Issues regarding the sealing of 1-inch ball valves with blind flanges
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Currently, many 1-inch ball valves that connect the separators to the level gauges in natural gas stations have internal leaks and cannot be closed properly. As a result, the company plans to discontinue using some of these level gauges. Now, it is necessary to remove both the 1-inch ball valve located behind the separator and the level gauge, and to seal off that area directly using a blind flange attached to the flange on the separator. I have a question: if we purchase blind flanges, for 1-inch four-hole blind flanges, aside from the difference in thickness, are the diameters of blind flanges with pressure ratings of 400, 600, and 900 the same, as well as the sizes of the bolts used for fixing them and the spacing between those bolt holes?
For such low pressure levels, the diameter of flanges and the size of bolt holes below DN80 are not related to the pressure level.
With a blind plate in place, the bolts will definitely need to be longer than before. It’s necessary to determine which standard the flange follows, so as to find the appropriate blind plate; actually, for a one-inch blind plate, it’s sufficient to cut some steel plates to create one
In other words, I just need to tell the material supplier that the blind flanges should be DN25, with four holes, and I need to know how many pieces are required for class 600 and class 900, right? I don’t need to worry about any other parameters; the flanges will definitely fit for use as blind flanges once they’re purchased, is that what it means?
Are domestic valves generally designed to meet American standards?
Refer directly to the standards HG20592~20635-09, namely \"Steel Pipe Flanges, Gaskets, and Fasteners\"
Original poster, pay more attention to standards in the future – everything is based on standards; there are also some non-standard cases, but you can just refer to the standards in such situations
Dude, I called the manufacturer today, and they said that there are slight differences in the screw holes of 1-inch blind flanges of classes 600 and 900. Is that really the case? We have over 50 stations here – what should we do? We can’t possibly measure them all, right?
Of course not. In China, national standards are still used the most; of course, there are also many pipelines equipped with valves that meet American standards
After checking relevant information and visiting the site, it was found that the pressure ratings vary, as do the flange sealing surfaces – there are RE/surface-with-ridges-and-grooves types