2022-11-21
What is the difference between the National Standard Valve Pressure and the American Standard valve pressure
The nominal pressure is an important parameter of the valve, which is usually represented by the letters PN. The pressure system of the valve is commonly divided into two categories: the National Standard Pressure System and the American Standard Pressure System. What are the differences between them? How to make a simple conversion? This detailed introduction will help the valve users better understand.
The National Standard System PN refers to the corresponding pressure at 120 ℃, while the American Standard Class refers to the corresponding pressure at 425.5 ℃ (except that 150LB is based on 260 ℃, all others are based on 454 ℃). The allowable stress of No. 25 carbon steel valve of 150lb class (150psi=1MPa) is 1MPa at 260 ℃, while the allowable stress at normal temperature is much larger than 1MPa, about 2.0MPa. Therefore, generally speaking, the nominal pressure class corresponding to 150LB in American Standard is 2.0MPa, and the nominal pressure class corresponding to 300LB is 5.0MPa. Therefore, in engineering interchange, it is not allowed to simply convert the pressure. For example, in case of only convert the pressure and regardless of temperature the pressure conversion of Class 300LB should be 2.1MPa, but if the temperature is considered, the corresponding pressure will