Monday, March 11, 2002
Part II
Department of Labor Mine Safety and Health Administration
30 CFR Parts 18 and 75 Electric Motor-Driven Mine Equipment and Accessories and High-Voltage Longwall Equipment Standards for Underground Coal Mines; Final Rule
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DEPARTMENT OF LABOR underground coal mines and allowed the industry’s need for higher voltages the use of high-voltage longwall and the marked improvement in the Mine Safety and Health Administration equipment. However, it did not design and manufacturing technology of specifically focus on the safety issues high-voltage components, MSHA 30 CFR Parts 18 and 75 related to the use of high-voltage developed rules that establish RIN 1219–AA75 longwall equipment. The Agency requirements for safe high-voltage published a new proposed rule (57 FR electric equipment use. This rule Electric Motor-Driven Mine Equipment 39036) on August 27, 1992, related provides improved design requirements and Accessories and High-Voltage specifically to the safe use of high- for longwall equipment, consistent with Longwall Equipment Standards for voltage longwall equipment in existing requirements in 30 CFR part 18, Underground Coal Mines underground coal mines. These rules and contains provisions that also specifically addressed approval accommodate new design technology, AGENCY: Mine Safety and Health requirements for high-voltage electrical are practical, and lessen burdens on the Administration (MSHA), Labor. equipment operated in longwall face mining community, while preserving ACTION: Final rule. areas of underground coal mines. The safety and health protections for miners. comment period on the proposed rule The safety criteria supporting the rule SUMMARY: This final rule establishes was scheduled to close on October 23, are based on research conducted over MSHA’s new mandatory electrical 1992, but was extended to November 13, the past 18 years by the former U.S. safety standards for the installation, use, 1992 (57 FR 48350). On October 18, Bureau of Mines (USBM) and MSHA. and maintenance of high-voltage 1995, (60 FR 53891), MSHA reopened USBM functions are now a part of the longwall mining systems used in the rulemaking record for additional National Institute of Occupational underground coal mines. The final rule comments to the proposed rule to Safety and Health. This research also includes design approval provide all interested parties an included the following: (1) Foster-Miller requirements for high-voltage opportunity to submit additional research, under USBM contract No. equipment operated in longwall face comments. The comment period was H0308093, which developed a areas of underground mines. These scheduled to close on November 14, recommended high-voltage permissible provisions allow the use of high-voltage 1995, but was extended to December 18, loadcenter criteria; (2) MSHA research, longwall face equipment with enhanced 1995 (60 FR 57203). The Agency under USBM contract No. J0333909, safety protection from fire, explosion, received no requests for a public hearing which resulted in modified criteria to and shock hazards. In addition to on the proposed rule. The record was address high-voltage permissible providing a safer mining environment reopened December 28, 1999, for switchgear enclosures and the and facilitating the use of advanced comments on the updated Preliminary development of test facilities for equipment designs, the final rule Regulatory Impact Analysis (PRIA). The acceptance of high-voltage permissible reduces paperwork requirements by record closed February 28, 2000. Only loadcenters and switchgear enclosures; eliminating the need for petitions for one comment was received. The (3) Follow-up MSHA inspections on modification (variances). commenter agreed with our economic high-voltage machines and longwall analysis of the cost impact of the DATES: This regulation is effective May mining systems operating under proposed rule. 10, 2002. The incorporation by reference experimental permits to confirm design These revised standards allow the use of certain publications listed in the rule requirements and operational safety; (4) is approved by the Director of the of high-voltage longwall mining systems. Longwall mining methods have MSHA internal research and review of Federal Register May 10, 2002. engineering reports for further analysis FOR FURTHER INFORMATION CONTACT: undergone numerous advances in technology during the past 25 years. of hazards relating to explosion-proof Marvin W. Nichols, Jr., Director, Office enclosures which contain high-voltage of Standards, Regulations and These technological advances have led to improved and safer systems. The switching; and, (5) Input from various Variances, MSHA, 4015 Wilson additional requirements under 30 CFR technical experts throughout the mining Boulevard, Arlington, Virginia 22203– part 18 provide enhanced safety community. These criteria are 1984. Mr. Nichols can be reached at protections that are consistent with technically sound and have the general [email protected] (Internet advances in mine technology that consensus of the mining community, e-mail), 703—235–1910 (voice), or 703– allows high-voltage switchgear to be including equipment manufacturers and 235–5551 (fax). You may obtain copies used on face equipment. Title 30 CFR other interested parties. of the final rule in alternative formats by parts 18 and 75 of this final rule The first high-voltage longwall system calling this number. The alternative implements a number of changes to started operating in 1985. Since that formats available are either a large print approval and safety requirements for time we have issued approximately 130 version of the final rule or the final rule high-voltage equipment to accommodate system design approvals for high- in an electronic file on computer disk. the advances in technology in a manner voltage longwall equipment. Over the The final rule also is available on the that protects the safety of miners. last 16 years, no electrical-type fatalities Internet at http://www.msha.gov/ or serious injuries occurred to miners REGSINFO.HTM. A. Part 18 Electric Motor-Driven Mine because of high-voltage equipment used Equipment and Accessories SUPPLEMENTARY INFORMATION: in accordance with over 100 granted Electrical equipment horsepower in high-voltage petitions for modification I. Background mines has increased over the years. The (petitions). Because of this new On December 4, 1989, the Mine Safety voltages required to operate this improved high-voltage technology, the and Health Administration (MSHA) equipment have also increased to designed safety benefits and the published a proposed rule (54 FR accommodate the design of practical observed use experience, MSHA is 50062) to revise its electrical safety and efficient equipment. The design of revising its existing 30 CFR part 18 standards for underground coal mines. safe, efficient, and practical high-voltage electric motor-driven mine equipment That proposed rule addressed all of the electric equipment has improved and accessories approval requirements Agency’s electrical standards for dramatically in recent years. Because of by adding specific design requirements
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for high-voltage longwall equipment in concerns about explosion, fire and include provisions addressing non- underground mines. shock hazards initially associated with electrical safety and health areas. MSHA received comments from all high-voltage use are sufficiently Specifically, they noted that high- segments of the mining industry, and addressed by this newly-developed voltage longwall systems of extended the final rule addresses these comments. technology. In each of the petition cases widths and lengths can adversely affect Many commenters were in favor of the the Agency granted, MSHA performed a not only ventilation, but shearer new approval requirements and were in specific on-site investigation to verify mounted methane monitors, intake agreement on the majority of the this finding. For example, we escapeways, exposure to respirable dust, provisions in the proposed rule. MSHA recognized that high-voltage electric tailgate travelways, and storage plans for carefully reviewed all of the comments. equipment and circuit design self-contained self-rescuers (SCSR’s), as This resulted in the modification of four improvements in combination with well as return entry rockdusting during of the sixteen technical requirements sensitive electrical circuit protections mining. addressed in the proposed rule. We reduce fire, explosion and shock It is the Agency’s view that non- considered the views of all interested hazards. Newly designed cable handling electrical safety and health issues parties, including: mine operators; systems provide additional safety related to the use of high-voltage equipment manufacturers; miners’ protections against electrical shock, fire longwalls are fully addressed by representatives; and other government and explosion hazards when the cable is existing safety and health standards agencies in developing this final rule. moved. Further, lighter power cables are under 30 CFR parts 70 and 75. This MSHA is publishing this high-voltage available which reduce back strain and view has been upheld by administrative longwall approval rule (30 CFR part 18) other injury risks to miners from the law judge, Assistant Secretary and Court along with mandatory safety standards heavier cable lifting and hauling often of Appeals decisions. UMWA v. Federal regarding high-voltage longwall associated with the moving or lifting of Mine Safety and Health Administration, equipment (30 CFR part 75). This new low- to medium-voltage cables. 931 F. 2d 908,913 (D.C. Cir. 1991). The 30 CFR part 18 rule provides additional Moreover, there have been no electrical promulgated standards relating to high-voltage equipment specifications fatalities and no serious electrical ventilation and escapeways under 30 that must be followed by the injuries to miners from high-voltage CFR 75.300 et seq. (61 FR 9764, March manufacturer in order to obtain MSHA equipment used under the granted 11, 1996) provide protection with approval of the equipment. The new 30 modifications. respect to ventilation and escapeways. CFR part 75 rule provides installation, Because of the new improved high- Mandatory health standards under part use, and maintenance requirements for voltage technology, with its attendant 70 address exposures to respirable dust. high-voltage longwalls in underground safety benefits, MSHA is revising its Section 75.215—Longwall mining coal mines. existing 30 CFR part 75 electrical safety systems—addresses longwall tailgate standards. This final rule does not B. Part 75 High-Voltage Longwall travelway protection. Storage plans for reduce the protection afforded by Equipment Safety Standards SCSRs may be approved by MSHA existing 30 CFR part 75 standards. It District Managers in accordance with This part of the final rule provides does, however, provide increased the specific conditions at each mine safety requirements for underground protection from electrical hazards, and under § 75.1714–2—Self-rescue devices; high-voltage longwall systems. reduces paperwork burden. It also use and location requirements. Existing Currently, longwall mining is permitted reduces the time and cost to all parties under MSHA’s existing standards only associated with the petition for § 75.400—Accumulation of combustible if it uses low- or medium-voltage modification process. This final rule is materials—provides protection against electrical power. High-voltage longwall implemented in conjunction with float coal dust and § 75.402—Rock systems are being used, but only when revisions to 30 CFR part 18, that address dusting—requires adequate rockdusting approved by MSHA through the petition approval requirements for high-voltage measures. MSHA continues to work on for modification process under § 101(c) equipment. The additional requirements improved respirable dust protection of the Federal Mine Safety and Health under 30 CFR part 18 are also consistent requirements in response to Act of 1977 (Mine Act). During the last with advances in mine technology, recommendations made by the Secretary 15 years, MSHA has evaluated the safe allowing high-voltage switchgear to be of Labor’s Advisory Committee on the use of high-voltage longwall equipment, used on face equipment with enhanced Elimination of Pneumoconiosis Among under a petition process that permits a safety protection from fire, explosion Coal Mine Workers. mine operator to request that the and shock hazards. MSHA is aware that several granted application of a safety standard be MSHA received comments from all modifications for high-voltage longwalls modified at a particular mine. MSHA segments of the mining community. contain non-electrical requirements grants a petition when it determines that Comments from labor, industry and specific to the affected mine. These a mine operator has an alternative manufacturers generally agree with the requirements are the result of settlement method which provides the same proposed rule. The final rule, to the negotiations arising out of the petition measure of safety protection as the extent feasible and appropriate, process and are not required as part of existing standard, or when the existing responds to commenters’ concerns and this electrical standard. Parties to the standard would result in diminished reflects general consensus of various current petition process may, through a safety protection to miners. Over the parties. However, MSHA did not adopt voluntary, cooperative effort, continue past 15 years, MSHA has granted over all comments received. to follow the non-electrical provisions 100 petitions for modification to use Joint commenters representing both after this final rule becomes effective. high-voltage electrical power with industry and labor recommended that Moreover, as indicated above, existing longwalls. In the Agency’s evaluation of operators mining under granted high- and new standards substantially address the use of high-voltage longwall mining voltage petitions containing non- these concerns and result in no systems, MSHA concluded that they can electrical provisions continue to comply diminution of safety and health be safely used, provided that certain with such provisions. Labor protection currently afforded to miners. conditions are met. Specifically, the commenters requested that standards Moreover, the Agency continually Agency found that the previous safety addressing high-voltage longwalls also reviews existing standards for
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improvements that will enhance miner nonconductive insulating board. These case. The shearer is not required under safety. requirements protect against shock § 18.53(f) to have a disconnect switch. Some commenters suggested that the hazards which may arise from Therefore, in an effort to address this final rule allow a longer phase-in inadvertent contact with energized high- issue, the final rule has been modified period, where equipment modifications voltage circuits. With the exception of a exempting the requirements of are necessary. The Agency does not controller on a shearer, compliance with paragraph (a) when applied to a shearer. believe that a delayed effective date is this section requires the components One commenter recommended that necessary. Many operators are already within each high-voltage motor-starter the term ‘‘location’’ be deleted from the complying with these requirements enclosure be segregated into separate final rule, suggesting that there must be under the petition for modification compartments by voltage classification. a physical separation within process and the modern technology The installation of the barriers and compartments to prevent accidental necessary to implement the final rule is partitions provides separation of contact with a high-voltage circuit while readily available. components in each high-voltage motor- troubleshooting low- and medium- starter enclosure. When complete voltage circuits. Another commenter II. Discussion of Final Rule separation of voltage classifications is proposed the use of separate The following section-by-section not possible with barriers or partitions compartments having explosion-proof portion of the preamble discusses each where both medium- and high-voltage walls between one compartment and the provision affected, starting with the circuits or both low- and high-voltage next. As noted in the proposed rule, the provisions in part 18. The text of the circuits are connected to a component intent of this provision is to minimize final rule is included at the end of the or device, that component is required to shock hazards by preventing exposure document. be located in the motor contactor or of personnel to high-voltage Part 18 Electric Motor-Driven Mine disconnect device compartment. components when troubleshooting and This rule covers both explosion-proof testing low- and medium-voltage Equipment and Accessories and nonexplosion-proof motor-starter circuits in accordance with § 75.820. This final rule addresses only those enclosures that are presently used by MSHA believes that this can be areas where specific additions to 30 CFR the mining industry. MSHA’s policy has accomplished by various types of part 18 are necessary for the approval of been to require barriers and partitions to partitions or barriers, including high-voltage longwalls. The existing separate the disconnect device designing the enclosure into several requirements of 30 CFR part 18 that compartment, control/communications separate explosion-proof compartments. apply to this equipment have not been compartment and motor contactor When designing the partitions or revised. Examples of these types of compartment in both power centers and barriers, however, consideration should requirements are the general motor-starter enclosures. If a motor- be given to possible effects of pressure- construction requirements of the high- starter enclosure is part of a power piling within the enclosure. The use of voltage enclosures and the short-circuit center, then the partitions and barriers the word ‘‘location’’, in the proposed and overload protection to be provided. required by this rule only apply to rule allowed the option of having The overload and short-circuit barriers and partitions for the separate enclosures to house the various protective device settings were not disconnect device compartment, compartments, as noted by the revised and will continue to be control/communications compartment, commenter. In response to these evaluated under existing requirements and motor-starter compartment of the comments, the final rule removes the and Agency policy. power center. This rule does not apply word ‘‘location’’ to provide for The main safety protections addressed to other parts of the power center or to flexibility, but clarifies that the in the final rule are summarized into separate power centers that supply requirement applies to each motor- four areas: (1) Prevention of a high- power to motor-starter enclosures. The starter enclosure. voltage arc from occurring; (2) mining industry presently provides Comments were also received Prevention of the resulting heat or flame barriers for power centers to separate suggesting that we change the word from igniting a methane-air mixture high-voltage components from low- and ‘‘board’’ to ‘‘material’’ in regard to surrounding the machine if an arc or medium-voltage circuits and equipment. construction of barriers and partitions. methane explosion occurs; (3) MSHA encourages the industry to Since the word ‘‘board’’ suggests a more Prevention of enclosure failure from an continue to provide barriers and sturdy barrier than ‘‘material,’’ the final increased pressure rise if an arc or partitions in power centers to minimize rule remains as proposed. methane explosion occurs within the shock hazards by limiting exposure of Paragraph (b) of the final rule, like the explosion-proof enclosure; and, (4) personnel to high-voltage components proposed rule, requires motor-starter Personal protection for miners from when troubleshooting and testing low- enclosure compartment(s) containing electrical shock hazards when working and medium-voltage circuits. If barriers high-voltage components be provided in or around the high-voltage and partitions are not provided on with cover interlock switches. These equipment. power centers, the power center must be interlock switches will protect miners deenergized from an outby set of high- entering enclosures from shock hazards Section 18.53 High Voltage Longwall voltage visible disconnects and the resulting from accidental contact with Mining Systems (Nameplate Ratings high-voltage circuit grounded before energized circuits. A minimum of two From 1,001 Volts Through 4,160 Volts) troubleshooting and testing is performed interlock switches per cover is required Paragraph (a) of this final rule on low- or medium-voltage circuits or and must be wired into the circuitry so requires the separation of compartments equipment in the same compartment that operation of either switch will containing low- and medium-voltage with high-voltage circuits or equipment. deenergize the incoming high-voltage circuits from those with high-voltage Commenters suggested that, because circuits. The Agency believes that a circuits in each motor-starter enclosure of overall machine design second switch coupled with required by location, partitions or barriers. considerations, an exception be maintenance under 30 CFR 75.512 will Partitions and barriers, under this final provided for the controller on a shearer. provide the necessary protection to rule, like the proposed rule, are required In response to this comment, MSHA ensure that the high-voltage circuits are to be constructed of grounded metal or acknowledges that a shearer is a special deenergized whenever a cover is
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removed. MSHA recommends either a windings. Compliance with this dangerous practice to test ground-fault magnetic or a whisker-type switch. provision protects against shock hazards protection by making direct connections MSHA’s follow-up inspections of high- should a fault develop between the between phase and ground, and stated voltage equipment with plunger- primary and secondary windings. that MSHA should establish a policy on operated switches reveal that these Faraday shielding provides electrical this so that the matter is resolved. switches may stick and not operate isolation between the high-voltage In response to these comments, unlike effectively after exposure to the mine primary and low-voltage secondary the proposed rule, the final rule environment. windings of these transformers. As a includes a requirement that each This rule covers both explosion-proof secondary benefit, Faraday shielding of ground-fault test circuit be designed to and nonexplosion-proof high-voltage control transformers assures that inject a primary current of 50 percent or motor-starter enclosures. MSHA’s high- transients occurring on the primary less of the maximum ground-fault voltage longwall petitions require circuit are not transferred to the current through the current transformer interlock switches for high-voltage secondary circuit. Such transients could to cause the corresponding circuit- compartments in both power centers cause premature damage to electrical interrupting device to open. This and motor-starter enclosures. When a control equipment and create an requirement is necessary to reduce the motor-starter enclosure is part of a economic burden for the mining likelihood of a hazardous condition power center, the interlock switches industry. resulting from a phase-to-ground fault. required by this rule only apply to This rule requires Faraday shielding A similar requirement is added to the motor-starter compartments of the for control transformers located in both final rule under 30 CFR 75.814(c). power center. This rule does not apply explosion-proof and nonexplosion-proof Paragraph (f) of the final rule requires to other parts of the power center or to motor-starter enclosures that are each longwall motor-starter enclosure, separate power centers that supply presently used by the mining industry. with the exception of a controller on a power to motor-starter enclosures. The Also, this rule requires Faraday shearer, to be equipped with a mining industry presently provides shielding for control transformers that disconnect device. Opening of the interlock switches for high-voltage supply motor-starter compartments, device deenergizes all high-voltage compartments on power centers. MSHA even if the control transformer is located power conductors extending from the encourages the industry to continue to in a separate power center. This rule enclosure, except the conductors provide interlocks switches for high- does not cover control transformers for supplying power to the enclosure. voltage compartments of power centers. power centers that do not supply power Compliance with this paragraph There were no comments on this to the motor-starter enclosure. provides for convenient and safe paragraph. However, the last sentence of Paragraph (d) also requires the deenergization of high-voltage circuits the proposed rule was deleted to clarify secondary nominal voltage of the and other components during testing the Agency’s intent that at least two control transformer be no more than 120 and troubleshooting work, thus switches be used to satisfy 30 CFR part volts, line-to-line. This is consistent 18.53 (b) requirements. with the existing policy interpretation of minimizing shock hazards. Paragraph (c) of the final rule, like the 30 CFR part 18 control voltage A joint industry commenter suggested proposed rule, requires that circuit- limitations under § 18.47. There were no that the word ‘‘incoming’’ be inserted interrupting devices installed in motor- comments on this paragraph and before the phrase ‘‘disconnect device’’. starter enclosures be designed and therefore, the wording remains the same MSHA believes this is implied, since installed to prevent automatic reclosure. as the proposed rule. the device must deenergize all high- Compliance with this provision protects Paragraph (e) of the final rule, like the voltage power conductors extending miners working on the circuit or in proposed rule, requires test circuits to from the enclosure. Therefore, the other hazardous situations from verify the integrity and proper operation language of final rule remains as unanticipated reenergization of the of the ground-wire monitors and proposed. circuit. For example, faults occur in ground-fault protective devices. Test Paragraph (f)(1) of the final rule, like underground electrical systems as a circuits for ground-wire monitors and the proposed rule, specifies that a single result of roof fall damage or equipment ground-fault circuits assure that the handle provide for simultaneous insulation failure. Under such circuits can be tested frequently in a operation through a mechanical circumstances, the use of automatic manner that minimizes the hazards to connection of multiple switches located reclosing circuit-interrupting devices personnel conducting the tests. within an enclosure. The simultaneous would create shock and fire hazards Incorporating these test circuits into the operation of multiple disconnect should the devices reclose automatically longwall circuitry eliminates the need to devices by the use of a single handle when a short-circuit or ground-fault test these protective devices by other ensures that all high-voltage conductors condition exists in the circuit. There means that could result in a shock extending from the enclosure are were no comments on this paragraph. hazard by placing personnel in close deenergized when the disconnect device Therefore, the language in the final rule proximity to exposed energized is in the open position. This has not been changed from the proposed conductors. arrangement ensures that personnel rule. Some commenters noted that the entering other enclosures are protected Paragraph (d) of the final rule, like the testing of backup ground-fault devices from a shock hazard resulting from proposed rule, specifies that control located across the grounding resistor accidental contact with energized transformers installed in each longwall would require the application of an circuits in the event the wrong circuit is motor-starter enclosure or control actual phase-to-ground fault, which disconnected. transformers that supply control power could be hazardous. These commenters The words ‘‘isolator switch’’ and to each longwall motor-starter suggested that the ground-fault test ‘‘switches’’ were removed in the final enclosure, must have electrostatic circuit inject a primary current into the rule to minimize confusion. There were (Faraday) shielding, grounded by at transformer and not subject the no comments on this paragraph and the least a No. 12 American Wire Gauge equipment to an actual phase-to-ground language in the proposed rule remains (AWG) grounding conductor, installed fault. In addition, another commenter unchanged except for the above between the primary and secondary supported the opinion that it is a clarifications.
