuit settings based on system capacity.
One commenter stated that time delays between the longwall
controller and section power center should be required to permit
adequate coordination with downstream devices. According to the
commenter, if there is a failure in the utilization circuit, for
example, the crusher motor, it is advantageous for the failure to be
cleared by the circuit-interrupting device in the controller, not the
section power center which acts as a back-up. This commenter further
stated:
(1) Without the presently permitted time delays, the fault would
also deenergize the transformer, and more than likely, personnel would
reenergize the circuitry to find the location of the fault in the
system;
(2) This unnecessary closing in on a faulted circuit is eliminated
when the circuits are properly coordinated; and
(3) Time delays should be kept as short as possible to provide
adequate coordination.
Other commenters suggested that time delays be eliminated and
higher short-circuit settings be allowed based on system capacity,
provided that the Agency develops test scenarios to determine the safe
time delay settings. These commenters stated that elimination of time
delays would offer protection in the event of a direct fault because
there would not be resistor strips (overloads) available to open the
circuit and remove the power. They stated that inspections have
revealed that, in some cases, resistor strips are either not operable,
damaged, or have been by-passed.
After careful review of this issue, the Agency has concluded that
the use of time delays and subsequent lower short-circuit settings
would result in coordination (selective tripping) of circuit-
interrupting devices. Proper coordination of circuit-interrupting
devices can result in improved safety since faulted circuits can be
more easily and safely identified and isolated for the purpose of
troubleshooting, testing, and repair work. Commenters also suggested
that time delay settings of short-circuit protective devices used to
protect any cable extending from the section power center to a motor-
starter enclosure not exceed the settings specified in approval
documentation or 0.30-second (18-cycles), whichever is less.
This provision is not changed from the proposed rule. MSHA's
experience has been that the maximum time delay for reliable
coordination is 0.25-second (15-cycles). Further, a joint standard
published by the American National Standards Institute (ANSI) and the
Institute of Electrical and Electronics Engineers, Inc., entitled IEEE
Recommended Practice for Protection and Coordination of Industrial and
Commercial Power Systems (IEEE Buff Book)--Standard 242-1986, allows
0.25-second time-delay to ensure reliable coordination of short-circuit
protective devices. Therefore, an increase to 0.30-second is not
justified.
[[Page 10983]]
These commenters further suggested that short-circuit protective
device settings, used to protect motor and shearer circuits, should be
based on the maximum asymmetrical starting current with no intentional
time delay or be based on the maximum symmetrical starting current with
a time delay of no more than 0.050-second (three-cycles). These
commenters pointed out that modern electronic short-circuit protective
devices can be made to operate within one cycle (0.017-second). These
devices will respond while the motor or shearing machine starting
current contains an appreciable asymmetrical component and the
asymmetrical component of the motor or shearing machine starting
current will be negligible near 0.050-second. They suggested that
introducing a 0.050-second time delay will permit a significant
reduction in the setting of the short-circuit protective devices.
Another commenter suggested that it is important to recognize the
difference between asymmetrical motor starting currents that persist
for two (0.033-second) to three cycles (0.050-second) following
contactor closure, and motor starting currents that persist for several
seconds. This commenter pointed out a need for two cycles time delay.
MSHA agrees that there is a difference between asymmetrical motor
starting currents and symmetrical motor starting currents which can
last for several seconds.
Therefore, the final rule permits limited time delays to be used in
conjunction with lower settings of short-circuit protective devices
rather than higher settings of short-circuit protective devices without
time delays. This should result in proper coordination and subsequent
selective tripping of circuit-interrupting devices and prevent nuisance
tripping of circuit-interrupting devices due to high motor starting
currents. In response to comments, the Agency concludes that a time
delay will be necessary to allow proper starting of motors. Therefore,
this provision allows short-circuit devices protecting motor or shearer
circuits to incorporate intentional time delays limited to the settings
specified in the approval documentation, or up to three cycles (0.050-
seconds), whichever is less.
Paragraph (a)(3) of the final rule, like the proposed rule,
requires ground-fault currents to be limited by a neutral grounding
resistor to not more than 6.5 amperes when the nominal voltage of the
power circuit is 2,400 volts or less, or 3.75 amperes when the power
circuit voltage is greater than 2,400 volts. Typically, the mining
industry has used grounding resistors in resistance-grounded systems
that limit the ground-fault current in a circuit to 0.50 to 1.00
ampere. MSHA encourages this practice to continue. The levels specified
in the final rule allow new technology to detect lower ground-fault
currents and reduces shock hazards. During ground-fault conditions, the
grounding resistor will dissipate heat. The final rule limits the heat
dissipation by the grounding resistors to a value equivalent to the
heat dissipated by grounding resistors that have been in service for
numerous years on medium-voltage longwall systems. The specified values
prevent grounding resistor enclosures from overheating and becoming
ignition or fire sources. There were no comments on this provision and
therefore it remains as stated in the proposed rule.
Paragraph (a)(4)(i) of the final rule, like the proposed rule,
requires high-voltage circuits extending from the section power center
to have ground-fault protection set at not more than 40 percent of the
current rating of the neutral grounding resistor. These protective
devices assure that circuits extending from the section power source
will be quickly deenergized when they are subjected to ground faults.
The final rule uses the current ratings for grounding resistors,
specified in paragraph (a)(3), as a basis for setting ground-fault
devices. For example, if a 6.50 ampere grounding resistor is used, the
ground-fault device must operate to deenergize the circuit at 2.60
amperes (40 percent) or less. If a 0.50-ampere grounding resistor is
used, the ground-fault device must operate to deenergize the circuit at
200 milliamperes or less. The 40 percent trip level provides a safety
factor to assure that unexpected lower levels of ground-fault current
would be detected and cause the circuit-interrupting device to open.
This value also allows proper trip coordination with other protective
devices. There were no comments on this section of the rule and the
final rule adopts the language used in the proposed rule.
Paragraph (a)(4)(ii) of the final rule, like the proposed rule,
requires backup ground-fault protection to detect an open grounding
resistor. The ground-fault protective device can be a combination of a
potential transformer and voltage relay, or another device(s) capable
of detecting an open neutral resistor. Once an open neutral resistor is
detected, the ground-fault protective device must cause the circuits
extending from the power center to be deenergized. There were no
comments on this section of the rule and it remains as stated in the
proposed rule.
Paragraph (a)(4)(iii) of the final rule requires thermal protection
for the high-voltage neutral grounding resistor, which opens the
ground-check circuit for the high-voltage circuit supplying the section
power center, if the grounding resistor is subjected to a sustained
ground-fault current. The overtemperature rating or setting must be 50
percent of the maximum temperature rise of the grounding resistor or
150 deg.C (302 deg. F), whichever is less. The final rule is changed
from the proposed rule to also allow the use of a current transformer,
and a thermal overcurrent relay to provide the required thermal
protection. The final rule uses the term ``thermal protection'' rather
than ``overtemperature protection'' to permit current transformers and
thermal relays or other devices such as thermostats that react to
overtemperature. This change allows new technology developed by the
mining industry during the last seven years.
A commenter questioned the need for these devices. In response,
grounding resistors generate heat when subjected to sustained ground-
faults. An overtemperature device causes interruption of the high-
voltage circuit supplying the section power center by opening the
ground-wire monitor circuit before extreme heat destroys the grounding
resistor function. Failure of the resistor leaves the circuit
unprotected against ground-faults and increases the possibility of fire
and shock hazards. The commenter also requested a six-month delay in
implementing this provision to allow mine operators to acquire high
quality devices. It is MSHA's view that since these devices have been
required to be installed on high-voltage longwall mining systems for at
least the past seven years under petitions granted for Sec. 75.1002,
the devices should be readily available for use. A six month delay is
not necessary.
Another commenter wanted the maximum temperature for the
overtemperature device to be set at 150 deg. C. This setting was
incorporated into the 1992 proposed rule. Some commenters suggested
that overtemperature protection should remove power from the power
center transformer if the grounding resistor is subjected to a
sustained ground fault. These commenters pointed out the following:
(1) Many power centers are equipped with an incoming high-voltage
circuit breaker to provide protection for the transformer;
(2) The overtemperature protection for the grounding resistor could
cause this circuit breaker to open in the event of a sustained fault;
and
[[Page 10984]]
(3) This would remove the ground fault and make troubleshooting
more convenient.
MSHA agrees that the use of an incoming high-voltage circuit breaker
may be an acceptable device for removing power from the section power
center when the overtemperature device is activated. However,
activation of the grounding resistor overtemperature protection could
be an indication of serious problems in the tripping circuits for the
circuit-interrupting device(s) located in the power center. This
condition warrants complete removal of power from the entire power
center until the condition is properly investigated and corrected.
Another commenter stated that experience has shown that the
required protection may be best provided by using a current transformer
and thermal overcurrent relay rather than a thermostat. The commenter
also stated that this type of protection would not be dependent upon
control power and would still be able to deenergize the primary of the
transformer. MSHA agrees with this comment. The final rule is changed
to allow more flexibility in the use of thermal protection. It permits
the use of a current transformer and a thermal overcurrent relay to
provide required overtemperature protection.
Paragraph (a)(5) of the final rule, like the proposed rule,
requires high-voltage motor and shearer circuits to be provided with
instantaneous ground-fault protection set at not more than 0.125-
ampere. This provides highly sensitive and responsive ground-fault
detection systems, using existing technology, for high-voltage circuits
supplying electric face equipment. Protective devices are required to
operate instantaneously, greatly reducing the likelihood of fires and
shock hazards caused by ground faults. Some commenters suggested that
the instantaneous ground-fault protection be set at not more than
0.125-ampere if the full-load current of the circuit does not exceed
200 amperes and set at not more than 0.200-ampere if the full-load
current of the circuit exceeds 200 amperes. These commenters pointed
out that it is very difficult to produce ground-fault current
transformers that can reliably discriminate between small ground-fault
currents and larger motor starting currents. They further stated that,
when the full load current of a circuit exceeds 200 amperes, it is
reasonable to expect motor starting currents to exceed 2,000 amperes
and that a small increase in the setting of the ground-fault protection
is justified for certain high-current circuits. Finally, they stated
that a 0.200-ampere setting would still be less than 40 percent of the
maximum ground-fault current. Ground-fault devices are used to detect
low levels of fault currents during a grounded phase condition. These
sensitive devices can be influenced by extremely large values of motor
starting current.
MSHA has evaluated these comments and determined that there are
sensitive ground-fault protective devices commercially available that
have been successfully used to respond to the conditions described by
the commenters. These devices can safely and reliably operate at 0.125-
amperes or less even on systems having higher motor-starting currents.
A large number of existing high-voltage longwall systems use grounding
resistors that limit ground-fault currents to 0.500-amperes. Raising
the trip value of ground-fault devices protecting motor and shearer
cables to 0.200-amperes would also have the device set at 40 percent of
the current rating of the grounding resistor. This setting would be the
same value as protective devices used on cables extending from power
centers to motor-starter enclosures. Proper coordination of these
protective devices with upstream devices may not be achievable if the
trip setting is raised to 0.200-ampere. For this reason, the provision
is unchanged from the proposed rule.
Paragraph (a)(6) of the final rule, like the proposed rule, allows
time delay settings, not to exceed 0.25 second (15 cycles), of ground-
fault protective devices to provide coordination with the instantaneous
ground-fault protection of motor and shearer circuits. This provision
limits the time lapses between actuation of the section power center
ground-fault protective devices and those located in the motor-starter
enclosure. Time delay settings allow coordination and selective
tripping of circuit protective devices. This coordination and selective
tripping also assures that the entire circuit deenergizes quickly to
reduce exposure to shock hazards.
A commenter wanted a time delay of 0.1 second (6 cycles) for
ground-fault protection for high-voltage motors. The commenter
described situations where nuisance tripping occurred during starting
and stopping of the motor and a time delay of 0.1 second would solve
the problem. MSHA has evaluated this comment and has determined that
technology is available and currently used by industry to alleviate
this condition without changing the time delay. Most ground faults
occur between the motor-starter enclosure and the motors or shearers.
These ground faults must be removed as quickly as possible. Another
commenter wanted to add wording to define the total time for ground-
fault protection as 0.4 second (24 cycles) maximum for all devices.
Most longwall systems now utilize two ground-fault protective devices
with a time delay of 0.25 second (15 cycles) which provides adequate
time for selective tripping. Thus, the final rule is unchanged from the
proposed rule.
Paragraph (a)(7) of the final rule, like the proposed rule,
requires an undervoltage protection device that operates on loss of
voltage to cause and maintain the interruption of power to a circuit.
The rule reduces the likelihood that miners will be pinned or crushed
due to the automatic restarting of the equipment. A commenter suggested
another means of compliance by using a ``momentary start contactor with
a seal in circuit.'' In response, the rule, unchanged from the proposed
rule, is performance oriented and permits any undervoltage protection
provided by a device that operates on loss of voltage. Therefore, any
voltage sensing device, including the method specified by the
commenter, that would prevent the automatic reclosing of the circuit
protective device as specified in paragraph (a) will meet the
requirements of the final rule.
Paragraph (b) of the final rule, like the proposed rule, requires a
single window-type current transformer to encircle the three-phase
conductors for ground-fault protection. The equipment safety grounding
conductors are prohibited from being passed through or connected in
series with ground-fault current transformers. This configuration could
defeat ground-fault protection and result in hazardous voltage on
equipment frames. A single window-type current transformer must be used
to provide the ground-fault protection required by paragraph (a)(4)(i)
for circuits extending from the section power center to the motor-
starter enclosures. It also requires the same type current transformer
for ground-fault protection specified in paragraph (a)(5) for:
(1) High-voltage motor circuits extending from the motor-starter
enclosures;
(2) The shearer motor circuits extending from the section power
center; and
(3) Motor enclosures.
Some commenters suggested this provision should allow for
alternative components if they provide equivalent or improved
protection. MSHA, however, is unaware of any alternative device that
provides equivalent
[[Page 10985]]
protection and the commenter did not specify any equivalent devices.
The use of a single window-type current transformer to encircle only
the three phase conductors assures that sensitive ground-fault devices
will be able to detect all ground faults exceeding the setting of the
device. Detection devices inserted in the ground wire may not detect
all ground-fault currents and could compromise the integrity of the
ground circuit. Therefore, paragraph (b) of this section remains as
proposed.
Paragraph (c) of the final rule requires a ground-fault test
circuit for each ground-fault current device. This test circuit must
inject a current of 50 percent or less of the current rating of the
grounding resistor to verify that a ground-fault condition causes the
corresponding circuit-interrupting device to open. This testing
procedure helps determine if ground-fault current devices function at
required current levels. It will also test the sensitivity of each
device to ground-fault currents. The proposed rule required each
ground-fault current device to be provided with a test circuit that
would inject a current of 50 percent or less of the current rating of
the grounding resistor and cause each corresponding circuit-
interrupting device to open. Some commenters suggested that this
requirement be limited to ground-fault circuit devices required by
paragraphs (a)(4)(i) and (a)(5) of this section. These commenters also
suggested that the ground-fault test circuit inject a primary current
into the current transformer that does not subject the equipment to an
actual phase-to-ground fault. They pointed out that primary current
injection tests of the ground-fault devices are safe and effective
tests for those devices. They further stated that testing of the backup
ground-fault devices located across the grounding resistor, such as the
potential transformer and overtemperature relay, would require
application of an actual phase-to-ground fault and could be hazardous
to both personnel and equipment. MSHA agrees with the commenters that
this method of testing is considered to be safe and effective in
determining whether a device trips at its setting. In response to these
comments, the final rule modifies the proposed rule, to require each
ground-fault current device required by paragraphs (a)(4)(i) and (a)(5)
to have a test circuit that passes a primary current of 50 percent or
less of the maximum ground-fault current through the current
transformer and cause the corresponding circuit-interrupting device to
open.
