|
US$559.00 · In stock
Delivery: <= 5 days. True-PDF full-copy in English will be manually translated and delivered via email.
GB/T 21432-2021: Graphite pressure vessels
Status: Valid GB/T 21432: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 21432-2021 | English | 559 |
Add to Cart
|
5 days [Need to translate]
|
Graphite pressure vessels
| Valid |
GB/T 21432-2021
|
| GB/T 21432-2008 | English | 599 |
Add to Cart
|
3 days [Need to translate]
|
Graphite pressure vessels
| Obsolete |
GB/T 21432-2008
|
PDF similar to GB/T 21432-2021
Basic data | Standard ID | GB/T 21432-2021 (GB/T21432-2021) | | Description (Translated English) | Graphite pressure vessels | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | J74 | | Word Count Estimation | 30,360 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 21432-2021: Graphite pressure vessels---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Graphite pressure vessels
ICS 23.020.30
J74
National Standards of People's Republic of China
Replace GB/T 21432-2008
Graphite pressure vessel
Released on 2021-03-09
2021-07-01 implementation
State Administration of Market Supervision and Administration
Issued by the National Standardization Management Committee
Table of contents
Foreword Ⅲ
1 Scope 1
2 Normative references 1
3 Terms and definitions 2
4 General requirements 3
5 Material 3
6 Design 4
7 Manufacturing 6
8 Inspection and acceptance 9
9 Container delivery requirements 11
Appendix A (Normative Appendix) Evaluation of Dipping Process 13
Appendix B (Normative Appendix) Bonding Process Evaluation 17
Appendix C (Normative Appendix) Test Method for Permeability Coefficient of Impermeable Graphite Materials 21
Graphite pressure vessel
1 Scope
This standard specifies the general requirements, materials, design, manufacturing, inspection and acceptance of graphite pressure vessels, and requirements for the vessels to leave the factory.
This standard applies to graphite pressure vessels with the following conditions.
---The working pressure is greater than or equal to 0.1MPa, and the design pressure is not greater than 2.4MPa;
---Design temperature -70℃~205℃;
--- The containing medium is gas, liquefied gas or liquid whose maximum working temperature is higher than or equal to its standard boiling point.
This standard does not apply to the following graphite containers.
---Graphite container heated by direct flame;
---Graphite container in nuclear power plant;
---Cast graphite container;
---Graphite brick lining equipment whose main stress is borne by the metal shell.
2 Normative references
The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this article
Pieces. For undated reference documents, the latest version (including all amendments) is applicable to this document.
GB/T 150.1 Pressure Vessel Part 1.General Requirements
GB/T 150.2 Pressure Vessel Part 2.Materials
GB/T 150.3 Pressure Vessel Part 3.Design
GB/T 150.4 Pressure Vessel Part 4.Manufacturing, Inspection and Acceptance
GB/T 151 heat exchanger
GB/T 1431 Method for determination of compressive strength of carbon materials
GB/T 1804 General Tolerance Tolerance of linear and angular dimensions without tolerance
GB/T 8721 Method for determination of tensile strength of carbon materials
GB/T 13465.1 Test methods for impermeable graphite materials Part 1.General rules for mechanical properties test methods
GB/T 13465.2 Test method for impermeable graphite materials Part 2.Flexural strength
GB/T 13465.3 Test method for impermeable graphite materials Part 3.Compressive strength
GB/T 13465.5 Test method for shrinkage of impermeable graphite phenolic adhesive
GB/T 13465.6 Water pressure blasting test method for impermeable graphite tube
GB/T 13465.8 Test method for bonding shear strength of impermeable graphite adhesive
GB/T 13465.9 Test method for bonding tensile strength of impermeable graphite adhesive
GB/T 13927-2008 Industrial valve pressure test
GB/T 21921 Test method for tensile strength of impermeable graphite materials
GB/T 24203 Determination of true density and true porosity of carbon materials Boiling method
GB/T 24528 Method for determination of bulk density of carbon materials
GB/T 26961 Water pressure test method for impermeable graphite equipment
GB/T 35922 Technical Specification for Corrosion Resistance of Impregnated Graphite
GB/T 35926 Technical specification for impermeable graphite bonding operation
HG/T 2059 Impermeable Graphite Tube Technical Conditions
HG/T 2370-2017 Technical requirements for impermeable graphite chemical equipment
HG/T 20584 steel chemical container manufacturing technical requirements
JB/T 4711 Pressure vessel coating and transportation packaging
NB/T 47003.1 Steel Welded Atmospheric Pressure Vessel
YB/T 2818 graphite block
TSG07-2019 Licensing Rules for Special Equipment Production and Filling Units
TSG21-2016 Safety Technical Supervision Regulations for Stationary Pressure Vessels
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Design temperature
Under normal working conditions of the container, set the temperature of the component (the average temperature along the cross section of the graphite component).
