Cause & Consequence
- Failure of vessels or pipework
Any Location Type
Incident Info Source
Specific Incident Equipment
Failure of integrity of thermowell allowing minor gas release.
Supplier details: Carrs Special Steels, UK. Cast no. CD16249, manufacture date: 22/6/2006. Material spec is: ASTM A182 F 316L.
Defect was not identified during visual inspections Thermowell passed pressure and service tests
Small cracks developed from the shrinkage cavities to the metal surface as a result of vibration.
More reliable NDE techniques are required to identify sub-surface material defects.
Operator vigilance is very important and prevented this becoming a significant gas release.
1. Operators may wish to check the certification on thermowells they may
have purchased to establish if any of them come from this same batch
number. If any do, they may wish to plan to change them out.
2. The manufacturer did carry out all the tests identified on the order, but
none of these would have found this defect type. Therefore, Operators
may wish to consider specifying additional inspections at the supply stage
for thermowells on high pressure hydrocarbon service to check for subsurface