Corrosion Allowance for Nozzles

[Mani]

Hi,

Good day,

If user specify corrosion allowance 1 mm for shell, toricone and 0 for top dish end. Its a vertical silo.
Now my question is what would be the corrosion allowance for the nozzles on shell, toricone and top dish end?
Does manufacturer of pressure vessel can use 0 for all nozzles?
Is there any rule applicable as per ASME VIII Div. 1?

Thank you.

 

[prex]

No rule on how much allowance in Div.1, c.allowances are specified by user.
You would use, for nozzles, the same CA as for the part in which they are located, unless the material for nozzle is different (e.g. SS instead of CS).

prex
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[gr2vessels]

The content of the silo appears to be corrosive to the MOC of the silo, where the content is in contact with the shell and bottom cone. Since the content is not in contact with the roof, you can remove the corrosion allowance from the top. Accordingly, the shell and bottom nozzles will be subject to corrosion and 1 mm corrosion allowance shall be included in the thickness calculations. The roof nozzles are not subject to corrosion, hence no corrosion allowance apply on nozzles.
Cheers,
gr2vessels

 

[Mani]

Thanks a lot gents, really appreciate.