Note. Design temperature and design pressure are used as design load conditions.
3.2
Graphite
A collective term for graphitized materials and semi-graphitized materials.
3.3
Graphitized material
It is formed by mixing, extruding, moulding (or vibration forming) of coke or graphite powder and particles and pitch at a high temperature of 2400℃~3000℃
Made of graphite material.
3.4
Half-graphitized material
Graphite material formed by mixing graphite powder, granules and pitch, extruding (or molding, vibrating forming), and calcining at 1000°C to 1200°C.
3.5
Imperviousgraphite
Graphite materials that are impermeable to liquids and gases on the current industrial level (that is, under low pressure and temperature conditions).
Note. Including impregnated graphite, profiled (including extruded and molded) graphite and cast graphite.
3.6
Profilingimperviousgraphite
The impermeability formed by mixing graphite powder and binder under certain pressure (molding or extrusion, including isostatic pressing) and curing
graphite.
3.7
Impregnated graphite
Use the impregnation process to press the organic or inorganic liquid material (impregnant) into the pores of the permeable graphite material and make it solidify in the pores
And the formation of impermeable graphite.
Note. Different varieties are formed due to different impregnants used to increase the permeability of materials. The most widely used is phenolic impregnated stone impregnated with phenolic resin
Ink, followed by furan impregnated graphite, epoxy impregnated graphite, PTFE impregnated graphite, water glass impregnated graphite and so on.
3.8
Impregnation
A method of filling the open pores in graphite parts with corrosion-resistant, temperature-resistant resins and inorganic substances.
3.9
Impregnation agent
It is a material used to immerse into the pores of carbon or graphite materials and make the carbon or graphite materials impermeable through a curing process.
3.10
Binder graphitecement
The mixture of graphite powder and resin, if necessary, add curing agent, modifier, etc., for the bonding of graphite materials.
3.11
Permeability coefficient
k(L)
Comprehensively reflect the permeability of materials and measure the gas permeability of solid materials.
4 General requirements
4.1 The materials, design, manufacturing, inspection and acceptance of graphite pressure vessels and the delivery of equipment shall not only comply with the provisions of this standard, but also comply with
Relevant laws, regulations and safety technical specifications promulgated by countries such as TSG21-2016 and TSG07-2019.
4.2 The metal pressure components in graphite pressure vessels shall comply with the relevant regulations of GB/T 150.1~GB/T 150.4 and GB/T 151.
Certain; non-compressed steel parts and components shall comply with the relevant regulations of NB/T 47003.1.
4.3 The manufacturer of graphite pressure vessels shall establish a sound quality assurance system and operate effectively in accordance with the relevant regulations of TSG07-2019.
4.4 The manufacture of graphite pressure vessels within the jurisdiction of TSG21-2016 shall be supervised by special equipment safety supervision agencies.
4.5 The use of new materials, new technologies, new processes, and pressure vessels with special requirements for use are inconsistent with the requirements of this standard, or this standard
If the requirements are not made and may have a significant impact on the safety performance, the relevant units shall implement the regulations in 1.9 of TSG21-2016.
5 materials
5.1 The main materials for the manufacture of graphite pressure vessels include. graphite materials, binders, impregnants, metal materials and sealing materials. Among them, stone
The ink materials are mainly impregnated graphite and pressed graphite impermeable graphite materials.
5.2 Graphite materials used for pressure components of graphite pressure vessels shall comply with this standard and the provisions of HG/T 2370-2017; graphite pressure vessels shall comply with the provisions of this standard and HG/T 2370-2017;
The metal materials used for the appliance should meet the requirements of GB/T 150.1 and GB/T 150.2.
