The use of risk based integrity management systems for pipelines is increasing in popularity, and now changes in legislation in the USA require operators to use risk assessment in high consequence areas. The methodologies used range from point scoring qualitative schemes to detailed quantified systems requiring structural reliability analysis, release modelling and post incident behavioural modelling. In the UK a risk based approach to pipeline integrity management has been included in legislation since 1996, and is widely used. Experience with implementing systems and applying them to onshore and offshore pipeline systems has led to the following conclusions:
• Point scoring systems cannot replace expert knowledge
• Point scoring systems always need to be modified to suit a particular system and need updating as parameters change.
• Detailed automated systems generate a huge number of sections and range of risks.This can be confusing and cannot easily be accounted for in inspection planning.
• A clear link between risks and inspection or monitoring is needed.
• Simplicity and flexibility are critical.
This paper describes a radical new approach to using risk assessment for pipeline integrity management. This new approach focuses on identifying whether hazards are time dependant (e.g. corrosion) or random (e.g. third party damage), and then either estimating a time to failure or a probability of occurrence. These estimates can be based on experience, history, or specific detailed studies. The effect of inspection and monitoring is also considered. This methodology allows the user to manage the risks associated with their pipeline in a way that is flexible, rational, consistent, and can be readily understood by others. It also allows the reasons for decisions regarding inspections to be recorded, and new users to quickly learn the key safety issues for the pipeline.