We usually use Pn, CLass, are a way of pressure, the difference is that they represent the pressure under the corresponding reference temperature is different, Pn European system refers to the corresponding pressure at 120℃, while the American standard refers to the corresponding pressure at 425.5℃. Therefore, in the engineering exchange can not only simply for pressure conversion, such as CLass300# simply with pressure conversion should be 2.1 Mpa, but if you take into account the use of temperature, its corresponding pressure will rise, according to the material temperature pressure test is equivalent to 5.0 Mpa.
There are two kinds of valve system: one is Germany (including China) as the representative of the normal temperature (China is 100 degrees, Germany is 120 degrees) allowable working pressure as the benchmark of the “nominal pressure” system. One is the “temperature pressure system” represented by the United States, which is based on the allowable operating pressure at a certain temperature. In the temperature pressure system of the United States, all levels are based on 454 degrees except 150LB based on 260 degrees. The 150 lb (150psi=1MPa) Class 25 carbon steel valve has an allowable stress of 1MPa at 260 degrees, but the allowable stress at room temperature is much greater than that, approximately 2.0MPa.
Therefore, it is generally said that the nominal pressure level corresponding to the American Standard 150LB is 2.0MPa, the nominal pressure level corresponding to the 300LB is 5.0MPa, and so on. Therefore, the nominal pressure and temperature pressure grade cannot be changed according to the pressure transformation formula. Pn is a numerical representation of pressure-related code, is to provide a convenient circular number for reference, Pn is approximately equivalent to the normal temperature pressure Mpa number, is usually used in the nominal pressure of domestic valves.
For the control valve of carbon steel valve body, refers to the maximum allowable working pressure when applied below 200℃; For cast iron body, the maximum allowable working pressure for service below 120 ° C; For control valves with stainless steel bodies, maximum allowable operating pressure for service below 250 ° C. When the operating temperature increases, the pressure resistance of the valve body will be reduced. American standard valves express nominal pressure in pound class, which is a calculation of the binding temperature and pressure of a metal according to ANSIB16.34. The main reason why pound grade and nominal pressure are not one – to – one correspondence is that pound grade and nominal pressure have different temperature datum.
We usually use software to calculate, but it is also important to know how to use tables to look up the weight grades. In Japan, the main value of K is used to indicate the pressure level. For gas pressure, in China, we generally use the mass unit “kg” (rather than “jin”), the unit of kg. The unit of pressure is kilograms per centimeter 2, and one kilogram of pressure is one kilogram of force acting on one square centimeter. Similarly, corresponding to foreign, for the pressure of gas, the commonly used pressure unit is “psi”, the unit is “1pound/inch2″, is “Pounds per square inch”, the English full name is Pounds per square inch.
But it’s more commonly referred to as the unit of mass, or LB., which is actually LB. That’s the pound force. All the units into metric units can be worked out: 1psi=1 pound/Inch2 ≈0.068bar, 1bar≈14.5psi≈0.1MPa, Europe and the United States and other countries used to use psi as a unit. In the Class600 and Class1500 corresponding to the European standard and the United States standard have two different values, 11MPa (corresponding to the class of 600 pounds) is the European system provisions, this is in the “ISO7005-1-1992 Steel Flanges” inside the provisions; 10MPa (corresponding to class 600 pounds) is the American system regulation, which is stipulated in ASMEB16.5. Therefore, it cannot be absolutely said that the corresponding class of 600 pounds is 11MPa or 10MPa, and the provisions of different systems are different.
Valve system mainly has 2 kinds: one is Germany (including China) as the representative to the normal temperature (China is 100 degrees, Germany is 120 degrees) allowable working pressure as the benchmark of the “nominal pressure” system. One is the “temperature pressure” system represented by the United States, which is based on the allowable working pressure at a certain temperature. In the United States, the temperature pressure system is based on 454 degrees except for 150LB based on 260 degrees.
For example, the 150LB. # 25 carbon steel valve has an allowable stress of 1MPa at 260 degrees, while the allowable stress at room temperature is much greater than that, about 2.0MPa. Therefore, it is generally said that the nominal pressure level corresponding to the American Standard 150LB is 2.0MPa, the nominal pressure level corresponding to the 300LB is 5.0MPa, and so on. Therefore, the nominal pressure and temperature pressure grade cannot be changed according to the pressure transformation formula.
Post time: Mar-24-2021