- 1 -  
ICS 23.020.30  
 
 
 
 
 
National Standard  
of the People's Republic of China  
 
 
GB 150.4 - 20xx  
Replaces Part of GB 150 - 1998  
 
 
 
Pressure Vessels  
Part 4: Fabrication, inspection and testing, 
and acceptance  
 
 
 
 
  
(Draft for approval)  
 
 
 
 Issue Date: 20XX – XX – XX Implementation Date: XX0XX – XX –
XX 
 
 
 
Issued by the General Administration of Quality Supervision, Inspection and 
Quarantine of the People's Republic of China  
- 2 -  
 
Table of contents  
 
 
Foreword....................................................... .....................................................  
 
1 Scope.................................................................................................................  
 
2 Normative references......................................................... ...............................  
 
3 Terms...............................................................................................................  
 
4 General provisions................................................................................... ..........  
 
5 Material retesting, segmentation and symbol transportation............................  
 
6 Cold forming, hot forming and assembly..........................................................  
 
7 Welding............................................. .................................................................  
 
8 Heat treatment....................................................................................................  
 
9 Test sample and specimen............................................. ......................................  
 
10 Non -destructive testing.....................................................................................  
 
11 Pressure test and leak test..........................  
 
12 Layered pressure vessel................... ...........  
 
13 Requirements for pressure vessel leaving factory................  
 
 
 
 
 
 - 3 -  
Foreword  
 
 
GB 150 Pressure Vessels consists of following four Parts:  
_____Part 1: General requirements  
_____Part 2: Materials  
_____Part 3: Designs;  
_____Part 4: Fabrica tion, inspection and testing, and acceptance.  
 
This Part is the Part 4 of GB 150. The draft procedure of this Part is in accordance with the 
provisions specified in GB /T 1.1 – 2009 Directives for standardisation.  
 
This Part replaces some section contents in Chapter 10 and Appendix C of GB 150 – 1998 Steel 
pressure vessels, compares with GB 150 – 1998, apart from the editorial amendments, other 
changes made in the main technical contents are as below:  
 
a) Added the normative references and technical terms.  
 
b) Chapter 4 and Chapter 5:  
---- Moved the provisions on the classification of weld joints of pressure vessels to GB 150.1 and 
added Category E weld joints;  
---- Added provisions on the risk preventing and controlling during the manufacturing process of 
pressure vessels, specifies provisions on the applications of new technologies, new processes and 
new methods as well as provisions on the information management.  
---- Added provisions on the design modification, material substitution and material retesting  during 
the manufacturing process of pressure vessels.  
 
c) Chapter 6  
---- Amended the provisions on the actual thickness of the pressure components after forming;  
---- Amended about the forming methods, the deviation inspection of the head shapes as well a s the 
requirements on the straight edges of heads are not permitted to have any longitudinal folds;  
---- Amended the cylinder linearity inspection method and requirements on the tolerance, the layout 
of the weld joints on shells.  
 
d) Chapter 7:  
---- Amende d the required scope for the implementation of the welding procedure qualification  
assessment and the retention time period of the technical files, appropriately added provisions on 
the sampling, test methods, compliance quota and the retention time period  of the samples.  
---- Amended the provisions on the once more heat treatment after the welding repair.  
 
e) Chapter 8 (GB 150 – 1998, 10.4)  
------- Added provisions on the heat treatments for the property restore and the heat treatments for 
improving the mec hanical properties and other heat treatments of the formed pressure components;  
------- Added the requirements on the heat treatment furnaces, heat treatment technologies and 
records;  
-------- Amended the required implementation scope for the post -weld heat treatment of pressure 
vessels and its pressure components, and the operating requirements on the post -weld heat - 4 - treatment;  
 
f) Chapter 9:  
--------- Adjusted the ranges of the product welding samples, base material heat treatment samples as 
well as other sam ples and test items which are required to be prepared, relevantly added the 
requirements on sampling, inspection and assessment;  
--------- Added provisions on the preparation of the product welding samples and the base metal heat 
treatment samples. Appropri ately added requirements on the sampling, inspection and the 
qualification assessment.  
 
g) Chapter 10:  
--------- Added provisions on the choices of the non -destructive testing and the implementation time 
of the non -destructive testing;  
--------- Adjusted the  scope of full radiographic (100%) testing or ultrasonic testing, local 
radiographic testing or ultrasonic testing and surface testing, added the requirements on the 
technical grades of radiographic testing and ultrasonic testing.  
--------- Added the time o f flight diffraction technique (TOFD), and specified the compliance grades;  
--------- Added requirements on the combination testing;  
--------- Added the requirement on the retention of non -destructive testing files.  
 
h) Chapter 11:  
--------- Added the pressur e test method for the gas-hydrostatic combined test;  
--------- Amended the provisions on the temperature of pressure test;  
--------- Clarified that the airtightness test method is one of the leak testing methods, added three 
leak testing methods such as the ammonia leak test, helium leak test and halogen leak test.  
 
i) Chapter 12:  
-------- Added the requirements on the fabrication, inspection and testing, and acceptance of wrapped 
layered cylindrical entirety  pressure vessels and flat-steel ribbon wound  pressu re vessels.  
 
j) Chapter 13:  
--------- Adjusted the contents of the quality certificate issued when the pressure vessels leaving  
factory, added required documents;  
--------- Added the contents of the product nameplate, added items such as equipment codes.  
  
This Standard was proposed and formulated by China Standardisation Committee on Boilers and 
Pressure Vessels (SAC/TC 262).  
 
The main organisation is responsible for the drafting of this Standard is:  
Hefei General Machinery Research Institute;  
 
The organis ations participated in the drafting of this Standard are:  
China Special Equipment Inspection & Research Institute;  
SINOPEC Engineering Incorporation;  
Lanzhou Petrochemical Machinery Plant;  
SINOPEC Nanjing Chemical Industrial Co.  Ltd, Chemical Machinery Wo rks 
 
 
The main drafters of this Standard are: Cui Jun, Shou BiNan, Chen XueDong, Yang GuoYi, Chen 
YongDong, Li ShiYu, Wang Bing, Xue Feng, Chen JianYu, Han Bing, Yao ZuoQuan.  - 5 -  
This Standard replaces the previous versions: GB 150 – 1989, GB 150 – 1998.  
 
The China Standardisation Committee on Boiler and Pressure Vessels (SAC/TC 262) is responsible 
for the interpretation of this Standard.  
 - 6 -  
 
           
Pressure Vessels  
Part 4: Fabrication, inspection and testing, and acceptance  
 
 
 
 1  1  Scope  
1.1 This Standard spec ifies the requirements for the fabrication, inspection and testing, and acceptance 
of steel pressure vessels within the applicable scope of GB 150; the requirements for the fabrication, 
inspection and testing, and acceptance of pressure vessels made of oth er materials shall be in 
accordance with the relevant standards.  
 
1.2 This Standard is applicable to the structures of pressure vessels as follows: single -layer welded 
pressure vessels, forged -welded pressure vessels, and multi - layered pressure vessels (I ncluding 
wrapped layered cylindrical segment, wrapped layered cylindrical entirety, flat steel ribbon wound, 
and shrink fit pressure vessels).  
 
1.3 With regard to low -temperature austenitic steel pressure vessels (design temperature lower than 
-196oC), the  additional requirements for the fabrication, inspection and testing, and acceptance should 
be specified by the consultations between the parties who participate in the construction of the 
pressure vessels, such requirements should be stated in the design documents by the design units.  
 2  2  Normative References  
The following documents are absolutely essential to the application of this Standard. For dated 
reference documents, only the dated versions apply to this Standard; For undated reference 
documents, the l atest versions (including all amendments) apply to this Standard.  
 
GB 150.1 Pressure vessels Part 1: General requirements  
 
GB 150.3 Pressure vessels Part 2: Materials  
 
GB 150.3 Pressure vessels Part 3: Design  
 
GB/T 196 General purpose metric screw threads  – Basic dimensions  
 
GB/T 197 General purpose metric screw threads – Tolerance  
 
GB/T 228 Metallic materials – Tensile testing at ambient temperature  
 
GB/T 229 Metallic materials – Charpy pendulum impact test method  
 
GB/T 232 Metallic materials – Bend test  
 
GB/T 1804 General tolerances – Tolerances for linear and angular dimensions without individual 
tolerance indications  - 7 -  
GB/T 25198 Heads for pressure vessels  
 
GB/T 21433 Detecting susceptibility to intergranular corrosion in stainless steel pressure vessel  
 
JB/T 4700 Type and specification for pressure vessel flanges  
 
JB/T 4701 A -type socket -weld flange  
 
JB/T 4702 B -type socket -weld flange  
 
JB/T 4703 Welding Neck flange  
 
JB/T 4704 Non -metallic gaskets  
 
JB/T 4705 Spiral wound gaskets  
 
JB/T 4706 Double -jackete d gaskets  
 
JB/T 4707 Stud bolts  
 
JB/T 4708 Welding procedure qualification for pressure equipment  
 
JB/T 4709 Welding specification for steel pressure vessels  
 
JB/T 4711 Coating and packing for pressure vessels transport  
 
JB/T 4730.1 Non -destructive testing  for pressure equipment – Part 1: General requirements  
 
JB/T 4730.2 Non -destructive testing for pressure equipment – Part 2: Radiographic testing  
 
JB/T 4730.3 Non -destructive testing for pressure equipment – Part 3: Ultrasonic testing  
 
JB/T 4730.4 Non -destructive testing for pressure equipment – Part 4: Magnetic particle testing  
 
JB/T 4730.5 Non -destructive testing for pressure equipment – Part 5 Penetrant testing  
 
JB/T 4730.6 Non -destructive testing for pressure equipment – Part 6 Eddy current testing  
 
JB/T 4736 Reinforcing pad  
 
JB/T 4744 Mechanical property tests of product welded test coupons for steel pressure vessels  
 
JB/T 4747.1 Technical permission of steel welding rod purchasing for pressure vessels – Part 1 
Terms and conditions of purchasing  
 
JB/T 4747.2 Technical permission of steel welding rod purchasing for pressure vessels – Part 
2Steel welding rod  
 
JB/T 4747.3 Technical permission of steel welding rod purchasing for pressure vessels – Part 3: Gas - 8 - shielded arc welding steel wires and filler wir es 
 
JB/T 4747.4 Technical permission of steel welding rod purchasing for pressure vessels – Part 4: 
Submerged -arc welding steel wires and welding fluxes  
 
JB/T 4747.5 Technical permission of steel welding rod purchasing for pressure vessels – Part 5: 
Build -up welding stainless steel strips and welding fluxes  
 
JB/T 4747.6 Technical permission of steel welding rod purchasing for pressure vessels – Part 6: 
Aluminium and aluminium  alloy welding wires and filler wires  
 
JB/T 4747.7 Technical permission of steel we lding rod purchasing for pressure vessels – Part 7: 
Titanium and titanium  alloy welding wires and filler wires  
 
TSG R004 Technical Supervision Regulation for Safety of Stationary Pressure Vessels  
 
 
 3  3  Terms  
The terms and definitions specified in GB 150.1 an d below apply to this Standard.  
3.1 Forged -welded pressure vessel  
Pressure vessels formed by the con nections of circumferential welded joints , for which the 
cylindrical segments or heads (or cylindrical body ends) are  made by machined cylindrical shapes or  
other shap es of forged parts.  
 
