- 1 -

ICS 23.060.01 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

- 2 -

Foreword

The sections 2 Normative references, 3.1.2 Calculation of minimum thickness of shell, 3.1.5 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 16.34-2004. Any numerical value not originally in Table 3-A of ASME B 16.34-2004 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 3000.

2 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 12224-2005 General requirements for industrial steel valves (neq ASTM B16.34a:1998) GB/T 14976 Stainless steel seamless tubes for fluid transport (GB/T 14976-2002, ASTM A269:2000, NEQ)

3 Minimum shell thickness of steel valves

3.1 General requirements

3.1.1 Consult table to determine minimum shell thickness

The shell thickness (tm) 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 3.1.3 to Section 3.1.6 and Section 3.1.8 of this Standard, as well as the circumstances indicated in Section 6.2 and Section 6.7 of GB/T 12224-2005. 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

- 4 -

surface where it comes into contact with liquid. The minimum shell thickness shall not include the thickness of any backing, sleeving or bushing. 3.1.2 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).

tm=1.5Pcd

nS 1.2Pc (1) In which: Tm 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 tm of valve body shell Unit: mm

3.1.3 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 3.1.5. 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.

3.1.4 Valve neck Measured from the outer side of the valve body, along the direction of the valve neck within the section of 1.1dtm (see Diagram 1), which maintains the minimum shell thickness specified in Section 3.1.1 and Section 3.1.4, where diameter d is the inner diameter specified in Section 3.1.2 and tm 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 1.1dtm, 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

- 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): (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): (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 1.1dtm, 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 = tm (1+1.1dtm) 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=tm (1+1.1dtm), 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 tm or t', see Diagram 2 for f' + g' t2'. 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 0.25tm or 0.25t', see Diagram 2 for f 0.25tm, j 0.25tm. 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.

- 7 -

Relation: Reference

t tm. 3.1.1 m t1' 3.1.3b n t2' 3.1.3b L=tm (1+1.1dtm) 3.1.3b f 0.25tm note 1 3.1.8c f + g tm. 3.1.8c f' 0.25t2' note 1 3.1.3c f' + g' t2' 3.1.3c c 0.75tm 3.1.8e j 0.25tm note 1 3.1.8d e 0.25t1' note 1 3.1.8b

Note 1: not less than 0.25mm. Note 2: circumstances specified in Section 3.1.6 are not inclusive.

Diagram 2 Butterfly va