Knowledge of pressure vessels

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Chapter 2: Materials Article 10: The quality and specifications of the materials used for pressure vessels shall comply with the relevant **standards and industry standards. The production of pressure vessel materials is approved by **regulatory authorities. The material manufacturer shall provide the user with a quality certificate (the original) in accordance with the relevant standards, and shall affix a clear and durable stamp or other mark in a conspicuous position on the material. This mark shall include at least the code of the material manufacturing standard, the material grade and specifications, the furnace (batch) number, a mark recognized by the supervisory authority, the name of the material manufacturer, and a inspection seal or other mark. The content of the material quality certificate must be complete and clear, and it must bear the quality inspection seal of the material manufacturer. 　　When a pressure vessel manufacturing unit obtains materials for pressure vessels from a non-material production unit, it shall obtain either the original quality certificate for the materials or a valid copy stamped with the inspection seal of the material supplier and the signature of the responsible person. The pressure vessel manufacturing unit is responsible for the authenticity and consistency of the pressure vessel materials obtained as well as the material quality certificates. 　　Article 11: When selecting materials for pressure vessels, in addition to mechanical properties and bending strength, compatibility with the medium must also be taken into consideration. The phosphorus content (as determined by melting analysis; the same applies hereafter) of steel specifically designed for pressure vessels should not exceed 0.030%, while the sulfur content should not exceed 0.020%. If carbon steel boiling steel plates or carbon steel killed steel plates are used to manufacture pressure vessels (with the exception of glass-lined pressure vessels), they must comply with the requirements specified in GB150 \"Steel Pressure Vessels\". Carbon steel boiling steel plates and Q235A steel plates shall not be used to manufacture pressure vessels that are directly exposed to flame heating. 　　Article 12: For carbon steel and low-alloy steel used in the main pressure-bearing elements of welded structural pressure vessels, the carbon content shall not exceed 0.25%. Under special circumstances, if steel with a carbon content higher than 0.25% is used, the carbon equivalent shall be limited to no more than 0.45%. The manufacturer must obtain the consent of the user and get approval from the person in charge of pressure vessel technology at the manufacturer’s facility; in addition, a material fracture resistance test report and a welding procedure qualification report must be provided, and the approval procedures specified in Article 7 of these regulations must be followed. 　　Article 13: The mechanical properties, bending properties, and impact test requirements for the materials used in steel pressure vessels (such as steel plates, forgings, steel pipes, studs, etc.) shall comply with the relevant provisions of GB150. 　　Article 14: Carbon steel and low-alloy steel sheets used for manufacturing pressure vessel shells shall be subjected to ultrasonic testing on a sheet-by-sheet basis if they meet one of the following conditions: 1. Pressure vessels that contain media with an extremely high or high degree of toxicity. 　　2. Pressure vessels that contain liquefied petroleum gas as the medium at midnight, with a sulfur and hydrogen content greater than 100 mg/l. 　　3. Pressure vessels with a maximum operating pressure of 10 Mpa or higher. 　　4. Steel plates that are required to undergo ultrasonic testing one by one as specified in Chapter 2 and Appendix C of GB150, GB151 \"Shell and Tube Heat Exchangers\", GB12337 \"Steel Spherical Storage Tanks\", and other **national and industry standards. 　　5. Mobile pressure vessels. 　　The ultrasonic testing of steel plates shall be carried out in accordance with the provisions of JB4730 \"Non-destructive Testing of Pressure Vessels\". The qualified grade of the steel plates used for the containers specified in paragraphs 1, 2, and 5 of this article shall be no lower than Grade II ； The qualified grade of the steel plates used for the containers specified in paragraph 3 of this article shall be no lower than Grade III; the qualified grade of the steel plates used for the containers specified in paragraph 4 of this article shall comply with the provisions of GB150, GB151, or GB12337. For mobile pressure vessels, 2** plates shall be sampled from each batch to undergo Charpy (V-notch) low-temperature impact tests at a temperature of minus 20°C or as specified in the drawings, with the sampling direction of the test specimens being horizontal. The low-temperature impact work index shall comply with the provisions of Appendix C of GB150. 　　Article 15: The requirements for cast iron used in pressure vessels are as follows: 1. It must be selected within the corresponding **standard range, and the material grade used for casting shall be indicated on the product quality certificate. 　　