repad - UG37 of BPVC VIII-1

[monk1999]

Does anyone know of a vendor that stock or make the repads specified to UG37 of the code. The outside contractor I work with doesn't know and I am not in the pressure vessel industry.

I thought a machine shop could make the repad from a flat piece of metal and form it to the outside diameter of the vessel...

see attachment for repad that I'm referring to.

Thanks!

 

[SnTMan]

monk1999, doubt your will find any stock, they tend to be all different. Shouldn't be a problem finding someone to make them, anybody that rolls plate should be able to do it.

Regards,

Mike

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

 

[marty007]

Any fabrication shop could make up these repads.

These repads would likely meet the requirements of UG-37, but I'm hoping you are still performing calculations to support the design. There are all sorts of special cases where these might not work (large openings/etc...).

Cheers,
Marty

 

[monk1999]

Thanks guys, really appreciate it!

@SnTman, that are probably not stock, you're right.
@Marty, yes, I did use the boiler code to confirm the design.

As a follow up question related to nozzle reinforcement. Does the boiler code allow for a saddle instead of a repad? Seems like saddle is more common in process piping world - ASME B31.3. The boiler code does mention saddle but doesn't really goes into specifics on analysis. Our vendor isn't too fond of using the repad because of the inner weld between the nozzle and the repad. As he explains it, you have a fillet on top of a weld. With a saddle, it's two fillets welds and there are no welds that stacks on another weld.

Regards,
Monk

 

[marty007]

Monk,

A saddle is listed in the code in Fig.UG-40(f), and UW-16.1(f-1).

I don't know of any software that directly models this, but it could be calculated in the same way as for a repad. The effective repad thickness would just be the saddle thickness minus the shell thickness.

Cheers,
Marty

 

[monk1999]

Hi Marty, I see what you're saying. My vendor was thinking of the saddle on top of the vessel shell, not replacing it. Has anyone done analysis for that configuration of saddle on top of shell at the nozzle? Is it significantly different?

Thanks!
Monk

 

[SnTMan]

With a saddle, it's two fillets welds and there are no welds that stacks on another weld.

Please explain, how about a sketch? UG-40(j) maybe?

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

 

[monk1999]

good point. See attachment of the reinforcing saddle.

-Monk

 

[marty007]

No attachment...

 

[monk1999]

Oops, see attached.

Thanks,
Monk

 

[SnTMan]

Hmmm, never seen such an arrangement. Nevertheless I don't see why it could not be treated as a re-pad under UG-37. It looks to me like could be treated as both a pad on the vessel wall (Sketch UG-40(b-1)) and a pad on the nozzle wall (sketch UG-40(b-2)), if that much area was needed. Subject to the thickness of the element (te) and limits of reinforcement. Also subject to provisions for a split pad (UG-37(h)).

As compared to a plain old pad, it looks like an expensive detail to me...

Regards,

Mike

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

 

[marty007]

Very expensive!

 

[monk1999]

Thanks for the input!