3.2 Layered pressure vessel  
Pressure vessels for which the cylinders are wrapped by two or more than two layer s of sheets or 
strips, the construction between the layers are non -welding method, lined pressure vessels are not 
included.  
 
3.3 Wrapped pressure vessel  
Layered pressure vessels for which the inner cylinders are wrapped layer by layer of sheets or 
strips.  
Wrapped pressure vessels including the following two types of structures:  
 
a) Wrapped layered cylindrical segment  pressure vessels, which means that the pressure vessels are 
formed by the connection of circumferential welded joints  and where a single segment of inner 
cylinder is wrapped by multi -layers of sheets.   
 
b) Wrapped layered cylindrical entirety pressure vess els, which means that pressure vessels for which 
its entire inner cylinders are wrapped by multi -layers of sheets.  
 
3.4 Flat steel ribbon wound pressure vessel  
Layered pressure vessels formed by staggered winding steel strips layer by layer along a certain  
winding angle.   
 
3.5 Shrink fit pressure vessel  
By shrinking fit the cylindrical segments which have a certain shrink range, layer by layer of - 9 - several layers as heating up, and eliminating the shrink fit prestress by heat treatment and forming a 
shrink fi t cylindrical segment, then by way of welding the circumferential welded joints  to formed a 
pressure vessel.  
 
3.6 Thickness of steel material  
The thicknesses of the components such as steel sheets, steel pipes or forged parts etc. Which can 
directly form a  pressure vessel, presented by s. 
 
3.7 Cold forming  
The plastic deformation process conducted under the recrystall isation temperature of the workpiece 
materials.  
In engineering practice, usually the plastic deformation process conducted below ambient 
temp erature is known as cold forming; plastic deformation process conducted between cold forming 
and hot forming is known as warm forming.  
 
3.8 Hot forming  
Plastic deformation process conducted above the recrystall isation temperature of the workpiece 
material s. 
 
4 General provisions  
 
4.1 Fabrication, inspection and testing, and acceptance basis of pressure vessels  
 
4.1.1 The fabrication, inspection and testing, and acceptance of pressure vessels shall comply with 
the provisions in this Part and the requirement s in the design documents. Within the application 
scope of the following criteria, if there is no additional provisions specified then generally should 
meet the following requirements:  
 
a) The heads should meet the provisions specified in GB/T 25198;  
 
b) The reinforcing pads should meet the provisions specified in JB/T 4736;  
 
c) The pressure vessel flanges and its connectors should meet the provisions specified in JB/T 
4700 –4707;  
 
d) The welding materials should meet the provisions specified in JB/T 4747;  
 
4.1.2 The selection of pipe flanges should be in accordance with the relevant provisions specified in 
TSG R0004.  
 
4.2 The risk preventing and controlling during the manufacturing process of pressure vessels  
For any pressure vessel if the design unit has  issued a risk assessment report,  then on the basis of 
the main failure modes, pressure vessel fabrication and inspection requirements and suggestion 
listed  in this risk assessment report, the manufacturing unit should complete the following tasks:  
 
a) Rea sonably determine the manufacturing and inspection technology;  
 
b) The failure modes, the prevention and protection measures stated in the risk assessment report 
should be reflected in the product quality documents.  
 - 10 - 4.3 Design amendments and material sub stitution  
Before the manufacturing unit carries out any modification to the original design and substitution of  
the pressure component materials, the manufacturing unit should obtain a written approval from the 
original design unit and make a detailed reco rd on the project completion drawings.  
 
4.4 Application of new technologies and new processes  
When using new technologies, new processes and new methods which are not listed in this Standard 
and are for the manufacturing and inspection of pressure vessels , the provisions should be subjected 
to the technical assessment specified in TSG R0004:  
 
a) When using the non -destructive testing method which is not listed in JB/T 4730 or beyond the 
applicable scope of JB/T 4730 to carry out non -destructive testing to pressure vessels which are still 
in preparation;  
 
b) When using other methods to eliminate the residual stress of pressure vessels and pressure 
components.  
 
4.5 Information management  
The manufacturing units of pressure vessels should timely input the rel evant data of the pressure 
vessels into the information management system for special equipment as required.  
 
5 Material retesting, segmentation and symbol transplantation  
 
5.1 Material retesting  
 
5.1.1 The following materials should be retested:  
 
a) The purchased Grade IV forged parts for the use of Type III pressure vessels;  
 
b) The main pressure components for which the authenticity of their quality certificates can not be 
determined, or for which the properties and chemical composition are doubtful;  
 
c) The imported materials used for preparing the main pressure components;  
 
d) Austenitic stainless steel flat sheets used for preparing the main pressure components;  
 
e) Materials requested in the design documents for retesting.  
 
5.1.2 Austenitic stainle ss steel flat sheets should be retested for its mechanical properties (for whole 
roll users, after the flat sheets are opened for operation, a group of retest samples from the heads, 
middle and tails of the corresponding flat sheets should be intercepted; for non -whole roll users, a 
group of retest samples from the ends of the flat sheets should be intercepted); for retesting 
situations stated in a), b), c) and e) of 5.1.1, should retest the chemical composition by according to 
the furnace number and retest  the mechanical properties by according to the lot number.  
 
5.1.3 The material retesting results should be consistent with the provisions of relevant material 
standards or the requirements in the design documents.  
 
5.1.4 Low -temperature welding rods should  be retested for the percentage of moisture for covering 
or retested for the diffusible hydrogen content in deposited metals, the testing method should be in - 11 - accordance with the corresponding welding rod standards or design documents.  
 
5.2 Material segment ation  
Material segmentation consists of cold segmentation or hot segmentation methods. When using hot 
segmentation method to separate materials, any surface slag and any surface layer which may effect 
the manufacturing quality should be cleared.  
 
5.3 Mate rial symbol transplantation  
 
5.3.1 Materials used to manufacture pressure components should carry traceable symbols. During 
manufacturing process, if such an original symbol is going to be removed from the material or the 
material is planed to be cut into pieces, then the manufacturing unit should specify an expression 
method of the symbol, and complete the symbol transplantation before conducting the material 
segmentation.  
 
5.3.2 For stainless steel sheets and composite steel sheets which are corrosion -resistant, no 
embossed marking must  be used on the corrosion -resistant surfaces.  
 
5.3.3 Pressure components of low temperature pressure vessels shall not be marked by embossing 
methods.  
 
6 Cold forming, hot forming and assembly  
 
6.1 Forming  
 
6.1.1 The manuf acturing unit should according to the manufacturing processes to determine the 
machining allowances, to ensure that the actual thickness of the formed pressure components are 
not thinner than the minimum forming thickness that is stated in the design drawi ngs.  
6.1.2 Steel pressure components which were treated with normal ising, normal ising and tempering 
or quenching, should use cold forming or warm forming; when warm forming is adopted, the 
temperature range of the temper brittleness should be avoided.  
 
6.2 Surface grinding  
 
6.2.1 During manufacturing process, any mechanical damage to the surface of the material should 
be av oided. For defects such as acute wounds and local wounds, grooves suffered by the corrosion -
resistant surfaces of stainless steel press ure vessels should be ground out, the maximum gradient of 
the grinding should be 1:3, the grinding depth should not exceed 5% of the steel thickness s of that 
location, and not more than 2mm, otherwise a welding repair should be conducted.  
 
6.2.2 With regard to formed parts, welded parts of composite steel sheets and metal linings, the 
grinding depth shall not be greater than the 30% of the thickness  of the cladding layer (or deposit 
welding layer, lining) and not larger than 1mm, otherwise a welding repair should be conducted.  
 
6.3 Groove  
Grooves shall meet the following requirements:  
 
a) On the groove surfaces, there shall be no defects such as crac ks, delamination or inclusions 
allowed.  
 - 12 - b) Groove surfaces of low -alloy steel materials with a standard tensile strength lower limit 
Rm  540MPa, and the groove surfaces of Cr -Mo low -alloy steel materials after hot segmentation, 
after the completion of the processing, should according to JB  / T 4730.4 to conduct magnetic particle 
testing, Grade I should be regarded as qualified;  
 
c) Before  conducting welding, any oxide scale, greasy dirt, slag and other harmful impurities which 
are within the range of 2 0 mm (the distance from the edge of the groove) from the base material 
surface and the groove should be cleared away.  
 
6.4 Heads  
 
6.4.1 The distance between various disjoint welding cent relines of the heads should be at least 3 
times of the head steel thickness s, and not less than 100mm. When a convex head is made by the 
assembly of the formed segments and a top circular plate, the welding directions between the  
segments should be radial and circumferential, see Diagram 1.  
 
For any head which is assembled firs t formed later, the inner surface of the welds and the outer 
surface of the welds which can affect the forming quality, should be polished to be the same level as 
the base metal.  
 
 Diagram 1 The weld seam arrangement of a convex head formed by segmentati on 
 
6.4.2 Use a full size gap inner sample plate to inspect the shape deviations (see Diagram 2) of the 
inner surfaces of elliptical heads, dished heads and spherical heads. The indentation size should be 
3% – 5% D i, the maximum shape deviation for convex shall not exceed 1.25% D i, for concave shall 
not exceed 0.625% D i. The sample plate should be perpendicular to the testing surface during 
inspection. For heads shown in Figure 1 as forming first assembled alter, allow the sample plate to 
avoid the weld for  measurement.  
 
- 13 -  
 Diagram 2 The shape deviation inspection of convex heads  
 
6.4.3 For dished heads and toriconical heads, the knuckle radius of the transition zone shall not be 
less than the specified design value.  
 
6.4.4 There shall be no longitudinal fo lds permitted on the straight edges.  
 
6.5 Cylinder and shell  
 
6.5.1 The align deviation value b (see Diagram 3) for Category A, B weld joints  should meet the 
requirements in Table 1. the align deviation value b for forged and welded Category B weld joints  
should be less than 1/8 of the steel thickness s at the alignment location, and not greater than 5mm.  
 
 
 Diagram 3 The align deviation value of Category A, B weld joints  
 
Table 1 The align deviation value for Category A, B weld joints  
According to the classifica tion of the weld joints  to differentiate 
the align deviation value b  Alignment location  
steel thickness s 
Category A weld joints  Category B weld joints  
 12  1/4 s  1/4s 
> 12 – 20  3  1/4s 
> 20 – 40  3  5 
> 40 – 50  3  1/8 s  
> 50  1/16 s, and  10  1/8 s, and  20 
The circumferential joints which connect the spherical head and the cylinder, and the Category A 
butt joints which connect the embedded nozzles and the cylinder or the head,  shall be according to 
the requirements for Category B weld joints to determine the al ign deviation value.  
 
- 14 - The align deviation value b (see Diagram 4) for any composite steel sheet shall not be greater than 
5% of the cla dding thickness of this steel sheet and not more than 2mm.  
 
 
 Diagram 4 The align deviation value for Category A, B weld joints  of composite steel sheets  
 
6.5.2 The edge E formed by the circumferential and axial of welded joints , should use an internal 
sample plate (or external sample plate) with the chord length equals to D i / 6 and not less than 300mm, 
and a ruler to ch eck (see Diagram 5, Diagram 6), the E value shall not exceed ( s/10 +  2) mm, and not 
more than 5mm.  
 