2. The design pressure and design temperature shall comply with the following provisions: (1) The design pressure of pressure vessels made of gray cast iron shall not exceed 0.8 Mpa, and the design temperature shall be 0–250°C℃ ； 　　(2) The design pressure of pressure vessels made of malleable cast iron and ductile iron shall not exceed 1.6 Mpa, with a design temperature ranging from -10 to 350°C. 3. Such materials shall not be used for the pressure-bearing components of pressure vessels that contain media with an extremely high, high, or moderate level of toxicity, nor for pressure-bearing components of flammable media with a design pressure of 0.5 Mpa or more; they shall also not be used for the pressure-bearing components of shell-and-tube waste heat boilers or mobile pressure vessels. 　　Article 16: The cast steel materials used for the pressure-bearing components of pressure vessels shall be selected in accordance with the relevant **standards or industry standards, and the grade of the material used in casting shall be specified in the product quality certificate. Cast steel materials should not be used for the pressure vessel shell and end closures (except where the pressure vessel manufacturer has prior experience in using such materials and it has been approved by provincial or **supervisory authorities). 　　Article 17: The requirements for non-ferrous metals used in pressure vessels (referring to aluminum, titanium, copper, nickel, and their alloys) are as follows: 1. Non-ferrous metals used for manufacturing pressure vessels shall be selected within the scope of the corresponding **standards or industry standards; when special requirements apply to these non-ferrous metals, they shall be specified in the design drawings or relevant technical specifications. 　　2. The manufacturing unit must establish a strict storage system and designate a specific area for storage. 　　3. The impact test requirements for materials used in pressure vessels made of non-ferrous metals shall comply with the provisions of the relevant standards. 　　4. The grooves of the welded joints in pressure vessels made of non-ferrous metals shall be prepared by mechanical methods, and their surfaces must be free from defects such as cracks, delamination, and inclusions. 　　Article 18: Aluminum and aluminum alloys used for the pressure-bearing components of pressure vessels shall meet the following requirements: 1. The design pressure shall not exceed 8 Mpa, and the design temperature range shall be from -269°C to 200°C. 2. When the design temperature is greater than 65°C, aluminum alloys with a magnesium content of 3% or more are generally not to be used. 　　Article 19: When steel and copper alloys are used as pressure-bearing components in pressure vessels, they should generally be in an annealed state. 　　Article 20: Pressure components for pressure vessels manufactured from titanium materials (referring to industrial pure titanium, titanium alloys, and their composite materials, the same below) shall meet the following requirements: 1. Design temperature: Industrial pure titanium shall not exceed 230°C, titanium alloys shall not exceed 300°C, and titanium composite plates shall not exceed 350°C. 　　2. Titanium materials used for manufacturing pressure vessel shells should be used in the annealed state. 　　3. The forming of titanium pressure vessel heads should be accomplished by hot forming or by cold forming followed by thermal reshaping. Ultrasonic testing should be performed on the formed titanium-steel composite plate heads. 　　4. Titanium pressure vessels generally do not require heat treatment; however, titanium vessels used in stress-corrosion environments or those fabricated from medium-thickness plates should undergo stress-relief annealing after welding or hot working. After explosive bonding of titanium-steel composite plates, stress-relief annealing should be performed. 　　5. The following welds in titanium pressure vessels shall be subject to penetrant testing: (1) The fillet welds connecting the nozzles, flanges, reinforcement rings to the vessel shell or head ； 　　(2) Welds connecting the heat exchanger tube sheet to the tubes ； 　　(3) The lap welds of the cladding welds on the titanium-steel composite plate, and the lap welds between the trim plates and the cladding of the composite plate. 　　Article 21: Nickel materials (referring to nickel and nickel-based alloys as well as their composite materials, the same below) used to manufacture pressure-bearing components of pressure vessels shall meet the following requirements: 1. Design temperature: Pure nickel in the annealed state shall not exceed 650°C; nickel-copper alloys shall not exceed 480°C; nickel-chromium-iron alloys shall not exceed 650°C; nickel-iron-chromium alloys shall not exceed 900°C. 　　2. Nickel alloys used for manufacturing the main pressure-bearing components of pressure vessels should be used in the annealed state, while linear nickel tubes for heat exchangers should be used after stress-relief annealing. 　　3. When hot-forming the pressure vessel heads in Nickel Village, the heating temperature must be strictly controlled. Ultrasonic testing should be performed on the formed nickel-steel composite plate seals. 　　4. The heating temperature, heating rate, and furnace atmosphere during hot forming in Nickel Village must be strictly controlled to prevent sulfur embrittlement contamination. The recommended hot working temperature range is: (1) for industrial pure nickel (N6-2.5-1,5), it is 280–350℃ ； 　　(2) Monel (NCU28-2.5-1.5) is 350～500℃ ； 　　(3) Inconel (NS312) is 470～550℃ ； 　　(4) Hastelloy (NS334) is for 930–1200°C. 　　5. The following welds of pressure vessels in Nickel Village shall be subject to magnetic particle or penetrant testing: (1) the fillet welds connecting the nozzles, flanges, reinforcement rings to the shell or head ； 　　(2) Welds connecting the heat exchanger tube sheet to the tubes ； 　　(3) Laminated welding joint of nickel-steel composite plate. 　　