5.3 The material production unit shall provide the user with a quality certificate (original) in accordance with the provisions of the standard. The quality certificate shall at least include the standard number,
Specifications, furnace (batch) number, particle size, specific resistance, various mechanical performance data, production unit name and inspection seal, etc., and make clear on the material
Clear and firm logo.
5.4 When the manufacturing unit obtains materials for pressure components from non-material production units, it shall also obtain the original material quality certificate or stamp the material supply list.
For the valid copies of the official seal and the operator’s seal, the material unit is responsible for the authenticity and consistency of the material certificate.
5.5 The graphite material used for the manufacture of pressure vessels shall be subjected to the evaluation of the impregnation process and the molding process of the composite material, and shall meet the following requirements.
Claim.
a) The process assessment report and process assessment procedures should be approved by the technical person in charge of the manufacturing unit and confirmed by the supervisory inspector;
b) The source, grade and quality index of the raw materials used to manufacture graphite materials should be recorded in the process assessment report;
c) The impregnation process assessment shall be carried out in accordance with Appendix A, and the impregnation process assessment report shall be filled in truthfully in accordance with Appendix A and GB/T 35922;
d) For qualified processes (including impregnation process and composite material molding process) and materials, verification should be carried out regularly (every 6
At least once a month).
5.6 The graphitized or semi-graphitized matrix material used for impregnating graphite shall comply with the regulations of YB/T 2818.
5.7 The physical and mechanical properties of impermeable graphite materials should meet the requirements of Table 1.
It should meet the requirements of HG/T 2059.
7.1.3 If the manufacturing unit changes carbon or graphite materials (such as material manufacturing unit, grade or batch number, density range, particle size range), synthesis
Resin (such as material manufacturing unit, resin grade, density range, viscosity range at room temperature, important components and range), process parameters (such as process pressure
(Force range, process time range, process temperature range, vacuum range), you need to re-evaluate the process.
7.1.4 The bonding work of graphite containers and components should be carried out by bonding workers who have passed the training and assessment of the manufacturing unit; when the bonding workers are within 6 months
If there is no bonding operation or doubt about its bonding operation ability, the training and assessment shall be carried out again. The impregnation of graphite parts should be carried out by
The manufacturing unit trains and evaluates qualified personnel to operate.
7.1.5 When materials are re-inspected, samples are taken in batches, and the results of the re-inspection should meet the relevant regulations in Table 1.
7.2 Design changes and material substitution
For design changes and material substitution of pressure components, the manufacturing unit shall obtain written approval from the original design unit in advance, and the approval document shall be
File and make detailed records on as-built drawings.
7.3 Incoming inspection, segmentation and marking of materials
7.3.1 The manufacturer shall review the authenticity of the material quality certificate and material mark and the difference between the material quality certificate and the material mark when the material enters the factory for inspection.
consistency.
7.3.2 The materials used to manufacture the pressure components shall have traceable marks, and the transplantation of the marks shall be completed before the material is divided.
7.4 Material reinspection
Material re-inspection should be carried out in the following cases.
a) The main pressure component materials for which the authenticity of the quality certificate cannot be determined or the performance and chemical composition are questionable;
b) The design drawings require re-inspection;
c) The user requires re-inspection.
7.5 Bonding of graphite parts
7.5.1 Bonding environment
7.5.1.1 During the bonding operation of graphite containers and components, the temperature of the workplace should be controlled so as not to affect the bonding strength quality of each bonding resin
Within the scope, the average temperature of the bonded material should be kept at 10℃~52℃, and the relative humidity of the work place should not exceed 90%.
7.5.1.2 When benzenesulfonyl chloride is used as the curing agent, if any of the following situations occurs without reliable guarantee measures, it shall not be bonded;
a) The temperature of the working place is lower than 15℃ or higher than 35℃;
b) The relative humidity of the workplace is greater than 90%.
7.5.2 Evaluation of bonding process
7.5.2.1 Before the bonding operation, the manufacturing unit shall conduct the bonding process evaluation, and carry out the vessel manufacturing according to the qualified bonding process regulations.
The qualified bonding process should be verified regularly (at least once every 6 months).
7.5.2.2 The bonding process evaluation shall be implemented in accordance with Appendix B. The bonding process evaluation report should be filled in truthfully in accordance with Appendix B and GB/T 35926, and report
The report shall be approved by the technical person in charge of the manufacturing unit and confirmed by the supervisory inspector.
