Valve pressure-temperature rating

Valve pressure - temperature rating

The pressure - temperature rating of the valve is the maximum allowable working pressure expressed in gauge pressure at the specified temperature. When the temperature rises, the maximum allowable working pressure decreases. Pressure - temperature rating data is the main basis for the correct selection of flanges, valves and piping at different operating temperatures and working pressures, as well as basic parameters in engineering design and manufacturing.

Pressure - temperature rating standards for valves, fittings, and flanges have been developed in many countries . The following describes China, the United States, Germany and international standards.

National Standard GB/T9124-2000 "Technical Conditions for Steel Pipe Flanges" refers to the principles and methods for the formulation of pressure and temperature ratings in German DIN2401-1977 and ASME/ANSI B16.5a-1992 standards, using the flanges commonly used in China. Materials, according to the international standard ISO/DIS7005-1-1992 , respectively , the flange pressure - temperature rating applicable to two nominal pressure series ( PN0.25 ~ 4.0MPa , PN2.0 ~ 42.0MPa ) . The standard specifies the maximum allowable pressure of 13 flange materials at 12 nominal pressure levels and an operating temperature of 20 to 530 °C .

In the US standard, the pressure - temperature rating of steel valves is specified in ASME/ANSI B16.5a-1992 and ASME B16.34-1996 ; the pressure - temperature ratings of cast iron valves are in accordance with ANSI B16.1-1989 to B16. .4-1989 , ANSI B16.42-1985 ; pressure - temperature ratings for bronze valves in accordance with ASME/ANSI B16.15a-1992 , ASME B16.24-1991 .

1, U.S. ASME / ANSI specified English units and metric units The two flange sizes B16.5a-1992 series, the list simultaneously applied pressure and temperature rating of the flanges of the two systems.

2 , the United States ANSI B16.42-1985 "nodular cast iron pipe flange and flange pipe fittings" standard specifies the CL150 and CL300 ( PN2.0 and PN5.0MPa ) ductile iron flange pressure - temperature rating in the standard appendix The method for formulating the pressure - temperature class is defined. The basic principle, scope of application, restrictions and procedures are basically the same as those of ASME/ANSI B16.5a-1992 .

3, into the United States ASME B16.34-1996 ASME / ANSI temperature B16.5a-1992 in flanged valves - pressure rating data. The pressure - temperature ratings of flanged valves in this standard are based on ASME/ANSI B16.5a-1992 . This standard lists pressure - temperature rating data sheets for standard-grade valves and butt-welded special-grade valves for flanged and butt welded connections . There are more than 100 kinds of valve materials listed in the standard, which are divided into 27 groups.

The second part of the German standard DIN2401-1977 "Pipeline pressure grade, allowable working pressure of steel and cast iron pipe parts" is a relatively comprehensive pressure - temperature rating standard. Among them, the allowable working pressure of seamless pipes, welded pipes, flanges, valves, fittings and bolts under different materials and different temperature conditions are listed. The standard includes 6 kinds of flange materials, 4 kinds of flanged cast iron valve materials , and 5 kinds of cast steel , all of which are original materials. The steel is carbon steel and low alloy steel, not including stainless steel.

It is clearly stated in the standard that when other materials different from the original material are used, the allowable working pressure is calculated based on the ratio of the strength characteristic value of the applicable material to the strength value of the original material specified in the standard at 20 °C .

The national standard ISO/DIS7005-1-1992 "Ordinary pipe flange" is a combination of the American standard ASME/ANSI B16.5a-1992 and the flange standard of the German pressure standard. Therefore, the pressure - temperature rating standard adopts the method of formulating the flange pressure - temperature rating standard of the United States and Germany and the corresponding data.

The nominal pressure ratings PN0.25 , 1.6 , 1.0 , 2.5 , 4.0MPa in ISO/DIS7005-1-1992 are German flange systems; PN2.5 , 10 , 15 , 25 , 42MPa are British flange systems. The pressure - temperature rating criteria for each system apply only to the flange standards of the respective systems.