PWHT and PFHT for Group 3.1 - EN 13445

[ElCidCampeador]

Good day

I'm designing a pressure vessel acc. to EN 13445+PED. This vessel consists in 1 rolled plate as shell with 2 formed heads at the ends. Shell and head materials: P690QL1 (Group 3.1).
At one end of this vessel there's a stub end, material SA 350 LF2 (for which I can give PMA).

The entire vessel is supported by welded saddles mat. s355.

According to EN 13445, in my case for O.D. and thk assigned, both shell and heads require PFHT (For heads, because of the facts they are hot formed - see table 9.4-3 ; for shell, in both case they are cold or hot formed - F>5%, PFHT is required ).

(P690 plates are still heat treated by manufacturer (quenching and tempering) ).

Moreover, EN requires a PWHT too for all the vessel (see 10.4.1) according to the specification of the material manufacturer.

So, take the head: plate is quenched and tempered by manufactuer; then after hot forming will be quenched and tempered another time and then, for PWHT, it will be subjected to a stress relieving (another HT). Do you think it's right? I mean, could I skip some of these HT and make a final HT, instead of them? I'm worried about final mechanical properites of the materials of vessel after all these HT...

Another question: P690 will be welded to 350 LF2 and S355, do you think that there will be problems during PWHT with these materials? Ok PWHT will be a sort of stress relieving but...

Thanks

 

[ElCidCampeador]

Attention: it semees that EN doesn't require anymore PWHT for group 3.1 Reh=690 MPa, but it's now responsability of the manufacturer to apply or not.