Diagram 5 Circumferential edge E at welded joint  Diagram 6 Axial edge E at welded joint  
6.5.3 For Category B weld joints  and Category A weld joints  which connect the cylinders and the 
spherical heads, when the steel  thickness of both sides are not the same, if the thickness of the thinner 
plate  s1  10mm, and the thickness difference between the two plates is more than 3mm; or if the 
thickness of the thinner plate s1> 10mm, and the thickness difference between the two plates is more 
than 30%  s1, or more than 5mm, then they should according to the requirements in Diagram 7 to thin 
the edge of the thicker plate from one side or both sides, or according to the same requirements, use 
the welding method to weld the edge  of the thinner plate to be an inclined surface.  
When the thickness difference between the two plates is less than the above mentioned values, then 
the align deviation value b shall be in accordance with the requirements in 6.5.1, and the align 
deviation value b shall be determined by using the thickness of the thinner plate as the benchmark. 
When measuring the align deviation value b, the thickness difference between the two plates should 
not be included.  
- 15 -  
 
Diagram 7 The connection types of the Category B weld joints  with different thicknesses and the 
Category A weld joints  which connect the cylinders and the spherical  heads.  
6.5.4 Unless otherwise specified in the drawings, the linear tolerance of a cylinder should not exceed  
1% of the cylinder length (L ). When the shell length of a vertical pressure vessel is more than 30m, 
the linear tolerance of its cylinder shall not exceed (0.5L  / 1000)  + 15.  
Note: the inspection of the cylinder linearity is conducted by way of inspecting the horizontal and the 
vertical plane of the centre  line, the measurement is conducted by along the 0°, 90°, 180°,  270° four 
circumference locations. The distance from the measuring positions to the centre  line of the cylinder 
longitudinal weld joint should not be less than 100mm. I f the shell thickness is different, then when 
calculating the linearity, the thickness difference should be deducted.  
6.5.5 When conducting the assembly, the layout of the welded joints  on the shell should meet the 
following requirements:  
a) The outer arc length between the Category A joints of the adjacent cylindrical segments , should be 
more than 3 times of the steel thickness s, and not less than 100mm;  
b) The outer arc lengths  between the Category A butt joints on the head, the embedded Category A 
joints on the head, and the Category A joints of the cylindrical segments which are adjacent to the 
head, should all be greater than 3 times of the steel thickness s, and not less than 100mm;  
c) Among the cylinder assembly, the length of any individual cyli ndrical segment  shall not be less 
than 300mm;  
d) Not suitable to use cross welding.  
Note: The outer arc length is between the centre  lines of the welded joints , the measured distance 
along the outer surface of the shell.  
- 16 - 6.5.6 The flange facing should b e perpendicular to the spindle centre  line of the connection pipe or the 
cylinder. The assembly between the connecting components and the flange, and the shell should 
ensure the level or vertical of the flange facing (if specially required, such as the con nection pipes 
should be according to the drawings specification), the deviation shall not exceed 1% of the external 
diameter of the flange ( when the external diameter of the flange is less than 100mm, should be 
regarded as 100mm),  and not larger than 3mm.  
Flange bolt holes should be arranged across the middle with the shell main axis or the plumb  line (see 
Diagram 8). Any special requirement should be indicated on drawings.  
 
 Diagram 8 The cross -middle arrangement of flange bolt holes  
6.5.7 The base rings of vertical vessels, and the anchor bolt holes on the floor base should be 
uniformly arranged. The diameter tolerance of the centre  circle, the chord length tolerance between 
two adjacent holes, and the chord length tolerance between any two holes should n ot be more than 
± 3mm.  
6.5.8 Weldings conducted between the inner parts of a pressure vessel and the shell should try to 
avoid the Category A, B weld joints  on the shell.  
6.5.9 Any welding seam on pressure vessels which is covered by a reinforcing pad, sup port or cushion 
plates etc., should be polished to be level with the base metal.  
6.5.10 After the welding of a pressure vessel is completed, the diameter of the shell should be 
checked, the requirements are as the following:  
a) The difference between the maximum inner diameter and minimum inner diameter of a same 
section of the shell should not exceed 1% of the inner diameter D i (for forged -welded pressure vessels 
shall be 1 ‰) of this section, and not be larger than 25mm (see Diagram 9);  
b) When the dista nce between the section inspected to the opening centre  is smaller than the opening 
diameter, then the difference between the maximum inner diameter and minimum inner diameter of 
this section, should not exceed the sum of 1% of the inner diameter Di of thi s section (for forged -
welded pressure vessels shall be 1 ‰) and 2% of the opening diameter, and not be larger than 25mm.  
- 17 -  
 
Diagram 9 The difference between the maximum inner diameter and minimum inner diameter of the 
same section of a sheet  
6.5.11 After t he welding of an external pressure vessel is completed, it is necessary  according to the 
following requirements to check the roundness of the shell:  
a) Use an inner arched or outer arched sample plate (depending on the measurement points) to  
measure. The arc radius of the sample plate is equal to the inner radius or the outer radius of the shell, 
the chord length is equal to two times of the arc length specific  in Diagram 4 -14 of GB 150.3 . The 
measurement points should avoid the welded joints or other rais ed parts.  
b) The maximum positive -negative deviation e which is measured by using the sample plate along the 
shell radial shall not be greater than the maximum allowable deviation indicated in Diagram 10.  
When the intersection point of D o / e and L  / Do is located between any two curves in Diagram 10, 
then its maximum positive -negative deviation e shall be determined by the interpolation method; 
When the intersection point of D o / e and L  / Do is located above of the e = 1. 0 e curve or below the 
e = 0.2 e curve, its maximum positive -negative deviations e shall not be greater than e and 0.2 e 
value respectively.  
c) The L and D o of the cylinder and conical shells should be selected by according to the provisions of 
GB 150.3, L for the spherical shell is taken as 0.5D o; with regard to conical shell, D o should be taken 
as the outer diameter D ox of the conical shell on which the measurement point is, L is taken as L e 
(Dd/Dox), among which, the equivalent length L e should be calculated by according to formula  (5-20) 
in GB 150.3.  
- 18 -  
Diagram 10 The maximum allowable deviation of external pressure shell roundness  
6.6 Flange and flat cover  
6.6.1 Pressure vessel flanges are processed by according to JB  / T 4700 – JB / T 4703, the processing 
of pipe flanges should be  conducted in accordance with the corresponding standards.  
6.6.2 The processing of flat covers and the cylinder ends should be conducted by according to the 
following provisions:  
a) The diameter tolerance between the centre  circles  of stud hole or bolt ho le, as well as the chord 
length tolerance between two adjacent holes shall be ±  0.6mm; the chord length tolerance between 
any two holes should be according to the specifications in Table 2:  
Table 2 The chord length tolerance between any two holes of flang e stud hole or bolt hole  
Design inner diameter  
Di < 600  600 – 1200  > 1200  
Tolerance  ± 1.0 ± 1.5 ± 2.0 
b) The perpendicularity tolerance between the screw centre line and the end surface shall not exceed 
0.25%;  
c) The basic dimension and tolerances of ea ch thread should be according to the provisions in 
GB/T  196, GB/T 197;  
- 19 - d) The thread precision of a screw is a general moderate accuracy, or selected by appropriate 
standards.  
6.7 Bolts, studs and nuts  
6.7.1 Bolts, studs and nuts with nominal diameter not  bigger than M36 should be manufactured  
according to the corresponding standards.  
6.7.2 Flange studs of pressure vessel shall be according to provisions specified in JB  / T 4707.  
6.7.3 Studs and nuts with nominal diameter greater than M36, apart from mee ting the requirements 
stated in c) and d) of 6.6.2 and corresponding standards, also should meet the following requirements:  
a) Studs  which require heat treatment, its samples and tests should be in accordance with the relevant 
provisions in GB 150.2;  
b) Semi -finished nuts after been through heat treatment, should be conducted with hardness test.  
c) Studs should be conducted with surface test in accordance with JB  / T 4730, Grade I shall be 
regarded as qualified.  
6.8 Assembly and other requirements  
6.8.1 The limit deviation of the linear dimension of machined surface and non -machined surface 
should be according to the requirements of Grade m and Grade c which are specified in GB/T 1804 . 
6.8.2 During the assembly of the pressure components, must not carry  out forceful levelling .  
6.8.3 Inspections should be conducted of the main geometry dimensions  and nozzle location of 
pressure vessels, and the results should meet the drawing specifications.  
7 Welding  
7.1 Welding preparation and welding environment  
7.1.1 Store rooms for the storage of welding rods, welding fluxes and other welding materials should 
be kept dry . The relative humidity of the store rooms shall not exceed 60%.  
7.1.2 When the welding environment is in one of the following situations, and if t here is no effective 
protection measures provided, then the welding process  should be prohibited:  
a) When conducting shielded arc welding, wind speed greater than 10m/s.  
b) When conducting gas arc welding, wind speed greater than 2m/s.  
c) Relative humidit y greater than 90%.  
d) When it is snowing, or raining . 
e) When the welding environment temperature is lower than -20oC. 
7.1.3 When the temperature of a welding part  is lower than 0 °C, then within the range of 100mm of 
the welding location, should be prehea ted to above 15 °C. - 20 - 7.2 Welding procedure  
7.2.1 Before conducting welding to a pressure vessel, the welding seam of the pressure components, 
welding seam welded with pressure components, tack welding seam welded into a permanent welding 
seam, the surface b uild-up welding and patch welding of the base metal of the pressure vessel, as well 
as the re -repair welding seam of the above mentioned welding seams, all should be subjected to 
welding procedure qualifications assessment by according to JB/T 4708 or get support from the 
assessed and qualified welding procedures.  
7.2.2 Any imported material (including fillers) which is used for welding structural pressure 
components, before it is used for the first time by the manufacturing unit of the pressure vessel, th e 
material should be conducted with a welding procedure qualification assessment by according to 
JB/T  4708.  
7.2.3 For any chromium -nickel austenitic stainless steel pressure vessel with a design temperature in 
the range of  -196°C to -100°C, should be acco rding to the design temperature to select an appropriate 
welding method, and the carbon content of the base metal should be less than or equal to 0.10% of the 
chromium -nickel austenitic stainless steel; during the appropriate welding procedure qualificatio n 
assessment, should conduct the low temperature Charpy (V -notch) impact test of the welding  metal, 
the absorbing energy during the impact which is not higher  than the design temperature must not be 
less than 31J (When the design temperature is lower than -192°C, the impact test temperature should 
be regarded as -192°C).  
7.2.4 The welding procedure qualification assessment of low temperature pressure vessels, should 
include the low temperature Charpy (V -notch) impact test on the weld seam and the heat affe cted 
zone. The sampling method of the impact test should be determined by according to the requirements 
specified in JB/T  4708.  
Impact test temperature should not exceed the test temperature which is indicated in the design 
drawings. When the base metal on  both sides of a welding seam have different impact test 
requirements, the low -temperature impact energy should be the lower value of the tensile strength  of 
the base metal on both sides and should be consistent with the requirements indicated in the desig n 
drawings or Table 1 of GB150.2. The tensile and bending performances of the joints should be 
consistent with the lower requirement of the base metal on both sides.  
7.2.5 The welding of low -temperature pressure vessels should strictly control the heat in put. Within 
the range determined in the welding procedure qualification assessment, should select a smaller 
welding heat input, and the selection of multi -channel welding shall be more appropriate.  
7.2.6 The steel stamp of the welder code should be marked  at the designated place near the welded 
joint of the pressure components, or record the steel stamp of the welder code in the welding records 
which also records the arrangement of the welding seam. Among them, on the corrosion -resistant 
surfaces of low -temperature pressure vessels and stainless steel pressure vessels,  the marking of the 
steel stamp must not be used.  
7.2.7 The technical files of welding procedure qualification assessment should be kept until this 
procedure qualification is invalid, the tes t specimens for the assessment of the welding procedure 
qualification should be preserved for at least 5 years.  
7.3 Dimension, shape and appearance of weld seam surface  
7.3.1 The weld seam reinforcement e 1, e2 of Category A and Category B weld joints  shou ld be in - 21 - accordance with the specifications in Table 3 and Diagram 11.  
Table 3 Compliance indexes of weld seam reinforcement for Category A and Category B weld joints  
Low-alloy steel material with R m  540MPa, Cr -
Mo low -alloy steel material  Other steel ma terial, mm  
Single groove  Double groove  Single groove  Double groove  
e1 e2 e1 e2 e1 e2 e1 e2 
0% – 10% s 
and  3 0 – 1.5 0% – 10% 1 
and  3 0% – 10% 2 
and  3 0% – 15% s 
and  4 0 – 1.5 0% – 15% 1 
and  4 0% – 15% 2 
and  4 
 