Paragraph (d) of Sec. 75.814, like the proposed rule, prohibits the
use of circuit-interrupting devices that automatically reclose.
Automatic reclosure of the circuit-interrupting device allows immediate
reenergization of a circuit that has sustained a fault. Faults occur in
underground electrical systems as a result of damage from roof falls or
equipment insulation failure. Under such circumstances, the use of
automatic reclosing circuit-interrupting devices could create shock and
fire hazards when a short-circuit or ground-fault condition exists in
the circuit. There were no comments on this paragraph and it remains as
proposed.
The final rule includes an additional paragraph (e) that is
partially derived from Sec. 75.518-1--Electric equipment and circuits;
overload and short circuit protection; minimum requirements. This was
suggested by joint commenters from industry and labor to address
concerns regarding the use of cables in parallel. The commenters
suggested that when two or more cables are used to supply power to a
common connection point (bus), each cable be provided with ground-wire
monitoring so that all cables are deenergized when the grounding
conductor becomes severed or open. In support of this suggestion, the
commenters noted that when two or more cables are connected in
parallel, shock hazards will exist if one cable has been disconnected
and the other cable is left energized. MSHA agrees. The Agency has been
incorporating this additional requirement into petitions for
modification of Sec. 75.1002 during the last four years. The final rule
requirement that parallel power cables be installed with ground-wire
monitor systems addresses this concern. Ground-wire monitoring in power
cables has been an inherent part of the developing high-voltage
longwall technology over the last 16 years. In addition, under the
final rule, parallel circuits installed after the effective date of
this rule must be protected by a single circuit-interrupting device
rather than have circuit-interrupting devices operating in parallel
unless such devices are mechanically and electrically interlocked. This
is supported by the fact that 30 CFR Sec. 75.518-1 requires overcurrent
devices to conform to the provisions of the National Electric Code
which prohibits parallel connections of circuit-interrupting devices.
Section 75.815 Disconnect Devices
Section 75.815 of the final rule includes requirements pertaining
to disconnecting devices located in longwall power centers and in
longwall equipment motor controllers that provide a safe means of
disconnecting power during the performance of electrical work. It
includes design and performance requirements pertaining to electrical
ratings, lockout, grounding, and maintenance requirements pertaining to
compliance with part 18 of Title 30 CFR. This section was derived, in
part, from existing Secs. 75.511, 75.520, 75.601, 75.705, and 75.808.
Paragraph (a) as in the proposed rule, requires a disconnecting
device in addition to the circuit-interrupting device (required by
Sec. 75.814) in the power center that supplies power to longwall
equipment. This disconnecting device provides visual evidence that the
circuit is deenergized. Either a disconnecting switch or cable coupler
would suffice to satisfy this requirement. Disconnecting devices in
power centers facilitate the deenergization process prior to
performance of electrical work. Figures I-1 and I-2 in Appendix A
provide guidance for compliance with this requirement. The Agency did
not receive any comments on this provision and it is unchanged from the
proposed rule.
Paragraph (b) of the final rule, like the proposed rule,
establishes maintenance requirements for disconnecting devices in
motor-starter enclosures. Section 75.815(b) requires that disconnect
devices be maintained in accordance with the approval requirements of
paragraph (f) of Sec. 18.53--High-voltage longwall mining systems.
Section 18.53(f) requires that the load-side power conductors be
grounded when the disconnecting device is open. This provision guards
against the occurrence of electrical accidents by requiring the circuit
disconnect device to ground the disconnected circuit before work is
performed on the circuit. The final rule assures that a properly
maintained safe means of deenergizing longwall circuits and equipment
is readily available for use during routine operation or in the event
of an emergency. Additionally, the final rule provides for safe
deenergization of high-voltage circuits in the motor-starter enclosure,
or equipment supplied power through the enclosure during testing and
troubleshooting work. MSHA encourages mine operators to continue using
additional disconnecting devices that are already installed in many
existing longwall systems.
Paragraph (b) requires a caution label on the cover of each starter
enclosure compartment containing the main disconnecting device. This
caution label must warn miners against entering the compartment before
deenergizing the incoming high-voltage circuits to the
[[Page 10986]]
compartment. It warns miners that the line side of the disconnect
device may be energized when the device is opened and cautions them to
deenergize incoming power before removing any covers. It also helps to
assure that miners deenergize power to starter enclosures before
removing any of the covers. There were no comments received on this
provision so the final rule is unchanged from the proposed rule. MSHA
recognizes that the mining industry has taken safeguards by using
additional caution labels to warn miners of stored energy devices
(capacitors). We encourage the industry to continue the safety practice
of using caution statements that warn miners to ground the capacitors
before performing work on electric circuits.
Paragraph (c) of the final rule, like the proposed rule, requires
disconnecting devices to have voltage and current ratings compatible
with the circuits in which they are used. This requirement ensures safe
operation of these devices during normal use. The Agency received no
comments on this provision. It remains the same as the proposed rule.
Paragraph (d)(1) of the final rule, like the proposed rule,
requires that disconnecting devices be designed to provide visual
evidence that all ungrounded power conductors are disconnected when the
device is open. Visual evidence means the ability to observe the
physical separation of the control and power conductors without
removing any covers. There were no comments received on this provision
and no changes were made to the proposed rule.
Paragraph (d)(2) of the final rule, like the proposed rule,
requires that disconnecting devices be equipped to ground all power
conductors when the device is ``open''. This requirement allows the
circuit to be properly grounded before any work is performed on the
electric circuits or equipment. It also allows discharging of any
existing voltage due to capacitance between the power conductors and
ground. The Agency did not receive any comments on this provision. It
remains unchanged from the proposed rule.
Paragraph (d)(3) is unchanged from the proposed rule. It requires
each device be equipped to lock the device in the open position. This
ensures that the circuit being worked on remains deenergized until work
is completed. There were no comments received in response to this
provision.
Paragraph (e) of the final rule, like the proposed rule, requires
that disconnecting devices, except those installed in explosion-proof
enclosures, be capable of interrupting load currents without creating
hazardous conditions. If the device is not designed for full load
interruption, the device must be installed so that a circuit-
interrupting device will deenergize the incoming power circuit before
the disconnecting device opens. Use of improperly rated devices could
result in the destruction of the device and injuries to miners due to
flash burns or flying parts. The final rule further requires that
disconnecting devices installed in explosion-proof enclosures be
maintained in accordance with the approval requirements of
Sec. 18.53(f)(2)(iv) of part 18. This provision specifies that
disconnecting devices be designed and installed to cause the current to
be interrupted automatically prior to the opening of the contacts of
the device. The Agency did not receive any comments on this provision
so it remains the same as the proposed rule.
Some commenters suggested that a new paragraph (f) be added to
require that any additional disconnecting devices used to deenergize a
portion of the longwall equipment meet the requirements of paragraphs
(c), (d), and (e). They stated that it is often necessary to maintain
power on part of the longwall equipment in order to safely and
efficiently perform electrical work on another part of the equipment.
For example, they stated that a disconnecting device for the shearing
machine circuit will permit electrical work on a deenergized shearing
machine while maintaining power on the rest of the longwall. Under the
final rule, individual disconnecting devices, such as cable couplers,
may be used to isolate individual pieces of equipment for the purpose
of performing maintenance. The final rule requires that all additional
disconnecting devices satisfy the requirements of paragraphs c, d, and
e. Therefore, the Agency believes that an additional provision is not
necessary.
Section 75.816 Guarding of Cables
This rule is derived in part from existing Sec. 75.807--
Installation of high-voltage transmission cables and addresses guarding
of high-voltage cables supplying longwall equipment. Until this rule,
Sec. 75.807 related to high-voltage cables in areas not in by the last
open crosscut or not within 150 feet from the pillar workings. In
addition to the Sec. 75.807 requirements, Sec. 75.816 of this final
rule requires guarding of high-voltage cables where persons regularly
work or travel over or under the cables and where the cables leave
cable handling or support systems in the longwall face areas or are
within 150 feet of the pillar workings. As provided in Sec. 75.807,
cables installed six and one half feet or more above the mine floor
satisfy these requirements by location. Guarding minimizes the
possibility of miners inadvertently contacting the cables. Also, cable
guarding must consist of grounded metal or nonconductive flame-
resistant material. High-voltage cables used to supply longwall
equipment could present shock and fire hazards if the cables are
damaged or defective.
Paragraph (a)(1) of the final rule, like the proposed rule,
requires that cables be guarded where persons regularly work or travel
over or under the cables. This minimizes accidental contact with
cables. There were no comments received on this provision and it is
unchanged from the proposed rule.
Paragraph (a)(2) of the final rule, like the proposed rule,
requires guarding where the cables leave cable handling or support
systems to extend to electric components. This provision prevents
physical damage from stress and flexing that might cause shock and fire
hazards. The Agency did not receive any comments on this provision and
it remains the same as in the proposed rule.
Paragraph (b) of the final rule requires guarding of high-voltage
cables to minimize the possibility of inadvertent contact with cables
and to protect high-voltage cables from physical damage. Guarding must
be constructed of grounded metal or nonconductive flame-resistant
material. This standard provides minimum requirements for the physical
and electrical protective characteristics of the guarding. The proposed
rule required that guarding prevent miners from contacting high-voltage
cables.
One commenter suggested that the provision specifically permit the
use of either continuous guarding or overlapping sections of guarding.
According to this commenter, overlapping sections of guarding achieve
the safety goal of the provision and would reduce time-consuming and
expensive repairs that could involve thousands of feet of cable to
repair a small section. In response to this comment, the rule specifies
the locations where cables are required to be guarded. Under the rule,
the guarding material must cover the cables and continuous or
overlapping guarding may be used. When joining sections of metal
guarding, steps should be taken to assure proper grounding.
Other commenters suggested that this section require that guarding
``minimize'' rather than ``prevent'' the possibility of miners
contacting the cables. They stated that it is not
[[Page 10987]]
practical to design guarding that would prevent miners from contacting
the cables. This often occurs when miners are attempting to guide or
train cable into its holding trough when it is loose or falls out. They
suggested it is possible to design guarding that would ``minimize''
contact or ``block access'' to the cable. MSHA agrees with this
commenter and modified the proposed rule. In response to these
comments, this revised provision, requires a physical barrier
consisting of guarding material between the cables and miners to
minimize inadvertent contact with the cables, and requires mechanical
protection for the cables. Also, Sec. 75.818 of the final rule
prohibits intentional contact with cables except for the purpose of
training (guiding) motor and shearer cables with the use of proper
protective equipment.
Section 75.817 Cable Support Systems
This section of the rule addresses handling and support systems of
high-voltage cables suppling longwall equipment. Under the final rule,
longwall mining systems must be equipped with cable handling and
support systems that are constructed, installed, and maintained to
protect high-voltage cables from damage and to minimize the possibility
of miners inadvertently contacting the cables. Under the proposed rule,
these systems were required to prevent miners from contacting high-
voltage cables. High-voltage cables used to supply longwall equipment
can present shock and fire hazards if the cables become damaged or
defective. This section of the final rule provides the necessary
protection to cables and miners by minimizing exposure to damaged or
defective cables. This section is derived, in part, from existing
requirements in Sec. 75.807 and addresses new systems developed by the
mining industry to mechanically handle and support cables. These
systems are presently used on high-voltage longwall mining systems to
minimize damage to the cables.
One commenter suggested that a provision be added to this section
that allows the installation of guarded high-voltage cables in cable
handling and support systems where hydraulic hoses and low- and medium-
voltage cables are also installed. In response to this comment, high-
voltage longwall equipment and associated cables are currently required
by existing Sec. 18.36(b)--Cables between machine components to be
isolated from hydraulic lines. Also, existing Sec. 75.807 currently
requires that the high-voltage cables be placed in a manner to prevent
contact with other low-voltage circuits. Isolation and placement help
guard against fire and assures protection of electric cables, which
could be damaged, if hydraulic lines are ruptured or conductor
insulation fails. Based on MSHA experience, acceptable methods which
meet Sec. 18.36(b) requirements will be determined during the part 18
approval process. Guarding of cables by proper isolation and placement
is an acceptable method to meet this requirement.
Other commenters suggested that the wording of the rule be changed
to ``longwall mining equipment shall be provided with cable handling
and support systems that are constructed, installed, and maintained to
minimize the possibility of miners contacting the cables and to protect
the high-voltage cables from damage.'' We agree with the commenters as
stated in the previous discussion of Sec. 75.816. The final rule
requires that cable support systems minimize the possibility of
inadvertent contact instead of preventing contact.
Section 75.818 Use of Insulated Cable Handling Equipment
This section of the final rule addresses the types of personal
protective equipment that may be used when it is necessary to handle
high-voltage longwall cables, the examination for defects or damage
prior to use, and the intervals at which high-voltage protective
equipment must be tested. Its purpose is to provide protection against
electric shock hazards associated with the handling of energized high-
voltage longwall cables. This section is derived, in part, from
existing requirements in Secs. 75.705-6--Protective clothing; use and
inspection, 75.705-8--Protective equipment; testing and storage and
75.812--Movement of high-voltage power centers and portable
transformers; permit.
Paragraph (a) of the final rule, like the proposed rule, requires
that personal protective equipment be used when training or guiding, by
hand, a high-voltage longwall cable into the cable handling trough when
the cable inadvertently comes out. Commenters suggested that the list
of protective equipment be expanded to include facial protection and
protective clothing, and that the protective equipment also be capable
of providing protection from a cable explosion. They stated that
additional protection is needed for persons who handle high-voltage
longwall cables, since persons have been burned when power conductor
insulation deteriorates within the cable and the power conductors fault
or contact each other, causing the cable to explode. MSHA disagrees.
Shielded-type cables, required by existing regulations, provide the
necessary protection for miners by limiting or preventing electrical
arcing and flashover within the cable. This protection occurs as long
as the cables are used in conjunction with proper mechanical
protections required under Sec. 75.817, and with proper maintenance of
electrical protective devices required under Sec. 75.814. Therefore,
paragraph (a) of this final section remains as proposed.
Paragraph (b) of the final rule requires high-voltage insulated
gloves, sleeves, and other insulated personal protective equipment, to
have a Class 1 (7,500 maximum use volts) or higher rating that has been
established by a nationally recognized consensus standard. The
protective equipment must be: (1) Examined prior to each use for signs
of damage or defects; (2) destroyed or removed from the underground
area of the mine if found damaged or defective; and (3) electrically
tested every six months according to a nationally recognized consensus
standard. This provision protects against electrical shock hazards by
requiring personal protective equipment to be rated for a maximum use
voltage and examined before each use to determine if the equipment is
safe to use. Paragraph (b) of the proposed rule required all personal
protective equipment to be rated for 20,000 volts; examined before each
use for visible signs of damage; removed from the underground area of
the mine when damaged or defective; and electrically tested every six
months.
A commenter suggested that this paragraph be modified to allow
gloves to be rated for a minimum of 5,000 volts and tested every six
months as described in a nationally recognized consensus standard. The
Agency is not aware of any recognized consensus standards that rate
gloves, sleeves, and other personal protective equipment at 5,000
volts. The commenter also stated that damaged or defective gloves
should be permitted to be either removed from the underground area of
the mine or destroyed.
