Corrosion

[7mayda]

Dear,

Can someone helps me to find/tell me where is the right procedure for the corrosion allowance selection in the ASME BPVC Section VIII of a compressed air receiver 400 litres/40 bar.

Regards.

 

[metengr]

Corrosion allowance is a value that is provided based on judgement by the Design Engineer and service conditions - experience based or from literature.

For guidance see Nonmandatory Appendix E Suggested Good Practice Regarding Corrosion Allowance.

With that said corrosion allowance can be from 0.062" to as much as 0.125".

 

[r6155]

First you must select the material.
Regards
r6155

 

[7mayda]

Dear Metengr,

Is there a relationship between the corrosion allowance and material or/and wall thickness ?
Can you give me some example of a corrosion allowance for the air receiver ?

Regards.

 

[metengr]

The air receiver's I have dealt with are carbon steel. Most have no corrosion allowance because of expected service conditions. In actual service, I have seen where the bottom head and shell in a vertical air receiver corroded from the ID because of moisture carryover in compressed air.

Corrosion allowance means thicker shell material, to compensate for general pitting, which means more weight and cost. So, proper design should consider expected service conditions. As far as a corrosion allowance number, it would be in the range I stated in the post above.

 

[r6155]

For example. if required thickness (mathematical formula) is 10,5mm and selected thickness is 12,7mm, the difference 2,2mm
works as corrosion allowance.
Regards
r6155

 

[loilfan]

In vertical air receivers, the common schools of thought to protect the bottom head are to add extra CA, coat it, or drain it regularly. Corrosion allowance is just a function of how much you expect it to corrode and how long you want it to last.

 

[MJCronin]

Ioilfan ...

I agree with your comments about corrosion prevention on the lower vessel head.

But, I think that it is important to point out that there must be a functioning automatic drainage device on the bottom of the vessel and that it must be periodically inspected and maintained.

A ball valve on an automatic timer is a common choice.

http://www.ingersollrandproducts.co...condensate-management/electronic-drain-valves

Zmayda, is this the first air receiver design that you have been involved with ???

MJCronin
Sr. Process Engineer