7.3.2 The fillet weld size of Category C, Category D weld joints , if not specified in the drawings, 
should take the thickness of the thinner weld part. For the fillet weld of the reinforcing pad, when the 
thickness of the reinforcing pad is not less than 8mm, then the fillet weld size should be equal to 70% 
of the thickness of the reinforcing pad, and not less than 8mm.  
7.3.3 The surfaces of the welded joints should be conducted with visual inspection in accordance with 
relative standards, there should be no surface cracks, incomplete penetration, incomplete fusion, 
surface pores, craters, not filled, slags and spatters; the transition between the welding seam and the 
base metal should be smooth; the outer of fillet welds should be a smooth concave transition.  
7.3.4 There should be no undercut on the welded surfaces of the following pressure vessels:  
 
 Diagram 11 The weld reinforcement of Category A and Category B weld joints   
a) Low -alloy steel pressure vessels with a standard tensile strength lower limit R m  540MPa;  
b) Pressure vessels made of Cr -Mo low -alloy steel;  
c) Pressure vessels made of stainless steel;  
d) Pressure vessels bear cyclic  loads;  
e) Pressure vessels with stress corrosion;  
f) Low -temperature pressure vessels;  
g) Pressure vessels with we ld joint coefficient  as 1.0 (except pressure vessels made of seamless steel 
- 22 - tubes).  
The undercut depth of the weld seam surface of other pressure vessels shall not exceed 0.5mm, the 
continuous length of the undercut shall not exceed 100mm, the total len gth of the undercut on both 
sides shall not exceed 10% of the weld seam length.  
7.4 Welding repairing  
7.4.1 When a weld repair is necessary, then its repair process should be consistent with the relevant 
provisions in 7.2.  
7.4.2 The times of weld repair at the same area should not be more than 2 times. If more than 2 times 
are required, then before repairing, should have obtained an approval from the technical director of 
the manufacturing unit, the times of repairing conducted, the location and the repai ring situation 
should be recorded into the quality certificate.  
7.4.3 The following pressure vessels after the post weld heat treatment, if need to conduct weld 
repairing, then the repair areas should be conducted with heat treatment again:  
a) Pressure v essels used to contain media with extreme toxicity or high hazard;  
b) Cr-Mo steel pressure vessels;  
c) Low -temperature pressure vessels;  
d) Pressure vessels indicated in the drawings with stress corrosion.  
7.4.4 After the heat treatment, any required weld  repairing should be with the user's consent. Except 
the pressure vessels specified in 7.4.3 requires post weld heat treatment, if repairing is conducted after 
the heat treatment, and when the repair depth is less than 1/3 of the steel thickness s, and no t larger 
than 13mm, then it does not have to be conducted with post weld heat treatment. When conducting 
repair welding, should preheat and control the thickness of each welding layer is no greater than 3mm, 
and the temp er bead technique should be used.  
When repairing both sides of the same section, the repair depth should be the total of the  repaired 
depth on both sides.  
7.4.5 Pressure vessels or pressure components with special corrosion -resistant requirements, the repair 
area needs to be not less than t he original corrosion resistance.  
8 Heat treatment  
8.1 Heat treatment for the property restore of formed pressure components  
8.1.1 When any cold formed steel pressure component meet any one of the following from a) – e) 
conditions, and if its deformation rate has exceeded the range specified in Table 4, then after the 
component is formed, a corresponding heat treatment used to restore the properties of the material 
should be conducted.  
a) Pressure vessels used to contain extremely toxicity or highly hazar dous media;  
b) Pressure vessels indicated in the drawings with stress corrosion;  - 23 - c) For carbon steel and low -alloy steel, before fo rming, its thickness is greater than 16mm;  
d) For carbon steel and low -alloy steel, before forming, its thinning deduction is  greater than 10%;  
e) For carbon steel and low -alloy steel which is required to be conducted with impact test.  
Table 4 Control index of deformation rate for cold formed parts  
Material  Carbon steel, low -alloy steel 
and other materials  Austenitic stainless s teel  
Deformation rate (%)  5 15note 
Calculation of deformation rate:  
Uni-axial tension (such as cylinder forming, see Diagram 12): deformation rate (%) = 50 [1-
(Rf/R0)]/R f 
Bia-axial tension (such as heads forming, see Diagram 12): deformation rate (%) =  75[1-
(Rf/R0)]/R f 
In the formulas:  
 ---- Thickness of the sheet material, mm;  
Rf ----- Radius of middle surface after formed, mm;  
R0 ----- Radius of middle surface before forming (for flat sheet is ), mm. 
Note: When design temperature is lower than -100oC or higher than 675oC, the control value of the 
deformation rate is 10%.  
 