Another commenter stated that insulated personal protective
equipment should be electrically tested by the manufacturer in
accordance with ASTM standards and be rated for at least the maximum
nominal voltage of the circuit. The commenter also stated that personal
protective equipment should be examined before each use for visible
signs of damage or defects and be electrically tested at least every
six months or when there is any sign of excessive wear. This commenter
stated that the visible and electrical tests
[[Page 10988]]
should be conducted in accordance with American Society for Testing and
Materials (ASTM) standards.
In response to the commenters' concerns, we agree that safety would
be enhanced by adopting the ASTM standard. We have revised paragraph
(b) of the proposed rule. The final rule requires insulated protective
equipment, including high-voltage gloves and sleeves, to be rated a
Class 1 or higher (maximum use voltage of 7,500 volts). Paragraph
(b)(1) requires that this equipment be examined before each use for
visible signs of damage or defects. This section requires users of
protective equipment to examine it for hazardous conditions, including
excessive wear. For example, a method commonly used to detect damage in
insulating gloves is to test the rubber gloves by rolling the cuff
tightly toward the palm of the glove in such a manner that air is
entrapped inside the glove. Puncture detection may be enhanced by
listening for escaping air or by feeling escaping air against the face.
In response to commenters, the Agency has revised paragraph (b) in
the final rule to allow defective personal protective equipment to be
destroyed or removed from the mine. The Agency agrees with the
commenter that destroying this equipment when it becomes defective is
as effective as removing it from the underground mine.
MSHA also received comments suggesting that insulating protective
equipment be tested every six months in accordance with nationally
recognized standards. The Agency agrees with this commenter and has
revised paragraph (b) to require that all insulated handling equipment
for use with high-voltage longwall cables be electrically tested every
six months in accordance with a nationally recognized consensus
standard contained in the ASTM F496-97, ``Standard Specification for
In-Service Care of Insulating Gloves and Sleeves.'' The purpose of
these formal testing procedures for high-voltage cable handling
equipment is to provide necessary safety protections for miners and
ensure that unknown equipment defects will be detected before they are
a hazard to miners.
Section 75.819 Motor-Starter Enclosures; Barriers and Interlocks
Section 75.819 of the final rule, like the proposed rule, requires
separation by location, partitions, or barriers of low- and medium-
voltage circuits from high-voltage circuits in motor-starter enclosures
and requires cover interlock switches to be installed on the cover of
any motor-starter compartment containing high-voltage components. The
compartment separations and interlock switches must be maintained in
accordance with paragraphs (a) and (b) of Sec. 18.53--High-voltage
longwall mining systems. The purpose of Sec. 75.819 is to help guard
against miners coming in contact with energized internal components of
high-voltage electric equipment through proper maintenance of safety
devices that assure deenergization when any cover that provides access
to energized high-voltage components is removed. Compartment separation
also helps assure that persons are not exposed to adjacent energized
high-voltage components or circuits after gaining access to
compartments containing control, communication, or other low- and
medium-voltage circuits.
This provision provides automatic protection for miners who may
inadvertently remove a cover exposing energized high-voltage circuits
should the wrong circuit be disconnected. There were no comments
received on this section of the proposed rule and it remains as
proposed.
Section 75.820 Electrical Work; Troubleshooting and Testing
Section 75.820 is directed at protecting miners while they are
performing electrical work, including troubleshooting and testing, and
the removal of belt structure. This section is derived, in part, from
existing Secs. 75.509--Electric power circuit and electric equipment;
deenergization, 75.511--Low-, medium-, or high-voltage distribution
circuits and equipment; repair, and 75.705--Work on high-voltage lines;
deenergizing and grounding and addresses requirements for performing
work on all circuits and equipment associated with high-voltage
longwalls. This section applies to all low-, medium-, and high-voltage
circuits and equipment associated with high-voltage longwalls. The
requirements are similar to those in existing Secs. 75.509 and 75.511
for work on electric circuits and equipment generally, except with
additional requirements applicable to high-voltage longwall
installations. These requirements include personnel qualifications and
safe work procedures, including safety equipment when troubleshooting
and testing, and methods to guard against contact with energized high-
voltage cables during the installation and/or removal of belt
structure(s). The final rule for Sec. 75.820 is identical to the
proposed rule except for changes to Sec. 75.820(a), which is revised
based on a recent Federal Mine Safety and Health Review Commission
decision and Secs. 75.820(d)(3) and 75.820(f) which MSHA revised due to
comments. The revisions address: (1) The fact that persons qualified
under Sec. 75.153--Electrical work; qualified person must be able to
perform electrical work on all circuits and equipment; (2) The type of
gloves that must be worn by persons performing troubleshooting and
testing; and (3) The methods used to guard against contact with a high-
voltage cable during installation and/or removal of belt structure.
Paragraph (a) of the final rule requires that electrical work on
all circuits and equipment associated with high-voltage longwalls be
performed only by persons qualified, in accordance with Sec. 75.153, to
perform electrical work on all circuits and equipment, not just high-
voltage circuits and equipment. This change is consistent with the
recent Federal Mine Safety and Health Review Commission decision,
Secretary of Labor v. Black Mesa Pipeline, Inc. 22 FMSHRC 708, 715
(June 30, 2000). That decision concluded that Sec. 75.153 requires that
a ``person qualified'' be knowledgeable of high-, medium-, and low-
voltage circuits and equipment. Therefore, for clarification purposes,
the language of this final rule has been modified to conform with this
decision and the plain meaning of Sec. 75.153. This requires that a
person qualified to work on electrical circuits be knowledgeable of
low-, medium- and high-voltage circuits. The Agency currently requires
that qualification in all voltages be obtained before a person can
become qualified under Sec. 75.153. The requirement that persons
performing electrical work be qualified for all voltages assures that
persons performing work on low- and medium-voltage circuits are
qualified to identify hazards that may exist on high-voltage circuits
in close proximity of their work.
Some commenters suggested that paragraph (a) state that electrical
work on all high-voltage circuits and any enclosure containing high-
voltage components shall be performed only by persons qualified under
Sec. 75.153 to perform electrical work only on high-voltage circuits
and equipment. These commenters indicated that the proposed rule would
not permit persons qualified under Sec. 75.153 to perform electrical
work only on low- and/or medium-voltage circuits or equipment or
perform any electrical work on circuits or equipment associated with a
high-voltage longwall. The commenters further indicated that certain
subsystems of the longwall are completely isolated from high-voltage
circuits and equipment such as: lighting systems, communication
systems, shield
[[Page 10989]]
control systems, hydraulic pump control systems, battery chargers, air
compressors, and rock dusters. However, because many low- and medium-
voltage circuits associated with high-voltage longwalls are in close
proximity to the high-voltage circuits, MSHA believes it is important
that anyone performing electrical work on the high-voltage longwall be
knowledgeable about low-, medium- and high-voltage circuits. And, as
noted above, a person qualified under Sec. 75.153 must be knowledgeable
of all voltage circuits.
Since all the circuits cannot be totally isolated, it is important
that qualified persons working on the circuits of lower voltages be
aware of the hazards of high-voltage circuits. Another commenter
inquired as to what the high-voltage qualification requirements were
and suggested that MSHA ensure that appropriate training is defined and
required. MSHA's existing standard in Sec. 75.511--Low-, medium-, or
high-voltage distribution circuits and equipment; repair requires that
only persons qualified in low-, medium- and high-voltages perform high-
voltage work, and Sec. 75.153 sets forth the procedures for their
qualification. Additionally, existing Sec. 75.160--Training programs
requires an MSHA approved plan for retraining qualified persons.
Another commenter requested that wording be added to allow anyone to
perform high-voltage work under the supervision of a qualified person.
Due to the hazards previously described, only qualified electricians
perform high-voltage work. Therefore, except for the clarifications
noted above, paragraph (a) of this section remains as proposed.
Generally, paragraphs (b)(1) through (b)(4) of Sec. 75.820, like
the proposed rule, require safety precautions to be taken by qualified
electricians prior to performing electrical work. The qualified
electrician is responsible for assuring that the electrical circuit is
properly deenergized, that the contacts of the circuit disconnecting
device are open, and that the disconnecting device is locked out with a
padlock and tagged. These precautions assure that the affected circuit
has been properly deenergized and disconnected so that persons
performing work are not exposed to shock, electrocution, or burn
hazards. Without taking precautions, such as properly locking out and
tagging the affected circuit, qualified electricians would be exposed
to shock and electrocution risks if someone were to inadvertently
reenergize the circuit.
Paragraph (b)(1) of the final rule specifically requires that a
qualified person deenergize the circuit or equipment with a circuit-
interrupting device. There were no comments on paragraph (b)(1) of the
proposed rule. This paragraph of the section remains as proposed.
Paragraph (b)(2) of the final rule requires that a qualified person
open the disconnecting device when performing work on circuits and
equipment, and if high-voltage, ground the circuits. Opening the
disconnect device deenergizes the circuit which, along with grounding,
protects the person working on the circuit from shock and electrocution
hazards. A commenter stated that in addition to grounding the circuit
prior to work being performed, that grounding hot sticks (a collapsible
non-conductive pole used to de-energize electrical circuits) rated at
4,160 volts should be available at each power center and a proximity
tester should be used by the qualified electrician to determine that
the circuit is deenergized. In response to this comment, Sec. 75.815(b)
of the final rule requires that the disconnecting devices be maintained
in accordance with the approval requirements of paragraph (f) of
Sec. 18.53. Section 18.53(f) in turn requires that the disconnecting
devices ground the circuit when ``open.'' In addition, the requirement
in paragraph (b)(3) of Sec. 75.820 places responsibility on each
qualified person to lock out the disconnecting device for the high-
voltage circuit prior to performing work. Therefore, MSHA concludes
that equipping power centers with grounding hot sticks, clamps, and
proximity testers, as suggested by the commenter, is not necessary.
Therefore, paragraph (b)(2) of this section remains as proposed.
Paragraph (b)(3) of the final rule, like the proposed rule,
requires that disconnecting devices be locked with an individual
padlock by each person performing work. Individual padlocks, removable
only by the persons who installed them, place responsibility on the
persons performing work to assure their personal safety. This should
prevent accidental reenergization of equipment or circuits before all
persons have completed work. The danger and accident history of
reenergization of circuits before work is completed require such
measures for the protection of miners against electrocution or electric
shock. A commenter suggested that the section be reworded to permit the
oncoming worker to install his/her lock, and the departing worker to
remove his/her lock at the change of shifts. Another commenter
suggested that MSHA recognize that service or maintenance in many cases
is performed by a new crew or group of people and that a group lockout
procedure be allowed. This commenter suggested that primary
responsibility can be vested with an authorized employee when more than
one group is working on the equipment, so that an authorized person
from each group may lockout the equipment. A review conducted by the
Agency in 1999 revealed that during the period 1970 to 1999, a total of
145 fatal accidents occurred by miners contacting energized circuits.
Data further revealed that during a five year period between 1994 and
1999, a total of nine fatal accidents were related to failure to
lockout disconnecting devices. The review also revealed that deaths and
injuries had also occurred when equipment was energized before all
persons had completed their work. Furthermore, the National Safety
Council in Data Sheet 237 Revision B, Methods of Locking Out Electrical
Switches (1971), recommends that individual, not group, type lockout
procedures be used. This publication is available in the rulemaking
record. Consistent with Agency experience and safety recommendations,
the final rule requires individual lockout rather than group lockout.
MSHA is confident that this system provides the necessary safety
protection because persons assigned to place and remove their own locks
are more cognizant of and responsible for their own security, and more
likely to take the steps necessary to assure proper deenergization.
This also reduces the risk of error due to lack of communication or
inadvertent reenergization. For these reasons, the paragraph remains
unchanged from the proposed rule.
Paragraph (b)(4) of the final rule, like the proposed rule,
requires tags used on deenergized circuits and equipment to identify
each person performing work and the circuit or equipment on which work
is being performed. There were no comments on this paragraph of the
proposed rule and it remains as proposed.
Paragraph (c) requires, like the proposed rule, that only the
persons who install a padlock and tag be permitted to remove them. This
provision also provides for an exception where an operator could
authorize someone else to remove the lock and tag if the person who
installed them is unavailable at the mine. Such authorized person is
required to be qualified to perform electrical work. Additionally, the
person who had originally installed the lock and tag must be informed
of the lock removal before resuming work on the circuit or equipment. A
commenter stated that in the absence of the person who installed
[[Page 10990]]
the lock, the mine operator may designate a qualified electrician to
remove the lock after it has been determined that all other affected
persons are not exposed to a hazard. Paragraph (c) of the final rule
requires locks to be removed by the person who installed them or by
qualified persons authorized by the operator, if that person is
unavailable at the mine.
Paragraph (d) of the final rule requires that certain safety
procedures be followed when troubleshooting and testing energized
circuits. This includes limiting troubleshooting and testing of
energized circuits only to low- and medium-voltage systems. In
addition, only qualified electricians wearing properly insulated rubber
gloves are permitted to perform this work and only for the purpose of
determining voltages and currents. This provision recognizes that, in
some instances, it is necessary for circuits or equipment to remain
energized for troubleshooting and testing. For example, in order to
understand the nature of problems within a circuit, it may be necessary
to take voltage or current readings while the circuit is energized.
Paragraph (d)(1) of the final rule, like the proposed rule, limits
troubleshooting and testing of energized circuits only to low- and
medium-voltage systems. Since troubleshooting and testing energized
circuits is known to be inherently hazardous work, the particular
skills and training of a qualified electrician are necessary for
performance of these tasks. Troubleshooting and testing is limited to
low- and medium-voltage energized circuits, primarily due to insulation
ratings of available troubleshooting and testing equipment. Insulation
ratings on equipment commonly used to troubleshoot and test in
underground mines are insufficient to protect persons if such equipment
is used to troubleshoot and test high-voltage circuits.
A commenter suggested that troubleshooting of energized circuits
ranging from 120 to 1,000 volts (low to medium voltage) should be
prohibited. This commenter indicated that the industry has already
demonstrated that high-voltage longwalls can be installed,
commissioned, and maintained without maintenance personnel being
exposed to any voltage higher than 120 volts. The commenter further
stated that if multiple utilization voltages are required in the same
compartment, then each supply should have a disconnect device, and
cover switches should be arranged to trip circuit-interrupting devices
to cut off both voltages. Some high-voltage longwalls are designed with
equipment supplied from low- and medium-voltage as well as high
voltage. These hybrid-type longwall systems include both high-voltage
and low- and medium-voltage equipment. This provision allows
troubleshooting and testing of low- and medium-voltage circuits
associated with these hybrid longwalls. Based on Agency experience with
petitions for modification allowing such testing, troubleshooting, and
testing of low- and medium-voltage circuits can be safely performed
with proper test instruments, and with use of protective gloves that
are commercially available. Therefore, paragraph (d)(1) of this section
remains as proposed.
Paragraph (d)(2) of the final rule permits troubleshooting and
testing of energized circuits only for the purpose of determining
voltages and currents (amperes). Some commenters suggested that
paragraph (d)(2) be changed to allow troubleshooting and testing to
determine waveform or other electrical diagnostic testing as well as
voltages and currents. The final rule, as written, is responsive to the
commenter's suggestion because evaluation of waveform or diagnostic
testing is normally considered to be a method of measuring voltage and
current. Paragraph (d)(2) of this section remains as proposed.
