colomn plates cracking 1

[benabed]

Dear members,
Attached is image taken from the inside of a crude oil stabilizer column during the turnarrond inspection. The image is showing cracks in the plates of the column made of 316L stainless steel . This is the second inspection we are facing such problem and each time we are welding the cracks with out chaging the damaged elements.
We are suspecting a chloride stress corrosion cracking to be the main cause of the cracks because the stabiliser is located just down stream the dessalter . I want your expert opinion on the problem in order to pin point clearly the true cause. If so what are the suitable solutions to be implimented .
Regards

 

[SJones]

The best 'expert opinion' would be given by a qualified engineer making a detailed failure analysis. An internet forum will only get you wild and wonderful speculation.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[pradipgoswami]

Hi Benabed,
As stated by Steve Jones a thorough failure analysis(Not Speculative)and resultant engineering or operational modifications would add to long term solutions and would be more value added. This is more so as the damage is repetitive. As you're in the petroleum industry, I presume you're quite familiar with API-RP-571. Fig-5-65 summarizes all the possible damage mechanisms for individual equipment in Crude Units/Vacuum, where multiple damage mechanism are listed for each equipment, which is good to start with. Hence through failure/damage investigation would help to move forward.
Additional resource could be NACE publication 34109:Crude Distillation Unit—Distillation Tower Overhead System Corrosion.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[metengr]

Well said, SJones.

 

[Chumpes]

hello
difficult to produce an explanation without detailled characterization.
one side of a crack is wide open and the other side is quite close : displacements were not homogeneous, maybe there were unexpected bending effort...
it "looks" like it seems to be a mechanical failure to me, but it has to be confirmed.
Cl-SCC cracks are very easy to detect thanks to their pecular shapes
regards

 

[benabed]

Chumpes,
Attached more images showing the cracks of the column internals to support ma assumptions.

Regards

 

[Chumpes]

any possibility for fatigue bye differential thermal dilatation in your system ?
can you confirm that liquid water is expected within the operating conditions for activation of Cl-SCC ?
I should be confirmed but i believe these don't have the shape of Cl-SCC cracks, again it looks purely mechanic to me