existing HE modification nozzle concept to calcualtion verify

[ronaltao]

Dear All,

I have doubt for the concept of the modification work

the work is modification to enlarge from 6" to 8" at the existing heat exchange as same condition
normal way, my calculation use nominal thickness and set corrosion same as previous design
and then for fabrication check the actual thickness, if it is still in the value of corrosion the shell is be pass (am I correct?)

just now, I got some comment to check the actual thickness and use it for the nominal thickness and set corrosion again
but I think the comment is inappropriate, it over from previous design of shell part

I would like to correct of the concept
and please recommence the general practice and any procedure applicable and can be used.

Thanks in advance.

best regards,
ronaltao.