Parameters of the valve

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Section 1: Nominal Diameter The nominal diameter DN is a numerical value that represents the size of all piping fittings in a piping system, serving to distinguish them from those components whose dimensions are indicated by threads or outer diameter. The nominal diameter is a rounded figure used for reference, and it is not exactly identical to the actual processed dimension. The nominal diameter is indicated by the letter “DN” followed by a number. For example, a nominal diameter of 250 mm should be marked as DN250 mm. Section 2: Nominal Pressure The nominal pressure PN is a numerical code related to pressure, serving as a convenient round integer for reference. All pipeline fittings with the same nominal diameter indicated by the same nominal pressure PN value have the same connection dimensions appropriate to their end connection type. In our country, when nominal pressure is involved, the unit of measurement is usually specified for clarity, denoted as “MPA”. In countries such as the UK and the US, although the concept of nominal pressure is now included in relevant standards, the imperial unit Class is still used in practice. Due to the different temperature references for nominal pressure and pressure classes, there is no strict correspondence between the two. The approximate correspondence between the two is shown in the table. Japanese standards feature a “K” grade system, such as 10K, 20K, 40K, etc. The concept of this pressure level is the same as that in the imperial pressure scale, but the measurement units are in the metric system. Section 3: Pressure-Temperature Ratings The pressure-temperature rating of a valve is the maximum allowable operating pressure, expressed in gauge pressure, at a specified temperature. As the temperature rises, the maximum allowable operating pressure decreases accordingly. Pressure-temperature rating data serve as the primary basis for selecting flanges, valves, and pipe fittings appropriately under different operating temperatures and pressures; they are also fundamental parameters in engineering design and manufacturing. The pressure-temperature ratings for various materials are provided in Chapter 4; standards for the pressure-temperature ratings of valves, fittings, and flanges have been established for many of them. I. American Standards: Under American standards, the pressure-temperature ratings for steel valves are specified in accordance with ASME/ANSI B16.5a-1992 and ASME B16.34-1996 ； The pressure-temperature ratings for cast iron valves are specified in ANSI B16.1-1989~B16.4-1989 and ANSI B16.42-1985; the pressure-temperature ratings for bronze valves are specified in ASME/ANSI B16.15a-1992 and ASME B16.24-1991. 1) The American standard ASME/ANSI B16.5a-1992 specifies two flange size series, one in imperial units and the other in metric units, and it also lists the pressure and temperature ratings for flanges applicable to each of these unit systems. The method for determining the pressure-temperature ratings in imperial units is given in Appendix D of this standard. 2) The American standard ANSI B16.42-1985 \"Flanges for ductile iron pipes and flanged pipe fittings\" specifies the pressure-temperature ratings for CL150 and CL300 ductile iron flanges. The appendix to this standard outlines the method for determining these pressure-temperature grades; its basic principles, scope of application, limitations, and procedures are essentially consistent with those outlined in ASME/ANSI B16.5a-1992. 3) The American standard ASME B16.34-1966 incorporates the temperature-pressure rating data for flanged valves from ASME/ANSI B16.5a-1992. The pressure-temperature ratings for flanged valves in this standard adopt the methodology established in ASME/ANSI B16.5a-1992. This standard provides a pressure-temperature rating table for standard-class valves with flange connections and weld connections, as well as for special-class valves with weld connections. There are over 100 types of valve materials listed in the standards, which are divided into 27 groups. II. German standards: Volume 2 of the German standard DIN 2401-1977, titled \"Pressure classes of pipes and allowable operating pressures for steel and cast iron pipe fittings,\" is a relatively comprehensive standard for pressure-temperature ratings. It lists the allowable operating pressures of seamless pipes, welded pipes, flanges, valves, pipe fittings, and bolts under different materials and temperature conditions. This standard includes 6 types of flange materials, 4 types of materials for cast-iron valves with flange connections, 5 types of cast steel, and 5 types of forged steel; all of these are base materials. The steels are all carbon steel and low-alloy steel; stainless steel is not included. The standard specifies that when other materials different from the original material are used, the allowable operating