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May 23, 2016
What is the Effect of a Composite Repair on a Crack?

Posted by: Casey Whalen 3:00 minute read

The use of composite repairs to remediate and prevent substrate cracking is often seen as a risky repair. In fact, in the ASME B31.4 standard, composite repairs on cracks are not allowed unless the crack has been mechanically removed without penetrating more than 40 percent of the wall thickness. While this procedure is highly recommended, it is not always possible.

The challenge, then, is anticipating what effect a composite repair will have on a crack. By examining the cause and behavior of cracking in the substrate, we can begin to understand how a composite repair may increase the usable life of a pipe.

The three main categories of cracks are:

- Fatigue Crack Growth (FCG)

- Stress Corrosion Cracking (SCC)

- Mechanical Damage

FCG, which arises in high cyclic conditions where a previous defect is present, can cause severe pipeline failure and may be difficult to find with modern inspection tools. All welds are susceptible to FCG due to imperfections within the weld, including seam, girth and spiral welds. Traditional welded steel sleeves work well on girth welds, but may be less effective on any axial cracking (seam or spiral welds), where the crack may not terminate at the sleeve end.

SCC, which can also cause severe pipeline failure, can occur anywhere on a pipe with sufficient corrosive attack and tensile stress.

Finally, mechanical damage of the pipe can cause cracks as the pipe is deformed, typically due to bending by soil movement or impact damage such as dents or wrinkle bends. We will explore the cause, effect and possible repair remediation for each crack type in the following posts.

To speak with our team of engineers regarding your pipe repair project, give us a call at 855.655.6750 or fill out a contact form

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Category: Feature Articles, Pipe Wrap

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