Thinning of burried pipes

[0481]

Hello ALL,

During operation at gas field a burried line suddenly rupture.I am working to carry out root cause analysis of pipe failure.
Details of parameters and our findings are given below
1. During visual inspection it has been observed that pipe is severely pittted from outside.
2.Locallized thinning of pipe occur during operation which leads towards rupture.
3.Fracture reveals that it is a brittle fracture.

Now in my view it may be due to Soil corrosion or Erosion corrosion.
If any one did this type of task can share with me.
thanks in advance

 

[GregLamberson]

0481

Based on the photo and your description, I would peg the root cause as poor coating application and/or poor installation.

Erosion corrosion will be internal, you didn't mention if there was internal coorision as well.

I have done allot of these type dig ups. It's not clear from the photo, but was the original coating tape?

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[dcasto]

Can not say for certain, but dig up a random spot and look at the line there.

Then look at the site you took the picture from, are there other lines in the area? Is the line conditions warm? Is there ground water that is acidic, Is there a ground bed nearby?

Ask the same about the random dig too.

Not given answers to the above, I'd look at total failure of Cathodic Protection including coating as suggested and the anodes or impressed current, if any. Time for a new line if this is true.

 

[brimmer]

Looks like typical general external corrosion of a pipeline to me. If you have more photos of the field site, and pipe after the corrosion area has been cleaned I might be able to give you more insight. I am not sure when you say errosion corrosion, how you can have this externally...
Reflecting Greg's comments above, was the pipe bare or coated? If coated what type of coating? The coating has completely failed here if it was coated. Is there cathodic protection on the line? You may want to take some cathodic readings at the site if there was. Can you share photos after you have cleaned (blasted) this piece, can't see the morphology of the corrosion with all the deposits on the pipe. There does not appear to be very much if any CaCO3 on the pipe which indicates CP was not reaching the pipe.
When you clean the pipe, complete magnetic particle inspection over the area to rule out any cracking or manufacturing defects. I would suggest you develop some kind of integrity management plan for this line, if there is external corrosion in one place this severe, chances are there is external corrosion in other places and the line will eventually fail again. You can hydrotest, complete additional excavations, run a pig (if possible), complete combination of ECDA including above ground coating surveys to select additional dig sites...

 

[0481]

Thanks to all for valuable guide line see below more detail regarding failure
1.Pitting found on internal surface as well.
2.Pipe was coated with coating tape.
3.Line condition is warm.
4.Line located in high water log area.
5.No CP system on line

 

[GregLamberson]

0481

I assume this is a flowline? Probably installed in the 60's or 70's?

What I've seen allot of times on taped pipe, whether over the ditch or yard coated, is during installation, especially in high water areas where there may have been a push, they'll get dinged and the coating damaged and no one cared back when it was installed.

I was on a project that dug up all of Interprovincial pipelines across Minnesota (18", 26", 34", and 48"). Where we had the most problem was the 26 & 34" (both installed in the 60's), they were installed taped over the ditch and in high water areas. The 48" was FBE, no real issues and the 18" was the oldest (the old hot dope, laid in the 50's) and had by far the fewest issues, but most that we found were where a push took place and the pipe bumped agains a stump orr something in the ditchline and wasn't repaired.

If it's a transmission line I would be surprised about the internal pitting.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[SJones]

Instead of getting people to speculate on here why not hire a decent provider of this type of service to undertake a detailed analysis for you (one where they can gather all the facts and look at the pieces using whatever equipment necessary)?

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[brimmer]

Wet areas and tape are usually a problem, the combination of water and soil stresses will disbond the tape coating. Water gets under the coating and you have a corrosive environment. I don't know the soil conditions to comment, but this wet environment and tape coatings has been a problem for many pipelines in North America. This type of environment has caused many pipeline leaks here. If your line runs through wetter areas and is tape coated, I would investigate further... There is clearly a corrosive environment here, the other comment I have is why is there no CP on the line? Sounds like you need help, I would take Steve's advice and get the proffessionals to look at it, we can offer advice from here but you really can't provide the kind of detail we need to give you the assistance you need. The internal corrosion has me interested, I assume it is not coated internally and there is no internal corrosion management plan either? You should consider developing both an internal and external management plan for this line, and if there are others like it, the same would apply.