Post weld heat treatment of shell and tube heat exchanger channels

[PumpTech81]

Hello Everyone,

As per API 660 paragraph 9.6.9 a post weld heat treatment of fabricated carbon steel and low-alloy channels shall be performed for the following:

A) Channels with six or more tube passes
B) Channels whose nozzle to cylinder internal diameter ratios are greater than 0.5

Could someone explain the reason for this requirement?
Furthermore, what should be done in the case of cladded channels? Would this requirement be still applicable?

Thank you in advance.

 

[r6155]

To restore excessive deformation after welding: 1) PWHT , 2) mechanize the channel.

Regards
r6155

 

[SnTMan]

PumpTech81, for either case, there is a relatively large amount of weld placed on the assembly. PWHT will reduce the residual stresses produced by said welding.

Clad channels would usually consist of austenitic pass plates welded to austenitic cladding or WOL. Presumably could be exempted from the API 660 requirement, upon approval of the buyer. I'm pretty sure API 660 contains no such exemption.

r1655, "mechanize the channel"? Please explain.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

Hi SnTMan
Is a good engineering practice re-machining the channel flange contact surface (turret lathe horizontal or vertical) after PWHT to warranty a good assembly with shell flange, and avoid leaks.

Regards
r6155

 

[SnTMan]

r6155, oh yes certainly, I am familiar with the practice, if not that terminology

Thanks for the follow up.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Cak war]

Hey,
They have other technic to avoid PWHT by temper bid welding technic.

 

[SnTMan]

Not for this

The problem with sloppy work is that the supply FAR EXCEEDS the demand