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In-Situ Large Diameter RAS Pipe Repair?

In-Situ Large Diameter RAS Pipe Repair?

(OP)
I'm looking to repair some large diameter (42", 30" and 20") steel RAS pipes. It needs to be a medium term solution, as we can't keep up with "patchwork" and they are scheduled to be replaced in just under 10 years. Weaknesses are at the welds and throughout the pipe wall.

Ideally, I'd like something external, so I don't have to take these out of service. As far as I can tell, internal cast-in-place solutions aren't really suitable for such diameters anyhow. I'm seeing the Henkel's Loctite Composite Repair System pop up a lot, but I don't see any case studies relevant to my type of service.

Does anyone have any experience with such repairs? Could you please share the method you used and how satisfied you were with the outcome?

RE: In-Situ Large Diameter RAS Pipe Repair?

This type of patching will work in the short term, maybe for several months and then the patch will break away or start leaking as the corrosion continues.

The preferred patch is to weld steel to the exterior of the pipe.

RE: In-Situ Large Diameter RAS Pipe Repair?

First of all, what is RAS pipe? Is it under internal pressure? how much? Can segments be taken out of service for a day at a time? What about Quakewrap?

Richard A. Cornelius, P.E.
WWW.amlinereast.com

RE: In-Situ Large Diameter RAS Pipe Repair?

(OP)
Thank you both for your replies.

RAS = Return Activated Sludge, it's the "bottom" of the final clarifiers that is being returned to the aeration tanks to help maintain the microbial populations. I am not exactly sure of the pressure, but I don't think it would exceed 200 kPa. It would be preferred to not take it out of service, but of course, if it breaks it will be out of service anyhow!

I will look into the Quakewrap. I'm not sure the idea of welding would be well received as I believe some of that area is Class I Div I.

Right now the supervisor is preferring patchwork, but I would like to see if I can offer him some better ideas.

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