7.5.3 Bonded joint requirements
7.5.3.1 Pressure components that can be manufactured as a whole should not be spliced. Under special circumstances (such as the component size is too large, the market does not have the corresponding specification monolithic material), it should be
When the pressure components are made by splicing, the strength of the bonding seam shall not be lower than the requirements of the design documents.
7.5.3.2 When the graphite cylinder is spliced, the stepped or tenon-groove type shall be used; when the head, tube sheet, and heat exchange block need to be spliced in multiple layers, the single layer can be aligned.
Butt joints between two adjacent layers should be staggered.
7.5.3.3 After the graphite parts are bonded, the bonding seam should be tight and full, and the seam width should be less than or equal to 1mm.
7.5.3.4 The graphite parts shall be cured after bonding, and the curing control shall be implemented in accordance with the provisions of the bonding process evaluation document.
7.5.4 Repair
7.5.4.1 The materials and bonding seams of graphite containers shall be repaired by an approved bonding process.
7.5.4.2 The material repair of graphite vessels shall meet the following requirements.
a) Surface scratches and pits with a depth of not more than 5% of the total thickness are allowed to be repaired, but the area of the repaired part shall not exceed the total thickness of the pressure part.
3% of the area, unless otherwise specified by the user;
b) The repair method and scope shall be proposed in writing by the relevant responsible engineer, and can be implemented only after the approval of the technical person in charge of the manufacturing unit;
c) The number of repairs of the same defect in the same part shall not exceed 2 times;
d) The appearance quality of the repaired part should meet the requirements of 7.7.1, and the material performance of the repaired part should not be lower than the material performance of the repaired part;
e) All repairs should be completed before the hydraulic test and should be carried out by the manufacturer. If repair is required after the hydraulic test, the repair is over
After that, the water pressure test shall be repeated in accordance with the provisions of 8.4.3;
f) The material repair should have a detailed record, which should include at least the bonding type, the size of the bonding part, the material brand, the manufacturer,
Bonding process parameters (joint gap, curing temperature and time, etc.), bonding operators and repair time, etc. Material repair records should
Save it as a quality certificate.
7.5.4.3 The bonding seam repair of graphite vessels shall meet the following requirements.
a) The repair of the same part of the bonding seam should not exceed 2 times. If more than 2 times, the situation should be summarized and the manufacturing unit's technology should be reviewed before the repair.
Approval by the person in charge;
b) The number of repairs, positions, and repairs should be recorded in the quality certification document and saved.
7.6 Impregnation of graphite parts
7.6.1 The impregnation of graphite parts includes impregnation and thermal curing (or plasticization), and the operation should be carried out in accordance with the process confirmed by the impregnation process evaluation.
7.6.2 The impregnation process evaluation shall be carried out in accordance with the requirements of Appendix A and GB/T 35922.
7.7 Machining of graphite parts
7.7.1 The material of the processed graphite parts should be uniform without cracks and other defects that may affect the mechanical properties of the material; the sealing surface must not affect the sealing
Defects in performance.
7.7.2 The graphite hole shall be inspected with a ϕ (d-1)mm test rod, and the pass rate shall be greater than 90%; when the hole needs to be plugged (including block hole type and column type), the pass rate shall be greater than 90%.
Tube type), the hole blocking rate on each side should not be greater than 1%.
7.7.3 The limit deviations of the linear dimensions of the machined surface and the non-machined surface of graphite parts are respectively according to m in GB/T 1804
Level and c level regulations.
7.8 Test pieces and specimens
7.8.1 In one of the following situations, product test pieces shall be made one by one.
a) For mobile containers, product immersion test pieces and product bonding test pieces should be made;
b) For containers with extremely or highly hazardous media, product immersion test pieces and product bonding test pieces should be made;
c) The use of new impregnating agents and/or changing the impregnation process and/or changing the resin thermal curing temperature, and there is no continuous inspection system of more than 30 sets
For containers with grid data, product immersion test pieces and product bonding joint test pieces should be made;
d) For containers with tensile stress in the bonding joints, test pieces of product bonding joints should be made;
e) Design documents or containers required by users.
