avoiding pwht on thick materials. 4

[rsauk]

I have a situation where 57mm.thick.cs. nozzles will be welded to vessel(set-on type) which is also 57mm. thk.(cs.)
It has been suggested that somewhere in ASME V111 div.1 or 2. it is possible to avoid pwht.
these nozzles are new nozzles which will be welded in-situ.

Does anyone know if there is some credence to this info.!!

 

[moseley]

rsauk,
You might want to look at ASME VIII Div 2, Table AF-402.1.
It gives some special exceptions to this rule, but from what I can see you must PWHT if the vessel was PWHT, If it were me I would say yes it must be PWHT especially with the thicknesses you mention. Hope this helps.

 

[VDK44]

Dear RSAUK,
It is a very good question of a practical background. You can apply a 13 mm buttering of INCONEL weld overlay on the bevels of both the nozzle as well as the shell and then weld the connection with inconel welding. This is a costly proposition, but technicalyy very sound and does not call for PWHT as per code due to INCONEL welding.

I think there is a technical article on the subject of avoiding PWHT of thick vessel closing joints by certain other buttering technics. When I come across with it I will inform you. Meanwhile the method of INCONEL buttering as suggested above can be surely adopted and I am very confident of the same.

If you can send me the drawing of the vessel or the detail of the connection with dimensions and MOC I can examine further out of my technical interest based on my knowledge and experience for over 34 years in the field of Design and Detailed Engineering of Heat Exchangers and Pressure Vessels including High Pressure Heat Exchangers and good acquaintance with ASME Codes and other codes.

Regards.
V.DWARAKAKRISHNA.
E-Mail: dwarakakrishna@sify.com

 

[rustbuster1]

My first question is why are the nozzles and the shell the same thickness? Surely the code calcs do not make this necessary. My second question is what is the Matl of Construction?

The National Board and API have options for welding without PWHT. These include using preheat in lieu of PWHT and also the use of temperbead welding. This is also addressed by the ASME code - I thin in Section IX - but is nevertheless a well-founded option, especially since localized heat treatment has often caused more problems - mainly with residual stresses at the edges of heated zones - than it has solved.

Happy preheating or temper bead welding...

 

you should provide PWHT to the vessel especially given the residual stresses involved . You have mentioned a thickness of 57mm given this i think it unlikely that the vessels service purpose would allow you not to. You may find some loophole in a code that may allow you to bypass this but do so at your own peril. I dont think that it would be sound advice for anyone to advise otherwise

 

[rustbuster1]

It's strange for this to resurface now. I fear that Heat treater's biases are showing.
Weldng on 2-1/2in. thick steam drums and other heavy wall components is regularly done without PWHT - which can loosen the rolled-in tubes - without "peril" of any sort. PWHT reduces the residual stresses, but there are many service conditions that do not require this because there is no environment or operating condition that will cause problems if the residual stresses aare not reduced.

Knowledge and science should trump fear-mongering and myths every time.

 

[pipewelder1999]

The temper bead/half Bead temper technique has been sucessfully used on repairs in both steam generators in naval nuclear power plants and conventional boilers.

I have personally repaired cracked ligaments on steam/mud drums on material 2-1/2" thick using techniques developed by Babcock & WIlcox. They may have some information on this along with The NBIC which mentions the technique as indicated above.

The above has only been applied to repairs and alterations in my experience but that experience may be limited

G Austin
weldinginspectionsvcs.com

 

[mbag]

What is the P# of both pressure parts?

New Construction??

For NBIC Section RD-1000 it is not a question of avoiding post weld heat treatment; it is a question of inadvisable or impractical conditions.

 

[metaltrade]

the nbic nb-23 and api 510 is applicable only for vessel already in-service. if its new then youre back to asme section VIII. for me, its not about practicality or its has work before but rather compliance to the code requirement. you maybe exposing your compnay to liability risk but circumbenting code requirement.