Gasket pressure rating issue
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This post was last edited by lflsedin on 2018-5-4 at 17:34. (1) I still don’t understand what the difference is between gaskets with the same pressure rating but different specifications; for example, for DN100 gaskets, one is PN25 and the other is PN40. Must their outer diameters be different (larger for PN25 and smaller for PN40?), and are their thicknesses also different?
The outer diameters of the DN125PN40 and PN25 valves purchased from our factory are not the same; the PN25 version has a slightly larger diameter than the PN40 version
What type of gasket do you have?
You can take a look at the steel pipe flanges; there are various size specifications for the gaskets used therein
Well, I checked 20610 – there’s no difference in pressure for type B gaskets; as long as the nominal dimensions are the same, the outer diameter will be the same as well. I don’t understand why the outer diameters of the PN25 and PN40 gaskets purchased by our factory are different; the PN25 gaskets are slightly larger than those of PN40. PN40 gaskets can fit into the grooves on the valve flanges, while PN25 gaskets cannot
It might be due to different models; one has an outer ring while the other doesn’t
This post was last edited by sdu*aohu on 2018-3-7 at 11:14. Type B has an inner ring, but the type of flange seal surface also needs to be considered; the RF type has a larger outer diameter than the MFM type. DN125 flanges, PN2.5 and PN4.0; the RF face diameter is 184mm, while that of the MFM type is only 175mm.
The surface differences are shown in the figure below; the attached image is from HG20606-2009 regarding non-metallic gaskets. There are invisible differences, and gaskets with different pressure ratings are suitable for different pressures. Firstly, the nominal pressure of the flanges differs, as does the tightening force of the bolts, which affects the performance of the gaskets