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DATE: December 29, 1997

INCIDENT TYPE: Propane Explosion

LOCATION: District 4

TYPE OF WORK ACTIVITY: Lighting Thermoplastic Pre-Heater

THE ACCIDENT: At approximately 5:30 AM on December 19, 1997, a Caltrans Equipment Operator was lighting a thermoplastic pre-heater in preparation for the day’s work. The CEO lit the pilot light on the pre-heater and was turning the valve to increase the temperature when the pilot light went out. The CEO noticed that the main LPG (Liquid Propane Gas) tank was off. The CEO turned the temperature control valve off and opened the valve on the main LPG tank. When the employee attempted to re-light the pilot light, an explosion occurred. The CEO was immediately taken to the hospital and released later that day with second and third degree burns to the face.

CONCLUSIONS: The employee did not follow the manufacturer’s instructions, which stated that the unit should be allowed to cool for several minutes before opening the main LPG tank valve. (This allows the thermocouple to cool and shut off, preventing LPG from flowing into the combustion chamber.) Also, because of the unreliability of the installed igniter system, the supervisor had approved a manual lighting procedure that was being used when the accident occurred. The manual lighting procedure required the operator to place an arm into the combustion chamber and manipulate an electronic igniter while depressing the pilot light button. This places the operator’s face in close proximity to the pilot light viewing port.

RECOMMENDATIONS: Light thermoplastic pre-heater pilot lights only with the installed igniter system. This will allow the operator to remain clear of the burner during the lighting process. If difficulty is experienced with the installed igniter system, notify the District equipment shop so repairs can be completed.

The potential for this type of accident exists with any Propane or LPG fueled device. Exercise extreme caution and closely follow the manufacturer’s directions for lighting burners or pilot lights.


Released 1/9/98 

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