Suitability of SS316 + TCC for sour service 1

[Hisham Al. Mohammad]

Hi all,

I am working on a project where the service conditions & design parameters are as below:

P = 460 bar = 10,000 psi
T = 120 deg C & Operating temp = 65 -80 deg C
The medium is a gas containing 9% H2S with a partial pressure = 41.4 bar

My question is:
Is SS316 + TCC "Tungsten Carbide Coating" suitable for this severe sour service? If not, any recommendations for a suitable material?
I need to get your kind answers with evidence, please.

Hisham Mohammad
Material Engineer / Welding & Quality Engineer

 

[SJones]

What is stopping you looking at ISO 15156-3, and giving us some more information like: application, chloride content, whether TCC is sprayed or weld deposited, etc etc.

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.

 

[Hisham Al. Mohammad]

Hi Dr. Steve,

Thanks for your response. It is a GIS "Gas Injection Skid", especially for valve manufacturing.

1. No Chloride.
2. TCC may be either sprayed or welded "No action yet" however, we can do any of them to fulfill the requirement of the service.
3. CO2% = 10.78%

Please let me know for any further required information.

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[SJones]

The H2S partial pressure limit in chloride containing environments for the design temperature quoted is 1 bar a. If it can be 100% guaranteed that the fluid will NEVER drop water AND will NEVER have more than 50 ppm of chloride, then 316L would have a selection basis under ISO 15156-3, Table A.2.

Personally, if the manufacturer supports thermal spray application of the tungsten carbide coating, I would go that route to prevent issues associated with intermixed zones of weld metal. IOGP S-563, Element Data Sheet IH002

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.

 

[Hisham Al. Mohammad]

Much appreciated. One more last point, SS316 minimum yield strength is 30K. So, will the minimum yield strength comply with API 60K after adding TCC or it will not change the mechanical props?

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[SJones]

TCC will not change the gross mechanical properties of the substrate

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.

 

[Hisham Al. Mohammad]

I really appreciate your replies. Many thanks & with my regards.

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[EdStainless]

Is this location near a coast or a salt flat?
Is there any chance that the OD surface will EVER see any Cl?
And given how low the pH will be in your line I would guess that any detectable Cl amount would be enough to drive CSCC.
Have you look at using a duplex SS?
Double the yield strength and some functional resistance to CSCC.

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P.E. Metallurgy, consulting work welcomed

 

[Hisham Al. Mohammad]

Dear EdStainless,

No chance to see any chloride either on the OD or the ID.
The project is in the desert not near to coast or seas.
One of the issues I am facing is how to increase the minimum yield strength of SS316 either by adding elements or by coating it

We wanna save costs and there is a big debate between us and our client for this change and variation.

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[EdStainless]

A lean duplex alloy (such as 2101) is how you do that.
The walls might be enough thinner that the duplex will cost no more than 316.
There is no way to increase the strength of 316 in this service.
If this were a totally non-corrosive environment, you could look at cold worked material.
The low pH and H2S are not compatible with cold worked material.
And a coating or overlay is not counted toward higher strength.

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P.E. Metallurgy, consulting work welcomed

 

[SJones]

The same absence of water, and chloride, criteria will apply. The other issue will be that there won't be a material datasheet for 2101 in IOGP S-563, and there's more scope to screw up 2101 than 316L. Plus, there won't be the same low temperature performance if it is required.

Perhaps the OP would care to elaborate on the material that the client wants, and who is initiating the "change and variation"?

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.

 

[Hisham Al. Mohammad]

Actually, the material is "
Austenitic SS API 60K / ASTM SS316L + TCC" as per the datasheet.
The client is requesting to go with inconel as XM-19 and SS316/L dual certificate are rejected for them and we should have verified this during the FEED verification and endorsement before the award. We informed them that either SS316L dual certificqte or F51 is suitable for the service hence there is no deviation from the approved datasheet

So, is SS316L dual certified suitable for this design temperature and design pressure?

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[EdStainless]

If you are designing using 316L you have to those allowed stresses.
Unless you are working to 316 (straight grade) with the L chemistry.
Your temps are low enough that this would work.
It will take a lot of material.
XM-19 is a superior option strength wise and you don't give up anything in corrosion resistance.
In terms of higher alloy materials there are a dozen options.

Steve, the lean duplex alloys are very easy to weld, nothing like the superduplex grades.
And for the lean alloys the temp range of -40C - 315C is very conservative. They perform well beyond this range on both ends.
I have done weld impacts at -52C without issues.

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

 

[Hisham Al. Mohammad]

EdStainless
You mentioned: "if you are designing .... you have to those allowed stresses". This semtence is not clear for me. Please elaborate

Moreover, is 316L not suitable for these design parameters?

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[SJones]

So, whose datasheet is being rejected: the client’s own from FEED/contract, or your revised interpretation of it produced for the execution of the contract?

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.

 

[Hisham Al. Mohammad]

The datasheet that we developed from FEED is approved as IFC approved with no comments. In this DS the material is mentioned as below

Austenitic SS API 60k / ASTM SS316L + TCC

But when we informed and started placing the POs and submitting the vendor drawing, the client requested to change the SS316 qs it is not accepted for them

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[SJones]

You will only get through this if the client gives you clear instruction that there is no water, and less than 50 ppm chloride. My guess is: they will simply say that that is your job to tell them, and if you can't, then the 316/316L will NOT comply with ISO 15156-3, and you will be changing your purchase order to a more expensive material. I'm also guessing that they are asking for something like 625.

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.

 

[Hisham Al. Mohammad]

They informed that it is our responsibility to select the material and they agreed to use F51 however, we want to raise a variation order IN CASE SS316/SS316L "dual certified" is suitable for the service & design parameters. If not suitable, then we should bear the additional cost.

Regarding the water and Cl contents, it is confirmed that there neither water nor chloride are present in the composition. Moreover, there is no possibility of water formation as well.

Based on the above, SS316/L (dual certified) will be OK for the service, 10,000 psi design pressure, and the mentioned temp range.

Please correct me if I am wrong and confirm my understanding.

Hisham Mohammad
Senior Project Engineer & Materials Engineer

 

[SJones]

"Regarding the water and Cl contents, it is confirmed that there neither water nor chloride are present in the composition. Moreover, there is no possibility of water formation as well."

If these parameters have been formally accepted by the client, your selection would be compliant with ISO 15156-3. However, there may be other client documentation that dictates materials selection policy and requirements that you will need to confirm as being absent before you can declare the conformity of the 316/316L selection.

Incidentally, if they are not happy with 316/316L from an H2S cracking perspective, then F51 is worse. Just a thought.

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.

 

[Hisham Al. Mohammad]

What a great & a helpful reply! Much appreciated, S. Jones.

Hisham Mohammad
Senior Project Engineer & Materials Engineer