National standard valve nominal pressure and American standard valve pressure there are the following differences:

◆ Pressure expression method and unit: the national standard valve pressure rating unit is MPa (MPA), the American standard valve pressure rating unit is LB (pound class) 2. For example, the nominal pressure of the national standard valve may be marked as 1.6MPa, 2.5MPa, etc., and the American standard valve is marked as 150LB, 300LB, etc.

◆ Pressure corresponding to reference temperature: in the national standard system, PN refers to the corresponding pressure at 120℃. In the US standard system, except for 150LB, which is based on 260 ° C, the other levels are based on 454 ° C. Due to the different reference temperature, the allowable pressure of the US standard valve at room temperature is greatly different from the value obtained by pressure conversion. For example, 150 pound grade 25 carbon steel valve at 260 ° C allowable pressure is 1.0MPa, and at room temperature allowable pressure is about 2.0MPa, so it is generally believed that the nominal pressure level of the US standard 150LB is 2.0MPa, and the nominal pressure level of 300LB is 5.0MPa.

◆ Standard specifications and application range: National standard valves follow the relevant Chinese standards, such as GB/T and other standard series, and are widely used in all kinds of engineering construction and industrial fields in China. American standard valves are designed, manufactured and tested according to the relevant standards of the United States, such as ASME B16.34, API and other standards, and are widely used in engineering and industrial projects in the world, especially in Europe and the United States. In addition, in the 600 pound class and 1500 pound class, the European and American standards have different regulations. For example, 11MPa (for the 600 lb class) is the European system requirement, and 10MPa (for the 600 lb class) is the American system requirement in ISO 7005-1 Steel Flanges, which is specified in ASME B16.5.

In actual use, the appropriate valve pressure grade and standard should be selected according to the specific engineering requirements, the design parameters of the pipeline system and the standard specifications of the region, and can not be simply converted and mixed based on the pressure value.