PWHT 1

[Downhand]

Section 331.1.3 in B31.3 talks about governing weld thicknesses for branch connections and fillet welds at slip-on and socket welding flanges and piping connections. I find this confusing. Could someone explain it in plain english? Thank you.

 

[metengr]

Plain English;
Basic requirements - in a weld joint the thicker of the two materials being joined determines PWHT with exceptions based on joint type and base materials;

(a) For branch connections you are comparing the thickness through the weld in any plane to material thickness to determine PWHT requirements.

(b) For fillet welds at slip on flange and socket welding fittings you are comparing the thickness through the weld in any plane to determine if it is twice as great as the material thickness for specific base materials.

 

[Hemant65]

If i have branch thickness as 40mm(Tb) & Header thickness as 20mm(Th), will PWHT require in this case?

 

[EdStainless]

Alloys will determine if PWHT is required.
Thickness will determine time of PWHT.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Kiwi2671]

Edstainless,
Don't forget P1 materials where thickness will determine whether PWHT is required or not,

Hemant65,
Do you mean branch 20 mm thick and header 40 mm thick ?
Regards,
Kiwi

 

[Hemant65]

Yes kiwi..branch thickness as 40mm(Tb) & Header thickness as 20mm(Th),

 

[metengr]

Thickness AND alloy chemistry determine if PWHT is required in Codes and Standards, not only alloy. The reason - residual stresses from the size of the weld regardless of thickness.

 

[Hemant65]

metengr,

Design Code is ASME B31.3
Material of branch: A516 Gr.70, Thickness of Branch: 40mm
Material of Header: A516 Gr.70, Thickness of Header: 20mm

Now could you please let me know that PWHT is required?

 

[metengr]

Yes, PWHT is required because the branch thickness >20mm.

See Table 331.1.1

 

[Hemant65]

metengr,

What about as per 331.1.3 (a)?

 

[metengr]

What is the thickness through the weld? I had assumed you have a stub in - full penetration weld. In the 2008 edition, the thickness for PWHT is 25mm and greater.

See below...
Heat treatment is required,
however, when the thickness through the weld in any
plane through the branch is greater than twice the minimum
material thickness requiring heat treatment, even
though the thickness of the components at the joint is
less than the minimum thickness.

 

[Hemant65]

it is not a stub in joint. Please refer Fig. 328.5.4D (1) for weld joint detail.

 

[metengr]

Ok, you have a stub on weld joint detail instead of a stub in. What is the weld throat + external weld fillet thickness????? You need to determine this and compare with above. Keep in mind that by the time you fill the 40mm wall thickness for a stub on wall thickness, you will be close to 50mm, which means PWHT.

 

[Kiwi2671]

metengr,
Would it not be classed as a groove weld and require PWHT based on being greater than 20 mm wall thickness as you stated in an earlier posting ?
Regards,
Kiwi