7.8.2 For containers other than those specified above, if the manufacturer can provide 30 consecutive containers, use the same grade of graphite material, the same impregnant, and impregnation.
Process, bonding process, curing conditions, standardize the qualified data of the product impregnation test piece and product bonding test piece, and prove the impregnation material and bonding joint
8.2.6 The determination methods of the tensile strength, shear strength, shrinkage rate, etc. of the graphite binder shall be in accordance with GB/T 13465.9,
GB/T 13465.8, GB/T 13465.5 and other standards.
8.2.7 Impermeable graphite tubes shall be inspected in batches in accordance with HG/T 2059, and corresponding batches of graphite tube quality certificates and certificates shall be provided.
Grid certificate.
8.3 Inspection of parts
8.3.1 General requirements
The inspection of parts and components shall be carried out one by one according to the requirements of the design documents, and their appearance, geometric dimensions and mechanical properties shall meet the requirements of the design documents.
8.3.2 Water pressure test or air pressure test of graphite tube
After the graphite tube is extruded, it should have an aging treatment of more than 2 months, and the water pressure test or air pressure test should be carried out one by one before assembly.
In the test, the test pressure shall not be lower than 2 times the design pressure, and shall not be lower than 1MPa, the water pressure holding time shall not be less than 30min, and the air pressure holding time shall be no less than 30min.
The pressing time is not less than 10min, and no leakage is qualified.
8.3.3 Water pressure test or air pressure test for graphite blocks
The graphite block of the block-hole heat exchanger shall be subjected to a single-piece hydraulic test or air pressure test before assembly, and the test pressure shall not be lower than the design
1.5 times the pressure, and not less than 1MPa, the water pressure holding time is not less than 30min, the air pressure holding time is not less than 10min, no leakage
Is qualified.
8.4 Container inspection
8.4.1 Visual inspection
The appearance of the graphite parts and the surface of the finished container should meet the requirements of the design documents, and the internal and external surfaces should be smooth, free of bubbles, blisters,
Dimples and cracks must not have sudden sharp scratches and other defects.
8.4.2 Inspection requirements
After the container is assembled, the hydraulic pressure test should be carried out one by one according to the design documents and the requirements of this standard, and the leakage test should be added when necessary.
8.4.3 Hydrostatic pressure test of the vessel
The hydraulic pressure test of the container shall be in accordance with the provisions of GB/T 26961 and shall meet the following requirements.
a) Clean water should be used in the hydraulic test, and the pressure chamber to be tested should be filled with water during the test;
b) The water pressure test should use two pressure gauges with the same range and have been metrologically verified or calibrated. The accuracy of the pressure gauge is not less than 2.5.
The range of the force meter should not be lower than 1.5 times and not higher than 3 times the test pressure;
c) The test pressure of general pressure vessels shall not be lower than 1.5 times the design pressure, and the degree of toxicity hazard of the container shall be extreme or high hazard
For the pressure vessel of the medium, the test pressure shall not be lower than 1.75 times the design pressure;
d) During the pressure test of the vessel, the pressure is increased by 0.1 MPa and the pressure is maintained for 2 min to 3 min. After the test pressure is reached, the pressure is maintained for 30 min, and then
Slowly reduce to the design pressure, and the pressure holding time is sufficient (not less than 60min) for inspection, and no leakage is qualified;
e) After the test is completed, the water should be drained.
8.4.4 Container leak test
8.4.4.1 Test requirements
Graphite pressure vessels whose medium toxicity is extremely, highly hazardous, or whose design is not allowed to have a small amount of leakage, should be leak tested.
Inspection, including all joints and connections, etc.
8.4.4.2 Leak test method
Leak test includes air tightness test, ammonia leak test, halogen leak test and helium leak test, etc. Degassing tightness test according to 8.4.
In addition to the requirements of 4.4, the other three types of container leakage test methods, pressures, technical requirements, etc. are designed by the designer in accordance with the requirements of HG/T 20584.
Provided in the document.
8.4.4.3 Timing of leak test
The leak test shall be carried out after the water pressure test is qualified.
8.4.4.4 Air tightness test
8.4.4.4.1 For pressure vessels with safety valves, bursting discs and other overpressure relief devices, if air tightness tests are required, the designer should give
The maximum allowable working pressure of the pressure vessel.