Article 22: Materials from abroad to be used for the pressure-bearing components of pressure vessels shall meet the following requirements: 1. Materials that are permitted under foreign pressure vessel codes and for which there are existing examples of use abroad shall be selected; their scope of use shall comply with the relevant codes and standards of the country where the material is produced, and a quality certificate for such material must be provided. 　　2. Before being used for the first time by the manufacturing unit, welding procedure qualification and welder testing must be carried out, and the chemical composition and mechanical properties must be rechecked; only after meeting the required specifications can production begin. 　　3. The technical requirements generally shall not be lower than the technical specifications of corresponding domestic materials. 　　4. Materials that are used for the first time in China and for which the specified minimum value for tensile strength in the standards is 540 Mpa or higher shall go through the approval procedures stipulated in Article 7 of these regulations. When domestic material manufacturers produce materials of foreign grades, they must follow the smelting methods specified in the foreign standards for those grades. The requirements regarding the shapes, sizes, processing conditions, and testing methods for tests of mechanical properties and bending strength must also comply with foreign standards. Before mass production, the product must undergo evaluation and approval by a **supervisory authority; in such cases, it can be treated as foreign steel in accordance with the provisions of this clause. 　　Article 23: When pressure vessels are prototyped using newly developed materials for their main pressure-bearing components (including imported materials for which there are no application examples domestically or internationally), or materials not listed in standards such as GB150, the manufacturers of such materials shall submit test data and third-party inspection reports to the National Pressure Vessel Standardization Technical Committee for technical evaluation. They must obtain a certification document issued by this committee granting permission for trial use (specifying the conditions under which the material may be used), and shall go through the approval procedures specified in Article 7 of these regulations. 　　Article 24 Pressure vessel manufacturing units shall ensure that the materials used for pressure vessels meet the relevant standards by means of retesting the materials or conducting inspections, evaluations, and follow-ups of the material suppliers. Before putting the vessels into use, they shall check for valid material quality certification documents and verify the valid markings on the materials as specified in Article 10 of these regulations. The material markings must exactly match the quality certificate; otherwise, it shall not be used. The material used to manufacture pressure components should be marked and transferred before cutting (or processing). 　　Article 25: Cylinder body, head (end cover) of pressure vessels, manway cover, manway flange, manway connection pipe, expansion joint, opening reinforcement ring, equipment flange ； Shell plates of spherical tanks ； Heat exchanger tube sheet and heat exchange tubes ； For equipment of class M36 and above, the main bolts, as well as pipes and pipe flanges with a nominal diameter of 250 mm or more, are considered to be primary pressure-bearing components. The reinspection requirements for these components are as follows: 1. The steel plates used in the manufacture of pressure vessels of category 3 must undergo reinspection. The re-inspection should include at least: checking the surface quality and material markings of each steel plate individually ； Recheck the chemical composition of the steel plate per furnace ； Inspect the mechanical properties and cold bending properties of the steel plate as approved ； When the steel plant does not provide a certificate of ultrasonic testing for the steel plates, re-ultrasonic testing shall be carried out in accordance with the requirements of Article 14 of these regulations. 　　2. Steel plates used for manufacturing pressure vessels of Category 1 and Category 2 shall be retested under any of the following circumstances: (1) When the design drawings require retesting ； 　　(2) Those requested by the user for re-inspection ； 　　(3) The manufacturing unit is unable to determine the authenticity of the materials or has doubts regarding their properties and chemical composition ； 　　(4) The steel quality certificate states that copies are invalid or not equivalent. 　　3. The re-inspection requirements for forgings used in the manufacture of Class III pressure vessels are as follows: (1) Re-inspection shall be carried out according to the items specified in the **standards for pressure vessel forgings or industry standards ； 　　(2) For outsourced forgings that are frequently used by the manufacturing unit and have a proven track record of quality, if the quality certification documents (originals) contain all necessary information, only retesting for hardness and chemical composition is required; if abnormal results are obtained in such retests, then retesting for mechanical properties is necessary ； 　　(3) forgings forged by pressure vessel manufacturing units for their own use may be exempted from re-inspection. 　　