[Federal Register Volume 75, Number 65 (Tuesday, April 6, 2010)]
[Rules and Regulations]
[Pages 17529-17553]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-7309]
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DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 18 and 75
RIN 1219-AB34
High-Voltage Continuous Mining Machine Standard for Underground
Coal Mines
AGENCY: Mine Safety and Health Administration, Labor.
ACTION: Final rule.
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SUMMARY: This final rule revises the Mine Safety and Health
Administration's (MSHA's) electrical safety standards for the
installation, use, and maintenance of high-voltage continuous mining
machines in underground coal mines. It also revises MSHA's design
requirements for approval of these mining machines. The final rule will
allow mine operators to use high-voltage continuous mining machines
with enhanced safety protection against fires, explosions, and shock
hazards and will facilitate the use of advanced equipment designs.
DATES: The final rule is effective on June 7, 2010. The incorporation
by reference in this rule is approved by the Director of the Federal
Register as of June 7, 2010.
FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director, Office
of Standards, Regulations, and Variances, MSHA, 1100 Wilson Boulevard,
Room 2350, Arlington, Virginia 22209-3939. Ms. Silvey can be reached at
[email protected] (e-mail), 202-693-9440 (voice), or 202-693-9441
(facsimile). (These are not toll-free numbers.)
SUPPLEMENTARY INFORMATION: The outline of this final rule is as
follows:
I. Introduction
A. Background
B. Petition for Modification (PFM) Requirements in the Final
Rule
II. Discussion of the Final Rule
A. General Discussion--Part 18--Electric Motor-Driven Mine
Equipment and Accessories
B. General Discussion--Part 75--Mandatory Safety Standards--
Underground Coal Mines
III. Section-by-Section Analysis
A. Part 18--Electric Motor-Driven Mine Equipment and Accessories
B. Part 75--Mandatory Safety Standards--Underground Coal Mines
IV. Executive Order 12866: Regulatory Planning and Review
A. Population at Risk
B. Benefits
C. Compliance Costs
V. Feasibility
A. Technological Feasibility
B. Economic Feasibility
VI. Regulatory Flexibility Act (RFA) and Small Business Regulatory
Enforcement Fairness Act (SBREFA)
A. Definition of a Small Mine
B. Factual Basis for Certification
VII. Paperwork Reduction Act of 1995
A. Elimination of Burden Hours
B. Annual Burden Hours
C. Details
VIII. Other Regulatory Considerations
A. The Unfunded Mandates Reform Act of 1995
B. Executive Order 13132: Federalism
C. The Treasury and General Government Appropriations Act of
1999: Assessment of Federal Regulations and Policies on Families
D. Executive Order 12630: Government Actions and Interference
With Constitutionally Protected Property Rights
E. Executive Order 12988: Civil Justice Reform
F. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
[[Page 17530]]
I. Introduction
A. Background
Horsepower for electrical equipment in mines has increased over the
years. The voltages required to operate this equipment have also
increased to accommodate the design of safe, practical, and efficient
equipment. Because of the industry's need for higher voltages and the
marked improvement in the design and manufacturing technology of high-
voltage components, MSHA has established requirements for use of high-
voltage electrical equipment such as longwall systems. This rule
establishes additional requirements to address the use and approval of
high-voltage continuous mining machines. These additional requirements
preserve safety and health protections for miners.
MSHA's existing standards do not allow the use of high-voltage
continuous mining machines because high-voltage mining machines were
not available when the standards were developed. MSHA has granted 52
Petitions for Modification (PFMs) since 1997 to allow mine operators to
use this equipment. In granting the PFMs, MSHA determined that the
methods the mine operator proposed to follow when using the high-
voltage equipment would at all times guarantee no less than the same
measure of protection afforded the miners by the existing standards.
On July 16, 2004, MSHA published a proposal (69 FR 42812) to
establish design requirements in part 18 for approval of high-voltage
continuous mining machines operating in production areas of underground
mines. The proposal also included new requirements in part 75 for the
installation, use, and maintenance of high-voltage continuous mining
machines in underground coal mines.
In the proposal, MSHA announced that it would hold four public
hearings in September 2004, and would allow comments through October
14, 2004. However, on August 23, 2004, MSHA published a notice changing
the public hearing dates to November 2004 and extending the comment
period to December 10, 2004 (69 FR 51787). Based on the review of all
comments and testimony, MSHA re-proposed provisions related to the
types of trailing cables that could be used with high-voltage
continuous mining machines and the types of cable handling equipment
that must be used when handling energized high-voltage trailing cables
(71 FR 15359, March 28, 2006). In developing the final rule, MSHA
considered the comments, hearing testimony, and granted PFMs.
B. Petition for Modification Requirements in the Final Rule
The final rule includes most of the requirements that were in the
granted PFMs. In each instance where a PFM requirement was not included
in the rule, MSHA has addressed the Agency's rationale in the section-
by-section analysis of the preamble.
This final rule supersedes all PFMs granted prior to the effective
date, and eliminates the need for mine operators to file for a PFM to
use high-voltage continuous mining machines with voltage up to 2,400
volts.
II. Discussion of the Final Rule
A. General Discussion--Part 18--Electric Motor-Driven Mine Equipment
and Accessories
The final rule addresses design requirements for approval of high-
voltage continuous mining machines. The rule is intended to prevent the
following hazards:
(1) High-voltage arcing;
(2) Ignition of a methane-air mixture surrounding the machine if an
arc or methane explosion occurs within the explosion-proof enclosure;
(3) Enclosure failure from an increased pressure rise if an arc or
methane explosion occurs within the explosion-proof enclosure; and
(4) Electrical shock hazards to miners when working with or around
high-voltage equipment.
One commenter stated that the proposal did not provide the same
level of safety that some of the granted PFMs provided. This commenter
expressed concern that MSHA was trying to issue a one-size-fits-all
regulation while mine-specific PFMs better assure safety. MSHA does not
believe that the final rule represents a generic approach or
compromises safety. MSHA reviewed all provisions contained in granted
PFMs and the final rule includes most of the provisions. However, in
some cases, the Agency revised the language in the PFMs to allow more
flexibility for mine specific conditions. The Agency explained at the
public hearing that Part 18 covers this commenter's examples and should
eliminate the concerns. Additionally, the final rule incorporates
additional safety measures such as short-circuit, under-voltage,
sensitive ground-fault protection, a look-ahead circuit, cable handling
methods, and cable inspection procedures that would assure the same
level of safety as the granted PFMs.
This final rule provides a mining environment as safe as the
existing environment and facilitates the use of advanced equipment
designs.
B. General Discussion--Part 75--Mandatory Safety Standards--Underground
Coal Mines
This final rule revises 30 CFR Part 75 to establish mandatory
electrical safety standards for the proper installation of high-voltage
continuous mining machines, electrical and mechanical protection of the
equipment, handling of trailing cables, and procedures for performing
electrical work. These safety standards include new provisions as well
as most of the provisions contained in granted PFMs.
There are 27 high-voltage continuous mining machines used in 8
underground coal mines that have been granted PFMs. Some of the
requirements in this final rule are not included in those PFMs.
Accordingly, mine operators with granted PFMs who wish to continue
using high-voltage continuous mining machines will be required to
comply with the additional requirements specified in this final rule.
These additional requirements include new testing and recordkeeping
requirements for tramming the machine in and out of the mine. In
addition, there may be other new provisions that mine operators must
adopt, such as following the cable manufacturers' recommended
procedures when pulling the trailing cable with equipment other than
the continuous mining machine (See Sec. 75.828).
The final rule also revises Sec. 75.1002 by adding paragraph
(b)(5) to allow the use of high-voltage continuous mining machines in
areas where permissible equipment is required.
III. Section-by-Section Analysis
A. Part 18--Electric Motor-Driven Mine Equipment and Accessories
Section 18.54 High-Voltage Continuous Mining Machines
Final Sec. 18.54(a) is derived from existing requirements for
high-voltage longwall mining systems and is similar to the proposal.
The final rule retains the proposed requirement that low- and medium-
voltage circuits in each motor-starter enclosure be separated from
high-voltage circuits by barriers, partitions, or covers. The purpose
of this provision is to protect persons from coming in contact with
energized high-voltage conductors or parts when testing and
troubleshooting low- and medium-voltage circuits.
Several commenters expressed concern over this proposal. They
indicated that in order to comply with the proposed provisions,
existing high-voltage continuous mining machines would need to be
retrofitted with
[[Page 17531]]
additional interlocked barriers and partitions to separate low- and
medium-voltage from high-voltage components and circuits. One commenter
stated that it is not the location of components that is the risk, but
rather the access to energized high-voltage components. The commenter
further stated that barriers, partitions, or the enclosure itself can
prevent access. The primary purpose of proposed paragraph (a) is to
prevent access to energized high-voltage components and circuits. In
the final rule, MSHA has revised the proposal to clarify its intent to
assure that existing equipment would not need retrofitting. The final
rule permits high-voltage and low- and medium-voltage components and
circuits in the same compartments if barriers are provided and covers
are arranged so that testing and troubleshooting can be performed
without exposing persons to any high-voltage conductors or parts. This
change allows for flexibility in design and does not reduce safety for
miners.
Final paragraph (a), like the proposal, requires barriers and
partitions to be constructed of grounded metal or nonconductive
insulating board.
One commenter expressed a preference for using barriers made of
insulating boards rather than grounded metal, but stated that either is
acceptable. MSHA agrees that use of either material would meet the
requirements of final paragraph (a).
Final paragraph (b) requires that each removable cover, barrier, or
partition of a motor-starter enclosure that provides access to high-
voltage components be provided with at least two interlock switches
that automatically de-energize the high-voltage components when the
cover, barrier, or partition is removed.
A commenter expressed concern with the proposed requirement for
interlock switches on all barriers, partitions, and covers. The
commenter requested that MSHA not require interlock switches except
when the cover, barrier, or partition provides access to energized
high-voltage circuits or parts.
MSHA did not intend to require interlock switches on all barriers,
partitions, and covers and has clarified the language in the final rule
to require interlock switches only when there is direct access to high-
voltage circuits. Interlock switches protect miners from shock hazards
by de-energizing high-voltage circuits when barriers, partitions, or
covers are removed.
Final paragraph (c), like the proposal, requires that circuit-
interrupting devices be designed and installed to prevent automatic re-
closure to protect miners from electrical shocks, fires, explosions,
and unintentional machine movement. For example, a roof-collapse or
equipment insulation failure can result in short-circuit or ground-
fault condition. This could result in the automatic re-closing of the
circuit-interrupting device and pose a hazard to miners. MSHA received
no comments on this proposal.
Final paragraph (d), like the proposal, includes requirements for
the grounding of the electrostatic shield for high-voltage transformers
supplying control voltages on continuous mining machines.
Final paragraph (d)(1), like the proposal, requires that the
nominal control voltage not exceed 120 volts line-to-line. Limiting the
control voltages to 120 volts line-to-line reduces the potential for
electrocution of miners. This provision is consistent with granted
PFMs. MSHA received no comments on this proposal.
Final paragraph (d)(2), like the proposal, requires that control
transformers with high-voltage primary windings in each high-voltage
motor-starter enclosure, or that supply control power to multiple
motor-starter enclosures, have an electrostatic (Faraday) shield
installed between the primary and secondary windings. The purpose of
the electrostatic shield is to isolate the high-voltage from lower-
voltage circuit. This protects miners from high-voltage shocks should a
fault develop between the primary and secondary windings. Electrostatic
shielding also prevents transients (sudden short-term changes in
voltage and current) occurring on the primary circuit from being
transferred to the secondary circuit. These transients can damage
equipment and create the risk of a fire and electrical shock.
Final paragraphs (d)(2)(i) and (d)(2)(ii) address requirements for
grounding the electrostatic shield. If the transformer has an external
grounding terminal, paragraph (d)(2)(i) requires the shield to be
connected from the grounding terminal to the equipment ground by a
minimum of a No. 12 American Wire Gauge (A.W.G.) grounding conductor.
This requirement will assure proper current carrying capacity and
mechanical strength of the grounding conductor.
If the transformer does not have an external terminal, paragraph
(d)(2)(ii) requires that the electrostatic shield be connected to the
transformer frame by an internal conductor. This conductor, generally
installed when the transformer is manufactured, is considered an
extension of the shield and therefore may be smaller than a No. 12
A.W.G. In this case, bolting the transformer frame to the equipment
enclosure will provide the required path to ground, as long as an
effective low impedance electrical connection is maintained. MSHA
received no comments on these proposals.
Final paragraph (e), like the proposal, addresses requirements for
indicator light circuits. Final paragraph (e)(1) requires a grounded-
phase indicator light on any ungrounded, three-phase power circuit
onboard the machine to alert the machine operator when a grounded-phase
condition occurs. Ungrounded circuits include high-voltage transformers
that power low- and medium-voltage circuits. The secondary windings of
these transformers are connected in an ungrounded configuration. With
ungrounded systems, the capacitive coupling between each phase
conductor and ground can subject the ungrounded system to dangerous
over-voltages resulting from intermittent ground faults. If a second
phase is grounded, a short-circuit condition will occur and cause
arcing between components. This could result in a methane-air
explosion, cause failure of the enclosure, and expose miners to
electrical shock. MSHA received a number of comments on this proposal.
Some commenters stated that a grounded phase indicator light should
be required on all high-voltage continuous mining machines. MSHA does
not agree. This requirement is unnecessary when the three-phase power
circuits onboard are grounded because the circuits are protected with
ground-fault devices that automatically trip the circuit breaker at the
power center. Currently, all 2,400-volt continuous mining machines have
grounded-phase indicator light circuits because they have ungrounded
power circuits onboard.
Several commenters stated that lower voltage continuous mining
machines and high-voltage shearing machines are not required to have a
grounded-phase indicator light circuit and have operated many years
without incident. They further stated that grounded-phase indictor
light circuits are unnecessary and create a shock hazard for those who
perform maintenance on the machine.
In response, MSHA notes that lower voltage continuous mining
machines and high-voltage shearing machines are designed differently
from high-voltage continuous mining machines. Explosion-proof
enclosures onboard low- and medium-voltage continuous mining machines
and explosion-proof enclosures for high-voltage shearing machines are
designed and tested to withstand arcing faults within the enclosure. On
a high-voltage continuous
[[Page 17532]]
mining machine, however, only explosion-proof enclosures containing
high-voltage switchgear are designed and tested to withstand internal
arc faults. High-voltage continuous mining machines also have
explosion-proof enclosures that do not contain high-voltage switchgear.
These enclosures are not designed and tested to withstand high-energy
arcing faults. Therefore, to prevent ignition hazards, the final rule
requires indicator light circuits to assure that arcing does not occur
and injure miners. Additionally, maintenance personnel are not exposed
to shock hazards if they follow the troubleshooting and testing
procedures specified in this final rule. MSHA believes that a greater
hazard exists when a grounded-phase condition goes undetected.
Final paragraph (e)(2), like the proposal, requires that the
indicator light be installed so that the machine operator can readily
observe it from any location where the continuous mining machine is
normally operated. MSHA received no comments on this proposal.
Final paragraph (e)(3), like the proposal, requires that the
onboard ungrounded, three-phase power circuit have a test circuit for
the grounded-phase indicator light circuit. It also requires that the
test circuit be designed so that it can be activated without removing
any enclosure covers and without creating a double-phase-to-ground
fault. This requirement will assure proper operation of the indicator
light circuit and that personnel conducting the test are not exposed to
any hazard. MSHA received no comments on this proposal.
Final paragraph (f) addresses the current carrying capacity,
outside diameter, and the physical properties of high-voltage trailing
cables. Unlike the proposal, the final rule does not incorporate by
reference the Insulated Cable Engineer's Standards (ICEA) S-75-381/
National Electrical Manufacturer's Association (NEMA) Standard, NEMA WC
58-1997, but rather includes a table for the outside diameters and
ampacity ratings for high-voltage trailing cables. This table is
referenced as Table 10 in Appendix I of 30 CFR Part 18, and is
consistent with tables contained in the ICEA S-75-381/NEMA WC 58-1997.
The purpose of the table is to standardize the ampacity and outer
diameter of cables to ensure the interchangeability of trailing cables
provided by different manufacturers.
A commenter expressed concern that proposed paragraph (f) did not
specifically limit trailing cable length. Existing Sec. 18.35(a)(5)
specifies the maximum allowable lengths for trailing cables used to
conduct electrical energy to production equipment, including continuous
mining machines. For this reason, the Agency does not believe that it
needs to limit trailing cable length in this provision.
Final paragraph (f)(1), like the proposal, requires that trailing
cables be constructed to include 100 percent semi-conductive tape
shielding over each insulated power conductor. Final paragraph (f)(2)
requires a grounded metallic braid shielding over each power conductor.
