Composite repair integrity for offshore pipeline project using Structural Reliability Assessment (SRA)

The Challenge

Composite-wrapped repairs are frequently used on offshore oil and gas pipework but are intended to be temporary. The customer had a large number of this type of repair, many on pipework that was now operating at reduced pressure, and wanted to know if the lives of these repairs could be safely extended.

The Solution

To understand the risk, Structural Reliability Assessment (SRA) was employed. 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 customer had excellent data on surface preparation, material properties, tear strength, and so on, allowing the creation of a series of probability curves distributed about the known current condition of the pipework.

The Result

Using SRA, it was possible to demonstrate to the satisfaction of both the client and the regulator that the lives of the repairs in question could be safely extended for many years. As a further check, a repair that was known to have failed was analyzed, and the mechanism was correctly predicted. The client was therefore able to divert resources to replace those repairs with shorter lives.