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Heater Makes Aircraft Fire Suppression System Possible

Problem:

This customer is a government contractor who manufactures halon flame suppression systems. Flame suppression systems reduce the chance for explosions in the event projectiles puncture the wing's fuel tanks during combat. Liquid halon must be kept warm so it can readily produce vapor to replace air and suppress fire.

Solution:

Heating halon is accomplished with a FIREROD® cartridge heater submerged in the liquid halon. When needed, halon is heated to increase gas pressure and evacuate all air from the fuel tanks and replace it with halon vapor.

Certain angles at which the plane may fly produces the potential for the cartridge heater to operate out of the liquid halon. In this scenario, deadly fluorine gas could be generated. To prevent this, Watlow designed a cartridge heater with two thermostats, in series, located at each end of the unit. In the event the heater operates out of the halon, the thermostats detect increasing temperature and temporarily open the power circuit and cut heater operation. After the aircraft establishes normal flying conditions, the thermostat will close the circuit and start the FIREROD heating again.