Wednesday, February 17, 2016

Risk Based Inspection for Offshore Pipeline

What is RBI?
– Any process where the decision of what inspection to perform and how often to inspect depends on risk – A structured approach to planning inspections (based on risk)– “The intention of using a risk based approach is that the activities are selected and scheduled on the basis of their ability to explicitly measure and manage threats to the pipeline system and ensure that associated risks are managed to be within acceptable limits.”

Why RBI?
– Operating pipelines presents a risk– We cannot eliminate the risk unless we remove the hazard (i.e. don’t have the pipeline)– We need to control the risk– Appropriate inspection contributes to risk control– “General industry practice is that a risk based integrity management approach should be applied.”– UK PSR• Previously a prescriptive requirement for periodic inspection• Now required to identify hazards and demonstrate that risk is controlled– all hazards relating to the pipeline with the potential to cause a major accident have been identified;– the risks arising from those hazards have been evaluated;– the safety management system is adequate; and– adequate arrangements for audit and for the making of reports thereof.

Application of RBI for pipelines
• Code guidance and methods– API 580 / 581– DNV RP F116– API 1160– ASME B31.8S

Common elements of RBI:
– Asset identification– Segmentation– Hazard identification– Probability of failure– Consequence of failure– Risk assessment– Inspection plan

But, how does inspection control risk? For time dependent hazards we can use inspection to: • Monitor deterioration• Predict future deterioration• Plan to take action before failure• But there is uncertainty• Hence we are dealing with a probability of failure rather than a fixed, known, failure date.For random hazards, an incident may result in:– Instantaneous failure– Damage which may fail with time– Initiation of a deterioration mechanism• Inspection cannot control the risk of instantaneous failure• Inspection can be used to monitor for damage, or the onset of deterioration 

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