Unpredicted pipeline explosion

Conclusion

This investigation concluded that inadequate maintenance was the root cause of the explosion, and that failure to properly purge the pipe for pigging was a significant contributing factor. The plug valve that had fractured did not appear to have been properly lubricated or inspected. Portions of the valve were effectively bonded to the valve seat by corrosion products, and the plug had experienced intergranular attack to the extent that portions of the plug fractured and fell from the valve. The pipeline contained a potentially explosive mixture of air and hydrocarbons when part of the plug fell to the line below, and, on impact, the spark or combustion caused by the impact initiated the first explosion in the piping system. Subsequent explosions were the result of dieseling within the pipe system.

The lessons learned from this incident are that constant vigilance is required to maintain safety in any operating system, particularly potentially hazardous installations. A continuous review of operation and maintenance is required to assure that safety needs are met. Because pipes and vessels are generally reliable, it is possible for operators to become complacent. Complacency leads to a reduction in safety standards and increases the risk of creating a hazardous situation. Routine audits of operation, safety, and maintenance procedures (preferably by an independent organization) minimize the tendency for complacency and help mitigate the risk of operations.