safety as defined in the American Standards Association's Wire Rope Standards and shall be replaced when it shows more than six broken wires in any single pitch length or lay of rope.

(8) The rope shall have at least three full turns on the drum when extended to its maximum working length and shall make at least one full turn on the drum shaft or around the spoke of the drum (in case of a free drum) and be fastened securely by means of clamps.

(9) A hoisting rope shall be fastened to its load by a spelter-filled socket or by a thimble and clamps.

(b) Cages and shafts. (1) Cages used for hoisting men shall be of substantial construction; with adequate steel bonnets; with enclosed sides; with gates, safety chains, or bars across the ends of the cage when men are being hoisted or lowered; and with sufficient handholds or chains for all men on the cage to maintain their balance.

(2) The floor of the cage shall be constructed so that it will be adequate to carry the load and so that it will be impossible for a workman's foot or body to enter any opening in the bottom of the cage.

(3) Cages used for handling men shall be equipped with safety catches that act quickly and effectively in an emergency.

(4) Cages shall be inspected daily. A test of safety catches on cages shall be made at least every two months. A written record shall be kept of inspections and tests, which shall be open for inspection by interested persons.

(5) The speed of the cage when hoisting or lowering men, unless regulated by State laws, shall not exceed 900 feet a minute.

(6) There shall be at least two independent methods of signalling, one of which shall be audible to the engineer, from all landings in shafts and slopes.

(7) An approved signal code shall be in use at each mine and shall be posted prominently in the engine room in easy sight of the engineer and at all places where signals are given.

(8) Workmen shall wear safety belts while doing repair work in or over shafts.

(9) An attendant shall be on duty at all cage stations when men are being hoisted or lowered at the beginning and end of each operating shift and when men are working in the shaft.

(10) Shafts shall be equipped with self-closing or manually controlled safety gates at surface landings.

(11) Positive stop blocks or derails shall be placed near shaft surface landings.

(12) At the bottom of each hoisting shaft and at intermediate landings, a "run-around" shall be provided for safe passage from one side of the shaft to the other. This passageway shall be not less than 5 feet in height and 3 feet in width.

(c) Haulage roads. (1) The roadbed, rails, joints, switches, frogs, and other elements of the track of all haulage roads shall be constructed, installed, and maintained in a manner consistent with speed and type of haulage operations being conducted to insure safe operation.

(2) Track switches, except room and entry development switches, shall be provided with properly installed throws, bridle bars, and guardrails; switch throws and stands, where possible, shall be placed on the clearance side.

(d) Clearance and shelter holes. (1) Haulage roads on entries developed after the effective date of this code shall have a continuous unobstructed clearance of at least 24 inches from the farthest projection of moving equipment.

(2) On haulage roads where trolley lines are used, the clearance shall be on the side opposite the trolley lines.

(3) On the trolley-wire or "tight" side, there shall be sufficient clearance to prevent the farthest projection of moving equipment from rubbing or coming in contact with ribs or timber.

(4) After the effective date of this code, all new sidetracks, partings, or entries equipped with more than one track shall have a clearance of at least 24 inches between the outermost projection of moving traffic.

(5) The clearance space on all haulage roads on entries driven before or after the effective date of this code shall be kept free of loose rock, coal, supplies, or other materials: Provided, That not more than 24 inches need be kept free of obstructions.

(6) Ample clearance shall be provided at all points where supplies are loaded or unloaded along haulage roads or conveyors.

(7) Where it is necessary for men to cross conveyors regularly and where the width of conveyors or low roof intro

(8) Shelter holes shall be provided along haulage entries driven after the effective date of this code where locomotive, rope, animal, or shuttle-car haulage is used. Such shelter holes shall be spaced not more than 80 feet apart. Except where the trolly wire is 6 feet or more above the roadbed or guarded effectively at the shelter holes, they shall be on the side of the entry opposite the trolley wire.

(9) Shelter holes made after the effective date of this code shall be at least 5 feet in depth, not more than 4 feet in width, and 6 feet in height or as high as the traveling space, if the traveling space is less than 6 feet high. Room necks and cross cuts may be used as shelter holes even though their width exceeds 4 feet.

(10) Shelter holes shall be kept clear of refuse and other obstructions.

(11) Shelter holes shall be provided at switch throws, except where more than 6 feet of clearance is maintained and at room switches.