8.4.4.4.2 The airtightness test pressure shall not be lower than the maximum allowable working pressure, and the test medium shall be clean air, nitrogen or other inert gas
body. During the test, the pressure should be increased slowly, and after the specified test pressure is reached, the pressure should be maintained for a long enough time (not less than 30min) for inspection.
Grid; You can also immerse the container in water for inspection, and no leakage is considered qualified.
9 Container factory requirements
9.1 The quality certification documents of the container
9.1.1 The quality certification documents for the vessel delivery should at least include the "pressure vessel product certificate", "product quality certificate", "quality plan", "special
Equipment Supervision and Inspection Certificate" (pressure vessel within the jurisdiction of TSG21-2016), "As-built Drawing", "Product Manual" and "Product
Nameplate rubbings".
9.1.2 The as-built drawing should have a special seal for the design of the design unit (the copy stamp is invalid), which is consistent with the actual product, and the as-built seal (as-built drawing)
The chapter should have the name of the manufacturer, the number of the manufacturing license, the signature of the reviewer and the words "as-built drawing").
9.1.3 The quality certificate shall include the following contents.
a) Product qualification certificate;
b) Product technical characteristics;
c) Material properties of main graphite pressure components;
d) The mechanical properties of the adhesive (such as when the material is spliced and the bonding seam is under tensile stress or shear stress);
e) Test results of pressure test;
f) The items that need to be added when there are steel pressure components are in accordance with the provisions of GB/T 150.1~GB/T 150.4 and GB/T 151;
g) Items that do not conform to this standard and drawings;
h) Appearance and geometric size inspection report;
i) Heat curing (plasticizing) report and automatic recording curve;
j) Rubbing or copy of the product nameplate, etc.
9.1.4 The special equipment supervision and inspection certificate shall be provided by the supervision and inspection agency recognized by the state.
9.1.5 The product manual (or manual) should include the following.
a) Equipment performance and purpose;
b) Product structure diagram;
c) Precautions for equipment acceptance and installation;
d) Precautions for the use of equipment;
e) Precautions for equipment maintenance.
9.1.6 The nameplate shall be fixed in an obvious position, and shall include at least the following contents.
a) Product name;
b) The name of the manufacturer;
c) Manufacturing unit license number and license level;
d) Product standards;
e) Main material;
f) The name of the medium;
g) design temperature;
h) Design pressure, maximum allowable working pressure (if necessary);
i) Pressure test pressure;
j) Product number or product batch number;
k) Device code;
l) Date of manufacture;
m) Classification of pressure vessels;
n) Weight and volume (heat exchange area).
9.2 Painting, packaging and transportation
The paint, packaging and transportation of the container shall comply with the regulations of JB/T 4711.
Tips & Frequently Asked Questions:Question 1: How long will the true-PDF of GB/T 21432-2021_English be delivered?Answer: Upon your order, we will start to translate GB/T 21432-2021_English as soon as possible, and keep you informed of the progress. The lead time is typically 3 ~ 5 working days. The lengthier the document the longer the lead time. Question 2: Can I share the purchased PDF of GB/T 21432-2021_English with my colleagues?Answer: Yes. The purchased PDF of GB/T 21432-2021_English will be deemed to be sold to your employer/organization who actually pays for it, including your colleagues and your employer's intranet. Question 3: Does the price include tax/VAT?Answer: Yes. Our tax invoice, downloaded/delivered in 9 seconds, includes all tax/VAT and complies with 100+ countries' tax regulations (tax exempted in 100+ countries) -- See Avoidance of Double Taxation Agreements (DTAs): List of DTAs signed between Singapore and 100+ countriesQuestion 4: Do you accept my currency other than USD?Answer: Yes. If you need your currency to be printed on the invoice, please write an email to [email protected]. In 2 working-hours, we will create a special link for you to pay in any currencies. Otherwise, follow the normal steps: Add to Cart -- Checkout -- Select your currency to pay. Question 5: Should I purchase the latest version GB/T 21432-2021?Answer: Yes. Unless special scenarios such as technical constraints or academic study, you should always prioritize to purchase the latest version GB/T 21432-2021 even if the enforcement date is in future. Complying with the latest version means that, by default, it also complies with all the earlier versions, technically.
|