The combination of semi-conductive tape and grounded metallic shielding
around each power conductor provides symmetrical distribution of
voltage stresses on the conductor insulation. Shielding also prevents
transients on power systems. These provisions protect miners from shock
and electrocution. MSHA received no comments on these proposals.
Final paragraph (f)(3) requires that the cable include either a
ground-check conductor not smaller than a No. 10 A.W.G., or a center
ground-check conductor not smaller than a No. 16 A.W.G. stranded
conductor. The term ``stranded'' has been added in the final rule to
describe the No. 16 A.W.G. ground-check conductor for accuracy. The
ground-check conductor is either located in the outer interstice of a
trailing cable along with the grounding conductors or in the center of
the trailing cable. Cables designed with a No. 16 A.W.G. center ground-
check conductor have been successfully used in high-voltage longwall
applications for several years.
A commenter indicated that the reference in the proposed preamble
to the No. 16 A.W.G. ``stranded'' conductor describing the center
ground-check conductor is technically incorrect, and suggested
``special annular stranded with extensibility.'' MSHA does not agree.
Cable manufacturers and ICEA/NEMA standards reference the center
ground-check conductor as ``stranded.'' The terminology suggested by
the commenter is a description of the quality of the No. 16 A.W.G.
ground-check conductor and is consistent with the cable designs
specified in the ICEA/NEMA standard.
Final paragraph (f)(4), like the re-proposal, addresses the design
and construction of high-voltage trailing cable jackets. MSHA received
several comments on the proposal.
Some commenters suggested that the final rule allow single-jacketed
cables made of thermoplastic polyurethane (TPU) because of its high
tensile strength and resistance to abrasion and tear. A commenter
stated that the minimum tensile strengths for the single-jacketed and
double-jacketed cables are 5,000 and 2,400 pounds per square inch,
respectively; and tear strengths are 120 and 40 pounds per inch,
respectively. The commenter also stated that the TPU material can be
made in a color other than black, that TPU-jacketed trailing cables
have been in use in the mining industry for 11 or 12 years, and that
they have been used successfully on mining equipment such as shearing
machines and medium-voltage continuous mining machines.
Others stated that at least one granted PFM permitted the use of a
TPU jacket as an alternative to the double-jacket requirement on two
high-voltage continuous mining machines and on shuttle cars for over
two years without any problems.
Based on the comments, MSHA re-proposed paragraph (f)(4) to allow
the option of using either a double-jacketed or a single-jacketed
cable. The final rule contains requirements for both types of trailing
cables.
Final paragraph (f)(4)(i) requires that a double-jacketed cable, if
used, consist of two reinforced layers of jacket material, with the
inner layer a distinctive color from the outer layer. It also requires
that black not be used for either layer. If used, a double-jacketed
cable must have tear strength of more than 40 pounds per inch thickness
and a tensile strength of more than 2,400 pounds per square inch.
Final paragraph (f)(4)(ii) specifies the requirements for a single-
jacketed cable. If used, a single-jacketed cable must have tear
strength of more than 100 pounds per inch thickness and a tensile
strength of more than 4,000 pounds per square inch, and not be black in
color. The final rule specifies the minimum values for the tear and
tensile strength based on granted PFMs.
In the re-proposal, MSHA requested comments on the minimum tear and
tensile strength values for single-jacketed cables and received none.
Final paragraph (g), like the proposal, requires manufacturers to
provide safeguards against corona on all 4,160-volt circuits in
explosion-proof enclosures.
Corona is a luminous discharge that occurs around electric
conductors that are subject to high electric stresses. Corona can cause
premature breakdown of insulating materials in explosion-proof
enclosures onboard the high-voltage continuous mining machine. This
poses the risk of arcing and may result in explosion. Although corona
usually does not present a hazard until a voltage of 8,000 volts is
reached, safeguards should be taken at 4,160
[[Page 17533]]
volts, the maximum voltage permitted under Part 18. Safeguards 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. MSHA received no comments on this
proposal.
Final paragraph (h), like the proposal, 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. The requirement protects miners against explosion
hazards that may arise from the effects of sustained high-voltage
arcing faults. Arcing faults may significantly contribute to a pressure
rise in an explosion-proof enclosure during an internal methane-air
explosion. A pressure rise above the design limit of the enclosure can
cause the explosion-proof enclosure to fail to contain the methane
explosion. MSHA received no comments on the proposal.
Final paragraph (i), like the proposal, prohibits high-voltage
electrical components located in explosion-proof enclosures from being
coplanar with a single-plane flame-arresting path. This provision
prevents the heat or flame from an arc or methane explosion in an
explosion-proof enclosure from igniting a methane-air mixture
surrounding the enclosure by preventing conductor material particles
from being expelled through the flame-arresting path. The possibility
of this occurring with multi-plane flame-arresting path surfaces is
non-existent because deflecting the path prevents ignitions by expelled
particles. MSHA received no comments on this proposal.
Final paragraph (j), like the proposal, requires that rigid
insulation between high-voltage terminals (phase-to-phase or phase-to-
ground) be designed with creepage distances in accordance with the
table specified in this section. The distances in the table provide
adequate isolation to prevent a phase-to-phase or phase-to-ground fault
that could cause a possible explosion. The required creepage distances
are based on the phase-to-phase use voltage and the Comparative
Tracking Index (CTI) of the insulation used. 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 creepage distances in the table are
consistent with most commercially available high-voltage components to
which this provision applies. MSHA received no comments on the
proposal.
Final paragraph (k), like the proposal, specifies minimum free
distances (MFDs) in motor-starter enclosures. If the MFDs are below the
values specified in the table, the enclosure could fail and cause an
explosion. MFDs are distances between the wall or cover of an enclosure
and uninsulated electrical conductors inside the enclosure. These MFDs
are established to prevent wall or cover damage that might result from
arcing.
Final paragraph (k)(1), like the proposal, requires that values not
specified in the table be calculated using a specific engineering
formula. This formula is based on existing longwall requirements. Final
paragraph (k)(2) requires that the MFD be increased by 1.5 inches for
4,160-volt systems and by 0.7 inches for 2,400-volt systems when the
adjacent wall area is the top of the enclosure. This increase in
distance is necessary to account for the thermal effects of arcing due
to heat rising within the enclosure. Final paragraph (k)(2) also
addresses the use of a steel shield in conjunction with an aluminum
wall or cover. Under these circumstances, the thickness of the steel
shield is used to determine the MFD. MSHA received no comments on the
proposal.
Final paragraph (l), like the proposal, addresses static pressure
testing of explosion-proof enclosures containing high-voltage
switchgear. Final paragraph (l)(1) requires that, prior to performing
the explosion tests, a static pressure test be performed on each
prototype design of an explosion-proof enclosure housing high-voltage
switchgear. It also establishes the static pressure testing and
performance requirements for explosion-proof enclosures housing the
high-voltage switchgear.
Final paragraph (l)(2) requires that every explosion-proof
enclosure containing high-voltage switchgear manufactured after the
prototype was tested undergo a static pressure test or follow an MSHA-
accepted quality assurance procedure covering inspection of the
enclosure. MSHA received no comments on this proposal.
B. Part 75--Mandatory Safety Standards--Underground Coal Mines
Section 75.823 High-Voltage Continuous Mining Machines; Scope
Final Sec. 75.823 describes the scope of this standard. The
standard addresses requirements for use of high-voltage continuous
mining machines of up to 2,400 volts in underground coal mines. Final
Sec. 75.823 also defines the term ``qualified person'' to mean a
person meeting the requirements specified in existing Sec. 75.153.
MSHA received no specific comments on this proposal. However,
several comments relating to machine voltage are relevant here. One
commenter agreed with the proposed rule which would have allowed
machines to operate at 4,160-volts. Other commenters opposed allowing
the voltage to exceed 2,400-volts, the limit in granted PFMs. They
stated that the industry has no experience with 4,160-volt continuous
mining machines and that these machines are more dangerous than 2,400-
volt machines.
The final rule limits the voltage of the continuous mining machines
to 2,400 volts because of the Agency's lack of experience with 4,160-
volt continuous mining machines in coal mines. Part 18, however, allows
for approval of equipment up to 4,160 volts. Mine operators seeking
MSHA approval to use 4,160-volt continuous mining machines would have
to file a petition for modification.
Section 75.824 Electrical Protection
Final Sec. 75.824 establishes the electrical protection
requirements for high-voltage continuous mining machines. Effective
electrical protection reduces the likelihood of ignitions, fires, and
electrical shocks. With the exception of (a)(2)(ii), this section is
based on granted PFMs. This section of the final rule is the same as
the proposed rule except that non-substantive changes have been made
for clarity.
Final paragraph (a) requires the use of an adequate circuit-
interrupting device capable of providing short-circuit, overload,
ground-fault, and under-voltage protection. The purpose of a circuit-
interrupting device is to interrupt the circuit in which it is used
without damage to itself when subjected to the maximum voltage and
current of the system. Short-circuit and overload protection prevent
damage to cables and motors that can result from arcing and
overheating. Ground-fault protection minimizes the risk of shock and
electrocution. Under-voltage protection prevents the unintentional
movement of equipment which can place miners at risk when power is lost
and then restored.
Final paragraph (a)(1)(i) specifies the current setting for a
short-circuit protective device. The device is required to be set at
the lower of: (1) The setting specified in the approval documentation,
or (2) 75 percent of the minimum available phase-to-phase
[[Page 17534]]
short-circuit current at the continuous mining machine.
The approval documentation specifies the maximum allowable setting
of the breaker required to protect the trailing cable. This setting
takes into consideration the cable size and length, and the motor
starting current. If 75 percent of the minimum available short-circuit
current is less than the setting specified in the approval, the breaker
setting will be based on that amount.
One commenter suggested that MSHA eliminate the phrase ``whichever
is less'' from the rule to allow the design of systems that could
utilize smaller cables and reduce injuries from handling cables. MSHA
does not agree with this commenter. If the size of the trailing cable
used is different than the cable size specified in the approval
documentation, the machine would not be permissible. Furthermore,
eliminating the words ``whichever is less,'' would allow the mine
operator to set the circuit-interrupting device at a value that may
cause it not to trip. For example, if the mine operator chooses to set
the circuit-interrupting device at 1,200 amps as required in the
approval, and 75 percent of the minimum available short-circuit current
is only 750 amps, the circuit-interrupting device would not trip.
Final paragraph (a)(1)(ii) revises the proposed rule to allow the
short-circuit device protecting the trailing cable to have an
intentional time delay not exceeding 0.050 seconds. The purpose of
permitting a time delay is to eliminate nuisance tripping during motor
starting.
Proposed paragraph (a)(1)(ii) required that the time delay not
exceed the setting specified in the approval documentation or 0.050
seconds, whichever is less. After further review, MSHA found that the
approval documentation does not specify a time delay. No comments were
received on this proposal.
Final paragraph (a)(2) establishes requirements for ground-fault
protection.
Final paragraph (a)(2)(i) requires a neutral grounding resistor to
limit ground-fault currents to not more than 0.5 amps. Neutral
grounding resistors are used in resistance grounded systems to limit
the level of ground-fault current in a circuit. The use of a 0.5 amps
neutral grounding resistor in conjunction with the ground-fault device
specified in final paragraph (a)(2)(ii) will provide additional
protection to miners from shock and fire hazards. MSHA received no
comments on this proposal.
Final paragraph (a)(2)(ii) requires that the circuit extending to
the continuous mining machine be protected by a ground-fault device set
at not more than 0.125 amps. The provision also allows a maximum time
delay of up to 0.050 seconds. The 0.125-amps limit is based on MSHA's
experience and knowledge that sensitive ground-fault devices are
commercially available and have been successfully used to detect
ground-fault currents. The ground-fault device would have to operate
within 0.050 seconds when exposed to 0.125 amps or more. MSHA received
no comments on this proposal.
Final paragraph (a)(2)(iii) requires a look-ahead circuit to detect
a ground-fault condition and prevent the closing of a circuit-
interrupting device when the ground-fault exists in a circuit.
Detection of the ground-fault condition prior to energizing the circuit
will protect miners from the risk of electrical shock. Additionally,
the final rule incorporates the best practice to prevent the circuit-
interrupting device from repeatedly closing when a ground-fault
condition exists because that could create a second ground-fault which
would result in a short-circuit condition. MSHA received no comments on
this proposal.
Final paragraph (a)(2)(iv) requires a backup ground-fault device to
detect an open neutral grounding resistor under a ground-fault
condition. This device will provide additional protection. Once an open
neutral grounding resistor is detected, the backup device will cause
the circuit-interrupting device to de-energize that circuit at 40
percent of the voltage developed across the resistor. This value
provides a safety factor. Additionally, this provision allows the
backup device to have a maximum time-delay setting of 0.250 seconds.
The time-delay setting is low enough to assure quick de-energization of
the circuit when the neutral resistor opens and a ground-fault exists,
while also allowing for selective tripping with the ground-fault
protective device in final paragraph (a)(2)(ii).
One commenter had several concerns about this provision. The
commenter stated that there were numerous problems with the potential
transformer and voltage relay monitoring method as a backup device,
which was used in MSHA's example. The commenter stated that potential
transformers are not able to detect rectified faults because of
ferroresonance. The potential transformer and voltage relay monitoring
method has been widely used in the industry and MSHA is not aware of
any problems associated with it. It is important to note that the
proposal did not require the use of a particular backup device to
detect an open neutral grounding resistor. Although MSHA listed this
method as an example of a backup device in the proposal as one means of
compliance, the Agency noted that other alternatives were acceptable.
The commenter also expressed concern that the proposal did not
include a requirement for detecting a shorted resistor. The commenter
stated that a shorted grounding resistor will not limit the voltage on
the frame of portable equipment to 100 volts or less. The purpose of
requiring a backup device is to detect a ground-fault condition when
the neutral grounding resistor is open. The commenter's recommendation
is not necessary because the ground-fault protection required in final
paragraph (a)(2)(ii) will detect that condition and de-energize the
circuit.
This commenter also suggested that the proposal be changed to
require de-energization of the circuit within a certain time if the
neutral grounding resistor opens, such as within 30 to 60 seconds. MSHA
is not aware of any device that monitors a shorted neutral grounding
resistor, nor does the Agency see the need for such a device. For the
reasons stated above, no changes have been made to this section, and
the final rule is the same as the proposal.
Final paragraph (a)(2)(v), like the proposal, requires a thermal
device to detect an overheated neutral grounding resistor caused by
sustained ground-fault current, and de-energize the incoming power.
This device provides an added safety measure for miners.
The rule also requires that the overtemperature rating or setting
of the device be the lower of: (1) 50 percent of the maximum
temperature rise of the neutral grounding resistor, or (2) 302 [deg]F
(150 [deg]C). Exposure of the neutral grounding resistor to sustained
ground-fault currents generates heat which can cause the resistor to
fail in the open mode. Failure of the resistor in an open mode will not
provide ground-fault protection and increases the risk of shock
hazards. The overtemperature setting requirement assures that the
affected circuit is quickly de-energized under a sustained fault.
MSHA's experience is that the temperature settings specified are high
enough to prevent nuisance tripping while providing safe operating
temperatures. Under the final rule, thermal protection must not be
dependent on control power. This requirement recognizes that the loss
of control power would prevent the operation of the detection device.
Thermal protection includes, but is not
[[Page 17535]]
limited to, current transformers and thermal relays, thermostats, and
other devices that sense overtemperature. MSHA did not receive any
comments on the proposal.
Final paragraph (a)(2)(vi), like the proposal, requires a single
window-type current transformer to encircle the three-phase conductors
to activate the ground-fault device required in final paragraph
(a)(2)(ii). It also prohibits the equipment grounding conductors from
passing through the current transformer as this defeats operation of
the ground-fault device and eliminates protection. Using the single-
window type current transformer in conjunction with a ground-fault
relay provides ground-fault protection for the circuit extending from
the power center to the continuous mining machine. MSHA received no
comments on this proposal.
Final paragraph (a)(2)(vii), like the proposal, requires a ground-
fault test circuit for each ground-fault device. This provision
requires that the test circuit inject no more than 50 percent of the
current rating of the neutral grounding resistor through the current
transformer. The purpose of the test circuit is to verify that a
ground-fault condition will cause the corresponding circuit-
interrupting device to open. MSHA received no comments on this
proposal.
Final paragraph (a)(3), like the proposal, requires that the under-
voltage device operate on a loss of voltage, de-energize the circuit,
and prevent the equipment from automatically restarting. This provision
is performance-oriented, which allows any under-voltage protective
device that will operate on loss of voltage and prevent the circuit-
interrupting device from automatically closing upon restoration of
power. This requirement will reduce pinning and crushing risks to
miners in case the equipment automatically restarts upon restoration of
power. MSHA received no comments on this proposal.
