Chapter 20. New Guidelines on Assessing the Risk of Fatigue Failure and Remaining Life of Ageing Pressure Vessels: Available to Purchase

An assessment of the risk of failure from fatigue of ageing pressure vessels that are approaching or beyond design life is important for assuring on-going containment of hydrocarbon and other hazardous fluids and stored energy. Most operators rely on costly in-service inspections to gain the necessary assurance as many do not know how much of the design fatigue life has been used or remains. In practice, fatigue cracking is often difficult to detect because of the tightness of the cracks, and access and coverage for a good inspection can be quite limited, particularly when requiring hazardous vessel entry.

Ageing vessels on offshore installations are of particular concern because they cannot be easily inspected or economically replaced. A hydrocarbon leak from a fatigue crack in a pressure vessel could create a significant hazard. Some operators are therefore taking steps to assess the risks of fatigue failure of their vessels and taking measures to manage the risk.

The Energy Institute has recently published new Guidelines to assist operators to assess the risk of fatigue failure of their vessels. The Guidelines follow the recommendation from the UK’s Health and Safety Executive’s Key Programme 4 on ageing and life extension of offshore installations that “duty holders should consider the potential pressure and thermal fatigue risks to pressure vessels where these would be of high consequence”. The Guidelines provide a risk assessment tool to enable operators to screen and rank their vessels according to their relative risk of fatigue failure and recommend modern analysis methods and techniques by which the remaining fatigue life can be determined and improved.

This paper will describe the main features of the Guidelines and provide two case studies illustrating how two offshore operating companies have assessed the risk of fatigue failure of their ageing pressure vessels and allowed continued service.