 Diagram 12 Uni -axial tension and bia -axial tension forming   
8.1.2 When cold forming is completed in steps, if the intermediate heat treatment is not conducted, 
then the deformat ion rate shall be the total of the deformation rate of each step; if the intermediate 
heat treatment is conducted, then the total of the deformation rate before the heat treatment and after 
the heat treatment should be calculated respectively.  
8.1.3 If th e deformation residual stress of a warm formed workpiece is required to be eliminated,  then 
- 24 - the heat treatment process should be conducted by according to the conditions and requirements for 
heat treatment of cold formed workpieces specified in 8.1.1.  
8.1.4 If the hot forming or warm forming has changed the heat treatment state of the material 
supplied, then more heat treatment should be conducted again to recover the heat treatment state of 
the material supplied.  
8.1.5 When there is any special requiremen t on the heat treatment of the forming temperature and the 
heat treatment state to recover the materials supplied, the procedure should be in accordance with the 
provisions specified in the relevant standards, regulations or design documents.  
8.2 Post wel d heat treatment (PWHT)  
Pressure vessels and its pressure components should be determined whether a post weld heat 
treatment is required by according to the materials, the welded joint thickness (the thickness after the 
post weld heat treatment, PWHT) and the design requirements of the said object.  
8.2.1 The thickness of a welded joint shall be determined by according to the following provisions:  
a) For equal thickness full penetration butt joints, shall be the steel thickness;  
b) For butt weld s and fillet welds should be the weld seam thickness;  
c) For combined welds should be the greater value of the thickness of the butt weld or the fillet weld;  
d) When welding components with different thickness:  
---------- For unequal thickness butt joints  should take the thickness of the thinner steel components;  
---------- For Category B weld joints  such as the shell and tube plate, the flat head, cover, and other 
similar components should take the shell thickness.  
---------- When welding the shell and the  connection pipes, should take the greater value of the neck 
thickness of the connection pipe, the shell thickness, the reinforcing pad and the thickness of the 
connecting fillet welding seam;  
---------- When welding a flange and the connection pipes, shou ld take the neck thickness of the 
connection pipe at the joint; for structures which are demonstrated in the Diagram 7 -1 g) of GB150.3, 
should take the flange thickness;  
---------- For inner heads connecting structures which are demonstrated in Diagram D.1 2 b) of 
Appendix D of GB150.3, should take the greater value from the thickness of the cylinder or the head;  
--------- When welding non -pressure components and pressure components, should take the weld seam 
thickness.  
8.2.2 Where a pressure vessel and its  pressure components meet one of the following conditions, a 
post weld heat treatment should be conducted, the post weld heat treatment should include the 
connection welding seams between the pressure components as well as the connection welding seam 
betwe en the pressure components and the non -pressure components. When drawing up the technical 
requirements for the heat treatment, in addition of meeting the following requirements, some 
necessary measures to avoid reheat cracking caused by the post weld heat treatment should also be - 25 - taken.  
8.2.2.1 Where the thicknesses of the welded joints meet the specifications in Table 5;  
Table 5 Welded joint thickness in need of conducting post weld heat treatment  
Material  Welded joint thickness  
Carbon steel, Q345R, Q3 70R, P265GH, 
P355GH, 16Mn  > 32mm  
> 38mm (weld preheating above 100oC) 
07MnMoVR, 07MnNiVDR, 07MnNiMoDR, 
12MnNiVR, 08MnNiMoVD, 10Ni3MoVD  > 32mm  
> 38mm (weld preheating above 100oC) 
16MnDR, 16MnD  > 32mm  
20MnMoD  > 20mm (low -temperature pressure vessels with  
design temperature not lower than -30oC) 
Any thickness (low -temperature pressure vessels 
with design temperature lower than -30oC) 
15MnNiDR, 15MnNiNbDR, 09MnNiDR, 
09MnNiD  > 20mm (low -temperature pressure vessels with 
design temperature not lower than -45oC) 
Any thickness (low -temperature pressure vessels 
with design temperature lower than -45oC) 
18MnMoNbR, 13MnNiMoR, 20MnMo, 
20MnMoNb, 20MnNiMo  Any thickness  
15CrMoR, 14cR1MoR, 12Cr2Mo1R, 
12Cr1MoVR, 12Cr2Mo1VR, 15CrMo, 
14Cr1Mo, 12Cr2Mo1, 12Cr1MoV , 12Cr2Mo 1V, 
12Cr3Mo1V, 1Cr5Mo  Any thickness  
S11306, S11348  > 10mm  
08Ni3DR, 08Ni3D  Any thickness  
8.2.2.2 Pressure vessels indicated in the drawings with stress corrosion.  
8.2.2.3 Carbon steel, low -alloy steel pressure vessels used to contain extremely toxicity o r highly 
hazardous media;  
8.2.2.4 When otherwise specified in relevant standards or drawings.  
8.2.3 For welded joints between dissimilar steels, should be according to the steel with higher 
requirements on heat treatment to determine whether or not the pos t weld heat treatment is needed.  
8.2.4 When it is required to conduct the post weld heat treatment to austenitic stainless steel, austenite 
- ferrite stainless steel, the process should be according to the requirements specified in the design 
documents.  
8.2.5 Unless specifically stated in the design documents, otherwise weld joints made of austenitic 
stainless steel or austenitic -ferritic stainless steel do not have to be conducted with heat treatment.  
8.2.6 Post weld heat treatment requirements  
8.2.6.1 Th e manufacturing unit should according to the design documents and standards to formulate - 26 - a heat treatment technique before conducting the heat treatment.  
8.2.6.2 Coal -fired furnaces shall not be used for post weld heat treatment.  
8.2.6.3 Heat treatment un it (furnace) should be equipped with a temperature thermometer which can 
automatically record the temperature curve, the thermometer should be able to draw the relation curve 
between the heat treatment time and the wall temperature of the workpiece  automat ically.  
8.2.6.4 Whole post weld heat treatment can be the heating method in a furnace as a whole or the 
heating method in a pressure vessel. Where possible, the heat method inside a furnace as a whole 
should be priority; when can not be heated as a whole, then section heating should be permitted. 
When conducting the section heat treatment, the length where is repeatedly heated should not be less 
than 1500mm, and insulation measures should be taken at the adjacent areas, in order to ensure that 
the temperatu re gradient will not affect the texture and properties of the material. The operating of the 
heat treatment should comply with the provisions in 8.2.7.  
8.2.6.5 For Category B, C, D, E weld joints , spherical heads and cylindrical joints as well as repairin g 
area of welding defects, shall be allowed to use the local heat treatment. The effective heating area of 
the local heat treatment shall meet the following requirements:  
a) Add PWHT or 50mm on the maximum width of the weld seam on each side respectively , take the  
greater value;  
b) Add PWHT or 50mm on the direction of the repaired weld end , take the greater value;  
c) When welding the connection pipes and the shell, should heat up  around the entire circumference 
of the cylinder including the connection pi pes, and in the direction which is perpendicular to the weld 
seam from the edge of the weld seam to add PWHT or 50mm, take the greater value.  
The effective heating range of local heat treatment should ensure that no harmful deformation can 
happen, when i t is unable to effectively control the deformation, then the heating scope should be 
expanded, such as carry out heating to the whole circumference of the cylinder; meanwhile, the areas 
which are near to the heating zone should be conducted with insulation  measures, in order to ensure  
the temperature gradient will not affect the texture and properties of the material.  
8.2.6.6 When conducting heat treatment to a composite steel pressure vessel and its pressure 
components, measures should be taken to ensure t hat the pressure vessel (especially the properties of 
the cladding layer material) meets the application requirement.  
8.2.7 Procedure for post weld heat treatment  
8.2.7.1 The procedure for the post weld heat treatments of carbon steel and low -alloy steel  should 
comply with the following provisions:  
a) When the weldment enters the furnace, the furnace temperature must not be higher than 400 °C; 
b) When the temperature of the weldment  has increased to 400 °C, the temperature rising rate of the 
heating zone s hall not exceed 5500/ PWHT°C / h, it must not exceed 220 °C / h, and not lower than 
55°C / h under normal circumstances;  
c) During temperature increasing, the temperature difference within 4600mm length of the heating 
zone must not be greater than 120 °C;  - 27 - d) During temperature maintaining, the temperature difference between the highest and lowest should  
not exceed 80 °C;  
e) During temperature increasing and maintaining, should control the atmosphere of the heating area, 
to prevent over -oxidation of the weld ment surface;  
f) When furnace temperature is higher than 400 °C, the temperature cooling speed of the heating zone 
shall not exceed 7000/ PWHT°C / h, it must not exceed 280 °C / h, and shall not be lower than 55 °C / h 
under normal circumstances;  
g) When taking the weldment  out of the furnace, the furnace temperature must not be higher than 
400°C, the weldment shall be cooled in still air aft er being taken out of the furnace;  
8.2.7.2 The post weld heat treatments for S11306, S11348 ferrite stainless steel should be conducted 
by according to the requirements in 8.2.7.1. In which, for f) and g), when the temperature is higher 
than 650 °C, the coo ling speed must not be greater than 55 °C / h, when the temperature is below 
650°C, the cooling speed should be fast.  
8.3 Heat treatment to improve material  mechanical properties  
Heat treatments carried out by the manufacturing units of the pressure vessel s or pressure components 
to improve the mechanical properties of the materials, should be conducted on the basis of the heat 
treatment technique requirements specified in the design documents. The heat treatment for the 
sample sheet of the base metal shoul d be (or pressure components) in a same furnace with the 
pressure vessel.  
8.4 Other heat treatments  
When the use state of the heat treatment of the materials and the state of the heat treatment of the 
goods supplied are required to be consistent, then the  state of the heat treatment of the goods supplied 
must not be changed, otherwise a reheat treatment should be conducted again.  
8.5 Surface treatment before and after heat treatments  
The surfaces of any stainless steel and composite  steel pressure vessel which has corrosion -resistant 
requirements, any dirt and harmful media on the stainless steel surface should be removed before the 
heat treatment. After conducted heat treatment to components made of such materials by according to 
the requirements specifie d in the design documents, treatments of pickling and passivation should also 
be conducted.  
9 Test sample and specimen  
9.1 Product weld sample  
9.1.1 Preparation conditions for specimen of welding product  
9.1.1 .1 Where a pressure vessel meets one of the fo llowing conditions and has Category A 
longitudinal weld joints, should be prepared for product weld specimen for each unit of product:  
a) Pressure vessels used to contain extremely toxic or highly hazardous media;  
b) Pressure vessels made of low -alloy stee l with the a standard tensile strength as R m  540MPa;  - 28 - c) Low -temperature pressure vessels;  
d) During fabrication, steel pressure vessels through heat treatment to improve or restore the material 
properties;  
e) Indicated in the design document, that the pressure vessel is required to be prepared with product 
weld specimens.   
9.1.1.2 Except when it is indicated in the drawings for the preparation of the forensic specimen ring, 
the Category B weld joints, Category A weld joints connecting spherical heads an d cylinders are 
exempt from preparing product weld specimens.  
9.1.2 Requirements for the preparation of the test samples and specimens for product welding.  
9.1.2.1 Welding process on the product welding specimen should be conducted on the extension part 
of the longitudinal seam of the cylindrical segment and on the cylindrical segment at the same time 
(except spherical pressure vessels).  
9.1.2.2 Specimen shall be taken from qualified raw materials, and has the same standard, same 
trademark, same thickness  and the same heat treatment state as the pressure vessel materials.  
9.1.2.3 The welding of the specimen should be conducted by the welders of this pressure vessel, using 
the same conditions, processes and welding technologies (including the welding and t he heat 
treatment conditions after the welding) of the welded pressure vessel. Where a pressure vessels has a 
requirement for heat treatment, its specimen should go through the heat treatment with the pressure 
vessel, otherwise measures should be taken to ensure that heat treatment for the specimen is 
conducted by according to the same heat treatment technologies as the pressure vessel.  
9.1.2.4 The size and cutting of the specimen should be according to the provisions specified in 
JB/T  4744. If an impact t est is required, test samples for the impact test should be intercepted from the 
specimen, and conduct the impact test.  
9.1.3 Inspection and evaluation of the specimen  
9.1.3.1 The inspection and evaluation of the specimen should be according to the requir ements 
specified in JB/T 4744 and the design documents.  
9.1.3.2 When the conduction of a corrosion resistance test is required, should prepare specimen by 
according to the relative standards and design documents, carry out the test,  and meet the 
requireme nts. Among which, the detecting susceptibility to intergranular corrosion in stainless steel  
should be conducted by according to provisions specified in GB/T 21433.  
9.1.3.3 For low -temperature pressure vessels, unless otherwise specified, the impact test should 
include the weld seam metal and heat affected zone, and according to the test temperature and 
compliance index which are specified in JB/T 4744 and the design documents to carry out inspection 
and evaluation.  
9.1.3.4 Unless otherwise specified, the  compliance index of the impact test for weld seam metal of 
austenitic steel shall be the impact absorbing energy and not less than 31J.  