Final paragraph (b), like the proposal, prohibits use of circuit-
interrupting devices that automatically re-close after opening.
Automatic re-closure allows a circuit that has been de-energized to
become automatically re-energized. This provision will prevent
automatic re-closing under fault conditions. Typically, faults occur in
trailing cables due to damage from roof falls or when equipment runs
over the cables. If this occurs, the use of a circuit-interrupting
device designed to re-close automatically could present a risk of
electrical shock and fire. MSHA received no comments on this proposal.
Final paragraph (c) requires a mine operator to take certain
actions when a grounded-phase indicator light, if used, indicates a
grounded-phase condition. Detection of a grounded-phase condition will
reduce risks of electrical shock and arcing. The capacitive coupling
between each phase conductor and ground can subject an ungrounded
circuit to dangerous over-voltages from intermittent ground faults,
which in turn can lead to arcing and insulation failure. Arcing can
ignite methane and create a hazard to miners. Insulation failure can
lead to another phase-to-ground failure and create a shock hazard.
Final paragraphs (c)(1) and (c)(2) specify the actions to be taken
when a grounded-phase condition is indicated. Under paragraph (c)(1),
once the indicator light shows that a grounded-phase condition has
occurred, the machine must immediately be moved to an area where the
roof is supported. This will minimize miners' exposure to roof falls
while the equipment is being repaired. Final paragraph (c)(2) requires
that that the grounded-phase condition be located and corrected prior
to placing the machine back into operation. This requirement will
protect miners from risks of electrical shocks.
MSHA received a number of comments concerning the indicator light
circuit, and has addressed these comments in Sec. 18.54(e). Except for
minor editorial changes, the final provision is the same as the
proposed rule.
Section 75.825 Power Centers
Final Sec. 75.825 revises the proposal, and addresses the
requirements for power centers that supply high-voltage continuous
mining machines. The final rule includes provisions for disconnecting
switches and devices, barriers and covers, interlocks, emergency stop
switches, grounding sticks, and caution labels. These provisions reduce
risks of electrical shocks, fires, and explosions.
Final paragraph (a), like the proposal, requires a main
disconnecting switch in the power center that supplies power to the
high-voltage continuous mining machines. The main disconnecting switch,
when open, must de-energize the input power to all power transformers
in the power center. This will provide a safe means of de-energizing
high-voltage circuits in the power center without affecting the feed-
through circuits. MSHA received no comments on the proposal.
Final paragraph (b), like the proposal, requires a disconnecting
device for each circuit that powers a continuous mining machine.
Disconnecting devices in power centers de-energize the power to the
machine. Power must be de-energized prior to performing electrical
work.
MSHA received no comments on this provision. In the final rule,
MSHA has added clarifying language and defined ``disconnecting device''
as either a disconnecting switch or cable coupler.
Final paragraph (c), which was paragraph (c)(7) in the proposal,
addresses labeling, design, and installation requirements for
disconnecting switches specified in this final rule. This provision
requires that each switch be labeled to clearly identify the circuit
that it disconnects. MSHA's experience is that identifying the circuit
being de-energized by the switch assures that the proper circuit is de-
energized, which protects miners from exposure to electrical hazards.
The design and installation requirements are specified in paragraphs
(c)(1) through (c)(6) of the final rule.
Final paragraphs (c)(1) and (c)(2), like the proposal, require each
disconnecting switch to have voltage and current ratings compatible
with the circuits in which they are used. Improperly rated switches can
cause overheating and arcing and may create a shock or fire hazard for
miners. MSHA received no comments on these proposals.
Final paragraph (c)(3), like the proposal, requires that the
disconnecting switch be designed and installed so that one can visually
verify, without removing any covers, that the contacts of the device
are open. If miners had to remove the cover to verify that the contacts
are open, they could be exposed to energized high-voltage circuits and
electrical shock risks. MSHA received no comments on the proposal.
Final paragraph (c)(4), like the proposal, requires the
disconnecting switch to ground all power conductors on the ``load''
side when the switch is in the ``open and grounded'' position. It
assures the discharge of any voltage caused by capacitance between the
power conductors and ground. Grounding the circuit on the load side
reduces the risk of shocks to miners who are working on the trailing
cable or continuous mining machine. MSHA received no comments on the
proposal.
Final paragraph (c)(5), like the proposal, requires that each
disconnecting switch be designed so that it can only be locked when in
the ``open and grounded'' position. A disconnecting switch that locks
in the closed position could delay opening the switch during an
emergency. This provision, in conjunction with the
[[Page 17536]]
requirements of final Sec. 75.831, assures that the circuit will
remain de-energized until work is completed. MSHA received no comments
on the proposal.
Final paragraph (c)(6), like the proposal, requires that the
disconnecting switch safely interrupt the full-load current in the
circuit. A switch that is not capable of safely interrupting the full-
load current could result in its destruction and injuries to miners
from flash burns or flying parts.
The final rule provides an alternative if the switch is not
designed to interrupt the full-load current of the circuit. It requires
that the switch be designed to cause the circuit-interrupting device to
automatically de-energize the incoming power before the disconnecting
switch opens the circuit. MSHA received no comments on this provision
and the requirement of the final rule is identical to the proposed
rule.
Final paragraph (d) requires all compartments that provide access
to high-voltage conductors or parts to have barriers or covers to
prevent miners from coming into contact with energized circuits.
A commenter was concerned that the proposed rule would require that
both a cover and a barrier be installed. This was not MSHA's intent.
MSHA has revised the final rule to clarify that barriers or covers, or
both, can be used.
Final paragraph (e), like the proposal, addresses the interlocking
requirements between the control circuit and the main disconnecting
switch.
Final paragraph (e)(1) requires that the interlock allow the
control circuit to be energized through an auxiliary switch in the
``test'' position only when the main disconnecting switch is in the
``open and grounded'' position. When the main disconnecting switch is
in the ``open and grounded'' position, the power conductors on the load
side of the disconnecting switch are de-energized and grounded. The
interlocking feature assures that, before the auxiliary switch can be
placed in the ``test'' position, the main disconnecting switch is open
and grounded.
Final paragraph (e)(2), like the proposal, requires that when the
main disconnecting switch is ``closed,'' the control circuit can only
be powered through an auxiliary switch that is in the ``normal''
position. These requirements will prevent energization of the high-
voltage circuits during testing and troubleshooting. MSHA received no
comments on the proposed paragraph (e).
Final paragraph (f), like the proposal, was derived from granted
PFMs. It requires that each cover or removable barrier of any
compartment providing access to energized high-voltage conductors or
parts have at least two interlock switches for the purpose of de-
energizing exposed high-voltage conductors or parts when the cover or
barrier is removed. While the granted PFMs did not specify how many
interlock switches were required, the proposed rule required a minimum
of two interlock switches as an added safety measure to protect miners
against accidental contact with energized high-voltage circuits.
In the proposal, MSHA specifically requested comments on whether to
add an exception for troubleshooting control circuits. A commenter
suggested that each removable cover or barrier be interlocked to remove
all power in the compartment before entering it, except when testing
and troubleshooting control circuits. The commenter gave an example of
some power centers that are designed with a circuit breaker in a
separate incoming high-voltage compartment where the circuit breaker
will remove power in other compartments instead of removing the
incoming power.
MSHA believes that it is crucial to miners' safety that incoming
power be de-energized when miners remove covers prior to performing
electrical work. De-energizing incoming power rather than only the
power in the compartment being accessed assures that miners will not be
exposed to energized high-voltage circuits.
This commenter further suggested that MSHA require a single
interlock switch instead of the two switches required in the proposed
rule. The commenter stated that interlock switches expose miners to
hazards when they troubleshoot failed switches. As noted in the
proposal, MSHA has found that interlock switches might not operate
effectively after exposure to the mine environment. To protect miners
against accidental contact with energized high-voltage circuits, the
final rule, like the proposal, requires two interlock switches to
assure that at least one switch will function.
Another commenter stated that MSHA should not allow an exception
for troubleshooting control circuits in the high-voltage compartments.
MSHA believes that miners who troubleshoot and test energized circuits
in accordance with the provisions in this and other existing rules,
will be protected.
MSHA has considered comments and revised the proposal to allow
troubleshooting and testing energized circuits when the control circuit
is powered through an auxiliary switch in the ``test'' position.
Final paragraph (g), like the proposal, requires that an emergency
stop switch be located on the outside of the power center. The switch
will de-energize the incoming high-voltage if an emergency arises. This
provision also requires that the switch be hard-wired to a fail-safe
ground-wire monitor. In emergency situations, reliability of the stop-
switch is critical. MSHA received no comments on the proposal.
Final paragraph (h), like the proposal, requires that the power
center be equipped with a grounding stick to be used to discharge
capacitors and circuits before electrical work is performed. The
purpose of the grounding stick is to assure that all high-voltage
capacitors are discharged and that all circuits and components are de-
energized before electrical work is performed.
Capacitors are energy storage devices; they continue to be
energized even after the circuit is de-energized. Although some
capacitors are supplied with bleed-off resistors, these resistors can
open and the capacitor will continue to be energized. A disconnecting
switch blade may stick in the closed position with the switch in the
open position. If this happens, one or more phases of the circuit would
remain energized. Use of a grounding stick provides a last line of
defense to assure that the person performing electrical work will not
be exposed to energized high-voltage circuits.
Although there is no generally accepted definition, MSHA considers
a grounding stick to be a live line tool (hot stick) made of either
wood or fiberglass with a grounding attachment bonded to a No. \1/0\
A.W.G. copper grounding conductor. To safely discharge the capacitors
and parts, the grounding conductor would need to be permanently bonded
to the power center frame.
The final rule requires that the power center have a label that
identifies the location of the grounding stick to assure that the
person performing the electrical work can easily find it. The rule
requires that the grounding stick be stored in a dry location to
maintain its effectiveness.
A commenter suggested that MSHA allow alternatives to the grounding
stick to discharge capacitors or circuits. At this time, MSHA is not
aware of any alternatives to the grounding stick. This provision will
assure that energy storing components and circuits are discharged and
de-energized before miners come in contact with them.
Another commenter agreed with the grounding stick requirement,
stating that it will allow the safe discharge of stored energy and
assure that miners
[[Page 17537]]
will not be exposed to high-voltage circuits. This commenter suggested
that MSHA require steps to assure that energy stored in the cable after
it is disconnected is discharged. Final paragraph (c)(4) requires that
the disconnecting device ground all power conductors of the trailing
cable when the device is in the ``open and grounded'' position.
Therefore, MSHA has addressed this concern.
A third commenter stated that power centers that have a visual
disconnect should not be required to have a grounding stick. Although
the visual disconnecting device de-energizes the circuit it
disconnects, it does not discharge capacitors and other circuits.
Therefore, MSHA has not adopted the comment.
Based on comments, MSHA has clarified that the intent of the
grounding stick is to discharge capacitors and de-energize high-voltage
circuits.
Final paragraph (i), like the proposal, requires that all
compartments that provide access to energized high-voltage conductors
and parts display a caution label that warns miners against entering
the compartment before de-energizing the incoming high-voltage. The
label serves as a reminder to miners that the line side of a
disconnecting switch remains energized when the switch is opened unless
the incoming power to the switch is de-energized. The Agency did not
receive any comments on the proposal.
Section 75.826 High-Voltage Trailing Cables
Final Sec. 75.826, like the proposal, is derived from existing
Sec. Sec. 75.804 and 18.35 and specifies the requirements for high-
voltage trailing cables.
Final paragraph (a) requires that the high-voltage trailing cable
meet the design requirements of existing Sec. 18.35 and the approval
requirements of high-voltage continuous mining machines.
Final paragraph (b) allows two sizes of ground-check conductors
depending on the cable design. The first option allows the use of a
ground-check conductor not smaller than a No. 10 A.W.G. as required in
existing Sec. 75.804. This minimum size is required because the
ground-check conductor is located on the periphery of the cable and is
subjected to more flexing and bending, weakening the conductor and
resulting in possible breakage or damage. As an alternative, the cable
can have a ground-check conductor not smaller than the No. 16 A.W.G.
located in the center of the cable. This design does not subject the
ground-check conductor to the same stresses as the No. 10 A.W.G. when
the cable is flexed. The main advantage of this alternative is the
reduction of inter-machine arcing because the cable design will include
three grounding conductors placed symmetrically. This cable design has
been used successfully with high-voltage longwall equipment. It
eliminates the need to petition for modification of Sec. 75.804(a)
when the cable is designed with a center ground-check conductor smaller
than No. 10 A.W.G. but not smaller than a No. 16 A.W.G. No comments
were received on the proposed section.
Section 75.827 Guarding of Trailing Cables
Final Sec. 75.827 addresses requirements for guarding trailing
cables. It renumbers proposed Sec. 75.827(c) and (d) as final
paragraphs (a) and (b).
Proposed Sec. 75.827(a) would have required the high-voltage
trailing cable to be supported on insulators or placed in an unused
entry from the power center to the last open crosscut during advance
mining, to within 150 feet outby any pillar workings during second
mining, and to within 150 feet of the continuous mining machine when
used in outby areas.
Some commenters were concerned that supporting the cable on
insulators may subject shuttle or ram car operators to injuries if the
cable is supported at canopy height. They stated that in muddy
conditions, shuttle or ram cars could slide into the coal ribs and
cause the equipment to hit and damage the cable, exposing the equipment
operators to possible arc burns and electrical shock. They also stated
that by placing the cable on the floor, the machine tires and not the
canopy would hit the cable, and any resulting hazard would occur away
from the machine operator. Other commenters agreed with the proposed
language requiring that the cables be supported on insulators but
suggested that the cable be installed only when it is de-energized.
Others suggested that the cable be installed on insulators at a minimum
height of 6.5 feet and 7.5 feet.
Commenters stated that an unused entry may not always be available
to meet the proposed requirement to place the cable in an unused entry.
After evaluating the comments, MSHA agrees that suspending the cable
may be more of a hazard to miners than placing the cable on the mine
floor. MSHA also agrees that an unused entry may not always be
available. Therefore, the final rule does not contain the proposed
requirements that the cable must be supported or placed in an unused
entry.
Proposed Sec. 75.827(b) permitted the temporary storage of cables
on a sled or in a crosscut located between the power center and the
last open crosscut. It required these storage locations to be
barricaded and to have warning signs posted.
One commenter stated that in many cases, allowing temporary storage
of trailing cables at the locations in the proposal would encourage
storage of cables in mining sections, posing a safety threat to miners.
The commenter further stated that the proposal was not practical or
safe. In response to comments, the final rule does not contain the
requirement for temporary storage of cables.
One commenter stated that the requirements of Sec. 75.827 are
excessive because the cable leaving the power center is the safest
cable on the section and should not be required to meet additional
requirements. MSHA does not agree with this commenter because the cable
is still susceptible to damage by mobile equipment. Consequently,
guarding and protecting the cable from damage by mobile equipment are
important safety measures for the protection of miners.
Proposed Sec. 75.827(c), redesignated as final Sec. 75.827(a),
addresses guarding of the trailing cable. Final paragraph (a)(1)
specifies the locations where the high-voltage trailing cable must be
guarded. These locations are: (1) From the power center cable coupler
for a distance of 10 feet inby the power center; (2) from the entrance
gland for a distance of 10 feet outby the last strain clamp on the
continuous mining machine; and (3) any location where the cable could
be damaged by moving equipment. These are locations where miners are
likely to come in contact with the cable and where the cable could be
damaged. To be effectively guarded, the cable must be fully covered, so
that there is a physical barrier between the cables and miners. One
commenter suggested that the trailing cable be guarded for 10 feet inby
the power center. MSHA agrees that this is the location that miners are
most likely to come in contact with the cable. In response to comments,
the final rule requires that the cable be guarded for 10 feet inby the
power center. The proposed requirement for guarding the trailing cable
between the power center and the first cable insulator is not included
in the final rule since insulators are not required.
Final paragraph (a)(1)(ii) requires that the high-voltage trailing
cable be guarded from the entrance gland for a distance of 10 feet
outby the last strain clamp on the continuous mining machine. The
proposal required guarding for a ``minimum'' of 10 feet. Some
commenters suggested that this distance be increased from 10 feet to 35
feet or more. The proposal would have
[[Page 17538]]
allowed guarding for a distance of 35 feet or more. However, requiring
guarding for a distance longer than 10 feet, as suggested by the
commenters, would preclude detection of a damaged cable in the guarded
area because the final rule does not require removal of guarding when
inspecting the cable. The final rule does not contain the term minimum
and does not require guarding beyond 10 feet.
Final paragraph (a)(1)(iii), like the proposal, requires guarding
at any location where the cable could be damaged by moving equipment.