Paragraph (d)(3) of the final rule requires that troubleshooting
and testing of energized circuits be performed by persons qualified
under Sec. 75.153 who wear protective gloves when the voltage of the
circuit exceeds 40 volts. This should prevent accidents related to
contact with energized circuits while troubleshooting and testing.
These gloves will provide the insulation protection necessary if a
miner has inadvertent contact with energized circuits during
troubleshooting and testing. A commenter stated that the circuit is
designed to permit troubleshooting of 120-volt alternating current
(VAC) control power. During this period, high voltage is not present
while the normal/test auxiliary switch is in the ``test'' position and
the incoming high-voltage disconnect is in the ``open/grounded''
position. This commenter suggested that gloves be rated for 120 VAC
rather than the nominal voltage of the circuit. The Agency is not aware
of any gloves rated for less than 1,000 volts. The rating of gloves is
determined commercially through formal testing procedures established
by national standards.
Another commenter suggested that this paragraph be changed to
permit the use of dry work gloves when troubleshooting low- and medium-
voltage circuits and to permit troubleshooting of high-voltage
circuits. The commenter added that wearing rubber gloves should be
required when working with high-voltage circuits; however, requiring
that rubber gloves be worn when troubleshooting low- and medium-voltage
circuits would diminish safety. In response to these comments, MSHA
believes that rubber gloves do not permit sufficient dexterity, as do
dry cloth gloves, for the safe troubleshooting of low- and medium-
voltage circuits. For example, an ohm meter has small controls which
are difficult to operate while wearing rubber gloves and the small
metal probes used with the ohm meter are hard to pick up while wearing
rubber gloves. A serious accident could result if probes were
improperly placed in an energized circuit or dropped in close proximity
to voltages up to 995 volts. In contrast, dry work gloves allow for
manual dexterity while providing adequate protection. The commenter
specified that his company has safely used dry work gloves when
troubleshooting low- and medium-voltage circuits for 15 years. The
commenter further stated that proposed Sec. 75.820(d) would conflict
with existing Sec. 75.509--Electric power circuit and electric
equipment; deenergization in two respects. The first is that
Sec. 75.509 permits troubleshooting of high-voltage circuits, as well
as low- and medium-voltage circuits. In contrast, proposed
Sec. 75.820(d)(1) would permit troubleshooting only on low- and medium-
voltage circuits. The second is that proposed Sec. 75.820 conflicts
with MSHA's interpretation of Sec. 75.509 concerning situations where
insulated rubber gloves are required. MSHA's Program Policy Manual
states:
Work gloves in good condition are acceptable for troubleshooting
or testing energized low-or medium-voltage circuits or equipment.
High-voltage gloves, rated at least for the voltage of the circuit,
are required for troubleshooting or testing of energized high-
voltage circuits or in compartments containing exposed energized
high-voltage circuits. (This portion has been corrected by MSHA
Program Policy Update V-15.)
The commenter further stated that in order to be consistent with
Sec. 75.509, as well as prudent mining practices, proposed
Sec. 75.820(d) should be changed to permit both troubleshooting of
high-voltage circuits and use of dry work gloves for troubleshooting
low- and medium-voltage circuits.
In response the Agency states that existing Sec. 75.705--Work on
high-voltage lines; deenergizing and grounding specifically applies to
high-voltage circuits out from (outby) the longwall mining faces or
pillar workings. Section
[[Page 10991]]
75.705 specifically prohibits work on high-voltage lines underground in
relation to troubleshooting and testing of high-voltage circuits.
Section 75.509 generally applies to all electrical circuits and is less
restrictive. This final rule specifically applies to high-voltage
circuits on longwalls and is consistent with the safety requirements of
existing Sec. 75.705.
Based on Agency data and experience, it is our view that attempts
to troubleshoot and test energized high-voltage circuits using standard
test equipment, such as volt-ohm-meters, commonly used on low- and
medium-voltage circuits, is extremely hazardous. MSHA prohibits
troubleshooting and testing of energized high-voltage circuits and
equipment. The use of hand-held proximity testers to determine
shielding continuity and energized circuits is allowed under this
regulation. Troubleshooting and testing routinely involves the use of
portable test instruments equipped with attached leads and metal probes
used to move from point to point in a circuit for the purpose of
determining voltage and/or current readings needed to target problem
areas. Insulation ratings on equipment commonly used to troubleshoot
and test are insufficient to protect persons if this equipment is used
on high-voltage circuits. The commenter stated that the MSHA program
policy manual permitted troubleshooting and testing of energized high-
voltage circuits. After review, MSHA determined that this policy was
inadvertently drafted in error and specifically conflicts with
mandatory safety standard Sec. 75.705. The error was corrected in MSHA
Program Policy Update V-15. The printed-in-error version was never
officially considered or enforced as MSHA policy.
Other commenters suggested--(1) that gloves not be required under
the standard when the maximum circuit voltage does not exceed 40 volts;
(2) that dry work gloves in good condition be required when the maximum
circuit voltage does not exceed 150 volts or the circuit voltage
exceeds 150 volts but is intrinsically safe; and (3) that insulating
gloves, with protective coverings designed to prevent physical damage
to the insulating material, be required when the maximum circuit
voltage exceeds 150 volts and the circuit is not intrinsically safe.
MSHA agrees with some of the commenters' suggestions and has
written the final rule to reflect these changes. The final rule
requires the use of protective gloves when troubleshooting and testing
circuits having voltages that exceed 40 volts. Based on MSHA electrical
accident information and experience, 40 volts is the lowest voltage
level range at which shock hazards are minimized. Other mandatory
safety standards, such as Secs. 77.515--Bare signal or control wires;
voltage, 75.901--Protection of low- and medium-voltage three-phase
circuits used underground, 75.902--Low- and medium-voltage ground check
monitor circuits, and 77.902-1--Fail safe ground check circuits;
maximum voltage, use 40 volts as a minimum safety voltage range level.
Section 18.50--Protection against external arcs and sparks also uses 40
volts as a minimum voltage range level for shock hazard protection
guidelines for electrical equipment frames. Dry work gloves, in good
condition (free of holes, etc.) will be permitted on circuits where the
voltage does not exceed 120 volts nominal and on circuits where the
voltage exceeds 120 volts nominal but is intrinsically safe. The normal
control circuit nominal voltage value is 120 volts for mining
equipment. Section 75.1720--Protective clothing, requirements and MSHA
policy allow miners to use dry gloves when working on circuits up to
1000 volts. Rubber insulating gloves rated for at least the nominal
voltage of the circuit and equipped with leather protectors will be
required to be used on circuits where the voltage exceeds 120 volts
nominal but is not intrinsically safe. (See paragraphs (b)(3) and
(b)(4)). Mine equipment typically has ratings such as 220-, 480-, 995-
volts and higher. Rubber gloves are not commercially rated for each of
these voltages. Rubber insulating gloves rated at 1,000 volts are
commercially available at this time. The 1,000 volt rated gloves can be
used on each of these circuits and, in fact, offer increased protection
for troubleshooting and testing on circuits exceeding 120 volts.
MSHA's fatality data show that at least six fatalities have
occurred since 1970 due to miners' contact with energized circuits
while troubleshooting and testing. The provisions of Sec. 75.820
address electrocution and shock hazards associated with troubleshooting
and testing of the low- and medium-voltage portions of high-voltage
longwalls and provide additional protection for persons performing work
on these circuits.
Commenters suggested that the proposed rule be expanded to include
facial protection, and protective clothing to minimize the risk of
injury in case of a short circuit during troubleshooting and testing of
an energized circuit. In support of this suggestion, commenters stated
that these additional requirements were needed to protect persons from
an electrical explosion, an electrical flash, and from flying debris.
Commenters suggested that injuries could be minimized if protective
clothing, such as a leather vest instead of polyester, was worn, as
clothing made of material that melts could compound an injury.
In response, the Agency concludes that when mine operators and
miners comply with the provisions of this final high-voltage rule,
including proper testing, examination, and maintenance of circuits and
equipment, and safe procedures during troubleshooting and testing,
hazards such as flying debris, electrical arcing, and flashover can be
avoided. Electrical arcing during troubleshooting and testing is
normally due to either misapplication or misuse of test equipment. In
some cases, electrical hazards may occur as a result of circuit
insulation failure while troubleshooting. Under the final rule, only
qualified individuals must be assigned to perform troubleshooting and
testing. Further, they must perform thorough examinations, tests, and
maintenance of circuits and equipment to help guard against the
occurrence of injury due to electrical arcing caused by failure of
insulation.
Paragraph (d)(4) of the final rule requires that rubber insulated
gloves, when required, be rated at least for the nominal voltage of the
circuit. This requirement was contained in paragraph (d)(3) of the
proposed rule. Comments pertaining to this proposed rule are addressed
above. The language of this provision remains the same as the proposed,
but it is renumbered.
Paragraph (e) of the final rule, like the proposed rule, requires
deenergization of high-voltage circuits contained in a compartment with
low-or medium-voltage circuits, in order to troubleshoot or test the
low-or medium-voltage circuits. Deenergizing, grounding, and locking
out and tagging the high-voltage circuit provides protection against
the danger of accidental contact with the high-voltage circuits while
troubleshooting and testing low- and medium-voltage circuits. Some
commenters suggested that high-voltage circuits should never be located
in the same compartment with low- and medium-voltage circuits in order
to prevent persons from contacting high-voltage circuits while testing
or working on low- and medium-voltage circuits. In response to this
comment, electrical closing of high-voltage contactors contained in
motor-starter enclosures requires low-voltage magnetic components that
are a part of the contactors. Therefore, sometimes it is necessary, to
have both high voltage in
[[Page 10992]]
the form of a power circuit and low voltage in the form of a control
circuit in the same compartment(s) of the motor-starter enclosures. In
addition, compartments of motor-starter enclosures that house high-
voltage disconnect switches may also contain low-and/or medium-voltage
control and lighting transformers. The deenergization and lockout
requirements under the new standard address the safety concerns
associated with working near multiple voltage circuits. Therefore, the
Agency concludes that paragraph (e) of this section should remain as
proposed.
Paragraph (f) of the final rule requires that high-voltage cables
located in conveyor belt entries be deenergized, guarded, or isolated
by elevation prior to the installation or removal of the conveyor belt
structure. The proposed rule required that the cables be deenergized
prior to the removal of the structure. Other commenters suggested that
the deenergization requirement should apply to the installation, as
well as the removal, of conveyor belt structures. These commenters
pointed out that the same type of work is performed during belt
installation as during removal. The Agency agrees with these commenters
and has concluded that the final rule should apply to advancing as well
as retreating longwall systems. Therefore, the requirement has been
changed to apply to installation as well as removal of conveyor belt
structures. Contact with or damage to energized cables while installing
or removing conveyor belt structures could cause risks of fire and
electrocution to miners. The final rule addresses these dangers by
requiring either deenergization, guarding, or proper location of the
cables before installing or removing belt structures.
Commenters suggested that deenergizing the high-voltage cable for
removal of the belt conveyor structure is often impractical and that an
alternative would be to guard the cable from direct contact with the
belt conveyor structure during removal. Reasons given for this
alternative were: (1) Many of the routine jobs performed along the
longwall face cannot be performed with the power off (such as
repositioning of the longwall shearer, moving the shields
electronically and moving the face conveyor, as well as equipment
servicing and welding operations that typically contribute to the
normal safe and efficient operation of the longwall) and (2) Methane
monitors, face lighting, and on-board shield diagnostics would lose
power if they receive electrical power through the high-voltage system
that feeds the face equipment. In addition, the commenter pointed out
that belt structure removal occurs 2 or 3 times a shift, taking 15 to
30 minutes each time. Other commenters suggested that this provision be
deleted, since proper guarding is required by Sec. 75.816. These
commenters suggested that the requirement would result in deenergizing
cables even if work is being done 10,000 feet from the cables. Another
commenter suggested that this requirement should be waived if the high-
voltage cable is installed on monorail because personnel are safely
protected by the location of the cable.
Other reasons given for deleting the deenergization requirement
were: (1) It would be less safe for miners, as it would result in
deenergization of several longwall safety devices such as the face and
equipment illumination system; (2) It would result in an undue burden
for operators due to the time required to travel to and from the power
center in order to deenergize the cable; (3) It would cause undue
stress, wear and tear on electrical breakers, components, and cables
due to frequent energizing and deenergizing; and (4) It would prevent
most maintenance, service and support functions from being performed
while the cables were deenergized. The commenter also pointed out that
the occurrence of high-voltage cable faults is infrequent and the
commenter has no experience of faults resulting in fire or causing
shocks to miners. This commenter further stated that currently required
circuit breakers and ground-fault systems provide adequate fault
protection and that backup protection is provided by a ``Post
Gulliver'' ground-fault system at the commenter's operation. Another
commenter suggested that this requirement should only apply to cables
which are not guarded and which are located in conveyor belt entries
less than three feet away from the conveyor belt structure.
Another commenter suggested that the requirement should not apply
where the mine operator can demonstrate that the seam height provides
ample clearance of at least 6.5 feet or other methods are used to
prevent any possible mechanical damage to high-voltage cables which may
occur during removal of conveyor belt structures. Another commenter
indicated that the phrasing of the proposed rule led the commenter to
believe that MSHA was referring to the complete removal of the conveyor
belt structure (as would be the case for an advancing longwall). This
commenter indicated that operators are concerned about application of
the rule to the more common retreating longwall situation where it is
part of the routine work to frequently remove sections of conveyor
structure. This commenter indicated that procedures have been developed
to ensure that this work can be done without risk of high-voltage
cables creating a hazard.
In response to these commenters, the Agency has changed the
language of the proposed rule. The final rule allows guarding or
protection by elevation as another means of protecting cables from
damage and to minimize danger of contact with energized cables. Proper
guarding of cables in accordance with Sec. 75.816 or protection
afforded by proper elevation would minimize miner contact with cables
and minimize damage to the cables. The Agency agrees that there are
safety advantages in leaving the high-voltage cable energized if the
cable is properly protected during belt structure installation and
removal. Examples of safety equipment that would remain energized are
methane monitors and illumination systems.
Section 75.821 Testing, Examination, and Maintenance
Section 75.821 of the final rule requires that a person, qualified
to perform electrical work, test and examine equipment and circuits to
detect and correct conditions that could lead to an accident and
injury. The section requires the qualified person to verify by
signature and date that the tests and examinations have been completed.
This record will include any unsafe conditions and corrective actions
taken. The section further requires that the records be kept and made
available for at least one year. This section was derived, in part,
from existing Secs. 75.512--Electric equipment; examination, testing
and maintenance, 75.512-2--Frequency of examinations, 75.800-3--
Testing, examination and maintenance of circuit breakers; procedures,
and 75.800-4--Testing, examination, and maintenance of circuit
breakers; record which generally apply to electrical equipment
underground. This section applies to high-voltage equipment on the
longwall face or within 150 feet of the pillar workings.
