The standard steel flange is a basic part in comparison with the pneumatic ball valve and the supporting steel flange of the pneumatic ball valve. It is widely used in the design of pneumatic ball valve, pneumatic ball valve and its parts (such as manhole, hand hole, sight glass, level gauge, etc.) and process piping design.
National Standard for Steel Pipe Flanges (hereinafter referred to as GB), because it adopts the internationally commonly used piping series (commonly known as British pipes), and at present the domestic production and supply problems have not been completely solved, the design unit and the construction unit are more accustomed to using the HGJ44 ～ 76 - gi Steel Pipe Flanges, Gaskets, Fasteners (hereinafter referred to as HGJ) issued by the Ministry of Chemical Industry And JB/T74 ～ 90-944 Pipe Flanges and Gaskets issued by the Ministry of Machinery (hereinafter referred to as JB/T), these two industry standards commonly known as metric pipes. In this paper, the three standards are compared in detail within the common range, and a comparison table is given. Through this table, the differences between standards can be seen at a glance, which is not only conducive to design selection, but also can avoid the non connection of process piping in technical transformation projects, and is beneficial to improving design quality and efficiency. It is hereby introduced for the reference of equipment and piping designers. 2. Consideration of comparison range (l) The nominal pressure GB includes two series: the first series is PNO.25~4.0MPa, and the second series is PNZ. 0~42.0MPa; The pressure rating of HGJ is PNO. 25~16. OMPa, JB ／ T is PNO 25~20.0MPa, and when PN<4.0MPa, it is completely consistent with the first series of GB. Pneumatic ball valves and pneumatic ball valves of different standards must use matching flanges of the same standard.