Crack on Oil Line
Crack on Oil Line
(OP)
A underground crude oil line had a unusual failure recently as indicated in attached picture.
It was a crack type failure but UT inspection on crack location and on near by material did not find any internal / external corrosion or any material defect like inclusion, lamination etc.
Pipe line is about 40 years old with 5L-X52 spec. and 9.5 mm thk. Operating at about 100 psig / 150 degF
Could any body have any suggestion for possible failure mechanism
Thanks
It was a crack type failure but UT inspection on crack location and on near by material did not find any internal / external corrosion or any material defect like inclusion, lamination etc.
Pipe line is about 40 years old with 5L-X52 spec. and 9.5 mm thk. Operating at about 100 psig / 150 degF
Could any body have any suggestion for possible failure mechanism
Thanks





RE: Crack on Oil Line
Is the OD surface of this line coated? It looks like a series of pin-hole leaks but I could not tell if what I am viewing is the actual exterior surface of the underground pipe or a coating.
How did you perform NDT to conclude the above? Did you send a crawler robot down the pipe to view the ID surface and conduct NDT? If not, I would recommend it.
RE: Crack on Oil Line
RE: Crack on Oil Line
RE: Crack on Oil Line
OD surface is coated with a tape wrapping which has deteriorated over last 40 years.
UT inspection was carried out by an ASNT-II technician over the crack and nearby area, but nothing abnormal was detected
Crawler can not be sent inside the pipe as it a live and very long line, though future intelligent inspection is planned.
Stanweld- Some more closeups are encliosed for further review.
Brimmer - information as above
Additional information:
This the second time that this type of failure has occoured in less than one year.
The crude oil has some sulfur ( o.38%wt. ) and some H2S which appears to be increasing over last 10 years. 10 - 20 ppm H2S has been detected in the confined vapour space of the storage tanks. Please remember this is not the H2S measured from the crude oil sample but the free H2S in the vap. space. There may be some more H2S dissolev in the crude.
Could this be HIC??
RE: Crack on Oil Line
Check this abstract:
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"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
RE: Crack on Oil Line
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RE: Crack on Oil Line
Now, is there any way to check / confirm / evaluate if the line is under HIC attach. Any inspection or test on the line. The leak spot is already under welded box sleeve (After installing mechanical clamp). So the pipe surface is not accessible near the leak.
Is intelligent pig inspection for crack detection may be usefull for detecting cracks which may be developing at other location?
Thanks
RE: Crack on Oil Line
RE: Crack on Oil Line
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Crack on Oil Line
RE: Crack on Oil Line
If you do more digs, make sure to clean the surface and complete MPI (not just UT inspection), if you can see the morphology of the cracks it will help. If we had a picture of the indication with MPI we would be able to most likely give you a definite answer on what type of crack this is. I still don't want to take a guess, with HIC I have seen on pipelines the cracks are not usually this long (though there is no scale). Could be HIC, SSC, I wouldn't rule out regular external SCC (given that it is tape coating), or even a manufacturing defect (like lamination that has grown from fatigue over time).
Not to beat a dead horse, but really the NDE crew should have detected something, how can they not?
RE: Crack on Oil Line
MCI or Stress Engr in Houston should be good help; more than a few consultants could miss this one,if you have it.
RE: Crack on Oil Line
RE: Crack on Oil Line
- Line size is 40"
- Actually MPI was considered but due to leaking oil from the live line, we had to abandon the idea.
- UT was carried out but there was nothing unusual found.
- Actually this line had other leaks also in the past but all leaks were due to external corrosion due to wrapping damage and associated corrosion. Only the last two failures in one year were like this strange crack like appearance.
- There are three grades of oil transported through the line in batches but line is always under operation with many batches of these grades of oil from a producing field to the tank farm. One of the batch is at elevated temp of 150 OF but other two are at normal ambient temperature
Thanks
RE: Crack on Oil Line
Given the multiple leaks it appears that low frequency ERW issues are not a determining factor. But whatever amount of this pipe remains in service, this is an issue that requires your proper diligence in future.
FWIW, I googled a picture of that Enbridge leak last year in western MI in a local online newspaper - it was a single, long, very straight longitudinal split; my best guess is corrosion along an ERW seam.