National Standard of the People's Republic of China. Specification for minimum thickness of the shell of valves

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1 ICS J16 National Standard of the People's Republic of China GBxxxx-xxxx Specification for minimum thickness of the shell of valves (Draft for approval) Issue Date: XXXX XX XX Implementation Date: XXXX XX XX Issued by the Standardization Administration of the People's Republic of China and the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China - 1 -

2 Foreword The sections 2 Normative references, Calculation of minimum thickness of shell, Threaded ends or butt welding ends steel valves with intermediate rated values, 4.3 Calculation of the minimum thickness of the shell of iron valves and Appendix A Bearings between the nominal diameter of steel valves and the basic inner diameter of valve ends are recommended. Any other contents are mandatory. The data of Table 1 in this Standard comes from Table 3-A of ASME B Any numerical value not originally in Table 3-A of ASME B shall be calculated using interpolation. This Standard is proposed by the China Machinery Industry Federation. This Standard is under the jurisdiction of the National Technical Committee 188 on Valves of Standardisation Administration of China (SAC/TC188). The organisations that participated in the drafting of this Standard: Shanghai Gaoke Valve Manufacturing Co. Ltd Anhui Baihu Valve Factory Co. Ltd; Hefei General Machinery Research Institute; Valve Co. Ltd. Jiangsu Mitac; Wuhan Boiler Group Valve Co. Ltd; Shanghai Lianggong Valve Factory Co. Ltd. The drafters of this Standard: Yang Heng, Jin Chengbo, Chen Jiangshan, Gao Bingshen, Zhang Yifang, Feng Yan, Mao Jianyun

3 Specification for minimum thickness of the shell of valves 1 Scope This standard specifies the shell thickness requirements for ball valves, butterfly valves, gate valves, globe valves, check valves, plug valves and diaphragm valves made of iron and steel. This Standard applies to valves with parameter range of: a) Steel valves with nominal pressure of PN 10 PN 760, nominal pressure of PN 760 is only applicable to welding-end valves; b) Flanged-end, wafer-end and butt-welding-end steel valves with nominal diameter not exceeding DN 1250 ; c) Socketed welding-end and threaded-end steel valves with nominal diameter not exceeding DN 100; d) Iron valves with nominal pressure of PN 1.0 ~ PN 25; e) Iron valves with nominal diameter not exceeding DN Normative References The provisions of the following documents become provisions of this Standard after being referenced. For dated reference documents, all later amendments (excluding corrigenda) and versions do not apply to this Standard; however, the parties to the agreement are encouraged to study whether the latest versions of these documents are applicable. For undated reference documents, the latest versions apply to this Standard. GB/T General requirements for industrial steel valves (neq ASTM B16.34a:1998) GB/T Stainless steel seamless tubes for fluid transport (GB/T , ASTM A269:2000, NEQ) 3 Minimum shell thickness of steel valves 3.1 General requirements Consult table to determine minimum shell thickness The shell thickness (t m ) of the body of any steel valve shall not be thinner than the data specified in Table 1, except in circumstances of ends with sizes indicated in Section to Section and Section of this Standard, as well as the circumstances indicated in Section 6.2 and Section 6.7 of GB/T When Table 1 is used, intermediate values for the listed numerical values can be calculated using linear interpolation. The shell thickness of any valve body not equipped with a liner shall be measured from the inner - 3 -

4 surface where it comes into contact with liquid. The minimum shell thickness shall not include the thickness of any backing, sleeving or bushing Calculation of minimum thickness of shell Any numerical value of shell thickness which cannot be consulted from Table 1 can be calculated by using formula (1). The smallest numerical value of shell thickness in Table 1 shall be greater than the numerical values calculated by using formula (1). t m = 1.5Pcd ns 1.2Pc (1) In which: T m is the shell thickness of the valve body, in millimetres (mm); Pc is the nominal pressure multiplied by 0.1 in megapascals (MPa); d is the Inner diameter of the end of valve body, in accordance with the specifications set out in Appendix A, in millimetres (mm); n is a coefficient: when Pc 2.5 MPa, n = 3.8; when Pc > 2.5 MPa, n = 4.8; S is the stress coefficient, S = 48.3 MPa; Formula (1) is not applicable to valves with nominal pressure greater than PN 760. The actual numerical values in Table 1 shall be approx. 3mm 5mm thicker than the numerical values calculated using formula (1). Due to the consideration of assembly stress, valve on-off stress, non-circular shape and stress concentration, the adding of additional thickness is required. So on the base of the calculated value for thickness value, the manufacturer shall add a certain thickness allowance to ensure the valve meets strength requirements