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Paragraph (f)(2) of the final rule, like and motor-starter enclosures. If a motor- requirement that neither the main the proposed rule, further defines the starter enclosure is part of a power circuit-interrupting device nor the requirements of a disconnect device. center, then this rule covers the power disconnect device can be closed without The switch must be rated for the center. This rule does not apply to deenergizing the incoming high-voltage maximum phase-to-phase circuit voltage separate power centers that supply circuit unless the auxiliary test switch is of the system. The ability to verify, by power to motor-starter enclosures. The in the normal operating position, has visual observation, that the switch’s mining industry presently provides this been replaced with a requirement which contacts are opened is also required. interlocking of the disconnect device for more clearly states the expected This verification must be determined power centers. MSHA encourages the performance of the control interlock without the removal of any enclosure industry to continue to interlock circuit. The final rule requires high- cover. The removal of an enclosure disconnects with the control circuits to voltage control circuits to be interlocked cover to verify opening of the contacts facilitate troubleshooting and testing so they can be energized only when the presents an increased shock hazard to high-voltage circuits and equipment disconnect switch is either in the miners because of exposed energized while the high-voltage circuits are ‘‘closed’’ or the ‘‘open and grounded’’ high-voltage components. disconnected. This maintains the positions. High-voltage control circuits Also included under this paragraph existing level of protection because the may not be operated in any other are the requirements that all load-side interlock disconnects provide an intermediate positions of the disconnect power conductors be grounded and the additional safeguard against inadvertent switch or auxiliary switch. This device be provided with a means to be exposure to energized high-voltage requirement will prevent unintentional locked when the device is in the ‘‘open’’ circuits. energization of high-voltage position. These requirements guard One commenter noted that the components. The control circuit can be against the hazard of maintenance proposed rule calls for deenergizing the energized only when the disconnect personnel being exposed to high-voltage incoming high-voltage circuit if the switch is ‘‘open and grounded’’ with the energized parts due to residual voltage normal/test auxiliary switch is not in auxiliary switch in the ‘‘test’’ position, or inadvertent energization of the the normal position while closing the or when it is closed with the auxiliary circuit. main circuit-interrupting device and the switch in the ‘‘normal’’ position. MSHA The final requirements of this disconnect device (isolator switch). This has not included language in this paragraph address the interrupting commenter stated that this requirement paragraph to specifically exclude the capability of the disconnect device. A would necessitate a retrofit in existing controller on a shearer from these disconnect device installed in an longwall controllers since the normal/ interlock requirements, as suggested by explosion-proof enclosure must be test switch must be in the normal some commenters. Shearers are not designed and installed to cause the position when the disconnect switch is required to be equipped with a current to be interrupted automatically closed in order for the control circuit to disconnect device as stated in § 18.53(f) prior to the opening of the device. This function at all. This would prohibit the of this final rule and MSHA does not requirement addresses the concern closing of the circuit-interrupting device intend that this provision be applicable about an explosion-proof enclosure and would disable the control circuitry. to shearers. Therefore, except for the failure because of an increased pressure With the disconnect device in the open/ above stated clarifications, the final rule rise. This pressure rise can result when grounded position, the test circuitry remains as proposed. an arc or methane explosion occurs cannot be used unless the normal/test Paragraph (h) of the final rule requires within the explosion-proof enclosure. switch is in the test position. The that the electrical protection be set at an When the enclosure is not explosion- commenter further indicated that, in appropriate value to provide protection proof, as in outby switching, the device either case, the incoming high voltage for the size and length of the longwall is required to either be installed in the does not present a hazard. motor and shearer cable used, based on circuit so that the circuit is Other commenters recommended that an ‘‘available fault current’’ study that automatically interrupted prior to the the control circuits within each high- must be submitted to MSHA. Proper opening of the device or the device is voltage motor-starter enclosure be electrical protection is essential in required to be capable of interrupting interlocked with the disconnect device, preventing a fire, explosion or shock the full-load current of the circuit. There except for the controller on a shearer, so hazard resulting from inadequate sizing were no comments on this paragraph that the control circuit can be powered of electrical cables. and the language in the proposed rule with an auxiliary test switch when the Appendix I of existing 30 CFR part 18 remains unchanged in the final rule. disconnect device is in the open and includes maximum trailing cable Paragraph (g) of the final rule grounded position; and the disconnect protective device settings and trailing addresses the interlocking of the device cannot be closed without de- cable length restrictions as specified in disconnect device. These interlocking energizing the incoming high-voltage Table 8 and in Table 9. These have, in requirements reduce shock hazards by circuit unless the auxiliary test switch is the past, been used as guidance in increasing the probability that the high- in the normal operating position. These evaluating cables on longwalls rated at voltage circuits will be isolated and commenters stated that, in many cases, less than 1,000 volts. Under this final deenergized prior to performing testing it is necessary to close the main circuit- rule and consistent with agency policy, and troubleshooting on the low- and interrupting device with the auxiliary the length restrictions and device medium-voltage circuits and ensure that switch in the test position. settings do not apply to high-voltage high-voltage circuits may only be MSHA has carefully reviewed and longwall motor and shearer cables. The energized at the proper time following considered these comments. The final procedures used in evaluating high- this activity. rule retains the requirement that the voltage longwalls cables and settings This rule covers both explosion-proof control circuit for high-voltage motor- include a review of the applicant’s fault- and nonexplosion-proof motor-starter starters can only be energized through current study to determine the enclosures that are presently used by an auxiliary test switch when the minimum expected short-circuit the mining industry. MSHA’s policy has disconnect switch is open and the load currents available at the farthest been to interlock disconnects with the power conductors of the high-voltage projected installation in the electrical control circuit in both power centers circuit are grounded. The proposed system.
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This paragraph of the final rule has achieved because the phase-to-ground tripping. This scheme is widely used in been clarified, in response to a proposed short-circuit currents, unlike the phase- mining at all voltages. Requiring all 1989 electrical rule comment, to to-phase short-circuit currents that may three phase conductors to be encircled indicate that trailing cables would also flow from faults in other cable by the CT prohibits the equipment be included in the required evaluation constructions, are limited in magnitude safety grounding conductors from to ensure adequate protection for the by the grounding circuit components. passing through or being connected in length and conductor size of all cables, Some commenters suggested that series with the CT. If the safety including longwall motor, shearer and these cables should be assembled with grounding conductor passes through or trailing cables. However, MSHA does a grounded shield around each power is connected in series with the CT, it is not intend to specify a fixed maximum conductor but that the shield should not possible for the fault currents to flow setting for short-circuit protective be specified as metallic since these through parallel paths, thereby reducing devices, as noted by the commenter. power systems restrict ground-fault the reliability of the ground fault MSHA intends to be flexible by current to reduced values and the cables protection. assessing each installation individually. are constantly flexed. They believed that Some commenters suggested that if The submitted fault study is the basis in an improved cable could be developed the full-load current of the circuit determining the settings, and for with a nonmetallic shielding material exceeds 200 amperes, the instantaneous permitting higher trailing cable circuit around each power conductor. In ground-fault protection be set at not protective device settings and cable response to this comment, MSHA more than 0.200-amperes. They stated lengths than specified by 30 CFR part believes that this technology has not that it is very difficult to produce 18. MSHA recognizes that it is practical been demonstrated or shown to provide ground-fault current transformers that to design longwall systems with higher equivalent safety in underground coal can reliably discriminate between small circuit protective device settings and mines. Although MSHA supports the ground-fault currents and larger motor longer cable lengths in order to lessen application of new technology, starting currents and that when the full- economic burdens on the mining questions such as splicing reliability load current of a circuit exceeds 200 community while preserving safety and would need to be addressed before amperes, it is reasonable to expect health protections for miners. Some incorporating these types of cables on motor starting currents in excess of commenters noted that the fault study is longwalls. If a reliable system using this 2,000 amperes. They asserted that a unique to each mine and that this type of cable were developed and small increase in the setting of the requirement should not be included in equivalent safety were demonstrated, it ground-fault protection is justified for 30 CFR part 18. They suggested that the could be addressed under existing certain high-current circuits and that the regulation is more suitable for inclusion §§ 18.20(b)—Quality of material, suggested 0.200-ampere setting would in part 75. MSHA disagrees. In order for workmanship, and design and/or still be less than 40 percent of the a longwall mining system to be safely 18.47(d)(6)—Voltage limitation through maximum ground-fault current. They designed, the designer must know the the construction and design noted that the specification of the parameters under which the longwall requirements for MSHA approval. The current transformers is very rigid and will be operated. These parameters final rule has not been modified, as stated that the regulation should allow would include available fault currents. suggested by commenters, and remains for new technology if it can provide The final rule requires that this as proposed. equal or improved protection. In Paragraph (j) of the final rule specifies relation to ground-fault protection, a information be provided to MSHA to that high-voltage motor and shearer commenter focused on MSHA’s determine whether cables are circuits be provided with instantaneous statement that zero sequence type adequately protected. Historically, ground-fault protection set at not more relaying ‘‘is not affected by CT error.’’ longwalls are custom-made systems and than 0.125-amperes. The current The commenters stated that, in their are not designed for more than one transformers (CT) used for ground-fault experience, erroneous signals are mining company. The fault study protection are required to be of the produced in the CT’s if the current should take into account worst-case single window-type and installed to levels are sufficiently high. They noted projections (i.e., longest cable lengths, encircle all three phase conductors. This that when starting currents flowing in smallest Kilo-Volt Amperes (KVA) will provide highly sensitive and the power circuit are in excess of 2000A Power Center). Enforcement personnel responsive ground-fault detection it is possible that an ‘‘error current’’ will also use this information to ensure systems, using new technology such as exceeding 100mA may be fed to the compliance with § 75.518–1—Electric solid state relays, for high-voltage relay, causing nuisance tripping. For equipment and circuits; overload and circuits supplying electric face this reason, it is their belief that the short circuit protection; minimum equipment. The protective devices are relays on the power center output cables requirements. Except as clarified above, required to operate instantaneously to the longwall controls are now set to the final rule remains as proposed. when exposed to ground faults that a higher current of 200–300mA and Paragraph (i) of the final rule requires exceed the trip setting of the ground- these cables carry the combined starting all longwall motor and shearer cables fault protective device. Therefore, currents of two or three motors. They with nominal voltages greater than 660 compliance with this standard will concluded that as a result, when the size volts to have a cable construction with greatly reduce the likelihood of fires and of individual motors gets larger, this a grounded metallic shield around each shock hazards that result from ground problem will be experienced on motor power conductor. This regulation faults on the high-voltage circuits or cables. requires the incorporation of the equipment. MSHA has reviewed these issues and grounded shield around each power The use of the single window-type determined that reliable, sensitive conductor providing additional current transformer encircling all three ground-fault protective devices are personnel protection against shock and phase conductors is the most reliable commercially available and that they electrocution hazards. This is necessary method for detection of ground faults in have been successfully used to correct because any cable faults would cause mine power systems. This type of the problems described by the phase-to-ground short-circuit currents to relaying (zero-sequence) is not affected commenters. These devices can safely flow. An extra level of protection is by CT error and gives very sensitive and reliably operate at 0.125-ampere or
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less. The use of a single window-type pressure). The final rule’s performance- included in this section. The required current transformer to encircle only the oriented language permits compliance creepage distances are determined based three phase conductors assures that through any achievable means. upon the phase-to-phase use voltage and sensitive ground-fault devices will Protective methods used in previously the CTI of the insulation to be used. detect all ground faults exceeding the issued approvals and experimental Creepage distance is based in part on setting of the device. Detection devices permits consisted of electrical devices the CTI of the electrical insulating inserted in the ground wire may not with rapid clearing times. However, the material. An appropriate method of detect all ground-fault currents and rule provides for flexibility and permits determining the CTI of the electrical could compromise the integrity of the alternative methods that may provide insulating material is described in the ground circuit. Therefore, the final rule equal protection, such as pressure American Society for Testing and has not been modified and remains as switches or special pressure release Materials Standard, ASTM D3638 proposed. devices. There were no comments on ‘‘Standard Test Method For Paragraph (k) of the final rule, like the this paragraph. The final rule remains as Comparative Tracking Index of proposed rule, requires safeguards proposed. Electrical Insulating Materials.’’ The against corona to be provided on all Paragraph (m) of the final rule, like MSHA derived creepage distances in the 4,160 volt circuits in explosion-proof the proposed rule, requires that high- table are consistent with most enclosures. Corona is a luminous voltage electrical components located in commercially available high-voltage discharge that occurs around electrical high-voltage explosion-proof enclosures components to which this provision conductors that are subject to high cannot be coplanar with a single-plane applies. There were no comments on electrical stress. One danger inherent flame-arresting path. This protective this paragraph. The final rule remains as with high-voltage equipment is that measure will further prevent the heat or proposed. excessive electrical stress can cause flame from an arc or methane explosion Paragraph (o) of the final rule premature breakdown of insulating in an explosion-proof enclosure from addresses a requirement for Minimum materials, which could result in arcing, igniting a methane-air mixture Free Distance (MFD) within an thus creating an explosion hazard in the surrounding the enclosure. This explosion-proof motor-starter enclosure. presence of corona. Corona usually requirement addresses the possibility of MSHA’s Internal Engineering Report doesn’t present a hazard until voltage of conductor material particles being Number 87021701 (available in the 8kV are reached. However, even at 4,160 expelled from the enclosure through the rulemaking record) determined that if volts, safeguards should be taken. This flame-arresting path. Particles of molten phase-to-phase arcing occurred, there would include using cables with a material are emitted from the may be adequate arc energy to heat the corona resistant insulation such as conductors whenever a short-circuit walls of the enclosure beyond the safe ethylene propylene, to avoid small nicks occurs. Expulsion of these particles working temperature. This could cause or cuts in the cable insulation and to from the enclosure can occur if their failure of the enclosure and create an minimize high-voltage transients. This source is in the same plane as the flame- explosion hazard. Distances between the provision is not intended to require arresting path and a pressure rise wall or cover of an enclosure and stress cones or similar termination coincides with the short circuit. Once uninsulated electrical conductors inside schemes. There were no comments on these particles are expelled from the the enclosure were established to this paragraph. The final rule has not explosion-proof enclosure, they can prevent wall or cover damage from been modified and remains as proposed. ignite an explosive atmosphere should phase-to-phase arcing. Paragraph (l) of the final rule, like the one be present. This possibility does not Some commenters suggested that the proposed rule, requires limiting the arise with multi-plane flame-arresting last sentence of the proposed paragraph maximum explosion pressure rise path surfaces because a deflection in the (o) be revised as follows: ‘‘If a grounded within an enclosure to 0.83 times the path would prevent ignitions by 1⁄4-inch thick steel shield is installed design pressure for any explosion-proof expelled particles. There were no between the area of potential arcing and enclosure containing high-voltage comments on this paragraph. The final the adjacent wall/cover area, the switchgear. This requirement protects rule remains as proposed. minimum free distance requirement is against explosion hazards that may arise Paragraph (n) of the final rule, like the satisfied.’’ MSHA believes that this from the effects of a sustained high- proposed rule, addresses MSHA’s comment was based on a footnote voltage arcing fault. This arcing fault concern with the decomposition of present in the part 18 approval criteria may significantly contribute to the insulating materials due to tracking. In established by MSHA for high-voltage pressure rise created in an explosion- the presence of surface contaminants, equipment containing on-board proof enclosure during an internal small levels of current can flow between switching of high-voltage circuitry. This methane-air explosion. Research conductors. As the currents flow, the criteria indicates that the specified conducted by the former U.S. Bureau of insulation may carbonize and produce MFDs may be reduced if a 1⁄4″ thick Mines and MSHA on effects of high- conducting tracks. The conducting steel shield is used between the area of voltage arcing in explosion-proof tracks may grow progressively across potential arcing and the adjacent wall/ enclosures concluded that this potential the surface eventually bridging between cover area. Since this footnote did not increased pressure rise can be safely conductors and causing complete cite a MFD or qualify the circumstances addressed through a combination of breakdown. Using insulation with an under which this shield could be used, designing the enclosure for the adequate Comparative Tracking Index MSHA did clarify this criteria exception increased pressure and providing (CTI) rating can prevent tracking, thus in the proposed rule, and the final rule electrical protective devices set to minimizing potential arcing that could remains unchanged with respect to this deenergize the incoming circuit before lead to an explosion hazard. Paragraph clarification. A commenter also stated the pressure rise becomes excessive. (n) requires that rigid insulation that a steel shield could be mounted in This provision requires that the between high-voltage terminals or conjunction with an aluminum wall or maximum explosion pressure rise must between high-voltage terminals and cover to reduce the required minimum be limited to a value that can be safely ground be designed with creepage free distance and that the thickness of contained within the explosion-proof distances in accordance with the table this steel shield would be used to enclosure (83 percent of the design labeled ‘‘Minimum Creepage Distances’’ determine the required minimum free