(12) At each landing of a slope where men are passing and cars are handled, a shelter hole at least 10 feet deep, 4 feet wide, and 6 feet high shall be provided.

(e) Haulage equipment. (1) Nonpermissible internal-combustion engines or other machinery which gives off noxious fumes shall not be permitted underground in any coal mine.

(f) Safety devices and practices. (1) Locomotives shall be equipped with proper devices for the rerailing of locomotives and cars.

(2) An audible warning device and headlights shall be provided on each locomotive.

(3) Where hoists are used for handling men in underground slopes, in pitching beds, or on slopes between two or more beds, the provisions governing hoisting or haulage mentioned heretofore shall apply.

(4) A permissibl trip light shall be used on the rear of trips pulled, and on the front of trips lowered into slopes or pushed. Trip lights need not be used during gathering operations at working faces. The uses of efficient reflectors in lieu of trip lights may be discontinued where now in use pending an investiga

tion by the United States Bureau of Mines to determine the effectiveness of such reflectors. (See § 304.5 (j) (1).

(5) Pushing of cars on main haulage roads shall be prohibited, except where necessary to push cars from side tracks to producing entries, where necessary to clear switches and side tracks, and on the approach to cages.

(6) Back-poling shall be prohibited except at places where the trolley pole cannot be reversed or when going up extremely steep grades and then only at very slow speed.

(7) Other than the motorman and trip rider, no person shall ride on a locomotive unless authorized by the mine foreman, and no person shall ride on loaded cars or between cars of any trip, except that the trip rider may ride on the last car.

(8) Motormen and brakemen shall not get on or off cars, trips, or locomotives while in motion, except that a brakeman may get on or off the rear end of a slowly moving trip to throw a switch or to close a door.

(9) All trips and all traffic equipment shall come to a complete stop before couplings are made by hand, unless a coupling hook is used.

(10) Standing cars on any track, unless held effectively by brakes, shall be properly blocked or spragged. Cars shall be secured effectively at working faces.

(11) On slopes and planes having a knuckle, there shall be a positive-acting stopblock, at or above the knuckle, and a derail.

(12) On entries going to the rise, a positive stopblock or derail shall be placed outby the switch of the first active working place.

(13) On entries going to the dip, a positive-acting stopblock or derail shall be placed just outby the switch to the first active working place, and a stopblock shall be placed just inby the switch of the last active working place.

(14) When coal is not being loaded, but men are working at a room or entry face, a positive-acting stopblock or derail shall be placed across the room or entry track, or the room switch shall be kept closed to prevent cars from being inadvertently pushed or running into the places.

(15) Slides, skids, or other adequate means shall be used on descending trips on grades where the locomotive is not adequate to control the trip, and where practicable, a drag shall be used on ascending trips.

(16) Material being hauled inside the mine shall be so loaded and protected that there is no danger to the motorman or brakeman from sliding of equipment and material.

(g) Transportation of men. (1) Mantrips shall be operated at safe speeds consistent with the condition of roads and type of equipment used, but not to exceed 12 miles an hour.

(2) Each man-trip shall be under the charge of a responsible person and it shall be operated independently of any loaded trip of coal or other material.

(3) Cars on the man-trip shall not be overloaded and sufficient cars in good mechanical condition shall be provided.

(4) No person shall ride under the trolley wire unless suitable covered mancars are used.

(5) No material or tools shall be transported in the same car with men on any man-trip, and all persons shall ride inside of man-trip cars, except the motorman and brakeman or trip rider.

(6) Men shall not load or unload before the cars in which they are to ride or are riding come to a full stop, and men shall proceed in an orderly manner to and from man-trips.

(7) A waiting station shall be provided where men are required to wait for man-trips or man-cages. It shall have sufficient room, ample clearance from moving equipment, and adequate seating facilities.

(8) Trolley and power wires shall be guarded effectively at man-trip stations where there is a possibility of any person coming in contact with energized electric wiring while loading or unloading from the man-trip.

(3) Where belts are used for transporting men, a minimum clearance of 18 inches shall be maintained between the belt and the roof or cross bars, projecting equipment, cap pieces, overhead cables, wiring, and other objects; but where the height of the coal bed permits, the clearance shall not be less than 24 inches.

