Both API RP 580 and API RP 581 discuss risk-based inspection program in the hydrocarbon and chemical process industries. However, API-580 contains definitions and concepts. It discusses detailed description of minimum program requirements to qualify for establishing inspectionintervals based on Risk-Based Inspection (RBI) analysis. But API RP 581 presentsRBI implementing methodology. Its procedure involves a rigorous quantitative assessment of the PoF (Probability of Failure) and the CoF (Consequence of Failure) associated with each equipment item in a particular process unit. Therefore, if one looks for basic concepts of the RBI, API 580 will be good choice, but if you are looking for detailed RBI calculations and formulas, API 581 can be helpful.
What is Life Extension?
Operating aging assets beyond their designed service life could bring adverse consequences. Time-dependant damage mechanisms such as corrosionand fatigue cause additional maintenance costs and disrupt the asset availability for commissioning.The older the asset, the more problems there might be.Life extension methods helps to use facilities beyond their planned service life. Given limited inspection budgets and resources for older assets,the focus has to be not just inspection and maintenance, but targeted, prioritized and smart inspection andmaintenance. Therefore, assessment of aging assets for life extension includes risk assessment of the components and recommendations to control the risk of high-risk components.The assessment procedure should consider not only thepresent integrity of the structures and facilities but also guarantee their extended working lives. Generally, risk control measures such as inspection and monitoring are performed to keep the failure risk of the asset under predefined value. Normally as an asset ages the frequency and extent of inspections tendto increase. But risk control options can incur significant costs. Therefore, rigorous cost-benefit analysis is essential part of any life extension program.
Life extension program is even critical for offshore facilities. The ocean is one of the harshest environments on the planet. Not only is seawater and salt spray highly corrosive, wave motion and wind will also impart fatigue loading, that combines togive corrosion fatigue.
The aging asset life extension program may include following activities:
- Data gathering on current and historic condition
- Understanding of degradation processes & responses
- Use of best technology / latest assessment methods
- Development of new techniques (e.g. online monitoring)
References:
- Stacey, A., Birkinshaw, M. and Sharp, J.V., 2008, January. Life extension issues for ageing offshore installations. In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering (pp. 199-215). American Society of Mechanical Engineers Digital Collection.
- Singh, Ramesh. Pipeline Integrity: Management and Risk Evaluation. Gulf Professional Publishing, 2017.