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distance. MSHA has determined that a warranted, under §§ 18.20(b) and/or not exhibit leakage through welds or 1⁄4″ thick steel shield, mounted to 18.47(d)(6). MSHA intentionally casting or rupture of any part that affects maintain a minimum electrical omitted the MFD value for a 1″ thick the explosion-proof integrity of the clearance, as suggested by the steel wall/cover under Column A to enclosure. Further, the enclosure, commenter, would not provide minimize confusion. MSHA calculated following removal of the pressurizing sufficient protection if a phase-to-phase this value to be 0.3″, which is less than agents, must not exhibit visible cracks arc occurred. The final rule also permits the minimum electrical clearance that in welds, permanent deformation the use of steel shields greater than 1⁄4″ must be maintained under § 18.24 for exceeding 0.040 inches per linear foot, thick to provide for flexibility and high-voltage equipment. As indicated or excessive clearances along flame- diversification in enclosure design. above, the proposed rule has been arresting paths following retightening of Some commenters noted that the modified in part, and adopted in part. fastenings, as necessary. Any of the proposed regulation classified all Paragraph (p) of the final rule, like the above conditions would constitute enclosures in one of two groups: those proposed rule, requires a static pressure unacceptable performance. with short-circuit currents less than test to be performed on each prototype There were no comments on this 10,000 amperes and those with short- design of explosion-proof enclosure paragraph. However, the final rule is circuit currents between 10,000 and housing high-voltage switchgear prior to modified to clearly state the type and 20,000 amperes. It was their view that explosion tests. The manufacturer is nature of quality assurance inspections because of the substantial increase in also required to use this test as a routine that qualify as an MSHA accepted minimum free distance between these test on every explosion-proof enclosure quality assurance procedure. groups, MSHA should permit a housing high-voltage switchgear, at the manufacturer to calculate the time of manufacture, or follow an Part 75 Mandatory Safety Standards— appropriate MFD when the short circuit MSHA accepted quality assurance Underground Coal Mines current is between 10,000 amperes and procedure covering the inspection of the The final rule revises existing 20,000 amperes. They also enclosure. These quality assurance standard § 75.1002—Location of trolley recommended that MSHA include a procedures must include a detailed wires, trolley feeder wires, high-voltage provision that would permit the check of parts against the drawings to cables and transformers, and adds minimum free distances to be revised determine: (1) That the parts and the §§ 75.813 through 75.822 to set out based on future research in this area. drawings coincide and (2) that the additional safety precautions that allow Finally, they noted that the MFD for a minimum requirements stated in 30 the use of available technology. These 1-inch thick cover under Column A was CFR part 18 have been followed with new safety precautions address the use omitted. respect to materials, dimensions, of high-voltage longwall equipment in In response to these comments, configuration and workmanship. face (production) areas. As stated MSHA has revised the Minimum Free MSHA is concerned about the earlier, MSHA previously included Distance Table by adding minimum free specified design pressure of an these safety precautions in petitions distance information for short-circuit enclosure. Presently, an enclosure that granted for § 75.1002. Based on its currents of 15,000 amperes. is designed for 150 pounds per square experience with petitions for Additionally under the final rule in inch gauge (PSIG) is tested with a modification, the agency expects the paragraph (o)(1), MSHA allows for methane explosion. Normally, these final rule to improve safety for values not presented in the table pressures do not exceed 100 pounds per underground coal mining. provided that they meet the specific square inch (PSI). Since the protective Under the final rule, the risk of injury engineering formulas on which the table method to prevent over-pressurization related to lifting and handling of cables is based. These formulas were in these enclosures would be directly should be reduced since the use of high- developed by MSHA engineers with related to the design pressure, MSHA voltage cables can reduce the weight standard engineering calculations using has developed the static pressure test and size of a cable used in longwall face data obtained from high-energy arc with its acceptable performance criteria systems. testing. This testing was performed to ensure each enclosure design would The final rule also provides the during Foster-Miller research, under be capable of withstanding its design following protection against fire, USBM Contract No. H0308093. The pressure. By requiring static pressure explosions, and/or shock hazards: MSHA research reports and data are testing on each enclosure prototype, (1) Improved short-circuit and ground part of the rulemaking record and are MSHA believes that the adequacy of fault protection; available for review. enclosure design would be verified. (2) A means to easily test the Equipment approved under these Additionally, to require either effectiveness of ground fault protection; circumstances will be limited to subsequent static pressure testing on (3) Use of manufactured cable support equipment used only with power each enclosure manufactured or an systems for cables extending from the systems that do not generate short- acceptable quality assurance program power center to the headgate; circuit currents that exceed the design guarantees the integrity of later (4) Use of insulated cable-handling parameters used for establishing manufactured units. equipment; minimum free distance. In addition, The static test procedure specifies that (5) Use of protective gloves to MSHA will consider the use of shields the enclosure be internally pressurized troubleshoot and test low- and medium- constructed with alternate materials and to a pressure no less than the design voltage circuits associated with high- the use of alternate techniques and pressure, with the pressure maintained voltage circuits; methods that preclude the possibility of for a minimum of 10 seconds. Following (6) Use of additional protection for high-energy arcs heating the walls of the pressure hold, the pressure is cables at points where cables leave explosion-proof enclosures beyond safe removed and the pressurizing agent support systems; working temperatures. If upon removed from the enclosure. (7) Use of more improved ‘‘quick evaluation, equivalent safety is Acceptable performance criteria are handle’’ disconnect devices for the demonstrated, MSHA will address these provided in this final rule. Acceptable purpose of performing work; and technological advances and the results performance is achieved if the (8) The use of barriers and interlock of additional research in this area, if enclosure, during pressurization, does switches to help guard against contact
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with energized circuits. The final rule be used without increasing voltage representatives were sent copies of these requires the use of cables containing levels which helps minimize cable over- proposed definitions as part of the metallic shielding (SHD) around each heating and reduces cable insulation complete longwall high-voltage power conductor. deterioration. Multiple parallel circuits proposed rule. There were no comments Many of these final rule safety in these systems are a logical option that opposing this approach. improvements are required conditions resulted from this high-voltage longwall The definitions are derived from for granted modifications of § 75.1002. petition experience. As noted above, consensus standards, including the However the final rule, like the industry and labor suggested multiple Institute of Electronic and Electrical proposed rule, provides two additional parallel circuit use during the Engineers, The New Standards requirements. These are gloves for rulemaking comment process. Dictionary of Electrical and Electronics troubleshooting and testing, and test Section 75.822 allows the use of high- Terms—Standard 100–1992, and the circuits for ground-fault protection. voltage longwall cables with a minimum National Electrical Code (NEC). The final rule, in response to No. 16 AWG center ground-monitor Definitions found in 30 CFR part 18 of commenters’ suggestions, also provides conductor. This provision eliminates MSHA’s regulations were also used as a two provisions not included in the the need for petitions for modification source for this final rule. In some proposed rule, §§ 75.814(e) and 75.822. of § 75.804(a). It allows the use of instances, definitions taken from these Section 75.814(e) requires a single improved high-voltage cable designs sources were changed to apply to circuit interrupting device for cables that provide increased protection electric circuits and equipment used in connected in parallel or permits parallel against fire and shock hazards. It the coal mining industry. circuits-interrupting devices to protect reduces inter-machine arcing from MSHA proposed that the term parallel cables when the parallel circuit- induced currents which can result in an ‘‘adequate interrupting capacity’’ be interrupting devices are electrically and ignition hazard. The cable designs were defined as the ability of an electrical mechanically interlocked. Section initially developed for high-voltage protective device to safely interrupt all 75.822 allows the use of No. 16 AWG longwall equipment under previously values of current which can occur at its ground-monitor conductors. These granted petitions. location in excess of its trip setting or additional provisions are a logical The cable design requirements were melting point. A commenter suggested outgrowth of the proposed rule and also requested by labor and industry that this term be defined as the ability notice and comment process, reflecting during the comment period of the of an electrical protective device, based the primary purpose of the proposed proposed rule. Since 1992, under upon its required and intended rule by allowing the use of high voltage MSHA-approved petitions, these cable application, to safely interrupt values of on longwalls in a safe and efficient designs have been safely used. current in excess of its trip setting or manner. The new provisions are in These new requirements not only melting point. MSHA agrees and has response to specific joint industry and permit multiple parallel cable use and changed the proposed definition to labor comments received about parallel the use of No. 16 AWG ground-monitor reflect this suggestion. This commenter circuit use, and industry comments conductors but also minimize industry suggested that the proposed definition about the size of ground-check paperwork requirements. With this new would cause a problem, since in motor- conductors. These additional provisions technology, the final rule results in starter enclosures of the type presently permit the use of high-voltage longwall improved safety and savings for both the used for high-voltage longwalls, short- systems that are safe, effective and mining community and MSHA. Cable circuit protection is provided by a single efficient and reflect the mining replacement and maintenance costs will circuit breaker common to all motor community’s experience with granted be reduced. Also, mine operators will circuits, whereas overload, ground fault, modifications. The ground-monitor not need to file petitions for and ground-monitor protection trips conductor size and the multiple parallel modification; therefore, costs associated individual motor contactors. According circuit provisions are not requirements with the petition process will be to this commenter, this could result in but are offered to give flexibility to mine eliminated. Legal costs are incurred by the interruption of the intended operators to use available technology all segments of the mining community protected circuits at a higher current and to minimize cost burdens where in the administrative review process value than was intended or required for feasible. associated with petitions. Agency costs that circuit, therefore, affording less Section 75.814(e) of the final rule associated with publication, processing, protection against overheating, shock requires that multiple (parallel) circuits investigation and review of high-voltage and fire hazards. The commenter further be protected by a single circuit- longwall petitions will also be suggested that in applying the revised interrupting device rather than parallel eliminated. definition, the short-circuit relay signals connected circuit-interrupting devices, The final rule increases safety the circuit breaker to interrupt the short- except when parallel devices are protections and does not reduce the circuit current, whereas the ground-fault mechanically and electrically protections currently afforded miners. relay signals the contactor to interrupt interlocked. This requirement is based the restricted ground-fault current. on MSHA electrical safety experience, Section 75.2 Definitions Under the final rule, adequate and experience in granting high-voltage The definitions in this section are key interrupting capacity is determined by longwall petitions for modification, and to proper interpretation of the electrical comparing the interrupting rating of the is consistent with requirements under standards. Upon review, the Agency device with the actual characteristics of nationally recognized consensus concluded that these definitions should the circuit to be protected. Thus, standards. Although multiple parallel also be used to describe these terms interruption of the circuit occurs at the circuits are not necessary for safe high- wherever they appear in 30 CFR part 75 current rating required or intended for voltage longwall systems, they do and proposed such an approach. This that circuit rather than all values of present certain safety and cost efficiency approach will provide clarity and current which can occur at its location. advantages to some longwall high- consistency in the use of these terms The final rule defines ‘‘approval voltage systems as demonstrated under where they appear in all underground documentation’’ to mean formal papers MSHA’s and the mining industry’s safety standards. All underground coal issued by the Mine Safety and Health petition experience. Higher currents can mine operators and miners Administration which illustrate and
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describe the complete assembly of operation of equipment. The Agency standard for shearing machines that electrical machinery or accessories that received no comments on this definition have been previously evaluated by have complied with the applicable and it has not been changed. MSHA under part 18, using non-high- approval requirements of 30 CFR part The final rule, like the proposed rule, voltage criteria. However, such an 18. The rule retains the meaning of the defines ‘‘short circuit’’ to mean an exemption would exclude shearing proposed rule but, for clarification abnormal connection of relatively low machines from the general safety purposes, replaces ‘‘formal document’’ impedance, whether made accidentally requirements contained in the final rule. with the words ‘‘formal papers’’ and the or intentionally, between two points of Safety requirements pertaining to verb ‘‘document’’ with the words different potential. There were no electrical work, such as troubleshooting ‘‘describe and illustrate’’. The proposed comments on this definition so it and testing, and installation, language was also changed to accurately remains unchanged. examination and maintenance, contain reflect that ‘‘approval documentation’’ Definitions of low voltage, medium provisions that apply to all equipment refers to those papers that illustrate and voltage, and high voltage were on the high-voltage longwall, including describe equipment meeting the inadvertently included in the proposed shearing machines. Other provisions ‘‘applicable requirements of 30 CFR part rule. No comments were received on relating to disconnect devices and cable 18.’’ This change clarifies that approval these definitions. These terms are handling and support systems are documentation must be submitted defined in existing rules and are not applicable to the equipment they under part 18. MSHA received no addressed in this final rule. address. Therefore, the Agency does not comments in regard to this definition. One commenter suggested that ‘‘cable believe that a general exemption for Like the proposed rule, the final rule handling and support system’’, a phrase shearing machines would promote defines ‘‘circuit-interrupting device’’ as used frequently in § 75.817—Cable safety. a device designed to open and close a handling and support systems, should circuit by nonautomatic means and to be defined. Section 75.817 contains the Section 75.814 Electrical Protection open the circuit automatically at a performance goals that cable handling This section of the final rule is predetermined overcurrent value and support systems must achieve, by derived in part from existing §§ 75.518– without damage to the device when minimizing the possibility of miners 1—Electric equipment and circuits; operated within its rating. The Agency coming into contact with cables and overload and short circuit protection; received no comments on this definition protecting the high-voltage cables from minimum requirements, 75.800—High- and it is unchanged from the proposed damage. The Agency does not believe voltage circuits; circuit breakers, and rule. This definition clarifies that that a definition is necessary for this 75.800–2—Approved circuit schemes circuit-interrupting devices be designed term. Specifically defining a cable and addresses electrical protection for manual closure rather than handling and support system would methods for longwall equipment automatic, to protect against safety limit operator flexibility with respect to supplied by high-voltage systems. The hazards which could result in severe cable handling and support systems that effects of ground faults, electrical arcing, bodily injury and death if unexpected may be designed in the future and heating of conductors, and short circuits automatic energization of equipment provide equal or greater safety can have adverse consequences to the were to occur. Conversely, the device protection. Cable handling and support safety of miners. Effective electrical must be capable of opening the circuit systems are understood by the plain protection for longwall equipment will automatically upon the occurrence of an meaning of the words. reduce the potential for ignitions, fires, and miner exposure to energized electrical fault. The rating of the device Section 75.813 High-Voltage equipment frames. The final rule must be at a value that would protect Longwalls; Scope the device from damage during the incorporates the latest technology and automatic deenergization of the circuit. Section 75.813 describes the scope of provides increased worker protection ‘‘Ground fault or grounded phase’’ is this final rule; it identifies new for high-voltage longwall mining defined to mean an unintentional §§ 75.814 through 75.822 as electrical equipment. connection between an electric circuit standards that apply only to the use of Paragraph (a) of the final rule and the grounding system. MSHA high-voltage longwall circuits and addresses requirements for short-circuit, received no comments on this definition equipment. The final rule, unlike the overload, ground fault, and and it remains unchanged from the proposed rule, expands the scope to undervoltage protection for high-voltage proposed rule. include new § 75.822. As explained cables extending from the section power Like the proposed rule, the final rule below, § 75.822 is included in the final center, the shearer motor cable(s), and defines ‘‘motor-starter enclosure’’ to rule in response to a comment regarding the remaining motor cables. Short- mean an enclosure containing motor the size of ground-monitor conductors circuit and overload protection prevent starting circuits and equipment. This in cables. This provision also eliminates damage to cables and motors due to term describes equipment commonly the need for petitions for modification overheating. Ground-fault protection used to house longwall motor-starting related to ground-monitor conductor minimizes the risk of shock injuries and equipment. No comments were received size. This section also clarifies that all ignition hazards to miners. Under- on this definition and it remains other existing standards in 30 CFR that voltage protective devices prevent unchanged. are applicable to the use of high-voltage automatic restarting of equipment Also like the proposed rule, the final longwall circuits and equipment following a loss of power. rule defines ‘‘nominal voltage’’ to mean continue to apply. For example, safety The final rule also requires circuit- the phase-to-phase or line-to-line root- standards, such as grounding and interrupting devices for high-voltage mean-square value assigned to a circuit ground-monitor requirements contained circuits that supply power to longwall or system to conveniently designate its in subparts H and I of part 75 that are equipment be properly rated to safely voltage class, such as 480 or 4,160 volts. currently applicable to high-voltage interrupt the current to which it may be The definition clarifies that the actual installations are also applicable to high- exposed without damage. The adequacy operating voltage of a system or circuit voltage longwall equipment. of the circuit-interrupting device assures may vary from its nominal voltage Some commenters suggested that an that the device will remain undamaged within a range that permits satisfactory exception should be made in the by overcurrents and faults in the system.
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One commenter requested calculations and not by actual in-mine advantageous for the failure to be clarification regarding whether vacuum short-circuit tests. cleared by the circuit-interrupting contactors can be used to provide To date, it has not been necessary to device in the controller, not the section ground-fault and overload protection conduct in-mine testing for the purpose power center which acts as a back-up. since some have been approved for use of making determinations of proper This commenter further stated: on longwall controllers. Vacuum settings of short-circuit protective (1) Without the presently permitted contactors are a vacuum sealed system devices. However, the method used to time delays, the fault would also as opposed to a circuit breaker, which make these determinations should not deenergize the transformer, and more interrupts the arc in air or oil. The final be restricted to calculations, since than likely, personnel would reenergize rule permits the use of vacuum unusual or unanticipated conditions, the circuitry to find the location of the contactors as long as these contactors such as high motor starting currents, fault in the system; meet the definition of a ‘‘circuit- may require in-mine testing. (2) This unnecessary closing in on a interrupting device.’’ Paragraph (a)(2) of the final rule faulted circuit is eliminated when the Some commenters submitted sketches specifies short-circuit time delay circuits are properly coordinated; and of high-voltage longwall circuits, and settings for protective devices. Short- (3) Time delays should be kept as requested an evaluation of whether the circuit devices protecting cables short as possible to provide adequate circuits would comply with the extending from section power centers to coordination. standard. It is beyond the scope of this motor-starter enclosures may Other commenters suggested that time rulemaking for MSHA to evaluate and incorporate time delays limited to the delays be eliminated and higher short- approve such submissions. Systems and settings specified in the approval circuit settings be allowed based on wiring designs can vary from mine to documentation or 0.25-second, system capacity, provided that the mine and from section to section within whichever is less. This paragraph Agency develops test scenarios to the same mine, depending on factors revises the proposed rule to allow short- determine the safe time delay settings. such as control circuit configuration, circuit devices protecting motor or These commenters stated that load terminations, and available fault shearer circuits to incorporate elimination of time delays would offer current. MSHA will evaluate these intentional time delays. The time delays protection in the event of a direct fault designs on a case-by-case basis as mine may be limited to the settings specified because there would not be resistor operators plan to implement high- in the approval documentation, or up to strips (overloads) available to open the voltage longwalls at their mines and three cycles (0.050-seconds), whichever circuit and remove the power. They during the approval process under the is less. The purpose of permitting a time stated that inspections have revealed applicable 30 CFR part 18 provisions. delay is to prevent nuisance tripping that, in some cases, resistor strips are Paragraph (a)(1) of the final rule, like during motor starting. When high- either not operable, damaged, or have the proposed rule, specifies a current voltage longwall equipment was been by-passed. setting for short-circuit protective introduced to the mining industry, After careful review of this issue, the devices. The devices, whether located in nuisance tripping problems were Agency has concluded that the use of the section power center or the longwall experienced. This nuisance tripping was time delays and subsequent lower short- motor-starter enclosure, are required to caused by motor starting currents. In circuit settings would result in be set at the lower value of either the order to solve these problems, it may be coordination (selective tripping) of setting specified in the approval necessary to incorporate time delays circuit-interrupting devices. Proper documentation pertaining to the into the short-circuit protective devices. coordination of circuit-interrupting longwall system, or 75 percent of the Currently, electronic relays that have a devices can result in improved safety minimum available phase-to-phase time delay to override motor starting since faulted circuits can be more easily short-circuit current. The short-circuit currents are commonly used to provide and safely identified and isolated for the current settings specified during short-circuit protection for high-voltage purpose of troubleshooting, testing, and MSHA’s approval process are based on longwall circuits. repair work. Commenters also suggested the calculation of fault currents at The proposed rule allowed time that time delay settings of short-circuit various key locations in the system. delays for short-circuit devices protective devices used to protect any The results of a 1992 Agency study of protecting cables extending from power cable extending from the section power fault current levels in 30 high-voltage centers to motor-starter enclosures. The center to a motor-starter enclosure not longwall systems indicate that phase-to- maximum value of the time delay was exceed the settings specified in approval phase short-circuit currents range limited to the smaller of the value documentation or 0.30-second (18- between 1,500 and 9,000 amperes at the specified in the approval documentation cycles), whichever is less. various motor locations. (A copy of this or 0.25-second (15 cycles). However, the This provision is not changed from study is available as part of the record.) proposed rule did not provide for time the proposed rule. MSHA’s experience Therefore, current (ampere) settings of delays to be incorporated into short- has been that the maximum time delay 75 percent of the minimum phase-to- circuit devices protecting motor or for reliable coordination is 0.25-second phase short-circuit currents will shearer cables. The Agency specifically (15-cycles). Further, a joint standard establish maximum limits for trip solicited comments regarding published by the American National settings of short-circuit current devices. elimination of intentional time delays Standards Institute (ANSI) and the As equipment is used and moved from and allowing higher short-circuit Institute of Electrical and Electronics one location to another in a mine, settings based on system capacity. Engineers, Inc., entitled IEEE changes take place in both the One commenter stated that time Recommended Practice for Protection equipment and electrical system that delays between the longwall controller and Coordination of Industrial and indicate a need for a change in settings and section power center should be Commercial Power Systems (IEEE Buff for short-circuit protective devices. required to permit adequate Book)—Standard 242–1986, allows Some commenters suggested that a coordination with downstream devices. 0.25-second time-delay to ensure statement be added to this provision According to the commenter, if there is reliable coordination of short-circuit indicating that the minimum available a failure in the utilization circuit, for protective devices. Therefore, an short-circuit current be determined by example, the crusher motor, it is increase to 0.30-second is not justified.
