Near-miss: Gas release from subsea pipeline

A member has reported a near miss incident in which there was an unplanned release of gas from a subsea pipeline, when divers were working nearby. A vessel was engaged in connecting a 32″ (81cm) spool to the pipeline with the vessel crane connected to the spool. Divers were in the bell for changeover of shift. Suddenly there was a release of gas near to the vessel. The Master took immediate action and moved the vessel 150m out of the area; the clearing crane wire was slacked off, and at a safe distance when no bubbles were observed in the water, the ROV was launched. The ROV went to the crane hook location, and the crane hook was released safely. ROV and crane wire was recovered without any damage to any property. The divers were unharmed.

Initial investigation records the following:

• An energy isolation permit was in place which was issued by the refinery and platform;
• The refinery failed to inform the vessel about the valve opening and expected gas flow down the pipeline.

Our member noted the following:

• There should be proper communication established between the refinery and the vessel before opening any valves and permitting gas flow down the pipeline;
• The vessel should be ready always to face any H₂S emergency at site;
• Drills for H₂S emergency, general muster, abandon ship and LARS bell recovery should be carried out regularly;
• H₂S detectors and appropriate PPE should be tested periodically.

IMCA notes that the importance of a properly understood and properly communicated Permit to Work process cannot be over-emphasised, particularly in high potential incidents such as this, and where communication between remote sites may be at a premium.

Members may wish to refer to the following incident:

• Gas release from pipeline during diving operations