MSHA received no comments on this proposal.
Final paragraph (a)(2), like the proposal, requires that guarding
be constructed of nonconductive flame-resistant material, or grounded
metal. If a marking does not appear on the guarding to indicate that it
is flame-resistant, MSHA will request documentation to substantiate
that the material is flame-resistant. Metal and non-conductive guarding
may be of a continuous length or overlapping shorter pieces. Shorter
pieces of metal guarding must be bonded together to assure a continuous
metallic path. MSHA received no comments on this proposal.
Final paragraph (b) addresses requirements when equipment must
cross any portion of the cable. It allows two alternatives for
protecting the cable from mobile equipment: (1) Suspension of the cable
from the mine roof; or (2) the use of commercially available cable
crossovers. MSHA encourages mine operators to establish work practices
that minimize the need for cable crossovers, such as placing the cable
in locations where mobile equipment is not likely to travel.
Final paragraphs (b)(2)(i) through (b)(2)(vii), like the proposal,
specify minimum design requirements for cable crossovers. Cable
crossovers are commercially available and are used throughout the
industry to protect cables from mobile equipment damage. These minimum
design requirements will assure that the largest piece of equipment
used would be able to cross over the cable without damaging it. MSHA's
experience is that cable crossovers provide effective protection when
properly used. MSHA received no comments on the proposal. However, the
phrase ``in or inby the last open crosscut'' is not included in the
final rule and the requirement is not limited to any section of the
mine.
Section 75.828 Trailing Cable Pulling
Final Sec. 75.828 addresses procedures for pulling high-voltage
trailing cable with equipment other than the continuous mining machine.
In the proposal, Sec. 75.828 was titled ``Trailing Cable Handling
and Pulling''. Proposed Sec. 75.828(a), dealing with handling
energized cables, is renumbered Sec. 75.833(a) and addressed in the
discussion of that provision. Except for editorial changes, final Sec.
75.828 is identical to proposed Sec. 75.828(b). It requires that the
mine operator de-energize the high-voltage trailing cable and follow
manufacturer's procedures for pulling the cable. Cable manufacturers'
recommendations usually include: The proper application of a rope or
sling to pull the cable; minimum bending diameter; maximum length of
trailing cable that can be safely pulled; and the number of corners
that the cable can be pulled around. The purpose of this requirement is
to prevent damage to the cable while it is being pulled. For example,
when pulling a cable with ropes, if a loop smaller than the minimum
bending diameter for the size of the trailing cable is created, the
cable can be damaged.
One commenter suggested that this proposed requirement be
eliminated. Another stated that there was no safety benefit from
requiring the trailing cable to be de-energized since the high-voltage
trailing cable is significantly safer than other cables. These
necessary requirements are included in the final rule as it has been
MSHA's experience that pulling long lengths of cable around corners
with shuttle cars or scoops may cause the ropes or slings to penetrate
the cable and roll back the jacket, shielding, and insulation, thereby
exposing energized conductors. If these conditions occur while the
cable is energized, miners will be exposed to the risk of an electrical
shock. De-energizing the trailing cable prior to pulling will assure
that exposed conductors will not present shock hazards to miners.
Section 75.829 Tramming Continuous Mining Machines In and Out of the
Mine and From Section to Section
Final Sec. 75.829 addresses tramming continuous mining machines in
and out of the mine or from one section to another, and testing
required prior to tramming.
Final paragraph (a) revises the proposal for clarity and sets forth
procedures for tramming the continuous mining machine. It also requires
that the applicable power sources used to tram the machine not be moved
while energized as specified in existing Sec. 75.812.
Final paragraph (a)(1), like the proposal, requires that when
tramming the continuous mining machine the power source must not be
located where permissible equipment is required. This provision is
adapted from existing Sec. 75.500, which prohibits non-permissible
equipment from being used in specific areas of the mine. Typically,
power sources listed in Sec. 75.829(c) are not ``permissible'' and,
therefore, must not be used in areas where permissible equipment is
required. MSHA received no comments on this proposal.
Final paragraph (a)(2) prohibits the mining machine from being used
for mining while being trammed except when using a power source that is
appropriate for this activity. Typically, the power sources used to
tram the machine do not have the capacity to provide for mining or
cutting functions. If mining or cutting were attempted while the
machine was powered by sources other than a power center, overloading
and loss of power could occur.
Although MSHA received no comments on proposed Sec. 75.829(a)(2),
the final rule clarified the proposal by specifying when a power center
used for tramming is appropriate for mining and cutting.
Final paragraph (a)(3), like the proposal, requires that low-,
medium-, and high-voltage cables comply with the applicable provisions
dealing with flame resistance qualities and design requirements of low,
medium, and high voltages when using the power sources specified in
Sec. 75.829(c). MSHA received no comments on this proposal.
Final paragraph (a)(4), like the proposal, requires that the high-
voltage cable be mechanically secured onboard the continuous mining
machine. This requirement applies to the high-voltage portable
transformer specified in paragraph (c)(2) of this section. If the
trailing cable does not fit on the machine, a shorter length of cable
should be used to connect the diesel-generator output to the continuous
mining machine. The purpose of this requirement is to prevent anyone
from handling energized high-voltage cables and to minimize damage to
the cable while tramming the continuous mining machine. MSHA received
no comments on this proposal.
Final paragraph (b), like the proposal, requires specific tests to
be conducted prior to tramming. Final paragraph (b)(1) requires that
ground-fault and ground-wire monitor tests be performed by a qualified
person. The purpose of these tests is to assure proper operation of the
ground-fault and ground-wire monitor. It is not the Agency's intent
that these tests be performed after momentary or incidental stops
during the tramming process. The testing
[[Page 17539]]
requirements assure that these devices operate properly to protect
miners from electrical shocks. The final rule clarifies the meaning of
a functional test. This provision also requires that corrective actions
and recordkeeping resulting from these tests be performed in accordance
with Sec. Sec. 75.832(f) and (g) of this final rule.
The ground-fault test assures that the circuit will be de-energized
if a ground-fault condition exists. Most manufacturers of power centers
provide ground-fault test circuits so that the circuit can be tested
without creating an actual ground-fault condition, which would expose
miners to the risk of burns and shocks. The test will assure that the
ground-wire monitor will de-energize the circuit if the ground-check or
grounding circuit is opened. Manufacturers of ground-wire monitors
provide a built-in test switch for this purpose. When low- and medium-
voltage power sources are used, a ground-wire monitor is required in
accordance with Sec. 75.902. A ground-wire monitor is not required for
the high-voltage power sources because these power sources use external
bonding.
One commenter suggested that a record be made only of the
corrective actions and that such a record be kept on the machine with
the date, time, and initials of the qualified person when the work is
completed. MSHA's data and experience show that all records and
certifications of tests and repairs are valuable tools for both mine
operators and MSHA. Records and certifications can be used to determine
trends with respect to equipment failure and/or design problems. They
have also been useful sources of information during accident
investigations. Records are required to be kept on the surface because
they will be more readily accessible to mine personnel and inspectors.
Therefore, final Sec. 75.829(b)(1) retains the requirements of the
proposal.
Final paragraph (b)(2), like the proposal, requires that prior to
tramming the continuous mining machine, where applicable, a person
designated by the operator must activate the test circuit for the
grounded-phase detection circuit on the continuous mining machine. This
test is applicable only if a grounded-phase detection circuit is
required. The purpose of requiring this test is to assure that the
detection circuit will successfully detect a grounded-phase condition.
If the test indicates that the detection circuit is not functioning
properly, corrective action must be taken in accordance with Sec.
75.832(f) of the final rule. A record of this test is not required.
MSHA received no comments on this proposal.
Final paragraph (c) specifies the power sources, in addition to the
power center, that may be used when the mining machine is trammed.
Power sources specified in this section have been selected to minimize
the need to handle energized high-voltage cables. It also specifies the
requirements that different power sources, such as generators or
stationary power supplies found at belt drives, must meet. These
sources can provide: (1) Low or medium voltage to portable transformers
that are either mounted on or attached to the high-voltage continuous
mining machine; or (2) high-voltage power sources. The source is a
generator set that includes a low- or medium-voltage diesel-generator
and a step-up transformer that provides high voltage to the continuous
mining machine.
Final paragraph (c)(1), like the proposal, addresses the use of a
medium-voltage power source that supplies 995 volts to the continuous
mining machine. To use this type of power source, the machine circuitry
would need to be rewired to allow the 995-volt trailing cable to
energize the tram and hydraulic pump motor circuits. Figure 1 of the
standard illustrates a high-voltage continuous mining machine using a
995-volt power source. The 995 volts can be supplied by the mine's
power system or a low- or medium-voltage diesel-generator set. If a
low- or medium-voltage diesel-generator set is used as the power
source, the generator set may be moved while energized in accordance
with existing regulations. MSHA received no comments on the proposal.
Final paragraph (c)(1)(i), like the proposal, prohibits back-
feeding the continuous mining machine with medium voltage to energize
the high-voltage circuits. This provision will prevent the high-voltage
motors from being powered by medium-voltage sources that do not meet
necessary requirements. MSHA received no comments on this proposal.
Final paragraph (c)(1)(ii) requires compliance with all applicable
requirements for medium-voltage circuits in 30 CFR Part 75, such as
overcurrent, ground-fault, under-voltage, and ground-wire monitors.
MSHA received no comments on this proposal.
Proposed Sec. 75.829(c)(1)(iii) is not included in the final rule.
It would have prohibited moving the medium-voltage portable transformer
while energized. This section was initially included in the proposed
rule because it would not have been practical to move the energized
portable transformer and comply with 30 CFR 75.516, which requires the
power cable feeding the portable transformer to be supported on well-
insulated insulators. Additionally, if the portable transformer has a
high-voltage primary winding that provides a medium-voltage output for
tramming the continuous mining machine, the movement of the transformer
would be prohibited by Sec. 75.812, unless the conditions specified in
Sec. 75.812 are met. However, neither Sec. Sec. 75.516 nor 75.812
prohibit movement of this equipment.
Therefore, upon reconsideration, MSHA has decided not to include
the proposed provision in the final rule to avoid any conflict with
existing standards.
Final paragraph (c)(2) addresses the use of step-up transformers to
convert low or medium voltage to high voltage to power the continuous
mining machine. Figure 2 of the standard illustrates this
configuration. Unlike the proposal, the final rule does not include the
term ``onboard'' to allow for other step-up transformers. The term
``temporary,'' used in the proposed rule to define an ``onboard step-up
transformer,'' is not used in the final rule.
Final paragraph (c)(2)(i) requires that the trailing cable
supplying low- or medium-voltage to the step-up transformer meet the
applicable requirements of 30 CFR Part 75. For example, the trailing
cable must meet the overcurrent, ground-fault, and under-voltage
protection requirements for underground low- and medium-voltage
alternating current circuits (Subpart J). The term ``input'' describing
the trailing cable was removed, as unnecessary. This requirement
remains unchanged from the proposed rule.
Final paragraph (c)(2)(ii), like the proposal, requires that the
high-voltage circuit output of the step-up transformer supplying power
to the mining machine meet the applicable provisions of final Sec.
75.824.
Final paragraph (c)(2)(iii)(A) requires the step-up transformer to
be securely mounted on either the continuous mining machine or a sled/
cart connected to the machine. This will minimize vibration that can
lead to an internal ground fault or damage to the transformer. The
proposal would have required the step-up transformer to be securely
mounted onboard the continuous mining machine.
Some commenters suggested that MSHA allow the installation of the
transformer on a sled/cart connected by a tow-bar and in close
proximity to the continuous mining machine. MSHA agrees that this
alternative provides
[[Page 17540]]
effective protection and has revised the proposal accordingly.
Final paragraph (c)(2)(iii)(B), like the proposal, requires that
the frame of the transformer be bonded to the frame of the continuous
mining machine and the metallic shell of each cable coupler by a No. 1/
0 A.W.G. or larger conductor, and connected to the incoming ground
conductor of the trailing cable. These grounding requirements assure a
low impedance grounding path from the transformer to the outby power
source should a ground-fault condition occur. MSHA received no comments
on the proposal.
Final paragraph (c)(2)(iii)(C), like the proposal, requires that
each of the transformer enclosure covers be equipped with at least two
interlock switches and that an external emergency stop switch be
provided to de-energize the input power to the step-up transformer when
activated in emergency situations. MSHA received no comments on the
proposal and the final rule includes clarifying changes.
Proposed paragraph (c)(3) is not included in the final rule in
response to comments.
One commenter objected to addressing high-voltage diesel-powered
generators in the proposed rule, stating that the equipment was not
relevant to the rulemaking and should be dealt with in a separate
rulemaking. The commenter requested that MSHA conduct public hearings
on the issue and suggested that MSHA include these requirements in the
rulemaking on low- and medium-voltage diesel-powered electrical
generators if necessary. In response to comments, the final rule does
not include the high-voltage diesel generator option.
Section 75.830 Splicing and Repair of Trailing Cables
Final Sec. 75.830 defines and addresses requirements for splices
and repairs of trailing cables.
Final paragraph (a) is derived from granted PFMs and addresses
requirements for persons performing splices and repairs. It also
specifies the manner in which the trailing cable must be spliced or
repaired to assure that miners are not exposed to shock and burn
hazards.
Commenters stated that the proposal did not distinguish between a
splice and a repair, and suggested that MSHA define these terms. In
response, MSHA has defined the terms in final paragraphs (a)(1) and
(a)(2) based on existing Sec. 7.402 and granted PFMs.
Another commenter stated that MSHA should use the language from the
Program Policy Manual relating to the existing standard for temporary
splice of trailing cable (Sec. 75.603) to identify whether cable
damage requires a splice or repair. This existing standard is not
applicable here because the proposed rule addressed permanent cable
repairs. The final rule does not use temporary or permanent. It
requires the use of an MSHA-approved kit, which precludes the use of
temporary splices.
Final paragraph (a)(3)(i), like the proposal, requires that cable
splicing and repair be performed only by a qualified person who is
trained in cable splicing and repair of high-voltage cables. From
MSHA's experience, hands-on training provides effective training. These
requirements will assure that the individual performing cable splicing
and repair understands the construction of the cable, the purpose of
every component, and the hazards associated with failure to replace
each component with a component similar to the original.
Some commenters suggested that the proposal be revised to allow
splices to be made under the direction of a qualified person. MSHA has
not incorporated this suggestion because a qualified person has the
knowledge and experience to make an effective splice that will protect
miners from electrical shocks. MSHA is concerned that a person who is
not qualified may not have the knowledge, training, or experience to
perform splicing and repairs safely.
Final paragraph (a)(3)(ii), like the proposal, requires that
splicing and repairs be made in a workman-like manner. The quality of
workmanship is vital to maintaining the same level of protection to
miners as that provided by the original cable. MSHA received no
comments on the proposal.
Final paragraph (a)(3)(iii), like the proposal, requires that
splices and repairs of trailing cables meet the requirements of
existing Sec. 75.810. This existing standard requires that the spliced
or repaired cable be mechanically strong, provide the same flexibility
and conductivity as the original cable, be insulated and sealed to
exclude moisture, preserve the cable's flame-resistance quality, and
have good bonding to the outer jacket. MSHA received no comments on
this proposal.
Final paragraph (a)(3)(iv) revises proposed Sec. 75.830(b) by
deleting the reference to permanent cable repair and requires that the
trailing cable be repaired using an MSHA-approved splice kit that
contains specific instructions.
MSHA prohibited the use of a permanent tape-type splice in granted
PFMs. The final rule does not prohibit this type of splice. Tape-type
splices can be used to make an effective splice when proper procedures
are followed. MSHA did not allow them in granted PFMs because the
splice materials were often used improperly and allowed moisture to
enter the splice. Moisture degrades the insulation and ultimately
creates a risk of electrical shock. Instead of prohibiting all tape-
type splices, the final rule requires that all splices be made with an
MSHA-approved splice kit. The approved kits contain materials and
appropriate instructions on the proper methods for making a splice. The
kit includes tape that is self-vulcanizing so it will exclude moisture
when applied as instructed, thereby preventing the risk of electrical
shock.
MSHA received several comments concerning tape-type splices. Some
commenters suggested that only vulcanized splices be used because
moisture cannot be kept out of tape splices. These commenters stated
that although tape-type splices are good when first made, after
dragging the cable the tape splices become damaged. MSHA does not agree
that only vulcanized splices can be effective. If a splice is made in
accordance with the instructions included in the MSHA-approved high-
voltage splice kit, the splice should be effective and exclude
moisture.
Another commenter stated that electricians need more training on
cable splicing and repair because not everyone reads the instructions
provided in the kits. MSHA agrees and, in response, the final rule
includes a new requirement for specialized training for persons who
perform maintenance on high-voltage mining machines which includes the
cable.