(10) The belt speed shall not exceed 250 feet a minute while men are loading, unloading, or being transported.

(11) The space between men riding on a belt line shall be not less than 5 feet.

(12) Loading and unloading stations shall be illuminated properly.

(13) An official or some other person designated by the mine foreman shall supervise the loading and unloading of belts and man-trips.

§ 304.8 Electricity—(a) Surface transmission lines. (1) Overhead high-potential power lines shall be placed at least 15 feet above the ground and 20 feet above driveways and haulageways, shall be installed on insulators, and shall be supported and guarded to prevent contact with other circuits.

(2) Overhead power circuits shall be protected against lightning and voltage surges, and high-potential power lines shall be protected adequately by circuit breakers, fuses, or both.

(3) Electric wiring in surface buildings shall be installed so as to present minimum fire and contact hazards.

(b) Transformer stations. (1) Unless surface transformers are isolated by elevation (8 feet or more above the ground), they shall be enclosed in a transformer house or surrounded by a suitable fence at least 6 feet high. If the enclosure is of metal, it shall be grounded effectively. The gate or door to the enclosure shall be kept locked at all times, unless authorized persons are present.

(2) Surface transformers containing flammable oil and installed where they present a fire hazard (near mine openings or in or near combustible buildings) shall be provided with means to drain or to confine the oil in event of rupture of the transformer casing.

(3) Transformers ordered after the effective date of this code, both permanent and portable, for use underground shall be air-cooled or nonflammable-liquid cooled.

(4) Permanent underground stations containing transformers filled with flammable oil shall be provided with door sills, or their equivalent, that will confine the oil if leakage or explosion occurs.

(5) Portable underground substations for transformers or other power conversion equipment shall be in fireproof housings. Where the installation contains transformers filled with flammable oil, means shall be provided to confine the oil in event of leakage or explosion.

(6) "Danger-high voltage" signs shall be posted conspicuously on all transformer enclosures, high-potential switchboards, and other high-potential installations.

(c) Substations and switchboards. (1) Permanent underground substations shall be in rooms of fireproof construction. Surface and underground substations shall be kept free from refuse, and metal containers shall be provided for oily waste.

(2) Switchboards installed after the effective date of this code shall be located so that ample room will be provided between the switchboard and passageways or lanes of travel and shall have an entrance at each end to permit authorized persons to inspect, adjust, or repair apparatus back of the board. Switchboards shall have the entrance to the rear guarded against entrance of unauthorized persons, unless in a building that is kept locked.

(3) Switchboards shall be well lighted for switch operations in the front and for repair and maintenance in the rear. (4) Rooms housing switchboards shall be free of debris and refuse.

(5) Pull switches and circuit breakers, or other power controls shall be mounted on slate or other suitable insulating material.

(d) Power circuits. (1) High-potential power cables (600 volts or more) carried from the surface through shafts, boreholes, and underground passageways shall be adequate for the services intended, installed in a permanent manner, and guarded from mechanical injury.

(2) Power wires, whether bare or insulated, except ground wires, shall be supported on or by well-installed insulators and shall not touch combustible materials, roof, or ribs.

(3) Power wires shall be insulated properly where passing through doors and stoppings, and where they cross other power circuits.

(4) Electric cables and wires, other than signal wires and trolley wires used for haulage, installed in haulage slopes shall be buried not less than 12 inches below combustible material or installed in fireproof protective conduit.

(5) Where track is used as a power conductor:

(i) Both rails of main-line tracks shall be well bonded and cross-bonded at least every 200 feet; however, if the track circuit is paralleled with a feeder cable, both rails of the track shall be well bonded and cross bonds shall be installed at least every 1,000 feet in both the track and feeder circuit.

(ii) At least one rail on secondary haulage roads shall be well bonded, and cross bonds shall be installed at least every 200 feet.

(iii) Switches on entries shall be well bonded.

(6) Power shall be disconnected before repair work is to be done on energized electric circuit or energized parts of electric equipment. Employees required to make repairs on energized bare trolley lines should wear protective clothing, such as insulated shoes and lineman's gloves, or the power shall be disconnected.

(7) Trolley and feeder wires shall be installed as follows:

(i) On the opposite side of the entry from shelter holes and clearance space, except where 6 feet or more above the roadbed or adequately guarded at shelter holes.

