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

HY ED again

I remember your notes in my previous thread (N°thread330-467841: LEAKS ON NEW INSTALLED PIPE : API 5L GRB PSL1 and or 2)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

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

www.linkedin.com/in/drstevejones

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

@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

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."

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

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."

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.

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

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?

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P.E. Metallurgy, consulting work welcomed

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.

Quote (Alaa1992)

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."

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."

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.

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

Steve Jones
Corrosion Management Consultant

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."

from the discussions, few things i can make out. In my experience, elimination approach is the best to work towards root cause:

1. There are pits waiting to leak - possibility that pits are available before use too - pits which are breeding ground for corrosion.

2. Doesn't look like MIC, but you can always rule it out by conducting an SRB test - contact yr labs/expert for what they can offer - SRB is particularly important as you have already mentioned that you could "find/see" contaminants near the sites - though these sites can also become deposition ground without the visible deposits being actually responsible for the leak. Thus below point is important.

3. Go for an SEM analysis with EDM - but do it on a raw UNCLEANED sample - difficult to get if you have flushed the line out or anything of this sort - this will tell you what deposits are actually available at the defect site and will help you a great deal in narrowing down the reason.

Keep us posted. Wish you the best.

HY SJmetallurgist.

Thanks for your Post. We are starting to narrowing down causes. The only disturbing parameter for us is the short period of corrosion (High corrosion rate value, How this can be possible);it took only 1 mounth for a 6'' line and 4 mounths for the 3'' pipe before leaks started to appear. (FYI: Both line are carrying a produced water to a tank storage battery).
Reagrding to the poor separation process with a hight amounts of salt & H2S existing in the produced water (only 1 operating vessel working among 6 in total), We are thinking about 3 possibilities:

1) A MIC due to bad fluid properities: this possibility seems the most likely, espeacialy when we cutted longitudinally the 6 inch pipe and observed a possible bacterial phenomina(see photos). Samples of internal contaminated surfaces besides to the produced water itself, have been taken to a specialized lab in order to perform an SBR tests and figure out for wich degree this can be possible. Did you encountered such event/ any comments here ??






2) A bad pipe quality (Mech & Chem properities) or a bad steel nuance selection: Personnaly i exclude this for many reason:
a) We used the same pipe (nuance, diameters, Heat numbers) in other process purposes (Processed oil lines, well head crude oil riser piping & fresh water lines)and no problems at all.

b) Our pipe supplier is well reconized
in Europe.

c) if we assume that propirities are
bad, the period of leaks appearance
would'nt be within 4 mounths only
and, if so, many other leaks would
appears intensively in different
locations.

d) According to my knowldge, Carbon
steel in general (e.g, A106, PSL1/2,
A53) with a composition of ''99% iron
and 1% = %C, %Al, %Mn etc..'', cannot
be cheated. For the mill itself, it is
not benificial and redicilious to
cheat in carbon steels. :D

E) The removed A106 pipe was in
operation scince 1992. It contains
many metal loss areas and this is
normal with years but never
had similar failures in its first
years. We can explain this with the
fact that old piping was operating
with 6 speration units in full
service. however, the new replacement
is working with a produced water
comming from only 01 seprator which
make product very corrosive.

Through all of the above, i strongly suspect to the fluid/service conditions (Point 1). But any way, we are conducting some of this pipe samples to the lab in order to confirm material certificates analysis.

3) Existing Pits as you said: Yeah, Maybe the reason was the hydraulic test or are existing previously (quality check didn't mentionned any problem). But saying pits, is pertaining to a small metal loss. Such a leaks, with the observed holes diameters and shapes,(see previous photos), are big within a short period.? this is where the pardox!
PS: the Majority of pits (including all leaks) were localized intensively at the lower part of the pipe (06 O'clock position).



Alaa Edine SMAALI
Energy (Oil&Gas) Project Engineer