PWHT with impact test

[farzam]

Hi all,

we have a filter(OD=508mm, 25thk, 714mmLG)and material is A516 Gr60.based on MDMT=-45c, impact test is required and the service is not lethal, but our client has made a comment that PWHT is mandatory with reference to UCS-79.
please let me know your idea and direct me to find the best solution.

Thank you very much

 

[ijzer]

Its a boarderline case. The calculated fiber elongation is 4.92% so it does not exceed 5%. According UCS-79 no heat treatment required. If actual wall thickness is 25.5mm or more the Client is correct.

 

[robsalv]

I'm not up to the ins and outs of ASMEVIII, being in Australia, but as a client my default would be to spec PWHT in that circumstance.

I would be happy to entertain an argument to the contrary though from my PV fabricator or designer - as it might result in savings.

However, hanging on 0.5mm seems like splitting hairs and natural conservativeness might say "Stick with the PWHT". What if the plate thickness came in over tolerance??

Some other considerations: What weld process is planned? What NDE is specified??

A 25mm full thickness pressure welds mean a good chance for undetected defects to lurk and possibily bring the vessel undone should the low temp be reached and combine with detrimental residual stresses...

... I think I just convinced myself to stick with PWHT.

Cheers

Rob

 

[metengr]

Most Codes of Construction provide MIMIMUM requirements for design and fabrication. Once can always specify more requirements that go above and beyond code. In this case, I would go with PWHT.

 

[ijzer]

The ASME Code para UCS-79 has nothing to do with welds. It is about Heat Treatment of plates/heads after cold deformation. In that respect PWHT is not the correct abrivation. Better use PFHT (post forming heat treatment)

 

[robsalv]

...hehehehe, well I did say I wasn't ASMEVIII savvy.

Still, if you're swinging on a 0.5mm / 0.08% argument... doesn't sound like much of an argument.

The practical logisitics of PV manufacture in Australia would drive the vessel to be PWHT'd.

Cheers

Rob

 

[rhg]

1) Please, read UCS-79 slowly: fiber elongation is greater than 5%
2) Plate SA 516-60 t=25 mm shall be normalized and Charpy test shall be at -51°C (see SA-20), the WPQT impact test shall be at -45°C.

I you think that these test pass the requirements without PWHT ...so no PWHT be performed.

I recommend PWHT

Remember: all weld shall be full penetration

Regards
rhg

 

[farzam]

Thanks to all

regarding ucs79, for fabrication by cold forming, when the fiber elongation is more than 5% and the material requires impact test, PWHT is mandatory,but in my case, the elongation is not more than 5%,and PWHT requirement is not mentioned at my clinet SPEC.but for this case they insist to perform PWHT.