What is the maximum allowable operating pressure for PN25 pipes?
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For pipe 304, with a maximum operating pressure of 2.4 MPa and an operating temperature of around 50°C, can PN25 be used? My question is: referring to the specifications for steel pipe flanges, it states that the allowable pressure for PN25 is lower than 2.4 MPa. So it definitely won’t work. But here I only have pipes, no flanges – everything is welded or threaded. So would that work then?
Flanges can be classified according to PN; pipes that are not classified by PN can be classified using the Sch pipe designation, which determines the different wall thicknesses and the pressures they can withstand.
The structural dimensions of the standard flange have been determined, so the maximum allowable operating pressure can be specified； The wall thickness of the steel pipe is determined by design, as long as it meets the strength requirements.
At least one level higher, to leave a safety margin
If the HG/T20592 flange standard is adopted, the maximum allowable operating pressure for the corresponding material at the design temperature can be found. That is, the temperature-pressure curve. If there is no corresponding temperature in the table, it is determined using interpolation.
Since you’re not using flanges, what’s the impact of upgrading to a higher level? PN40 should also not affect the pipe wall thickness.
For pipes, check the thickness; for flanges, check PN and CLASS
Simple pipes without flanges do not involve PN. There is a maximum operating pressure and operating temperature; based on these, the wall thickness can be calculated. What’s lacking now is information regarding the corrosiveness of the medium. Check GB20801, which provides formulas for calculating pipe thicknesses – once you’ve seen that, you won’t be confused anymore!
If there are no flanges, then what is the meaning of PN?