ASME definition of "corrosive service"

[weldgal]

Has anyone come across a written definition of "corrosive service" for ASME Section VIII pressure vessels? I ask because UG-46(a) exempts inspection openings in vessels for non-corrosive service, but at what corrosivity is a vessel considered non-corrosive? Even air has some moisture in it that could eventually corrode steel, so I'm wondering under what conditions the user the could designate his vessel as non-corrosive?

 

[metengr]

weldgal;
Corrosive service is determined by the Owner/User or Owner/User's Design Engineer. The Engineer should be familiar with the limitation of materials and their response to process environments. Once you have determined that the material will be subjected to some level of corrosion, ASME provides guidelines for design.

 

[weldgal]

My question is geared more to the way the User determines corrosive service. Ideally, I was looking for something in writing that would explain just how low a corrosion rate has to be before it can be considered non-corrosive. It seems almost like there is no such thing as a non-corrosive service since even compressed air (which contains some moisture would eventually corrode steel.

 

[jte]

weldgal-

The way a guy who was a part of an ASME/NB code authorization review team 'splained it to me was quite simple: If you have a corrosion allowance, it's corrosive service. It's not a rate thing.

A case where you would not be in corrosive service would be a situation where you have a vessel built with clad material or some solid stainless or other alloy which would be expected to never corrode.

jt

 

[weldgal]

That makes perfect sense; thanks.

 

[deanc]

http://www.nace.org/nace/index.asp

http://www.fitness4service.com/

Heres a couple of good links to start.