Self-ignition of natural gas inside pipes at a regulation station

Expert investigations were developed for a leak followed by fire in a natural gas measurement and regulation station, located in the Southern part of South America. Field inspections, chemical and microstructural tests, mechanical tests and models, and models for deflagration and detonation are presented and discussed. The fire was due to air that got into the pipes, when mounting valves at the pig traps. Venting and bleeding failed to be properly carried out while the line was pressurized, and the filling rate was not regulated properly either. In order to reduce the probability of recurrence of the event, the procedure for the filling and the pressurization of the pipeline was redesigned, safety features added, and personnel trained.