9.1.3.5 When the specimen evaluation results can not meet the requirements, shall be allowed to take 
samples for reins pection by according to the requirements specified in JB/T 4744. If the reinspection - 29 - results still not meet the requirements, then the product represented by the specimen should be 
regarded as unqualified.  
9.2 Base metal heat treatment specimen  
9.2.1 Prep aration conditions of the specimen for the heat treatment of the base metal   
9.2.1.1 When one of the following conditions is met, then specimens for the base metal heat treatment 
should be prepared:  
a) Circumstances  where the use state of the heat treatme nt of the materials and the state of the heat 
treatment of the goods supplied are required to be consistent, and the state of the heat treatment of the 
goods supplied is changed during  the fabrication process, and requires conduct ing the heat treatment 
again.  
b) During the fabrication process, circumstances wh ich require heat treatment to improve the 
mechanical properties of the material;  
c) For cold formed or warm formed pressure components, circumstances where , after forming, require  
heat treatment to re store the material properties.  
9.2.2 Preparation requirements of the specimen and test sample for the heat treatment of the base 
metal  
9.2.2.1 The specimen for the heat treatment of the base metal should be together with the base metal 
specimen in a same  furnace to have heat treatment; when the same furnace heat treatment cannot be 
provided, then a heat treatment state which is the same as the base metal should be simulated.  
9.2.2.2 The size of the specimen can be determined by according to the requiremen ts specified in 
JB/T  4744. The specimens for the heat treatment of the base metal should be one sample for the 
tensile test, one sample for the cold -bending test and three samples for the impact test.  
9.2.3 Specimen inspection and evaluation  
The tensile test, cold -bending test and impact test of the specimen should be conducted according to 
provisions specified in GB/T  228, GB/T  232 and GB/T  229, and according to the requirements 
specified in GB150.2 and the design documents to carry out evaluation. When the evaluation results 
of the specimen cannot meet the requirements, then resampling and retest should be permitted. If the 
retest results are still below standard, then this specimen represented base metal should be regarded be 
unqualified.  
9.3 Forensics  ring of the Category B weld joints  
9.3.1 According to the provisions specified in the design documents to determine whether or not the 
forensics ring for the Category B weld joints of pressure vessels are required to be prepared.  
9.3.2 Forensics ring  shall be taken from qualified materials, and has the same steel grade, same heat 
treatment state as the materials of the pressure vessel . In the case of forgings, its forging level should 
also be the same. Where pressure vessels with heat treatment requirement , the forensics ring should 
also be conducted the same heat treatment.  
9.3.3 The type, size, quantity, cutting and the test methods and the results evaluation of the forensic  - 30 - specimen ring should be in accordance with the requirements specified in the desi gn documents.  
9.4 Other sample and specimen  
9.4.1 Pressure vessels or pressure components which are required to undertake corrosion resistance 
tests, should be according to the provisions specified in the design documents to prepare the test 
samples for t he corrosion resistance test and carry out inspections and evaluations.  
9.4.2 If according to the requirements in the design documents, any stud is required to undertake the 
mechanical property test after heat treatment, then test samples for the heat tre atment should be  
prepared as batches and inspection and evaluation  carried out . Each batch refers to the same type of 
studs which are feed at the same time and with the same steel grade, the same furnace tank number, 
the same section size, the same manufac turing process.  
9.5 Specimen combined preparation  
Where a pressure vessel is requested to prepare product welding specimen and also the base metal  
heat treatment specimen, then by ensuring the representation of both situations, the combined 
preparation of the specimen can be conducted.  
10 Non -destructive testing  
10.1 Selection of non -destructive testing methods  
10.1.1 The butt joints of pressure vessels should be tested by using the techniques of radiographic 
testing or ultrasonic testing, the ultrasonic te sting technique including time of flight diffraction 
technique (TOFD), recordable ultrasonic pulse reflection technique  and the unrecordable ultrasonic 
pulse reflection technique.  
10.1.2 When the unrecordable ultrasonic pulse reflection technique was used for the detection, the 
radiographic testing technique or the time of flight diffraction testing technique should also be us ed as 
an additional local detection.  
10.1.3 The surfaces of the weld joints of ferromagnetic pressure vessels should be tested by usi ng the 
magnetic particle testing technique.  
10.2 Implementation time of the non -destructive testing  
10.2.1 The weld joints of pressure vessels, after passed the visual inspection on shapes and sizes, 
appearance, should be conducted with non -destructive tes ting.  
10.2.2 Formed heads should be conducted with non -destructive testing.  
10.2.3 Materials having a tendency of delayed crack (such as: 12Cr2Mo1R) should be conducted with 
a non -destructive testing at least 24h after the completion of the welding, mate rials having a reheat 
crack tendency (such as: 07MnNiVDR) should be conducted with one more time of the non -
destructive testing after the heat treatment.  
10.2.4 Low -alloy steel pressure vessels with a standard tensile strength lower limit R m  540MPa , 
after the pressure test, should also conduct the surface non -destructive testing to the weld joints.  
10.3 Radiographic testing and ultrasonic testing  - 31 - 10.3.1  Full radiographic (100%) testing or ultrasonic testing  
Where pressure vessels or pressure components me et one of the following conditions,  according to 
the methods specified in the design documents, the full radiographic (100%) test should be conduct ed 
or ultrasonic test to Category A and B weld joints:  
a) Type III pressure vessels with design pressure gre ater than or equal to 1.6MPa;  
b) Pressure vessels us ing gas pressure test or gas and hydrostatic combined pressure test;  
c) Pressure vessels with weld joint coefficient as 1.0;  
d) Pressure vessels which are unable to be conducted with an internal examinati on after use;  
e) Pressure vessels which are used to contain media with extreme toxic or high hazard;  
f) Low -temperature pressure  vessels with design temperature below -40°C or low -temperature 
pressure vessels with the weld joint thickness greater than 25 mm; 
g) The weld joint thickness of austenitic stainless steel, carbon steel, Q345R, Q370R and supporting 
forgings thicker than 30mm;  
h) The weld joint thickness of 18MnMoNbR , 13MnNiMoR , 12MnNiVR  and supporting forgings 
thicker than 20mm;  
i) The weld join t thickness of 15CrMoR , 14Cr1MoR , 08Ni3DR,  austenitic -ferritic stainless steel  and 
supporting forgings thicker than 20mm;  
j) Ferritic stainless steel, other Cr -Mo low alloy steel pressure vessels;  
k) Low -alloy steel pressure vessels with a standard tensil e strength lower limit  Rm  540MPa;  
l) Pressure vessels indicated in drawings to require 100% inspection;  
Note: For the above mentioned pressure vessels with butt joints between one connection pipe and 
another connection pipe with nominal diameter  DN  250mm,  the inspection requirements forthe butt 
joints of the connection pipe and high neck flange  are the same as the inspection requirements for 
Category A and Category B weld joints.  
10.3.2 Local radiographic testing and ultrasonic testing  
Except for pressure vessels which are not specified in 10.3.1, the Category A and Category B weld 
joints should be conducted with  local radiographic testing and ultrasonic testing. The testing method 
should be according to the design documents. Among them, the testing le ngth of the low -temperature 
pressure vessel shall not be less than 50% of the length of all weld joints, the testing length of non -
low-temperature pressure vessels shall not be less than 20% of the length of all weld joints, and shall 
not be less than 250m m.  
For t he locations listed in following section a) – e), the cross section of the weld seam should be 
conducted with 100% inspection, among which the testing length of section a), b), c) and the cross -
section of the weld seam can  be included into the loc al test length  
a) All connection joints on the convex heads which are assembled first formed later;  - 32 - b) All weld joints which are covered by reinforcement ring, bearing, cus hion plate or inner pieces;  
c) For connection pipes meet ing the requirements with no  further reinforcement specified in 6.1.3 of 
GB 150.3, from the p eening centre  the minimum length along the surface of the pressure vessel is 
equal to the weld joints within the range of opening diameter;  
d) Butt weld joints between embedded connection pip es and the cylinder or head;  
e) The butt joints between the connection pipes which bear external load and with the nominal 
diameter as DN  250mm, and the butt joints between connection pipes and the welding neck flanges;  
Note: after conduct ing the testin g required by this section, the manufacturing unit is still responsible 
for the quality of the sections which are not inspected. However, i f further testing find s a few pores 
which are standard defects but do not endanger the safety of the pressure vessel,  if such defects are 
not permitted then the full radiographic (100%) testing or ultrasonic testing should be selected.  
10.3.3 The testing requirements for the butt joints between the connection pipes with the nom inal 
diameter as DN  250mm, and the butt joints between connection pipes and the welding neck flanges 
should according to the design documents.  
10.3.4 The last closed circumferen tial weld seam between the cylinder of a pressure vessel with 
diameter  not ex ceeding 800mm and the head, when a single welded but joints with no cushion plate is 
used, and the techniques of radiographic testing or ultrasonic testing can not be conducted, then 
testings are permitted not to be carried out, but the closed weld seam sh all be subjected to gas welding 
backing.  
10.4 Surface testing  
If a weld joint meets one of the following conditions, then an  inspection of magnetic particle testing 
or penetrant testing is required to conduct to the surface of the weld joint according to the method 
specified in the drawings:  
a) For Category A, B, C, D and E weld joints on medium -temperature and low -temperature pressure 
vessels which are stated in 10.3.1,  the surfaces of defects grinding or welding repairing, the cutting 
marks of the surfa ces of demolition places such as clamping and stretching;  
b) Category C, D and E weld joints belong to the pressure vessels stated in i), j), k) of 10.3.1;  
c) Dissimilar steel weld joints, and weld joints with a tendency of reheat cracking or tendency of 
delayed cracking;  
d) The butt joints and fillet joints of austenitic stainless steel and austenitic -ferritic stainless steel 
pressure vessels with a steel thickness greater than 20mm.  
e) Build -up welding surfaces;  
f) Clad weld joints of composite steel sh eets;  
g) The surfaces defects grinding or weld repairing of low -alloy steel pressure vessels with lower limit 
of standard tensile strength R m  540MPa, and the surface defects grinding or weld repairing of Cr -
Mo low -alloy steel pressure vessels, as well as the cutting marks of the surfaces of demolition places 
such as clamping and stretching;  - 33 - h) The butt joints between the connection pipes where  the Nominal Diameter DN<250mm, and the 
butt joints between the connection pipes and neck flanges on pressure vessels which require full 
radiographic (100%) testing or ultrasonic testing;  
i) All convex head assembling joints on pressure vessels which are a ssembled first and formed later 
and are required for the inspection of local radiographic testing and ultrasonic testing;  
j) Pipe angle seams specified in design documents for inspection;  
10.5 Combination testing  
10.5.1 For a ll Category A and B weld join ts of low -alloy steel pressure vessels with a  standard tensile 
strength lower limit Rm   540MPa,  if the weld joint thickness is greater than 20mm, then a testing 
technique which is different from the original non -destructive testing technique listed in 10. 1 should 
be used to carry out local testing . This test should include all cross weld areas; meanwhile, after this 
type of pressure vessels under went the pressure test, non -destructive testing should also be conducted 
on the weld joints.  
10.5.2 For weld jo ints after undergoing radiographic testing or ultrasonic testing, if any unallowable 
defects appear, then welding repair s should be conducted after cleaning the defects, and use the 
original test method to carry out re -examination of these parts until it passes ;  
10.5.3 For weld joints after undergoing through local inspection, if any unallowable defects appear,  
then increase the inspection length at the extended part of both ends of the defect . The increased 
length should be 10% of this weld joint length,  and both sides shall not be less than 250mm. If the 
unallowable defect still exists, then a full inspection should be conducted on this weld joint.  
10.5.4 Unallowable defects which are detected by particle testing and penetrant testing, after  any 
necessar y grinding and welding, should use the original test technique to carry out retesting of this 
part until it is satisfactory .  
10.5.5 If it is specified by design documents, combination testing should be carried out according to 
the provisions.  
10.6 Technic al requirements for non -destructive testing  
10.6.1 Technical requirements for radiographic testing  
Carry out radiographic testing to weld joints according to JB/T  4730 . See Table 6 for its compliance 
index.  
10.6.2 Technical requirements for ultrasonic test ing 
Carry out ultrasonic testing to weld joints according to JB/T  4730, see Table 6 for its compliance 
index.  
Table 6 Compliance indexes for radiographic testing and ultrasonic testing  
Testing method  Test technical 
grade  Testing range  Compliance 
grade  
Radiographic testing  AB Category A, B Full  II - 34 - joints  Local  III 
Fillet joints, T shape joints  II 
Full  I Category A, B 
joints  Local  II Pulse 
reflection 
method  B 
Fillet joints, T shape joints  I Ultrasonic 
testing  
Time of flight 
diffraction  / / II 
 
