Challenges in Inspection Planning for Maintenance of Static Mechanical Equipment on Ageing Oil and Gas Production Plants: The State of the Art

Although the design life of many of the oil and gas (O&G) production and process facilities on the Norwegian Continental Shelf (NCS) has been exceeded, the same physical assets are still under exploitation as a result of extended life based on the information gathered by inspection, maintenance, modification and replacement history. Nevertheless, pressure systems, which comprised of static mechanical equipment such as piping components (valves, separators, tanks, vessels, spools, etc.), undergo continuous inherent deterioration (fatigue, corrosion, erosion, etc). Often the deterioration rates vary over the lifetime following no specific pattern due to the changes in product quality of the well stream, varying environmental conditions and unexpected cyclical loading. These necessitate effective inspection planning to repair, modify or replace those components that reach the end of their design life. This enables the integrity of the physical assets to be retained at a tolerable level. The inspection planning has traditionally been driven by prescriptive industry practices and carried out by human experts, based on risk-based inspection (RBI) and risk-based maintenance (RBM) philosophies. The RBI and RBM involve the planning of inspections on the basis of the information obtained from risk analyses of a particular system and related equipment. This manuscript reviews the evolution of inspection and maintenance practices. Then it provides a conceptual framework to mechanize the inspection planning process in order to reduce the effect arising from human involvement, whilst improving the effective utilization of data from different sources.