July, 2004

200401JulAll DayMisalignment + Corrosion = Failure!Process Safety Beacon | Expansion joints have Design Limits - Make sure they are not ExceededLessons:Asset integrityLanguage:EN Origin: CCPS Document Type:BulletinTopics:Ageing


Here’s What Happened:

This TFE lined stainless steel expansion joint was part of a piping system containing a high concentration of HCl. The expansion joint was not installed properly and HCl had embrittled the stainless steel bellows. This embrittlement along with fatigue caused by improper alignment and insufficient restraint caused the joint to fail. The catastrophic failure you see in this picture occurred the day after it passed a visual inspection. Fortunately, the system pressure was low, the leak was small, and no one was around when it failed. In this case, there were no injuries. However, if the circumstances had been only slightly different…

How Did this Happen?

• The piping to the vessel where this expansion joint was used was misaligned by approximately 3/4 inch. This caused stress on the expansion joint.
• The three retaining bolts that limit compression and extension were not installed on the expansion joint because of space limitations. This allowed excessive movement and placed even more stress on the joint.
• The specification for this joint had changed during a retrofit of the process for a new chemical service, but the expansion joint was not replaced with one of proper specification, requiring a higher grade of stainless. This likely contributed to the HCl embrittlement of the stainless steel making it prone to stress cracking and failure.

© AIChE | Sponsored by Knovel


CCPSCenter for Chemical Process Safety