Regarding the regulations, metal wound gaskets should be used with butt-welded flanges and flanges of PN20 or higher
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This post was last edited by xunzaonvdun on 2018-6-27 at 10:18. For low-pressure steam pipelines, I originally designed them to use socket weld flanges, PN16, with metal wound gaskets as the sealing elements. While reviewing something for someone else, I came across 2 standards: So, what is the basis behind these two standards? If metal wound gaskets are used, then welding at PN25 must be the standard approach, and butt-welded flanges of PN16 would have to be phased out. Or do we have to return the gasket and choose a non-metallic one instead?
3.0.2 Point 9 states that flange types with higher rigidity, such as wafer butt-welded flanges, should be selected. Pay attention to the word “wait”. In Table P226, flat weld flanges with necks can also use wound gaskets. For non-metallic gaskets, it is also a good idea to choose RSB.
I don’t think the word “wait” includes flanges with a neck for butt welding; the P226 specification is also quite strange. The pressure for spiral gaskets is 16–160 (while the column for pressure of non-metallic gaskets states ≤16). Does that mean 16 is not included? If not, then RSB has to be chosen……
Metal wound gaskets are commonly used in conjunction with butt-welded connections (not with socket welds), and are primarily applied in conditions of high temperature, high pressure, or both. In \"American flanges\", they are commonly used in pressure classes of PN10.0 (in some cases), PN15.0, PN25.0, and PN42.0 MPa. In “European flanges”, PN10.0, PN16.0, PN25.0, PN32.0, and PN4200 are commonly used. Full-flat sealing surface of metal wound gaskets: It is often used in combination with the flat welding method for applications under relatively mild operating conditions (PNg1.0); it is commonly used on cast iron flanges or steel flanges connected to cast iron. Raised surface sealing surface: This is the most widely used type, and it is often used in conjunction with the butt welding and socket welding methods. In “American-style flanges”, it is commonly used for pressure grades of PN2.0, PN5.0, and some PN10.0 MPa grades; in “European-style flanges”, it is commonly used for pressure grades of PN1.6 and PN2.5 MPa.
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May I ask a question? How should one check in practical work whether this roughness is within a certain range?
There are standards; check the flange standard you are using. Is it the flange standard and testing method you are using, which allows the use of a roughness meter or roughness standard blocks?
Flat-face flanges and socket-weld flanges do not have high stiffness compared to spiral-wound gaskets (relatively speaking); in contrast, necked butt-weld flanges have sufficient stiffness. Conversely, using a flange with a neck and wound gasket as the standard, butt-welded flanges or socket-welded flanges appear to have too low stiffness. At this time, this requirement was put forward to ensure sealing. Therefore, if the original poster were to take a look at SEI’s European standard classification table (for illustrative purposes only; such information is easily available online), it can be seen that for DN40 and below with a PN16 rating, flanges requiring gaskets are those of PN25 grade, which is also in line with the requirements of the HG flange standards.