Fire protection for hydraulic excavators
Automatic fire sensing and suppression systems were designed and built for use on hydraulic shovels and backhoes. A line-type temperature sensor is mounted in the machine's engine and hydraulic pump areas to detect the heat from a fire while it is still small and easy to control. Two systems were tested. In one, the inside of the sensor consists of two conductors separated by a ceramic material whose electrical resistance decreases with increases in temperature. When heated to a predetermined temperature, the control circuit responds to the resistance drop. In the second system, the detection element of the sensor is comprised of a thin metal tube containing a hydrogen charged metal hydride wire. The tube is sealed at one end and is connected to a sensitive pressure switch at the other end. When exposed to the heat from a fire, hydrogen gas released from the metal hydride wire actuates the pressure switch. In both systems, the sensors signal compact cab-mounted control panels to: initiate visual and audible operator alarms, shut down the diesel engine, and release dry chemical extinguishing agent through a network of fixed hoses and nozzles onto the fire. In the test systems the fire alarms used were a red light and a constant tone horn. The control panels are automatically monitored continuously, to alert the operator to any malfunction in the control circuit. In the test systems, an open circuit or short circuit in the sensor triggered a yellow light and beeping. The fire suppression subsystems can be manually activated from the cab or ground level. The systems were fabricated from off-the-shelf components, and bench tested by the Bureau. In mid 1978, they were installed on a pair of Poclain HC 300 loaders. After a 1-year endurance test period, each system was functionally tested and performed satisfactorily.
- OSTI ID:
- 5494229
- Journal Information:
- Bur. Mines Technol. News; (United States), Journal Name: Bur. Mines Technol. News; (United States) Vol. 78; ISSN TNBMD
- Country of Publication:
- United States
- Language:
- English
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