Final Sec. 75.830(b) limits the number of splices in a certain
portion of the trailing cable. Final Sec. 75.830(b)(1), as in the
proposal, prohibits splicing of the high-voltage trailing cable within
35 feet of the continuous mining machine.
Some commenters suggested that splicing should be prohibited within
50 to 60 feet from the continuous mining machine. MSHA's experience
with low- and medium-voltage equipment is that the portion of the cable
within 35 feet of the continuous mining machine is subjected to more
strains, stresses, and cable handling than the rest of the cable. The
probability that a miner will be shocked by an inadequate splice is
greatest within this portion of the cable due to weakened and damaged
cable.
Several commenters stated that the number of splices should be
limited because cable splicing causes the resistance of the cable to go
up. MSHA asked commenters during public
[[Page 17541]]
hearings for suggestions on a reasonable limit for the number of
splices. No number was suggested. Final paragraph (b)(2) limits to four
(4) the splices in the portion of the trailing cable that extends from
the continuous mining machine outby for a distance of 300 feet. Granted
PFMs contained a 4-splice limitation. Based on Agency experience with
PFMs, the final rule includes this limit.
Section 75.831 Electrical Work; Troubleshooting and Testing
Final Sec. 75.831 includes requirements for performing electrical
work, including troubleshooting and testing. It contains editorial
changes for clarity.
Final paragraph (a) requires that prior to performing electrical
work, other than troubleshooting and testing, on the trailing cable or
continuous mining machine, a qualified person must de-energize the
trailing cable in accordance with either paragraph (a)(1) or (a)(2).
De-energization is usually accomplished by opening the circuit-
interrupting device. The qualified person must follow the required work
procedures to prevent inadvertent re-energization. These procedures are
important to assure that miners are not exposed to potential shock,
fire, or other hazards when performing electrical work.
Final paragraphs (a)(1) and (a)(2) specify the two lock-out and
tagging procedures. Depending on the power center design, a
disconnecting switch or a cable coupler (plug and receptacle) would be
used to lock-out and tag the trailing cable. Final paragraph (a)(1)
specifies work procedures if a disconnecting switch is used on the
output circuit of the power center supplying power to the continuous
mining machine. If a disconnecting switch is used, final paragraph
(a)(1)(i) requires the switch to be opened to provide visual evidence
that the output is de-energized, grounded, and locked out and tagged in
the open and grounded position. This allows the cable coupler plug to
remain connected to the power receptacle. No comments were received on
this proposal.
Final paragraph (a)(1)(ii), like the proposal, requires the plug
and receptacle to be locked together and tagged. This requirement will
assure that the cable coupler plug cannot be disconnected from the
receptacle and connected to a spare circuit. When this procedure is
used, connection to a grounding receptacle is unnecessary because
opening the disconnecting switch grounds the power conductors of the
high-voltage trailing cable.
MSHA understands that some mine operators prefer not to disconnect
high-voltage couplers since this may lead to problems when re-
energizing the circuit. The main problem with disconnecting high-
voltage couplers is the risk of contaminating the couplers' insulation
with dust. Using a disconnecting switch to ground and isolate power
from the trailing cable and continuous mining machine would eliminate
the need to remove the cable coupler plug from the receptacle.
One commenter suggested that the proposal be revised to allow other
means of locking-out and tagging, such as requiring all spare circuit
visual disconnects to be locked-out and tagged. This suggestion may
require the person performing the work to carry more keys and locks
because there may be more than one spare circuit and each must be
locked. Also, MSHA believes that most of the plugs and receptacles are
designed with means to lock them together.
Final paragraph (a)(2), like the proposal, addresses the use of a
cable coupler as a disconnecting device. After power has been removed,
final paragraph (a)(2)(i) requires the plug to be disconnected from the
receptacle and connected to a grounding receptacle. The grounding
receptacle, which is mounted on the power center, will cause all power
conductors of the cable to be grounded to the power center frame.
Connecting the plug to the grounding receptacle assures that no voltage
will be present in the cable conductors. MSHA received no comments on
this proposal.
Final paragraph (a)(2)(ii) requires the plug and grounding
receptacle to be locked together and tagged. Tagging will alert miners
that work is being done on the circuit, and the lock will prevent the
circuit from being re-energized and ungrounded while work is being
performed. These requirements will prevent shock hazards to miners
while performing electrical work. MSHA received no comments on this
proposal.
Final paragraph (a)(2)(iii) requires that a dust cover be placed
over the power receptacle to protect it from becoming contaminated by
dust when the trailing cable is disconnected. Dust is a conducting
medium and can create ground faults. The dust cover will also prevent
miners from contacting energized parts of the receptacle. MSHA received
no comments on this proposal.
Final paragraph (b) addresses all troubleshooting requirements. It
contains only minor clarifying changes from the proposal. It requires
that during troubleshooting and testing, the de-energized cable may be
disconnected from the grounding receptacle only for that period of time
necessary to locate the defective condition. Generally, when the cable
is disconnected from the power receptacle, it is connected to the
grounding receptacle. It also requires that prior to troubleshooting
and testing the trailing cable, a qualified person must follow one of
the lock-out and tagging procedures specified in paragraphs (b)(1) and
(b)(2). Following these procedures prevents inadvertent re-energization
of the circuits being tested and protects miners from shock, fire, or
other hazards.
Final paragraphs (b)(1) and (b)(2), like the proposal, address
lock-out and tagging procedures based on the design of the power
center. These procedures are the same as discussed in paragraph (a) of
this section.
One commenter suggested that since the high-voltage trailing cable
is not subject to accumulation of static charges, as in the case of a
surface high-voltage line which is subject to wind and other sources of
charge buildup, the Agency should not require constant grounding. MSHA
does not agree and, consistent with existing rules, the final rule
contains grounding requirements to assure the safety of personnel
performing electrical work on high-voltage circuits.
Final paragraph (c), re-numbered from proposed paragraph (d),
addresses limitations on troubleshooting and testing. It is derived
from granted PFMs and existing troubleshooting requirements for
longwalls. The final rule recognizes that it may be necessary for
circuits or equipment to remain energized for troubleshooting and
testing, such as when taking voltage and current readings to identify a
problem. It contains conditions under which this can be done.
Final paragraph (c)(1), like the proposal, limits troubleshooting
and testing of energized circuits to low- and medium-voltage systems
because troubleshooting and testing energized circuits is known to be
inherently hazardous work. Further, there are no adequate equipment and
insulation ratings for testing energized high-voltage circuits and
equipment. MSHA received no comments on this proposal.
Final paragraph (c)(2), like the proposal, permits troubleshooting
and testing of energized circuits only for the purpose of determining
voltages and currents, including evaluation of waveforms or other
electrical diagnostic testing. MSHA received no comments on this
proposal.
Final paragraph (c)(3), like the proposed (d)(3), requires that
troubleshooting and testing of energized circuits be performed only by
a qualified person. This requirement assures that the person conducting
the
[[Page 17542]]
testing is aware of the hazards associated with these tests. The
requirement for wearing properly rated gloves has been moved to final
paragraph (c)(4). MSHA received no comments on this proposal.
Final paragraph (c)(4) requires that the qualified person wear
protective gloves when the voltage of the circuit is 40 volts or more.
It also specifies the types of gloves to be used for different
voltages. Based on MSHA's experience and electrical accident data, the
Agency has concluded that 40 volts is the lowest voltage level that is
likely to cause electrocution. The final rule requires gloves to
protect miners who might inadvertently contact energized circuits
during troubleshooting and testing.
Dry work gloves or rubber insulating gloves with leather
protectors, in good condition, i.e., free of holes, etc., can be used
when troubleshooting 40-volt to 120-volt circuits nominal. Normally,
the nominal control voltage for mining equipment is 120 volts. If
miners are testing intrinsically safe circuits, dry gloves can be used
for circuits that exceed 120 volts nominal. When the circuit is not
intrinsically safe, rubber insulating gloves with leather protectors
rated for at least the nominal voltage of the circuit and equipment are
required to be used on circuits that exceed 120 volts nominal.
Typically, mining equipment is rated as 220, 480, 995 volts and higher.
Commercially available rubber insulating gloves are rated for 1,000
volts but are not rated for each of these voltages. Therefore, when
testing or troubleshooting low- and medium-voltage circuits, 1,000-volt
rated gloves must be used. MSHA received no comments on this proposal.
Final paragraph (d), re-numbered from proposed paragraph (e),
specifies the work procedures to be followed when performing electrical
work, other than troubleshooting and testing, in any compartment of the
power center. These procedures will assure that miners are not exposed
to potential shock, fire, or other hazards when performing electrical
work.
Final paragraph (d)(1), re-numbered from proposed (e)(1), requires
that affected circuits be de-energized in accordance with existing de-
energization requirements (see Sec. 75.509). MSHA received no comments
on the proposal.
Final paragraph (d)(2), re-numbered from proposed paragraphs (e)(2)
and (4), requires that a qualified person open the corresponding
disconnecting switch and lock it out and tag it to isolate the circuit.
MSHA received no comments on the proposal.
Final paragraph (d)(3), re-numbered from proposed (e)(3), requires
that a qualified person visually verify that the contacts of the
disconnecting switch are open and grounded. To verify, the qualified
person views the position of the contacts through a window. Opening the
disconnecting switch grounds the high-voltage conductors. Grounding the
conductors protects the miner working on a circuit from exposure to
energized high-voltage circuits which reduces the risk of electrical
shock and electrocution. MSHA received no comments on the proposal.
Final paragraph (d)(4), re-numbered from proposed paragraph (e)(5),
requires that all high-voltage capacitors and circuits in the power
center be discharged prior to performing electrical work. Because
capacitors are energy storage devices, they may continue to hold a
charge even after the disconnecting switch is opened and the circuit is
de-energized. Therefore, to assure that miners are not exposed to shock
hazards, capacitors and circuits must be discharged before performing
work. MSHA received no comments on the proposal.
Final paragraph (e), re-numbered from proposed paragraph (f),
requires that when more than one qualified person is working on the
same circuit or equipment, each person must install their own lock and
tag on the circuit or equipment on which work is being performed. It
also requires that each lock and tag be removed by the individual who
installed them. Limiting removal of the lock to the person who
installed it will prevent accidental re-energization of equipment or
circuits before all persons have completed their work.
MSHA's accident investigation experience reveals that failure to
lock out and tag circuits and equipment prior to performing maintenance
is the root cause of many accidents. This finding is supported in both
the National Safety Council's Data Sheet 237 Revision B, ``Methods of
Locking Out Electrical Switches'' (1971) and the National Fire
Protection Association's NFPA 70E ``Standard for Electrical Safety
Requirements for Employee Workplaces'' (2000 Edition). If persons are
required to place and remove their own locks, they will be more aware
of and responsible for their own safety as well as safety of others.
Following these procedures, miners will take the steps necessary to
assure proper de-energization. This requirement reduces the risk of
error due to lack of communication or inadvertent re-energization. MSHA
received no comments on this proposal.
Final paragraph (e)(2), like proposed paragraph (f)(2), includes
requirements for removing locks and tags. If the person who installed
the lock and tag is not available, the mine operator can authorize a
qualified person to remove that person's lock and tag. In this case,
the mine operator must notify the person who installed the lock and tag
that they have been removed. MSHA received no comments on this
proposal.
Section 75.832 Frequency of Examinations; Recordkeeping
Final Sec. 75.832 includes non-substantive editorial changes for
clarity. It specifies the frequency of testing certain equipment and
circuits, and the requirements for creating and maintaining adequate
records. Unlike granted PFMs that required some tests to be done
weekly, the final rule requires those tests to be conducted at least
every 7 days. Frequent examination and testing of the trailing cable
and the high-voltage continuous mining machine, as well as testing of
the ground-fault test circuit and ground-wire monitor circuit, is
necessary because moving this equipment increases the likelihood of
component failure and break down. MSHA's enforcement experience with
existing weekly examination and testing requirements indicates that the
actual frequency between examinations and tests is sometimes as long as
13 days. By changing the requirement to testing every 7 days, MSHA will
avoid prolonged periods between tests and examinations.
Final paragraph (a) requires that a qualified person examine the
high-voltage continuous mining machine at least once every 7 days to
verify that electrical protection, equipment grounding, permissibility,
cable insulation, and control devices are properly installed and
maintained. The purpose of the examination is to assure that the
equipment is operating safely. The examination will also advance
miners' safety and minimize their exposure to fire, electric shock,
ignition, or operational hazards.
Final paragraph (b) requires that, at least once every 7 days and
prior to tramming the machine, a qualified person activate the ground-
fault test circuit to verify that it will cause the corresponding
circuit-interrupting device to open. Activating the ground-fault test
circuit verifies that the ground-fault protection circuit is operating
properly. Failure of the ground-fault circuit to function properly when
a
[[Page 17543]]
ground fault exists would expose miners to shock hazards.
Final paragraph (c), like the proposal, requires that, at least
once every 7 days and prior to tramming the machine, a qualified person
test the ground-wire monitor circuit to verify that it will cause the
corresponding circuit-interrupting device to open. Testing of a ground-
wire monitor circuit normally requires activation of a test switch.
MSHA received a number of comments on this proposal. Some
commenters suggested that the 7-day examination requirement be changed
to a weekly examination. They stated that the 7-day requirement will be
confused with other electrical examinations performed on a weekly or
monthly basis and recommended that, for consistency purposes, testing
should be done on a weekly basis. Other commenters supported the 7-day
requirement, stating that the weekly requirement can provide a gap of
13 days between tests. MSHA agrees and the final rule includes the 7-
day requirement for testing and examination.
Final paragraph (d) addresses inspection of the high-voltage
trailing cable.
Final paragraph (d)(1) requires that once each day, during the
shift that the continuous mining machine is first energized, a
qualified person de-energize and inspect the entire length of cable
from the power center to the machine. This inspection must include all
areas of the cable where guarding is required, the outer jacket
repairs, and splices for damage or deterioration. The cable inspection
does not require removal of the guarding but rather, requires assuring
that the guarding is provided where required. In response to comments,
MSHA has replaced production day that was in the proposal with the more
clarifying phrase ``during the shift that the continuous mining machine
is first energized''.
Final paragraph (d)(2) requires that at the beginning of each shift
that the continuous mining machine is energized, a person designated by
the mine operator de-energize and visually inspect the high-voltage
trailing cable from the mining machine: (1) To the last open crosscut;
(2) to within 150 feet of the working place during retreat or second
mining; or (3) up to 150 feet of the machine when it is used in outby
areas for cutting overcasts, underpasses, sumps, etc. The inspection
must include an examination of the outer jacket of the cable for
damage. The specified locations are areas where the trailing cable is
most likely to be damaged by mobile equipment. Visual inspection will
assure the integrity of the cable and increase miners' safety.
MSHA received a number of comments on the proposed provisions
relating to trailing cable inspections. One commenter suggested that
the proposed requirements be deleted due to the superior design and
construction of high-voltage trailing cables. Although MSHA agrees that
the high-voltage trailing cable design and construction is superior to
low- and medium-voltage cable designs, the Agency continues to believe
that the requirements in the final rule are necessary to assure
integrity of the cable while in use.
Others recommended changing the proposal from each production shift
to each shift. They stated that such a change would be necessary in
order to include idle shifts during which equipment is moved for
section setup and maintenance. Another commenter suggested that MSHA
change the proposal to allow for hot seat change-outs. Some commenters
disagreed with this suggestion because this change would allow
inspections to be made at the end of the shift and could result in a
damaged cable remaining undetected for eight hours.
MSHA agrees with the suggestion to inspect the cable at the
beginning of each shift the machine is energized, which would include
idle shifts. MSHA believes that it is important to examine the trailing
cable in all shifts where the machine is energized to detect any damage
and has revised the proposal accordingly.
Another commenter objected to the proposed provision requiring the
high-voltage trailing cable to be de-energized, suggesting instead that
the miner wear high-voltage gloves when handling the energized cable.
MSHA does not agree because when visually examining the high-voltage
trailing cable, the miner may need to handle, move, or bend the cable.
Handling, moving, or bending a damaged energized cable can result in an
internal short-circuit and subsequent arc-flash injuries to the miner.
Using high-voltage gloves to handle a damaged energized cable would not
protect miners from arc-flash injuries. Therefore, it is necessary to
de-energize the cable prior to the examination.
Final paragraph (e), like the proposal, is derived from granted
PFMs and requires that at the beginning of each production shift, a
person designated by the operator must test the grounded-phase
detection circuit on the high-voltage continuous mining machine. This
provision will assure that the detection circuit functions properly and
that it will detect a grounded-phase condition. If the detection
circuit is defective, a grounded-phase condition will remain undetected
and miners will be exposed to the risk of electrical shock. MSHA
received no comments on the proposal.
