August, 2002

200201AugAll DayFaster than a speeding bulletProcess Safety Beacon | When threaded equipment is taken apart, look carefully for stripped threads, corrosion or anything that looks abnormal - it may be a WEAK POINT in your systemLessons:Asset integrityLanguage:EN Origin: CCPS Document Type:Bulletin


Here’s What Happened:

A piece of equipment was being pressure tested at approximately 5,000 psi. During the pressure check, two employees were inspecting for leaks. Without warning, a 3/4″ threaded thermowell failed at the threaded joint, the force separated it at a very high rate of speed and it struck one of the employees in the leg, leading to a very serious injury.

Common causes of failures like this:

• Threaded connections can be weak points, especially if the threads are corroded, stripped or if the threaded connection is not fully made up
• These problems are often hidden from view; finding a problem may be possible only if the connection is disassembled and all threads inspected
• In the above incident, what made the accident very serious was the fact that someone was standing right in front of the thermowell when the joint failed

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CCPSCenter for Chemical Process Safety