Paragraph (a) of Sec. 75.821 requires that persons, qualified in
accordance with existing Sec. 75.153--Electrical work; qualified
person, test and examine high-voltage longwall equipment and circuits
to protect miners from electrical or operational hazardous that may
exist. As noted under the Sec. 75.820 discussion, based on the recent
Federal Mine Safety and Health Review Commission Black Mesa decision
(22 FMSHRC 708, 715; June 30, 2000), Sec. 75.153 requires that a
`person qualified' be knowledgeable of
[[Page 10993]]
high-, medium-, and low-voltage circuits and equipment. Consistent with
this decision and for clarification purposes, the language of paragraph
(a) has been modified in the same fashion as in Sec. 75.820(a) to
conform with the ruling under this decision and the plain meaning of
Sec. 75.153. Thus, under this paragraph as revised, a person must be
qualified under Sec. 75.153 to perform electrical work on ``all''
circuits and equipment, not just high-voltage circuits. Testing and
examining high-voltage longwall equipment and circuits allows qualified
persons to determine that the electrical protection, equipment
grounding, permissibility, cable insulation, and control devices are
properly maintained to prevent fire, electric shock, ignition or
operational hazards from existing on the equipment. Keeping equipment
free from these hazards is assured by the training and expertise of
qualified electricians. Regular testing and examination of high-voltage
equipment used in face areas assures that hazardous conditions are
discovered and corrected before they can cause injuries to miners. The
standard requires examinations and tests of high-voltage longwall
equipment at least once every 7 days.
Examinations and tests include activating the ground-fault test
circuit which is required by Sec. 75.814(c) of this final rule. The
standard assures that problems which arise during normal use of mining
equipment will be identified and corrected, so that miners are not
exposed to hazards. Activating the ground-fault test circuit will
identify any damage or defects in the ground-fault circuit and
therefore protect miners from being exposed to energized longwall
equipment frames.
A commenter stated that 30 CFR part 75 requires mine operators to
conduct a multitude of tests in the underground environment. The
commenter further stated that these tests are normally conducted on a
``daily,'' ``weekly,'' or ``monthly'' basis, and that the proposed rule
is confusing and can present a problem for those operations working
under nontraditional schedules. The commenter recommended that for
clarity and consistency, the phrase ``once every 7 days'' be removed
and the word ``weekly'' be substituted. In response to this comment,
circuits and equipment used in conjunction with high-voltage longwalls
are frequently being moved and subjected to heavy use, increasing the
likelihood of wear and breakdown. Because of this, it is extremely
important that defects in circuits and equipment be detected as quickly
as possible and repaired before the occurrence of related accidents and
injuries. The Agency considers it very important that the required
examinations and tests be conducted as frequently as possible from the
standpoint of safety and practicability, and that an examination at
least once every seven days rather than weekly provides this assurance.
A requirement for a weekly examination can result in the equipment not
being examined for as long as 13-14 days. In addition, the seven-day
requirement is consistent with similar type requirements contained in
regulations promulgated by the Agency pertaining to ventilation under
Secs. 75.312(b)(1)(ii)--Main mine fan examinations and records and
75.364(a)--Weekly examination. Another commenter suggested that the
proposed provision was too vague and in order to eliminate confusion,
submitted the following examination requirements: (1) Actuate each
ground-fault test circuit required by Sec. 75.814(c); (2) Examine the
cable guarding and handling system to ensure that they are properly
installed and protecting the cables; (3) Determine that explosion-proof
components are maintained in permissible condition; (4) Actuate the
emergency stop button and verify that the corresponding circuit-
interrupting device opens; and (5) Verify that the face communication
system is operational. Another commenter suggested that the proposed
examination requirements were so comprehensive that it would take a
skilled person two days and that the more limited examination suggested
by the previous commenter would cover the essential safety aspects.
In response to the comments regarding adoption of less time-
consuming examination requirements, the complex high-voltage longwall
mining system contains numerous cables, conductors, and pieces of
equipment that require time-consuming examinations to assure safe
operating conditions. Although proper circuit and equipment maintenance
requires both visual and physical examinations, most examinations are
visual. In addition, testing of circuits and equipment routinely
includes activating available test switches to verify proper operation
and causes the protective devices to open. High-voltage longwall
equipment contains circuit protective devices that are mounted in
heavily constructed explosion-proof enclosures containing large bolted
covers and cables that are protected by heavily constructed guarding.
The proposed rule required, in part, that a determination be made that
protective devices, in some cases contained within these enclosures,
and cables protected by the described guarding, be inspected to assure
proper maintenance. The Agency believes that verification of proper
maintenance regarding these items would not require, in all cases,
removal of the equipment covers and cable guards in order to make this
determination. Some protective device settings do not change, so
frequent removal of covers to gain access for inspection serves no
useful purpose and reduces safety if covers are not properly replaced.
Removing and replacing guards that are installed to provide mechanical
protection for cables, without good reason, could likewise result in an
unsafe condition if not properly replaced.
Since 1970, Title 30 CFR has contained an examination, test, and
maintenance requirement for electric equipment that is more basic than
Sec. 75.821. The Agency has been asked on several occasions to describe
the required extent of proper examination of circuits and equipment.
Since there are so many varieties of circuits and equipment in use in
mines, it is impractical to describe a specific inspection procedure
that applies to all circuits and equipment in all instances.
Consequently, a general type inspection procedure, such as that
contained in this final rule, is necessary. The amount of detail needed
for a given inspection is normally determined on a case-by-case basis,
as the inspection takes place. For example, the testing of ground
monitors would normally only require simple activation of readily
available test switches; however, findings revealed during this portion
of the inspection of the longwall circuits and equipment may indicate a
need for more thorough examinations and tests. For example, if an ohm
meter test determined that a condition existed in a cable, such as an
inadvertent connection between a pilot wire and ground wire rendering a
ground monitor inoperative, further examination and correction would be
required to establish effective ground monitoring. For these reasons,
the Agency concludes that the final rule require general type
examinations and tests be conducted. Therefore, except for the change
based on the Black Mesa decision, paragraph (a) of this section remains
as proposed.
Paragraph (b) of the final rule, like the proposed rule, requires
that each ground-wire monitor and corresponding circuit be examined and
tested at least once each 30 days to verify that it is operating
properly and will cause the corresponding circuit-interrupting device
to open. This procedure assures that ground-wire monitors and
corresponding circuit-interrupting
[[Page 10994]]
devices will operate properly to deenergize the circuits that they
monitor. A commenter suggested that the requirement for testing of
ground-wire monitors be relocated to another section of the rule, or
possibly Sec. 75.803--Fail safe ground check circuits on high-voltage
resistance grounded systems. The Agency has determined that the
important safety protection provided by these devices and their use on
operating high-voltage longwall equipment necessitates placing ground
monitor testing requirements in this section of the final rule. This is
required in addition to other relevant testing requirements for other
protective systems on high-voltage longwall equipment.
Another commenter suggested that the testing be limited to the
operation of appropriate control circuit test devices in the power
center or high-voltage motor-starter enclosure, and indicated that it
should not be necessary to open any explosion-proof enclosure or to
disconnect any ground wire while testing a ground-wire monitor. These
commenters suggested that language be added to the provision that
specifies the test be initiated by operating the test switch provided
as part of the ground-wire monitor, or a similar switch installed in
the power center or the high-voltage motor-starter enclosure. As stated
above, proper examination and testing of ground-wire monitors and
associated circuits, which include pilot wires and grounding
conductors, may require more than simple activation of a test switch
that normally opens the pilot wire. Therefore, paragraph (b) of this
section remains as proposed.
Paragraph (c) of the final rule requires equipment to be
immediately removed from service or immediately repaired when
examinations or tests reveal a fire, electric shock, ignition, or
operational hazard. This provision assures that equipment which may
pose a danger to miners will not be used until the hazardous condition
is corrected. Some commenters stated that the term ``immediately''
should be added to this provision. These commenters indicated that it
is of utmost importance that whenever tests and examinations reveal
malfunctions and defects, equipment must be repaired or removed from
service immediately. They pointed out that operators may be reluctant
to shut down a longwall operation to make necessary corrections and
that confrontational situations and any misinterpretations could be
avoided by adding this clarification to the standard.
The Agency agrees with the commenter and has added the word
``immediately'' to Sec. 75.821(c) of the final rule. ``Immediately'' is
intended to reflect its plain meaning that the required action be
without hesitation or delay. It is emphasized, however, that the rule
is referring to those safety defects that are considered hazardous, as
stated under Sec. 75.821(c). For example, some conditions, such as bare
energized conductors in cables or conductors, present fire, electric
shock, ignition, and possibly even operational hazards and require
either immediate removal from service or immediate repair. However,
conditions may exist that would not require immediate shutdown of
equipment, but due to the nature of the condition, would permit
continued operation of the equipment until material or parts necessary
to correct the condition are procured, or would permit orderly shutdown
of equipment prior to repair. For example, Sec. 75.816 of this final
rule requires guarding of high-voltage cables in specific locations.
Unless there are other extenuating circumstances such as damaged cable
or bare conductors present, a torn portion of guarding material would
not be judged a condition that would have to be corrected immediately.
It is the Agency's intent that once a condition with the potential to
result in a fire, electric shock, ignition, or operational hazard is
revealed correction of the condition should begin immediately. This
includes arranging for orderly shutdown or removal of the equipment for
repair until the necessary repair parts are obtained and installed.
Paragraph (d) of the final rule, like the proposed rule, requires
the person who performs examinations and tests to certify by signature
and date that they have been conducted. Also, a record is required for
any unsafe condition found and any corrective action taken. This unsafe
condition need not be an immediate hazard to be reported. In addition,
certifications and records are required to be kept for at least one
year and made available at the mine for inspection by authorized
representatives of the Secretary and representatives of miners at the
mine. Records and certifications of tests and repairs are valuable
tools for mine operators and can be used to point out patterns of
equipment defects and facilitate improvements in equipment maintenance
and design. These records and certifications will assist in identifying
that the required examinations were conducted, and will also assist in
the investigation of accidents.
A commenter suggested that requiring the examiner's signature is
not necessary and eliminates other responsible persons from entering
the information as is currently allowed. This commenter pointed out
that the results of the examination could be allowed to be entered by
the examiner or by a responsible mine official, or information could be
transferred from a checklist filled out by the examiner. In response to
this commenter, high-voltage longwalls contain complex circuits and
equipment that require examinations and tests be conducted only by
qualified persons knowledgeable about equipment function and operation.
These persons routinely acquire this knowledge through numerous hours
of education, training, and experience. Once inspections, including
required examinations and tests, of high-voltage longwalls are
conducted by qualified persons, it can be concluded that these
individuals are the only ones that have the necessary detailed
knowledge and understanding of the results of the inspection. Because
of this, it is appropriate that only these persons certify by signature
and date that the required examinations and tests have been conducted
and that unsafe conditions found have been corrected and recorded. This
approach is consistent with other examination and recordkeeping
requirements promulgated by MSHA.
Another commenter suggested that the operator maintain a written
record of each test, examination, repair or adjustment of all circuit
breakers protecting high-voltage circuits which enter any underground
area of the coal mine and that such records be maintained in a book
approved by the Secretary. These commenters indicated that such records
are necessary to assure that tests and examinations have been made and
would indicate which pieces of electrical equipment were tested and
examined and which ones were not. They suggested that a reduction in
the amount of recordkeeping diminishes the operator's accountability to
provide proof that all equipment has been tested and examined. In
response to this commenter, even though existing Sec. 75.512 requires
examination of all electric equipment, proposed Secs. 75.814 through
75.822 are specific to high-voltage longwall circuits and equipment and
not just high-voltage circuit breakers. Since proper test, examination,
and maintenance of circuits and equipment is considered to be of
extreme importance for the protection of personnel, the Agency
concluded it was necessary to draft an examination and testing standard
for high-voltage longwall circuits and
[[Page 10995]]
equipment. As stated above, the wording of Sec. 75.821(d), which in
part, requires that the person who completes the examination and tests
certify by signature and date that they have been conducted. This
approach is generally consistent with requirements in other regulations
promulgated by the Agency. This certification and recording requirement
only pertains to high-voltage longwall systems, including associated
low- and medium-voltage circuits and equipment. The requirements of
Sec. 75.512 remain in effect for circuits and equipment in the mine
other than that used on high-voltage longwall systems. Therefore,
paragraph (d) of this section remains as proposed.
Section 75.822 Underground High-Voltage Longwall Cables
Section 75.822 of the final rule is new, derived in part from
existing Sec. 75.804--Underground high-voltage cables. It has been
added since the proposed rule in specific response to commenters, and
is a logical outgrowth of this high-voltage longwall rulemaking. This
section differs from the requirements of Sec. 75.804 by permitting the
use of high-voltage cables that have an insulated center ground-check
conductor that is smaller than a No. 10 AWG conductor. The Agency
developed this new provision in response to industry requests and to
accommodate new cable design technology that can either eliminate or
significantly minimize inter-machine arcing due to the reduction of
current induced into the ground-check conductor. This new cable design
technology developed from MSHA and the industry's experience with using
smaller ground-monitor conductor sizes in high-voltage longwall cables
under MSHA granted modifications. This experience, together with
comments from the high-voltage longwall rulemaking process, caused MSHA
to conclude that such cable designs should be permitted under the final
rule. The development of affordable smaller conductors resulted
directly from the high-voltage longwall equipment design and use
experience under granted modifications.
Two commenters suggested that a regulation be developed to permit
the use of high-voltage cables that have a center ground-check
conductor smaller than a No. 10 AWG conductor that is presently
required under Sec. 75.804(a). The commenters further stated that MSHA
has allowed the use of a smaller ground-check conductor for high-
voltage cables through the use of Sec. 101(c) of the Mine Act for
petitions for modification. One of these commenters stated that the use
of a center ground-check conductor can either eliminate or
significantly minimize inter-machine arcing and also provides improved
ground-check monitor performance by reducing induced current into the
ground-check conductor.
The Agency agrees with these comments, and includes a new section
permitting this cable design use in light of its experience with high-
voltage longwall petitions. As noted above, these new cable design
provisions arise from technology developments referenced by commenters
in response to the proposed rule and from the high-voltage longwall
experience under the petition process. This section includes
requirements from Sec. 75.804 and allows the use of high-voltage
longwall equipment cables that are designed with a center ground-check
insulated conductor smaller than No. 10 AWG and metallic shields around
each power conductor. Acceptable cables are those manufactured to meet
nationally recognized consensus standards, such as the Insulated Cable
Engineers Association (ICEA) standards and, as provided by the final
rule, are designed with a stranded ground-check conductor that is no
smaller than No. 16 AWG and is located in the center interstice of the
cable conductors. The national consensus standards are developed by
recognized experts in their fields. These cables, through the Mine Act
Sec. 101(c) petition for modification process, have been used on
longwall mining equipment for the past several years and provide the
necessary protection from physical damage or stress to the No. 16 AWG
center ground-check conductor.
For these reasons, the Agency has determined that allowing the use
of a No. 16 AWG center ground-check conductor can provide equivalent or
improved protection as provided by a regular No. 10 AWG conductor.
Improved protection is provided by the No. 16 AWG ground-check
conductor because it is located in the center of the cable creating
cable conductor symmetry. This greatly minimizes induced currents and
voltages that have been found to occur when using cables where the
ground-check conductors are located in the interstices between the
phase conductors. These induced currents and voltages can result in
arcing, fire or ignition hazards. Using cables with No. 10 AWG
conductors has required the installation of external arc-suppression
devices to prevent induced currents and voltages. Therefore, permitting
cables with No. 16 AWG conductors located in the center of the cables,
brings a safer, more efficient, and less burdensome ground-wire monitor
system to the mining industry. This small ground-check conductor size
is not a requirement but is offered to give added flexibility to mine
operators and to minimize their cost burden where feasible. This option
became available to the coal industry and coal mine equipment
manufacturers as it was developed and used in high-voltage longwall
systems under the petition for modification process during the last
seven years.
