I have a question regarding flange types; I would like to ask the experts on this forum
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I used to work on custom projects, and I’m here temporarily to handle the design of pump rooms and valve chambers. Our project involves drawing in hot spring water, which has a temperature of around 80°. I previously came across the standard “HGT 20592~20635-2009”, and it seemed that the plate flanges specified in that standard could handle pressures up to 4 MPa (or maybe I misunderstood it). However, the new standard “GBT 9124.1-2019” specifies that PL plate flanges combined with RF raised-face seals can withstand pressures of up to 10 MPa. Initially, for safety reasons, I used WN wafer-type butt weld flanges everywhere; now I want to replace some of them with plate flanges. The reason for this is, firstly, to reduce costs, and secondly, to reduce the size of the valve chambers. Therefore, I would like to ask the professionals: 1. Can a PL plate flange be used at 6.4 MPa? 2. Also, can a PL plate flange be welded directly to a tee? Could there be issues with the bolts not being easy to install in the future? 3. Can PL plate flanges be made with uneven surfaces? (Because the standards mainly involve flat and convex surfaces) Thank you in advance! ! !
A 6.4MPA unit should be able to do PL； When installing PL flanges and fittings, sufficient length of main pipe must be left; otherwise, the bolts may not be able to be removed ； PL flanges seem to not be suitable for use with uneven surfaces; such flanges are generally not employed, unless the pipeline is under high pressure or the medium is highly toxic.
According to GB/T 9119-2010, Table 1 in section 3.1 provides the tables of nominal pressures and nominal size ranges. Since the pressure you intend to use is 6.4 MPa, it is necessary to choose a higher grade; PN63 is no longer sufficient to meet your pressure requirements. Therefore, an RF (convex) flange with PN100 rating should be selected, and its applicable pipe diameter range is DN10 to DN350. Given that the operating temperature is not very high, no temperature correction is required.
Also, can a PL plate flange be welded directly to a tee? Could there be a problem with the bolts not being easy to install later on? ? No, it’s not possible. Yes