30 CFR § 75.1107-10 High expansion foam devices; minimum capacity.
(a) On unattended underground equipment the amount of water delivered
as high expansion foam for a period of approximately 20 minutes shall be not
less than 0.06 gallon per minute per square foot of surface area of the
equipment protected; however, the minimum total rate for any system shall be
not less than 3 gallons per minute.
(b) On attended underground equipment, foam may be delivered by
internal injection, inundation, or combination-type systems. Each system
shall deliver water as foam for a minimum of 10 minutes. For internal
injection, the rate of water application as high expansion foam shall be not
less than 0.5 gallon per minute per hazardous location; however, the minimum
total rate shall be not less than 2 gallons per minute. For inundation, the
rate of water application as high expansion foam shall be not less than 0.05
gallon per minute per square foot of top surface area of the equipment
protected; however, the minimum total rate shall be not less than 5 gallons
of water per minute.
(c) In combined internal injection and inundation systems the rate of
water applied as foam shall not be less than 0.035 gallon per minute per
square foot of top surface area of the equipment protected; however, the
minimum total rate shall not be less than 3.5 gallons of water per
minute.
(d) Where internal injection is employed, the amount of water
discharged as high expansion foam into the cable reel compartments of
underground equipment regularly operated by a miner shall be approximately 25
percent of the total amount required to be discharged by the system;
however, the quantity of water discharged as foam into the cable reel
compartment need not exceed 1.5 gallons.
