Problems with flange standards
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May I ask: Are the flange standards for American standards the same as those for the petrochemical industry? For example, can ANSI 150LB flanges be connected to flanges of such a large size as those specified in petrochemical standards?
They should be different, right? If they were the same, then wouldn’t they also be called ANSI standards? What other differences are there?
Basically the same; Sinopec, having introduced ethylene plants from abroad in the past, uses ANSI standards. To localize the ethylene production facilities, the ANSI standards were replaced with Sinopec standards; the pressure units were changed from pounds to PN MPa, and the dimensions were changed from inches to millimeters, with the numbers rounded off ； Fully convert it to the ANSI standard. However, individual large-size flange specifications undergo some changes during the conversion process.
The flange standards of the Ministry of Chemical Industry, series HG 20592, are derived from the European DIN standard; HG 20615 corresponds to the flange standards of the American system. Of course, there is no perfect match in terms of large sizes.
In fact, attention should be paid to flange connections in high-pressure and high-temperature environments; however, in low-temperature and low-pressure conditions, gaskets can be used for a sealed connection
SH3406, which is generally compatible with both American and petrochemical standards, adopts ANSI B16.5 and API605 standards. SH3406 is highly interchangeable with ANSI B16.5/API605 in terms of structural dimensions and seal face types, and it can be used in conjunction with pipe fittings that comply with standards such as ANSI, API, and MSS. However, since SH3406 follows China’s material standards rather than American material standards (ASTM), there is a slight difference between the temperature-pressure charts of the two. Therefore, when considering their interchange, it is necessary to pay attention to and verify the allowable values for temperature and pressure corresponding to each.
Of course they are different; the specific dimensions can be found in the relevant flange standards. It can be downloaded from websites such as BidWin, HaohaoXue* Community, and China Gas Separation Equipment Network.
The inner diameter of flanges per ANSI 150LB and SH3406 standards differs by 2 mm, while all other values are the same.
The American standards, petrochemical standards, national standards, as well as HG20615 from the Ministry of Chemical Industry are generally compatible with each other; there may be slight differences, but these do not affect assembly, so they can be used together. However, it’s important to check the specifications carefully!