Final paragraph (f), like the proposal, requires equipment to be
removed from service or repaired when any examinations or tests reveal
damage that could lead to a risk of fire, electric shock, ignition, or
operational hazard. This provision will assure that equipment that may
pose a danger to miners is not used until the hazardous condition is
corrected. For example, if examination of a trailing cable reveals an
exposed conductor, miners would be at risk of potential fire,
electrical shock, and methane gas ignition when the cable is energized.
MSHA received no comments on this proposal.
Final paragraph (g) specifies the recordkeeping requirements for
the examinations and tests in the final rule and is consistent with
existing recordkeeping requirements. Records and certifications of
tests and repairs are valuable tools for mine operators. Records and
certifications are used by MSHA to identify trends in equipment failure
and design problems so that the Agency can disseminate necessary best
practice information to the mining community.
Final paragraph (g)(1)(i), like the proposal, requires that the
person who examines and tests the equipment certify by signature and
date that the tests and examinations have been conducted. Only the
person conducting the examinations and tests can provide the
certification because that person would have direct knowledge of the
test results.
Final paragraph (g)(1)(ii) requires that a record be kept of any
unsafe conditions found by the individual who conducted the tests
because that person would have direct knowledge of the unsafe
conditions. Unlike the proposal, which did not identify who must record
corrective action, final paragraph (g)(2) specifies that the individual
who takes any corrective action must be the one to record that action.
The clarification is important because the person conducting the tests
may not be the one who takes the corrective action.
Final paragraphs (g)(3) and (g)(4) are new provisions added in
response to comments. Final paragraph (g)(3) requires that records must
be countersigned by the mine foreman or equivalent mine official by the
end of their next regularly scheduled working shift. Final paragraph
(g)(4) requires that records be maintained either in a secure book that
is not susceptible to alteration or electronically in a computer system
[[Page 17544]]
that is also secure and not susceptible to alteration.
Some commenters suggested that mine management share the
responsibility of assuring that records are properly documented and
stored. In so doing, these commenters raised the fact that the proposal
did not require records to be countersigned and that they have made
this suggestion on several occasions during previous rulemakings. MSHA
has re-evaluated this issue. In the preamble to the proposed rule, MSHA
stated that the Agency accepts certification only from the person who
examines and tests the equipment because that person will have
knowledge of the results of the examination and tests. MSHA
reconsidered its position and the final rule requires countersigning of
records by a foreman or equivalent. In making this change, the Agency
determined that countersigning of records by a foreman or equivalent
will help to assure accuracy of the records. Additionally, as mentioned
earlier, records are an important tool in maintaining miners' health
and safety. The countersigning requirement will provide important
corroboration of this vital action.
One commenter requested that the recordkeeping requirement be more
specific. This commenter requested clarification on alternate methods
of recordkeeping, specifically questioning electronic signatures for
electronic records.
The final rule requires that examination, testing, and repair
records for mine equipment must not be susceptible to alteration. MSHA
recognizes that electronic storage of records is becoming a more
valuable alternative for the mining industry. In response to comments,
the final rule includes a new provision to require that records be
maintained either in a secure book that is not susceptible to
alteration or electronically in a computer system that is also secure
and not susceptible to alteration. MSHA defines the phrase ``secure and
not susceptible to alteration'' to mean that the stored record,
including signatures, cannot be tampered with or modified. Examples of
books that are considered secure and not susceptible to alteration
include, but are not limited to, record books that are currently
approved by state mine safety agencies and permanently bound books.
Examples of books that are not considered secure and are susceptible to
alteration include loose leaf binders and spiral note books. An example
of an acceptable electronic record storage that is secure would be a
record stored in a ``write once, read many'' drive. MSHA believes that
electronic records meeting these criteria are practical and reliable as
traditional records.
Final paragraph (g)(5), like the proposal, requires that
certifications and records, including those in electronic form, be kept
for at least one year and be made available at the mine for inspection
by authorized representatives of the Secretary and representatives of
miners. MSHA received no comments on this proposal.
Section 75.833 Handling High-Voltage Trailing Cables
Final Sec. 75.833 addresses the requirements for handling
energized trailing cables. It requires that energized trailing cable
not be handled unless high-voltage insulating gloves or insulated cable
handling tools are used.
Based on comments received on the proposed rule, the re-proposal
contained the option of providing high-voltage insulating gloves, which
include both the rubber gloves and the leather outer protector gloves,
or insulated cable handling tools. MSHA received two comments on the
re-proposal. Both commenters suggested that MSHA should not require the
use of insulating high-voltage gloves because the high-voltage trailing
cable is safer than current trailing cables already permitted for use
without gloves. Under the final rule, gloves are not required if cable
handling tools are used.
Some commenters on the proposal recommended that personal
protective equipment (PPE) be required in addition to the cable
handling tools. MSHA considered this comment and decided that because
PPE is not tested to a nationally-recognized standard, it may not
provide protection to miners. For that reason the final rule does not
require PPE.
Final paragraph (a), like the re-proposal, prohibits handling
energized trailing cables unless high-voltage insulating gloves or
insulating cable handling tools are used.
Final paragraph (b), like the re-proposal, requires that mine
operators make either the insulating gloves or cable handling tools
available for miners to use.
Final paragraph (c), like the re-proposal, addresses the
requirements for insulating gloves and cable handling tools. Final
paragraph (c)(1) addresses the design requirements for rubber gloves
and incorporates by reference the American Society for Testing and
Materials (ASTM) publication ASTM F496-02a, ``Standard Specification
for In-Service Care of Insulating Gloves and Sleeves'' (2002). Final
paragraph (c)(2) requires that the rubber gloves be air-tested to
assure their effectiveness. Final paragraph (c)(3) requires that both
the leather protector and the rubber insulating glove be visually
examined before each use. Final paragraph (c)(4) requires that damaged
rubber gloves be removed from service or destroyed, and that the
leather protector be maintained in good condition or replaced.
Final paragraph (d), like the re-proposal, addresses the
requirements for insulated cable handling tools. Final paragraph (d)(1)
requires that insulated cable handling tools be rated and maintained to
withstand at least 7,500 volts to assure that the handling tools
provide at least the same level of protection to miners as the
insulating high-voltage gloves.
Final paragraph (d)(2) requires that insulated cable handling tools
be designed and manufactured for cable handling to protect miners from
shock hazards. Examples of insulated cable handling tools are hooks,
slings, and tongs, when designed and manufactured for cable handling.
Final paragraph (d)(3) requires that the insulated cable handling
tools be visually examined before each use for signs of damage or
defects.
Final paragraph (d)(4) requires that damaged or defective insulated
cable handling tools be removed from the underground area of the mine
or destroyed to assure that they are not available to use.
Section 75.834 Training
Final Sec. 75.834 is new and addresses training requirements based
on comments received on the proposal. One commenter stated that it is
important to train miners on safety practices where new technologies
are utilized and requested that specific training be required for those
who test and repair high-voltage cables. MSHA originally believed that
part 48 provides sufficient training requirements. Upon consideration,
the final rule contains specific training requirements that are
consistent with the provisions in granted PFMs. It also requires that
the specialized training be specified in the part 48 plans.
Final paragraph (a) requires that miners who perform maintenance on
high-voltage continuous mining machines be trained in high-voltage
safety, testing, and repair and maintenance procedures. Final paragraph
(b) requires that miners who work in the vicinity of high-voltage
continuous mining machines or who move the high-voltage equipment or
cables also be trained in high-voltage safety procedures and
precautions. MSHA's experience is that not only miners who work on
equipment are
[[Page 17545]]
exposed to hazards, but also miners in the vicinity.
Section 75.1002 Installation of Electric Equipment and Conductors;
Permissibility
Existing Sec. 75.1002 addresses requirements for conductors and
cables used in or in by the last open crosscut as well as electrical
equipment, conductors and cables used within 150 feet of pillar
workings. Final Sec. 75.1002 allows the use of shielded, high-voltage
cables that supply power to permissible continuous mining machines in
underground coal mines. No comments were received on this proposal.
IV. Executive Order 12866: Regulatory Planning and Review
Executive Order (E.O.) 12866, as amended, requires that regulatory
agencies assess both the costs and benefits of intended regulations. To
comply with Executive Order 12866, MSHA has prepared a Regulatory
Economic Analysis (REA) for the final rule. The REA contains supporting
data and explanations for the summary materials presented in sections
IV through VII of this preamble, including the covered mining industry,
benefits and costs, feasibility, small business impact, and information
collection requirements. The REA is located on MSHA's Web site at
http://www.msha.gov/rea.HTM#final. A copy of the REA can be obtained
from MSHA's Office of Standards, Regulations and Variances. MSHA has
determined that the final rule will not have an annual effect of $100
million or more on the economy and, therefore, it is not an
economically ``significant regulatory action'' pursuant to section 3(f)
of E.O. 12866.
A. Population at Risk
The final rule applies to all underground coal mines in the United
States. Based on MSHA data, there were 583 underground coal mines
reporting production, employing 44,456 miners, operating in the U.S. in
2008.
B. Benefits
The final rule will reduce the potential for electrical-related
fatalities and injuries when using high-voltage continuous mining
machines due to: Better design and construction criteria; improved
ground-fault protection; handling of lighter cables; and increased
safety requirements for work practices. These design and work practice
requirements offer greater protection against electrical shock, cable
overheating, fire hazards, unsafe work and repair practices, and back
injuries and other sprains caused by handling trailing cables. These
benefits are described in more detail in Chapter III of the REA
associated with this rulemaking.
C. Compliance Costs
MSHA estimates that the final rule will result in total yearly net
compliance cost of approximately $50,100 for all the underground
operators that use high-voltage continuous mining machines. MSHA
estimates that for all underground coal mine operators that use high-
voltage continuous mining machines with 20-500 employees, yearly costs
will be approximately $85,875 and yearly cost savings will be
approximately $45,200, which results in a net cost of approximately
$40,675. For all underground coal mine operators using high-voltage
continuous mining machines with 501+ employees, MSHA estimates yearly
costs of approximately $16,225 and yearly cost savings of approximately
$6,800, which results in a net cost of $9,425. For a complete breakdown
of the compliance costs and savings of the final rule, see Chapter IV
of the REA associated with this rulemaking.
V. Feasibility
MSHA has concluded that the requirements of the final rule are
technologically and economically feasible.
A. Technological Feasibility
High-voltage continuous mining machines have been used to produce
coal in underground coal mines since 1997. Underground coal mine
operators that use high-voltage continuous mining machines are
currently following most of the provisions of the final rule through
conditions set forth in their granted Petitions for Modification
(PFMs). Any requirements in the final rule that are different from
those currently being followed in granted PFMs will not make the
implementation of the final rule technologically infeasible for
underground coal mine operators who choose to use high-voltage
continuous mining machines for extracting coal. MSHA therefore
concludes that the final rule is technologically feasible.
B. Economic Feasibility
MSHA has traditionally used a revenue screening test--whether the
yearly compliance costs of a regulation are less than 1 percent of
revenues, or are negative (i.e., provide net cost savings)--to
establish presumptively that compliance with the regulation is
economically feasible for the mining industry. As estimated in the REA
that accompanies this final rule, the underground coal mining industry
will incur a net yearly compliance cost of approximately $50,100 versus
annual revenue of approximately $18.4 billion per year. On this basis,
the Agency concludes that the rule is economically feasible.
VI. Regulatory Flexibility Act (RFA) and Small Business Regulatory
Enforcement Fairness Act (SBREFA)
Pursuant to the Regulatory Flexibility Act (RFA) of 1980, as
amended by the Small Business Regulatory Enforcement Fairness Act
(SBREFA), MSHA has analyzed the impact of the final rule on small
businesses. Based on that analysis, MSHA has notified the Chief Counsel
for Advocacy, Small Business Administration, and made the certification
under the Regulatory Flexibility Act at 5 U.S.C. 605(b) that the final
rule will not have a significant economic impact on a substantial
number of small entities. The factual basis for this certification is
presented in full in Chapter V of the REA and in summary form below.
A. Definition of a Small Mine
Under the RFA, in analyzing the impact of the final rule on small
entities, MSHA must use the Small Business Administration (SBA)
definition for a small entity or, after consultation with the SBA
Office of Advocacy, establish an alternative definition for the mining
industry by publishing that definition in the Federal Register for
notice and comment. MSHA has not taken such an action and hence is
required to use the SBA definition. The SBA defines a small entity in
the mining industry as an establishment with 500 or fewer employees.
In addition to examining small entities as defined by SBA, MSHA has
also looked at the impact of this final rule on underground coal mines
with fewer than 20 employees, which MSHA and the mining community have
traditionally referred to as ``small mines.'' These small mines differ
from larger mines not only in the number of employees, but also in
economies of scale in material produced, in the type and amount of
production equipment, and in supply inventory. Therefore, the cost of
complying with MSHA's final rule and the impact of the final rule on
small mines will also be different. It is for this reason that small
mines are of special concern to MSHA.
Although the final rule does apply to mine operators with fewer
than 20 employees that choose to use high-
[[Page 17546]]
voltage continuous mining machines, MSHA's experience has been that no
underground coal mine operator with fewer than 20 employees has ever
requested a PFM to use high-voltage continuous mining machines. MSHA
has analyzed the economic impact of the final rule on all underground
coal mine operators with 500 or fewer employees, which conforms to the
requirements of the RFA. The Agency concludes that it can certify that
the final rule will not have a significant economic impact on a
substantial number of small entities that are covered by this final
rule.
B. Factual Basis for Certification
Using SBA's definition of a small mine operator, the estimated
yearly net compliance cost of the final rule on small underground coal
mine operators is approximately $40,675. The estimated yearly net
compliance cost is less than one percent of the estimated annual
revenues of approximately $14.5 billion for small underground coal mine
operators with 500 or fewer employees.
Based on this analysis, MSHA has determined that the final rule
will not have a significant economic impact on a substantial number of
small underground coal mine operators with 500 or fewer employees. MSHA
has certified these findings to the SBA. The factual basis for this
certification is discussed in Chapter V of the REA associated with this
final rule.
VII. Paperwork Reduction Act of 1995
As a result of this final rule there will be: (1) An elimination of
burden hours and related cost approved under OMB control numbers 1219-
0065 and (2) burden hours in the Information Collection Request (ICR)
that accompanies this final rule. The burden hours and related cost for
these two items are discussed below. For a more detailed explanation of
how the burden hours and related cost for the two items were
determined, see Chapter VII of the REA associated with this final rule.
A. Elimination of Burden Hours
As a result of this final rule, mine operators will no longer need
a PFM of existing 30 CFR 75.1002 to use a high-voltage continuous
mining machine. Existing OMB control number 1219-0065 includes annual
burden hours and cost related to the time it takes mine operators to
prepare and file petitions with MSHA, including petitions to use a
high-voltage continuous mining machine. As a result of this rulemaking,
the burden hours and cost approved under OMB control number 1219-0065
that relate to the time it takes operators to prepare and file
petitions need to be reduced to reflect the fact that petitions to use
a high-voltage continuous mining machine will no longer be needed.
Therefore, the burden hours and cost in OMB control number 1219-0065
should be reduced by approximately 48 hours and $3,700 annually.
B. Burden Hours
The final rule will impose approximately 819 first-year burden
hours and related cost of $50,200 on underground coal mine operators
using high-voltage continuous mining machines. Of the 819 first-year
burden hours, 12 hours and related costs of $700 are associated with
conducting a ground-fault and ground-wire monitor circuit test prior to
tramming the high-voltage continuous mining machine as required by
final Sec. 75.829. In addition, 242 hours and related cost of $9,450
are associated with tagging requirements that are required by final
Sec. 75.831. Also, 565 hours and related cost of $40,050 are
associated with final Sec. 75.832(c), which requires a ground-wire
monitor circuit test, and final Sec. 75.832(g), which requires
countersigning of records concerning examinations and tests specified
in final Sec. 75.832(a), (b), and (c).
The following final requirements do not have burden hours
associated with them. Final Sec. 75.825(i) requires that all
compartments providing access to energized high-voltage conductors and
parts display a caution label to warn miners against entering the
compartment(s) before de-energizing incoming high-voltage circuits.
This requirement is not a paperwork burden to mine operators because it
is currently a normal business practice of manufacturers to place such
warning labels on the compartments noted above.
Final Sec. 75.832(a) and (b) require that examinations or tests be
conducted at least once every seven days, and final Sec. 75.832(g)
requires that a record be made of these examinations or tests.
Paragraph (a) requires an examination of the high-voltage continuous
mining machine. Paragraph (b) requires a test of the ground-fault test
circuit. The examinations required by final Sec. 75.832(a) and (b) are
already being conducted as part of a larger weekly examination of
electrical equipment required under existing Sec. 75.512 (electrical
equipment; examination, testing and maintenance). Existing Sec. 75.512
also requires that records be made of these examinations and tests.