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These commenters further suggested grounded systems that limit the ground- voltage neutral grounding resistor, that short-circuit protective device fault current in a circuit to 0.50 to 1.00 which opens the ground-check circuit settings, used to protect motor and ampere. MSHA encourages this practice for the high-voltage circuit supplying shearer circuits, should be based on the to continue. The levels specified in the the section power center, if the maximum asymmetrical starting current final rule allow new technology to grounding resistor is subjected to a with no intentional time delay or be detect lower ground-fault currents and sustained ground-fault current. The based on the maximum symmetrical reduces shock hazards. During ground- overtemperature rating or setting must starting current with a time delay of no fault conditions, the grounding resistor be 50 percent of the maximum more than 0.050-second (three-cycles). will dissipate heat. The final rule limits temperature rise of the grounding These commenters pointed out that the heat dissipation by the grounding resistor or 150°C (302° F), whichever is modern electronic short-circuit resistors to a value equivalent to the less. The final rule is changed from the protective devices can be made to heat dissipated by grounding resistors proposed rule to also allow the use of operate within one cycle (0.017-second). that have been in service for numerous a current transformer, and a thermal These devices will respond while the years on medium-voltage longwall overcurrent relay to provide the motor or shearing machine starting systems. The specified values prevent required thermal protection. The final current contains an appreciable grounding resistor enclosures from rule uses the term ‘‘thermal protection’’ asymmetrical component and the overheating and becoming ignition or rather than ‘‘overtemperature asymmetrical component of the motor fire sources. There were no comments protection’’ to permit current or shearing machine starting current on this provision and therefore it transformers and thermal relays or other will be negligible near 0.050-second. remains as stated in the proposed rule. devices such as thermostats that react to They suggested that introducing a 0.050- Paragraph (a)(4)(i) of the final rule, overtemperature. This change allows second time delay will permit a like the proposed rule, requires high- new technology developed by the significant reduction in the setting of voltage circuits extending from the mining industry during the last seven the short-circuit protective devices. section power center to have ground- years. Another commenter suggested that it is fault protection set at not more than 40 A commenter questioned the need for important to recognize the difference percent of the current rating of the these devices. In response, grounding between asymmetrical motor starting neutral grounding resistor. These resistors generate heat when subjected currents that persist for two (0.033- protective devices assure that circuits to sustained ground-faults. An second) to three cycles (0.050-second) extending from the section power overtemperature device causes following contactor closure, and motor source will be quickly deenergized interruption of the high-voltage circuit starting currents that persist for several when they are subjected to ground supplying the section power center by seconds. This commenter pointed out a faults. The final rule uses the current opening the ground-wire monitor circuit need for two cycles time delay. MSHA ratings for grounding resistors, specified before extreme heat destroys the agrees that there is a difference between in paragraph (a)(3), as a basis for setting grounding resistor function. Failure of ground-fault devices. For example, if a asymmetrical motor starting currents the resistor leaves the circuit 6.50 ampere grounding resistor is used, and symmetrical motor starting currents unprotected against ground-faults and the ground-fault device must operate to which can last for several seconds. increases the possibility of fire and Therefore, the final rule permits deenergize the circuit at 2.60 amperes shock hazards. The commenter also limited time delays to be used in (40 percent) or less. If a 0.50-ampere requested a six-month delay in conjunction with lower settings of short- grounding resistor is used, the ground- implementing this provision to allow circuit protective devices rather than fault device must operate to deenergize mine operators to acquire high quality higher settings of short-circuit the circuit at 200 milliamperes or less. devices. It is MSHA’s view that since protective devices without time delays. The 40 percent trip level provides a these devices have been required to be This should result in proper safety factor to assure that unexpected coordination and subsequent selective lower levels of ground-fault current installed on high-voltage longwall tripping of circuit-interrupting devices would be detected and cause the circuit- mining systems for at least the past and prevent nuisance tripping of circuit- interrupting device to open. This value seven years under petitions granted for interrupting devices due to high motor also allows proper trip coordination § 75.1002, the devices should be readily starting currents. In response to with other protective devices. There available for use. A six month delay is comments, the Agency concludes that a were no comments on this section of the not necessary. time delay will be necessary to allow rule and the final rule adopts the Another commenter wanted the proper starting of motors. Therefore, this language used in the proposed rule. maximum temperature for the ° provision allows short-circuit devices Paragraph (a)(4)(ii) of the final rule, overtemperature device to be set at 150 protecting motor or shearer circuits to like the proposed rule, requires backup C. This setting was incorporated into the incorporate intentional time delays ground-fault protection to detect an 1992 proposed rule. Some commenters limited to the settings specified in the open grounding resistor. The ground- suggested that overtemperature approval documentation, or up to three fault protective device can be a protection should remove power from cycles (0.050-seconds), whichever is combination of a potential transformer the power center transformer if the less. and voltage relay, or another device(s) grounding resistor is subjected to a Paragraph (a)(3) of the final rule, like capable of detecting an open neutral sustained ground fault. These the proposed rule, requires ground-fault resistor. Once an open neutral resistor is commenters pointed out the following: currents to be limited by a neutral detected, the ground-fault protective (1) Many power centers are equipped grounding resistor to not more than 6.5 device must cause the circuits extending with an incoming high-voltage circuit amperes when the nominal voltage of from the power center to be breaker to provide protection for the the power circuit is 2,400 volts or less, deenergized. There were no comments transformer; or 3.75 amperes when the power circuit on this section of the rule and it remains (2) The overtemperature protection for voltage is greater than 2,400 volts. as stated in the proposed rule. the grounding resistor could cause this Typically, the mining industry has used Paragraph (a)(4)(iii) of the final rule circuit breaker to open in the event of grounding resistors in resistance- requires thermal protection for the high- a sustained fault; and
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(3) This would remove the ground they stated that a 0.200-ampere setting motors or shearers. These ground faults fault and make troubleshooting more would still be less than 40 percent of the must be removed as quickly as possible. convenient. maximum ground-fault current. Ground- Another commenter wanted to add MSHA agrees that the use of an fault devices are used to detect low wording to define the total time for incoming high-voltage circuit breaker levels of fault currents during a ground-fault protection as 0.4 second may be an acceptable device for grounded phase condition. These (24 cycles) maximum for all devices. removing power from the section power sensitive devices can be influenced by Most longwall systems now utilize two center when the overtemperature device extremely large values of motor starting ground-fault protective devices with a is activated. However, activation of the current. time delay of 0.25 second (15 cycles) grounding resistor overtemperature MSHA has evaluated these comments which provides adequate time for protection could be an indication of and determined that there are sensitive selective tripping. Thus, the final rule is serious problems in the tripping circuits ground-fault protective devices unchanged from the proposed rule. for the circuit-interrupting device(s) commercially available that have been Paragraph (a)(7) of the final rule, like located in the power center. This successfully used to respond to the the proposed rule, requires an condition warrants complete removal of conditions described by the undervoltage protection device that power from the entire power center commenters. These devices can safely operates on loss of voltage to cause and until the condition is properly and reliably operate at 0.125-amperes or maintain the interruption of power to a investigated and corrected. less even on systems having higher circuit. The rule reduces the likelihood motor-starting currents. A large number that miners will be pinned or crushed Another commenter stated that of existing high-voltage longwall due to the automatic restarting of the experience has shown that the required systems use grounding resistors that equipment. A commenter suggested protection may be best provided by limit ground-fault currents to 0.500- another means of compliance by using using a current transformer and thermal amperes. Raising the trip value of a ‘‘momentary start contactor with a seal overcurrent relay rather than a ground-fault devices protecting motor in circuit.’’ In response, the rule, thermostat. The commenter also stated and shearer cables to 0.200-amperes unchanged from the proposed rule, is that this type of protection would not be would also have the device set at 40 performance oriented and permits any dependent upon control power and percent of the current rating of the undervoltage protection provided by a would still be able to deenergize the grounding resistor. This setting would device that operates on loss of voltage. primary of the transformer. MSHA be the same value as protective devices Therefore, any voltage sensing device, agrees with this comment. The final rule used on cables extending from power including the method specified by the is changed to allow more flexibility in centers to motor-starter enclosures. commenter, that would prevent the the use of thermal protection. It permits Proper coordination of these protective automatic reclosing of the circuit the use of a current transformer and a devices with upstream devices may not protective device as specified in thermal overcurrent relay to provide be achievable if the trip setting is raised paragraph (a) will meet the required overtemperature protection. to 0.200-ampere. For this reason, the requirements of the final rule. Paragraph (a)(5) of the final rule, like provision is unchanged from the Paragraph (b) of the final rule, like the the proposed rule, requires high-voltage proposed rule. proposed rule, requires a single motor and shearer circuits to be Paragraph (a)(6) of the final rule, like window-type current transformer to provided with instantaneous ground- the proposed rule, allows time delay encircle the three-phase conductors for fault protection set at not more than settings, not to exceed 0.25 second (15 ground-fault protection. The equipment 0.125-ampere. This provides highly cycles), of ground-fault protective safety grounding conductors are sensitive and responsive ground-fault devices to provide coordination with prohibited from being passed through or detection systems, using existing the instantaneous ground-fault connected in series with ground-fault technology, for high-voltage circuits protection of motor and shearer circuits. current transformers. This configuration supplying electric face equipment. This provision limits the time lapses could defeat ground-fault protection and Protective devices are required to between actuation of the section power result in hazardous voltage on operate instantaneously, greatly center ground-fault protective devices equipment frames. A single window- reducing the likelihood of fires and and those located in the motor-starter type current transformer must be used shock hazards caused by ground faults. enclosure. Time delay settings allow to provide the ground-fault protection Some commenters suggested that the coordination and selective tripping of required by paragraph (a)(4)(i) for instantaneous ground-fault protection circuit protective devices. This circuits extending from the section be set at not more than 0.125-ampere if coordination and selective tripping also power center to the motor-starter the full-load current of the circuit does assures that the entire circuit enclosures. It also requires the same not exceed 200 amperes and set at not deenergizes quickly to reduce exposure type current transformer for ground- more than 0.200-ampere if the full-load to shock hazards. fault protection specified in paragraph current of the circuit exceeds 200 A commenter wanted a time delay of (a)(5) for: amperes. These commenters pointed out 0.1 second (6 cycles) for ground-fault (1) High-voltage motor circuits that it is very difficult to produce protection for high-voltage motors. The extending from the motor-starter ground-fault current transformers that commenter described situations where enclosures; can reliably discriminate between small nuisance tripping occurred during (2) The shearer motor circuits ground-fault currents and larger motor starting and stopping of the motor and extending from the section power starting currents. They further stated a time delay of 0.1 second would solve center; and that, when the full load current of a the problem. MSHA has evaluated this (3) Motor enclosures. circuit exceeds 200 amperes, it is comment and has determined that Some commenters suggested this reasonable to expect motor starting technology is available and currently provision should allow for alternative currents to exceed 2,000 amperes and used by industry to alleviate this components if they provide equivalent that a small increase in the setting of the condition without changing the time or improved protection. MSHA, ground-fault protection is justified for delay. Most ground faults occur between however, is unaware of any alternative certain high-current circuits. Finally, the motor-starter enclosure and the device that provides equivalent
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protection and the commenter did not Paragraph (d) of § 75.814, like the provide a safe means of disconnecting specify any equivalent devices. The use proposed rule, prohibits the use of power during the performance of of a single window-type current circuit-interrupting devices that electrical work. It includes design and transformer to encircle only the three automatically reclose. Automatic performance requirements pertaining to phase conductors assures that sensitive reclosure of the circuit-interrupting electrical ratings, lockout, grounding, ground-fault devices will be able to device allows immediate reenergization and maintenance requirements detect all ground faults exceeding the of a circuit that has sustained a fault. pertaining to compliance with part 18 of setting of the device. Detection devices Faults occur in underground electrical Title 30 CFR. This section was derived, inserted in the ground wire may not systems as a result of damage from roof in part, from existing §§ 75.511, 75.520, detect all ground-fault currents and falls or equipment insulation failure. 75.601, 75.705, and 75.808. could compromise the integrity of the Under such circumstances, the use of Paragraph (a) as in the proposed rule, ground circuit. Therefore, paragraph (b) automatic reclosing circuit-interrupting requires a disconnecting device in of this section remains as proposed. devices could create shock and fire addition to the circuit-interrupting Paragraph (c) of the final rule requires hazards when a short-circuit or ground- device (required by § 75.814) in the a ground-fault test circuit for each fault condition exists in the circuit. power center that supplies power to ground-fault current device. This test There were no comments on this longwall equipment. This disconnecting circuit must inject a current of 50 paragraph and it remains as proposed. device provides visual evidence that the percent or less of the current rating of The final rule includes an additional circuit is deenergized. Either a paragraph (e) that is partially derived disconnecting switch or cable coupler the grounding resistor to verify that a from § 75.518–1—Electric equipment would suffice to satisfy this ground-fault condition causes the and circuits; overload and short circuit requirement. Disconnecting devices in corresponding circuit-interrupting protection; minimum requirements. power centers facilitate the device to open. This testing procedure This was suggested by joint commenters deenergization process prior to helps determine if ground-fault current from industry and labor to address performance of electrical work. Figures devices function at required current concerns regarding the use of cables in I–1 and I–2 in Appendix A provide levels. It will also test the sensitivity of parallel. The commenters suggested that guidance for compliance with this each device to ground-fault currents. when two or more cables are used to requirement. The Agency did not The proposed rule required each supply power to a common connection receive any comments on this provision ground-fault current device to be point (bus), each cable be provided with and it is unchanged from the proposed provided with a test circuit that would ground-wire monitoring so that all rule. inject a current of 50 percent or less of cables are deenergized when the Paragraph (b) of the final rule, like the the current rating of the grounding grounding conductor becomes severed proposed rule, establishes maintenance resistor and cause each corresponding or open. In support of this suggestion, requirements for disconnecting devices circuit-interrupting device to open. the commenters noted that when two or in motor-starter enclosures. Section Some commenters suggested that this more cables are connected in parallel, 75.815(b) requires that disconnect requirement be limited to ground-fault shock hazards will exist if one cable has devices be maintained in accordance circuit devices required by paragraphs been disconnected and the other cable with the approval requirements of (a)(4)(i) and (a)(5) of this section. These is left energized. MSHA agrees. The paragraph (f) of § 18.53—High-voltage commenters also suggested that the Agency has been incorporating this longwall mining systems. Section ground-fault test circuit inject a primary additional requirement into petitions for 18.53(f) requires that the load-side current into the current transformer that modification of § 75.1002 during the last power conductors be grounded when does not subject the equipment to an four years. The final rule requirement the disconnecting device is open. This actual phase-to-ground fault. They that parallel power cables be installed provision guards against the occurrence pointed out that primary current with ground-wire monitor systems of electrical accidents by requiring the injection tests of the ground-fault addresses this concern. Ground-wire circuit disconnect device to ground the devices are safe and effective tests for monitoring in power cables has been an disconnected circuit before work is those devices. They further stated that inherent part of the developing high- performed on the circuit. The final rule testing of the backup ground-fault voltage longwall technology over the assures that a properly maintained safe devices located across the grounding last 16 years. In addition, under the means of deenergizing longwall circuits resistor, such as the potential final rule, parallel circuits installed after and equipment is readily available for transformer and overtemperature relay, the effective date of this rule must be use during routine operation or in the would require application of an actual protected by a single circuit-interrupting event of an emergency. Additionally, phase-to-ground fault and could be device rather than have circuit- the final rule provides for safe hazardous to both personnel and interrupting devices operating in deenergization of high-voltage circuits equipment. MSHA agrees with the parallel unless such devices are in the motor-starter enclosure, or commenters that this method of testing mechanically and electrically equipment supplied power through the is considered to be safe and effective in interlocked. This is supported by the enclosure during testing and determining whether a device trips at its fact that 30 CFR § 75.518–1 requires troubleshooting work. MSHA setting. In response to these comments, overcurrent devices to conform to the encourages mine operators to continue the final rule modifies the proposed provisions of the National Electric Code using additional disconnecting devices rule, to require each ground-fault which prohibits parallel connections of that are already installed in many current device required by paragraphs circuit-interrupting devices. existing longwall systems. (a)(4)(i) and (a)(5) to have a test circuit Paragraph (b) requires a caution label that passes a primary current of 50 Section 75.815 Disconnect Devices on the cover of each starter enclosure percent or less of the maximum ground- Section 75.815 of the final rule compartment containing the main fault current through the current includes requirements pertaining to disconnecting device. This caution label transformer and cause the disconnecting devices located in must warn miners against entering the corresponding circuit-interrupting longwall power centers and in longwall compartment before deenergizing the device to open. equipment motor controllers that incoming high-voltage circuits to the
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compartment. It warns miners that the without creating hazardous conditions. in § 75.807, cables installed six and one line side of the disconnect device may If the device is not designed for full load half feet or more above the mine floor be energized when the device is opened interruption, the device must be satisfy these requirements by location. and cautions them to deenergize installed so that a circuit-interrupting Guarding minimizes the possibility of incoming power before removing any device will deenergize the incoming miners inadvertently contacting the covers. It also helps to assure that power circuit before the disconnecting cables. Also, cable guarding must miners deenergize power to starter device opens. Use of improperly rated consist of grounded metal or enclosures before removing any of the devices could result in the destruction nonconductive flame-resistant material. covers. There were no comments of the device and injuries to miners due High-voltage cables used to supply received on this provision so the final to flash burns or flying parts. The final longwall equipment could present rule is unchanged from the proposed rule further requires that disconnecting shock and fire hazards if the cables are rule. MSHA recognizes that the mining devices installed in explosion-proof damaged or defective. industry has taken safeguards by using enclosures be maintained in accordance Paragraph (a)(1) of the final rule, like additional caution labels to warn miners with the approval requirements of the proposed rule, requires that cables of stored energy devices (capacitors). § 18.53(f)(2)(iv) of part 18. This be guarded where persons regularly We encourage the industry to continue provision specifies that disconnecting work or travel over or under the cables. the safety practice of using caution devices be designed and installed to This minimizes accidental contact with statements that warn miners to ground cause the current to be interrupted cables. There were no comments the capacitors before performing work automatically prior to the opening of the received on this provision and it is on electric circuits. contacts of the device. The Agency did unchanged from the proposed rule. Paragraph (c) of the final rule, like the not receive any comments on this Paragraph (a)(2) of the final rule, like proposed rule, requires disconnecting provision so it remains the same as the the proposed rule, requires guarding devices to have voltage and current proposed rule. where the cables leave cable handling or ratings compatible with the circuits in Some commenters suggested that a support systems to extend to electric which they are used. This requirement new paragraph (f) be added to require components. This provision prevents ensures safe operation of these devices that any additional disconnecting physical damage from stress and flexing during normal use. The Agency received devices used to deenergize a portion of that might cause shock and fire hazards. no comments on this provision. It the longwall equipment meet the The Agency did not receive any remains the same as the proposed rule. requirements of paragraphs (c), (d), and comments on this provision and it Paragraph (d)(1) of the final rule, like (e). They stated that it is often necessary remains the same as in the proposed the proposed rule, requires that to maintain power on part of the rule. disconnecting devices be designed to longwall equipment in order to safely Paragraph (b) of the final rule requires provide visual evidence that all and efficiently perform electrical work guarding of high-voltage cables to ungrounded power conductors are on another part of the equipment. For minimize the possibility of inadvertent disconnected when the device is open. example, they stated that a contact with cables and to protect high- Visual evidence means the ability to disconnecting device for the shearing voltage cables from physical damage. observe the physical separation of the machine circuit will permit electrical Guarding must be constructed of control and power conductors without work on a deenergized shearing grounded metal or nonconductive removing any covers. There were no machine while maintaining power on flame-resistant material. This standard comments received on this provision the rest of the longwall. Under the final provides minimum requirements for the and no changes were made to the rule, individual disconnecting devices, physical and electrical protective proposed rule. such as cable couplers, may be used to characteristics of the guarding. The Paragraph (d)(2) of the final rule, like isolate individual pieces of equipment proposed rule required that guarding the proposed rule, requires that for the purpose of performing prevent miners from contacting high- disconnecting devices be equipped to maintenance. The final rule requires voltage cables. ground all power conductors when the that all additional disconnecting devices One commenter suggested that the device is ‘‘open’’. This requirement satisfy the requirements of paragraphs c, provision specifically permit the use of allows the circuit to be properly d, and e. Therefore, the Agency believes either continuous guarding or grounded before any work is performed that an additional provision is not overlapping sections of guarding. on the electric circuits or equipment. It necessary. According to this commenter, also allows discharging of any existing overlapping sections of guarding voltage due to capacitance between the Section 75.816 Guarding of Cables achieve the safety goal of the provision power conductors and ground. The This rule is derived in part from and would reduce time-consuming and Agency did not receive any comments existing § 75.807—Installation of high- expensive repairs that could involve on this provision. It remains unchanged voltage transmission cables and thousands of feet of cable to repair a from the proposed rule. addresses guarding of high-voltage small section. In response to this Paragraph (d)(3) is unchanged from cables supplying longwall equipment. comment, the rule specifies the the proposed rule. It requires each Until this rule, § 75.807 related to high- locations where cables are required to device be equipped to lock the device in voltage cables in areas not in by the last be guarded. Under the rule, the guarding the open position. This ensures that the open crosscut or not within 150 feet material must cover the cables and circuit being worked on remains from the pillar workings. In addition to continuous or overlapping guarding deenergized until work is completed. the § 75.807 requirements, § 75.816 of may be used. When joining sections of There were no comments received in this final rule requires guarding of high- metal guarding, steps should be taken to response to this provision. voltage cables where persons regularly assure proper grounding. Paragraph (e) of the final rule, like the work or travel over or under the cables Other commenters suggested that this proposed rule, requires that and where the cables leave cable section require that guarding disconnecting devices, except those handling or support systems in the ‘‘minimize’’ rather than ‘‘prevent’’ the installed in explosion-proof enclosures, longwall face areas or are within 150 possibility of miners contacting the be capable of interrupting load currents feet of the pillar workings. As provided cables. They stated that it is not
