Allowable stress for Heat Exchanger Tube Sheet of Stainless Steel Material, Extended as Flange

[DK44]

Dears,
Need following clarifications
1. For Tube sheets of Stainless Steel materials, ASME SEC II D gives two sets of allowable stresses (Higher & Lower). As per Note G5 Table 1A, higher allowable stress to be used for gasketed joints where a distortion can cause leakage.

2. I the design of U-Tube Heat Exchanger, with Tube sheet extended as flange using gasket, is it permitted to take higher allowable stress for Tube sheet design, the governing thickness being at the centre of the Tube sheet which is always much greater than at the peripheral edge under gasket and such Tube sheet is clamped between mating Flanges and not in itself a Flange.

3. Is there any code case governing these instructions.

 

[NRP99]

DK44

Note G5 is quite clear. You already got an answer here.

Past long standing practice is to use higher allowables for central portion of the tubesheet and lower allowables for the extended, bolted portion, if a gasket is involved.

If you are still in doubt, you can use smaller allowable and make design more conservative and if deign is not qualifying, as a professional engineer you can suggest to increase the thickness.

You can search code cases here

 

[DK44]

Thank you NRP 99.

1. Request give relevant Code Case reference number. I am not able to find same.

2. As SnTMan kindly advised to use different Allowable stresses for Central thickness and Peripheral Edge thickness, We have to make such calculations manually.

3. Softwares like PV Elite has no such provision?

4. Is such method acceptable to AI for code stamping?

 

[DK44]

Dears,

Is there any Code interpretation covering the subject?