B31.1/B31.3 Nominal Material Thickness for Slip-On Flanges

[WDSeng]

Hello,

I have searched and read past posts but did not find any related to the specifics of my following topic.

ASME B31.1 and B31.3 PWHT exemptions reference nominal material thicknesses when determining if PWHT is mandatory. Their definitions of nominal material thickness are listed below
[ul]
[li]ASME B31.3-2016 para. 331.1.3(c) states "The term nominal material thickness as used in Table 331.1.3 is the thicker of materials being joined at the weld."[/li]
[li]ASME B31.1-2018 para. 132.4.3 states "The term nominal material thickness as used in Table 132.2-1 is the thicker of pressure retaining materials being joined at the weld."[/li]
[/ul]

I understand how one would determine nominal material thickness when dealing with pipe or weld neck flanges. However when using slip-on flanges how does one determine the nominal material thickness? Is it 'A' or 'B' as shown below or perhaps something totally different. I am requesting help determining this specifically for slip-on flanges.

I respect your expertise and appreciate your help on the matter.

Thanks in advance.

 

[SnTMan]

Can't speak to the piping Codes, but under Sec VIII, Div 1, and for welded assemblies of carbon and lo-alloy steels, this so-called "governing thickness" is defined as thinner of the two parts joined; i.e., the nozzle neck.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Dhurjati Sen]

Dear WDSeng,

When you are using a slip-on flange, do you go for a butt weld or a fillet weld?

Does this give you any clue?

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[david339933]

Wrong part of 331.1.3.....read 331.1.3 (a)(1) and then 331.1.3(b)(2)......

 

[WDSeng]

SntMan,
Thank you for your insight.

Dhurjati Sen,
Thank you for your reply. A slip-on flange requires fillet welds (as shown in my screenshot above) and no that doesn't provide any clue.

david339933,
Thank you for your reply. Para 331.1.3(a) defines the term control thickness and per 331.1.3(a)(1) and 331.1.3(b)(1) the control thickness will be the fillet weld throat. This I understand, however the reference to "nominal material thickness" in Table 331.1.3 is still unclear. See the table below which references control thickness (green highlight) and nominal material thickness (yellow highlight).

Para. 331.1.3(c) states "The term nominal material thickness as used in Table 331.1.3 is the thicker of materials being joined at the weld."

All,
How does one define nominal material thickness for a slip-on flange?

Thanks and everyone have a nice weekend.