Flange failure due to incorrect tool used to set flange

Contributing Factor

• Communication

Description of Incident

A mechanical connector installed as part of an 8” cooling medium line failed resulting in approx. 20m3 of cooling medium (water / glycol mix) being released to sea in 15 seconds. There were no visible warning of failure before the line failed. No personnel were injured.

Findings:

• Incorrect tool had been used to set the flange.
• Incorrect tooling alignment created stress raisers in the pipe and within the weld-neck area, outwith the supported area of the flange.
• Incorrect pressure was applied during the installation, causing partial severing of the pipe - 700 bar pressure used for the tool, correct for tool but well above the pressure for the flange type (460 bar).
• Large dilation of the flange and pipe, plasticity deformed due to over pressurisation of the joint.

Good Practice Guidance

• Ensure the correct tool is selected for the job.
• Understand the operating limits of plant and equipment and stay within them.