What are ASME 2019 Changes for Code Case 2901?
Code Case 2901 (CC 2901) has now been incorporated into UG-44.
This adds consideration for tensile forces and overturning moments for the selection of rated flanges. It’s limited to Weld Neck flanges, but works for B16.5 and B16.47 weld necks. The calculation uses the pressure-temperature rating from B16.5 and B16.47; but also requires the designer to know the gasket reaction diameter in order to consider the external loads.
These changes move CC 2901 into the proper code book, which makes it easier for manufacturers to use in their designs.
How Does Gasket Reaction Factor Into Flange Selection?
Historically, choosing the rated flange class came down to pressure, temperature and the material group. Using this same method, you can now consider two external loads along with the pressure and compare it with the pressure rating in an evaluation formula.
It’s important to state again, though, that at the time of flange selection, the designer will need to know the gasket reaction as opposed to only knowing the pressure and temperature.
To mitigate these problems and avoid thickening your tube sheet, use Ap and Cp. You can also use your operating temperatures for operating cases where thermal loads are.
If these solutions don’t work, a final solution could be thickening the tube sheet.
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