MAWP for nozzle loads and vessel supports

[mechengineer]

Hello everone,
So far I have not found any design of pressure vessels and heat exchangers with the condideration of using MAWP to analyze the nozzle loads and the support loads on the vessel. Even if the MAWP was higher than the design pressure indicated in the calculation report, but it was still used the design pressure for nozzle external loads and support calculation. This may be because it has no option provided by the software for using MWAP to analyze a nozzle loads and vessel supports except a designer use the MAWP to replace the design pressure and rerun the whole calculation again. In this case, I think that the two design reports to be provided, one is based on the design pressure and another is the MAWP.
I am not so sure if it is only me with such issue. Welcome peers to share your experience here. Anybody has had the experience in using the MAWP to nanalyze nozzle loads and vessel supports in your real design before? Or as a reviewer/inspector, you noted that some design had considered the MAWP into the nozzle loads and support design, welcome to share the cases here.

 

[ali.pk]

Which software are you using for that matter?

COMPRESS has this option of evaluating nozzle loads based on MAWP. It uses calculated nozzle MAWP and uses the same to perform nozzle piping laods as per WRC 537 (or WRC 107).

Regards,

Asad

 

[MJCronin]

I am at a loss to understand how the MAWP directly affects the analysis and design of pressure vessel supports.

(Of course this is aside from the usage of the ancient Zick methodology for the design of saddles on horizontal vessels)

Assuming the rest of the vessel is properly designed and meets ASME requirements, how does a change in the MAWP specifically affect the design of the supports ?

Explain what you mean .....

How does an increase in MAWP affect the following ???

- Pressure vessel legs on vertical vessels
- Pressure vessel lugs on vertical vessels
- Pressure vessel skirts on vertical vessels
- Pressure vessel lifting lugs

MJCronin
Sr. Process Engineer

 

[ali.pk]

@MJCronin (Mechanical)

I cannot explain all at once, but I can explain the effect on saddle (As per Zick's Analysis)

In the zick analysis check is there are two check for longitudinal stress between saddles.
1) Compressive Stresses
2) Tensile Streses

There will be no direct effect on the compressive stresses. But as far as the tensile stresses are concerned, they do depend upon pressure, i,e,

Sp = P x R / (2 x t)

In this equation if you Put P as an MAWP instead of design pressure, the reasult will definitely show more induced longitudinal stresses.

Regards,

Asad

 

[SnTMan]

MJCronin, it generally has to do with the thickness of the main shell elements above what is required for pressure. As MAWP is above design pressure, less excess thickness is available to resist external loads.

Regards,

Mike

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

 

[mechengineer]

@ali.pk, I use PV Elite. Does it have the option (MAWP) for vessel support by Compress?