GB/T 1047-2005 standard stipulates that the nominal diameter of the back pressure valve is only an indication, which is represented by the combination of symbol "DN" and number. The nominal size cannot represent the measured valve diameter value. The actual diameter value of the valve is specified by relevant standards, and the general measured value (unit mm) shall not be less than 95% of the nominal size value. Nominal size is divided into metric system (symbol: DN) and English system (symbol: NPS). National standard valve adopts metric system, American standard valve is English system. The metric DN values are as follows: DN10, DN15, DN20, DN25, DN32, DN50, DN65, DN80, DN100, DN125, DN150, DN250, DN300, DN400, DN450, DN600, DN700, DN800, DN1000, DN1100, DN1200, DN1400, DN1800, DN1800, DN1800, DN1800, DN1800, DN1800, DN2400, DN2600, DN2600, DN2100, DN2400, DN2600, DN2100, DN2400, DN2600, DN2100 DN3000, DN3200, DN3500, DN4000
GB/T 1048-2005 standard, nominal pressure of valve is also a logo, represented by a combination of symbols "PN" and Numbers, nominal pressure can not be applied to calculate the purpose, do not represent the actual measured value of valve, nominal pressure of establishing the purpose is to simplify the number of the specifications of the valve pressure, in the selection, design, manufacturing units and units used are near to the provisions of the data on the principle of the establishment of the nominal size is the same purpose. The nominal pressure is divided into the European system and the American system. China's nominal pressure is to use European system standards. The specifications are as follows:
PN0.1, PN0.6, PN1.0, PN 2.5, PN6, PN10, PN16, PN25, PN40, PN63/64, PN100/110, PN150/160, PN260, PN320, PN420
CLASS: 125LB, 150LB, 300LB, 400LB, 600LB, 900LB, 1500LB, 2000LB, 2500LB, 3500LB, 4500LB