With the advent of high-voltage longwall face equipment, the
development and use of No. 16 AWG ground-check conductors for high-
voltage longwall equipment became an affordable technology with
additional safety benefits. This standard also eliminates the need for
Sec. 75.804(a) petitions for modification on longwalls for this purpose
and facilitates the use of improved high-voltage cable designs. These
cable designs should reduce the hazards associated with locating
severed ground-check conductors, thereby discouraging the bypassing of
ground-wire monitors when a cable has experienced a broken or severed
ground-check conductor. Mines using this cable design have reported
less downtime by having to locate and repair broken or severed ground-
check conductors.
A commenter recommended that the word ``metallic'' not be used to
describe the shielding that surrounds the individual power conductors
and that the rule should allow the use of other materials to be
incorporated in the construction of the shielding. The commenter did
not specify what other types of materials should be used as shielding
around the power conductors. Experience indicates that use of high-
voltage cables with metallic shielding that surrounds the individual
power conductors provides the intended protection against electrical
hazards. Thus, the Agency has retained the cable design specifications
that incorporate metallic shielding around each power conductor.
Section 75.1002 Installation of Electric Equipment and Conductors;
Permissibility
This section of the final rule is derived from existing
Secs. 75.1002--Location of trolley wires, trolley feeder wires, high-
voltage cables and transformers and 75.1002-1--Location of other
electric equipment; requirements for permissibility and addresses
requirements for conductors and cables used in or inby the last open
crosscut, and electric equipment and conductors and cables used within
150
[[Page 10996]]
feet of pillar workings. The final rule revises existing Sec. 75.1002
and removes Sec. 75.1002-1, which prohibited the use of high-voltage
cables inby the last open crosscut and within 150 feet of pillar
workings or longwall faces. It also revises Sec. 75.1002 related to the
use of permissible equipment in these areas.
Paragraph (a) of the final rule, like the existing rule and
proposed rule, continues to require that only permissible electric
equipment be located within 150 feet of pillar workings or longwall
faces. This equipment is specifically designed to protect miners
against fire and explosion hazards in the mining face areas such as the
longwall face where methane gas would likely accumulate and possibly
cause an ignition or explosion.
Paragraph (b) of the final rule, like the existing rule and
proposed rule, limits the types of electric conductors and cables
permitted in areas where permissible equipment is required. This
section prohibits the installation of conductors such as trolley wires
and trolley feeder wires in areas where permissible equipment is
required. Such electric conductors could provide a ready ignition
source and therefore must not be used where permissible equipment is
required. Permissible equipment is defined under 30 CFR Sec. 18.2--
Definitions and under Sec. 318(i) of the Mine Act. Such equipment is
specifically approved by MSHA for use in fire and explosive hazardous
areas. However, the new final paragraph (b)(1), like the proposed rule,
permits the use of shielded high-voltage longwall cable. Such shielding
and design protect against arcing and other electrical ignition hazards
that may occur when the outer jacket material of the cable is damaged.
The use of shielded high-voltage cables supplying power to permissible
longwall equipment reduces the risk of fire or explosion in face areas
since these cables have equivalent or superior mechanical and
electrical protective characteristics. This equipment offers other
improved safety features, such as short-circuit and ground-fault
protection against shock, fire, and explosion hazards. The final rule
continues to prohibit the use of such nonpermissible equipment not
specifically approved by MSHA for use near the actual coal extraction
areas where increased fire and explosion hazards exist.
The high-voltage longwall final rule does not apply to high-voltage
continuous miner use within 150 feet of pillar workings. High-voltage
continuous miner petitions granted under existing Sec. 75.1002
(Sec. 75.1002(b) under this final rule) will remain in effect, and mine
operators who do not have granted petitions in effect must file a
petition for modification of Sec. 75.1002(b) for the future use of
high-voltage continuous miners.
In addition, the high-voltage longwall final rule does not apply to
nonpermissible test and diagnostic equipment use. Previously granted
petitions under existing Sec. 75.1002-1(a) (Sec. 75.1002(a) under this
final rule) will remain in effect. After the effective date of this
rule, mine operators who do not have granted petitions in effect must
file a petition for modification for the use of nonpermissible test and
diagnostic equipment under Sec. 75.1002(a).
In response to a commenter's suggestion, MSHA has added the term
``longwall faces'' to paragraph (b) of the section. While longwall
faces are generally considered to be part of a pillar working, the use
of this term more specifically identifies the place where conductors
and cables can be used. The addition of this term also maintains
consistency with paragraph (a). This term was used in proposed
paragraph (a) to clarify that longwall faces are included as part of
the pillar working.
Paragraph (b)(1) of the final rule, like the proposed rule, permits
the use of shielded high-voltage cables supplying power to permissible
longwall equipment. Paragraphs (b)(2) through (b)(4) of the final rule,
like the existing standards, permit the use of conductors and cables of
intrinsically safe circuits, and cables and conductors supplying power
to low- and medium-voltage permissible equipment in or inby the last
open crosscut and within 150 feet of pillar workings or longwall faces.
Petitions for Modification
On the effective date of this final rule, all existing petitions
for modification for high-voltage longwall use under Sec. 75.1002 will
be superseded. Operators are thereafter required to comply with the
provisions of this final rule.
Derivation Table
The following derivation table lists: (1) Each section number of
the final rule and (2) The section number of the standard from which
the section is derived (existing section).
Derivation Table
------------------------------------------------------------------------
Final rule Existing section
------------------------------------------------------------------------
75.2...................................... Partly new.
75.813.................................... N/A.
75.814(a)(1).............................. 75.518-1 & 75.800.
75.814(a)(2).............................. N/A.
75.814(a)(3).............................. 75.802.
75.814(a)(4).............................. 75.800.
75.814(a)(5) & (6)........................ N/A.
75.814(a)(7).............................. 75.800.
75.814(b), (c) & (d)...................... N/A.
75.814(e)................................. New (75.518-1).
75.815(a) & (b)........................... 75.808.
75.815(c)................................. 75.520.
75.815(d)(1).............................. 75.601 & 75.808.
75.815(d)(2).............................. 75.705.
75.815(d)(3).............................. 75.511.
75.815(e)................................. 75.520.
75.816 & 75.817........................... 75.807.
75.818(a)................................. 75.705-6 and 75.812.
75.818(b)................................. 75.705-7 & 75.705-8.
75.819.................................... N/A.
75.820.................................... 75.153, 75.509, 75.511 &
75.705.
75.821.................................... 75.512, 75.512-1, 75.800-3 &
75.800-4.
75.822.................................... N/A.
75.1002 (revised)......................... 75.1002, 75.1002-1.
------------------------------------------------------------------------
N/A: Not Applicable.
Distribution Table
The following distribution table lists: (1) Each section number of
the existing standards and (2) The section number of the final rule
which contains provisions derived from the corresponding existing
section.
Distribution Table
------------------------------------------------------------------------
Existing section Final rule
------------------------------------------------------------------------
75.2...................................... Partly new 75.2.
NA........................................ 75.813.
75.518-1 & 75.808......................... 75.814(a)(1).
NA........................................ 75.814(a)(2).
75.802.................................... 75.814(a)(3).
75.800.................................... 75.814(a)(4).
NA........................................ 75.814(a)(5) & (6).
75.800.................................... 75.814(7).
NA........................................ 75.814(b), (c) & (d).
New (75.518-1)............................ 75.814 (e).
75.808.................................... 75.815 (a) & (b).
75.520.................................... 75.815 (c).
75.601 & 75.808........................... 75.815 (d)(1).
75.705.................................... 75.815 (d)(2).
75.511.................................... 75.815 (d)(3).
75.520.................................... 75.815 (e).
75.807.................................... 75.816 & 75.817.
75.705-6 & 75.812......................... 75.818 (a).
75.705-7 & 75.705-8....................... 75.818 (b).
NA........................................ 75.819.
75.153, 75.509, 75.511 75.705............. 75.820.
75.512, 75.512-1, 75.800-3 & 75.800-4..... 75.821.
NA........................................ 75.822.
75.1002 (Revised) & 75.1002-1 (Removed)... 75.1002.
------------------------------------------------------------------------
NA--Not Applicable.
III. Paperwork Reduction Act
The information collection requirements contained in this final
rule
[[Page 10997]]
have been submitted to the Office of Management and Budget (OMB) for
review under the Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3520),
as implemented by OMB in regulations at 5 CFR part 1320. The Paperwork
Reduction Act of 1995 (PRA 95) defines collection of information as
``the obtaining, causing to be obtained, soliciting, or requiring the
disclosure to third parties or the public of facts or opinions by or
for an agency regardless of form or format.''
This rule contains information collection requirements for high-
voltage longwall operators in Sec. 18.53(h), Sec. 75.820(b),
Sec. 75.820(e) and Sec. 75.821(d). Annual paperwork burden hours and
costs from these provisions are given in the following table. The total
first year paperwork burden hours and costs of the rule are 5,736 hours
and $163,929, respectively. The total burden hours and costs in each
year thereafter will be 5,732 hours and $163,806, respectively.
Manufacturers seeking approval for longwall equipment continue to
be required to submit applications for approval including related
drawings, drawing lists, specifications, wiring diagrams, and
descriptions. The paperwork burden for this application process is
approved as part of a petition for modification, under OMB Control
Number 1219-0065.
The information collection requirements contained in this rule for
part 75 were submitted to OMB for review under the Paperwork Reduction
Act of 1995 and were approved under OMB Control Number 1219-0116. This
Control Number, however, expired in 1994, and the information
requirements have been resubmitted to OMB for reinstatement. In
accordance with Sec. 1320.11(h) of the implementing regulations, OMB
has 60 days from today's publication date in which to approve,
disapprove, or instruct MSHA to make a change to the information
collection requirements in this final rule.
Table of Annual Burden hours and Costs From the Rule
----------------------------------------------------------------------------------------------------------------
Annual burden Annual burden
Annual burden hours for Annual burden costs for
Hours in each year costs in each year
first year thereafter first year thereafter
----------------------------------------------------------------------------------------------------------------
Section 18.53(h)................................ 7 3 $247 $124
Section 75.820(b) and (e)....................... 1604 1604 45,831 45,831
Section 75.821(d)............................... 4125 4125 117,851 117,851
---------------------------------------------------------------
Total....................................... 5736 5732 163,929 163,806
----------------------------------------------------------------------------------------------------------------
IV. Executive Order 12866 and Regulatory Flexibility Act
Executive Order 12866 requires that regulatory agencies assess both
the costs and benefits of regulations. MSHA has determined that this
final rule will not have an annual effect of $100 million or more on
the economy and that, therefore, they are not an economically
significant regulatory action pursuant to Sec. 3(f)(1) of Executive
Order (E.O.) 12866. However, we have determined that this final rule is
significant under Sec. 3(f)(4) of E.O. 12866, which defines a
significant regulatory action as one that may ``* * * raise novel legal
or policy issues arising out of legal mandates, the President's
priorities, or the principles set forth in the Executive Order.'' MSHA
completed a Regulatory Economic Analysis (REA) in which the economic
impact of the rule is estimated. The REA is available from MSHA and is
summarized as follows.
Population-at-Risk
MSHA estimates that this rulemaking would initially affect
approximately 14,229 miners at 43 underground coal mines and six mines
employing about 1,667 miners that would begin using high-voltage
longwall equipment in the first year of the rule. The rule would not
increase costs to small mines, which MSHA has traditionally defined as
having fewer than 20 employees, because such mines do not use longwall
equipment.
Benefits
The more stringent criteria and design features associated with
high-voltage systems, such as compartment covers that are interlocked
to prevent access to energized high-voltage conductors and equipment
designed to facilitate safe testing procedures, decrease the likelihood
of electrical accidents. In addition, high-voltage cables are required
to be shielded around each conductor (SHD type) whereas medium-voltage
cables can be shielded around the circumference of the cable (SHC
type). The SHD cables are safer than the SHC cables because shielding
the individual power conductors reduces the possibility of a short
circuit that can cause a fire, or a shock and burn hazard when a miner
touches a cable. The SHD shielding reduces the possibility of a shock
hazard because an exposed energized conductor will contact the SHD
shielding and activate the ground-fault protection, which removes power
to the cable. The use of high-voltage SHD cables reduces the chances of
cable damage which, in turn, reduces the chances of a miner coming into
contact with an energized conductor(s).
Further, the use of high voltage in longwall mining operations may
reduce the number of power cables running between various pieces of
longwall equipment. In certain situations, the cables may also be
smaller, for example, 5,000-volt (high-voltage) power cables are
smaller and weigh less than 1,000-volt (medium-voltage) power cables.
As a result of fewer and lighter power cables, the risk of injuries
from handling power cables during longwall installation, movement, or
replacement may be reduced.
Increased productivity gains can be realized when using high
voltage rather than medium voltage. In cases where medium voltage is
used to power larger motors and heavier duty longwall equipment,
current (amperes) can increase, causing motors and/or cables to
overheat. However, if high voltage rather than medium voltage is used
to power the larger motors and heavier duty longwall equipment, current
(amperes) is reduced, and the risk of overheating motors and/or cables
diminishes. Also, motor start-up is easier when using high voltage.
This increased reliability may reduce the amount of longwall equipment
downtime, thereby enhancing coal productivity.
Section 75.818(b)(1) and (2) requires that high-voltage insulated
gloves, sleeves, and other insulated personal protective equipment be
rated as Class 1 or higher, be visibly examined before each use for
signs of damage, and that such protective equipment be removed
[[Page 10998]]
from the underground area of the mine when damaged or defective.
Section 75.818(b)(3) requires that insulated personal protective
equipment be electrically tested every six months.
Section 75.820(d)(3) requires qualified electricians to wear
properly rated rubber gloves in order to perform troubleshooting and
testing on low- and medium-voltage circuits in a high-voltage
compartment. Currently, petitions for modification do not have this
requirement. Thus, Sec. 75.820(d)(3) provides additional safety
protection during this troubleshooting and testing.
Finally, the rule continues the same electrical safety requirements
developed in the petitions for modification to use high-voltage
longwalls.
Compliance Costs
This rule will result in yearly net savings of $23,083,980. This
includes a savings per conversion of $6,753,851 attributed to each
medium-voltage longwall unit that converts to high-voltage usage. These
conversion savings consist of $6,733,280 for accelerated production
savings per unit, and $20,571 for filed petition savings per unit.
The net economic effect of the rule includes substantially
increased productivity and cost savings for each longwall unit that
converts to high-voltage equipment and cables, and a small cost
annually for each longwall unit that uses high-voltage equipment and
cables. Accelerated production savings are savings due to the more
productive high-voltage equipment being used sooner rather than later.
Filed petition savings refer to savings due to eliminating legal fees
and expenses connected with a filed petition. The elimination of the
need to file petitions for modification to use high-voltage longwalls
will reduce the costs associated with the petition process and will
require less paperwork.
MSHA estimates that the petition process would have imposed costs
for legal fees and expenses of about $5,250 for an unopposed petition
filing and $112,500 for an opposed petition requiring litigation,
including proceedings before Administrative Law Judges, the Assistant
Secretary, and courts of appeal. Since 14.3 percent (1 out of 7) of all
petitions granted by MSHA in 1998 were contested and required an ALJ's
decision, MSHA assumes this same percentage would be contested were
future petitions to be filed. Thus, elimination of the petition process
would generate a one-time filed petition savings per high-voltage
longwall unit of $20,571.
