• Published: 26 Aug 2011
  • Incident ID: 3381

Thermowell Safety Alert

Cause & Consequence

  • Failure of vessels or pipework
Incident Consequence

Incident Location

Any Location Type

Incident Activity


Incident Info Source

Maersk Oil

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.

Lessons Identified

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.

Incident Recommendations

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


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