Dear all
We are having a U bundle exchanger with channel side integral with tubesheet; Tubesheet is with a lip and hemispherical head is welded to the lip.
4-18-4 para c of of ASME Section VIII Div2 imposes a condition that the head shall be directly welded to tubesheet and no cylindrical shell shall be welded in between; Similar condition exists in ASME Sec VIII Div1 (UHX - 10 b)
My personal interpretation is the lip of short length (machined from tubesheet) is not a cylinder and the intention of code is not to weld a separate cylindrical shell in between. Hence welding the hemispherial dished end without any cut back to the lip of tubesheet should be OK.
The job is not code stamped ; We would like to have your expert opinion on the issue please
Thanking You and with regards

Dear Mr. R. Srinivasan

According to me, you can weld hemispherical dish directly with tubesheet provided you meet the requirement of UHX-12.5 Step 10,
"For Configurations a, e and f: A cylindrical channel shall have a uniform thickness of tc for a minimum length of 1.8*sqrt(Dc*tc) adjacent to the tubesheet".

The configuration explained by you, tubesheet integral with channel is configuration 'e' as per Fig. UHX-12.1.

If you provide lip length of tubesheet = minimum length required as above, there may not be any problem.

Dear Mr.Purav
Thank You. I agree with you. But I have not explained my case properly earlier;
1. My case is a tubesheet integral with channel and shell side (similar to Fig.uhx-10(b) in section VIII Div.1)

2.My design code is Sec VIII Div.2 which puts condition (para 4.18.4 (c) which is same as condition in para 10(b) of Sec VIII Div.1

3. We are not able to insert a cylinder of 1.8*sqrt(Dc*tc) due to some other constraint

4.Due to presence of a short lip of 50 to 100 mm (cylinder) between dished end and tubesheet, analysis by part5 of VIII Div2 is mandatory.

5.Is it adequate to check dished end stress (thickness adequacy) alone by analysis or one has to check all parts including tubesheet

Expecting expert opinion / suggestions from all

Thanking You and With regards

Dear Mr. R. Srinivasan,

As per my knowledge of code, guideline is available to check stresses for integral shell/channel, but if you want to check integral hemispherical dish stresses, formulaes are not available.

Code specify guideline for tubesheet analysis considering it as simply supported where the effect of the stiffness of the integral channel and/or shell is not considered.

Here you need not have to evaluate integral shell/channel stresses.

So you can try this option.