In addition, eliminating the petition process would produce further
savings for medium-voltage longwall units that convert to high-voltage
units. The rule would eliminate delayed production that could occur as
a result of a mine not being able to synchronize initial start-up of
its high-voltage longwall equipment with the granting of a petition.
The medium-voltage longwall units that convert would have the
opportunity to obtain higher productivity yields from the use of high
voltage sooner under the rule than under current procedures. Based on
an average 66.1 percent increased productivity of high-voltage
longwalls over lower-voltage longwalls and an average delayed
production time of 78 working days, MSHA estimates that the one-time
conversion accelerated production savings due to the petition process
would be about $6,733,280 per high-voltage longwall unit.
With respect to individual provisions concerning the 43 existing
mines that currently use high-voltage equipment and the medium-voltage
longwall units that would shift to high voltage, Sec. 75.818(b)(4)
would require mines to perform an electrical test of personal
protective equipment every six months. Section 75.820(d)(3) would
require electricians to wear properly-rated rubber gloves to perform
troubleshooting and testing on low- and medium-voltage circuits that
are contained in a compartment with high-voltage circuits. Compliance
cost increases of $90 per longwall unit and $168 per longwall unit are
identified with Secs. 75.818(b)(4) and 75.820(d)(3), respectively.
Economic Impact
The rule enhances productivity in those affected mines because it
allows more efficient high-voltage longwall equipment to be established
more rapidly in the relatively few underground coal mines in which it
can be profitably employed. MSHA has concluded that the rule will have
only a small (but favorable) effect on coal output, price, and
profitability.
Feasibility
MSHA has concluded that the requirements of the final rule are both
technologically and economically feasible.
This final rule is not a technology-forcing standard and does not
involve activities on the frontiers of scientific knowledge. The
equipment testing, recordkeeping, and rubber glove requirements all
involve standard procedures or simple, off-the-shelf technologies.
Other provisions of the final rule will reduce recordkeeping and
petition requirements.
The final rule is clearly economically feasible insofar as it
provides a yearly net savings of $23.08 million to high-voltage
longwall mines. This includes a one-time savings of $6.75 million for
each longwall mine that converts to high voltage as well as annual
costs of $258 for each high-voltage longwall mine.
Regulatory Flexibility Act and Small Business Regulatory Enforcement
Fairness Act (SBREFA)
The Regulatory Flexibility Act (RFA) requires regulatory agencies
to consider a rule's impact on small entities. For the purposes of the
RFA and this certification, MSHA has analyzed the impact of the final
rule and has determined that there will be a cost savings to small
entities affected by this rule.
MSHA will mail a copy of the final rule, including the preamble and
regulatory flexibility certification statement, to all underground coal
mine operators and miners' representatives. The final rule will also be
placed on MSHA's Internet Homepage at http://www.msha.gov, under
Statutory and Regulatory Information.
In accordance with Sec. 605 of the RFA, MSHA certifies that this
final rule will not have a significant adverse economic impact on a
substantial number of small entities. No small governmental
jurisdictions or nonprofit organizations are affected.
Under the Small Business Regulatory Enforcement Fairness Act
amendments to the RFA, MSHA must include in the final rule a factual
basis for this certification. The Agency also must publish the
regulatory flexibility certification in the Federal Register, along
with its factual basis.
Factual Basis for Certification
The Agency compared the gross costs of the rule for small mines in
each sector to the revenue for that sector for both size categories
analyzed (MSHA and Small Business Administration `small entity'
definitions). Given that the gross compliance costs for small mines is
substantially less than 1 percent of revenue and that net costs are
negative, MSHA concludes that there is no significant cost impact of
the rule on small entities that use high-voltage longwall units.
Other small entities potentially affected by the rule are small
manufacturers of high-voltage longwall equipment. MSHA concludes that
the rule would not have a significant impact upon a substantial number
of small
[[Page 10999]]
manufacturers of high-voltage longwall equipment.
MSHA also has determined that there are no initial net compliance
costs as a result of this rule. The final rule results in a net
savings. Currently mine operators are required to file a petition for
modification to use high-voltage longwall equipment. This is a costly
and lengthy administrative process. This final rule increases safety,
effectiveness, and efficiency in the use of high-voltage longwall
equipment. The lengthy approval process will be eliminated. The Agency
estimates that six existing longwall mines will convert to high voltage
and an additional three new longwall mines each year will elect to
adopt high-voltage technology in the future.
Unfunded Mandates Reform Act of 1995
For purposes of the Unfunded Mandates Reform Act of 1995, as well
as E.O. 12875, this rule does not include any Federal mandate that may
result in increased expenditures by State, local, and tribal
governments, or increased expenditures by the private sector of more
than $100 million. MSHA is not aware of any State, local, or tribal
government that either owns or operates underground coal mines.
Executive Order 13132
MSHA has reviewed this rule in accordance with Executive Order
13132 regarding federalism, and has determined that it does not have
``federalism implications.'' The rule does not ``have substantial
direct effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government.'' There are no
underground coal mines or manufacturers of high-voltage longwall
equipment owned or operated by any State governments.
Executive Order 13045
In accordance with Executive Order 13045, MSHA has evaluated the
environmental health and safety effect of the final rule on children.
The Agency has determined that the final rule will have no effect on
children.
Executive Order 13084
In accordance with Executive Order 13084, MSHA certifies that the
high-voltage longwall final rule does not impose substantial direct
compliance costs on Indian tribal governments. MSHA is not aware of any
Indian tribal governments which either own or operate underground coal
mines or manufacturers high-voltage longwall equipment.
Executive Order 12630
This rule is not subject to Executive Order 12630, Governmental
Actions and Interference with Constitutionally Protected Property
Rights, because it does not involve implementation of a policy with
takings implications.
Executive Order 12988
This regulation has been drafted and reviewed in accordance with
Executive Order 12988, Civil Justice Reform, and will not unduly burden
the Federal court system. The regulation has been written so as to
minimize litigation and provide a clear legal standard for affected
conduct, and has been reviewed carefully to eliminate drafting errors
and ambiguities.
Executive Order 13211 (Energy)
In accordance with Executive Order 13211, MSHA has reviewed this
final rule for its energy impacts. We have determined that the
Executive Order does not apply to this final rule for the following
reasons. One, this rulemaking is not considered a ``significant
regulatory action'' under Executive Order 12866 and therefore the
action does not meet the criteria listed in Executive Order 13211
requiring a Statement of Energy Effects. Two, the proposed rule was
published before the effective date of the Executive Order. Three, MSHA
has determined that this final rule will not have any adverse effects
on energy supply, distribution, or use. To the contrary, as summarized
in the economic analysis, MSHA expects accelerated coal production
because of the implementation of this final rule. Therefore, no
reasonable alternatives to this action are necessary.
List of Subjects
30 CFR Part 18
Approval regulations, Electric motor-driven mine equipment and
accessories, Mine safety and health.
30 CFR Part 75
High-voltage longwall, Incorporation by reference, Mandatory safety
standards, Mine safety and health, Underground coal mines.
Dated: February 25, 2002.
Dave D. Lauriski,
Assistant Secretary of Labor for Mine Safety and Health.
For the reasons set out in the preamble, chapter I of title 30 of
the Code of Federal Regulations is amended as follows:
PART 18--ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES
1. The authority citation for part 18 continues to read as follows:
Authority: 30 U.S.C. 957, 961.
2. Add Sec. 18.53 to subpart B of part 18 to read as follows:
Sec. 18.53 High-voltage longwall mining systems.
(a) In each high-voltage motor-starter enclosure, with the
exception of a controller on a high-voltage shearer, the disconnect
device compartment, control/communications compartment, and motor
contactor compartment must be separated by barriers or partitions to
prevent exposure of personnel to energized high-voltage conductors or
parts. In each motor-starter enclosure on a high-voltage shearer, the
high-voltage components must be separated from lower voltage components
by barriers or partitions to prevent exposure of personnel to energized
high-voltage conductors or parts. Barriers or partitions must be
constructed of grounded metal or nonconductive insulating board.
(b) Each cover of a compartment in the high-voltage motor-starter
enclosure containing high-voltage components must be equipped with at
least two interlock switches arranged to automatically deenergize the
high-voltage components within that compartment when the cover is
removed.
(c) Circuit-interrupting devices must be designed and installed to
prevent automatic reclosure.
(d) Transformers with high-voltage primary windings that supply
control voltages must incorporate grounded electrostatic (Faraday)
shielding between the primary and secondary windings. The shielding
must be connected to equipment ground by a minimum No. 12 AWG grounding
conductor. The secondary nominal voltage must not exceed 120 volts,
line to line.
(e) Test circuits must be provided for checking the condition of
ground-wire monitors and ground-fault protection without exposing
personnel to energized circuits. Each ground-test circuit must inject a
primary current of 50 percent or less of the current rating of the
grounding resistor through the current transformer and cause each
corresponding circuit-interrupting device to open.
(f) Each motor-starter enclosure, with the exception of a
controller on a high-voltage shearer, must be equipped with
[[Page 11000]]
a disconnect device installed to deenergize all high-voltage power
conductors extending from the enclosure when the device is in the
``open'' position.
(1) When multiple disconnect devices located in the same enclosure
are used to satisfy the above requirement they must be mechanically
connected to provide simultaneous operation by one handle.
(2) The disconnect device must be rated for the maximum phase-to-
phase voltage and the full-load current of the circuit in which it is
located, and installed so that--
(i) Visual observation determines that the contacts are open
without removing any cover;
(ii) The load-side power conductors are grounded when the device is
in the ``open'' position;
(iii) The device can be locked in the ``open'' position;
(iv) When located in an explosion-proof enclosure, the device must
be designed and installed to cause the current to be interrupted
automatically prior to the opening of the contacts; and
(v) When located in a non-explosion-proof enclosure, the device
must be designed and installed to cause the current to be interrupted
automatically prior to the opening of the contacts, or the device must
be capable of interrupting the full-load current of the circuit.
(g) Control circuits for the high-voltage motor starters must be
interlocked with the disconnect device so that--
(1) The control circuit can be operated with an auxiliary switch in
the ``test'' position only when the disconnect device is in the open
and grounded position; and
(2) The control circuit can be operated with the auxiliary switch
in the ``normal'' position only when the disconnect switch is in the
closed position.
(h) A study to determine the minimum available fault current must
be submitted to MSHA to ensure adequate protection for the length and
conductor size of the longwall motor, shearer and trailing cables.
(i) Longwall motor and shearer cables with nominal voltages greater
than 660 volts must be made of a shielded construction with a grounded
metallic shield around each power conductor.
(j) High-voltage motor and shearer circuits must be provided with
instantaneous ground-fault protection of not more than 0.125-amperes.
Current transformers used for this protection must be of the single-
window type and must be installed to encircle all three phase
conductors.
(k) Safeguards against corona must be provided on all 4,160 voltage
circuits in explosion-proof enclosures.
(l) The maximum pressure rise within an explosion-proof enclosure
containing high-voltage switchgear must be limited to 0.83 times the
design pressure.
(m) High-voltage electrical components located in high-voltage
explosion-proof enclosures must not be coplanar with a single plane
flame-arresting path.
(n) Rigid insulation between high-voltage terminals (Phase-to-Phase
or Phase-to-Ground) must be designed with creepage distances in
accordance with the following table:
Minimum Creepage Distances
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minimum creepage distances (inches) for comparative tracking index (CTI) range
\1\
Phase to phase voltage Points of measure -------------------------------------------------------------------------------
CTI500 380CTI500 175CTI380 CTI175
--------------------------------------------------------------------------------------------------------------------------------------------------------
2,400...................................... - 1.50 1.95 2.40 2.90
-G 1.00 1.25 1.55 1.85
4,160...................................... - 2.40 3.15 3.90 4.65
-G 1.50 1.95 2.40 2.90
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Assumes that all insulation is rated for the applied voltage or higher.
(o) Explosion-proof motor-starter enclosures must be designed to
establish the minimum free distance (MFD) between the wall or cover of
the enclosure and uninsulated electrical conductors inside the
enclosure in accordance with the following table:
High-Voltage Minimum Free Distances (MFD)
----------------------------------------------------------------------------------------------------------------
Steel MFD (in) Aluminum MFD (in)
Wall/cover thickness (in) -----------------------------------------------------------------------------
A \1\ B \2\ C \3\ A B C
----------------------------------------------------------------------------------------------------------------
\1/4\............................. 2.8 4.3 5.8 \4\ NA \4\ NA \4\ NA
\3/8\............................. 1.8 2.3 3.9 8.6 12.8 18.1
\1/2\............................. * 1.2 2.0 2.7 6.5 9.8 13.0
\5/8\............................. * 0.9 1.5 2.1 5.1 7.7 10.4
\3/4\............................. * 0.6 * 1.1 1.6 4.1 6.3 8.6
1................................. (*) * 0.6 * 1.0 2.9 4.5 6.2
----------------------------------------------------------------------------------------------------------------
Note *: The minimum electrical clearances must still be maintained.
\1\ Column A specifies the MFD for enclosures that have available 3-phase bolted short-circuit currents of
10,000 amperes rms or less.
\2\ Column B specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit
currents greater than 10,000 and less than or equal to 15,000 amperes rms.
\3\ Column C specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit
currents greater than 15,000 and less than or equal to 20,000 amperes rms.
\4\ Not Applicable--MSHA doesn't allow aluminum wall or covers to be \1/4\ inch or less in thickness (Section
18.31).
(1) For values not included in the table, the following formulas on
which the table is based may be used to determine the minimum free
distance.
[[Page 11001]]
(i) Steel Wall/Cover:
[GRAPHIC] [TIFF OMITTED] TR11MR02.001
(ii) Aluminum Wall/Cover:
[GRAPHIC] [TIFF OMITTED] TR11MR02.002
Where C is 1.4 for 2,400 volt systems or 3.0 for 4,160 volt systems,
Isc is the 3-phase short circuit current in amperes of the
system, t is the clearing time in seconds of the outby circuit-
interrupting device and d is the thickness in inches of the metal wall/
cover adjacent to an area of potential arcing.
(2) The minimum free distance must be increased by 1.5 inches for
4,160 volt systems and 0.7 inches for 2,400 volt systems when the
adjacent wall area is the top of the enclosure. If a steel shield is
mounted in conjunction with an aluminum wall or cover, the thickness of
the steel shield is used to determine the minimum free distances.
(p) The following static pressure test must be performed on each
prototype design of explosion-proof enclosures containing high-voltage
switchgear prior to the explosion tests. The static pressure test must
also be performed on every explosion-proof enclosure containing high-
voltage switchgear, at the time of manufacture, unless the manufacturer
uses an MSHA accepted quality assurance procedure covering inspection
of the enclosure. Procedures must include a detailed check of parts
against the drawings to determine that the parts and the drawings
coincide and that the minimum requirements stated in part 18 have been
followed with respect to materials, dimensions, configuration and
workmanship.
(1) Test procedure. (i) The enclosure must be internally
pressurized to at least the design pressure, maintaining the pressure
for a minimum of 10 seconds.
(ii) Following the pressure hold, the pressure must be removed and
the pressurizing agent removed from the enclosure.
(2) Acceptable performance. (i) The enclosure during pressurization
must not exhibit--
(A) Leakage through welds or casting; or
(B) Rupture of any part that affects the explosion-proof integrity
of the enclosure.
