Trenchless Tricks: Pipeline Repair Troubleshooting

Successful projects don’t lose money. Here’s how to overcome a few trenchless trip-ups.
Trenchless Tricks: Pipeline Repair Troubleshooting
One of the most important and often overlooked job factors for a successful rehabilitation project is the client. It is important to discuss current pipe conditions and what the lining will look like when completed to ensure the customer’s expectations are met.

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Trenchless rehabilitation techniques have become a generally accepted solution for most mainline sewer and storm system pipeline repairs, which means it’s even more important to understand what problems are likely to occur and how to quickly solve them.   

Regardless of the pipe diameter you’re working on, certain challenges can be the difference between a successful project and one that loses money. The following are a few recent pitfalls that could have been avoided by the lining contractor.

Who is paying the bills?

One of the most important and often overlooked job factors for a successful rehabilitation project is the client. It is important to discuss current pipe conditions and what the lining will look like when completed to ensure the customer’s expectations are met. 

You can create service brochures that illustrate how a pipe in poor condition is transformed into a perfectly smooth lined pipe. This is not always the case with cured-in-place (CIPP) pipe liners. The liner conforms to the deformation in odd-shaped sections, holes or other deformations. 

If there are bends in the pipe there may be fins or wrinkles in the lining. The lining is still structurally sound and the lined pipe will function as designed, but if the client has the expectation of a visually smooth lining, he or she may insist on expensive and unneeded remediation of the perceived defects in the lining. So, it’s vital to ensure the customer understand these factors. 

Shy away from shrinkage

It is important to relieve tension on a CIPP bag before curing during installation to avoid liner shrinkage. This may not be possible when you’re working on steep slopes, and the liner may shrink. Again, this is another reason why it’s important to educate clients so that they understand the liner will still be functional and doesn’t need to be removed and replaced. If the lateral cuts have moved, you can remediate them by recutting and using a top hat to bridge the original cut, and then use a sectional liner to fill the pullback area if needed. 

An incomplete cure will leave soft areas in a CIPP liner that may collapse, bubble or otherwise fail. This may be due to improperly proportioned resin mix (in which case, the lining should be removed and replaced). In most cases, not reaching or maintaining cure temperatures can cause an incomplete cure. 

Infiltration should be addressed before installation to avoid a cold spot at the infiltration site. It is critical to monitor thermocouples at the ends of the installation to keep the curing medium within the correct temperature range. If the cure gets too hot the styrene will boil and a leave a brittle liner. For larger diameter or critical pipelines, you should use a continuous temperature monitor running the length of the pipe. With careful monitoring, curing issues can be addressed before leaving the site.

Are you in control?  

Re-establishing laterals incorrectly can quickly cause a project to go south. Few things reflect as poorly on a lining contractor as having to go on a fishing expedition with the cutting tool to try to locate lateral openings. Your most experienced operator should control the cutting tool with a clear understanding of the connection locations. The pre-lining inspection video should be carefully calibrated to ensure correct distances. 

Only live connections should be re-established. Deform-reform liners need to be reformed at the correct temperature and pressure to leave dimples indicating the locations of the laterals. 

Finally, it is important to control the post construction video. The camera shouldn’t be put into the pipe with the client present, or a post construction video submitted, before meeting client expectations. What do your clients expect? 

About the Author

Mark Hill is a senior project manager with RBF Consulting, a company of Michael Baker International. For more information, visit www.mbakerintl.com.



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