Design tubesheet thickness UHX hydrotest condition

[Ehiman1]

Good evening,
I was checking the tubesheet thickness of BEM heat exchanger and using ASME VIII div.1 with UHX for fixed tubesheets I saw that Hydrotest condition designs tubesheet thickness!
In hydrotest I have a thickness of 100 mm, insteaf of 80 mm in design/operating condition.
I have a stress of 400 MPa due to bending moment and 40 Mpa due to axial load.
The sum of axial load plus bending moment exceeds the maximum allowable in hydrotest condition.
Is it possible consider hydrotest condition as per design tubesheet thickness instead of design condition?

Many thanks

 

[SnTMan]

extragol1A, I assume your axiual load is at hydro. What is the source? There should be no axial load due to differentisl thermal expansion. Allowable stresses at hydro may be higher than allowable at design conditions.

You may need to check your inputs.

Regards,

Mike

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

 

[Ehiman1]

Yes, allowable are higher and I am doing calculation by Compress.
Input data are correct, I Checked again. I can't understand why Hydrotest condition is more restrictive than design..
In my opinion bending stress shouldn't be a problem because section can be distribute the stress.

 

[SnTMan]

Well, all one can say, based on available info, is that you need to determine what the software is doing.

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

 

[r6155]

I do the calculations by hand or with my own calculation programs. I don't trust other programs.

Regards

 

[SnTMan]

r6155, do you often do Part UHX calculations by hand? If so, you have my respect.

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

 

[r6155]

SnTman: My last calculation of fixed tubesheet was 40 years ago, more or less, with my own computer program in a desk computer. Obviuosly checking the program by hand calculations.
Today this work is not for me. I leave it for young engineers
Thank you.

Regards

 

[SnTMan]

r6155, right with you there

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

 

[marty007]

Yep... when I first started in this industry my mentor/boss made a rule that whenever I used a code rule for the first time I was not allowed to use PV software. I was then required to run it through the PV software to check my hand-calcs. Only then could I use PV software for future jobs, having learned how it worked. Part UHX was painful, but I appreciate having gone through it in detail at least once by hand...

 

[SnTMan]

marty007, although I have spent more hours poring over Part UHX than bears thinking about I never did any significant portion by hand, and I was not and am not convinced my skills at mathematics are up to it.

My hat's off to you

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

 

[TGS4]

I would be very surprised that the test condition governs the thickness. That is not the intent of the Code.