Program Policy Manual - VOLUME V - Mine Safety and Health ...

MSHA PROGRAM POLICY MANAUL VOLUME V
"Unattended enclosed" equipment referred to in paragraph a)(3)
mounted on fire clay or a similar noncombustible mine floor
will be acceptable as "equivalent," provided the floor is free
of coal, coal dust, or other combustibles.
Small rubber-tired wheels (rim diameter 6 to 8 inches) on mobile
transformers do not constitute combustible material within the
meaning of paragraph (a)(3)(iii) and need not be removed from
unattended electrical power equipment. This interpretation
should not be construed to permit the presence or use of other
combustible materials at the device, such as a wooden platform
base, and shall be restricted to situations and equipment
involving only small rubber-tired wheels.
In some instances a determination must be made in regard to
similar noncombustible electrically-powered equipment. Careful
consideration should be given to the equipment as to its
similarity to enclosed motors, controls, transformers, and
rectifiers in regard to its being located in a fireproof area or
structure.
"Flammable fluid," as used in this section, means any liquid
having a flash point below 140 o F. This does not include
lubricating oil and grease. Electrical cables are required to
conform to Schedule 2G only if the equipment is installed in
accordance with paragraph (a)(3)(iii) which requires the cables
to meet Schedule 2G or that the cables be enclosed in metal
conduit.
The intent of this section is that timber supports or other
timber appurtenances should be considered as combustible
material. Enforcement of this regulation may cause difficulty
for some installations. Removal of or substitution of metal
supports for the timber may not always be practical. Alternative
equivalent fire protection in these instances could be provided
by using asbestos boards or metal plates, considering the merits
of each existing installation individually.
The "controls" in paragraph (a)(3) are intended to mean large
power controls on a working section or other power distribution
center. It is difficult to identify all such controls by an
ampere rating, and some judgment must be used by the inspector.
Questions may arise as to whether an "on-off" switch for an
enclosed motor should be included as a "control" and whether such
control could be mounted on a wooden post. Such practice can be
tolerated if the switch is fully enclosed in a metal box
comparable with paragraph (a)(3)(iii), which requires cables to
meet Schedule 2G or be enclosed in metal conduit.
October 2003 (Release V-34) 113