Corrosion allowance for bonnet extension

[k2012]

Hi,
Customer has specified corrosion allowance for the valve as 3 mm. Valve is Globe Valve with extended bonnet. Our design is with standard bonnet welded with extension part. This extension part can be a pipe or from bar. Need your help in understanding if the corrossion allowance is applicable on this bonnet extension also or it is limited to body and bonnet only. References to related codes and standards would be helpful.

 

[valvit]

Customers typically expect the corrosion allowance to be applied to any pressure containing part that is exposed to pipeline media. If the purpose of having an extended bonnet is to move the stem seals out of a low (or high) temperature environment, then most likely your extended bonnet is pressure containing, and the CA requirement would apply.