ASME B31.3 2020 Impact Test Requirement Changes 1

[tiz99]

Hi all,

Does anyone know the reason for the impact test requirement changes in 2020? Specifically the minimum temperature requiring impact testing changing from -29C to -18C?

I can't find any commentary. I expect it to be based on some material science discoveries?

Thanks in advance,
Tiz

 

[DekDee]

It would help if you noted specific clause or Table that has been revised. (or specific material)

 

[tiz99]

Paras. 323.2.2, 323.3.1

 

[TGS4]

Does the change align B31.3 with B31T?

Sorry - I don't have the 2020 Edition yet...

 

[tiz99]

Hi TGS4.

Thanks for giving me a place to start looking! I don't have access to B31T but will try and get a copy.

Do you know if there is a way to find the 'basis' for the requirements. I.e. if B31.3 now aligns with B31T, why are the requirements different in the first place?

Thanks again

 

[DekDee]

tiz99,
I started researching for you and this goes all the way back to 2015.
I have asked the original PM for clarification on the change.
There is also a proposal to include B31T in B31.3 some time in the future,
Cheers,
DD

 

[DekDee]

Tiz,
This is an informal response I received.

As a rule contractors will use filler metals that have been impact tested at -29°C when impact testing is required, but there are a lot of materials where the filler metal specification does not specify any impact testing. Engineers routinely pick -29°C as the lowest service temperature, including for system use for steam. B3 and other Cr-Mo weld metal as-welded is like glass at -29°C, not quite so bad at -18°C, not that steam systems operate at -18°C.Cr-Mos are tough as hell if they get PWHT, but code permits them to be used as-welded.

The fix is as simple as specifying the lowest service temperature as -18°C unless you plan to use a system below that temperature.

Hope that helps,
Cheers,
DD