4. Materials that have obtained **product safety and quality certification from a supervisory authority and carry a mark indicating exemption from re-inspection can be exempted from re-inspection. 　　Article 26: Welding materials used for manufacturing the pressure-bearing components of pressure vessels shall be manufactured, inspected, and selected in accordance with relevant standards. Welding materials must have a quality certificate and clear, durable markings. Pressure vessel manufacturing units shall establish and strictly implement systems for the acceptance, retesting, storage, drying, distribution, and recycling of welding materials. 　　Article 27: Units responsible for the manufacturing or on-site welding of pressure vessels shall, in principle, obtain prior approval for material substitutions for the main pressure-bearing components from the design unit; the modified areas must be detailedly recorded in the as-built drawings. When the manufacturing unit has experience in using such materials and the properties of the substitute material are superior to those of the original material (this applies only to the interchange of steel plates from the 16MnR, 20R, and Q235 series, as well as forgings or steel pipes from the 16Mn, 10#, and 20# categories), the manufacturing unit bears corresponding responsibility and must also inform the original design unit. If the original design unit has objections, it should promptly convey those opinions to the manufacturing unit. Chapter 5: Installation, Operation, Management, Repair, and Modification Article 113: Units engaged in the installation of pressure vessels must be those that have obtained the corresponding manufacturing qualifications, or they must be installation units approved by the provincial safety supervision agency where the installation unit is located. Supervision engineers engaged in the supervision of pressure vessel installation should possess professional knowledge of pressure vessels, and must undergo training and assessments recognized by **the regulatory authority before they can work with a valid certificate. 　　Article 114: Before installing the following pressure vessels, the installation unit or the user unit shall submit an application to the safety supervision agency located in the area where the pressure vessel registration is kept, providing information such as the name and quantity of the vessels, as well as the manufacturer, user unit, installation unit, and installation location, in order to go through the installation procedures: 1. Pressure vessels of Category III. 　　2. Pressure vessels with a volume of 10 m3 or more. 　　3. Steaming ball. 　　4. Various types of pressure vessels installed simultaneously in a complete production plant. 　　5. Liquefied petroleum gas storage containers. 　　6. Medical oxygen chamber. 　　Article 115: When purchasing pressure vessels or issuing tenders for pressure vessel projects, the entities that use such vessels shall select pressure vessel design, manufacturing (or welding) units that possess the appropriate manufacturing qualifications. The technical responsible person of the using unit (the plant manager, director, or chief engineer) shall be accountable for the safety management of pressure vessels, and shall assign engineering and technical personnel with expertise in pressure vessels and familiarity with **relevant regulatory standards to handle the safety management of such vessels. 　　Article 116 The safety management tasks of entities that use pressure vessels mainly include: 1. Implementing these regulations as well as relevant technical standards and rules for pressure vessel safety. 　　2. Establish safety management regulations for pressure vessels. 　　3. Participate in the ordering of pressure vessels, the arrival of equipment at the site, installation and acceptance, as well as commissioning. 　　4. Inspect the operation, maintenance of pressure vessels, and the calibration of safety accessories. 　　5. Technical reviews for the inspection, repair, modification, and retirement of pressure vessels. 　　6. Prepare the annual regular inspection plan for pressure vessels and be responsible for its implementation. 　　7. Submit statistical reports to the competent authorities and local safety supervision agencies regarding the number of pressure vessels in use during the year and any changes in that number, the implementation status of regular inspection plans for these pressure vessels, as well as the main problems encountered and the actions taken to address them. 　　8. Rescue, reporting, assistance in investigations, and aftermath handling for pressure vessel accidents. 　　9. Management of safety technical training for inspectors, welders, and operators. 　　10. Registration of pressure vessel use and management of technical documents. 　　Article 117: The entities that use pressure vessels must establish technical records for such vessels, which shall be kept in a centralized manner by the management department. The contents of the technical file should include: 1. Pressure vessel file card (see Annex 4). 　　2. The pressure vessel design documents specified in Article 33. 　　