pressure is calculated based on the ratio of the strength characteristic value of the material being used to the strength value of the original material specified in the standard at 20°C. The pressure-temperature ratings for stainless steel materials are further specified in ISO/DIS 70651 \"Steel Flanges\". III. Former Soviet Union standards: The former Soviet Union standard TOCT356-1980 \"Series of nominal pressures, test pressures, and operating pressures for valves and piping fittings\" fully comply with the CMEA standards. In the former Soviet standards, materials were classified into groups. In this standard, the maximum allowable operating pressure values below 200°C are considered to be the operating pressure at room temperature, and are equal to the nominal pressure. IV. International Standards The international standard ISO/DIS 7005-1-1992 \"Plain Pipe Flanges\" combines the American standard ASME/ANSI B 16.5a-1992 with the flange standards for nominal pressure classes in German standards. Therefore, the pressure-temperature rating standards also adopt, respectively, the methods for establishing flange pressure-temperature rating standards and the corresponding data from the United States and Germany. The nominal pressure classes PN0.25, 0.6, 1.0, 1.6, 2.5, 4.0 MPa specified in ISO/DIS7005-1-1992 belong to the German flange system ； PN2.5, 10, 15, 25, 42 MPa belong to the American flange system. The pressure-temperature rating standards for each system apply only to the flange standards of that respective system. V. China’s **standard** GB/T 9124-2000 (Appendix A), “Technical Requirements for Steel Pipe Flanges,” draws on the principles and methods used in determining pressure and temperature ratings specified in Germany’s DIN 2401-1977 and the United States’ ASME/ANSI B 16.5a-1992 standards. By utilizing the flange materials commonly used in China and referring to the international standard ISO/DIS 7005-1-1992, pressure-temperature ratings for flanges suitable for two nominal pressure ranges (PN0.25–4.0 MPa, PN2.0–42.0 MPa) were established. The standards specify the maximum allowable operating pressure for 13 flange materials at 12 nominal pressure grades, at operating temperatures ranging from 20 to 530°C. Section 4: Structural Length of Valves I. Data from China 1. Basic series of structural lengths – The basic series for the structural length of valves with flange connections. 2. Structural length of gate valves 3. Structural length of globe valves, check valves, and throttle valves 4. Structural length of ball valves 5. Structural length of butterfly valves 6. Structural length of diaphragm valves 7. Structural length of plug valves 8. Structural length of steam traps 9. Structural length of pressure relief valves 10. Structural length of safety valves 11. Tolerances for the structural length of valves 12. Structural length of valves with butt weld connections 13. Structural length of valves with flange connections 14. Structural length of valves with internal thread connections 15. Structural length of valves with external thread connections II. American data 1. American ASME B16.10-1992 standard: The American ASME B16.10-1992 standard applies to valves with flange ends and butt weld ends, but not to valves with socket weld ends. III. British data: The British standard BS2080-1989 specifies the nominal length of valves with flanged ends and butt-welded ends. IV. German data 1. Structural length of flanged valves: The structural length of flanged valves as specified in the German DIN3202-1999 standard. 2. Structural length of valves with butt weld connections: The structural length of valves with butt weld connections as specified in the German DIN3202-1999 standard. 3. The length l in the structural length diagram of the wafer-type valve is the structural length of the valve. This structural length is the same for both unlined and lined valves. If a lining is used to eliminate the need for a dedicated seal, the dimensions can exceed 2mm. 4. Structural length of valves with internal thread connections. V. French standards: The standard NFE29-305-1999 in France specifies that the structural lengths of flanged steel gate valves, butterfly valves, check valves, plug valves, ball valves, globe valves, as well as copper alloy gate valves, globe valves, and check valves, are the same as those specified by ISO5752-1999 and GB/T12221-1989. VI. Japanese data: The code for the series of valve structural length specifications as defined by the Japanese JIS B2002-2000 standard. When the flange sealing surface type changes, its structural length needs to be adjusted. For flanged connections and clamp connections (flangeless), valves with a nominal pressure of 40 K or less, as well as those in the PN nominal pressure series, the allowable deviations in their overall length are specified in the table. The allowable deviations for the structural length of weld-connected valves and those with