Diesel explosion of propane at pump-down of air conditioner.

Propane (R290) is a potential alternative refrigerant for reducing greenhouse gas emissions from refrigeration and air conditioning equipment; it is necessary to carry out an adequate safety assessment because of its high flammability. This study focuses on compressor explosion accidents at pump-down of split air conditioners. Pump-down is an operation used to gather an entire refrigerant into an outdoor unit by closing the outlet valve of the outdoor unit and forcefully driving the compressor. If the entrance of air into the tube for the refrigerant occurs owing to an error during operation, the lubricating oil in the compressor may cause a self-ignition and a diesel explosion. Experiments were conducted to reproduce the diesel explosion, and its characteristics were examined. A mixture of air, a refrigerant, and lubricating oil was compressed by a compressor and an explosion occurs under certain conditions. R290 was used as the refrigerant, and its safety was evaluated in comparison with conventional fluorocarbon refrigerants.