Composite repairs – ensuring long-term integrity

Challenge

Composite wrapped repairs are frequently used on offshore oil and gas pipework, but are intended to be temporary. Our client had a large number of such repairs, many on pipework that was now operating at reduced pressure. They wanted to know whether the lives of these repairs could be safely extended.

To understand the risk we employed Structural Reliability Assessment. SRA takes a conventional design integrity analysis and applies a statistical distribution to the inputs, rather than a single fixed value. With the equation replaced by a series of related probabilities, the Monte-Carlo method can then be used to calculate the risk of failure. In this case the client had excellent data on surface preparation, material properties, tear strength and so on, allowing us to create a series of probability curves distributed about the known current condition of the pipework.

Our work

Outcome

We were able to demonstrate to both the client’s and the regulator’s satisfaction that the repairs were sounds for very many years’ time. As a further check we analysed a repair that was known to have failed, and correctly predicted the mechanism. Our client was able to divert resources to replacing those repairs with shorter lives.

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Case Study

Composite repairs – ensuring long-term integrity