A burning propane leak occurred at 6:40 a.m. at a refinery. A flame was shooting 2 m into the air from the flange of a pipe connected to propane accumulators. The refinery’s internal emergency plan was implemented at 6:50 a.m. Its employees were evacuated. The line’s automatic valves closed. Technicians began isolating the equipment and relieving pressure in the line. Emergency services set up a 200 m cordon. They decided not to douse the flame and instead allow the propane to burn off. They protected the area with water curtain systems. At 1:40 p.m., the flame was reduced to 1 m in height. It burnt itself out at 3:11 a.m. The site’s firefighters injected steam into the line. The internal emergency plan was lifted at 2:55 p.m.

An estimated 16 t of gas was burnt. The operator replaced the gasket on the leaking flange and a section of pipe. The repairs cost less than €100,000. Production losses were estimated at €1.5 million.

The leak occurred after three days of the unit not operating stably. A malfunction in the measurement of the interface of one of the two extractors caused the propane to become polluted with a mixture of heavy hydrocarbons. The operator thinks that the difference in density may have caused the allowable stress of the line’s flanges to be exceeded. In addition, a slight depression was found on the gasket of the leaking flange. The gasket, which is corrugated and made of stainless steel with a graphite layer, may have been improperly fitted.

The operator modified the control PLC to make it easier to have a real-time assessment of the material between the two extractors. The purpose is to understand what causes the unit to not operate stably. From now on, a propane sample will be collected and its colour visually checked each day.