Severity
Incident
Leak
Yes
Ignition
Yes

Overview
A hydrogen leak and fire occurred due to the installation of an incorrectly sized gasket at a solvent manufacturing plant. A worn gasket was accidentally replaced with a new gasket that was smaller than the standard one, and the system could not withstand the operational pressure of the hydrogen, causing the hydrogen to leak and ignite a small fire. Furthermore, a nearby gasket was damaged by the fire, causing a larger quantity of hydrogen to leak, and the fire spread. As nitrogen was substituted for the combustible hydrogen gas in the piping at an early stage of the fire, damage was limited to the immediate area. If the hydrogen had not been quickly purged from the system, the fire damage would have been greater. It is assumed that gasket management at a turnaround shutdown was the cause.

Incident Synopsis
A worn gasket was replaced with a somewhat smaller one, and was used to rejoin the flange of a valve at a solvent manufacturing plant. The system was then activated and the system pressure gradually rose, until the plant shifted into usual continuous operation. After operation restarted, the smaller gasket, which was about 1/7th the width of the standard one, could not withstand the pressure of the compressed hydrogen. Hydrogen began to leak from the flange and was ignited by static electricity, causing a small fire in the thermal insulation. A flange of an adjacent drain valve, and the thermal insulation on the valve, were also damaged. A large quantity of hydrogen leaked from the flange of the drain valve, and the fire spread. The plant was urgently shut down and employees carried out initial fire fighting and nitrogen substitution. The fire department was notified about the fire, and the fire fighters injected nitrogen into the system until the fire burned itself out and was confirmed to be extinguished.

The cause of the incident was human error in removing a worn component and installing the wrong replacement part. After a gasket replacement, a leak test is usually performed. The new gasket passed the leak test at the time of this incident, probably because the test duration was very short.

The physical damage incurred during the incident was concentrated on nearby piping and surrounding thermal insulation.

Incident Date
Apr 28, 1996
Setting
Equipment
  • Piping/Fittings/Valves
  • Gasket
Damage and Injuries
When Incident Discovered
Lessons Learned

Normally hydrogen fires are not extinguished until the supply of hydrogen has been shut off due to the danger of re-ignition and explosion. During a gas leak/fire, it is important to shut off the source of the hydrogen if it is safe to do so. If the leak cannot be stopped, the danger of a fire (or an explosion if the unburned hydrogen gas is leaking into a poorly ventilated confined space) would be very high. If a leak cannot be stopped, fire extinguishing is impossible and only prevention of fire spreading is possible. It is also difficult to detect a gas leak from thermally insulated piping at an early stage.

Countermeasures which were employed to prevent future occurrences include:

Improving management of construction at turnaround to prevent improper gasket installations.
To detect gas leaks in piping systems covered with thermal insulation, inspection windows were installed in the insulation and gas leak checks were strengthened.