Flange pressure rating
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This post was last edited by kww8411 on 2016-2-29 10:49 end
Personally, I think it’s all templates directly copied from certain design institutes. In our company, the pressure of the circulating water in the utility systems is the same, as is the pipe diameter; however, the flange grades differ. In some cases, the valves are rated at 1.6, but the flanges are actually rated at 1.0. Finally, the changes need to be standardized so that they’re all the same; Sigh, sometimes the design isn’t done carefully either.
The difference between 1.0 and 1.6 is not significant; a unified specification facilitates management.
It’s the same with some of the pipe fittings in our company – the allowable pressure is clearly 0.7 MPa at most, yet PN16 flange valves and similar components are used. I guess it’s not because the hydrostatic test is carried out at 1.5 times the design pressure that the pressure on the flanges has to be increased?
For flanges with PN10 and PN16 ratings, all sizes up to DN150 are the same; therefore, sometimes design institutes or designers specify PN16, as this makes the nominal pressure appear higher. Why is the nominal pressure much higher than the actual operating pressure? In some cases, the pressure of the medium in the pipes on-site is only 0.5 MPa, but the flanges chosen are of PN16 grade. This is because, to ensure safe operation, the nominal pressure must be multiplied by a safety factor of 1.5; thus, for a pressure of 0.5 MPa on-site, this value becomes 0.75 MPa after applying the safety factor. Since there is no pressure rating of 0.75 MPa, a rating slightly higher than that, namely 1.0 MPa, is used. For pipe diameters below DN150, designers usually specify 1.6 MPa in the parameter tables. It is well known that for diameters below DN150, PN10 and PN16 have the same performance, but specifying PN16 gives the impression of a higher pressure rating, implying greater safety and better quality. . . .
Small-diameter valves generally have a minimum pressure rating of PN16 or PN25, right?
As long as it is not less than the design pressure, that’s fine
It is related to the operating temperature. The pressure rating of the flange per standards is at normal temperature.