Gas Leak from vent line within turbine enclosure

Cause & Consequence

• Uncontrolled release of a flammable gas or liquid

Contributing Factor

• Communication
• Control of work

Description of Process

The fuel gas priming process releases short bursts of fuel gas through the vent line. The vent line is only used for priming the fuel gas before changing over and for purging the system. Short duration low frequency use, the priming process is required to condition the gas to specified temperature and remove condensate before introducing it to the turbine.

When transferring over from diesel to fuel gas, the venting process requires small amounts of hydrocarbon fuel gas to be released to atmosphere using an agreed control valve operating method. A valve is opened/closed in quick succession to vent the fuel gas in short bursts.

Description of Incident

During the above process, the gas detector within the turbine enclosure activated.

The GPA was activated when the gas detector went into High/High alarm and subsequently shut down the turbine.

Snoop tests confirmed that the release had come from a join between the flexible/hard pipe section within the enclosure.

A weep had been identified on the flexible line by the previous crew involved in the initial isolation using nitrogen. A work order was raised but the vent line was not tagged (Defect Tag).

Good Practice Guidance

Maintenance – When working with flexible/hard sections of hose be mindful of impact on integrity when bending

Defect Tagging – Ensure a process/procedure to tag defects when identified is available and that it is used.

Control of Work - Ensure equipment being returned to service is indeed fit to be returned to service.