5 Table 1 Minimum shell thickness t m of valve body shell Unit: mm Inner diameter The basic inner diameter (d) of the end of any steel valve shall be selected in accordance with the inner diameter of the flow passage specified in Appendix A, but the minimum diameter shall be no smaller than 90% of the basic inner diameter of the valve end. Whereas for valves with socketed welding ends and threaded ends, when determining the d value the diameter of the socket or thread and any relevant borehole or counterbore shall not be taken into consideration, and the local deviation of the transition zone for processing of the welding groove is also not considered, apart from those circumstances specified in Section In situations where there is backing, bushing or sleeving, the inner diameter d shall be the diameter of lining and the separating surface of the valve body Valve neck Measured from the outer side of the valve body, along the direction of the valve neck within the section of 1.1 dt m (see Diagram 1), which maintains the minimum shell thickness specified in Section and Section 3.1.4, where diameter d is the inner diameter specified in Section and t m is the minimum shell thickness in Table 1. The range of the requirements of the minimum shell thickness is from the inner surface of the valve which comes into contact with the liquid, to the filler seal of the valve cap, and all pressure cavity walls must be included. Beyond the abovementioned 1.1 dt m, there should be a straight cylindrical section with an inner diameter of d' at the valve neck, and the shell thickness of this local area shall not be smaller than t', with t' being the shell thickness determined according to the pressure grade to the corresponding diameter d'' from Table 1. Diagram 1 Valve neck - 5 -

6 For any valve with a nominal pressure in the range of PN 16 to PN 420, the corresponding inner diameter of its valve neck shall be calculated by using the formula (2): For any valve with a nominal pressure greater than PN420, the corresponding inner diameter of its valve neck shall be calculated by using the formula (3): In which: d' is the diameter of the straight cylinder section of the valve neck, in millimetres (mm); d'' is the corresponding inner diameter calculated according to d', in millimetres (mm); PN is the nominal pressure. a) In special cases where d' > 1.5d, within the overall length of valve neck, including the inner diameter d' of section 1.1 dt m, the shell thickness shall not be less than t'. b) when the inner diameter of the valve neck is a lot smaller than the inner diameter of the valve flow passage, such as d/d' 4 (see Diagram 2) of a butterfly valve, the shell thickness of the local area within the section L = t m (1+1.1 dt m ) from the inner diameter of the valve body to the intersection point of the axis of the valve neck diameter shall not be less than t'. t' is obtained from Table 1 according to the inner diameter d' of the corresponding valve neck. The shell thickness of the other section of the valve neck, beyond the above mentioned section L=t m (1+1.1 dt m ), can be obtained from Table 1 according to the value of d''. c) In cases where there will be drilling or tapping on the wall of the valve neck parallel to the direction of the valve neck axis, the sum thickness of the inner side and outer side connecting lines must not be less than t m or t', see Diagram 2 for f' + g' t 2 '. The thickness of the inner side connecting line of the drilling and the thickness of the connecting line at the bottom shall not be less than 0.25t m or 0.25t', see Diagram 2 for f 0.25t m, j 0.25t m. In addition, this thickness shall extend to a distance along the valve neck, starting from the top of the neck, which shall be equal to at least the sum length of the depth of the drilling plus half of the drilling diameter or the diameter of the thread. (2) (3) - 6 -

7 Relation: Reference t t m m t 1 ' 3.1.3b n t 2 ' 3.1.3b L=tm (1+1.1 dt m ) 3.1.3b f 0.25t m note c f + g t m c f' 0.25t 2 ' note c f' + g' t 2 ' 3.1.3c c 0.75t m 3.1.8e j 0.25t m note d e 0.25t 1 ' note b Note 1: not less than 0.25mm. Note 2: circumstances specified in Section are not inclusive. Diagram 2 Butterfly valve body - 7 -

