Tubesheet Calcs 1

[MrBTU]

Hello All,
We are submitting a shell and tube heat exchanger design for PED for import into the EU. As such, it is designed to ASME Sect VIII Div 1, and submitted to a Notified Body for review. The tube pattern is such that the tubesheets do not fall under the scope of UHX (large untubed areas and non-circular pattern).... therefore, we fall to U-2(g). Our first fall back would be to submit TEMA calcs, but the reviewer correctly says we cannot submit TEMA calcs either because RCB 7-11(3) exempts these tubesheets. So... short of an FEA, what can we submit to justify these tubesheets? Does anyone have calcs that cover tubesheets with untubed areas?

 

[SnTMan]

MrBTU, TEMA calculations were formerly used regularly and ASME calculations are now used regularly for this type of tube pattern although, as you note, it does not fit within the scope of either, strictly speaking.

However, you have to satisfy your reviewer, no way around that. Can the reviewer suggest other analysis perhaps? FEA may be your only option.

Regards,

Mike

 

[MrBTU]

SnTMan - Agreed, and I have asked the reviewer what he receives and accepts from European manufacturers.

 

[SnTMan]

MrBTU, good luck, I would be interested in knowing how you resolve this.

Regards,

Mike

 

[MrBTU]

Interestingly enough, I have a letter from the same Notified Body from 2004 that states that TEMA calcs are an acceptable alternative for these types of tubesheets under U-2(g). I scanned this email and sent it to them yesterday. It gets murky because the people I deal with here in the states are not the people doing the PED reviews, they are over in France. Who reports to whom and which group wins will be interesting to watch. At the end of the day, PED is an exclusionary spec that is meant as a trade barrier, so the European group can delay and delay, just like some of our friends from a certain Canadian province.... but I digress..... don't get me started..... Why don't all of the Canadian Provinces get together and do what Saskatchewan did - tell the end user to file the U-1 and they get a CRN - easy, quick, no hassle, and safe.... but no.....

 

[carthago]

..New UHX calculations methodology in ASME VIII should at the end match the EN 13445 -Part 3 of the european code ..which is the same as for instance the french Code CODAP...

Try a search on Google and find = francis OSWEILLER.
see also attachment.
This defines the assumptions and backround of UHX

This gentlman is a a " gourou" in tubular heat exchanger design and he works for ASME + EN + Codap
his papers are the basis for UHX design and also for EN

In his papers he defines analitically the boundaries between th former TEMA design and UHX ( based on the stiffness factor Xa..)

Again dowload his free paper and you probably find a way I hope