scope:

Description of Driving Event:

In Bldg. 9 at JSC, a 1000-watt quartz immersion heater was being used to heat a small amount of water for a chemical mixing operation in a precious metals shop. The heater, which was not equipped with a safety device to shut it off automatically in case of high temperature caused by the water level falling below the level of the heater element, was inadvertently left on overnight. Once water in the polypropylene bucket had evaporated, the heater's protective quartz sheath melted, and subsequently ignited the bucket, leading to a fire with damages estimated at $350,000 to a NASA facility. A simulation conducted as part of the mishap investigation confirmed the plausibility of this scenario. The mishap investigation board recommended that all equipment with the potential for overheating or causing a fire should be incapable of overheating to an ignition temperature, and there should be adequate safeguards to disconnect power in an anomalous situation.

Lesson Revised: June 17, 1997.