Re: [MW:28120] CRITERIA OF CLAD THICKNESS

Dear All.

thanks for your responding.

I may not describe my issue correctly.in our project documents specify just 3 mm 625 clad material, without explaining that this thickness have been considered the dilution layer( that depends to welding process and amount of heat input and might be reached to 1mm) or not .

Now this question remained this 3mm must be measured from base or not?one of our colleague's opinion is that due to high safety design factor and based on the specified requirement which mentioned in project specification, Fe content have to be measured .5 mm beneath from final layer is measured from base metal although I believe we must consider corrosion rate of clad layer (therefor it is prescribed to do ASTM G28) and occurred inter metallic in diluted area which are detrimental and weaken the resistance to corrosion environment.

it must be added that this situation getting so worse if clad layer will be stainless steels.

If anyone have access to any documents that talk about this case or corrosion rate of 625 in G28, please let me know.

Regards.   

On Mon, Jul 23, 2018 at 8:47 PM, Nitin Shetty <nshetty1981@gmail.com> wrote:

Dear Ali

The thickness of the clad should have been mentioned in the equipment data sheet and more over it should say the intent of the clad. If the thickness of the clad is only for corrosion then u need not consider clad thickness in the design calculation. If this data is missing then u need to ask the client and I wonder how it was estimated if this data was not available in the design data. The sour requirement does not come from code and usually it is dictated by the project documents so u need to find an answer to ur question in the spec for clad thickness or get in touch with ur client. 

Usually what I have seen is that the clad thickness for a clad plate is 3 mm after the manufacturing process is completed and the weld overlay part depends on the wps at what height u can achieve the undiluted chemistry. The height is calculated from the approximate weld interface (refer fig QW 462.5 a), so if the project doc does not specify then follow this.

I hope ur query is answered.

Regards 

NS

On Mon, Jul 23, 2018 at 6:24 PM Ali Asghari <asgharialigl@gmail.com> wrote:

Dear All.

Does anybody know about how a designer calculate the thickness of clad material especially for sour service and how much is conservative?

because in our project documents have not said clearly that thickness of clad have to be measured from base material or from layer that dilution is negligible and this question remained does designer account or consider dilution or not?

Regards.

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