(ii) The hangers on curves shall be spaced so that the trolley wire may become detached at any one hanger without exposing the locomotive operator to a shock hazard.

(iii) Alined properly and installed at least 6 inches outside the track gage line. (iv) Provided with cut-out switches at intervals of not more than 2,000 feet and near the beginning of all branch lines.

(v) Kept taut and not permitted to touch the roof, rib, or cross bars; particular care shall be taken where they pass through door openings to preclude the possibility of bare wires coming in contact with combustible material.

(vi) Guarded adequately where it is necessary for men to pass or work under them regularly, unless the wires are more than 61⁄2 feet above the top of the rail. They shall also be guarded adequately on both sides of doors.

(vii) Shall not extend beyond the last open crosscut and shall be kept at least 150 feet from pillar workings.

(viii) Anchored securely and insulated properly at the ends.

(ix) Not in air known to contain 1.0 percent or more methane or in air re

turning from pillar recovery work or old workings where dangerous amounts of methane may be liberated suddenly, Provided, That, when this requirement is not being complied with, reasonable time may be allowed to make necessary changes.

(e) Grounding.

(1) Metal conduit and metallic coverings and armor of cables shall be grounded and shall be electrically continuous to afford a conductor path for the ground circuit.

(2) Metallic frames, casings, and other electrical equipment that can become "alive" through failure of insulation or by contact with energized parts shall be grounded.

(3) Casings of transformers shall be grounded unless protected by isolation (freedom from contact hazard by position).

(4) Mining equipment mounted on rubber tires or caterpillar treads, receiving power through a trailing cable, purchased after the effective date of this code, shall be grounded effectively.

(f) Circuit breakers and switches. (1) Fuses or equivalent protective devices of the correct type and capacity shall be installed on electric equipment to protect against excessive overload. Wires or other conducting materials shall not be used as a substitute for properly designed fuses, and where circuit breakers are used, they shall be maintained in good operating condition and adjusted so that equipment cannot be overloaded.

(2) Switches and circuit breakers shall be installed so that they are readily accessible and can be operated without danger of contact with moving or live parts.

(3) Disconnecting switches shall be installed in all main power circuits at the bottoms of shafts, boreholes, and at other places where main power circuits enter the mine.

(4) Underground electric equipment and circuits shall be provided with switches or other controls of safe design, construction, and installation.

(5) Circuit breakers or other overload devices shall be provided to protect power circuits. If they are automatic, they shall be set so that the circuits cannot be overloaded.

(6) Dry wooden platforms, rubber mats, or other electrically nonconductive material shall be kept in place at each

switchboard, power-control switch, and at stationary machinery where shock hazards exist.

(g) Telephone systems. (1) Telephone service shall be provided at the bottom of each main shaft or slope and in all mines from the surface to the working sections of the mine, where the mine workings are 1,500 feet or more from the surface.

(2) Telephone lines, other than cables, shall be carried on insulators, installed on the opposite side from power or trolley wires, and where they cross power or trolley wires, they shall be insulated adequately.

(3) Telephone circuits on the surface shall be protected by lightning arresters.

(h) Signal systems. (1) Signal wires shall be supported on insulators and insulated properly where they cross power lines.

(2) Rare signal wires that are readily accessible to persona' contact shall not carry more than 30 volts. (This does not apply to block-signal systems.)

(i) Electric face equipment. (1) After the effective date of this part, all new electric face equipment and "eplacements of equipment purchased for mines where nonpermissible equipment is now being used shall be of a permissible type approved by the United States Bureau of Mines, except that explosion-tested cable-reel locomotives and shuttle cars may be used. This does not apply to equipment ordered before the effective date of this part. (§ 304.5 (j) (1).

(2) Permissible junction or distribution boxes shall be used for making multiple-power connections in working places or other places where dangerous quantities of methane may be present or may enter the air current, except that where nonpermissible junction or distribution boxes are now in use, or on order, their use may be continued until such time as replacements are made.

(3) Permissible equipment shall be maintained in a good state of repair and in permissible condition. (See § 304.5 (j) (1).)

(4) In mines where nonpermissible equipment is now being used, care shall be taken to protect the workmen by making frequent examinations of the air for methane content and by preventing interruption of the ventilating current. (See § 304.5 (j) (1)).