Filter plate designed as a flange calc - ASME VIII DIV 1

[mech8790]

Hi everyone!

Can anybody point me to the specific paragraph of ASME VIII DIV 1 when the calculations of the above flange can be made please? I would like to find out how a perforated flange with the number of holes located in the centre part of it and arranged in circular pattern can be verified by the calculations when this type of flange forms a joint with a slip on flange being located in the mid span of a shell. The holes are made to locate some filters in there so as long as the filters are not clogged there should be no differential pressure at all. Please find my sketch below (sorry for the quality). Hope you can understand what I mean.

I was wandering if the set of calculations from part UHX (rules for shell and tube heat exchangers) can be used or since this is not a heat exchanger design this type of flange/filter plate can be calculated by utilising the formulas listed in App.2 and treat the flange as a ring with the perforated section removed.

Thanks!

 

[CuMo]

Yes.
Sounds like a good plan to design the flange as a ring with the perforated section removed and see what this gives you.

You can probably design for pressure across the perforated plate using the rules for U-tube or floating head tubesheets
where the tubes are not fixed and typically do not contribute to the stiffness of the plate.

It will be up to you to determine some safe margin although you say there will not be pressure across the plate.

If the plate is of a very large diameter and you apply even small amount of pressure - you might not like the final result because UHX doesn't like too much deflection in tubesheets

Look at TEMA too.

 

[SnTMan]

mech8790, if there is no pressure stress present I'd think the design thickness of the plate would depend on only physical considerations, i.e. thick enough to accept the filters.

However if pressure design is needed, such as for when the filters become clogged, I'd think TEMA Apx A (sketches A.131 (g) & A.132 (d) seem applicable) would be much easier to implement than Part UHX.

Regards,

Mike

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

 

[mech8790]

Thank you for your quick respond. I was considering TEMA rules to apply in ASME VIII design but wasn't sure if this will be still in compliance with the code or part UHX should be followed only. If the flange is considerated to meet TEMA requirements so the u-bend configuration can be used, what will be the pressure inside the tubes (filters)? I beleive I will have to apply inside pressure to the flange itself since it is bolted to a slip-on flange and differential pressure to the inside of tubes. But then, what is the point of calculating the tubes since they don't exist and the filters are not of similiar stiffness (usualy made of plstic).

Elaborating this the other way, if the filters are not clogged, so the flange is loaded with internal pressure only and since the joint is made with a slip-on flange in theory we can utilise Appendix 2 calculations. I beleive the flange cannot be calculated as blind with number of openinngs since the uniform inside pressure is acting on each side of the flange. Usually, a flange is made in stepped or smooth form, but removing the perforated section of the flange for analysis this will generate different load case than descirbed by the code. I am not sure if the only way for getting this calculated right is to use FEA tools or TEMA rules if they are deemed to be conservative enough. I am looing forward to know your thoughts.

I have added another sketch for your reference.

https://files.engineering.com/getfi...cc21-4be3-a73b-4b55c2a24c8c&file=no_title.png

 

[SnTMan]

mech8790, you have two situations to design for:

1) The central portion of the plate need only be deigned for the differential pressure that can exist across it. This is either zero, filters clean, or non-zero, filters clogged. This portion might be designed per one of the UG-34 configurations using the appropriate ligament efficiency. It might be designed as a tubesheet although there are not two distinct, separate pressure chambers. In either case, the design pressure would be the differential pressure across the plate.

2) The extended rim or bolting flange portion is subject to the same loads as the mating flange. It might be considered ss an Apx 2 flange as you have proposed, or as a portion of a tubesheet. TEMA A.133 offers a means to calculate the thickness for this rim. Note there is not pressure term as such in this calculation, instead the flange design moment(s) from the mating flange are used.

As far as I know there are no particular Sec VIII, Div 1 rules for the design of a filter plate. It appears to be a U-2(g) component. I do not know whether current U-2(g) rules mandate a particular means to perform calculations for such components or not, but:

This component is clearly is outside the scope of Part UHX, so use of same is not mandatory. If U-2(g) permits however it or TEMA rules may be used, or a combination of Apx 2 & UG-34, or perhaps a calculation from Roark or something like it. I'd likely for simplicity go with a TEMA approach consisting of A.131, A.132 and A.133. Greater complexity does not imply greater accuracy

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

 

[mech8790]

Hi SnTMan,

Thank you for your elaboration on this problem. I believe we have got this topic sorted out.

Cheers!

 

[r6155]

See ASME VIII Div 1 UG-39 or Appendix 41. You decide

Regards