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practical to design guarding that would Isolation and placement help guard Shielded-type cables, required by prevent miners from contacting the against fire and assures protection of existing regulations, provide the cables. This often occurs when miners electric cables, which could be necessary protection for miners by are attempting to guide or train cable damaged, if hydraulic lines are ruptured limiting or preventing electrical arcing into its holding trough when it is loose or conductor insulation fails. Based on and flashover within the cable. This or falls out. They suggested it is possible MSHA experience, acceptable methods protection occurs as long as the cables to design guarding that would which meet § 18.36(b) requirements will are used in conjunction with proper ‘‘minimize’’ contact or ‘‘block access’’ to be determined during the part 18 mechanical protections required under the cable. MSHA agrees with this approval process. Guarding of cables by § 75.817, and with proper maintenance commenter and modified the proposed proper isolation and placement is an of electrical protective devices required rule. In response to these comments, acceptable method to meet this under § 75.814. Therefore, paragraph (a) this revised provision, requires a requirement. of this final section remains as physical barrier consisting of guarding Other commenters suggested that the proposed. material between the cables and miners wording of the rule be changed to Paragraph (b) of the final rule requires to minimize inadvertent contact with ‘‘longwall mining equipment shall be high-voltage insulated gloves, sleeves, the cables, and requires mechanical provided with cable handling and and other insulated personal protective protection for the cables. Also, § 75.818 support systems that are constructed, equipment, to have a Class 1 (7,500 of the final rule prohibits intentional installed, and maintained to minimize maximum use volts) or higher rating contact with cables except for the the possibility of miners contacting the that has been established by a nationally purpose of training (guiding) motor and cables and to protect the high-voltage recognized consensus standard. The shearer cables with the use of proper cables from damage.’’ We agree with the protective equipment must be: (1) protective equipment. commenters as stated in the previous Examined prior to each use for signs of discussion of § 75.816. The final rule damage or defects; (2) destroyed or Section 75.817 Cable Support Systems requires that cable support systems removed from the underground area of This section of the rule addresses minimize the possibility of inadvertent the mine if found damaged or defective; handling and support systems of high- contact instead of preventing contact. and (3) electrically tested every six voltage cables suppling longwall months according to a nationally Section 75.818 Use of Insulated Cable equipment. Under the final rule, recognized consensus standard. This Handling Equipment longwall mining systems must be provision protects against electrical equipped with cable handling and This section of the final rule shock hazards by requiring personal support systems that are constructed, addresses the types of personal protective equipment to be rated for a installed, and maintained to protect protective equipment that may be used maximum use voltage and examined high-voltage cables from damage and to when it is necessary to handle high- before each use to determine if the minimize the possibility of miners voltage longwall cables, the examination equipment is safe to use. Paragraph (b) inadvertently contacting the cables. for defects or damage prior to use, and of the proposed rule required all Under the proposed rule, these systems the intervals at which high-voltage personal protective equipment to be were required to prevent miners from protective equipment must be tested. Its rated for 20,000 volts; examined before contacting high-voltage cables. High- purpose is to provide protection against each use for visible signs of damage; voltage cables used to supply longwall electric shock hazards associated with removed from the underground area of equipment can present shock and fire the handling of energized high-voltage the mine when damaged or defective; hazards if the cables become damaged longwall cables. This section is derived, and electrically tested every six months. or defective. This section of the final in part, from existing requirements in A commenter suggested that this rule provides the necessary protection §§ 75.705–6—Protective clothing; use paragraph be modified to allow gloves to cables and miners by minimizing and inspection, 75.705–8—Protective to be rated for a minimum of 5,000 volts exposure to damaged or defective equipment; testing and storage and and tested every six months as cables. This section is derived, in part, 75.812—Movement of high-voltage described in a nationally recognized from existing requirements in § 75.807 power centers and portable consensus standard. The Agency is not and addresses new systems developed transformers; permit. aware of any recognized consensus by the mining industry to mechanically Paragraph (a) of the final rule, like the standards that rate gloves, sleeves, and handle and support cables. These proposed rule, requires that personal other personal protective equipment at systems are presently used on high- protective equipment be used when 5,000 volts. The commenter also stated voltage longwall mining systems to training or guiding, by hand, a high- that damaged or defective gloves should minimize damage to the cables. voltage longwall cable into the cable be permitted to be either removed from One commenter suggested that a handling trough when the cable the underground area of the mine or provision be added to this section that inadvertently comes out. Commenters destroyed. allows the installation of guarded high- suggested that the list of protective Another commenter stated that voltage cables in cable handling and equipment be expanded to include insulated personal protective equipment support systems where hydraulic hoses facial protection and protective should be electrically tested by the and low- and medium-voltage cables are clothing, and that the protective manufacturer in accordance with ASTM also installed. In response to this equipment also be capable of providing standards and be rated for at least the comment, high-voltage longwall protection from a cable explosion. They maximum nominal voltage of the equipment and associated cables are stated that additional protection is circuit. The commenter also stated that currently required by existing needed for persons who handle high- personal protective equipment should § 18.36(b)—Cables between machine voltage longwall cables, since persons be examined before each use for visible components to be isolated from have been burned when power signs of damage or defects and be hydraulic lines. Also, existing § 75.807 conductor insulation deteriorates within electrically tested at least every six currently requires that the high-voltage the cable and the power conductors months or when there is any sign of cables be placed in a manner to prevent fault or contact each other, causing the excessive wear. This commenter stated contact with other low-voltage circuits. cable to explode. MSHA disagrees. that the visible and electrical tests
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should be conducted in accordance with The compartment separations and 75.820(f) which MSHA revised due to American Society for Testing and interlock switches must be maintained comments. The revisions address: (1) Materials (ASTM) standards. in accordance with paragraphs (a) and The fact that persons qualified under In response to the commenters’ (b) of § 18.53—High-voltage longwall § 75.153—Electrical work; qualified concerns, we agree that safety would be mining systems. The purpose of § 75.819 person must be able to perform enhanced by adopting the ASTM is to help guard against miners coming electrical work on all circuits and standard. We have revised paragraph (b) in contact with energized internal equipment; (2) The type of gloves that of the proposed rule. The final rule components of high-voltage electric must be worn by persons performing requires insulated protective equipment, equipment through proper maintenance troubleshooting and testing; and (3) The including high-voltage gloves and of safety devices that assure methods used to guard against contact sleeves, to be rated a Class 1 or higher deenergization when any cover that with a high-voltage cable during (maximum use voltage of 7,500 volts). provides access to energized high- installation and/or removal of belt Paragraph (b)(1) requires that this voltage components is removed. structure. equipment be examined before each use Compartment separation also helps Paragraph (a) of the final rule requires for visible signs of damage or defects. assure that persons are not exposed to that electrical work on all circuits and This section requires users of protective adjacent energized high-voltage equipment associated with high-voltage equipment to examine it for hazardous components or circuits after gaining longwalls be performed only by persons conditions, including excessive wear. access to compartments containing qualified, in accordance with § 75.153, For example, a method commonly used control, communication, or other low- to perform electrical work on all circuits to detect damage in insulating gloves is and medium-voltage circuits. and equipment, not just high-voltage to test the rubber gloves by rolling the This provision provides automatic circuits and equipment. This change is cuff tightly toward the palm of the glove protection for miners who may consistent with the recent Federal Mine in such a manner that air is entrapped inadvertently remove a cover exposing Safety and Health Review Commission inside the glove. Puncture detection energized high-voltage circuits should decision, Secretary of Labor v. Black may be enhanced by listening for the wrong circuit be disconnected. Mesa Pipeline, Inc. 22 FMSHRC 708, escaping air or by feeling escaping air There were no comments received on 715 (June 30, 2000). That decision against the face. this section of the proposed rule and it concluded that § 75.153 requires that a In response to commenters, the remains as proposed. ‘‘person qualified’’ be knowledgeable of Agency has revised paragraph (b) in the high-, medium-, and low-voltage Section 75.820 Electrical Work; final rule to allow defective personal circuits and equipment. Therefore, for Troubleshooting and Testing protective equipment to be destroyed or clarification purposes, the language of removed from the mine. The Agency Section 75.820 is directed at this final rule has been modified to agrees with the commenter that protecting miners while they are conform with this decision and the destroying this equipment when it performing electrical work, including plain meaning of § 75.153. This requires becomes defective is as effective as troubleshooting and testing, and the that a person qualified to work on removing it from the underground mine. removal of belt structure. This section is electrical circuits be knowledgeable of MSHA also received comments derived, in part, from existing low-, medium- and high-voltage suggesting that insulating protective §§ 75.509—Electric power circuit and circuits. The Agency currently requires equipment be tested every six months in electric equipment; deenergization, that qualification in all voltages be accordance with nationally recognized 75.511—Low-, medium-, or high-voltage obtained before a person can become standards. The Agency agrees with this distribution circuits and equipment; qualified under § 75.153. The commenter and has revised paragraph repair, and 75.705—Work on high- requirement that persons performing (b) to require that all insulated handling voltage lines; deenergizing and electrical work be qualified for all equipment for use with high-voltage grounding and addresses requirements voltages assures that persons performing longwall cables be electrically tested for performing work on all circuits and work on low- and medium-voltage every six months in accordance with a equipment associated with high-voltage circuits are qualified to identify hazards nationally recognized consensus longwalls. This section applies to all that may exist on high-voltage circuits standard contained in the ASTM F496– low-, medium-, and high-voltage in close proximity of their work. 97, ‘‘Standard Specification for In- circuits and equipment associated with Some commenters suggested that Service Care of Insulating Gloves and high-voltage longwalls. The paragraph (a) state that electrical work Sleeves.’’ The purpose of these formal requirements are similar to those in on all high-voltage circuits and any testing procedures for high-voltage cable existing §§ 75.509 and 75.511 for work enclosure containing high-voltage handling equipment is to provide on electric circuits and equipment components shall be performed only by necessary safety protections for miners generally, except with additional persons qualified under § 75.153 to and ensure that unknown equipment requirements applicable to high-voltage perform electrical work only on high- defects will be detected before they are longwall installations. These voltage circuits and equipment. These a hazard to miners. requirements include personnel commenters indicated that the proposed qualifications and safe work procedures, rule would not permit persons qualified Section 75.819 Motor-Starter including safety equipment when under § 75.153 to perform electrical Enclosures; Barriers and Interlocks troubleshooting and testing, and work only on low- and/or medium- Section 75.819 of the final rule, like methods to guard against contact with voltage circuits or equipment or perform the proposed rule, requires separation energized high-voltage cables during the any electrical work on circuits or by location, partitions, or barriers of installation and/or removal of belt equipment associated with a high- low- and medium-voltage circuits from structure(s). The final rule for § 75.820 voltage longwall. The commenters high-voltage circuits in motor-starter is identical to the proposed rule except further indicated that certain enclosures and requires cover interlock for changes to § 75.820(a), which is subsystems of the longwall are switches to be installed on the cover of revised based on a recent Federal Mine completely isolated from high-voltage any motor-starter compartment Safety and Health Review Commission circuits and equipment such as: lighting containing high-voltage components. decision and §§ 75.820(d)(3) and systems, communication systems, shield
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control systems, hydraulic pump equipment with a circuit-interrupting people and that a group lockout control systems, battery chargers, air device. There were no comments on procedure be allowed. This commenter compressors, and rock dusters. paragraph (b)(1) of the proposed rule. suggested that primary responsibility However, because many low- and This paragraph of the section remains as can be vested with an authorized medium-voltage circuits associated with proposed. employee when more than one group is high-voltage longwalls are in close Paragraph (b)(2) of the final rule working on the equipment, so that an proximity to the high-voltage circuits, requires that a qualified person open the authorized person from each group may MSHA believes it is important that disconnecting device when performing lockout the equipment. A review anyone performing electrical work on work on circuits and equipment, and if conducted by the Agency in 1999 the high-voltage longwall be high-voltage, ground the circuits. revealed that during the period 1970 to knowledgeable about low-, medium- Opening the disconnect device 1999, a total of 145 fatal accidents and high-voltage circuits. And, as noted deenergizes the circuit which, along occurred by miners contacting energized above, a person qualified under § 75.153 with grounding, protects the person circuits. Data further revealed that must be knowledgeable of all voltage working on the circuit from shock and during a five year period between 1994 circuits. electrocution hazards. A commenter and 1999, a total of nine fatal accidents Since all the circuits cannot be totally stated that in addition to grounding the were related to failure to lockout isolated, it is important that qualified circuit prior to work being performed, disconnecting devices. The review also persons working on the circuits of lower that grounding hot sticks (a collapsible revealed that deaths and injuries had voltages be aware of the hazards of high- non-conductive pole used to de-energize also occurred when equipment was voltage circuits. Another commenter electrical circuits) rated at 4,160 volts energized before all persons had inquired as to what the high-voltage should be available at each power center completed their work. Furthermore, the qualification requirements were and and a proximity tester should be used National Safety Council in Data Sheet suggested that MSHA ensure that by the qualified electrician to determine 237 Revision B, Methods of Locking Out appropriate training is defined and that the circuit is deenergized. In Electrical Switches (1971), recommends required. MSHA’s existing standard in response to this comment, § 75.815(b) of that individual, not group, type lockout § 75.511—Low-, medium-, or high- the final rule requires that the procedures be used. This publication is voltage distribution circuits and disconnecting devices be maintained in available in the rulemaking record. equipment; repair requires that only accordance with the approval Consistent with Agency experience and persons qualified in low-, medium- and requirements of paragraph (f) of § 18.53. safety recommendations, the final rule high-voltages perform high-voltage Section 18.53(f) in turn requires that the requires individual lockout rather than work, and § 75.153 sets forth the disconnecting devices ground the group lockout. MSHA is confident that procedures for their qualification. circuit when ‘‘open.’’ In addition, the this system provides the necessary Additionally, existing § 75.160— requirement in paragraph (b)(3) of safety protection because persons Training programs requires an MSHA § 75.820 places responsibility on each assigned to place and remove their own approved plan for retraining qualified qualified person to lock out the locks are more cognizant of and persons. Another commenter requested disconnecting device for the high- responsible for their own security, and that wording be added to allow anyone voltage circuit prior to performing work. more likely to take the steps necessary to perform high-voltage work under the Therefore, MSHA concludes that to assure proper deenergization. This supervision of a qualified person. Due to equipping power centers with also reduces the risk of error due to lack the hazards previously described, only grounding hot sticks, clamps, and of communication or inadvertent qualified electricians perform high- proximity testers, as suggested by the reenergization. For these reasons, the voltage work. Therefore, except for the commenter, is not necessary. Therefore, paragraph remains unchanged from the clarifications noted above, paragraph (a) paragraph (b)(2) of this section remains proposed rule. of this section remains as proposed. as proposed. Paragraph (b)(4) of the final rule, like Generally, paragraphs (b)(1) through Paragraph (b)(3) of the final rule, like the proposed rule, requires tags used on (b)(4) of § 75.820, like the proposed rule, the proposed rule, requires that deenergized circuits and equipment to require safety precautions to be taken by disconnecting devices be locked with an identify each person performing work qualified electricians prior to individual padlock by each person and the circuit or equipment on which performing electrical work. The performing work. Individual padlocks, work is being performed. There were no qualified electrician is responsible for removable only by the persons who comments on this paragraph of the assuring that the electrical circuit is installed them, place responsibility on proposed rule and it remains as properly deenergized, that the contacts the persons performing work to assure proposed. of the circuit disconnecting device are their personal safety. This should Paragraph (c) requires, like the open, and that the disconnecting device prevent accidental reenergization of proposed rule, that only the persons is locked out with a padlock and tagged. equipment or circuits before all persons who install a padlock and tag be These precautions assure that the have completed work. The danger and permitted to remove them. This affected circuit has been properly accident history of reenergization of provision also provides for an exception deenergized and disconnected so that circuits before work is completed where an operator could authorize persons performing work are not require such measures for the protection someone else to remove the lock and tag exposed to shock, electrocution, or burn of miners against electrocution or if the person who installed them is hazards. Without taking precautions, electric shock. A commenter suggested unavailable at the mine. Such such as properly locking out and tagging that the section be reworded to permit authorized person is required to be the affected circuit, qualified the oncoming worker to install his/her qualified to perform electrical work. electricians would be exposed to shock lock, and the departing worker to Additionally, the person who had and electrocution risks if someone were remove his/her lock at the change of originally installed the lock and tag to inadvertently reenergize the circuit. shifts. Another commenter suggested must be informed of the lock removal Paragraph (b)(1) of the final rule that MSHA recognize that service or before resuming work on the circuit or specifically requires that a qualified maintenance in many cases is equipment. A commenter stated that in person deenergize the circuit or performed by a new crew or group of the absence of the person who installed
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the lock, the mine operator may with equipment supplied from low- and troubleshooting of high-voltage circuits. designate a qualified electrician to medium-voltage as well as high voltage. The commenter added that wearing remove the lock after it has been These hybrid-type longwall systems rubber gloves should be required when determined that all other affected include both high-voltage and low- and working with high-voltage circuits; persons are not exposed to a hazard. medium-voltage equipment. This however, requiring that rubber gloves be Paragraph (c) of the final rule requires provision allows troubleshooting and worn when troubleshooting low- and locks to be removed by the person who testing of low- and medium-voltage medium-voltage circuits would installed them or by qualified persons circuits associated with these hybrid diminish safety. In response to these authorized by the operator, if that longwalls. Based on Agency experience comments, MSHA believes that rubber person is unavailable at the mine. with petitions for modification allowing gloves do not permit sufficient Paragraph (d) of the final rule requires such testing, troubleshooting, and dexterity, as do dry cloth gloves, for the that certain safety procedures be testing of low- and medium-voltage safe troubleshooting of low- and followed when troubleshooting and circuits can be safely performed with medium-voltage circuits. For example, testing energized circuits. This includes proper test instruments, and with use of an ohm meter has small controls which limiting troubleshooting and testing of protective gloves that are commercially are difficult to operate while wearing energized circuits only to low- and available. Therefore, paragraph (d)(1) of rubber gloves and the small metal medium-voltage systems. In addition, this section remains as proposed. probes used with the ohm meter are only qualified electricians wearing Paragraph (d)(2) of the final rule hard to pick up while wearing rubber properly insulated rubber gloves are permits troubleshooting and testing of gloves. A serious accident could result permitted to perform this work and only energized circuits only for the purpose if probes were improperly placed in an for the purpose of determining voltages of determining voltages and currents energized circuit or dropped in close and currents. This provision recognizes (amperes). Some commenters suggested proximity to voltages up to 995 volts. In that, in some instances, it is necessary that paragraph (d)(2) be changed to contrast, dry work gloves allow for for circuits or equipment to remain allow troubleshooting and testing to manual dexterity while providing energized for troubleshooting and determine waveform or other electrical adequate protection. The commenter testing. For example, in order to diagnostic testing as well as voltages specified that his company has safely understand the nature of problems and currents. The final rule, as written, used dry work gloves when within a circuit, it may be necessary to is responsive to the commenter’s troubleshooting low- and medium- take voltage or current readings while suggestion because evaluation of voltage circuits for 15 years. The the circuit is energized. waveform or diagnostic testing is commenter further stated that proposed Paragraph (d)(1) of the final rule, like normally considered to be a method of § 75.820(d) would conflict with existing the proposed rule, limits measuring voltage and current. § 75.509—Electric power circuit and troubleshooting and testing of energized Paragraph (d)(2) of this section remains electric equipment; deenergization in circuits only to low- and medium- as proposed. two respects. The first is that § 75.509 voltage systems. Since troubleshooting Paragraph (d)(3) of the final rule permits troubleshooting of high-voltage and testing energized circuits is known requires that troubleshooting and testing circuits, as well as low- and medium- to be inherently hazardous work, the of energized circuits be performed by voltage circuits. In contrast, proposed particular skills and training of a persons qualified under § 75.153 who § 75.820(d)(1) would permit qualified electrician are necessary for wear protective gloves when the voltage troubleshooting only on low- and performance of these tasks. of the circuit exceeds 40 volts. This medium-voltage circuits. The second is Troubleshooting and testing is limited should prevent accidents related to that proposed § 75.820 conflicts with to low- and medium-voltage energized contact with energized circuits while MSHA’s interpretation of § 75.509 circuits, primarily due to insulation troubleshooting and testing. These concerning situations where insulated ratings of available troubleshooting and gloves will provide the insulation rubber gloves are required. MSHA’s testing equipment. Insulation ratings on protection necessary if a miner has Program Policy Manual states: equipment commonly used to inadvertent contact with energized troubleshoot and test in underground circuits during troubleshooting and Work gloves in good condition are acceptable for troubleshooting or testing mines are insufficient to protect persons testing. A commenter stated that the energized low-or medium-voltage circuits or if such equipment is used to circuit is designed to permit equipment. High-voltage gloves, rated at least troubleshoot and test high-voltage troubleshooting of 120-volt alternating for the voltage of the circuit, are required for circuits. current (VAC) control power. During troubleshooting or testing of energized high- A commenter suggested that this period, high voltage is not present voltage circuits or in compartments troubleshooting of energized circuits while the normal/test auxiliary switch is containing exposed energized high-voltage ranging from 120 to 1,000 volts (low to in the ‘‘test’’ position and the incoming circuits. (This portion has been corrected by medium voltage) should be prohibited. high-voltage disconnect is in the ‘‘open/ MSHA Program Policy Update V–15.) This commenter indicated that the grounded’’ position. This commenter The commenter further stated that in industry has already demonstrated that suggested that gloves be rated for 120 order to be consistent with § 75.509, as high-voltage longwalls can be installed, VAC rather than the nominal voltage of well as prudent mining practices, commissioned, and maintained without the circuit. The Agency is not aware of proposed § 75.820(d) should be changed maintenance personnel being exposed any gloves rated for less than 1,000 to permit both troubleshooting of high- to any voltage higher than 120 volts. volts. The rating of gloves is determined voltage circuits and use of dry work The commenter further stated that if commercially through formal testing gloves for troubleshooting low- and multiple utilization voltages are procedures established by national medium-voltage circuits. required in the same compartment, then standards. In response the Agency states that each supply should have a disconnect Another commenter suggested that existing § 75.705—Work on high-voltage device, and cover switches should be this paragraph be changed to permit the lines; deenergizing and grounding arranged to trip circuit-interrupting use of dry work gloves when specifically applies to high-voltage devices to cut off both voltages. Some troubleshooting low- and medium- circuits out from (outby) the longwall high-voltage longwalls are designed voltage circuits and to permit mining faces or pillar workings. Section
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75.705 specifically prohibits work on Based on MSHA electrical accident needed to protect persons from an high-voltage lines underground in information and experience, 40 volts is electrical explosion, an electrical flash, relation to troubleshooting and testing the lowest voltage level range at which and from flying debris. Commenters of high-voltage circuits. Section 75.509 shock hazards are minimized. Other suggested that injuries could be generally applies to all electrical circuits mandatory safety standards, such as minimized if protective clothing, such and is less restrictive. This final rule §§ 77.515—Bare signal or control wires; as a leather vest instead of polyester, specifically applies to high-voltage voltage, 75.901—Protection of low- and was worn, as clothing made of material circuits on longwalls and is consistent medium-voltage three-phase circuits that melts could compound an injury. with the safety requirements of existing used underground, 75.902—Low- and In response, the Agency concludes § 75.705. medium-voltage ground check monitor that when mine operators and miners Based on Agency data and experience, circuits, and 77.902–1—Fail safe ground comply with the provisions of this final it is our view that attempts to check circuits; maximum voltage, use 40 high-voltage rule, including proper troubleshoot and test energized high- volts as a minimum safety voltage range testing, examination, and maintenance voltage circuits using standard test level. Section 18.50—Protection against of circuits and equipment, and safe equipment, such as volt-ohm-meters, external arcs and sparks also uses 40 procedures during troubleshooting and commonly used on low- and medium- volts as a minimum voltage range level testing, hazards such as flying debris, voltage circuits, is extremely hazardous. for shock hazard protection guidelines electrical arcing, and flashover can be MSHA prohibits troubleshooting and for electrical equipment frames. Dry avoided. Electrical arcing during testing of energized high-voltage circuits work gloves, in good condition (free of troubleshooting and testing is normally and equipment. The use of hand-held holes, etc.) will be permitted on circuits due to either misapplication or misuse proximity testers to determine shielding where the voltage does not exceed 120 of test equipment. In some cases, continuity and energized circuits is volts nominal and on circuits where the electrical hazards may occur as a result allowed under this regulation. voltage exceeds 120 volts nominal but is of circuit insulation failure while Troubleshooting and testing routinely intrinsically safe. The normal control troubleshooting. Under the final rule, involves the use of portable test circuit nominal voltage value is 120 only qualified individuals must be instruments equipped with attached volts for mining equipment. Section assigned to perform troubleshooting and leads and metal probes used to move 75.1720—Protective clothing, testing. Further, they must perform from point to point in a circuit for the requirements and MSHA policy allow thorough examinations, tests, and purpose of determining voltage and/or miners to use dry gloves when working maintenance of circuits and equipment current readings needed to target on circuits up to 1000 volts. Rubber to help guard against the occurrence of problem areas. Insulation ratings on insulating gloves rated for at least the injury due to electrical arcing caused by equipment commonly used to nominal voltage of the circuit and failure of insulation. troubleshoot and test are insufficient to equipped with leather protectors will be Paragraph (d)(4) of the final rule protect persons if this equipment is required to be used on circuits where requires that rubber insulated gloves, used on high-voltage circuits. The the voltage exceeds 120 volts nominal when required, be rated at least for the commenter stated that the MSHA but is not intrinsically safe. (See nominal voltage of the circuit. This program policy manual permitted paragraphs (b)(3) and (b)(4)). Mine requirement was contained in paragraph troubleshooting and testing of energized equipment typically has ratings such as (d)(3) of the proposed rule. Comments high-voltage circuits. After review, 220-, 480-, 995-volts and higher. Rubber pertaining to this proposed rule are MSHA determined that this policy was gloves are not commercially rated for addressed above. The language of this inadvertently drafted in error and each of these voltages. Rubber insulating provision remains the same as the specifically conflicts with mandatory gloves rated at 1,000 volts are proposed, but it is renumbered. safety standard § 75.705. The error was commercially available at this time. The Paragraph (e) of the final rule, like the corrected in MSHA Program Policy 1,000 volt rated gloves can be used on proposed rule, requires deenergization Update V–15. The printed-in-error each of these circuits and, in fact, offer of high-voltage circuits contained in a version was never officially considered increased protection for troubleshooting compartment with low-or medium- or enforced as MSHA policy. and testing on circuits exceeding 120 voltage circuits, in order to troubleshoot Other commenters suggested—(1) that volts. or test the low-or medium-voltage gloves not be required under the MSHA’s fatality data show that at circuits. Deenergizing, grounding, and standard when the maximum circuit least six fatalities have occurred since locking out and tagging the high-voltage voltage does not exceed 40 volts; (2) that 1970 due to miners’ contact with circuit provides protection against the dry work gloves in good condition be energized circuits while troubleshooting danger of accidental contact with the required when the maximum circuit and testing. The provisions of § 75.820 high-voltage circuits while voltage does not exceed 150 volts or the address electrocution and shock hazards troubleshooting and testing low- and circuit voltage exceeds 150 volts but is associated with troubleshooting and medium-voltage circuits. Some intrinsically safe; and (3) that insulating testing of the low- and medium-voltage commenters suggested that high-voltage gloves, with protective coverings portions of high-voltage longwalls and circuits should never be located in the designed to prevent physical damage to provide additional protection for same compartment with low- and the insulating material, be required persons performing work on these medium-voltage circuits in order to when the maximum circuit voltage circuits. prevent persons from contacting high- exceeds 150 volts and the circuit is not Commenters suggested that the voltage circuits while testing or working intrinsically safe. proposed rule be expanded to include on low- and medium-voltage circuits. In MSHA agrees with some of the facial protection, and protective response to this comment, electrical commenters’ suggestions and has clothing to minimize the risk of injury closing of high-voltage contactors written the final rule to reflect these in case of a short circuit during contained in motor-starter enclosures changes. The final rule requires the use troubleshooting and testing of an requires low-voltage magnetic of protective gloves when energized circuit. In support of this components that are a part of the troubleshooting and testing circuits suggestion, commenters stated that contactors. Therefore, sometimes it is having voltages that exceed 40 volts. these additional requirements were necessary, to have both high voltage in