8 3.1.5 Threaded-end or butt-welding-end steel valves with intermediate rated value The minimum shell thickness of intermediate pressure grade valve shells can be determined by formula (4) and formula (5): In which: P rd is the nominal pressure of the intermediate pressure grade; t m is the minimum shell thickness of the intermediate pressure grade, in millimetres; P d is the working pressure under design temperature, in megapascals (MPa); P 1 is the pressure lower value adjoining to P d, unit as Megapascal (MPa); P 2 is the pressure higher value adjoining to P d, unit as Megapascal (MPa); P r1 is the nominal pressure PN which corresponds to P 1 ; P r2 is the nominal pressure PN which corresponds to P 2 ; t 1 is the minimum shell thickness of nominal pressure P r1, unit as millimetre (mm); t 2 is the minimum shell thickness of nominal pressure P r2, unit as millimetre (mm); On the basis of design temperature and working pressure P d, find the pressure-temperature ratings which are specified in Section of GB/T , then determine the lower rated pressure value P 1 which adjoins to P d and the adjoining higher value of P 2 ; P 1 and P 2 being equivalent to the rated values of pressure grades of P r1 and P r2. The intermediate pressure grade of P rd which meets the design condition shall be determined by using formula (4). Use appropriate inner diameter d from Table 1 to determine the minimum shell thickness t 1 and t 2 for the nominal pressure P r1 and P r2 respectively. The minimum shell thickness which meets the design condition shall be determined by using formula (5) Shell thickness of valve ends a) Butt welding ends The shell thickness of the flow passage of the valve welding groove shall not be less than the required value t m specified in Section or In the case of the distance from the welding end being 1.33t m, the thickness shall not be less than 0.77t m. b) Socketed welding ends and threaded ends The distance from the centre line of the basic cylinder shaped flow passage to the outer surface of the valve flow passage shall not be less than 0.5 times the nominal outer diameter of the tubes listed in GB/T Local section Where the shell thickness of any local section is less than the minimum shell thickness, it may be acceptable in cases where the following restrictive conditions are met. a) in sections where the thickness is smaller than the minimum thickness, the area can be surrounded by a circle with diameter not greater than 0.35 d 0 t 0. For valve neck, d 0 = d' and t 0 = t' (see Section 3.1.3). For all of the other local sections, d 0 = d (see Section 3.1.2) and t 0 = t m (see the corresponding Section or 3.1.4); - 8 -

9 b) the measured thickness shall not be less than 0.75t 0 ; c) the distance between the edges of the surrounding circles shall not be less than 1.75 d 0 t Additional thickness allowance Due to the effects of factors such as piping system load, operation (switch on and off) load, noncircular shape and stress concentration, an additional thickness allowance for the shell thickness obtained from Table 1 shall be required. There are many factors to be considered for calculating the additional thickness allowance, so the allowance for additional thickness shall be calculated and determined by the manufacturer. Steel valves with inclined rods (enlarging the intersecting surface and the opening of the inner cavity of the valve body) and steel valves with composite welding valve bodies may require additional strengthening in order to ensure sufficient strength and hardness Wafer steel valve For wafer steel valves (such as butterfly valves), its shell thickness shall comply with the requirements for flanged end steel valves and the requirements listed below (see Diagram 2). a) The required minimum shell thickness t m shall be measured as the minimum distance from the inner circumference to the outer circumference of the valve body, or the distance from the inner circumference of the valve body to the inner-side tangent line of the flange bolt hole. b) The inner thickness of vent or thread blind holes which are near to the valve rod passage (see Diagram 2(e)) shall not be less than 0.25 times of the required shell thickness for the valve neck, and no thinner than 2.5mm. c) The inner side thickness of the holes which are parallel to the valve body passage (see Diagram 2(f)) shall not be less than 0.25t m, and no thinner than 2.5mm. The sum of the inner side thickness and outer side thickness shall not be less than the shell thickness t m of the valve body. d) The minimum thickness of the valve shell (see Diagram 2(j)) between two adjoining holes on the valve body wall shall not be thinner than 0.25t m, and no less than 2.5mm. e) The thickness on the inner-side of the radial blind holes (see Diagram (c)) shall not be thinner than 0.75t m. 3.2 Specifications for minimum thickness for all types steel valve shells Steel valves used in petroleum and chemical industry Table 2 specifies the minimum shell thickness for gate valves, block valves, plug valves, lift check valves, swing check valves and wafer check valves which are made of steel and are used in petroleum, chemical and other related industries, while Table 1 specifies the minimum shell thickness for ball valves made of steel and used in petroleum, chemical and other relevant industries

