Battery boxes and covers constructed of AISI 1010 hot rolled
steel shall have the following minimum thicknesses based on the total weight
of a unit of the battery assembly charged and ready for service:
+------------------------+----------------------------+
| Weight of battery unit | Minimum required thickness |
+------------------------+----------------------------+
| 1,000 lbs. maximum...| 10 gauge or 1/8" nominal |
| | |
| 1,001 to 2,000 lbs...| 7 gauge or 3/16" nominal |
| | |
| 2,001 to 4,500 lbs...| 3 gauge or 1/4" nominal |
| | |
| Over 4,500 lbs.......| 0 gauge or 5/16" nominal |
+------------------------+----------------------------+
(2) Battery boxes not constructed of AISI 1010 hot rolled
steel shall have at least the tensile strength and impact resistance of
battery boxes for the same weight class, as listed in paragraph (a)(1) of
this section.
(3) Battery box covers constructed of materials with less
than the tensile strength and impact resistance of AISI 1010 hot rolled steel
or constructed of nonmetallic materials shall meet the acceptable performance
criteria for the impact test in §7.46. Nonmetallic covers shall be used only
in the battery assembly configuration in which they pass the impact test.
(4) Nonmetallic materials for boxes and covers shall--
(a)(4)(i) Be accepted by MSHA as flame-resistant material under
part 18 of this chapter; and
(a)(4)(ii) Meet the acceptable performance criteria for the
deflection temperature test in §7.47.
(b) All insulating material shall have a minimum resistance of 100
megohms at 500 volts d.c. and be accepted by MSHA as flame resistant under
part 18 of this chapter.
(c) Battery box and cover insulating material shall meet the
acceptable performance criteria for the acid resistance test in
§7.48.
(d) Covers shall be lined with insulating material permanently
attached to the underside of the cover, unless the cover is constructed of
insulating material.
(e) Covers, including those used over connector receptacle housings,
shall be provided with a means of securing them in a closed position.
(f) Battery boxes shall be provided with vent openings to prevent the
accumulation of flammable or toxic gases or vapors within the battery
assembly. The size and location of openings shall prevent direct access to
cell terminals and other uninsulated current carrying parts. The total
minimum unobstructed cross-sectional area of the ventilation openings shall
be no less than the value determined by the following formula:
(N) (R)
------- = M
950
N = Number of cells in battery box.
R = Rated 6 hour battery capacity in ampere hours.
M = Total minimum ventilation area in square inches per battery box.
(g) Battery boxes shall have drainage holes to prevent accumulation
of water or electrolyte.
(h) Battery cells shall be insulated from the battery box walls,
partitions and bottom by insulating material, unless such part of the battery
box is constructed of insulating material. Battery box wall insulating
material shall extend to the top of the wall.
(i) Cell terminals shall be burned on, except that bolted connectors
using two or more bolts may be used on end terminals.
(j) Battery connections shall be designed so that total battery
potential is not available between adjacent cells.
(k) Cables within a battery box shall be accepted by MSHA as flame
resistant under part 18 of this chapter or approved under subpart K of this
part. The cables shall be protected against abrasion by insulation,
location, clamping, or other effective means.
(l) When the battery plug and receptacle are not located on or within
the battery box, strain on the battery terminals shall be prevented by a
strain-relief device on the cable. Insulating material shall be placed
between the strain-relief device and cable, unless the device is constructed
of insulating material.
(m) At least a 1/2-inch air space shall be provided between the
underside of the battery cover and the top of the battery, including the
terminals and connectors.