Since the burden for conducting examinations and tests required by
final Sec. 75.832(a) and (b) and making records of them is already
accounted for under existing Sec. 75.512 (which is approved under OMB
control number 1219-0116), such activity is not included in the ICR
accompanying this final rule. However, the countersigning of these
records is not part of any existing requirement, and is, therefore,
accounted for in the ICR that accompanies this rulemaking.
C. Details
The information collection package has been submitted to the Office
of Management and Budget (OMB) for review under 44 U.S.C. 3504(h) of
the Paperwork Reduction Act of 1995, as amended. A copy of the
information collection package can be obtained from the Department of
Labor by email request to [email protected] or by phone request at
202-693-4129.
VIII. Other Regulatory Considerations
A. The Unfunded Mandates Reform Act of 1995
MSHA has reviewed the final rule under the Unfunded Mandates Reform
Act of 1995 (2 U.S.C. 1501 et seq.). MSHA has determined that this
final rule does not include any federal mandate that may result in
increased expenditures by State, local, or tribal governments; nor will
it increase private sector expenditures by more than $100 million in
any one year or significantly or uniquely affect small governments.
Accordingly, the Unfunded Mandates Reform Act of 1995 (2 U.S.C. 1501 et
seq.) requires no further Agency action or analysis.
B. Executive Order 13132: Federalism
The final rule does not have ``federalism implications'' because it
will 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.'' Accordingly, under E.O. 13132, no further Agency action
or analysis is required.
C. The Treasury and General Government Appropriations Act of 1999:
Assessment of Federal Regulations and Policies on Families
Section 654 of the Treasury and General Government Appropriations
Act of 1999 (5 U.S.C. 601 note) requires agencies to assess the impact
of Agency action on family well-being. MSHA has determined that the
final rule will have no effect on family stability or safety, marital
commitment, parental rights and authority, or income or poverty of
families and children. The final rule impacts only the underground coal
mine industry. Accordingly, MSHA
[[Page 17547]]
certifies that the final rule will not impact family well-being.
D. Executive Order 12630: Government Actions and Interference With
Constitutionally Protected Property Rights
This final rule does not implement a policy with takings
implications. Accordingly, under E.O. 12630, no further Agency action
or analysis is required.
E. Executive Order 12988: Civil Justice Reform
The final rule was written to provide a clear legal standard for
affected conduct and was carefully reviewed to eliminate drafting
errors and ambiguities, so as to minimize litigation and undue burden
on the Federal court system. Accordingly, the final rule will meet the
applicable standards provided in section 3 of E.O. 12988, Civil Justice
Reform.
F. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks
The final rule will have no adverse impact on children.
Accordingly, under E.O. 13045, no further Agency action or analysis is
required.
G. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
The final rule does not have ``tribal implications'' because it
will not ``have substantial direct effects on one or more Indian
tribes, on the relationship between the Federal government and Indian
tribes, or on the distribution of power and responsibilities between
the Federal government and Indian tribes.'' Accordingly, under E.O.
13175, no further Agency action or analysis is required.
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
Executive Order 13211 requires agencies to publish a statement of
energy effects when a rule has a significant energy action that
adversely affects energy supply, distribution or use. MSHA has reviewed
this final rule for its energy effects because the final rule applies
to the underground mining sector. Because this final rule will result
in yearly net compliance cost of approximately $50,100 to the
underground coal mining industry, relative to annual revenues of $18.4
billion in 2008, MSHA has concluded that it is not a significant energy
action because it is not likely to have a significant adverse effect on
the supply, distribution, or use of energy. Accordingly, under this
analysis, no further Agency action or analysis is required.
List of Subjects in 30 CFR Parts 18 and 75
Coal mining, Incorporation by reference, Mine safety and health,
Reporting and recordkeeping requirements, Underground mining.
Dated: March 29, 2010.
Joseph A. Main,
Assistant Secretary of Labor for Mine Safety and Health.
0
For the reasons set out in the preamble and under the authority of the
Mine Safety and Health Act of 1977, as amended, Chapter I of Title 30,
Code of Federal Regulations, Parts 18 and 75 are amended as follows:
PART 18--ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES
0
1. The authority citation for part 18 continues to read as follows:
Authority: 30 U.S.C. 957 and 961.
0
2. Add Sec. 18.54 to subpart B to read as follows:
Sec. 18.54 High-voltage continuous mining machines.
(a) Separation of high-voltage components from lower voltage
components. In each motor-starter enclosure, barriers, partitions, and
covers must be provided and arranged so that personnel can test and
troubleshoot low- and medium-voltage circuits without being exposed to
energized high-voltage circuits. Barriers or partitions must be
constructed of grounded metal or nonconductive insulating board.
(b) Interlock switches. Each removable cover, barrier, or partition
of a compartment in the motor-starter enclosure providing direct access
to high-voltage components must be equipped with at least two interlock
switches arranged to automatically de-energize the high-voltage
components within that compartment when the cover, barrier, or
partition is removed.
(c) Circuit-interrupting devices. Circuit-interrupting devices must
be designed and installed to prevent automatic re-closure.
(d) Transformers supplying control voltages.
(1) Transformers supplying control voltages must not exceed 120
volts line to line.
(2) Transformers with high-voltage primary windings that supply
control voltages must incorporate a grounded electrostatic (Faraday)
shield between the primary and secondary windings. Grounding of the
shield must be as follows:
(i) Transformers with an external grounding terminal must have the
shield grounded by a minimum of No. 12 A.W.G. grounding conductor
extending from the grounding terminal to the equipment ground.
(ii) Transformers with no external grounding terminal must have the
shield grounded internally through the transformer frame to the
equipment ground.
(e) Onboard ungrounded, three-phase power circuit. A continuous
mining machine designed with an onboard ungrounded, three-phase power
circuit must:
(1) Be equipped with a light that will indicate a grounded-phase
condition;
(2) Have the indicator light installed so that it can be observed
by the operator from any location where the continuous mining machine
is normally operated; and
(3) Have a test circuit for the grounded-phase indicator light
circuit to assure that the circuit is operating properly. The test
circuit must be designed so that, when activated, it does not require
removal of any electrical enclosure cover or create a double-phase-to-
ground fault.
(f) High-voltage trailing cable(s). High-voltage trailing cable(s)
must conform to the ampacity and outer dimensions specified in Table 10
of Appendix I to Subpart D of this part. In addition, the cable must be
constructed with:
(1) 100 percent semi-conductive tape shielding over each insulated
power conductor;
(2) A grounded metallic braid shielding over each insulated power
conductor;
(3) A ground-check conductor not smaller than a No. 10 A.W.G.; or
if a center ground-check conductor is used, not smaller than a No. 16
A.W.G. stranded conductor; and
(4) Either a double-jacketed or single-jacketed cable as follows:
(i) Double jacket. A double-jacketed cable consisting of reinforced
outer and inner protective layers. The inner layer must be a
distinctive color from the outer layer. The color black must not be
used for either protective layer. The tear strength for each layer must
be more than 40 pounds per inch thickness and the tensile strength must
be more than 2,400 pounds per square inch.
(ii) Single jacket. A single-jacketed cable consisting of one
protective layer. The tear strength must be more than 100 pounds per
inch thickness, and the
[[Page 17548]]
tensile strength must be more than 4,000 pounds per square inch. The
cable jacket must not be black in color.
(g) Safeguards against corona. Safeguards against corona must be
provided on all 4,160-voltage circuits in explosion-proof enclosures.
(h) Explosion-proof enclosure design. The maximum pressure rise
within an explosion-proof enclosure containing high-voltage switchgear
must be limited to 0.83 times the design pressure.
(i) Location of high-voltage electrical components near flame
paths. High-voltage electrical components located in high-voltage
explosion-proof enclosures must not be coplanar with a single plane
flame-arresting path.
(j) Minimum creepage distances. 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 (inches) for comparative tracking index
Points of (CTI) range \1\
Phase-to-phase voltage measure -----------------------------------------------------------------------
CTI >= 500 380 <= CTI < 500 175 <= CTI < 380 CTI < 175
--------------------------------------------------------------------------------------------------------------------------------------------------------
2,400......................................................... 0-0 1.50 1.95 2.40 2.90
0-G 1.00 1.25 1.55 1.85
4,160......................................................... 0-0 2.40 3.15 3.90 4.65
0-G 1.50 1.95 2.40 2.90
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Assumes that all insulation is rated for the applied voltage or higher.
(k) Minimum free distances. 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:
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steel MFD (in) Aluminum MFD (in)
Wall/cover thickness (in) -----------------------------------------------------------------------------------------------------------
A \1\ B \2\ C \3\ A \1\ B \2\ C \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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 in accordance with the minimum clearance table of Sec. 18.24.
\1\ Column A specifies the MFD for enclosures that have available three-phase, bolted, short-circuit currents of 10,000 amperes root-mean-square (rms)
value or less.
\2\ Column B specifies the MFD for enclosures that have maximum available three-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 maximum available three-phase, bolted, short-circuit currents greater than 15,000 and less than
or equal to 20,000 amperes rms.
\4\ Not Applicable--MSHA does not allow aluminum wall or covers to be \1/4\ inch or less in thickness. (See also Sec. 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.
(i) Steel Wall/Cover:
[GRAPHIC] [TIFF OMITTED] TR06AP10.000
(ii) Aluminum Wall/Cover:
[GRAPHIC] [TIFF OMITTED] TR06AP10.001
Where ``C'' is 1.4 for 2,400 volt systems or 3.0 for 4,160 volt
systems; ``Isc'' is the three-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.
(l) Static pressure testing of explosion-proof enclosures
containing high-voltage switchgear.
(1) Prototype enclosures. The following static pressure test must
be performed on each prototype design of an explosion-proof enclosure
containing high-voltage switchgear prior to the explosion tests.
[[Page 17549]]
(i) Test procedure.
(A) The enclosure must be internally pressurized to at least the
design pressure, maintaining the pressure for a minimum of 10 seconds.
(B) Following the pressure hold, the pressure must be removed and
the pressurizing agent removed from the enclosure.
(ii) Acceptable performance.
(A) During pressurization, the enclosure must not exhibit:
(1) Leakage through welds or casting; or
(2) Rupture of any part that affects the explosion-proof integrity
of the enclosure.
(B) Following removal of the pressurizing agents, the enclosure
must not exhibit:
(1) Cracks in welds visible to the naked eye;
(2) Permanent deformation exceeding 0.040 inches per linear foot;
or
(3) Excessive clearances along flame-arresting paths following
retightening of fastenings, as necessary.
(2) Enclosures for production. Every explosion-proof enclosure
containing high-voltage switchgear manufactured after the prototype was
tested must undergo one of the following tests or procedures:
(i) The static pressure test specified in paragraph (l)(1)(i) of
this section; or
(ii) An MSHA-accepted quality assurance procedure covering
inspection of the enclosure.
(A) The quality assurance procedure must include a detailed check
of parts against the drawings to determine that--
(1) The parts and the drawings coincide; and
(2) The requirements stated in part 18 have been followed with
respect to materials, dimensions, configuration and workmanship.
(B) [Reserved]
Appendix I to Subpart D [Amended]
0
3. Add Table 10 to Appendix I to Subpart D of Part 18 to read as
follows:
* * * * *
Table 10--High Voltage Trailing Cable Ampacities and Outside Diameters
----------------------------------------------------------------------------------------------------------------
Power conductor Ampacity * Outside diameter ** (inches)
----------------------------------------------------------------------------------------------------------------
Amperes per SHD-GC 2001 to SHD-CGC 2001 to SHD-PCG 2001 to
Size AWG or kcmil conductor 5000 volts 5000 volts 5000 volts
----------------------------------------------------------------------------------------------------------------
6....................................... 93 1.56 1.62 ................
4....................................... 122 1.68 1.73 ................
3....................................... 140 1.78 1.82 1.94
2....................................... 159 1.87 1.91 2.03
1....................................... 184 1.95 1.98 2.12
1/0..................................... 211 2.08 2.10 2.26
2/0..................................... 243 2.20 2.20 2.40
3/0..................................... 279 2.36 2.36 2.58
4/0..................................... 321 2.50 2.50 2.76
250..................................... 355 2.69 2.69 ................
300..................................... 398 2.81 2.81 ................
350..................................... 435 2.95 2.95 ................
500..................................... 536 3.31 3.31 ................
----------------------------------------------------------------------------------------------------------------
These ampacities are based on single isolated conductor in air, operated with open-circuited shield for a 90
[deg]C conductor temperature and an ambient temperature of 40 [deg]C.
** Tolerances for the outside diameter are +8%/-5%.
PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES
0
4. The authority citation for Part 75 continues to read as follows:
Authority: 30 U.S.C. 811.
0
5. Add Sec. Sec. 75.823 through 75.834 to subpart I, to read as
follows:
Sec. 75.823 Scope.
Sections 75.823 through 75.834 of this part are electrical safety
standards applicable to 2,400 volt continuous mining machines and
circuits. A ``qualified person'' as used in these sections means a
person meeting the requirements of Sec. 75.153. Other standards in 30
CFR apply to these circuits and equipment where appropriate.
Sec. 75.824 Electrical protection.
(a) Trailing cable protection. The trailing cable extending to the
high-voltage continuous mining machine must be protected by a circuit-
interrupting device of adequate interrupting capacity and voltage that
provides short-circuit, overload, ground-fault, and under-voltage
protection as follows:
(1) Short-circuit protection.
(i) The current setting of the device must be the setting specified
in the approval documentation or 75 percent of the minimum available
phase-to-phase short-circuit current, whichever is less; and
(ii) The time-delay setting must not exceed 0.050 seconds.
(2) Ground-fault protection.
(i) Neutral grounding resistors must limit the ground-fault current
to no more than 0.5 ampere.
(ii) Ground-fault devices must cause de-energization of the circuit
extending to the continuous mining machine at not more than 0.125
ampere. The time-delay of the device must not exceed 0.050 seconds.
(iii) Look-ahead circuits must detect a ground-fault condition and
prevent the circuit-interrupting device from closing as long as the
ground-fault condition exists.
(iv) Backup ground-fault devices must cause de-energization of the
circuit extending to the continuous mining machine at not more than 40
percent of the voltage developed across the neutral grounding resistor
when a ground fault occurs with the neutral grounding resistor open.
The time-delay setting of the backup device must not exceed 0.25
seconds.
(v) Thermal devices must detect a sustained ground-fault current in
the neutral grounding resistor and must de-energize the incoming power.
The device must operate at either 50 percent of the maximum temperature
rise of the neutral grounding resistor or 302[deg] F (150[deg] C),
whichever is less. Thermal protection must not be dependent on control
power and may consist of a current transformer and over-current
[[Page 17550]]
relay in the neutral grounding resistor circuit.
(vi) A single window-type current transformer that encircles all
three-phase conductors must be used to activate the ground-fault device
protecting the continuous mining machine. Equipment grounding
conductors must not pass through the current transformer.
(vii) A test circuit for the ground-fault device must be provided.
The test circuit must inject no more than 50 percent of the current
rating of the neutral grounding resistor through the current
transformer. When the test circuit is activated, the circuit-
interrupting device must open.
(3) Under-voltage protection. The under-voltage device must operate
on a loss of voltage, de-energize the circuit, and prevent the
equipment from automatically restarting.
(b) Re-closing. Circuit-interrupting devices must not re-close
automatically.
(c) Onboard Power Circuits. When a grounded-phase indicator light
circuit is used and it indicates a grounded-phase fault, the following
corrective actions must be taken:
(1) The machine must be moved immediately to a location with a
properly supported roof; and
(2) The grounded-phase condition must be located and corrected
prior to placing the continuous mining machine back into operation.
Sec. 75.825 Power centers.
(a) Main disconnecting switch. The power center supplying high
voltage power to the continuous mining machine must be equipped with a
main disconnecting switch that, when in the open position, de-energizes
input to all power transformers.
(b) Trailing cable disconnecting device. In addition to the main
disconnecting switch required in paragraph (a) of this section, the
power center must be equipped with a disconnecting device for each
circuit that supplies power to a high-voltage continuous mining
machine. A disconnecting device is defined as a disconnecting switch or
a cable coupler.
(c) Disconnecting switches. Each disconnecting switch must be
labeled to clearly identify the circuit it disconnects, and be designed
and installed as follows:
(1) Rated for the maximum phase-to-phase voltage of the circuit;
(2) Rated for the full-load current of the circuit that is supplied
power through the device.