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the form of a power circuit and low addition, the commenter pointed out work to frequently remove sections of voltage in the form of a control circuit that belt structure removal occurs 2 or conveyor structure. This commenter in the same compartment(s) of the 3 times a shift, taking 15 to 30 minutes indicated that procedures have been motor-starter enclosures. In addition, each time. Other commenters suggested developed to ensure that this work can compartments of motor-starter that this provision be deleted, since be done without risk of high-voltage enclosures that house high-voltage proper guarding is required by § 75.816. cables creating a hazard. disconnect switches may also contain These commenters suggested that the In response to these commenters, the low-and/or medium-voltage control and requirement would result in Agency has changed the language of the lighting transformers. The deenergizing cables even if work is proposed rule. The final rule allows deenergization and lockout being done 10,000 feet from the cables. guarding or protection by elevation as requirements under the new standard Another commenter suggested that this another means of protecting cables from address the safety concerns associated requirement should be waived if the damage and to minimize danger of with working near multiple voltage high-voltage cable is installed on contact with energized cables. Proper circuits. Therefore, the Agency monorail because personnel are safely guarding of cables in accordance with concludes that paragraph (e) of this protected by the location of the cable. § 75.816 or protection afforded by section should remain as proposed. Other reasons given for deleting the proper elevation would minimize miner Paragraph (f) of the final rule requires deenergization requirement were: (1) It contact with cables and minimize that high-voltage cables located in would be less safe for miners, as it damage to the cables. The Agency agrees conveyor belt entries be deenergized, would result in deenergization of that there are safety advantages in guarded, or isolated by elevation prior several longwall safety devices such as leaving the high-voltage cable energized to the installation or removal of the the face and equipment illumination if the cable is properly protected during conveyor belt structure. The proposed system; (2) It would result in an undue belt structure installation and removal. rule required that the cables be burden for operators due to the time Examples of safety equipment that deenergized prior to the removal of the required to travel to and from the power would remain energized are methane structure. Other commenters suggested center in order to deenergize the cable; monitors and illumination systems. that the deenergization requirement (3) It would cause undue stress, wear Section 75.821 Testing, Examination, should apply to the installation, as well and tear on electrical breakers, and Maintenance as the removal, of conveyor belt components, and cables due to frequent structures. These commenters pointed energizing and deenergizing; and (4) It Section 75.821 of the final rule out that the same type of work is would prevent most maintenance, requires that a person, qualified to performed during belt installation as service and support functions from perform electrical work, test and during removal. The Agency agrees with being performed while the cables were examine equipment and circuits to these commenters and has concluded deenergized. The commenter also detect and correct conditions that could that the final rule should apply to pointed out that the occurrence of high- lead to an accident and injury. The advancing as well as retreating longwall voltage cable faults is infrequent and the section requires the qualified person to systems. Therefore, the requirement has commenter has no experience of faults verify by signature and date that the been changed to apply to installation as resulting in fire or causing shocks to tests and examinations have been well as removal of conveyor belt miners. This commenter further stated completed. This record will include any structures. Contact with or damage to that currently required circuit breakers unsafe conditions and corrective actions energized cables while installing or and ground-fault systems provide taken. The section further requires that removing conveyor belt structures could adequate fault protection and that the records be kept and made available cause risks of fire and electrocution to backup protection is provided by a for at least one year. This section was miners. The final rule addresses these ‘‘Post Gulliver’’ ground-fault system at derived, in part, from existing dangers by requiring either the commenter’s operation. Another §§ 75.512—Electric equipment; deenergization, guarding, or proper commenter suggested that this examination, testing and maintenance, location of the cables before installing or requirement should only apply to cables 75.512–2—Frequency of examinations, removing belt structures. which are not guarded and which are 75.800–3—Testing, examination and Commenters suggested that located in conveyor belt entries less maintenance of circuit breakers; deenergizing the high-voltage cable for than three feet away from the conveyor procedures, and 75.800–4—Testing, removal of the belt conveyor structure is belt structure. examination, and maintenance of often impractical and that an alternative Another commenter suggested that circuit breakers; record which generally would be to guard the cable from direct the requirement should not apply where apply to electrical equipment contact with the belt conveyor structure the mine operator can demonstrate that underground. This section applies to during removal. Reasons given for this the seam height provides ample high-voltage equipment on the longwall alternative were: (1) Many of the routine clearance of at least 6.5 feet or other face or within 150 feet of the pillar jobs performed along the longwall face methods are used to prevent any workings. cannot be performed with the power off possible mechanical damage to high- Paragraph (a) of § 75.821 requires that (such as repositioning of the longwall voltage cables which may occur during persons, qualified in accordance with shearer, moving the shields removal of conveyor belt structures. existing § 75.153—Electrical work; electronically and moving the face Another commenter indicated that the qualified person, test and examine high- conveyor, as well as equipment phrasing of the proposed rule led the voltage longwall equipment and circuits servicing and welding operations that commenter to believe that MSHA was to protect miners from electrical or typically contribute to the normal safe referring to the complete removal of the operational hazardous that may exist. and efficient operation of the longwall) conveyor belt structure (as would be the As noted under the § 75.820 discussion, and (2) Methane monitors, face lighting, case for an advancing longwall). This based on the recent Federal Mine Safety and on-board shield diagnostics would commenter indicated that operators are and Health Review Commission Black lose power if they receive electrical concerned about application of the rule Mesa decision (22 FMSHRC 708, 715; power through the high-voltage system to the more common retreating longwall June 30, 2000), § 75.153 requires that a that feeds the face equipment. In situation where it is part of the routine ‘person qualified’ be knowledgeable of
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high-, medium-, and low-voltage injuries. The Agency considers it very cables protected by the described circuits and equipment. Consistent with important that the required guarding, be inspected to assure proper this decision and for clarification examinations and tests be conducted as maintenance. The Agency believes that purposes, the language of paragraph (a) frequently as possible from the verification of proper maintenance has been modified in the same fashion standpoint of safety and practicability, regarding these items would not require, as in § 75.820(a) to conform with the and that an examination at least once in all cases, removal of the equipment ruling under this decision and the plain every seven days rather than weekly covers and cable guards in order to meaning of § 75.153. Thus, under this provides this assurance. A requirement make this determination. Some paragraph as revised, a person must be for a weekly examination can result in protective device settings do not change, qualified under § 75.153 to perform the equipment not being examined for so frequent removal of covers to gain electrical work on ‘‘all’’ circuits and as long as 13–14 days. In addition, the access for inspection serves no useful equipment, not just high-voltage seven-day requirement is consistent purpose and reduces safety if covers are circuits. Testing and examining high- with similar type requirements not properly replaced. Removing and voltage longwall equipment and circuits contained in regulations promulgated by replacing guards that are installed to allows qualified persons to determine the Agency pertaining to ventilation provide mechanical protection for that the electrical protection, equipment under §§ 75.312(b)(1)(ii)—Main mine cables, without good reason, could grounding, permissibility, cable fan examinations and records and likewise result in an unsafe condition if insulation, and control devices are 75.364(a)—Weekly examination. not properly replaced. properly maintained to prevent fire, Another commenter suggested that the Since 1970, Title 30 CFR has electric shock, ignition or operational proposed provision was too vague and contained an examination, test, and hazards from existing on the equipment. in order to eliminate confusion, maintenance requirement for electric Keeping equipment free from these submitted the following examination equipment that is more basic than hazards is assured by the training and requirements: (1) Actuate each ground- § 75.821. The Agency has been asked on expertise of qualified electricians. fault test circuit required by § 75.814(c); several occasions to describe the Regular testing and examination of high- (2) Examine the cable guarding and required extent of proper examination of voltage equipment used in face areas handling system to ensure that they are circuits and equipment. Since there are assures that hazardous conditions are properly installed and protecting the so many varieties of circuits and discovered and corrected before they cables; (3) Determine that explosion- equipment in use in mines, it is can cause injuries to miners. The proof components are maintained in impractical to describe a specific standard requires examinations and permissible condition; (4) Actuate the inspection procedure that applies to all tests of high-voltage longwall equipment emergency stop button and verify that circuits and equipment in all instances. Consequently, a general type at least once every 7 days. the corresponding circuit-interrupting inspection procedure, such as that Examinations and tests include device opens; and (5) Verify that the contained in this final rule, is necessary. activating the ground-fault test circuit face communication system is The amount of detail needed for a given which is required by § 75.814(c) of this operational. Another commenter inspection is normally determined on a final rule. The standard assures that suggested that the proposed case-by-case basis, as the inspection problems which arise during normal use examination requirements were so takes place. For example, the testing of of mining equipment will be identified comprehensive that it would take a ground monitors would normally only and corrected, so that miners are not skilled person two days and that the exposed to hazards. Activating the require simple activation of readily more limited examination suggested by ground-fault test circuit will identify available test switches; however, the previous commenter would cover any damage or defects in the ground- findings revealed during this portion of the essential safety aspects. fault circuit and therefore protect the inspection of the longwall circuits miners from being exposed to energized In response to the comments and equipment may indicate a need for longwall equipment frames. regarding adoption of less time- more thorough examinations and tests. A commenter stated that 30 CFR part consuming examination requirements, For example, if an ohm meter test 75 requires mine operators to conduct a the complex high-voltage longwall determined that a condition existed in multitude of tests in the underground mining system contains numerous a cable, such as an inadvertent environment. The commenter further cables, conductors, and pieces of connection between a pilot wire and stated that these tests are normally equipment that require time-consuming ground wire rendering a ground monitor conducted on a ‘‘daily,’’ ‘‘weekly,’’ or examinations to assure safe operating inoperative, further examination and ‘‘monthly’’ basis, and that the proposed conditions. Although proper circuit and correction would be required to rule is confusing and can present a equipment maintenance requires both establish effective ground monitoring. problem for those operations working visual and physical examinations, most For these reasons, the Agency concludes under nontraditional schedules. The examinations are visual. In addition, that the final rule require general type commenter recommended that for testing of circuits and equipment examinations and tests be conducted. clarity and consistency, the phrase routinely includes activating available Therefore, except for the change based ‘‘once every 7 days’’ be removed and the test switches to verify proper operation on the Black Mesa decision, paragraph word ‘‘weekly’’ be substituted. In and causes the protective devices to (a) of this section remains as proposed. response to this comment, circuits and open. High-voltage longwall equipment Paragraph (b) of the final rule, like the equipment used in conjunction with contains circuit protective devices that proposed rule, requires that each high-voltage longwalls are frequently are mounted in heavily constructed ground-wire monitor and corresponding being moved and subjected to heavy explosion-proof enclosures containing circuit be examined and tested at least use, increasing the likelihood of wear large bolted covers and cables that are once each 30 days to verify that it is and breakdown. Because of this, it is protected by heavily constructed operating properly and will cause the extremely important that defects in guarding. The proposed rule required, corresponding circuit-interrupting circuits and equipment be detected as in part, that a determination be made device to open. This procedure assures quickly as possible and repaired before that protective devices, in some cases that ground-wire monitors and the occurrence of related accidents and contained within these enclosures, and corresponding circuit-interrupting
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devices will operate properly to rule. ‘‘Immediately’’ is intended to responsible persons from entering the deenergize the circuits that they reflect its plain meaning that the information as is currently allowed. monitor. A commenter suggested that required action be without hesitation or This commenter pointed out that the the requirement for testing of ground- delay. It is emphasized, however, that results of the examination could be wire monitors be relocated to another the rule is referring to those safety allowed to be entered by the examiner section of the rule, or possibly defects that are considered hazardous, or by a responsible mine official, or § 75.803—Fail safe ground check as stated under § 75.821(c). For information could be transferred from a circuits on high-voltage resistance example, some conditions, such as bare checklist filled out by the examiner. In grounded systems. The Agency has energized conductors in cables or response to this commenter, high- determined that the important safety conductors, present fire, electric shock, voltage longwalls contain complex protection provided by these devices ignition, and possibly even operational circuits and equipment that require and their use on operating high-voltage hazards and require either immediate examinations and tests be conducted longwall equipment necessitates placing removal from service or immediate only by qualified persons ground monitor testing requirements in repair. However, conditions may exist knowledgeable about equipment this section of the final rule. This is that would not require immediate function and operation. These persons required in addition to other relevant shutdown of equipment, but due to the routinely acquire this knowledge testing requirements for other protective nature of the condition, would permit through numerous hours of education, systems on high-voltage longwall continued operation of the equipment training, and experience. Once equipment. until material or parts necessary to inspections, including required Another commenter suggested that correct the condition are procured, or examinations and tests, of high-voltage the testing be limited to the operation of would permit orderly shutdown of longwalls are conducted by qualified appropriate control circuit test devices equipment prior to repair. For example, persons, it can be concluded that these in the power center or high-voltage § 75.816 of this final rule requires individuals are the only ones that have motor-starter enclosure, and indicated guarding of high-voltage cables in the necessary detailed knowledge and that it should not be necessary to open specific locations. Unless there are other understanding of the results of the any explosion-proof enclosure or to extenuating circumstances such as inspection. Because of this, it is disconnect any ground wire while damaged cable or bare conductors appropriate that only these persons testing a ground-wire monitor. These present, a torn portion of guarding certify by signature and date that the commenters suggested that language be material would not be judged a required examinations and tests have added to the provision that specifies the condition that would have to be been conducted and that unsafe test be initiated by operating the test corrected immediately. It is the conditions found have been corrected switch provided as part of the ground- Agency’s intent that once a condition and recorded. This approach is wire monitor, or a similar switch with the potential to result in a fire, consistent with other examination and installed in the power center or the electric shock, ignition, or operational recordkeeping requirements high-voltage motor-starter enclosure. As hazard is revealed correction of the promulgated by MSHA. stated above, proper examination and condition should begin immediately. testing of ground-wire monitors and This includes arranging for orderly Another commenter suggested that associated circuits, which include pilot shutdown or removal of the equipment the operator maintain a written record wires and grounding conductors, may for repair until the necessary repair of each test, examination, repair or require more than simple activation of parts are obtained and installed. adjustment of all circuit breakers a test switch that normally opens the Paragraph (d) of the final rule, like the protecting high-voltage circuits which pilot wire. Therefore, paragraph (b) of proposed rule, requires the person who enter any underground area of the coal this section remains as proposed. performs examinations and tests to mine and that such records be Paragraph (c) of the final rule requires certify by signature and date that they maintained in a book approved by the equipment to be immediately removed have been conducted. Also, a record is Secretary. These commenters indicated from service or immediately repaired required for any unsafe condition found that such records are necessary to assure when examinations or tests reveal a fire, and any corrective action taken. This that tests and examinations have been electric shock, ignition, or operational unsafe condition need not be an made and would indicate which pieces hazard. This provision assures that immediate hazard to be reported. In of electrical equipment were tested and equipment which may pose a danger to addition, certifications and records are examined and which ones were not. miners will not be used until the required to be kept for at least one year They suggested that a reduction in the hazardous condition is corrected. Some and made available at the mine for amount of recordkeeping diminishes the commenters stated that the term inspection by authorized representatives operator’s accountability to provide ‘‘immediately’’ should be added to this of the Secretary and representatives of proof that all equipment has been tested provision. These commenters indicated miners at the mine. Records and and examined. In response to this that it is of utmost importance that certifications of tests and repairs are commenter, even though existing whenever tests and examinations reveal valuable tools for mine operators and § 75.512 requires examination of all malfunctions and defects, equipment can be used to point out patterns of electric equipment, proposed §§ 75.814 must be repaired or removed from equipment defects and facilitate through 75.822 are specific to high- service immediately. They pointed out improvements in equipment voltage longwall circuits and equipment that operators may be reluctant to shut maintenance and design. These records and not just high-voltage circuit down a longwall operation to make and certifications will assist in breakers. Since proper test, necessary corrections and that identifying that the required examination, and maintenance of confrontational situations and any examinations were conducted, and will circuits and equipment is considered to misinterpretations could be avoided by also assist in the investigation of be of extreme importance for the adding this clarification to the standard. accidents. protection of personnel, the Agency The Agency agrees with the A commenter suggested that requiring concluded it was necessary to draft an commenter and has added the word the examiner’s signature is not examination and testing standard for ‘‘immediately’’ to § 75.821(c) of the final necessary and eliminates other high-voltage longwall circuits and
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equipment. As stated above, the modification. One of these commenters less burdensome ground-wire monitor wording of § 75.821(d), which in part, stated that the use of a center ground- system to the mining industry. This requires that the person who completes check conductor can either eliminate or small ground-check conductor size is the examination and tests certify by significantly minimize inter-machine not a requirement but is offered to give signature and date that they have been arcing and also provides improved added flexibility to mine operators and conducted. This approach is generally ground-check monitor performance by to minimize their cost burden where consistent with requirements in other reducing induced current into the feasible. This option became available to regulations promulgated by the Agency. ground-check conductor. the coal industry and coal mine This certification and recording The Agency agrees with these equipment manufacturers as it was requirement only pertains to high- comments, and includes a new section developed and used in high-voltage voltage longwall systems, including permitting this cable design use in light longwall systems under the petition for associated low- and medium-voltage of its experience with high-voltage modification process during the last circuits and equipment. The longwall petitions. As noted above, seven years. requirements of § 75.512 remain in these new cable design provisions arise With the advent of high-voltage effect for circuits and equipment in the from technology developments longwall face equipment, the mine other than that used on high- referenced by commenters in response development and use of No. 16 AWG voltage longwall systems. Therefore, to the proposed rule and from the high- ground-check conductors for high- paragraph (d) of this section remains as voltage longwall experience under the voltage longwall equipment became an proposed. petition process. This section includes affordable technology with additional requirements from § 75.804 and allows safety benefits. This standard also Section 75.822 Underground High- the use of high-voltage longwall eliminates the need for § 75.804(a) Voltage Longwall Cables equipment cables that are designed with petitions for modification on longwalls Section 75.822 of the final rule is a center ground-check insulated for this purpose and facilitates the use new, derived in part from existing conductor smaller than No. 10 AWG of improved high-voltage cable designs. § 75.804—Underground high-voltage and metallic shields around each power These cable designs should reduce the cables. It has been added since the conductor. Acceptable cables are those hazards associated with locating severed proposed rule in specific response to manufactured to meet nationally ground-check conductors, thereby commenters, and is a logical outgrowth recognized consensus standards, such as discouraging the bypassing of ground- of this high-voltage longwall the Insulated Cable Engineers wire monitors when a cable has rulemaking. This section differs from Association (ICEA) standards and, as experienced a broken or severed the requirements of § 75.804 by provided by the final rule, are designed ground-check conductor. Mines using permitting the use of high-voltage cables with a stranded ground-check conductor this cable design have reported less that have an insulated center ground- that is no smaller than No. 16 AWG and downtime by having to locate and repair check conductor that is smaller than a is located in the center interstice of the broken or severed ground-check No. 10 AWG conductor. The Agency cable conductors. The national conductors. developed this new provision in consensus standards are developed by A commenter recommended that the response to industry requests and to recognized experts in their fields. These word ‘‘metallic’’ not be used to describe accommodate new cable design cables, through the Mine Act § 101(c) the shielding that surrounds the technology that can either eliminate or petition for modification process, have individual power conductors and that significantly minimize inter-machine been used on longwall mining the rule should allow the use of other arcing due to the reduction of current equipment for the past several years and materials to be incorporated in the induced into the ground-check provide the necessary protection from construction of the shielding. The conductor. This new cable design physical damage or stress to the No. 16 commenter did not specify what other technology developed from MSHA and AWG center ground-check conductor. types of materials should be used as the industry’s experience with using For these reasons, the Agency has shielding around the power conductors. smaller ground-monitor conductor sizes determined that allowing the use of a Experience indicates that use of high- in high-voltage longwall cables under No. 16 AWG center ground-check voltage cables with metallic shielding MSHA granted modifications. This conductor can provide equivalent or that surrounds the individual power experience, together with comments improved protection as provided by a conductors provides the intended from the high-voltage longwall regular No. 10 AWG conductor. protection against electrical hazards. rulemaking process, caused MSHA to Improved protection is provided by the Thus, the Agency has retained the cable conclude that such cable designs should No. 16 AWG ground-check conductor design specifications that incorporate be permitted under the final rule. The because it is located in the center of the metallic shielding around each power development of affordable smaller cable creating cable conductor conductor. conductors resulted directly from the symmetry. This greatly minimizes high-voltage longwall equipment design induced currents and voltages that have Section 75.1002 Installation of Electric and use experience under granted been found to occur when using cables Equipment and Conductors; modifications. where the ground-check conductors are Permissibility Two commenters suggested that a located in the interstices between the This section of the final rule is regulation be developed to permit the phase conductors. These induced derived from existing §§ 75.1002— use of high-voltage cables that have a currents and voltages can result in Location of trolley wires, trolley feeder center ground-check conductor smaller arcing, fire or ignition hazards. Using wires, high-voltage cables and than a No. 10 AWG conductor that is cables with No. 10 AWG conductors has transformers and 75.1002–1—Location presently required under § 75.804(a). required the installation of external arc- of other electric equipment; The commenters further stated that suppression devices to prevent induced requirements for permissibility and MSHA has allowed the use of a smaller currents and voltages. Therefore, addresses requirements for conductors ground-check conductor for high- permitting cables with No. 16 AWG and cables used in or inby the last open voltage cables through the use of conductors located in the center of the crosscut, and electric equipment and § 101(c) of the Mine Act for petitions for cables, brings a safer, more efficient, and conductors and cables used within 150