3. The technical documents and materials for the manufacture and installation of pressure vessels as specified in Article 63. 　　4. Inspection and testing records, as well as technical documents and materials related to the inspections. 　　5. Repair plan, records of actual repair work, as well as relevant technical documents and materials. 　　6. Plans for the technical renovation of pressure vessels, drawings, material quality certificates, construction quality inspection technical documents, and related materials. 　　7. Records of inspection, repair, and replacement of safety accessories. 　　8. Records and handling reports related to the accident. 　　Article 118: The entities that use pressure vessels shall, prior to putting such vessels into use, proceed to the safety supervision agency or an authorized department to complete the registration procedures for each vessel in accordance with the requirements of the \"Rules for the Registration and Management of Pressure Vessel Use\". 　　Article 119: The entities that use pressure vessels shall specify the safety operation requirements for such vessels in their process operation procedures and job-specific operation procedures. These requirements shall include at least the following: 1. The operational parameters of the pressure vessel (including the maximum operating pressure, as well as the maximum or minimum operating temperature). 　　2. Operating procedures for pressure vessels (including startup and shutdown procedures and precautions). 　　3. Items and areas that require special attention during the operation of pressure vessels, possible abnormal phenomena that may occur during operation and preventive measures, as well as procedures for dealing with emergency situations. 　　Article 120: Operators of pressure vessels must hold a valid license to work. The entities that use pressure vessels shall provide regular professional training and safety education for the personnel responsible for operating such vessels. The assessment of this training is carried out by local or municipal safety supervision agencies, or by the authorized entities using the vessels. 　　Article 121: When a pressure vessel exhibits any one of the following abnormal conditions, the operator shall immediately take emergency measures and report to the relevant authorities in accordance with the prescribed reporting procedures. 　　1. When the operating pressure of the pressure vessel, the temperature of the medium, or the wall temperature exceeds the specified values, and measures taken still fail to achieve effective control. 　　2. Cracks, bulging, deformation, leakage, and other safety-threatening defects occur in the main pressure-bearing components of the pressure vessel. 　　3. Failure of safety accessories. 　　4. Damage to the connectors and fasteners makes it difficult to ensure safe operation. 　　5. Fires or other incidents that pose a direct threat to the safe operation of pressure vessels. 　　6. Overfilling. 　　7. The liquid level in the pressure vessel exceeds the specified limit, and measures taken fail to bring it under effective control. 　　8. Severe vibrations occur in pressure vessels and pipelines, posing a threat to safe operation. 　　9. Other abnormal conditions. 　　Article 122: No repairs shall be carried out on a pressure vessel when there is pressure inside it. For special production processes that require bolts to be tightened under temperature and pressure conditions ； In the event of an emergency leak that requires plugging it while the system is under pressure, the user entity must establish effective operational procedures and safety measures in accordance with the design specifications. The personnel involved must receive professional training and hold the necessary certifications to carry out these tasks, and their actions must be approved by the technical supervisor of the user entity. In actual operation, the safety department of the using unit should send personnel to conduct on-site supervision. 　　Article 123: Pressure vessels that generate steam using water as a medium must have proper water quality management and monitoring in place; they should not be put into operation without reliable water treatment measures. 　　Article 124: Units engaged in the repair and technical modification of pressure vessels must be those that have obtained the corresponding manufacturing qualifications, or units that have been approved by provincial safety supervision agencies. Plans for major repairs or modifications to pressure vessels must be approved by the original design unit or a qualified design firm, and submitted to the local or municipal safety supervision authorities where the work will be carried out for review and record-keeping. The repair or modification unit shall provide the user unit with technical documents such as the drawings after repair or modification, and construction certification documents. The major repairs for pressure vessels refer to the correction and repair of the main pressure-bearing components, as well as the welding repairs of joint seams in accordance with the provisions of Article 3 of these regulations. Major modifications to pressure vessels refer to changes in the structure of the main pressure-bearing components, or alterations to the operating parameters of the vessel, the medium it contains, or its purpose. After repair or modification, pressure vessels must ensure that their structure and strength meet the requirements for safe use. 　　