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Corrosion in underground piping

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pbc825

pbc825

Structural
May 21, 2013
103
We're in a project to assess the condition of a groundwater piping system following observation of leaking in a line in a building. We've identified it's likely occurring by the microbiologically influenced corrosion (MIC) mechanism, which corroded an 8" sch 40 line (0.322" wall) through in a little over 6 years. The bypass line if typically not used, and the contents warm up to the building's ambient temp (just over 20C). It's unlikely to be occurring underground as the water in that piping is under the threshold for the MIC mechanism (20C vs a max groundwater temp of about 15C in summer). My question is related to tools and technology that are able to measure wall thickness (by UT) or pipe ID (I presume by laser/optical means) downhole in an 8" sch 40 pipe and 6" sch 40 pipe. Does this technology exist? I'm thinking the petroleum folks might have some tools up their sleeve. Any insight or experience with this would be helpful.

Thank you in advance for any responses.
 
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Is this ID corrosion or OD? Have you verified this with eyes on metal?
There are remote camera inspection tools as well as ID measurement tools (IRIS is one). Either of those will rely on your cleaning of the ID as well.
And don't rely on temp to control MIC, it won't work that way. It may be slower when cold but there are cases of MIC damage in cold systems also.

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Thanks for your reply EdStainless.

It's corrosion on the internal surface. Yes, we've looked at the exterior (painted), the a pinhole through an elbow with iron oxide staining around the pinhole, and the interior from a flange (unpainted). The elbow is not visible from a flange. We then did an extensive A-scan corrosion survey. The holes are highly local.

Thanks for your input on MIC vs. temp. Even in the building, the straighter sections of pipe (elbows and pipes away from bypass tees) are not tending to corrode by any mechanism per results from the corrosion survey. I trust that downhole segments would be corroding at s similar (but lesser) rate compared to the "straight" sections above ground.

What is the typical control mechanism for MIC? Chemical treatment like chlorine?
 
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There are a lot of microbial control systems out there. Chlorination is one way to go, mostly hypochlorate. There are other ways to go from something as simple as hydrogen peroxide to very complex (and effective) synthetic biocides. Talk to someone like Suez or Ecolab or Evoqua or someone else in that business.

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If you really need to know, then try this
Basically anyhting above 4" nowadays can be inspected by UT pigs, either tehtered and pulled through or pushed.

Of you don't have too many welds or flanges, Long range UT LRUT or sometimes called guided wave UT can do up to 20+m, but as soon as you get a weld it doesn't extend very far beyond that weld.

A lot depends on length of the section, ability to access the inside, can you run it full of water?, radius of the elbows, any tees, changes in ID, things sticking into the pipe etc etc

But what exactly is a "groundwater piping system"? Fancy name for a drain?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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You know in many cases people remediate these lines by blasting the ID clean and installing a full length polymer liner. There are a number of different systems available for this.

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You can use ultrasonic piging, contact a company on this subject they will access you. Microbiologic corrosion is normally fighted with some kind of biocide chemicals.

luis
 
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Thanks to all for your responses. Much appreciated.

I don't think there's much to follow up on. I'll post if anything revolutionary arises out of this work.

LI: The groundwater piping system pumps groundwater out of a well and into a holding tank.
 
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