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feet of pillar workings. The final rule under this final rule) will remain in DERIVATION TABLE—Continued revises existing § 75.1002 and removes effect, and mine operators who do not § 75.1002–1, which prohibited the use have granted petitions in effect must file Final rule Existing section of high-voltage cables inby the last open a petition for modification of crosscut and within 150 feet of pillar § 75.1002(b) for the future use of high- 75.814(a)(5) & (6) ..... N/A. workings or longwall faces. It also voltage continuous miners. 75.814(a)(7) ...... 75.800. In addition, the high-voltage longwall 75.814(b), (c) & (d) ... N/A. revises § 75.1002 related to the use of 75.814(e) ...... New (75.518–1). permissible equipment in these areas. final rule does not apply to 75.815(a) & (b) ...... 75.808. Paragraph (a) of the final rule, like the nonpermissible test and diagnostic 75.815(c) ...... 75.520. existing rule and proposed rule, equipment use. Previously granted 75.815(d)(1) ...... 75.601 & 75.808. continues to require that only petitions under existing § 75.1002–1(a) 75.815(d)(2) ...... 75.705. permissible electric equipment be (§ 75.1002(a) under this final rule) will 75.815(d)(3) ...... 75.511. located within 150 feet of pillar remain in effect. After the effective date 75.815(e) ...... 75.520. workings or longwall faces. This of this rule, mine operators who do not 75.816 & 75.817 ...... 75.807. equipment is specifically designed to have granted petitions in effect must file 75.818(a) ...... 75.705–6 and 75.812. 75.818(b) ...... 75.705–7 & 75.705– protect miners against fire and a petition for modification for the use of 8. explosion hazards in the mining face nonpermissible test and diagnostic 75.819 ...... N/A. areas such as the longwall face where equipment under § 75.1002(a). 75.820 ...... 75.153, 75.509, methane gas would likely accumulate In response to a commenter’s 75.511 & 75.705. and possibly cause an ignition or suggestion, MSHA has added the term 75.821 ...... 75.512, 75.512–1, explosion. ‘‘longwall faces’’ to paragraph (b) of the 75.800–3 & Paragraph (b) of the final rule, like the section. While longwall faces are 75.800–4. existing rule and proposed rule, limits generally considered to be part of a 75.822 ...... N/A. the types of electric conductors and pillar working, the use of this term more 75.1002 (revised) ...... 75.1002, 75.1002–1. cables permitted in areas where specifically identifies the place where N/A: Not Applicable. permissible equipment is required. This conductors and cables can be used. The Distribution Table section prohibits the installation of addition of this term also maintains conductors such as trolley wires and consistency with paragraph (a). This The following distribution table lists: trolley feeder wires in areas where term was used in proposed paragraph (1) Each section number of the existing permissible equipment is required. Such (a) to clarify that longwall faces are standards and (2) The section number of electric conductors could provide a included as part of the pillar working. the final rule which contains provisions ready ignition source and therefore must Paragraph (b)(1) of the final rule, like derived from the corresponding existing not be used where permissible the proposed rule, permits the use of section. equipment is required. Permissible shielded high-voltage cables supplying equipment is defined under 30 CFR power to permissible longwall DISTRIBUTION TABLE § 18.2—Definitions and under § 318(i) of equipment. Paragraphs (b)(2) through the Mine Act. Such equipment is (b)(4) of the final rule, like the existing Existing section Final rule specifically approved by MSHA for use standards, permit the use of conductors in fire and explosive hazardous areas. 75.2 ...... Partly new 75.2. and cables of intrinsically safe circuits, NA ...... 75.813. However, the new final paragraph (b)(1), and cables and conductors supplying 75.518–1 & 75.808 ... 75.814(a)(1). like the proposed rule, permits the use power to low- and medium-voltage NA ...... 75.814(a)(2). of shielded high-voltage longwall cable. permissible equipment in or inby the 75.802 ...... 75.814(a)(3). Such shielding and design protect last open crosscut and within 150 feet 75.800 ...... 75.814(a)(4). against arcing and other electrical of pillar workings or longwall faces. NA ...... 75.814(a)(5) & (6). ignition hazards that may occur when 75.800 ...... 75.814(7). the outer jacket material of the cable is Petitions for Modification NA ...... 75.814(b), (c) & (d). damaged. The use of shielded high- On the effective date of this final rule, New (75.518–1) ...... 75.814 (e). 75.808 ...... 75.815 (a) & (b). voltage cables supplying power to all existing petitions for modification for 75.520 ...... 75.815 (c). permissible longwall equipment reduces high-voltage longwall use under 75.601 & 75.808 ...... 75.815 (d)(1). the risk of fire or explosion in face areas § 75.1002 will be superseded. Operators 75.705 ...... 75.815 (d)(2). since these cables have equivalent or are thereafter required to comply with 75.511 ...... 75.815 (d)(3). superior mechanical and electrical the provisions of this final rule. 75.520 ...... 75.815 (e). protective characteristics. This 75.807 ...... 75.816 & 75.817. Derivation Table equipment offers other improved safety 75.705–6 & 75.812 ... 75.818 (a). features, such as short-circuit and The following derivation table lists: 75.705–7 & 75.705–8 75.818 (b). (1) Each section number of the final rule NA ...... 75.819. ground-fault protection against shock, 75.153, 75.509, 75.820. fire, and explosion hazards. The final and (2) The section number of the 75.511 75.705. rule continues to prohibit the use of standard from which the section is 75.512, 75.512–1, 75.821. such nonpermissible equipment not derived (existing section). 75.800–3 & specifically approved by MSHA for use 75.800–4. near the actual coal extraction areas DERIVATION TABLE NA ...... 75.822. where increased fire and explosion 75.1002 (Revised) & 75.1002. hazards exist. Final rule Existing section 75.1002–1 (Re- The high-voltage longwall final rule moved). 75.2 ...... Partly new. does not apply to high-voltage 75.813 ...... N/A. NA—Not Applicable. continuous miner use within 150 feet of 75.814(a)(1) ...... 75.518–1 & 75.800. III. Paperwork Reduction Act pillar workings. High-voltage 75.814(a)(2) ...... N/A. continuous miner petitions granted 75.814(a)(3) ...... 75.802. The information collection under existing § 75.1002 (§ 75.1002(b) 75.814(a)(4) ...... 75.800. requirements contained in this final rule
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have been submitted to the Office of costs from these provisions are given in The information collection Management and Budget (OMB) for the following table. The total first year requirements contained in this rule for review under the Paperwork Reduction paperwork burden hours and costs of part 75 were submitted to OMB for Act of 1995 (44 U.S.C. 3501–3520), as the rule are 5,736 hours and $163,929, review under the Paperwork Reduction implemented by OMB in regulations at respectively. The total burden hours and Act of 1995 and were approved under 5 CFR part 1320. The Paperwork costs in each year thereafter will be OMB Control Number 1219–0116. This Reduction Act of 1995 (PRA 95) defines 5,732 hours and $163,806, respectively. Control Number, however, expired in collection of information as ‘‘the 1994, and the information requirements obtaining, causing to be obtained, Manufacturers seeking approval for longwall equipment continue to be have been resubmitted to OMB for soliciting, or requiring the disclosure to reinstatement. In accordance with third parties or the public of facts or required to submit applications for § 1320.11(h) of the implementing opinions by or for an agency regardless approval including related drawings, of form or format.’’ drawing lists, specifications, wiring regulations, OMB has 60 days from This rule contains information diagrams, and descriptions. The today’s publication date in which to collection requirements for high-voltage paperwork burden for this application approve, disapprove, or instruct MSHA longwall operators in § 18.53(h), process is approved as part of a petition to make a change to the information § 75.820(b), § 75.820(e) and § 75.821(d). for modification, under OMB Control collection requirements in this final Annual paperwork burden hours and Number 1219–0065. rule.
TABLE OF ANNUAL BURDEN HOURS AND COSTS FROM THE RULE
Annual burden Annual burden Annual burden hours for Annual burden costs for Hours in each year costs in each year first year thereafter first year thereafter
Section 18.53(h) ...... 7 3 $247 $124 Section 75.820(b) and (e) ...... 1604 1604 45,831 45,831 Section 75.821(d) ...... 4125 4125 117,851 117,851
Total ...... 5736 5732 163,929 163,806
IV. Executive Order 12866 and because such mines do not use longwall equipment. In certain situations, the Regulatory Flexibility Act equipment. cables may also be smaller, for example, 5,000-volt (high-voltage) power cables Benefits Executive Order 12866 requires that are smaller and weigh less than 1,000- regulatory agencies assess both the costs The more stringent criteria and design volt (medium-voltage) power cables. As and benefits of regulations. MSHA has features associated with high-voltage a result of fewer and lighter power determined that this final rule will not systems, such as compartment covers cables, the risk of injuries from handling have an annual effect of $100 million or that are interlocked to prevent access to power cables during longwall more on the economy and that, energized high-voltage conductors and installation, movement, or replacement therefore, they are not an economically equipment designed to facilitate safe may be reduced. significant regulatory action pursuant to testing procedures, decrease the § 3(f)(1) of Executive Order (E.O.) 12866. likelihood of electrical accidents. In Increased productivity gains can be However, we have determined that this addition, high-voltage cables are realized when using high voltage rather final rule is significant under § 3(f)(4) of required to be shielded around each than medium voltage. In cases where E.O. 12866, which defines a significant conductor (SHD type) whereas medium- medium voltage is used to power larger regulatory action as one that may voltage cables can be shielded around motors and heavier duty longwall ‘‘* * * raise novel legal or policy issues the circumference of the cable (SHC equipment, current (amperes) can arising out of legal mandates, the type). The SHD cables are safer than the increase, causing motors and/or cables President’s priorities, or the principles SHC cables because shielding the to overheat. However, if high voltage set forth in the Executive Order.’’ MSHA individual power conductors reduces rather than medium voltage is used to completed a Regulatory Economic the possibility of a short circuit that can power the larger motors and heavier Analysis (REA) in which the economic cause a fire, or a shock and burn hazard duty longwall equipment, current impact of the rule is estimated. The REA when a miner touches a cable. The SHD (amperes) is reduced, and the risk of is available from MSHA and is shielding reduces the possibility of a overheating motors and/or cables summarized as follows. shock hazard because an exposed diminishes. Also, motor start-up is easier when using high voltage. This Population-at-Risk energized conductor will contact the SHD shielding and activate the ground- increased reliability may reduce the MSHA estimates that this rulemaking fault protection, which removes power amount of longwall equipment would initially affect approximately to the cable. The use of high-voltage downtime, thereby enhancing coal 14,229 miners at 43 underground coal SHD cables reduces the chances of cable productivity. mines and six mines employing about damage which, in turn, reduces the Section 75.818(b)(1) and (2) requires 1,667 miners that would begin using chances of a miner coming into contact that high-voltage insulated gloves, high-voltage longwall equipment in the with an energized conductor(s). sleeves, and other insulated personal first year of the rule. The rule would not Further, the use of high voltage in protective equipment be rated as Class increase costs to small mines, which longwall mining operations may reduce 1 or higher, be visibly examined before MSHA has traditionally defined as the number of power cables running each use for signs of damage, and that having fewer than 20 employees, between various pieces of longwall such protective equipment be removed
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from the underground area of the mine In addition, eliminating the petition final rule will reduce recordkeeping and when damaged or defective. process would produce further savings petition requirements. Section 75.818(b)(3) requires that for medium-voltage longwall units that The final rule is clearly economically insulated personal protective equipment convert to high-voltage units. The rule feasible insofar as it provides a yearly be electrically tested every six months. would eliminate delayed production net savings of $23.08 million to high- Section 75.820(d)(3) requires qualified that could occur as a result of a mine voltage longwall mines. This includes a electricians to wear properly rated not being able to synchronize initial one-time savings of $6.75 million for rubber gloves in order to perform start-up of its high-voltage longwall each longwall mine that converts to troubleshooting and testing on low- and equipment with the granting of a high voltage as well as annual costs of medium-voltage circuits in a high- petition. The medium-voltage longwall $258 for each high-voltage longwall voltage compartment. Currently, units that convert would have the mine. opportunity to obtain higher petitions for modification do not have Regulatory Flexibility Act and Small productivity yields from the use of high this requirement. Thus, § 75.820(d)(3) Business Regulatory Enforcement voltage sooner under the rule than provides additional safety protection Fairness Act (SBREFA) during this troubleshooting and testing. under current procedures. Based on an Finally, the rule continues the same average 66.1 percent increased The Regulatory Flexibility Act (RFA) electrical safety requirements developed productivity of high-voltage longwalls requires regulatory agencies to consider in the petitions for modification to use over lower-voltage longwalls and an a rule’s impact on small entities. For the high-voltage longwalls. average delayed production time of 78 purposes of the RFA and this working days, MSHA estimates that the certification, MSHA has analyzed the Compliance Costs one-time conversion accelerated impact of the final rule and has This rule will result in yearly net production savings due to the petition determined that there will be a cost savings of $23,083,980. This includes a process would be about $6,733,280 per savings to small entities affected by this savings per conversion of $6,753,851 high-voltage longwall unit. rule. MSHA will mail a copy of the final attributed to each medium-voltage With respect to individual provisions rule, including the preamble and longwall unit that converts to high- concerning the 43 existing mines that regulatory flexibility certification voltage usage. These conversion savings currently use high-voltage equipment statement, to all underground coal mine consist of $6,733,280 for accelerated and the medium-voltage longwall units operators and miners’ representatives. production savings per unit, and that would shift to high voltage, The final rule will also be placed on $20,571 for filed petition savings per § 75.818(b)(4) would require mines to MSHA’s Internet Homepage at http:// unit. perform an electrical test of personal protective equipment every six months. www.msha.gov, under Statutory and The net economic effect of the rule Section 75.820(d)(3) would require Regulatory Information. includes substantially increased electricians to wear properly-rated In accordance with § 605 of the RFA, productivity and cost savings for each rubber gloves to perform MSHA certifies that this final rule will longwall unit that converts to high- troubleshooting and testing on low- and not have a significant adverse economic voltage equipment and cables, and a medium-voltage circuits that are impact on a substantial number of small small cost annually for each longwall contained in a compartment with high- entities. No small governmental unit that uses high-voltage equipment voltage circuits. Compliance cost jurisdictions or nonprofit organizations and cables. Accelerated production increases of $90 per longwall unit and are affected. savings are savings due to the more $168 per longwall unit are identified Under the Small Business Regulatory productive high-voltage equipment with §§ 75.818(b)(4) and 75.820(d)(3), Enforcement Fairness Act amendments being used sooner rather than later. respectively. to the RFA, MSHA must include in the Filed petition savings refer to savings final rule a factual basis for this due to eliminating legal fees and Economic Impact certification. The Agency also must expenses connected with a filed The rule enhances productivity in publish the regulatory flexibility petition. The elimination of the need to those affected mines because it allows certification in the Federal Register, file petitions for modification to use more efficient high-voltage longwall along with its factual basis. high-voltage longwalls will reduce the equipment to be established more Factual Basis for Certification costs associated with the petition rapidly in the relatively few process and will require less paperwork. underground coal mines in which it can The Agency compared the gross costs MSHA estimates that the petition be profitably employed. MSHA has of the rule for small mines in each process would have imposed costs for concluded that the rule will have only sector to the revenue for that sector for legal fees and expenses of about $5,250 a small (but favorable) effect on coal both size categories analyzed (MSHA for an unopposed petition filing and output, price, and profitability. and Small Business Administration $112,500 for an opposed petition ‘small entity’ definitions). Given that the requiring litigation, including Feasibility gross compliance costs for small mines proceedings before Administrative Law MSHA has concluded that the is substantially less than 1 percent of Judges, the Assistant Secretary, and requirements of the final rule are both revenue and that net costs are negative, courts of appeal. Since 14.3 percent (1 technologically and economically MSHA concludes that there is no out of 7) of all petitions granted by feasible. significant cost impact of the rule on MSHA in 1998 were contested and This final rule is not a technology- small entities that use high-voltage required an ALJ’s decision, MSHA forcing standard and does not involve longwall units. assumes this same percentage would be activities on the frontiers of scientific Other small entities potentially contested were future petitions to be knowledge. The equipment testing, affected by the rule are small filed. Thus, elimination of the petition recordkeeping, and rubber glove manufacturers of high-voltage longwall process would generate a one-time filed requirements all involve standard equipment. MSHA concludes that the petition savings per high-voltage procedures or simple, off-the-shelf rule would not have a significant impact longwall unit of $20,571. technologies. Other provisions of the upon a substantial number of small
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manufacturers of high-voltage longwall manufacturers high-voltage longwall PART 18—ELECTRIC MOTOR-DRIVEN equipment. equipment. MINE EQUIPMENT AND MSHA also has determined that there Executive Order 12630 ACCESSORIES are no initial net compliance costs as a result of this rule. The final rule results This rule is not subject to Executive 1. The authority citation for part 18 in a net savings. Currently mine Order 12630, Governmental Actions and continues to read as follows: operators are required to file a petition Interference with Constitutionally Authority: 30 U.S.C. 957, 961. for modification to use high-voltage Protected Property Rights, because it does not involve implementation of a 2. Add § 18.53 to subpart B of part 18 longwall equipment. This is a costly and to read as follows: lengthy administrative process. This policy with takings implications. final rule increases safety, effectiveness, Executive Order 12988 § 18.53 High-voltage longwall mining and efficiency in the use of high-voltage systems. longwall equipment. The lengthy This regulation has been drafted and (a) In each high-voltage motor-starter approval process will be eliminated. reviewed in accordance with Executive enclosure, with the exception of a The Agency estimates that six existing Order 12988, Civil Justice Reform, and controller on a high-voltage shearer, the longwall mines will convert to high will not unduly burden the Federal disconnect device compartment, voltage and an additional three new court system. The regulation has been control/communications compartment, longwall mines each year will elect to written so as to minimize litigation and and motor contactor compartment must adopt high-voltage technology in the provide a clear legal standard for be separated by barriers or partitions to future. affected conduct, and has been reviewed prevent exposure of personnel to carefully to eliminate drafting errors and Unfunded Mandates Reform Act of 1995 energized high-voltage conductors or ambiguities. parts. In each motor-starter enclosure on For purposes of the Unfunded Executive Order 13211 (Energy) a high-voltage shearer, the high-voltage Mandates Reform Act of 1995, as well components must be separated from as E.O. 12875, this rule does not include In accordance with Executive Order lower voltage components by barriers or any Federal mandate that may result in 13211, MSHA has reviewed this final partitions to prevent exposure of increased expenditures by State, local, rule for its energy impacts. We have personnel to energized high-voltage and tribal governments, or increased determined that the Executive Order conductors or parts. Barriers or expenditures by the private sector of does not apply to this final rule for the partitions must be constructed of more than $100 million. MSHA is not following reasons. One, this rulemaking grounded metal or nonconductive aware of any State, local, or tribal is not considered a ‘‘significant insulating board. government that either owns or operates regulatory action’’ under Executive (b) Each cover of a compartment in underground coal mines. Order 12866 and therefore the action the high-voltage motor-starter enclosure does not meet the criteria listed in Executive Order 13132 containing high-voltage components Executive Order 13211 requiring a must be equipped with at least two MSHA has reviewed this rule in Statement of Energy Effects. Two, the interlock switches arranged to accordance with Executive Order 13132 proposed rule was published before the automatically deenergize the high- regarding federalism, and has effective date of the Executive Order. voltage components within that determined that it does not have Three, MSHA has determined that this compartment when the cover is ‘‘federalism implications.’’ The rule final rule will not have any adverse removed. does not ‘‘have substantial direct effects effects on energy supply, distribution, or (c) Circuit-interrupting devices must on the States, on the relationship use. To the contrary, as summarized in be designed and installed to prevent between the national government and the economic analysis, MSHA expects automatic reclosure. the States, or on the distribution of accelerated coal production because of (d) Transformers with high-voltage power and responsibilities among the the implementation of this final rule. primary windings that supply control various levels of government.’’ There are Therefore, no reasonable alternatives to voltages must incorporate grounded no underground coal mines or this action are necessary. electrostatic (Faraday) shielding manufacturers of high-voltage longwall List of Subjects between the primary and secondary equipment owned or operated by any windings. The shielding must be State governments. 30 CFR Part 18 connected to equipment ground by a Executive Order 13045 Approval regulations, Electric motor- minimum No. 12 AWG grounding driven mine equipment and accessories, conductor. The secondary nominal In accordance with Executive Order Mine safety and health. voltage must not exceed 120 volts, line 13045, MSHA has evaluated the to line. environmental health and safety effect 30 CFR Part 75 (e) Test circuits must be provided for of the final rule on children. The High-voltage longwall, Incorporation checking the condition of ground-wire Agency has determined that the final by reference, Mandatory safety monitors and ground-fault protection rule will have no effect on children. standards, Mine safety and health, without exposing personnel to energized circuits. Each ground-test Executive Order 13084 Underground coal mines. circuit must inject a primary current of Dated: February 25, 2002. In accordance with Executive Order 50 percent or less of the current rating 13084, MSHA certifies that the high- Dave D. Lauriski, of the grounding resistor through the voltage longwall final rule does not Assistant Secretary of Labor for Mine Safety current transformer and cause each impose substantial direct compliance and Health. corresponding circuit-interrupting costs on Indian tribal governments. For the reasons set out in the device to open. MSHA is not aware of any Indian tribal preamble, chapter I of title 30 of the (f) Each motor-starter enclosure, with governments which either own or Code of Federal Regulations is amended the exception of a controller on a high- operate underground coal mines or as follows: voltage shearer, must be equipped with
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a disconnect device installed to (v) When located in a non-explosion- volts must be made of a shielded deenergize all high-voltage power proof enclosure, the device must be construction with a grounded metallic conductors extending from the designed and installed to cause the shield around each power conductor. enclosure when the device is in the current to be interrupted automatically (j) High-voltage motor and shearer ‘‘open’’ position. prior to the opening of the contacts, or circuits must be provided with (1) When multiple disconnect devices the device must be capable of instantaneous ground-fault protection of located in the same enclosure are used interrupting the full-load current of the not more than 0.125-amperes. Current to satisfy the above requirement they circuit. transformers used for this protection must be mechanically connected to (g) Control circuits for the high- must be of the single-window type and provide simultaneous operation by one voltage motor starters must be must be installed to encircle all three interlocked with the disconnect device handle. phase conductors. so that— (2) The disconnect device must be (k) Safeguards against corona must be rated for the maximum phase-to-phase (1) The control circuit can be operated with an auxiliary switch in the ‘‘test’’ provided on all 4,160 voltage circuits in voltage and the full-load current of the explosion-proof enclosures. circuit in which it is located, and position only when the disconnect installed so that— device is in the open and grounded (l) The maximum pressure rise within position; and an explosion-proof enclosure containing (i) Visual observation determines that (2) The control circuit can be operated the contacts are open without removing high-voltage switchgear must be limited with the auxiliary switch in the to 0.83 times the design pressure. any cover; ‘‘normal’’ position only when the (ii) The load-side power conductors disconnect switch is in the closed (m) High-voltage electrical are grounded when the device is in the position. components located in high-voltage ‘‘open’’ position; (h) A study to determine the explosion-proof enclosures must not be (iii) The device can be locked in the minimum available fault current must coplanar with a single plane flame- ‘‘open’’ position; be submitted to MSHA to ensure arresting path. (iv) When located in an explosion- adequate protection for the length and (n) Rigid insulation between high- proof enclosure, the device must be conductor size of the longwall motor, voltage terminals (Phase-to-Phase or designed and installed to cause the shearer and trailing cables. Phase-to-Ground) must be designed current to be interrupted automatically (i) Longwall motor and shearer cables with creepage distances in accordance prior to the opening of the contacts; and with nominal voltages greater than 660 with the following table:
MINIMUM CREEPAGE DISTANCES
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 ...... -–- 1.50 1.95 2.40 2.90 -–G 1.00 1.25 1.55 1.85 4,160 ...... -–- 2.40 3.15 3.90 4.65 -–G 1.50 1.95 2.40 2.90 1 Assumes that all insulation is rated for the applied voltage or higher. (o) Explosion-proof motor-starter enclosures must be designed to establish the minimum free distance (MFD) between the wall or cover of the enclosure and uninsulated electrical conductors inside the enclosure in accordance with the following table: HIGH-VOLTAGE MINIMUM FREE DISTANCES (MFD)
Steel MFD (in) Aluminum MFD (in) Wall/cover thickness (in) A 1 B 2 C 3 ABC
1⁄4 ...... 2.8 4.3 5.8 4 NA 4 NA 4 NA 3⁄8 ...... 1.8 2.3 3.9 8.6 12.8 18.1 1⁄2 ...... * 1.2 2.0 2.7 6.5 9.8 13.0 5⁄8 ...... * 0.9 1.5 2.1 5.1 7.7 10.4 3⁄4 ...... * 0.6 * 1.1 1.6 4.1 6.3 8.6 1 ...... (*) * 0.6 * 1.0 2.9 4.5 6.2 Note *: The minimum electrical clearances must still be maintained. 1 Column A specifies the MFD for enclosures that have available 3-phase bolted short-circuit currents of 10,000 amperes rms or less. 2 Column B specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit currents greater than 10,000 and less than or equal to 15,000 amperes rms. 3 Column C specifies the MFD for enclosures that have a maximum available 3-phase bolted short-circuit currents greater than 15,000 and less than or equal to 20,000 amperes rms. 4 Not Applicable—MSHA doesn’t allow aluminum wall or covers to be 1⁄4 inch or less in thickness (Section 18.31). (1) For values not included in the table, the following formulas on which the table is based may be used to determine the minimum free distance.