10.6.3 Technical requirements for surface testing  
Carry out magnetic particle testing,  and penetrant testing to weld joints . According to JB/T  473, the 
compliance index shall not be lower than Grade I.  
10.6.4 Technical requirements for combinatio n testing  
When a combination test of radiographic testing and ultrasonic testing is used, the quality requirement 
and compliance grade shall be determined by its own standards respectively, and all should be 
qualified.  
10.7 Non -destructive testing files  
The files of non -destructive testing for pressure vessels should be complete, the retention time of 
these files shall not be shorter than the design service life of the pressure vessel.  
11 Pressure test and leak test  
11.1 Fabricated pressure vessels shall be  subject to a  pressure test and leak test according to the design 
documents.  
11.2 During pressure test and leak test s, if the test pressure is measured with a pressure gauge, then 
two qualified pressure gauges with the same range should be used. The range of the pressure gauges 
should be 1.5 to 3 times the test pressure, ideally  2 times the test pressure. The accuracy of the 
pressure gauges shall not be less than Grade 1.6, the dial diameter shall not be less than 100mm.  
11.3 The opening reinforcement ring  of a pressure vessel should be checked for its weld joint quality 
with 0.4MPa – 0.5MPa compressed air before tests.  
11.4 Pressure test  
11.4.1 The p ressure test is divided into hydrostatic pressure test, gas pressure test, gas and hydrostatic 
combined pres sure test, according to the method specified in the design documents to carry out  the 
pressure test.  
11.4.2 The test pressure and necessary  strength of the pressure test should be checked by according to 
the requirements in GB 150.1  
11.4.3 Before the pressure test, the fasteners used to connect the pressure vessel parts should be 
ensured to be fully equipped and properly fastened; any temporary pressure components fitted - 35 - especially for the pressure test, should be ensured of their safety by taking appropri ate measures.  
11.4.4 The pressure gauges used for the test should be installed at the top position of the pressure 
vessel under test.  
11.4.5 During the pressure test, the pressure  must not be continuously increase d to maintain a constant 
pressure . During  the test process the pressure components  must not be equip ped with any pressure 
fastener or external forces  impose d. 
11.4.6 Any repair which is carried out after a pressure test, if a pressure vessel repair depth is more 
than half of the vessel wall thick ness, then a re -pressure test should be conducted.  
11.4.7 For a p ressure test where the multi -cavity pressure vessel is formed by two (or more than two) 
chambers,  the test shall comply with the requirements specified in 4.6.1.7 of GB 150.1 and the design 
documents.  
11.4.8 Jacketed pressure vessels should be conducted with an inner cylinder hydrostatic pressure test, 
until the test is qualified then welding the jacket, then a hydrostatic pressure test conduct ed again in 
the inside of  the jacket.  
11.4.9 Hyd rostatic pressure test  
11.4.9.1 Usually use water as the test liquid . After qualifying the test, the water should be drained and 
the pressure vessel should be blow dried immediately in case water is not able to be completely 
drained or dried . For austeniti c stainless steel pressure vessels, the chloride ion content in the water 
should be controlled to be no more than 25mg  / L.  
11.4.9.2 When necessary, other test liquids which will not lead to any hazards may also be used, but 
the temperature of the liquid during the test should be lower than the flash point or boiling point of the 
liquid, and some reliable safety measures should also be provided.  
11.4.9.3 Test temperature  
When conducting hydrostatic pressure test to Q345R, Q370R, 07MnMoVR pressure vessels,  the 
temperature of the test liquid must not be lower than 5 °C; when conducting hydrostatic pressure test s 
to other carbon steel and low -alloy steel pressure vessels, the temperature of the test liquid must not 
be lower than 15 °C; the temperature of the te st liquid for low -temperature pressure vessels during 
hydrostatic pressure test should not be less than the temperature of the impact test for the shell 
material and the weld joints (take the greater value) plus 20 °C. If the nil -ductility transition 
temper ature of the material is increased due to the factor of material thickness, then the test 
temperature should be appropriately increased.  
When it is supported by test data, then a lower temperature liquid can be used to carry out the test, but 
during the te st, the test temperature should be ensured (the metal temperature of the pressure vessel 
wall) to be 30oC higher than the  nil-ductility transition temperature of the wall metal of the pressure 
vessel.  
11.4.9.4 Test procedures and steps  
a) Inside the test p ressure vessel, any gas should be completely discharged and filled with liquid . 
During the test process,  the observation surface of the test pressure vessel should be kept dry;  - 36 - b) When the metal temperature of the test pressure vessel wall is near to the liquid temperature, then 
the pressure can be slowly increased to the design pressure, after confirming that there is no leakage, 
then continu ously increase the pressure to the required test pressure . The time to maintain the pressure 
should be generally no t less than 30min; and then the pressure should be decreased to the design 
pressure, and maintain the pressure to a sufficient length of time for inspection ; the pressure should 
remain unchanged during the inspection.  
11.4.9.5 Compliance criteria for hydr ostatic test  
During the test process, the pressure vessel has no leakage, no visible deformation and abnormal 
noise.  
11.4.9.6 After complet ing the hydrostatic pressure test, the liquid inside the pressure vessel should be 
drained and should use compressed  air to blow dry the inside of the pressure vessel.  
11.4.10 Gas pressure test, gas and hydrostatic combined pressure test  
11.4.10.1 Gas used in the test should be dry and clean air, nitrogen or other inert gases; the provisions 
for the  test liquid and the hydrostatic pressure test should be the same.  
11.4.10.2 The gas pressure test and the gas and hydrostatic combined pressure test should be provided 
with safety measures, the safety administration department of the test unit should send personnel to 
carry out on -site supervision.  
11.4.10.3 The test pressure and the necessary strength check should according to the provisions 
specified in GB 150.1.  
11.4.10.4 The test temperature should be according to the provisions specified in 11.4.9.3.  
11.4.10.5 During the test one should increase the pressure slowly to 10% of the required test pressure, 
maintain this temperature for 5min, and conduct initial inspection to all of the weld joints and 
connection areas; after confirming no leakage is happening, then continu e to increase the pressure to 
50% of the required test pressure; if there is no anomaly happening, then increase the pressure as10% 
of the required test pressure in steps, until the test pressure is reached, then maintain the pressure for 
10min; and then d ecrease to the design pressure, maintain the pressure for a sufficient time for the 
inspection ; during the inspection period, the pressure should remain unchanged.  
11.4.10.6 Compliance criteria for gas pressure test and gas and hydrostatic combined pressur e test  
With regard to the gas pressure test, the pressure vessel should have no abnormal sound,  no gas 
leakage should be detected with the inspection carried out by using liquid soap or other leakage 
detection liquid, no visible deformation; with regard to  the gas and hydrostatic combined  pressure 
test, the outer wall of the pressure vessel should be kept dry, after inspection  and confirmed to be no 
liquid leakage, then use soap liquid or other leakage detection liquid to exam ine that there is no gas 
leakag e, no abnormal sound, and no visible deformation.  
11.5 Leak test  
11.5.1 Pressure vessels are required to pass the pressure test before the leak test can be conducted.  
11.5.2 The l eak test includes  airtightness testing, ammonia leak testing, helium leak t esting and 
halogen leak testing . The leak test should be conducted by according to the methods and requirements - 37 - specified in the design documents.  
11.5.3 Airtightness test  
11.5.3.1 The gas used for the airtightness test should be consistent with the provis ions in 11.4.10.1.  
11.5.3.2 The test pressure of the airtightness test should be the design pressure of the pressure vessel.  
11.5.3.3 The test pressure should be increased slowly, it should be maintained  for a sufficient length of 
time when it has reache d to the required pressure, and leakage detections conduct ed for all weld joints 
and connections areas. Small size pressure vessels can also be immersed in water for detection.  
11.5.3.4 During the test process, if no leakage was detected, then the pressur e vessel shall be regarded 
as qualified; if any leakage was detected, then the pressure vessel should be retested after repairing.  
11.5.3.5 Other requirements of the airtightness test should be according to the relevant standards and 
provisions.  
11.5.4 Ot her leak testing methods and requirements should also comply with the relevant standards.  
12 Layered pressure vessel  
The fabrication of layered pressure vessels, apart from meeting the other relevant provisions of this 
standard, also should meet the follo wing requirements.  
12.1 Forming and inner cylinder  
12.1.1 The forming tolerances of the inner cylinders of wrapped pressure vessels (Including wrapped 
layered cylindrical segment, wrapped layered cylindrical entirety), flat -steel ribbon wound pressure 
vessels should be consistent with the specifications stated in Table 7.  
Table 7 Forming tolerances for the inner cylinders of wrapped pressure vessels and flat -steel ribbon 
wound pressure vessels  
Forming tolerances, mm  
The align deviation value b of 
Category  A weld joints  
(see Diagram 3)   Edge E formed at Category A 
weld joints  
(see Diagram 5)  Difference between the 
maximum diameter and 
minimum diameter of a same 
section  
(see Diagram 9)  
 1.0  1.5  0.4%D 1, and  5 
12.1.2 The forming tolerances of single -layered shrink fit cylinder pressure vessels  
12.1.2.1  After a single -layered cylinder is formed, it should be divided along its axis  into three 
sections as the upper section, middle se ction and lower section to measure the  internal diameter . The 
difference between the maximum diameter and minimum diameter of a same section should be less 
than 0.5% of the inner diameter of the cylinder.  
12.1.2.2 The linearity  of a single -layered cylinder  should be measured using a straight ruler which is 
not shorter than the length of the cylinder. Against the ruler on the cylinder tube wall along the axial 
direction, the clearance between the ruler and the cylinder wall shall not be greater than 1.5mm.  - 38 - 12.1.2.3 The surfaces of Category A weld joints are required to be machined or ground out, any weld 
reinforcement, unfitness, undercut are not allowed to be retained, and make sure the roundness at the 
joint area is consistent with the cylinder body. Use a n inner sample sheet or outer sample sheet with a 
chord length which is equal to 1/3 of the inner diameter of this single -layered cylinder, and not less 
than 300mm (see Diagram 5) ; the formed E edges should be consistent with the specifications 
indicated in  Table 8.  
 
