A hydrocarbon leak occurred in a processing module and gas detectors went into alarm.
An operator was sent to the module to investigate. He quickly became aware of the smell of gas and notified the CRO.
The duty CRO immediately shutdown the plant.
The plant was made safe. An oil leak was traced to a ¼” diameter hole at the lower end of a pipework elbow. The line was rarely used and had been left stagnant with liquid creating a deadleg corrosion trap.
Deadlegs can result in rapid corrosion and can arise as a result of:
- design errors
- the effects of normal operations
- a change in designed operating mode
- plant changes
Be aware of the potential for operational deadlegs.
Operations and maintenance
- Be aware of changes to process plant operation
- Identify periods of significant stagnant operation in process lines with potentially corrosive fluids
- Ensure integrity personnel are consulted on Operational Risk Assessments (ORA) and Management of Change affecting the way pressure systems equipment is operated
- Ensure risk-based inspection and integrity assessments account for threats of operational deadlegs and critical inspections are performed
- Consider review of material selection for known problem areas
- Ensure corrosion risk assessments and chemical management strategy are reviewed periodically
Help and Advice:
- Energy Institute ‘Guidance for corrosion management in oil and gas production and processing’ provides good insight into the hazards of deadlegs, how they can be avoided and managed
- Step Change in Safety – Asset Integrity Toolkit
- Step Change in Safety – Guidance on Hydrocarbon Release Reduction Plans
- Step Change in Safety – Joined-up Thinking Communication pack
- Energy Institute – Corrosion Threats Handbook