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(i) Steel Wall/Cover:
− ()35+ 105 (C) (I (t)) d MFD =×2. 296 10 6 sc − ()()Cd 2
(ii) Aluminum Wall/Cover:
− ()35+ 105 (C) (I (t)) d MFD =×1. 032 10 5 sc − ()()Cd 2
Where C is 1.4 for 2,400 volt systems or (B) Permanent deformation exceeding Short circuit. An abnormal connection 3.0 for 4,160 volt systems, Isc is the 3- 0.040 inches per linear foot; or of relatively low impedance, whether phase short circuit current in amperes of (C) Excessive clearances along flame- made accidentally or intentionally, the system, t is the clearing time in arresting paths following retightening of between two points of different seconds of the outby circuit-interrupting fastenings, as necessary. potential. device and d is the thickness in inches PART 75—MANDATORY SAFETY * * * * * of the metal wall/cover adjacent to an 5. Part 75, Subpart I, Underground area of potential arcing. STANDARDS—UNDERGROUND COAL MINES High-Voltage Distribution, is amended (2) The minimum free distance must by adding §§ 75.813 through 75.822 and be increased by 1.5 inches for 4,160 volt 3. The authority citation for part 75 Appendix A under a new undesignated systems and 0.7 inches for 2,400 volt continues to read as follows: center heading, high-voltage longwalls, systems when the adjacent wall area is Authority: 30 U.S.C. 811. to read as follows: the top of the enclosure. If a steel shield Sec. is mounted in conjunction with an 4. Amend § 75.2 by adding the aluminum wall or cover, the thickness following definitions: High-Voltage Longwalls of the steel shield is used to determine § 75.2 Definitions. 75.813 High-voltage longwalls; scope. the minimum free distances. 75.814 Electrical protection. * * * * * 75.815 Disconnect devices. (p) The following static pressure test Adequate interrupting capacity. The 75.816 Guarding of cables. must be performed on each prototype ability of an electrical protective device, 75.817 Cable handling and support systems. design of explosion-proof enclosures based upon its required and intended 75.818 Use of insulated cable handling containing high-voltage switchgear prior application, to safely interrupt values of equipment. to the explosion tests. The static current in excess of its trip setting or 75.819 Motor-starter enclosures; barriers pressure test must also be performed on melting point. and interlocks. 75.820 Electrical work; troubleshooting and every explosion-proof enclosure * * * * * containing high-voltage switchgear, at testing. Approval documentation. Formal 75.821 Testing, examination and the time of manufacture, unless the papers issued by the Mine Safety and maintenance. manufacturer uses an MSHA accepted Health Administration which describe 75.822 Underground high-voltage longwall quality assurance procedure covering and illustrate the complete assembly of cables. inspection of the enclosure. Procedures electrical machinery or accessories Appendix A to Subpart I—Diagrams of Inby must include a detailed check of parts which have met the applicable and Outby Switching against the drawings to determine that requirements of 30 CFR part 18. * * * * * the parts and the drawings coincide and * * * * * High-Voltage Longwalls that the minimum requirements stated Circuit-interrupting device. A device in part 18 have been followed with designed to open and close a circuit by § 75.813 High-voltage longwalls; scope. respect to materials, dimensions, nonautomatic means and to open the Sections 75.814 through 75.822 of this configuration and workmanship. circuit automatically at a predetermined part are electrical safety standards that (1) Test procedure. (i) The enclosure overcurrent value without damage to the apply to high-voltage longwall circuits must be internally pressurized to at least device when operated within its rating. and equipment. All other existing the design pressure, maintaining the * * * * * standards in 30 CFR must also apply to pressure for a minimum of 10 seconds. Ground fault or grounded phase. An these longwall circuits and equipment (ii) Following the pressure hold, the unintentional connection between an where appropriate. pressure must be removed and the electric circuit and the grounding pressurizing agent removed from the system. § 75.814 Electrical protection. enclosure. Motor-starter enclosure. An enclosure (a) High-voltage circuits must be (2) Acceptable performance. (i) The containing motor starting circuits and protected against short circuits, enclosure during pressurization must equipment. overloads, ground faults, and not exhibit— Nominal voltage. The phase-to-phase undervoltages by circuit-interrupting (A) Leakage through welds or casting; or line-to-line root-mean-square value devices of adequate interrupting or assigned to a circuit or system for capacity as follows: (B) Rupture of any part that affects the designation of its voltage class, such as (1) Current settings of short-circuit explosion-proof integrity of the 480 or 4,160 volts. Actual voltage at protective devices must not exceed the enclosure. which the circuit or system operates setting specified in approval (ii) The enclosure following removal may vary from the nominal voltage documentation, or seventy-five percent of the pressurizing agents must not within a range that permits satisfactory of the minimum available phase-to- exhibit— operation of equipment. phase short-circuit current, whichever is (A) Visible cracks in welds; * * * * * less.
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(2) Time-delay settings of short-circuit phase conductors. Equipment safety the circuit that is supplied power protective devices used to protect any grounding conductors must not pass through the device. cable extending from the section power through or be connected in series with (d) Each disconnecting device must be center to a motor-starter enclosure must ground-fault current transformers. designed and installed so that — not exceed the settings specified in (c) Each ground-fault current device (1) Visual observation determines that approval documentation, or 0.25- specified in paragraphs (a)(4)(i) and (5) the contacts are open without removing second, whichever is less. Time delay of this section must be provided with a any cover; settings of short-circuit protective test circuit that will inject a primary (2) All load power conductors can be devices used to protect motor and current of 50 percent or less of the grounded when the device is in the shearer circuits must not exceed the current rating of the grounding resistor ‘‘open’’ position; and settings specified in approval through the current transformer and (3) The device can be locked in the documentation, or 3 cycles, whichever cause each corresponding circuit- ‘‘open’’ position. interrupting device to open. is less. (e) Disconnecting devices, except (3) Ground-fault currents must be (d) Circuit-interrupting devices must those installed in explosion-proof limited by a neutral grounding resistor not reclose automatically. enclosures, must be capable of to not more than— (e) Where two or more high-voltage (i) 6.5 amperes when the nominal cables are used to supply power to a interrupting the full-load current of the voltage of the power circuit is 2,400 common bus in a high-voltage circuit or designed and installed to volts or less; or enclosure, each cable must be provided cause the current to be interrupted (ii) 3.75 amperes when the nominal with ground-wire monitoring. The automatically prior to the opening of the voltage of the power circuit exceeds ground-wire monitoring circuits must contacts of the device. Disconnecting 2,400 volts. cause deenergization of each cable when devices installed in explosion-proof (4) High-voltage circuits extending either the ground-monitor or grounding enclosures must be maintained in from the section power center must be conductor(s) of any cable become accordance with the approval provided with— severed or open. On or after May 10, requirements of paragraph (f)(2)(iv) of (i) Ground-fault protection set to 2002, parallel connected cables on § 18.53 of part 18 of this chapter. cause deenergization at not more than newly installed longwalls must be § 75.816 Guarding of cables. 40 percent of the current rating of the protected as follows: neutral grounding resistor; (1) When one circuit-interrupting (a) High-voltage cables must be (ii) A backup ground-fault detection device is used to protect parallel guarded at the following locations: device to cause deenergization when a connected cables, the circuit- (1) Where persons regularly work or ground fault occurs with the neutral interrupting device must be electrically travel over or under the cables. grounding resistor open; and interlocked with the cables so that the (2) Where the cables leave cable (iii) Thermal protection for the device will open when any cable is handling or support systems to extend grounding resistor that will deenergize disconnected; or to electric components. the longwall power center if the resistor (2) When two or more parallel circuit- (b) Guarding must minimize the is subjected to a sustained ground fault. interrupting devices are used to protect possibility of miners contacting the The thermal protection must operate at parallel connected cables, the circuit- cables and protect the cables from either 50 percent of the maximum interrupting devices must be damage. The guarding must be made of temperature rise of the grounding mechanically and electrically grounded metal or nonconductive resistor, or 150° C (302° F), whichever interlocked. Mechanical interlocking flame-resistant material. is less, and must open the ground-wire must cause all devices to open monitor circuit for the high-voltage § 75.817 Cable handling and support simultaneously and electrical systems. circuit supplying the section power interlocking must cause all devices to center. The thermal protection must not open when any cable is disconnected. Longwall mining equipment must be be dependent upon control power and provided with cable-handling and may consist of a current transformer and § 75.815 Disconnect devices. support systems that are constructed, overcurrent relay. (a) The section power center must be installed and maintained to minimize (5) High-voltage motor and shearer equipped with a main disconnecting the possibility of miners contacting the circuits must be provided with device installed to deenergize all cables cables and to protect the high-voltage instantaneous ground-fault protection extending to longwall equipment when cables from damage. set at not more than 0.125-ampere. the device is in the ‘‘open’’ position. See § 75.818 Use of insulated cable handling (6) Time-delay settings of ground-fault Figures I–1 and I–2 in Appendix A to equipment. protective devices used to provide this subpart I. coordination with the instantaneous (b) Disconnecting devices for motor- (a) Energized high-voltage cables must ground-fault protection of motor and starter enclosures must be maintained in not be handled except when motor or shearer circuits must not exceed 0.25- accordance with the approval shearer cables need to be trained. When second. requirements of paragraph (f) of § 18.53 cables need to be trained, high-voltage (7) Undervoltage protection must be of part 18 of this chapter. The insulated gloves, mitts, hooks, tongs, provided by a device which operates on compartment for the disconnect device slings, aprons, or other personal loss of voltage to cause and maintain the must be provided with a caution label protective equipment capable of interruption of power to a circuit to to warn miners against entering the providing protection against shock prevent automatic restarting of the compartment before deenergizing the hazard must be used to prevent direct equipment. incoming high-voltage circuits to the contact with the cable. (b) Current transformers used for the compartment. (b) High-voltage insulated gloves, ground-fault protection specified in (c) Disconnecting devices must be sleeves, and other insulated personal paragraphs (a)(4)(i) and (5) of this rated for the maximum phase-to-phase protective equipment must— section must be single window-type and voltage of the circuit in which they are (1) Have a voltage rating of at least must be installed to encircle all three installed, and for the full-load current of Class 1 (7,500 volts) that meets or
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exceeds ASTM F496–97, ‘‘Standard § 75.819 Motor-starter enclosures; barriers each person must install an individual Specification for In-Service Care of and interlocks. padlock. Insulating Gloves and Sleeves’’ (1997). Compartment separation and cover (4) Tag the disconnecting device to interlock switches for motor-starter (2) Be examined before each use for identify each person working and the enclosures must be maintained in visible signs of damage; circuit or equipment on which work is accordance with the approval being performed. (3) Be removed from the underground requirements of paragraphs (a) and (b) of (c) Each padlock and tag must be area of the mine or destroyed when § 18.53 of part 18 of this chapter. removed only by the person who damaged or defective; and § 75.820 Electrical work; troubleshooting installed them, except that, if that (4) Be electrically tested every 6 and testing. person is unavailable at the mine, the months in accordance with publication (a) Electrical work on all circuits and lock and tag may be removed by a ASTM F496–97. ASTM F496–97 equipment associated with high-voltage person authorized by the operator, (Standard Specification for In-Service longwalls must be performed only by provided— Care of Insulating Gloves and Sleeves, persons qualified under § 75.153 to (1) The authorized person is qualified 1997) is incorporated by reference and perform electrical work on all circuits under paragraph (a) of this section; and may be inspected at any Coal Mine and equipment. (2) The operator ensures that the Health and Safety District and (b) Prior to performing electrical person who installed the lock and tag is aware of the removal before that person Subdistrict Office, or at MSHA’s Office work, except for troubleshooting and resumes work on the affected circuit or of Standards, 4015 Wilson Boulevard, testing of energized circuits and equipment. Arlington, VA., and at the Office of the equipment as provided for in paragraph (d) of this section, a qualified person (d) Troubleshooting and testing of Federal Register, 800 North Capitol energized circuits must be performed Street, NW., Suite 700, Washington, DC. must do the following: (1) Deenergize the circuit or only— In addition, copies of the document can equipment with a circuit-interrupting (1) On low- and medium-voltage be purchased from the American device. circuits; Society for Testing and Materials, 100 (2) Open the circuit disconnecting (2) When the purpose of Barr Harbor Drive, West Conshohocken, device. On high-voltage circuits, ground troubleshooting and testing is to Pennsylvania 19428–2959. This the power conductors until work on the determine voltages and currents; and incorporation by reference was circuit is completed. (3) By persons qualified to perform approved by the Director of the Federal (3) Lock out the disconnecting device electrical work and who wear protective Register in accordance with 5 U.S.C. with a padlock. When more than one gloves on circuits that exceed 40 volts 552(a) and 1 CFR part 51. qualified person is performing work, in accordance with the following table:
Circuit voltage Type of glove required
Greater than 120 volts (nominal) (not intrinsically safe) ...... Rubber insulating gloves with leather protectors. 40 volts to 120 volts (nominal) (both intrinsically safe and non-intrinsically safe) ... Either rubber insulating gloves with leather protectors or dry work gloves. Greater than 120 volts (nominal) (intrinsically safe) ...... Either rubber insulating gloves with leather protectors or dry work gloves.
(4) Rubber insulating gloves must be § 75.821 Testing, examination and service immediately or repaired rated at least for the nominal voltage of maintenance. immediately. the circuit when the voltage of the (a) At least once every 7 days, a (d) At the completion of examinations circuit exceeds 120 volts nominal and is person qualified in accordance with and tests required by this section, the not intrinsically safe. § 75.153 to perform electrical work on person who makes the examinations all circuits and equipment must test and (e) Before troubleshooting and testing and tests must certify by signature and examine each unit of high-voltage a low- or medium-voltage circuit date that they have been conducted. A longwall equipment and circuits to contained in a compartment with a record must be made of any unsafe determine that electrical protection, high-voltage circuit, the high-voltage condition found and any corrective equipment grounding, permissibility, circuit must be deenergized, action taken. Certifications and records cable insulation, and control devices are disconnected, grounded, locked out and must be kept for at least one year and being properly maintained to prevent must be made available for inspection tagged in accordance with paragraph (b) fire, electrical shock, ignition, or of this section. by authorized representatives of the operational hazards from existing on the Secretary and representatives of miners. (f) Prior to the installation or removal equipment. Tests must include of conveyor belt structure, high-voltage activating the ground-fault test circuit as § 75.822 Underground high-voltage cables extending from the section power required by § 75.814(c). longwall cables. center to longwall equipment and (b) Each ground-wire monitor and In addition to the high-voltage cable located in the belt entries must be: associated circuits must be examined design specifications in § 75.804 of this (1) Deenergized; or and tested at least once each 30 days to part, high-voltage cables for use on verify proper operation and that it will longwalls may be a type SHD cable with (2) Guarded in accordance with cause the corresponding circuit- a center ground-check conductor no § 75.816 of this part, at the location interrupting device to open. smaller than a No. 16 AWG stranded where the belt structure is being (c) When examinations or tests of conductor. The cables must be MSHA installed or removed; or equipment reveal a fire, electrical shock, accepted as flame-resistant under part (3) Located at least 6.5 feet above the ignition, or operational hazard, the 18 or approved under subpart K of part mine floor. equipment must be removed from 7.
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§ 75.1002–1 [Removed] equipment is located within 150 feet of (2) Interconnecting conductors and 6. Remove § 75.1002–1. pillar workings or longwall faces. cables of permissible longwall equipment; 7. Revise § 75.1002 to read as follows: (b) Electric conductors and cables installed in or inby the last open (3) Conductors and cables of § 75.1002 Installation of electric equipment crosscut or within 150 feet of pillar intrinsically safe circuits; and and conductors; permissibility. workings or longwall faces must be— (4) Cables and conductors supplying (a) Electric equipment must be (1) Shielded high-voltage cables power to low- and medium-voltage permissible and maintained in a supplying power to permissible permissible equipment. permissible condition when such longwall equipment; BILLING CODE 4510–43–P
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[FR Doc. 02–4863 Filed 3–8–02; 8:45 am] BILLING CODE 4510–43–C
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