T22 U bend heat treatment

[alexx]

ASME code does not require T22 tube bends to be post bend stress relieved.

However, what is the industry practice? Should T22 material bends be stress relieved to reduce possibility of cracking or corrosion. Or perhaps these are non-issues with this type of material?

Thanks,

Alex

 

[metengr]

This is dependent on service conditions, and is client driven. For heat exchanger applications in a wet environment, I would recommend a post bend stress relief operation of U-bends to reduce susceptibility to corrosion fatigue.

For steam conditions in a boiler reheater or superheater, I don't see any benefit in performing a post bend stress relief.

 

[alexx]

The application is a steam boiler so the U bends will see water, steam and a mixture. Most of the unit in fact will have some wetness except the bottom couple of rows which will be superheat. I guess in this case post bend stress relief would be required.

In this application, the water conductivity is low (ie. 0.25 microseimens)so . Exhaust gas is based on combusted natural gas with no sulfur.

Thanks,

Alex

 

[EdStainless]

With T22 I would not post-bend stress relieve. The risk of screwing up the heat treatment is greater than the possible benifits.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[metengr]

edstainless;
You must be thinking of T91 material. You really cannot screw up the heat treatment of this material unless the stress relief temperature gets away, and you re-austenitize (1600 deg F) and quench. The T22 tube materials are very forgiving, and are commonly stress relieved after welding attachments during fabrication of tube assemblies.