We have to hydrotesting outside of the bundle of a U type conf. d (gasketed both sides) heat exchanger's tubesheet, which, for this purpose is extended as a flange.The tubesheet has classic TEMA male and female body flanges.
The problem is that tubesheet male groove for gasket place is placed radially appr. 5mm inside the inner edge of the bolts, so, if anyone wants to bolt the tubesheet to shell or to the channel for hydrotest, the nuts to fall in to the interface between the grooved and the ungrooved area of the tubesheet, which have different thickness.Additional,in the ungrooved area they fall on to the spiral serrated area. I wonder how this technical problem can be solved, understanding that distance between gasket circle and bolt circle must be small enough for reducing of moment level arm and allowing of using of thinner flanges, so I could not say that this configuration is technical wrong.
Another issue is that the stress to the tubesheet at hydrotest to the channel are reaching appr. 3700bar, which in many cases is almost material yield strenght. This value have been calculated from UHX chapter for U -type conf d, by adding into the Pt the eq. bolting pressure 6.2M/G3.Can anyone advise if these stresses are acceptable for hydrotest.