Release of hydrogen from a gas pipe in a refinery

During a stop of the operations for maintenance and repairs, a worker was cold-cutting a hydrogen pipe supposedly purged before. This caused a release of hydrogen. Realising this, the worker stopped the air saw and gave an alert. The installation was put in safe mode. The thousand employees presented was confined A solid plug was installed to isolate the section affected by the leak.

The incident was caused by an error in identifying the location of the purge valve to be cut. A preparatory site visit had been conducted a few months earlier between the subcontractor in charge of the work and the subcontractor responsible for its preparation. A photograph was used, in addition to isometric drawings, to locate the installations. However, the photograph used did not depict the correct purge valve but its mirror image with respect to a manifold. The label marking the location of the intervention was then placed on a hydrogen pipeline that was in operation. Pre-work checks and verifications, focused on energy isolation, failed to detect this error. There was no on-site meeting between the contractor and the operator before work began.

The ROOT CAUSE can be identified in shortcoming in the procedures regulating the preparatory work and the management between plant operator and contractors in charge of the repair/maintenance works. It was not only about procedures, but also about involvement of the site management in assuming responsibilities towards contractors and ensuring correct communications.

a pipe in a refinery

In this event, not properly designed communications and assumption of responsibility between operator and the contractor in charge of the repair works could have had great consequences. The fact that ‘nothing’ happened is related to the prompt reaction of the worker and to the fact that the hydrogen did not ignite, despite the ongoing cutting work.
To guarantee a safe environment for contractors on site, it is not only important that the latter received good quality information package on what to do, where and how. It also critical that the plant is put in a safe condition for these works, and that the plant management implement ensure proper execution of the preparatory works and optimal communication and instruction flow. The plant management remains responsible for the safety of contractors.

The authority in charge of the plant inspection, during a visit 6 days later, reminded the operator of its regulatory obligations in terms of joint operator/subcontractor inspection, the pre-interventions and safety plans aiming at incidents prevention.

Immediately after the incident, the operator reviewed its process of identification of the cutting sites. Tagging at the cutting point by the facility manager became mandatory.
Similar solution was considered for the entire refinery.