PWHT requirement

[Ast83]

Hi all!

I am currently calculating an equipment with 30 mm C.S. shell thickness which is not required to be PWHT, but on the I/O nozzles we have to use C.S. reinforcement pads with 40 mm thickness because of design /space requirements. Shall we have to PWHT the entire equipment only because of these pads? Is it enough to local PWHT? Or do you know if there is any exception on the Code to avoid this PWHT?.

Thanks in advance for your support!

 

[vesselfab]

you can use a partial heat treatment on the repads and stamp name plate "PHT"

The code talks about PWHT based upon thickness of welds, it does not say every weld must be PWHT.

Now, I would look at a thickened neck for reinforcement instead of pad. Use of forgings is an effective way to do away with reinforcing pads, especially when it forces you to do a local pwht.

 

[stanweld]

As per vesselfab, you may locally PWHT the weld(s) per UW-40.

 

[Ast83]

Thank you very much both vesselfab and stanweld for your quick response!. I will consult this option; regarding the reinforcement pad, in this case are unavoidable because of design matters (it is not enough with a thickened forging or pipe neck) and because of space matters it is necessary to use the 40 mm thickness in order to reduce the width of the pad.

 

[vesselfab]

If you have room for a pad, you normallyhave room for a forging.

if you don't , you can go forging with a smaller pad.

anything is better than local PWHT.

 

[bhushan76]

Not sure of the required and available reinforcement areas , however you can check if projecting nozzle neck on inside of vessel wall and reducing RF pad thickness to say 36 mm meets reinforcement calculations.


Be sure to check with yout process people , if projecting nozzle neck inside of vessel is acceptable to them , as this creates some liquid hold up when nozzle is located on bottom of vessel.

 

[Ast83]

Thanks for your answers, i think that the best option will be go for a reduced pad thickness of about 35 or 36 mm as suggested by bhushan76, as the required reinforcement area is too big to go for a forging (we would have to use thickened necks and it is a too expensive solution because there are a lot of nozzles),also the inside projecting nozzle option is not permitted for process reasons. Initially we wanted to use an existing stock plate of 40 mm thick of SA-516 Gr.65 N for these pads, but i think that we will purchase plate of above mentioned thickness and go for the maximum available pipe schedule.
Anyway i will post the final solution we decide.
Thanks again!