Vacuum Pressure Rating

[steris]

Hi All,

We make vessels to Section VIII Div 1. The MAWP for internal pressure was established by burst testing as per UG-101(m) because there are no applicable rules for our design. We are now looking to add a vacuum rating to the vessel. How can we go about this? The rules for external pressure are not applicable. It wouldn't be practical to build a pressurized enclosure around our vessel to do an external pressure hydro-test. The only thing I can think of is FEA using the Div 1 stresses. However, since we don't have properly trained FEA experts in house I was hoping to avoid this route. Any help would be greatly appreciated!

Best,
Steris

 

[trottiey]

It is common practice to sweep that underneath U-1(c)(2)(h)(1). But then I don't think you could stamp the vacuum rating on the nameplate.

We had a similar case last year, and in the end we built a custom pressurized enclosure for the specific part that needed an external pressure test.

If you want to use FEA, that's Div. 2, not Div. 1.

 

[steris]

Hi Trottiey,

Thanks for the information. It is my understanding that you can use FEA for Div 1 as long as you maintain the same safety factors as Div 1 ie. use the same allowable stresses. I know of more than a few different manufacturers that do this for unusual designs and claim U-2(g) for acceptance.

I agree with you that U-1(c)(2)(h)(1) could apply but wouldn't be justification for stamping vacuum on the name plate.

Thanks again,
Steris