Article 125: Before inspection and repair personnel for pressure vessels enter the interior of such vessels to carry out their work, the user entity must carry out the necessary preparations and clean-ups in accordance with the requirements of the \"Inspection Regulations for In-service Pressure Vessels\". Access is strictly prohibited when the requirements are not met. 　　Article 126: When repairing or modifying pressure vessels using welding methods, patching or replacement should generally be employed, rather than patch welding; furthermore, the following requirements must be met: 1. The technical requirements for patching or replacing sections of the pressure vessel, as well as for post-weld heat treatment, shall be determined by referring to the relevant manufacturing specifications, in order to formulate appropriate construction plans and technical requirements. The welding process must be approved by the welding technology supervisor. 　　2. After the defects are removed, surface non-destructive testing is generally carried out to confirm that the defects have been completely eliminated. After completing the welding work, non-destructive testing should be carried out to confirm that the repaired area meets the quality requirements. 　　3. The repaired area of the base metal must be ground smooth. The repair length after the removal of welding defects shall meet the requirements. 　　4. If heat treatment is required, it shall be carried out again after welding repair. 　　5. Pressure vessels whose main stressed components have a weld repair thickness greater than 1/2 of the wall thickness shall also undergo a pressure test. 　　Article 127: When the operating conditions of a mobile pressure vessel (medium, temperature, pressure, purpose) are changed, the entity using the vessel shall submit an application; upon approval by the provincial or **supervisory authority, the qualified manufacturing unit shall replace the safety accessories and repaint as well as re-label the vessel ； After internal and external inspections are carried out by a qualified inspection agency and an inspection report is issued, the user unit shall reapply for the use permit. 　　Article 128: Units responsible for loading and unloading mobile pressure vessels must obtain a safety registration for filling operations from the provincial safety supervision authority; only after approval may they carry out such filling tasks. Chapter 3 Design Article 28 The qualifications of design units for pressure vessels, as well as the classification of design categories and the scope of applicable types, shall comply with the provisions of the Rules for the Management and Supervision of Qualifications of Pressure Vessel Design Units. The design unit shall be responsible for the design quality. Pressure vessel design firms are not allowed to stamp their pressure vessel design qualification seal on drawings designed by other firms (except for those drawings designated by the authority responsible for approving such design firms). 　　Article 29: The general design drawing (blueprint) of a pressure vessel must bear the seal certifying the qualification for pressure vessel design (a photocopy of such seal is invalid). Drawings with an invalid design qualification stamp and those already stamped with the as-built stamp shall not be used for manufacturing pressure vessels. The design layout plan should bear the signatures of the design, verification, and approval (finalization) personnel. For medium-pressure reaction vessels and storage vessels, high-pressure vessels, and mobile pressure vessels in Category 3, the approval signature of the person in charge of pressure vessel design technology is required. 　　Article 30: The general design drawing of a pressure vessel shall indicate at least the following information: 1. The name and category of the pressure vessel. 　　2. Design criteria: A loading factor should be added for tanks storing liquefied petroleum gas ； For materials prone to stress corrosion, the limited content of the corrosive medium should be specified ； For time-sensitive materials, the compatibility of the working medium should be considered, and the service life of the pressure vessel should also be specified. 　　3. Material grade and requirements for the main stressed components. 　　4. Main characteristic parameters (such as the volume of pressure vessels, the heat exchange area and number of stages of heat exchangers, etc.). 　　5. Manufacturing requirements. 　　6. Heat treatment requirements. 　　7. Requirements for corrosion protection treatment. 　　8. Non-destructive testing requirements. 　　9. Requirements for voltage withstand test and airtightness test. 　　10. Specifications of safety accessories and special requirements for ordering. 　　11. Location of the chromium plate on pressure vessels. 　　12. Requirements for packaging, transportation, on-site welding, and installation. 　　