(1) Where fire suppression devices are installed on unattended underground equipment, one or more point-type sensors or equivalent shall be installed for each 50 square feet of top surface area, or fraction thereof, of such equipment, and each sensor shall be designed to activate the first suppression system and disconnect the electrical power source to the equipment protected, and, except where sprinklers are used, there shall be in addition, a manual actuator installed to operate the system. Where sprinklers are used, provision shall be made for manual application of water to the protected equipment in lieu of a manual actuator.
(2) Two or more manual actuators, where practicable, shall be installed, as provided in paragraphs (a)(2) (i) and (ii) of this section, to activate fire suppression devices on attended equipment purchased on or after the effective date of this § 75.1107-4. At least one manual actuator shall be used on equipment purchased prior to the effective date of this § 75.1107-4.
(i) Manual actuators installed on attended equipment regularly operated by a miner, as provided in § 75.1107-1(c)(1) shall be located at different locations on the equipment, and at least one manual actuator shall be located within easy reach of the operator's normal operating position.
(ii) Manual actuators to activate fire suppression devices on attended equipment not regularly operated by a miner, as provided in § 75.1107-1(c)(2), shall be installed at different location, and at least one manual actuator shall be installed so as to be easily reached by the miner at the jobsite or by persons approaching the equipment.
(b) Sensors shall, where practicable, be installed in accordance with the recommendations set forth in National Fire Code No. 72A “Local Protective Signaling Systems” (NFPA No. 72A-1967).
(c) On unattended equipment the fire suppression device shall operate independently of the power to the main motor (or equivalent) so it will remain operative if the circuit breakers (or other protective device) actuates. On attended equipment powered through a trailing cable the fire suppression device shall operate independently of the electrical power provided by the cable.
(d) Point-type sensors (such as thermocouple, bimetallic strip, or rate of temperature rise) located in ventilated passageways shall be installed downwind from the equipment to be protected.
(e) Sensor systems shall include a device or method for determining their operative condition.
[37 FR 15301, July 29, 1972]