Table 8 E edge tolerance for the single -layered cylinder of shrink fit pressure vessels  
E edge, 
mm  1.50  1.50 > E  
0.75 1.25 > E  
1.00 1.00 > E  
0.75 0.75 > E  
0.50 0.50 > E  
0.20 < 2.0  
The arc 
length of 
the E edge/ 
The 
circumfere
nce of the 
shrink fit 
surface, %  0 3 4 5 6 7 Excluding  
12.1.3 The assembly tolerances of the inner cylinders of wrapped layered cylindrical entirety pressure 
vessels and flat -steel ribbon wound pressure vessels  
12.1.3.1 The align deviation value b (see Diagram 3) of Category  B weld joints between the inner 
cylinders  should not exceed 1.5mm; the connection between the cylinder and the end flange or the 
head, its align deviation value should not exceed 1.0mm.  
12.1.3.2 The E edge formed on the axial by the Category  B weld joints of an inner cylinder (see 
Diagram 6), should be checked by using a ruler with a length not less than 300mm, the E value shall 
not be greater than 1.5mm.  
12.1.3.3 The linearity  tolerance of assemble inner cylinder shall not be more than 0.1%  of the cylinder 
length, and shall not be greater than 6mm.  
12.1.4 Welding and heat treatment of inner cylinder  
12.1.4.1 Inner cylinder or assemble inner cylinder shall not have any undercut.  
12.1.4.2 The outer surfaces of Category A, B weld joints of in ner cylinders or assemble inner 
cylinders shall be machined or gr ound , to ensure a smooth transition of the surfaces and the base 
metal surfaces.  
12.1.4.3 For t he Category A weld joints of carbon steel and low -alloy steel inner cylinders of wrapped 
pressur e vessels, the Category A and B weld joints of carbon steel and low -alloy steel inner cylinders 
of flat steel ribbon wound pressure vessels should be conducted with post -weld heat treatments.  
12.2 Assembly  
12.2.1 Sheet wrapping  - 39 - 12.2.1.1 All rust, grease a nd other debris which is on the outer surfaces of the inner cylinder, wrapped  
sheets or sheets to be used for wrapping should be removed before conducting the wrapping process.  
12.2.1.2 The longitudinal weld joints of the inner cylinder and the Category C  weld joints of each 
layer sheet should be staggered evenly; the circumferential weld joints of wrapped layered cylindrical 
entirety pressure vessels and the circumferen tial weld joints of each sheet layer should be staggered 
evenly, and the minimum distan ce between the circumferential weld joints of two adjacent sheet 
layers should be greater than the design requirements.  
12.2.1.3 Before wrapping the next layer of sheet, one should grind and smooth the welding seam of 
the previous sheet.  
12.2.1.4 After gr inding, one should conduct visual inspection to the weld joints on the sheets ; there 
must be no cracks, undercut, and intensive air  holes.  
12.2.1.5 After sheet wrapping, one should carry out loose area checking. With regard to a pressure  
vessel with the in ternal diameter of its inner cylinder D i  1000mm, for each loose area along the 
circumferential, the length shall not exceed 30% of the D i, along the axial the length shall not exceed 
600mm; with regard to a pressure vessel with the internal diameter of i ts inner cylinder D i> 1000mm, 
for each loose area along the circumferential, the length shall not exceed 300mm, along the axial the 
length shall not exceed 600mm.  
12.2.1.6 On the sheets of each multi -layered cylindrical segments , there  should be according  to the 
design , requirements to  process leakage detection holes.  
12.2.1.7 For the connections between each sheet of a wrapped layered cylindrical entirety pressure 
vessel and an end flange or head, the align deviation value  shall not be larger than 0.8mm.   
12.2.2 Shrink fitting  
12.2.2.1 Before operating the shrink fitting, a sandblasting treatment or a shot peening treatment 
should be conducted to each single -layered cylinder, to remove rust, grease and the integration 
effective debris between layers.  
12.2.2.2 The selection of the heating temperature for shrink fitting operation, should  give priority to 
not affecting the properties of the steel material. The shrink fitting operation should rely on the weight 
of the cylinder t o fit into each other, any forceful push down shall not be allowed.  
12.2.2.3 During shrink fitting, the Category A joints of each single -layered cylinder should mutually 
stagger ; the stagger angle shall not be smaller than 30°.  
12.2.2.4 Except for the inn er cylinder, each one of the shrink fitting cylinders should be drilled with 
relief holes according to the design requirements.  
12.2.2.5 After the grooves on both ends of the shrink fitting cylinder are processed, use a feeler gauge 
to check the gap of the  shrink fitting surfaces. Any one gap area with a radial gap size of 0.2mm must 
not be greater than 0.4% of the area of the shrink fitting surface; for any gap with a radial size  of more 
than 1.5mm, welding repair should be conducted.  
Note: Radial gap siz e refers to the maximum thickness of a feeler gauge which can be squeezed  into 
the gap; Gap area refers to the product of the gap depth along the cylinder axis and the arc length of 
the gap.  - 40 - 12.2.3 Flat steel ribbon winding  
12.2.3.1 After preparation of cy linders for flat steel ribbon wound pressure vessels is completed, the 
cylinders shall undergo a leak test according to the provisions in 11.5 ; after passing  the leak test the 
flat steel ribbon winding can be carried out. The leak test pressure shall not b e greater than the 
formula (1) calculated value:  
PTi=[]ii
Ri...........................................................................(1)  
In which: P Ti -------  The leak test pressure for the inner cylinder, Mpa;  
[]i --------------- The allowable stress of the inner cylinder material under test temperature, Mpa;  
i-------------------- The wall thickness of the inner cylinder, mm;  
Ri------------------- The inner radius of the inner cylinder, mm;  
12.2.3.2 Before windin g flat steel ribbon, all rust, grease and debris should be removed from the outer 
surfaces of the inner cylinder and steel ribbons.  
12.2.3.3 The winding process of each layer of the flat steel ribbons should be conducted  according to 
the design -specified w ound angle and pre -tensile stress, and recording the force measurement device 
readings. During the winding process of the flat steel ribbons, one should measure and record the 
actual thickness of the steel ribbon of each layer, and ensure the actual total thickness of every layer of 
the steel ribbons is greater than the design thickness of the steel ribbon layers, otherwise  one should 
increase the layers of steel ribbons.  
12.2.3.4 Among the same layer of steel ribbons, the spacing between any adjacent steel  ribbons 
should be evenly distributed and less than 3mm, and must not cut any sides of a steel ribbon for 
reason s of uneven spacing.  
12.2.3.5 After each layer of the steel ribbon is wound, a loose area inspection should be carried out . 
The loose area on ea ch steel ribbon shall not exceed 15% of the total area of this steel ribbon.  
12.2.3.6 The beginning and ending of each steel ribbon layer should be tightly packed with the 
previous layer, and the  ends of the steel ribbon should  be weld ed for a length whic h is double  the 
ribbon width, in order to strengthen and tighten the ribbon spacing. The welding seam of the steel 
ribbon ends of each layer should be ground smooth, and use a 5 times magnifying glasses to carry out 
inspection to the appearance of the weld ing seam, to check there are no defects such as undercuts, 
intensive air  holes, slag or cracks. When necessary, a magnetic particle testing or penetration testing 
can be conducted.  
12.2.3.7 Steel ribbons shall be allowed for an angle of 45° trimming for bu tt splicing, the splicing 
length of a steel ribbon must not be shorter than 500mm, each ribbon should be allowed for one 
splicing only,  and each layer of winding steel ribbon should not have more than three splicings. The 
splicing joints should use full pe netration structure, before splicing one should carry out welding 
procedure qualification assessment according to JB/T 4708 . After splicing, the welding seam should 
be ground to be level with the steel ribbons.  
12.3 Heat treatment  - 41 - 12.3.1 On the multi -layer ed pressure vessels, all kinds of the weld joints which are welded together 
with the wrapping cylindrical segments , may not have to undergo a post weld heat treatment after 
welding.  
12.3.2 Shrink fitted cylinders should be conducted a stress relief heat tr eatment, this process should be 
allowed  to be conducted with the post weld heat treatment as a combination treatment.  
12.4 Test sample and specimen  
12.4.1 The product welding specimen of wrapped layered cylindrical segment pressure vessels should 
include an inner cylinder welding specimen and sheet layer welding specimen. The welding specimen 
of the sheet layer  should  be welded at the extended part of the longitudinal joints (Category C) of a 
layer. At the seam root of the sample, a pad sheet which is the s ame material as the sheet layer and has 
the same thickness as the sheet layer should be prov ided.  
12.4.2 The inner cylinders of wrapped layered cylindrical entirety pressure vessels, flat steel ribbon 
wound pressure vessels (except inner cylinders made of  steel pipes) should be prepared with product 
welding specimen.  
12.5 Non -destructive testing  
12.5.1 The splice joints of the sheet layer of the  Category A weld joints of the inner cylinders of 
wrapped layered cylindrical segment pressure vessels, the Cate gory A weld joints of the single -
layered  cylinders of shrink fit pressure vessels, the Category A and Category B weld joints of the 
inner cylinders of wrapped layered cylindrical entirety pressure vessels, the welded joints connecting 
each layer of sheets and the end flanges or spherical  heads, the longitudinal and circumferential 
welded joints of the sheet at the most outside layer, the Category A and Category B weld joints of the 
inner cylinders of flat steel ribbon wound pressure vessels, all of the abov e mentioned weld joints 
should be conducted with a full (100%) radiographic testing or ultrasonic testing, and shall conform to 
the provisions in 10.6.  
12.5.2 The Category C weld joints of the sheet layers of multi -layered pressure vessels with a 
standard  tensile strength lower limit Rm   540MPa,  the surfaces of the weld joints should be 
conducted with 100% of magnetic particle testing or penetrant testing, and shall conform to the 
provisions in 10.6.  
12.6 Pressure test and leak test  
12.6.1 The pressure test and final leak test of multi -layered pressure vessels should be consistent with 
the requirements in Chapter 11 and the design documents.  
12.6.2 The pressure test for flat steel ribbon wound pressure vessels should meet the requirements in 
11.4,  but also in the pressure test, at a loc ation of 800mm from the welding seams of both ends of the 
most outside layer steel ribbon, and the central of the cylinder to measure the cylinder circumference.  
Take two sets of measurements during the test process, the first set is the measurements of 3 locations 
taken under a zero pressure state before the pressure test; the second set is the measurements of 3 
locations after the required test pressure is obtained and maintained for at least 5 minutes during the 
pressure test; calculate the average  (em) of the actual measured circumference elongation at the 3 
locations, and compare to the theoretical circumference elongation e th of the single -layered same size 
cylinder use  calculated by using the following formula . When the ratio between e m and e th is wit hin 
the range of 0.6 –1.0, then it should be regarded as passed . - 42 - Calculation of the circumferential theoretical elongation e th of a same size single -layered cylinder:  
eth=10.68R0PtRi2
Em(R02Ri2)..........................................(2)  
In wh ich:  
eth -------  the circumferential theoretical elongation of a same size single -layered cylinder, mm;  
R0---------- The external radius of the pressure vessel cylinder, mm;  
PT---------- The pressure of the pressure test of the flat steel ribbon wound press ure vessel, MPa;  
Ri---------- The internal radius of the pressure vessel cylinder, mm;  
Em--------- The elastic modulus of the materials under the temperature  of the pressure test, Mpa;  
12.6.3 After a flat steel ribbon pressure vessel qualified the pressure test and leak test, a weld 
protection shell should be provided by according to the design requirements.  
13 Requirements for pressure vessels leaving factory  
13.1 Documents for leaving factory  
13.1.1 The manufacturing unit should provide documents for the p roduct leaving factory to the 
purchasers of the pressure vessels; where there is any special requirements regarding to the use of the 
pressure vessels, a user's manual should also be provided.  
13.1.2 The documents for leaving factory should at least inclu de the following information:  
a) The pressure vessel completion plan;  
b) The product quality certificate of the pressure vessel (including product data table);  
c) Product quality testimony documents (including the quality certificate of the materials for m ain 
pressure components, materials list, the quality testimony documents of the heads and forged parts, 
quality plan and inspection plan, structure and size inspection report, welding record, non -destructive 
testing report, heat treatment report and automa tically recording curves, pressure test report and leak 
test report, fabrication documents relative to risk prevention and control, the on -site group welding of 
the group weld pressure vessels, and the technical information on quality inspection etc.);   
d) The rubbing copy and photocopy of the nameplate;  
e) Manufacturing supervision and inspection certificate for special equipment  (for pressure vessels 
which require supervision and inspection);  
f) Pressure vessel design documents (including the strength cal culation report or the stress analysis 
report, the risk assessment report formulated by according to the relevant requirements, as well as 
other necessary design documents.)  
13.2 Nameplate  - 43 - 13.2.1 The n ameplate of a pressure vessel should be fixed at a cle arly visible location, but the 
nameplate of a low -temperature pressure vessel cannot be directly housed onto the shell . 
13.2.2 A nameplate should include at least the following information:  
a) Name of the product;  
b) Name of the manufacturing unit;  
c) License No,/Grade of the manufacturing unit;  
d) Product standard;  
e) Main body materials;  
f) Medium name;  
g) Design temperature;  
h) Design  pressure or maximum allowable working stress (when it is necessary);  
i) Pressure of the pressure test;  
j) Product serial number;  
k) Equipment code;  
l) Manufacturing date;  
m) Pressure vessel type;  
n) Volume (heat exchange area);  
13.3 Coating and packing for pressure vessels transport  
The requirements on coating and packing for pressure vessels transport should not only meet the 
provisions in JB/T4711, but also should be consistent with the requirements in the design documents.