The Weekly Reflektion Week 31 / 2020

167 people died on the 6th July 1988 due to explosions and fires on the Piper Alpha platform in the UK sector of the North Sea. The Public Inquiry into the Piper Alpha Disaster was led by Lord Cullen and failure in the operation of the permit to work system was identified as one of the causes of the disaster. The inquiry indicated that the failure was not an isolated mistake but rather an example of laid down procedures that were not adhered to and unsafe practices had been followed for the day to day operation. Communication was highlighted as one of the areas where the permit to work system was deficient. This had previously been identified as a factor in a fatality on Piper Alpha in September 1987.

Do you realise the importance of your permit to work system? How do you ensure that the permit to work system is functioning as intended? How do you guarantee that critical information related to the work being carried out is communicated to the right people?

A condensate pump on Piper Alpha tripped and could not be restarted. The standby pump was isolated for maintenance anda permit had been issued for the work and an isolation established in accordance with the permit system. The isolation prevented the start of the pump. Without an operational pump production would need to be stopped within a short time. The operators checked that the maintenance was complete, de-isolated and started the pump. Unfortunately, a second permit had been issued to remove the pressure safety valve (PSV) on the discharge from the pump. The operators were unaware of the second permit and the removal of the PSV. The investigation found it probable that the blind flange installed on the pipework was not secured properly and condensate leaked out when the pump was started. It is estimated about 30 kgs of condensate had leaked when it ignited. The resulting explosion and fire eventually escalated to catastrophic failures of the high-pressure gas risers on Piper Alpha.

The importance of the permit system was a factor in a near miss also on another North Sea Platform. As part of a major construction project, several pipes had to be re-routed. This included a high-pressure gas pipeline that supplied fuel gas to the turbines for power generation. The intention was to maintain gas to the turbines for as long as possible hence this pipeline was among the last to be worked on.

Two mechanics started work on the pipeline using a cut and bevel tool and were partially through the steel wall when one of them asked the other whether he had the permit for carrying out the work. He did not. He had assumed that the first mechanic had collected the permit and that everything was OK to start the work. The mechanics decided to stop the work and went to find the process operator that was responsible for the area they were working in. The mechanics explained the situation to the process operator and showed him the work site where they had started to cut the fuel gas pipeline. The process operator was reported to have turned white when he saw what they had done. The fuel gas pipeline was still in operation and still filled with high pressure gas. They were millimetres away from a major gas leak that if it had ignited could have destroyed the platform they were working on. Luckily, the mechanics realised they had not followed the system for control of work, stopped the work and sought advice. Another pipeline close by had been prepared for cutting on that day and the mechanics had mistakenly started work on the wrong pipeline.

This incident and many others on several platforms in the North Sea has led to the practice of an area technician/process operator always being present at the start of any critical work including opening of hydrocarbon systems. A simple measure applied consistently that can prevent a serious incident. Do you require that a person familiar with the facilities and the systems is present at the start of critical work? Do you ensure that this requirement is actually followed?

Reflekt AS