- 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 val ves 
 
 
 
 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 ran ge 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 a nd 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 pr ovisions 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 versio ns 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  Minim um shell thickness of steel valves  
3.1 General requirements  
3.1.1 Consult table to determine minimum shell thickness  
The shell thickness (t m) of the body of any steel valve shall not be thinner than t he 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. T he 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  formul a (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 s hell thickness of the valve body, in millimetres  (mm);  
Pc is the nominal pressure  multiplied by  0.1 in  megapascal s (MPa);  
d is the Inner diameter of the end of valve body, in accordance with the specifications set out in 
Appendix A, in millimetre s (mm);  
n is a c oefficient : when Pc  2.5 MPa, n  = 3.8; when Pc > 2.5  MPa, n  = 4.8; 
S is the s tress 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 t he 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  
 3.1.3 Inner diameter  
The basic inner diameter ( d) of the end of any st eel 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 als o not considered, apart 
from those circumstance s 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  
Meas ured from the outer side of the valve body, along the direction of the valve neck within the 
section of 1.1 dtm (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. T he range of the requirement s of the minimum  
shell thickness is from the inner surface of the valve which comes in to 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 dtm, there should be a st raight cylindr ical 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 a ny 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 a ny valve with a nominal pre ssure  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 millimetre s (mm);  
d'' is the corresp onding inner diameter calculated according to d', in millimetre s (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 dtm, 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+1.1 dtm) 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+1.1 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 v alve 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 0.25 tm or 0.25 t', see Diagram 2 for f  0.25 tm, j 0.25tm. In 
addition, this thickness shall extend to a distance along the valve neck, start ing 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+1.1 dtm)  3.1.3b  
f  0.25 tm note 1   3.1.8c  
f + g  tm.   3.1.8c  
f'  0.25 t2' note 1  3.1.3c  
f' + g'  t2'   3.1.3c  
c  0.75 tm   3.1.8e  
j  0.25 tm note 1   3.1.8d  
e  0.25 t1' 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 valve body  
 
- 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 shell s can be determined by 
formula (4) and formula (5):  
 
 
In which:  
Prd is the nominal pressure  of the intermediate pressure grade;  
tm is the minimum  shell thickness of the intermediate pressure grade, in millimetre s; 
Pd is the working pressure under design t emperature, in megapascal s (MPa); 
P1 is the pressure lower value adjoining to Pd, unit as Megapascal ( MPa ); 
P2 is the pressure higher value adjoining to Pd, unit as Megapascal ( MPa ); 
Pr1 is the  nominal pressure  PN which corresponds to P1; 
Pr2 is the nomina l pressure  PN which corresponds to P2; 
t1 is the minimum  shell thickness of nominal pressure  Pr1, unit as millimetre (mm);  
t2 is the minimum  shell thickness of nominal pressure  Pr2, unit as millimetre (mm);  
 
On the basis of design temperature and working p ressure Pd, find the pressure -temperature ratings 
which are specified in Section 3.1.1 of GB/T 12224 -2005, then determine the lower rated pressure 
value P1 which adjoins to Pd and the adjoining higher value of P2; P1 and P2 being  equivalent to the 
rated va lues of pressure grades of Pr1 and Pr2. The intermediate pressure grade of Prd 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  Pr1 and Pr2 respectively. The minimum  shell thickness which meets  the 
design condition shall be determined by using formula (5).  
 
3.1.6 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 tm specified in Section 3.1.1 or 3.1.4 . In the case of the distance from the welding 
end being  1.33 tm, the thickness shall not be less than 0.77 tm. 
 
b) Socketed welding ends and threaded ends  
The dis tance 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/T14976.  
 
3.1.7 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 d0t0. For valve neck, d0 = d' and t0 
= t' (see Section 3.1.3). For all of the other local sections, d0 = d (see Section 3.1.2) and 
t0 = tm (see the corresponding Section 3.1.1 or 3.1.4);  - 9 -  
b) the measured thickness shall no t be less than 0.75 t0; 
 
c) the distance between the edges of the surrounding circles shall not be less than 1.75 d0t0. 
 
3.1.8 Additional thickness allowance  
Due to the effects of factors such as piping system load, operation (switch on and off) load, non -
circular shape and stress concentration, an addition al thickness allowance for the shell thickness 
obtained from Table 1 shall be required. There are many factors to be considered for calculating t he 
additional thickness allowance, so the allowance for additio nal thickness shall be calculated and 
determined by the manufacturer.  
 
Steel valves with inclined rods (enlarg ing the intersecting surface and the opening of the inner 
cavity of the valve body) and steel valves with composite welding valve bodies may requi re 
additional strengthening  in order  to ensure sufficient strength and hardness.  
 
3.1.9 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 require ments listed below  (see Diagram 2).  
 
a) The required minimum  shell thickness tm 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 hole s 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 0.25 tm, 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 tm 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 0.25 tm, 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 0.75 tm. 
 
3.2 Specifications for minimum  thickness for all types steel valve shells  
 
3.2.1 Steel valves used in petroleum and chemical industry  
 
Table 2 specifies the minimum shell thic kness  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 rel ated 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 
cond itions . 
- 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 val ve 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 QT450 -10. 
 
4.2 The minimum  shell thickness of iron valves shall be looked up using the  tables  
 
4.2.1  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  
 
4.2.3 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.  
 
 
4.2.5 Table 9 specifies the minimum shell thickness for iron butterfly valves  
 
Table 9 Minimum  shell thickness for iron butterfly v alves  
 
 
- 15 - 4.2.6 Table 10 specifies the minimum shell thickness for iron diaphragm valves  
 
 
4.2.7 Table 11 specifies the minimum shell thickness for iron plug valves.  
 
- 16 -  
4.3 Calculation of minimum  shell thickness of iron valves  
 
4.3.1 Middle cavity of valv e 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:  
SB is the shell thickness after having allowed for corrosion, in millimetre s (mm); 
DN is the maximum inner diameter of the middle cavity of  the valve body, in millimetre s (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 megapasc als (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.  
 
4.3.2 Non-cylindric al shell in m iddle cavity of valve body  
 
4.3.2.1 See Diagram 3 for the shape of non-cylindrical shell s 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 ); 
SB is the design shell thickness allowing for corrosion ,  in millimetre s (mm);  
a is the semi -major axis of the shell body cross section, in millim etres (mm);  
b is the semi-minor axis of the shell body cross section, in millimetre s (mm);  
K is the gyration radius of the shell body to its axis, in millimetre s (mm);  
 
4.3.2.2 Gyration radius K of the shell body axis  
 
a) for ellipse shaped cross section s (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)/2.  
 
- 18 -  
b) for rectangular shaped cross section s (see Diagram 3b), K shall be determined by using formula 
(10):  
 
 
c) for rounded rectangle shaped cross section s (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 millimetre s (mm);  
 
 
d) for semi -oval shaped cross section s (see Diagram 3d), K shall be determined by using formula 
(12):  
 
 
In which:  
ri 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 . 
 
4.3.2.3 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 interp olated . 
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 differ ing. Table A.1 provide s the nominal diameters for specific steel 
valves and the basic inne r 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 .