Do valve connection flanges need to be distinguished between Series A and B?

Yes, the valve connection flanges need to be distinguished between Series A and B. When selecting the flange for valve connection, it is necessary to ensure that the flange model matches the valve model; this is especially true in the AB series, where there are significant differences between the flange models. Improper connection can affect the performance of the valve. Therefore, when selecting valve connection flanges, the appropriate AB series flanges should be chosen based on the specific model of the valve for connection purposes. -

The AB series of flanges is determined by the outer diameter of the pipe (metric or imperial), not by the valve; valves do not have an AB series.

During the initial research, I found that American standard large flanges do indeed come in AB series. It is clearly stated that the others have not been seen yet.

The last edit to this post was made by Siege Lion_peyWD on 2023-3-13 at 17:15. Flanges are divided into A and B series; type B is suitable for national standards, while type A is suitable for American standards. The domestic petrochemical industry uses type A

For PN series valves, there is no distinction between Series A and Series B, as the flange sizes are the same. For valves in the class series, only flanges of the corresponding pound rating can be used. The sizes of pound-class flanges and PN series flanges are still different.

For the AB distinction mentioned by the original poster, it can be temporarily understood as a classification based on the AB size series; this distinction depends not on the valve itself but rather on the diameter of the inlet and outlet pipes connected to the valve. If the pipes belong to series A, then A-series flanges must be used, and if they belong to series B, then B-series flanges are required. This has little to do with the flanges on the valve body itself, and generally, the flanges on valve bodies produced by valve manufacturers are of series B. Thus, the appropriate flanges can be used to connect the pipes accordingly. If it’s AB flanges from the American system, then it’s different, as one type is heavy-duty and the other is light-duty; the outer diameter and center distance of these two types of flanges are different, so in the American system, A must be paired with A and B must be paired with B.

The 8th floor answer is correct. Let me add more: 1. The pipes and flanges in the PN series come in A/B size variants, but the dimensions of their sealing surfaces are the same; therefore, valves do not have A/B series distinctions — HG20592； 2. CLASS series: For pipelines, flanges, and valves of DN600 and below, there is only one size series – HG20615 ； Flanges with a large diameter of DN650 and above are divided into Series A and B; the dimensions of their sealing surfaces differ, which means that the valves connected to them also come in Series A and B – according to HG20623.

The analysis is correct, but there’s one additional point: the dimensions of the sealing surfaces in the PN series vary. Since the inner diameter changes after the AB modification, the dimensions of the sealing surfaces also differ slightly

Flanges are divided into A and B types; they are mainly used for mating with pipes, with type A mating with type B, and there is a misalignment between them

The AB series differs only in pipe diameter; for example, for DN100, the diameters are 114 and 108. But the flange sealing surfaces and center distances have the same dimensions. So, if they are matching valves, there is no need to distinguish between A and B; whereas if they are flanges intended for use with pipes, then flanges of the A and B series need to be selected according to the pipe diameter category