- "Nominal pressure" commonly used system - PN vs Class
For the valve "nominal pressure" commonly used marking system, the European standard system (PN) is represented by Germany at room temperature (120 ℃) of the permissible working pressure as the basis for the "nominal pressure" system, mostly used in ISO, DIN, EN, BS standards. Class American Standard system (Class) is represented by the United States to a certain temperature under the permissible working pressure as a representative of the "temperature-pressure" system, mostly used in AMSE and other standards.
American Standard valves in the Class series (i.e., pounds), are a combination of temperature and pressure for a particular metal, according to ASME B16.34 calculation results. Due to the poundage and the nominal pressure of the temperature benchmark being different, the poundage and the nominal pressure are not a one-to-one correspondence, so in engineering, conversion can not simply be pressure conversion. For example, Class300 simply with the pressure conversion should be 2.1MPa, but if you take into account the use of temperature, the corresponding pressure will rise, according to the material temperature and pressure test to determine the equivalent of 5.0MPa. At the same time, in the U.S. "Temperature - Pressure" system, the other levels of 454 ° C as a benchmark, while the Class150 is 260 ° C as a benchmark. Class150 is based on 260 ℃. Class150 of 25 carbon steel valves at 260 ℃, the permissible stress of 1MPa, while the permissible stress at room temperature is much larger than 1MPa, about 2.0MPa. Therefore, you can not just follow the pressure change formula to change the nominal pressure temperature and pressure levels.
What should be more concerned is that there are two different values in Class600 and Class1500 corresponding to the European Standard and American Standard. Take Class600 as an example, in the European standard system, the 10MPa stipulated in ISO 7005-1:2011 corresponds to Class600; in the American standard system, the 11MPa stipulated in ASME B16.5 corresponds to Class600, so we can't say that Class600 corresponds to 11MPa or 10MPa, and the stipulations of different systems are different. different systems are different.
- The common unit of gas pressure and conversion relationship
For the pressure of the gas, China generally more commonly used its mass unit "kilogram" to describe (rather than "jin"), the unit kg. Its corresponding pressure unit is "kg/cm2 ", a kilogram of pressure is a kilogram of force acting on a square centimeter, converted to 1kg/cm2 = 0.98 bar ≈ 0.1MPa. Similarly, in foreign countries, for the pressure of the gas, the commonly used unit of pressure is "psi", the units are "1pound/inch2", that is, "pounds/square inch", the full name of the English Pounds per square inch. but more commonly used is to directly call the unit of mass, that is, pounds (LB.). All units into metric units can be derived: 1psi = 1pound/inch2 ≈ 0.068bar, 1bar ≈ 14.5psi ≈ 0.1MPa.
