(112c) For Want of a Nail, the Kingdom Was Lost: Process Safety Management of Gaskets and Flanged Connections

Flanged connections have an important role in all process systems. They modularize the system and allow it to be efficiently assembled and disassembled for installation, repair, or replacement. In the flanged connection assembly, gaskets are a critical component, along with bolts and the flange body. The gasket can maintain the pressure integrity of a flanged connection over its design life if it is properly selected, installed, and inspected. Industry data shows that flange connections are the most likely location for leaks to occur in a process plant, and often the gaskets get blamed for leakage. 

The most notable incident of gasket failure leading to a tragedy was the Challenger disaster. On January 28, 1986, seven astronauts were killed when Space Shuttle Challenger exploded just over a minute into the flight. The failure investigation concluded that the explosion was caused by a failure of the solid rocket booster O-rings to seal properly.

The process safety literature also offers similar anecdotes where a lack of flange integrity caused a major, high consequence release of process fluids. In 2005, a damaged gasket on the inlet to an exchanger at a nuclear power plant led to a leak of non-radioactive cooling water that prompted the shutdown of the plant. And in 2012, a metal gasket failure on a hydrofluoric (HF) alkylation unit piping flange resulted in a release of an estimated 300-500lb HF acid.

However, gaskets often recieve an unjust share of the blame for integrity issues. In reality, each flanged connection component is responsible for cooperatively preventing connection leakage. Therefore, a holistic mindset is required to understand and prevent unacceptable leakage at flanged connections.

This paper will discuss the role of flanged connections in ensuring process safety throughout the life cycle of a plant. Problems specific to the flanged connection will be discussed in the five phases of a plant life cycle: Research; Process Development; Detailed Engineering and Construction; Operations, Maintenance, and Repair; and Decommissioning.