Valve pressure, GB is how to convert between the US standard?
We usually use the PN, Class, are a representation of the pressure, the difference is that they represent the pressure to withstand the corresponding reference temperature is different, PN European system refers to the pressure at 120 ℃, and the United States CLass The standard refers to the pressure at 425.5 ° C. So in the project exchange can not be purely for pressure conversion, such as the CLass300 # simply pressure conversion should be 2.1MPa, but if you consider the use of temperature, it corresponds to the pressure increased, according to the temperature of the material pressure The test is equivalent to 5.0MPa.
There are two kinds of valve system: one is the "nominal pressure" system based on the allowable working pressure at normal temperature (100 degrees in our country and 120 degrees in Germany) represented by Germany (including China). One is the "temperature pressure system" represented by the United States, represented by the allowable working pressure at a certain temperature. In the U.S. temperature stress system, all levels except the 150LB are based on a standard of 454 degrees . The 150 psi (150 psi = 1 MPa) 25 # carbon steel valve has a permissible stress of 1 MPa at 260 ° C and a permissible stress greater than 1 MPa at ambient temperature of about 2.0 MPa. Therefore, in general, the nominal pressure grade corresponding to American Standard 150LB is 2.0MPa, the nominal pressure grade corresponding to 300LB is 5.0MPa, and so on.
Therefore, we can not change the nominal pressure and the temperature and pressure level casually according to the pressure transformation formula. PN is a number and the pressure-related code-named, is to provide a convenient reference for a round integer, PN is similar to the pressure equivalent to normal temperature MPa, is the nominal pressure used in domestic valves. The control valve for carbon steel body refers to the maximum allowable working pressure when it is used below 200 ℃. For cast iron body, the maximum working pressure allowed when it is used under 120 ℃. The control valve for stainless steel body means 250 ℃ below the maximum allowable working pressure. When the working temperature increases, the body pressure will be reduced.
American standard valve to indicate the nominal pressure pounds, pounds for the combination of a metal temperature and pressure calculations, he calculated according to ANSI B16.34 standard. The main reason why the pound level and the nominal pressure do not correspond to each other is the difference between the pound level and the nominal temperature. We usually use the software to calculate, but also know how to use the table to check the scale. Japan mainly uses K value to express pressure level. For gas pressure, we generally use "kilogram" mass units (rather than "jin") in China, in kilograms. The corresponding unit of pressure is "kg / cm2", one kilogram of pressure is one kilogram of force acting on a square centimeter. Similarly, corresponding to foreign countries, for gas pressure, the commonly used pressure unit is "psi", the unit is "1 pound / inch2", which is "Pounds per square inch" and the full English name is Pounds per square inch. But it is more common to call its mass unit directly, LB (LB.), the actual LB. Is the aforementioned pound force. All units replaced by metric units can be calculated: 1 psi = 1 pounds / inch2 ≈ 0.068 bar, 1 bar ≈ 14.5 psi ≈ 0.1 MPa, Europe and the United States and other countries used to make the unit of psi. There are two different values ​​for Class 600 and Class 1500 corresponding to the European standard and the American standard, 11 MPa (corresponding to 600 lb.) is defined in the European system as specified in "ISO 7005-1-1992 Steel Flanges"; 10 MPa (corresponding to 600 lb Level) is defined by the American system, which is defined in ASME B16.5. Therefore, it can not be absolutely said that the equivalent of 600 pounds is 11MPa or 10MPa, the provisions of different systems are different.
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