ASME VIII-1 Para. UHX-10(c)

[marty007]

I'm working on a heat exchanger design in accordance with ASME VIII-1, and have been posed an interesting question by a reviewer. First off, I have attached a screenshot of our tube layout. This layout was specified by our customer, we did not come up with it...

The reviewer is asking us to address the untubed area at the top of the bundle in our calculations. I believe this is being asked to address paragraph UHX-10(c), which states:
(c) The tubesheet shall be uniformly perforated over a nominally circular area, in either equilateral triangular or square patterns. However, untubed lanes for pass partitions are permitted.

My first question would be, what is a "nominally circular area"?

I have seen many NTIW single segmental heat exchanger designs that include large untubed areas on both the top and bottom windows, where this question has never been asked. Where would you draw the line on these designs to say that it is no longer a "nominally circular area"? Untubed over 1/8th of the tubesheet diameter? 1/4 of the tubesheet diameter?

Has anyone else had to address such a question before, and how would you go about justifying the design?

-Marty

 

[SnTMan]

marty007, wow, bad luck on your reviewer. Even before Part UHX was effective, TEMA rules had limited applicability for "large untubed areas".

These designs are very common and to my knowledge, this particular question as never been addressed, even in the most casual manner. So you either use an accepted method or, I guess, FEA.

To the reviewer, I guess I would try to defend use of Part UHX under U-2(g). And hope fo the best...

Regards,

Mike



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