13. Special requirements in the following situations: (1) For jacketed pressure vessels, the test pressures for the shell and the jacket, the allowable difference between the internal and external pressures, as well as the test procedures and requirements, shall be specified separately ； 　　(2) Reaction vessels equipped with catalysts and large pressure vessels containing fillers shall specify the technical requirements for regular inspections during use ； 　　(3) In cases where internal inspection is not possible due to structural reasons, the calculated thickness shall be indicated; for inspections at regular intervals during use, as well as pressure tests and airtightness tests, the calculated thickness and any special requirements regarding manufacturing and use shall be specified ； 　　(4) For those that cannot undergo pressure resistance tests and airtightness tests, the calculated thickness as well as the special requirements for manufacturing and use shall be specified, and the recommended service life and safety assurance measures shall be proposed in consultation with the user entity ； 　　(5) For reaction vessels with heat-resistant linings, the technical measures to prevent overheating of pressure-bearing components should be specified ； 　　(6) To prevent corrosion caused by the medium (stress corrosion), the requirements regarding the purity of the medium should be specified ； 　　(7) The anti-corrosion technical requirements should be specified for the steaming balls used in ammonium process papermaking ； 　　(8) Special requirements for the manufacturing and inspection of pressure vessels made of non-ferrous metals. 　　(9) The design pressure of pressure vessels shall not be lower than the maximum operating pressure; for pressure vessels equipped with safety relief devices, their design pressure shall not be lower than the opening pressure of the safety valve or the burst pressure of the rupture disc. 　　Article 31: When designing pressure vessels, sufficient corrosion margin shall be provided. The corrosion margin should be determined based on the expected service life of the pressure vessel and the rate at which the medium corrodes the material; it is also necessary to take into account the erosion and wear caused by the flow of the medium on the pressure vessel or its pressure-bearing components. When conducting structural design, the impact of local corrosion should also be taken into account to meet the safety requirements for pressure vessels. To prevent safety issues arising from the operation of pressure vessels beyond their designed lifespan, the design team should generally indicate the designed service life of the pressure vessel in the design drawings. 　　Article 32 The design documents for pressure vessels shall include design drawings, technical specifications, and strength calculation reports; where necessary, they shall also include design, installation, or operation manuals. 　　1. The design entity of the pressure vessel shall provide the user of the pressure vessel or the manufacturer of the pressure vessel with a design specification, design drawings, and technical requirements. 　　2. When required by the user, the design or manufacturing unit of the pressure vessel shall also provide the user with installation and operation instructions. 3. For mobile pressure vessels, high-pressure vessels, category III medium-pressure reaction vessels, and storage vessels, the design unit shall provide the user with a strength calculation report. 　　4. When designing in accordance with JB4732, the design entity shall provide a stress analysis report to the user entity. The contents of the strength calculation report should at least include: design conditions, all codes and standards, materials, corrosion allowance, calculated thickness, nominal thickness, calculated stress, etc. For pressure vessels equipped with safety valves and burst disc devices, the design entity shall provide the user unit with calculations regarding the safe discharge capacity of the pressure vessel, the discharge volume of the safety valve, and the discharge area of the burst disc. When calculation is not possible, the opinion of the user unit should be sought to negotiate the selection of a safety relief device. Any special requirements regarding process parameters, materials, manufacturing techniques, heat treatment, inspection, etc., should be specified in the contract. 　　Article 34 The design pressure for fixed pressure vessels used to hold liquefied gases is specified as follows: 1. The design pressure of fixed liquefied gas pressure vessels shall not be lower than the specified value. 　　2. The design pressure for fixed liquefied petroleum gas storage tanks shall be determined based on the actual saturated vapor pressures of the components in the mixed liquefied petroleum gas at 50°C or higher; the design entity shall indicate on the drawings the specified components and the corresponding pressures. If there is no actual component data or no component analysis is performed, the design pressure shall be no lower than the specified pressure. 　　Article 35: When designing storage containers, if the metal temperature of the shell is affected by the ambient air temperature, the minimum design temperature may be determined based on the meteorological data for that area, using the lowest value among the average monthly minimum temperatures over the years. The monthly average lowest temperature is calculated by adding up the lowest temperatures recorded on each day of the month and then dividing that total by the number of days in the month. The lowest value of the monthly average minimum temperature is the smallest value among the 10-year monthly average minimum temperature data measured by the meteorological agency. Areas across the country where the average monthly minimum temperature is less than or equal to minus 20°C and minus 10°C are listed in Appendix 2. 　　