(3) Allow for visual observation, without removing any covers, to
verify that the contacts are open;
(4) Ground all power conductors on the load side when the switch is
in the ``open and grounded'' position;
(5) Can only be locked out in the ``open and grounded'' position;
and
(6) Safely interrupts the full-load current of the circuit or
causes the current to be interrupted automatically before the
disconnecting switch opens.
(d) Barriers and covers. All compartments that provide access to
high-voltage circuits must have barriers and/or covers to prevent
miners from contacting energized high-voltage circuits.
(e) Main disconnecting switch and control circuit interlocking. The
control circuit must be interlocked with the main disconnecting switch
in the power center so that:
(1) When the main disconnecting switch is in the ``open'' position,
the control circuit can only be powered through an auxiliary switch in
the ``test'' position; and
(2) When the main disconnecting switch is in the ``closed''
position, the control circuit can only be powered through an auxiliary
switch in the ``normal'' position.
(f) Interlocks. Each cover or removable barrier providing access to
high-voltage circuits must be equipped with at least two interlock
switches. Except when the auxiliary switch is on the ``test'' position,
removal of any cover or barrier that exposes energized high-voltage
circuits must cause the interlock switches to automatically de-energize
the incoming circuit to the power center.
(g) Emergency stop switch. The power center must be equipped with
an externally accessible emergency stop switch hard-wired into the
incoming ground-wire monitor circuit that de-energizes the incoming
high-voltage in the event of an emergency.
(h) Grounding stick. The power center must be equipped with a
grounding stick to be used prior to performing electrical work to
assure that high-voltage capacitors are discharged and circuits are de-
energized. The power center must have a label readily identifying the
location of the grounding stick. The grounding stick must be stored in
a dry location.
(i) Caution label. All compartments providing access to energized
high-voltage conductors and parts must display a caution label to warn
miners against entering the compartments before de-energizing incoming
high-voltage circuits.
Sec. 75.826 High-voltage trailing cables.
High-voltage trailing cables must:
(a) Meet existing trailing cable requirements and the approval
requirements of the high-voltage continuous mining machine; and
(b) Meet existing ground-check conductor requirements (Sec.
75.804) or have a stranded center ground-check conductor not smaller
than a No. 16 A.W.G.
Sec. 75.827 Guarding of trailing cables.
(a) Guarding.
(1) The high-voltage cable must be guarded in the following
locations:
(i) From the power center cable coupler for a distance of 10 feet
inby the power center;
(ii) From the entrance gland for a distance of 10 feet outby the
last strain clamp on the continuous mining machine; and,
(iii) At any location where the cable could be damaged by moving
equipment.
(2) Guarding must be constructed using nonconductive flame-
resistant material or grounded metal.
(b) Suspended cables and cable crossovers. When equipment must
cross any portion of the cable, the cable must be either:
(1) Suspended from the mine roof; or
(2) Protected by a cable crossover having the following
specifications:
(i) A minimum length of 33 inches;
(ii) A minimum width of 17 inches;
(iii) A minimum height of 3 inches;
(iv) A minimum cable placement area of two and one half-inches
(2\1/2\) high by four and one-quarter inches (4\1/
4\) wide;
(v) Made of nonconductive material;
(vi) Made of material with a distinctive color. The color black
must not be used; and
(vii) Made of material that has a minimum compressive strength of
6,400 pounds per square inch (psi).
Sec. 75.828 Trailing cable pulling.
The trailing cable must be de-energized prior to being pulled by
any equipment other than the continuous mining machine. The cable
manufacturer's recommended pulling procedures must be followed when
pulling the trailing cable with equipment other than the continuous
mining machine.
Sec. 75.829 Tramming continuous mining machines in and out of the
mine and from section to section.
(a) Conditions of use. Tramming the continuous mining machine in
and out of the mine and from section to section must be done in
accordance with movement requirements of high-voltage power centers and
portable transformers (Sec. 75.812) and as follows:
(1) The power source must not be located in areas where permissible
equipment is required;
[[Page 17551]]
(2) The continuous mining machine must not be used for mining or
cutting purposes, unless a power center is used in accordance with
Sec. Sec. 75.823 through 75.828 and Sec. Sec. 75.830 through 75.833;
(3) Low-, medium-, and high-voltage cables must comply with
Sec. Sec. 75.600-1, 75.907, and 75.826, as applicable; and
(4) The energized high-voltage cable must be mechanically secured
onboard the continuous mining machine. This provision applies only when
using the power sources specified in paragraphs (c)(2) and (c)(3) of
this section.
(b) Testing prior to tramming. Prior to tramming the continuous
mining machine,
(1) A qualified person must activate the ground-fault and ground-
wire monitor test circuits of the power sources specified in paragraph
(c) of this section to assure that the corresponding circuit-
interrupting device opens the circuit. Corrective actions and
recordkeeping resulting from these tests must be in accordance with
Sec. Sec. 75.832(f) and (g).
(2) Where applicable, a person designated by the mine operator must
activate the test circuit for the grounded-phase detection circuit on
the continuous mining machine to assure that the detection circuit is
functioning properly. Corrective actions resulting from this test must
be in accordance with Sec. 75.832(f).
(c) Power sources. In addition to the power center specified in
Sec. 75.825, the following power sources may be used to tram the
continuous mining machine.
(1) Medium-voltage power source. A medium-voltage power source is a
source that supplies 995 volts through a trailing cable (See Figure 1
of this section) to the continuous mining machine. The medium-voltage
power source must--
(i) Not be used to back-feed the high-voltage circuits of the
continuous mining machine; and
(ii) Meet all applicable requirements for medium-voltage circuits
in 30 CFR 75.
[GRAPHIC] [TIFF OMITTED] TR06AP10.002
(2) Step-up transformer. A step-up transformer is a transformer
that steps up the low or medium voltage to high voltage (See Figure 2
in this section) and must meet the following requirements:
(i) The trailing cable supplying low or medium voltage to the step-
up transformer must meet the applicable requirements of 30 CFR part 75;
(ii) The high-voltage circuit output of the step-up transformer
supplying power to the continuous mining machine must meet the
applicable provisions of Sec. 75.824;
(iii) The step-up transformer enclosure must be--
(A) Securely mounted to minimize vibration on:
(1) The continuous mining machine; or
(2) A sled/cart that must be connected to the continuous mining
machine by a tow-bar and be in close proximity to the mining machine.
(B) Grounded as follows:
(1) Connected to the incoming ground conductor of the low- or
medium-voltage trailing cable;
(2) Bonded by a No. 1/0 A.W.G. or larger external grounding
conductor to the continuous mining machine frame; and
(3) Bonded by a No. 1/0 A.W.G. or larger external grounding
conductor to the metallic shell of each cable coupler.
(C) Equipped with:
(1) At least two interlock switches for each of the enclosure
covers; and
(2) An external emergency stop switch to remove input power to the
step-up transformer.
[GRAPHIC] [TIFF OMITTED] TR06AP10.003
Sec. 75.830 Splicing and repair of trailing cables.
(a) Splices and repairs.
(1) Splicing means the mechanical joining of one or more severed
conductors in a single length of a cable including the replacement of:
Insulation, semi-conductive tape, metallic shielding, and the outer
jacket(s).
(2) Repair means to fix damage to any component of the cable other
than the conductor.
(3) Splices and repairs to high-voltage trailing cables must be
made:
(i) Only by a qualified person trained in the proper methods of
splicing and repairing high-voltage trailing cables;
(ii) In a workman-like manner;
(iii) In accordance with Sec. 75.810; and
(iv) Using only MSHA-approved high-voltage kits that include
instructions for outer-jacket repairs and splices.
[[Page 17552]]
(b) Splicing limitations.
(1) Splicing of the high-voltage trailing cable within 35 feet of
the continuous mining machine is prohibited.
(2) Only four (4) splices will be allowed at any one time for the
portion of the trailing cable that extends from the continuous miner
outby for a distance of 300 feet.
Sec. 75.831 Electrical work; troubleshooting and testing.
(a) Trailing cable and continuous mining machine electrical work
procedures. Prior to performing electrical work, other than
troubleshooting and testing, on the high-voltage trailing cable or the
continuous mining machine, a qualified person must de-energize the
power center and follow procedures specified in paragraph (1) or (2):
(1) If a trailing cable disconnecting switch is provided:
(i) Open and ground the power conductors, lock out and tag the
disconnecting switch; and
(ii) Lock out and tag the plug to the power receptacle.
(2) If a trailing cable disconnecting switch is not provided and a
cable coupler is used as a disconnecting device:
(i) Remove the plug from the power receptacle and connect it to the
grounding receptacle;
(ii) Lock out and tag the plug to the grounding receptacle; and
(iii) Place a dust cover over the power receptacle.
(b) Troubleshooting and testing the trailing cable. During
troubleshooting and testing, the de-energized high-voltage cable may be
disconnected from the power center only for that period of time
necessary to locate the defective condition. Prior to troubleshooting
and testing trailing cables, a qualified person must perform the
following:
(1) If a trailing cable disconnecting switch is provided:
(i) Open and ground power conductors and lock out and tag the
disconnecting switch;
(ii) Disconnect the plug from the power receptacle;
(iii) Lock out and tag the plug; and
(iv) Place a dust cover over the power receptacle.
(2) If a trailing cable disconnecting switch is not provided and a
cable coupler is used as a disconnecting device:
(i) Remove the plug from the power receptacle and connect it to the
grounding receptacle to ground the power conductors;
(ii) Remove the plug from the grounding receptacle and install a
lock and tag on the plug; and
(iii) Place a dust cover over the power receptacle.
(c) Troubleshooting and testing limitations. Troubleshooting and
testing 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;
(3) By qualified persons; and
(4) When using protective gloves in accordance with the following
table:
------------------------------------------------------------------------
Circuit voltage Type of glove required
------------------------------------------------------------------------
Greater than 120 volts (nominal) (not Rubber insulating gloves with
intrinsically safe). leather protectors.
40 volts to 120 volts (nominal) (both Either rubber insulating gloves
intrinsically safe and non- with leather protectors or dry
intrinsically safe). work gloves.
Greater than 120 volts (nominal) Either rubber insulating gloves
(intrinsically safe). with leather protectors or dry
work gloves.
------------------------------------------------------------------------
(d) Power center electrical work procedures. Before any work is
performed inside any compartment of the power center, except for
troubleshooting and testing energized circuits as specified in
paragraph (c) of this section, a qualified person must:
(1) De-energize affected circuits;
(2) Open the corresponding disconnecting switch, lock it out, and
tag it to assure the circuit is isolated;
(3) Visually verify that the contacts of the disconnecting switch
are open and grounded; and
(4) Discharge all high-voltage capacitors and circuits.
(e) Locking out and tagging responsibilities.
(1) When more than one qualified person is performing electrical
work, including troubleshooting and testing, each person must install
an individual lock and tag. Each lock and tag must be removed only by
the persons who installed them.
(2) If the person who installed the lock and tag is unavailable,
the lock and tag may be removed by a person authorized by the operator,
provided that:
(i) The authorized person is a qualified person; and
(ii) The mine operator assures that the person who installed the
lock and tag is aware that the lock and tag have been removed.
Sec. 75.832 Frequency of examinations; recordkeeping.
(a) Continuous mining machine examination. At least once every 7
days, a qualified person must examine each high-voltage continuous
mining machine to verify that electrical protection, equipment
grounding, permissibility, cable insulation, and control devices are
properly installed and maintained.
(b) Ground-fault test circuit. At least once every 7 days, and
prior to tramming the high-voltage continuous mining machine, a
qualified person must activate the ground-fault test circuit to verify
that it will cause the corresponding circuit-interrupting device to
open.
(c) Ground-wire monitor test. At least once every 7 days, and prior
to tramming the high-voltage continuous mining machine, a qualified
person must examine and test each high-voltage continuous mining
machine ground-wire monitor circuit to verify that it will cause the
corresponding circuit-interrupting device to open.
(d) Trailing cable inspections.
(1) Once each day during the shift that the continuous mining
machine is first energized, a qualified person must de-energize and
inspect the entire length of the high-voltage trailing cable from the
power center to the continuous mining machine. The inspection must
include examination of the outer jacket repairs and splices for damage,
and assure guarding is provided where required.
(2) At the beginning of each shift that the continuous mining
machine is energized, a person designated by the mine operator must de-
energize and visually inspect the high-voltage trailing cable for
damage to the outer jacket. This inspection must be conducted from the
continuous mining machine to the following locations:
(i) The last open crosscut;
(ii) Within 150 feet of the working place during retreat or second
mining; or
(iii) Up to 150 feet from the continuous mining machine when the
machine is used in outby areas.
[[Page 17553]]
(e) Grounded-phase detection test. When a grounded-phase test
circuit is provided on a high-voltage continuous mining machine, a
person designated by the mine operator must activate the test circuit
at the beginning of each production shift to assure that the detection
circuit is functioning properly.
(f) Corrective action. When examinations or tests of equipment
reveal a risk of fire, electrical shock, ignition, or operational
hazard, the equipment must be immediately removed from service or
repaired.
(g) Record of tests.
(1) At the completion of examinations and tests required under
paragraphs (a), (b), and (c) of this section, the person conducting the
examinations and tests must:
(i) Certify by signature and date that the examinations and tests
have been conducted.
(ii) Make a record of any unsafe condition found.
(2) Any corrective action(s) must be recorded by the person taking
the corrective action.
(3) The record must be countersigned by the mine foreman or
equivalent mine official by the end of the mine foreman's or the
equivalent mine official's next regularly scheduled working shift.
(4) Records must be maintained in a secure book that is not
susceptible to alteration or electronically in a computer system so as
to be secure and not susceptible to alteration.
(5) Certifications and records must be kept for at least 1 year and
must be made available for inspection by authorized representatives of
the Secretary and representatives of miners.
Sec. 75.833 Handling high-voltage trailing cables.
(a) Cable handling.
(1) Miners must not handle energized trailing cables unless they
are wearing high-voltage insulating gloves, which include the rubber
gloves and leather outer protector gloves, or are using insulated cable
handling tools that meet the requirements of paragraph (c) or (d) of
this section.
(2) Miners must not handle energized high-voltage cables with any
parts of their bodies except by hand in accordance with paragraph (1)
above.
(b) Availability. Each mine operator must make high-voltage
insulating gloves or insulated cable handling tools available to miners
handling energized high-voltage trailing cables.
(c) High-voltage insulating gloves. High-voltage insulating gloves
must meet the following requirements:
(1) The rubber gloves must be designed and maintained to have a
voltage rating of at least Class 1 (7,500 volts) and tested every 30
days in accordance with publication ASTM F496-02a, ``Standard
Specification for In-Service Care of Insulating Gloves and Sleeves''
(2002). The Director of the Federal Register approved this
incorporation by reference in accordance with 5 U.S.C. 522(a) and 1 CFR
part 51. ASTM F496-02a may be obtained from the American Society for
Testing and Materials, 100 Barr Harbor Drive, West Conshohocken,
Pennsylvania 19428-2959, call 610-832-9500 or go to http://astm.org.
ASTM F496-02a is available for inspection at any MSHA Coal Mine Safety
and Health District office, at the MSHA Office of Standards,
Regulations, and Variances, 1100 Wilson Boulevard, Room 2350,
Arlington, VA 22209-3939, 202-693-9440, or at the National Archives and
Records Administration (NARA). For information on the availability of
this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
(2) The rubber glove portion must be air-tested at the beginning of
each shift to assure its effectiveness.
(3) Both the leather protector and rubber insulating gloves must be
visually examined before each use for signs of damage or defects.
(4) Damaged rubber gloves must be removed from the underground area
of the mine or destroyed. Leather protectors must be maintained in good
condition or replaced.
(d) Insulated cable handling tools. Insulated cable handling tools
must be:
(1) Rated and properly maintained to withstand at least 7,500
volts;
(2) Designed and manufactured for cable handling;
(3) Visually examined before each use for signs of damage or
defects; and
(4) Removed from the underground area of the mine or destroyed if
damaged or defective.
Sec. 75.834 Training.
In addition to existing part 48 task training, hazard training,
training for qualified persons under existing Sec. 75.153, and annual
refresher training, the following specialized training shall be
provided and specified in the part 48 plan:
(a) Training for miners who perform maintenance on high-voltage
continuous mining machines in high-voltage safety, testing, and repair
and maintenance procedures.
(b) Training for personnel who work in the vicinity of high-voltage
continuous mining machines in safety procedures and precautions for
moving the high-voltage machines or the trailing cables.
0
6. Amend Sec. 75.1002 by adding paragraph (b)(5) to read as follows:
Sec. 75.1002 Installation of electric equipment and conductors;
permissibility.
* * * * *
(b) * * *
(5) Shielded high-voltage cables supplying power to permissible
continuous mining machines.
[FR Doc. 2010-7309 Filed 4-5-10; 8:45 am]
BILLING CODE 4510-13-P