Differential Design of Fixed Flanged Tubesheets ( Fig. UHX-12.1(e) )

[Ganfoss2]

Differential design of tubesheets (P.Shell - P.Channel) allow the reduce in thk of tubesheets.

With a TEMA HIGH PRESSURE Exchanger with a Shell Side flanged and the Channel Side Integral with the Channel Barrels (Welded Joint) as stated in Fig. UHX-12.1(e), the differential design may lead to a sensible tubesheet thickness reduction taking in account the moment due to the Bolt Loads (M = W x hG)?

Assume: P.Shell = 1.50 x P.Channel, same Gaskets Types (m, Y) and Dimensions (diam. G and width N) and PRESSURE CASE (factor "m") govern the design of the Flanged Joint, therefore I have to assure a minimum load on the gasket calculate by: m x P.Shell.

I have to desigh the flanged joint between teh tubesheet and the Shell Barrel for the FULL PRESSURE at SHELL SIDE and not for the DIFFERENTIAL PRESSURE (P.Shell-P.Channel) andtehrefore W of Bolt Load is evaluated takingin account the full pressure at shell side!

Is this correct?

Many Thanks to all.

 

[gr2vessels]

Ganfoss2,
The design based on differential pressure is not a feature granted to you by the ASME code for your convenience. It is a responsible decision made by the exchanger designer or by the purchaser, based on actual operating conditions and other safety and process requirements.
If your load case seems to be UHX-12.4(a)(2) Loading Case 2: Shell side pressure Ps acting only (Pt=0), then Clause UHX-9.1 requires..."The required thickness of the extended portion of the tubesheet may differ from that required for the interior of the tubesheet as calculated in UHX-12, UHX-13, or UHX-14."
Hence, according to UHX-9.4(c) The thickness hr shall be calculated for both operating and gasket seating onditions, and the greater of the two values shall be used. For operating conditions, the values of S at the design temperature and W from eq. (3) of 2-5(e) shall be used.
However, if your load case is UHX-12.4(a)(3), then Ps shall be the shell side design pressure and Pt shall be Ps less the differential design pressure. Note however, the checking for the hydrotest condition with no pressure on the tubeside!
Howzat,
gr2vessels