a nominal pressure above 63 K are specified in the table. Section 5: Connection Flanges I. Steel Pipe Flanges – Chinese Standards 1. GB/T9113.1 Dimensions of Integral Steel Pipe Flanges. The flange sealing surface types for integral steel pipe flanges include flat, raised, male-and-female, keyway, and ring-type surfaces. Types of integral steel pipe flanges with various seal face configurations, nominal pressures, and nominal diameters. (1) Flat integral steel pipe flange (2) Raised-face integral pipe flange (3) Grooved and raised-face integral steel pipe flange (4) Tenon-and-socket face integral steel pipe flange (5) Ring-connected face integral steel pipe flange (6) Octagonal gasket ring for connecting ring-connected face steel pipe flanges (7) Elliptical metal ring gasket for connecting ring-connected face steel pipe flanges. 2. GB/T13402-1992 Flanges for large-diameter carbon steel pipes: The structural types of flanges for large-diameter carbon steel pipes are divided into butt-welded type and integral type. II. Chinese Machinery Industry Standards for Steel Pipe Flanges
1. Types of pipeline flanges
2. Raised-face integral cast steel pipe flanges
3. Male-and-female face integral cast steel pipe flanges
4. Tenon-and-mortise face integral cast steel pipe flanges
5. Ring-connected face integral cast steel pipe flanges
6. Raised-face plate-type butt-welded steel pipe flanges
7. Raised-face welded steel pipe flanges
8. Male-and-female face welded steel pipe flanges
9. Tenon-and-mortise face welded steel pipe flanges
10. Ring-connected face welded steel pipe flanges
11. Metal tooth gaskets for pipeline flanges
12. Metal ring gaskets for pipeline flanges
13. Spiral wound gaskets for pipeline flanges

III. Chinese Chemical Industry Standards for Steel Pipe Flanges
1. Steel pipe flanges based on the European system (HG20592-1997)
2. Steel pipe flanges based on the American system (HG20615-1997)

IV. Chinese Petroleum and Chemical Industry Standards for Steel Pipe Flanges
1. Range of nominal diameter sizes for various nominal pressure classes
2. Types of flange connections and sealing surfaces. Flange connections for nominal diameters DN ≤ 600 mm. 3. Flange structure and dimensions for nominal diameter DN≥600mm. 4. Loose-flange type 5. Nominal pressure PN 5.0 ≥ MPa; types and dimensions of the sealing surfaces for male-female, tenon-socket flanges 6. Connection dimensions between flanges and carbon steel, low-alloy steel, and stainless steel pipes 7. Structural dimensions of flanges with a nominal diameter DN > 60 mm 8. Structural types and dimensions of flange screw holes and drilling holes 9. Structural dimensions of the welded joint between the flange and the pipe; groove dimensions for butt-welded flanges with a nominal diameter DN ≤ 600 mm ； Groove dimensions at the welded end of butt-weld flanges with nominal diameter DN＞600mm ； Structure and dimensions of the weld zones for socket weld and butt weld flanges and nozzles. 10. Flange pressure-temperature ratings: The maximum shock-free pressure at which a flange can be used at different operating temperatures is determined according to Table 1-308; intermediate values can be obtained using interpolation. 11. Maximum allowable deviations in flange dimensions 12. Structural forms and dimensions of metal ring gaskets 13. Coiled gaskets V. American ASME/ANSI B 16.5a-1992: Pipe flanges and flanged pipe fittings 1. Relationship between the flange face, flange thickness, and dimensions from center to edge as well as from one end to the other (structural length) 2. Structural forms and dimensions of connecting flanges 3. Structural forms and dimensions of weld ends without backing rings for weld-necked flanges VI. American ANSI B 16.6-1989, ANSI B 16.2-1989: Dimensions of cast iron flanges VII. American ASME B 16.47-1996: Dimensions of large-diameter steel flanges VIII. American API6A-2002: Steel pipe flanges IX. Structural forms and dimensions of Japanese JIS flanges X. Structural forms and dimensions of German DIN flanges 1. Gray cast iron flanges 2. Cast steel flanges XI. British BS4504-2000 standard flanges 1. Integral gray cast iron flanges 2. Integral ductile iron flanges 3. Integral steel flanges 4. Allowable deviations in flange dimensions XII. French NF E29-211-1999: Steel flanges Section 6: Other connection ends I. Butt weld ends 1. Provisions for butt weld ends according to Chinese standard GB/T12224-1989 2. Provisions for butt weld ends according to American ASME B 16.25-1992 standard 3. Provisions regarding butt weld ends of steel ball valves according to British BS5351-1999 standard II. Forged steel pipe fittings with socket welds and threaded connections 1. Forged steel pipe fittings with socket welds 2. Steel pipe fittings with threaded connections III. Auxiliary connections 1. Dimensions and markings specified in ASME B 16.34-1996 and BS1873-1996 2. Structural forms of plugs and sockets according to American ASME B 16.11-1991 standard