UG-45 Question about corrosion allowance 1

[brandonb73]

Must the corrosion allowance for nozzles referred to in UG-45 be the same as that specified for the shell/heads or can it be a different value?

 

[metengr]

If the nozzle is of the same material as the head or shell, yes. If different material, it can be a different value. Read UG-25.

 

[prex]

I would be less sharp than metengr: there is no obligation of having the same CA for nozzle and shell, when the material is the same. One can easily imagine situations where CA for nozzle could be higher than for shell (e.g. erosion due to fluid velocity). However, if your intent was to have a lower CA for nozzle (same material), then you (or the process engineer) should justify that based on UG-25 criteria (rate of attack).

prex

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[SnTMan]

And some customer specs require more CA on the nozzles.

Regards,

Mike

 

[vesselfab]

i've seen different corrosion allowances of different parts of shell in vessels and different corrosions allowances on nozzles in the same vessel.

it's all up to the end user and his process