Surface defect on API 5L pipe 20"

[engresague]

Hi,
I would get the recommendation of you in this uncommon case for we.
During the laying of a pipeline under construction, was found in one of the pipes, a origin deep surface defect (hole)not seen at its reception.
The hole has a conical shape, whith external diameter of 13mm and is 13mm in depth.
The pipe specification is API 5L Gr B; size 20"; WT 0.812" (20.6mm); anticorrossion coating FBE, plus concrete 2.5".
Pressure test by design 20.65bar (300psi).
The pipeline was welded in 500mtrs segments at land (onshore)before being pulled out to sea.
Now we have strong suspicions that other pipes of the same lot number may have similar defects.
So, i´d like to know which method may be recommended to detect other possible similar defects masked by the layer of concrete.
we are considering a higher pressure test (1920psi) to uncover impending failure but we are not sure about.

See attachment

What do you think about it...?

Thanks in advance

 

[blacksmith37]

I have seen a few "pits" as you describe : They had been caused by lightening strikes, sometime after the pipe left the mill (not mill defects ).

 

[engresague]

Hi blacksmith 37, thanks...

Well, if you could see the attached image, the gap is partially coated with FBE in its internal cavity, ie that already existed in this pipe before being coated whith FBE.

 

[BigInch]

Pressure testing an offshore pipeline with a known higher chance of defects seems especially risky.
I'd run an intelligent pig and start a claim against the mill to pay for that and any repairs.

 

[engresague]

Ok BigInch,
I´m agree that the pressure test is risky, but, do you know any especific intrnal smart tool for detect defects in the body of the pipe..?
Thanks

 

[bimr]

Types of Defects Detected by smart pig technology:

In general, smart pigs may be used to detect stress corrosion cracking, general and pitting corrosion.

In specific: gouges, dents, pit corrosion, anomalous weld seams, longitudinal cracks, longitudinal grooves, and general corrosion are all detectable.


Contact:

http://www.dacon-inspection.com/services/pipeline-services/magnetic-flux-leakage-pigging/

http://www.pipelineandgasjournal.co...-spiral-magnetic-flux-leakage-inspection-tool

http://www.enduropls.com/products/inspection/dfl.html#more-35

http://www.applusrtd.us/en/service/PIT_(Pipeline_Inspection_Tool)-1340227852615

 

[LittleInch]

First off you need to get the mill properly involved if not already and get them to review their test records and plate manufacture records to see where and how many you think you have more of these things. It looks to me like a rolled in defect in the original strip, but I'm no expert on material defects.

You need to find someone who is to fight your corner against the mill which could go to court, so preserve all samples and take lots of photos and records.

I can't quite understand why you have such a large wall thickness for the design pressure and in the end this might be your savior.

While it's not great, the wall thickness you have at a DF of 0.72 gives you 2000 psi design pressure. It would seem your current design pressure is about 200 to 250?

Hence do a fitness for purpose assessment using one of the known tools (31G) and look at it as a deep corrosion pit of 65% wall loss.

I suspect at 250psi it'll pass without a problem at that sort of size.

I don't know what your service is, but maybe think about lining it - structurally the pipe isn't affected, but clearly might spring a leak at some point. Running an intelligent pig and choose the right one for this type of defect - an MFL pig might pick up defects like this better even if they are not craters yet - then make your decisions.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[saplanti]

The portion on the left hand side does not seem to be a new pipe. It seems that the end portion was attached to the old pipe by welding and the hole is on the end portion if one claims that the entire pipe is new. And the end portion seems to be annealed by heating. Depending on the material type the steel may have already lost the strength due to heating.

This type of holes on the pipe are created mainly by external machine work, excavators or air tools if the pipe was laying in the ground covered.

 

[IQM]

Is very difficult to do any analysis from the picture, the first step will be send out this pipe section for a failure analysis and when you have the results from it you will determine the next step

 

[blacksmith37]

I should have looked at picture; doesn't look like lightening. Looks like external damage : We once had a larger external hole - shaped just like a backhoe tooth - not too hard to figure out.

 

[engresague]

Thanks you all for your comments and suggestions.

We are looking for a inspection company that can carry out this evaluation with smart tools like recommended per you.
The desing pressure is 240psi, service Fuel Oil.
The pipe is longitudinal seam. I'm almost convinced that´s defect in the original strip. But I do not have knowledge on material defects.
The hole was detected during the cleaning with power tool before the examination of the weld by UT. It was filled with foreign material and covered with FBE.