§ 57.4760 Shaft mines. ( a ) Shaft mines shall be provided with at least one of the following means to control the spread of fire, smoke, and toxic gases underground in the event of a fire: control doors, reversal of mechanical ventilation, or effective evacuation procedures. Under this standard, “shaft mine” means a mine in which any designated escapeway includes a mechanical hoisting device or a ladder ascent. ( 1 ) *Control doors.* If used as an alternative, control doors shall be— ( i ) Installed at or near shaft stations of intake shafts and any shaft designated as an escapeway under § 57.11053 or at other locations that provide equivalent protection;
( ii ) Constructed and maintained according to Table C-3;
( iii ) Provided with a means of remote closure at landings of timbered intake shafts unless a person specifically designated to close each door in the event of a fire can reach the door within three minutes;
( iv ) Closed or opened only according to predetermined conditions and procedures;
( v ) Constructed so that once closed they will not reopen as a result of a differential in air pressure;
( vi ) Constructed so that they can be opened from either side by one person, or be provided with a personnel door that can be opened from either side; and
( vii ) Clear of obstructions.
( 2 ) *Mechanical ventilation reversal.* If used as an alternative, reversal of mechanical ventilation shall— ( i ) Provide at all times at least the same degree of protection to persons underground as would be afforded by the installation of control doors;
( ii ) Be accomplished by a main fan. If the main fan is located underground— ( A ) The cable or conductors supplying power to the fan shall be routed through areas free of fire hazards; or
( B ) The main fan shall be equipped with a second, independent power cable or set of conductors from the surface. The power cable or conductors shall be located so that an underground fire disrupting power in one cable or set of conductors will not affect the other; or
( C ) A second fan capable of accomplishing ventilation reversal shall be available for use in the event of failure of the main fan;
( iii ) Provide rapid air reversal that allows persons underground time to exit in fresh air by the second escapeway or find a place of refuge; and
( iv ) Be done according to predetermined conditions and procedures.
( 3 ) *Evacuation.* If used as an alternative, effective evacuation shall be demonstrated by actual evacuation of all persons underground to the surface in ten minutes or less through routes that will not expose persons to heat, smoke, or toxic fumes in the event of a fire.
( b ) If the destruction of any bulkhead on an inactive level would allow fire contaminants to reach an escapeway, that bulkhead shall be constructed and maintained to provide at least the same protection as required for control doors under Table C-3.
Table C-3—Control Door Construction
Location
Minimum required construction At least 50 feet from: timbered areas, exposed combustible rock, and any other combustible material1
Control door that meets the requirements for a ventilation door in conformance with 30 CFR 57.8531. Within 50 feet but no closer than 20 feet of: timbered areas, exposed combustible rock, or other combustible material1Within 20 feet of: any timbered areas or combustible rock, provided that the timber and combustible rock within the 20 foot distance are coated with one inch of shotcrete, one-half inch of gunite, or other material with equivalent fire protection characteristics and no other combustible material1 is within that distance
Control door that serves as a barrier to the effects of fire and air leakage. The control door shall provide protection at least equivalent to a door constructed of no less than one-quarter inch of plate steel with channel or angle-iron reinforcement to minimize warpage. The framework assembly of the door and the surrounding bulkhead, if any, shall be at least equivalent to the door in fire and air-leakage resistance, and in physical strength. Within 20 feet of: timbered areas, exposed combustible rock, or other combustible material1
Control door that serves as a barrier to fire, the effects of fire, and air-leakage. The door shall provide protection at least equivalent to a door constructed of two layers of wood, each a minimum of three-quarters of an inch in thickness. The wood grain of one layer shall be perpendicular to the wood grain of the other layer. The wood construction shall be covered on all sides and edges with no less than twenty-four gauge sheet steel. The framework assembly of the door and the surrounding bulkhead, if any, shall be at least equivalent to the door in fire and air-leakage resistance, and in physical strength. Roll-down steel doors with a fire-resistance rating of 11/2 hours or greater, but without an insulation core, are acceptable if an automatic sprinkler or deluge system is installed that provides even coverage of the door on both sides. 1 In this table, “combustible material” does not refer to installed wiring or track support.
[50 FR 4082, Jan. 29, 1985; 50 FR 20100, May 14, 1985]