SUDDEN LEAKS INVESTIGATION 2

[Alaa1992]

Hello guys

We are in the middle of an investigation to determine the reason leading to the appearance of a ponctual corrosion phenomena inside a newly installed 3'' SCH40 ASTM A106 process piping carrying a produced water stream inside a petroleum processing facility (water with hight amounts of H2s and salt).

The duration of line service before a COUPLE of leaks started to appears was 100 days only!!!!

Ps:the metal loss was huge in some points and leaks were been detected basically near to weld joints.

As a priliminary action we started to radiographically re-inspect all weld joints existing in this line by putting spots on the fusion and HAZ areas. The results have showed many corroded points with a huge metal loss in some of them, and this was in the base metal and/or HAZ and maybe in the rest of pipe structure! (SEE RADIOGRAPHY FILMS)
An API 570 engineer will continue this inspection by doing an overall B-SCAN to detect any other corroded areas. (mechanical/chimical analysis to pipe material and water fluid will be performed in an other step)

Meanwhile, I'm starting to search about this type of corrosion through API574 and I found myself confused between two reasons/possibilities

1) base metal manufacturing failure/default. (the pipe was manufuctered in an API certified mill and within europeans standards/requirements)
2) a Mic phenomena (microbiological influenced corrosion) or other type caused by the fluid nature and/or its non compatibility with the choosed metal nuance!

By looking at the attached photos, and according to your experience, which possibility might be the most likely to happens?
Thanks in advance for your help

Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[EdStainless]

When was the hydro test?
Was the hydro water low in Cl?
Was the hydro water treated with biocide?
Was the system drained and dried after hydro?
If any of these is no then the pitting may have happened prior to any service.
What biocide and inhibitors are being used now?
After all since this is above ground it will have a lot of oxygen in it and be very corrosive if untreated.

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P.E. Metallurgy, consulting work welcomed

 

[Alaa1992]

HY ED again

I remember your notes in my previous thread (N°thread330-467841)before strating this investigation and it was very helpful.
The case is starting to be clear now, Possibles reasons were been identified by having a greater idea about corrosion type and distribution over the pipe. (by refering to API574)
Concernning your questions i can answer by
1) hydraulic test was performed in january 2020 and comissionned 1 mounth later.
2) Test fluid was fresh water (Low C% with Cl)
3) No
4)the system was drained and drying operation with an inert gas was postponned i remember.
PS: The same process (dewatering immidiately & drying later) repeated with other process lines (oil & instrument air piping) and
no pits were detected (a regular inspection was performed and no metal loss or corrosion appears). Do you think that a such
''Mistake'' could result a similar corrosion forms in a short duration? like this?.

5) Corrsion inhibitors are used in other lines/purposes, but not in this particular produced line piping! And i found this very strange.
Another observation is that all corrosion locations are in the bottom part of the pipe body. for this i'm guessing about fluid settlement (in addition to its nature) might be both a strong reason to such a problem (and not metal manufacturing default).
your opinion?



Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[SJones]

Failure analysis by internet forum, don't you just love it. What is the water analysis? What checks have been made for microbial infection? Location of the leaks: upstream/downstream of welds, o'clock position in the pipe? Flow rates, dead legs? Try to rule MIC in, rather than out.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[Alaa1992]

@sjones

All things you re asking for are under analysis, and when problem is solved, I will share causes with you in particular
Till that time, I m sharing this here to get/know:
1)if any similar failures (with same conditions) happenned somewhere and this is can be very helpful for all members
2) verify my failure assumptions mentioned above and how much it can be right/logic

Have a nice day

Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[EdStainless]

If the pits are mostly in the bottom I strongly suspect that standing hydro water and biological growth started the pitting well before service.
The lack of treatment in service simply allowed them to grow faster.
A real investigation is in order (water chem, bio profile, operating history, are there are residues in the bottom of pipes, and so on).
The problem with MIC is that there are microbes everywhere, before blaming MIC you should rule out all other possibilities.