10 3.2.2 Steel plug valves used under ordinary working conditions Table 3 specifies the minimum shell thickness for steel plug valves used under ordinary working conditions

11 3.2.3 Compact steel valves Table 4 specifies the minimum shell thickness for compact steel valves

12 4 Minimum shell thickness of iron valves 4.1 Shell material of iron valves The data provided in this Standard for the minimum thickness of valve shells, are only applicable to the valve shells made of: grey cast-iron HT200, with cast iron HT250 being denoted by a * mark, and nodular cast-iron QT The minimum shell thickness of iron valves shall be looked up using the tables Table 5 specifies the minimum shell thickness for iron gate valves Table 5 Minimum shell thickness of iron gate valves

13 4.2.2 Table 6 specifies the minimum shell thickness for iron block valves and lift check valves Table 7 specifies the minimum shell thickness for iron swing check valves

14 4.2.4 Table 8 specifies the minimum shell thickness for iron ball valves Table 9 specifies the minimum shell thickness for iron butterfly valves Table 9 Minimum shell thickness for iron butterfly valves

15 4.2.6 Table 10 specifies the minimum shell thickness for iron diaphragm valves Table 11 specifies the minimum shell thickness for iron plug valves

16 4.3 Calculation of minimum shell thickness of iron valves Middle cavity of valve body as drum-shaped thin shell The minimum shell thickness of the middle cavity of valve body as drum-shaped thin shell shall be calculated by using formula (6): In which: S B is the shell thickness after having allowed for corrosion, in millimetres (mm); D N is the maximum inner diameter of the middle cavity of the valve body, in millimetres (mm); P is the design pressure, in megapascals (MPa) measured as 0.1 times the nominal pressure; [ L ] is the permissible tensile stress of the material, in megapascals (MPa); C is the additional allowance (mm) taking into account factors such as the deviation for casting, technology and media corrosion. This value shall be determined by the design department on the basis of production conditions Non-cylindrical shell in middle cavity of valve body See Diagram 3 for the shape of non-cylindrical shells in the middle cavity of the valve body; check against formula (7) and formula (8)

17 Diagram 3 Non-cylindrical thin shell valve body In which: A is the synthetic stress at A, in megapascals (MPa); B is the synthetic stress at B, in megapascals (MPa); S B is the design shell thickness allowing for corrosion, in millimetres (mm); a is the semi-major axis of the shell body cross section, in millimetres (mm); b is the semi-minor axis of the shell body cross section, in millimetres (mm); K is the gyration radius of the shell body to its axis, in millimetres (mm); Gyration radius K of the shell body axis a) for ellipse shaped cross sections (see Diagram 3a), K shall be determined by using formula (9): In which: f coefficient. Consult Table 12. in actual use, when b/a 0.4, take K = (a+b)/

18 b) for rectangular shaped cross sections (see Diagram 3b), K shall be determined by using formula (10): c) for rounded rectangle shaped cross sections (see Diagram 3c), K shall be determined by using formula (11); In which: x is the eccentric dimension of the rounded rectangle (see Diagram 3c), in millimetres (mm); d) for semi-oval shaped cross sections (see Diagram 3d), K shall be determined by using formula (12): In which: r i is the radius at the measuring points, in millimetres (mm); i is the serial number of the measuring points (mm); n is the quantity of the measuring points. The calculated K value becomes more precise when there are more measuring points The calculated value of A and B, shall be tensile stress when positive and shall be compressive stress when negative. The modular value of this should be less than its permissible bending stress [ w ]

19 Appendix A (Informative annex) Relations between the nominal diameters and the basic inner diameters of steel valves The relations between the shell thickness and inner diameters of steel valves are the foundations of pressure rating values. The specific design basis for any combination of pressure-diameter-material can be interpolated. Using the flange dimension of standard pressure grade series, the nominal diameters for corresponding pipes and the matching inner-pipe diameters can be determined. These relations provide an effective design basis for the corresponding flanged-end steel valves. This design basis is also applicable to welding-end steel valves, because many aspects of these valves the same, with only their connection ends differing. Table A.1 provides the nominal diameters for specific steel valves and the basic inner diameters for valve ends with specific pressure grades. The inner diameter values for pipes with nominal diameter above DN 750 or below DN 420 can be determined with linear interpolation

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