Maintenance of petroleum process plant systems as a source of major accidents?

The prevention of hydrocarbon leaks is of great importance as they are the most critical precursor events that may lead to major accidents on petroleum facilities. Maintenance of process components on offshore and onshore petroleum facilities is therefore crucial in order to avoid major accidents, such as Piper Alpha and Texas City. Maintenance of Pressure Safety Valves (PSVs) is a significant activity because they are usually in quite high number and are recertified regularly. The accident chain that led to Piper Alpha started with maintenance of a PSV. Studies of leak circumstances have shown that, on Norwegian offshore installations, there is approximately one hydrocarbon leak per year resulting from recertification of PSVs, due to errors made during isolation and blinding or reinstatement. The preventive maintenance of PSVs thus becomes a source of a leak (which indicates risk) as well as a safety barrier element to reduce risk. The paper discusses corrective as well as preventive maintenance of static (not rotating) process equipment in relation to experience with hydrocarbon leaks and makes a case for optimization of preventive maintenance scheduling for static process equipment.