(ii) The enclosure following removal of the pressurizing agents
must not exhibit--
(A) Visible cracks in welds;
(B) Permanent deformation exceeding 0.040 inches per linear foot;
or
(C) Excessive clearances along flame-arresting paths following
retightening of fastenings, as necessary.
PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES
3. The authority citation for part 75 continues to read as follows:
Authority: 30 U.S.C. 811.
4. Amend Sec. 75.2 by adding the following definitions:
Sec. 75.2 Definitions.
* * * * *
Adequate interrupting capacity. The ability of an electrical
protective device, based upon its required and intended application, to
safely interrupt values of current in excess of its trip setting or
melting point.
* * * * *
Approval documentation. Formal papers issued by the Mine Safety and
Health Administration which describe and illustrate the complete
assembly of electrical machinery or accessories which have met the
applicable requirements of 30 CFR part 18.
* * * * *
Circuit-interrupting device. A device designed to open and close a
circuit by nonautomatic means and to open the circuit automatically at
a predetermined overcurrent value without damage to the device when
operated within its rating.
* * * * *
Ground fault or grounded phase. An unintentional connection between
an electric circuit and the grounding system.
Motor-starter enclosure. An enclosure containing motor starting
circuits and equipment.
Nominal voltage. The phase-to-phase or line-to-line root-mean-
square value assigned to a circuit or system for designation of its
voltage class, such as 480 or 4,160 volts. Actual voltage at which the
circuit or system operates may vary from the nominal voltage within a
range that permits satisfactory operation of equipment.
* * * * *
Short circuit. An abnormal connection of relatively low impedance,
whether made accidentally or intentionally, between two points of
different potential.
* * * * *
5. Part 75, Subpart I, Underground High-Voltage Distribution, is
amended by adding Secs. 75.813 through 75.822 and Appendix A under a
new undesignated center heading, high-voltage longwalls, to read as
follows:
Sec.
High-Voltage Longwalls
75.813 High-voltage longwalls; scope.
75.814 Electrical protection.
75.815 Disconnect devices.
75.816 Guarding of cables.
75.817 Cable handling and support systems.
75.818 Use of insulated cable handling equipment.
75.819 Motor-starter enclosures; barriers and interlocks.
75.820 Electrical work; troubleshooting and testing.
75.821 Testing, examination and maintenance.
75.822 Underground high-voltage longwall cables.
Appendix A to Subpart I--Diagrams of Inby and Outby Switching
* * * * *
High-Voltage Longwalls
Sec. 75.813 High-voltage longwalls; scope.
Sections 75.814 through 75.822 of this part are electrical safety
standards that apply to high-voltage longwall circuits and equipment.
All other existing standards in 30 CFR must also apply to these
longwall circuits and equipment where appropriate.
Sec. 75.814 Electrical protection.
(a) High-voltage circuits must be protected against short circuits,
overloads, ground faults, and undervoltages by circuit-interrupting
devices of adequate interrupting capacity as follows:
(1) Current settings of short-circuit protective devices must not
exceed the setting specified in approval documentation, or seventy-five
percent of the minimum available phase-to-phase short-circuit current,
whichever is less.
[[Page 11002]]
(2) Time-delay settings of short-circuit protective devices used to
protect any cable extending from the section power center to a motor-
starter enclosure must not exceed the settings specified in approval
documentation, or 0.25-second, whichever is less. Time delay settings
of short-circuit protective devices used to protect motor and shearer
circuits must not exceed the settings specified in approval
documentation, or 3 cycles, whichever is less.
(3) Ground-fault currents must be limited by a neutral grounding
resistor to not more than--
(i) 6.5 amperes when the nominal voltage of the power circuit is
2,400 volts or less; or
(ii) 3.75 amperes when the nominal voltage of the power circuit
exceeds 2,400 volts.
(4) High-voltage circuits extending from the section power center
must be provided with--
(i) Ground-fault protection set to cause deenergization at not more
than 40 percent of the current rating of the neutral grounding
resistor;
(ii) A backup ground-fault detection device to cause deenergization
when a ground fault occurs with the neutral grounding resistor open;
and
(iii) Thermal protection for the grounding resistor that will
deenergize the longwall power center if the resistor is subjected to a
sustained ground fault. The thermal protection must operate at either
50 percent of the maximum temperature rise of the grounding resistor,
or 150 deg. C (302 deg. F), whichever is less, and must open the
ground-wire monitor circuit for the high-voltage circuit supplying the
section power center. The thermal protection must not be dependent upon
control power and may consist of a current transformer and overcurrent
relay.
(5) High-voltage motor and shearer circuits must be provided with
instantaneous ground-fault protection set at not more than 0.125-
ampere.
(6) Time-delay settings of ground-fault protective devices used to
provide coordination with the instantaneous ground-fault protection of
motor and shearer circuits must not exceed 0.25-second.
(7) Undervoltage protection must be provided by a device which
operates on loss of voltage to cause and maintain the interruption of
power to a circuit to prevent automatic restarting of the equipment.
(b) Current transformers used for the ground-fault protection
specified in paragraphs (a)(4)(i) and (5) of this section must be
single window-type and must be installed to encircle all three phase
conductors. Equipment safety grounding conductors must not pass through
or be connected in series with ground-fault current transformers.
(c) Each ground-fault current device specified in paragraphs
(a)(4)(i) and (5) of this section must be provided with a test circuit
that will inject a primary current of 50 percent or less of the current
rating of the grounding resistor through the current transformer and
cause each corresponding circuit-interrupting device to open.
(d) Circuit-interrupting devices must not reclose automatically.
(e) Where two or more high-voltage cables are used to supply power
to a common bus in a high-voltage enclosure, each cable must be
provided with ground-wire monitoring. The ground-wire monitoring
circuits must cause deenergization of each cable when either the
ground-monitor or grounding conductor(s) of any cable become severed or
open. On or after May 10, 2002, parallel connected cables on newly
installed longwalls must be protected as follows:
(1) When one circuit-interrupting device is used to protect
parallel connected cables, the circuit-interrupting device must be
electrically interlocked with the cables so that the device will open
when any cable is disconnected; or
(2) When two or more parallel circuit-interrupting devices are used
to protect parallel connected cables, the circuit-interrupting devices
must be mechanically and electrically interlocked. Mechanical
interlocking must cause all devices to open simultaneously and
electrical interlocking must cause all devices to open when any cable
is disconnected.
Sec. 75.815 Disconnect devices.
(a) The section power center must be equipped with a main
disconnecting device installed to deenergize all cables extending to
longwall equipment when the device is in the ``open'' position. See
Figures I-1 and I-2 in Appendix A to this subpart I.
(b) Disconnecting devices for motor-starter enclosures must be
maintained in accordance with the approval requirements of paragraph
(f) of Sec. 18.53 of part 18 of this chapter. The compartment for the
disconnect device must be provided with a caution label to warn miners
against entering the compartment before deenergizing the incoming high-
voltage circuits to the compartment.
(c) Disconnecting devices must be rated for the maximum phase-to-
phase voltage of the circuit in which they are installed, and for the
full-load current of the circuit that is supplied power through the
device.
(d) Each disconnecting device must be designed and installed so
that --
(1) Visual observation determines that the contacts are open
without removing any cover;
(2) All load power conductors can be grounded when the device is in
the ``open'' position; and
(3) The device can be locked in the ``open'' position.
(e) Disconnecting devices, except those installed in explosion-
proof enclosures, must be capable of interrupting the full-load current
of the circuit or designed and installed to cause the current to be
interrupted automatically prior to the opening of the contacts of the
device. Disconnecting devices installed in explosion-proof enclosures
must be maintained in accordance with the approval requirements of
paragraph (f)(2)(iv) of Sec. 18.53 of part 18 of this chapter.
Sec. 75.816 Guarding of cables.
(a) High-voltage cables must be guarded at the following locations:
(1) Where persons regularly work or travel over or under the
cables.
(2) Where the cables leave cable handling or support systems to
extend to electric components.
(b) Guarding must minimize the possibility of miners contacting the
cables and protect the cables from damage. The guarding must be made of
grounded metal or nonconductive flame-resistant material.
Sec. 75.817 Cable handling and support systems.
Longwall mining equipment must be provided with cable-handling and
support systems that are constructed, installed and maintained to
minimize the possibility of miners contacting the cables and to protect
the high-voltage cables from damage.
Sec. 75.818 Use of insulated cable handling equipment.
(a) Energized high-voltage cables must not be handled except when
motor or shearer cables need to be trained. When cables need to be
trained, high-voltage insulated gloves, mitts, hooks, tongs, slings,
aprons, or other personal protective equipment capable of providing
protection against shock hazard must be used to prevent direct contact
with the cable.
(b) High-voltage insulated gloves, sleeves, and other insulated
personal protective equipment must--
(1) Have a voltage rating of at least Class 1 (7,500 volts) that
meets or
[[Page 11003]]
exceeds ASTM F496-97, ``Standard Specification for In-Service Care of
Insulating Gloves and Sleeves'' (1997).
(2) Be examined before each use for visible signs of damage;
(3) Be removed from the underground area of the mine or destroyed
when damaged or defective; and
(4) Be electrically tested every 6 months in accordance with
publication ASTM F496-97. ASTM F496-97 (Standard Specification for In-
Service Care of Insulating Gloves and Sleeves, 1997) is incorporated by
reference and may be inspected at any Coal Mine Health and Safety
District and Subdistrict Office, or at MSHA's Office of Standards, 4015
Wilson Boulevard, Arlington, VA., and at the Office of the Federal
Register, 800 North Capitol Street, NW., Suite 700, Washington, DC. In
addition, copies of the document can be purchased from the American
Society for Testing and Materials, 100 Barr Harbor Drive, West
Conshohocken, Pennsylvania 19428-2959. This incorporation by reference
was approved by the Director of the Federal Register in accordance with
5 U.S.C. 552(a) and 1 CFR part 51.
Sec. 75.819 Motor-starter enclosures; barriers and interlocks.
Compartment separation and cover interlock switches for motor-
starter enclosures must be maintained in accordance with the approval
requirements of paragraphs (a) and (b) of Sec. 18.53 of part 18 of this
chapter.
Sec. 75.820 Electrical work; troubleshooting and testing.
(a) Electrical work on all circuits and equipment associated with
high-voltage longwalls must be performed only by persons qualified
under Sec. 75.153 to perform electrical work on all circuits and
equipment.
(b) Prior to performing electrical work, except for troubleshooting
and testing of energized circuits and equipment as provided for in
paragraph (d) of this section, a qualified person must do the
following:
(1) Deenergize the circuit or equipment with a circuit-interrupting
device.
(2) Open the circuit disconnecting device. On high-voltage
circuits, ground the power conductors until work on the circuit is
completed.
(3) Lock out the disconnecting device with a padlock. When more
than one qualified person is performing work, each person must install
an individual padlock.
(4) Tag the disconnecting device to identify each person working
and the circuit or equipment on which work is being performed.
(c) Each padlock and tag must be removed only by the person who
installed them, except that, if that person is unavailable at the mine,
the lock and tag may be removed by a person authorized by the operator,
provided--
(1) The authorized person is qualified under paragraph (a) of this
section; and
(2) The operator ensures that the person who installed the lock and
tag is aware of the removal before that person resumes work on the
affected circuit or equipment.
(d) Troubleshooting and testing of energized circuits must be
performed only--
(1) On low- and medium-voltage circuits;
(2) When the purpose of troubleshooting and testing is to determine
voltages and currents; and
(3) By persons qualified to perform electrical work and who wear
protective gloves on circuits that exceed 40 volts in accordance with
the following table:
------------------------------------------------------------------------
Circuit voltage Type of glove required
------------------------------------------------------------------------
Greater than 120 volts (nominal) (not Rubber insulating gloves
intrinsically safe). with leather protectors.
40 volts to 120 volts (nominal) (both Either rubber insulating
intrinsically safe and non-intrinsically gloves with leather
safe). protectors or dry work
gloves.
Greater than 120 volts (nominal) Either rubber insulating
(intrinsically safe). gloves with leather
protectors or dry work
gloves.
------------------------------------------------------------------------
(4) Rubber insulating gloves must be rated at least for the nominal
voltage of the circuit when the voltage of the circuit exceeds 120
volts nominal and is not intrinsically safe.
(e) Before troubleshooting and testing a low- or medium-voltage
circuit contained in a compartment with a high-voltage circuit, the
high-voltage circuit must be deenergized, disconnected, grounded,
locked out and tagged in accordance with paragraph (b) of this section.
(f) Prior to the installation or removal of conveyor belt
structure, high-voltage cables extending from the section power center
to longwall equipment and located in the belt entries must be:
(1) Deenergized; or
(2) Guarded in accordance with Sec. 75.816 of this part, at the
location where the belt structure is being installed or removed; or
(3) Located at least 6.5 feet above the mine floor.
Sec. 75.821 Testing, examination and maintenance.
(a) At least once every 7 days, a person qualified in accordance
with Sec. 75.153 to perform electrical work on all circuits and
equipment must test and examine each unit of high-voltage longwall
equipment and circuits to determine that electrical protection,
equipment grounding, permissibility, cable insulation, and control
devices are being properly maintained to prevent fire, electrical
shock, ignition, or operational hazards from existing on the equipment.
Tests must include activating the ground-fault test circuit as required
by Sec. 75.814(c).
(b) Each ground-wire monitor and associated circuits must be
examined and tested at least once each 30 days to verify proper
operation and that it will cause the corresponding circuit-interrupting
device to open.
(c) When examinations or tests of equipment reveal a fire,
electrical shock, ignition, or operational hazard, the equipment must
be removed from service immediately or repaired immediately.
(d) At the completion of examinations and tests required by this
section, the person who makes the examinations and tests must certify
by signature and date that they have been conducted. A record must be
made of any unsafe condition found and any corrective action taken.
Certifications and records must be kept for at least one year and must
be made available for inspection by authorized representatives of the
Secretary and representatives of miners.
Sec. 75.822 Underground high-voltage longwall cables.
In addition to the high-voltage cable design specifications in
Sec. 75.804 of this part, high-voltage cables for use on longwalls may
be a type SHD cable with a center ground-check conductor no smaller
than a No. 16 AWG stranded conductor. The cables must be MSHA accepted
as flame-resistant under part 18 or approved under subpart K of part 7.
[[Page 11004]]
Sec. 75.1002-1 [Removed]
6. Remove Sec. 75.1002-1.
7. Revise Sec. 75.1002 to read as follows:
Sec. 75.1002 Installation of electric equipment and conductors;
permissibility.
(a) Electric equipment must be permissible and maintained in a
permissible condition when such equipment is located within 150 feet of
pillar workings or longwall faces.
(b) Electric conductors and cables installed in or inby the last
open crosscut or within 150 feet of pillar workings or longwall faces
must be--
(1) Shielded high-voltage cables supplying power to permissible
longwall equipment;
(2) Interconnecting conductors and cables of permissible longwall
equipment;
(3) Conductors and cables of intrinsically safe circuits; and
(4) Cables and conductors supplying power to low- and medium-
voltage permissible equipment.
BILLING CODE 4510-43-P
[[Page 11005]]
[GRAPHIC] [TIFF OMITTED] TR11MR02.000
[FR Doc. 02-4863 Filed 3-8-02; 8:45 am]
BILLING CODE 4510-43-C
