Calculation of tube sheet flanges for DN325 heat exchangers
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Dear experts: The heat exchanger of DN325 is made of seamless steel pipes, with a design pressure of 0.5 MPa for both the tube side and the shell side. PN16, DN300 standard pipe flanges are used – why is the calculation for these flanges not satisfactory? For such small-diameter heat exchangers, how are flanges and end caps generally selected?
This post was last edited by fzujunru on 2018-12-22 at 21:01. Use high-grade HG20615 flanges; generally, the pipe ends require a pressure rating of PN20 or higher, so PN16 is not sufficient for you. Choose EHB type end caps. Additionally, if using wound gaskets, make sure the inner diameter of those with reinforcing rings is not less than 300
The flange calculation fails either under the pre-tensioning condition or under the operating condition; the operator’s applied pressure is not high. If it’s the former issue, it can be resolved by adjusting the material of the bolts.
This is a common situation: even with large-diameter flanges selected according to NB/T47010, there are times when the calculations don’t work out. If you’re concerned, you can thicken the flange to its original size (which makes it a non-standard flange); generally, however, the standard option is chosen directly.
The design temperature and flange material are not specified; it is possible to check the maximum allowable working pressure according to Table 7.0.1-4 of HG/T 20592. If there are no issues, it can be used directly without the need for further calculations.
There’s no need to calculate. Pipe flanges ensure strength by ensuring that the stress during sealing does not exceed the allowable stress of the bolts. According to HG/T20592, simply select the flanges, studs, and gaskets of the corresponding grade.
This post was last edited by Gusikucun on 2018-12-24 at 17:08. Agree with 5#. Make sure to check the maximum allowable operating pressure; for flanges of the same specification within the same grade table but made from different material groups, the applicable pressure ranges vary, so it is necessary to verify this based on the specific material group after making a selection. If that doesn’t work, consider changing the material or upgrading to a higher-grade option; flanges selected according to standards can be exempt from calculation. But it must be done strictly in accordance with the standards