Cause & Consequence
- Uncontrolled release of a flammable gas or liquid
Backup Contributing Factor
Complacency, Control of work, Competence
Description of Process
Plant flowrates have changed recently, and there have been high levels of vibration on the pipework on the main outlet of the condensate separator.
On at least two previous occasions the position indicator on the Level Control Valve has gone into fault, preventing the control room operator (CRO) from seeing the actual position of the level control valve. So far they have managed their way around this.
Description of Incident
What happened
- The LCV was not designed for the current flowrates, leading to vibration
- Vibration caused a crack in the 2’’ line connected to the condensate outlet,
- Condensate leaked out at ~8 kg/second. It took 90 minutes for flow to stop, as the leak was on the separator side of the closed ESDV.
Identified issues
- There was a design failure
- People had become accustomed to the vibration
- There was a lack of specialist competence to select the right size of valve
- There was a lack of operations input to projects on valve issues and design
Good Practice Guidance
Recommendations for learning:
•Vibrating pipework is a warning sign – don’t live with it
•Vibration can result from original design as well as changing plant conditions
•Creeping change can be difficult to spot – people can become accustomed to defective conditions. Are you accepting normalisation of deviation?
•Managing vibration requires engineering advice – constraining vibrating pipework can cause failure
•A Step Change Joined-up Thinking video on small bore tubing issues is available
•A guidance document for the avoidance of vibration induced fatigue failure in process pipework
Is there anything else you would do?
•Who can you go to in your organisation for help with vibration?
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