Currently, many developed countries in the world have formulated pressure and temperature rating standards for valves, pipe fittings, and flanges. Today we focus on China, the United States, Germany and international standards:
1. Chinese National Standards
The national standard GB/T 9124-2000 “Technical Conditions for Steel Pipe Flanges” refers to the principles and methods for formulating pressure and temperature ratings in the German DIN 2401-1977 and the American ASME/ANSI B16.5a-1992 standards, and uses the commonly used standards in my country Flange materials refer to the international standard ISO/DIS7005-1-1992, and flange pressure-temperature ratings suitable for two nominal pressure series (PN0.25~4.0MPa, PN2.0~42.0MPa) are respectively formulated. The standard stipulates the maximum allowable pressure for 13 flange materials under 12 nominal pressure levels and operating temperatures of 20~530°C.
2. American Standards
In American standards, the pressure-temperature rating of steel valves is in accordance with ASME/ANSI B16.5a-1992 and ASME B16.34-1996; the pressure-temperature rating of cast iron valves is in accordance with ANSI B16.1-1989~B16 .4-1989, ANSI B16.42-1985; the pressure-temperature rating of bronze valves is in accordance with ASME/ANSI B16.15a-1992, ASME B16.24-1991. The American ASME/ANSI B16.5a-1992 stipulates two flange size series in imperial units and metric units, and lists the flange pressure and temperature ratings applicable to the two unit systems. The American ANSI B16.42-1985 “Ductile Iron Pipe Flange and Flange Fittings” standard stipulates CL150 and CL300 (PN2.0 and PN5.0MPa) ductile iron flange pressure-temperature ratings, which are also specified in the standard appendix. The method for formulating pressure-temperature grades, its basic principles, scope of application, limitations and formulating procedures are basically consistent with ASME/ANSI B16.5a-1992.
U.S. ASME B16.34-1996 incorporates the temperature-pressure rating data for flanged valves in ASME/ANSI B16.5a-1992. The pressure-temperature ratings for flange-connected valves in this standard are developed using the method of ASME/ANSI B16.5a-1992. This standard lists pressure-temperature rating data tables for standard-grade valves with flanged and butt-welded connections and special-grade valves with butt-welded connections. There are more than 100 valve materials listed in the standard, divided into 27 groups.
3. German standards
The German standard DIN2401-1977 Part II “Pipe Pressure Levels, Allowable Working Pressures of Steel and Cast Iron Piping Components” is a relatively comprehensive pressure-temperature rating standard. Among them, the allowable working pressures of seamless pipes, welded pipes, flanges, valves, pipe fittings and bolts under different materials and different temperature conditions are listed. The standard includes 6 flange materials, 4 flange-connected cast iron valve materials, and 5 cast steel materials, all of which are original materials. Steel materials are all carbon steel and low alloy steel, stainless steel is not included.
The standard clearly stipulates that when a material different from the original material is used, the allowable working pressure is calculated based on the ratio between the strength property value of the applicable material and the strength value of the original material at 20°C specified in the standard.
4. International standards
The national standard ISO/DIS7005-1-1992 “General Pipe Flange” is a merger of the American standard ASME/ANSI B16.5a-1992 and the German standard flange standard for nominal pressure levels. Therefore, the pressure-temperature rating standard