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P.E. Metallurgy, consulting work welcomed

 

Are you familiar with the term 'bathtub curve'? Your equipment is at the start of it.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TugboatEng]

I think the poor hydro test procedure and lack of water treatment turned the bathtub curve upside down.

 

[mrfailure]

I think you should run a boroscope inside the pipe to see what it looks like there - that is where the real action is. You'll be able to see if damage is localized to the bottom or a specific location, and what type of attack is going on. Of course, ultimately you should remove a section of pipe and have a lab-based failure analysis evaluation performed to really nail down mechanism and cause.

 

TugboatEng,
Your suggestion does't hold water.

mrfailure,
I don't think you need a boroscope to know what is going on inside (and the material will be cut out anyway). This is one of those failures where the metallurgy will tell you nothing; the history and the service conditions hold the key to explaining rapid corrosion.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[mrfailure]

True, NDE is not necessary if you really are going to remove the part from service, but it is uninformed to suggest a destructive devaluation is not necessary. I can think of several mechanisms at the moment that could result in the observed leaks, everything from MIC to erosion-corrosion to pitting corrosion. This kind of characterization in an FA investigation is really necessary to identify actual cause of failure and necessary corrective actions to prevent future failures.

 

[Alaa1992]

Hello guys
We opened transversely the concerned pipe and besides to the leak shapes (see photos bellow), we noticed the presence of chlore, salt and sulfur impurties.(More laboratory tests will be performed)

Api570 and API574 inspectors are working now on the possible reasons of such corrosion shapeS and the most propable thing was Mic or material nuance incompatibility with similar service conditions.
Your interpretations.

Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer

 

[EdStainless]

Since it is all in the bottom I lean toward either deposits (mud and such) settling out or the effects of untreated hydro water sitting in there. When piping is drained there will be a small amount of water sitting in the bottom of the pipe. As it evaporates all of the impurities will be concentrated. And while it is sitting there any microbes present have a chance to start growing.
What is your flow velocity in this?
What did it look like before it got cleaned off?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[mrfailure]

It would be worth it to take a cross-section through some of the pits early in their lives so you can see whether the pitting is hemispherical (like oxygen pitting) or if instead the attack looks like internal attack as is often associated with sulfate reducing bacteria (SRB) under MIC attack. Regarding MIC: the ID surface does not have the slimy and dark discoloration often associated with microbiological attack.

 

we noticed the presence of chlore, salt and sulfur impurties.

By 'chlore' I will presume you mean elemental chlorine (impossible) or chloride ions (extremely elusive and not visible to the eye). Similarly I don't know how one can visibly observe something like 'sulfur impurties' [sic]

If there are salts, get them analyzed at a chem lab. Get a sample of the fluids running through the pipe and get analysis performed at the same lab. Those results will form only one facet of the story though.

Reading some of the comments I see we are officially into full speculation mode. The only person who can solve this for you is one experienced in the process and associated corrosion mechanisms. This person will be able to recognize upset conditions not only by the forms of damage, but by interrogating Process Engineers (good luck finding one, they are numerous around refinery and CPI but always seem to go missing during failure investigations) as well as Operators and Inspectors.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Compositepro]

It appears that weld spatter that dropped to the bottom inside of the pipe may have been involved, as well. Maybe flux.

 

Correction, make that full hyperspeculation mode.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Compositepro]

The facts that the pits are only seen very close to a weld, get bigger and more frequent closer to the weld, and appear only in the bottom section of the pipe, do not suggest any ideas to you IM? Like many of your posts, this last one was not very helpful to anyone. I hope you display more positive behavior at work.

 

[SJones]

@Alaa1992 - try to obtain a copy of ASTM G161 and work through the checklist within it.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

Compositepro,

One of my positive behaviours 'at work' is to refrain from speculation when the discussion is out of my field, and if I have an opinion I will qualify it as such.
One of my actual fields of activity is metallurgical failure analysis, and I can assure you it is not done by crowdsourcing.
I fully stand by my comments.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."