UHX Applicability
UHX Applicability
(OP)
UHX-10(a) says that for the rules of Part UHX to apply, a tubesheet must be "uniformly perforated over a nominally circular area". I conclude, then, that if a tubesheet is not "uniformly perforated over a nominally circular area", the Tube Requirements of UHX-4(e) are not mandatory. In that case, I am free to analyze the tubesheets as welded flat heads (UG-34) with the tubes acting as stay-rods having strength determined by Appendix A and the cross-sectional characteristics of the tubes.
My question is this: Are there guidelines for what constitutes a "nominally circular area"? Aspect ratio perhaps?
Consider a tubesheet on a 10" ID Shell. If the overall tube pattern was 6" square with a diagonal of roughly 8.5", I might reasonably call this a "nominally circular area". But I would not consider a rectangular area 6" wide x 3" tall to be circular.
Is this something for which I must find an agreement with my AI (and Canadian Inspectors for CRNs)?
My question is this: Are there guidelines for what constitutes a "nominally circular area"? Aspect ratio perhaps?
Consider a tubesheet on a 10" ID Shell. If the overall tube pattern was 6" square with a diagonal of roughly 8.5", I might reasonably call this a "nominally circular area". But I would not consider a rectangular area 6" wide x 3" tall to be circular.
Is this something for which I must find an agreement with my AI (and Canadian Inspectors for CRNs)?





RE: UHX Applicability
For lack of alternatives, Part UHX is routinely applied to these designs. TEMA rules can be used also, but have the same limitation, nominally circular area.
My company builds S&T exchangers for which we use Part UHX (whatever the tubefield looks like), and we also build rectangular air coolers, for which we use UG-34 for tubesheet design, although we do not take staying by the tubes into account.
Never had any kicks about the design method used, however for your case, a visit with your AI and the Canadian juridiction may pay off. Nova Scotia is one thing, Alberta something else altogether.
Regards,
Mike
RE: UHX Applicability
Thanks for guiding me to the No-Tube-in-Window reference. Your feedback is consistent with what my AI says.
I've used UHX on non-circular tube distributions in the past. But lately have found that the tube column bending results (UHX-13.5.9) are driving me to what seems like over-conservative results on larger shell diameters.
I appreciate your input.
Rick
RE: UHX Applicability
Regular readers will know I am not big fan of Part UHX tubesheet design:)
Regards
Mike
RE: UHX Applicability
Who said PED wasn't a trade barrier???
RE: UHX Applicability
Mike
RE: UHX Applicability
RE: UHX Applicability
RE: UHX Applicability
RE: UHX Applicability
Think more in the $150-$200/hr range and you're a little better.
RE: UHX Applicability
Regards,
Mike