Article 36: The design storage capacity of pressure vessels used for storing liquefied gases shall comply with the following provisions: 1. For fixed pressure vessels containing liquefied gases (including liquefied petroleum gas), the design storage capacity shall be calculated using the following formula: W = фVρt, where W represents the storage capacity, and t… ； f – filling coefficient; generally taken as 0.9. For containers whose volume has been determined experimentally, a value greater than 0.9 may be used, but it must not exceed 0.95 ； V —— Volume of the pressure vessel, m3 ； ρt – Density of the saturated liquid at the design temperature, in t/m3. 2. The maximum allowable filling volume of a mobile pressure vessel filled with liquefied gas shall be calculated using the following formula: W = фvV, where W represents the maximum allowable filling volume, in t ； fv – the filling volume per unit volume, determined based on the 8% gas space remaining in the tank at 50°C and the density of the medium at that temperature, in t/m3. V – the actual volume of the tank, in m3. The design pressure, corrosion margin, and filling volume per unit volume for common media used in mobile pressure tanks are specified in Table 3-3. 　　Article 37: When designing storage containers for liquefied petroleum gas, the provisions of the industry standards HG20592–20635 shall be followed, and pipe flanges, gaskets, and fasteners with a pressure rating higher than the design pressure should be selected. For the first dust seal surface connected using flanges, a high-neck butt weld flange, a metal wound gasket (with an outer ring), and high-strength bolts should be used together. 　　Article 38: Facilities for filling shall generally not be installed on mobile pressure vessels, and filling pumps are strictly prohibited on liquefied gas tank cars. 　　The safety accessories of mobile pressure vessels include safety relief devices (such as built-in full-opening safety valves, rupture disc devices, fusible plugs, and rupture disc devices with fusible plugs), emergency shut-off devices, level indication devices, static discharge devices, thermometers, and pressure gauges, etc. Mobile pressure vessels whose filling medium is a liquefied gas or a cryogenic liquid shall be equipped with wave plates, and the volume of each wave damping section of the vessel shall generally not exceed 3 m3. Article 39: Mobile pressure vessels are classified into three types according to the design temperature: 1. Normal temperature type: The vessel has an exposed structure, with a design temperature ranging from -20 to -50°C. 　　2. Low-temperature type: The tank uses a stacked insulation design, with a designed temperature range of minus 70 to minus 20°C. 　　3. Cryogenic type: The tank uses vacuum powder insulation or vacuum multi-layer insulation, with a design temperature below minus 150°C. 　　When a mobile pressure vessel (for normal temperature conditions) is used to transport media other than those specified in Table 3-3, the determination of its design pressure, corrosion margin, and filling volume per unit volume shall be carried out by the design agency, which must provide data on the main physical and chemical properties of the medium, along with design specifications and the rationale therefor, for approval by the **supervisory authority. 　　Article 40: The strength calculation of the pressure-bearing components of steel pressure vessels, as well as the selection of allowable stresses, shall be carried out in accordance with the relevant provisions of standards such as GB150, GB151, GB12337, and JB4732. For certain compressed components with special structures for which strength calculations cannot be carried out using conventional standards, local analysis and calculation can be conducted by referring to the methods specified in JB4732; such standards are used for the analysis and calculation of compressed components in pressure vessels, and it is not necessary to have the qualification for stress analysis and design work. The strength calculation of the pressure-bearing components in pressure vessels made of non-ferrous metals (Note) can be carried out in accordance with the provisions of GB150 or relevant standards. The allowable stress can be determined in accordance with the provisions of relevant **standards and industry standards, or it can be calculated using the safety factors specified for mechanical properties as given in those same **standards and industry standards. 　　Article 41 For the strength design of the pressure-bearing elements in cast iron pressure vessels, the allowable stress is determined as follows: for gray cast iron, it is the tensile strength at the design temperature divided by a safety factor of 10.0 ； For malleable cast iron and ductile cast iron, the value is the tensile strength at the design temperature divided by a safety factor of 8.0. Article 42: For the strength design of the pressure-bearing elements in cast steel pressure vessels, the allowable stress is determined as follows: when the operating temperature is below 300°C, it is the material’s tensile strength divided by a safety factor of 4.0, multiplied by a casting factor; this factor shall not exceed 0.9 ； When the operating temperature is greater than 300°C, the value to be used is the yield strength of the material at that temperature divided by a safety factor of 1.5, multiplied by a casting coefficient; this coefficient shall not exceed 0.9. Article 43: For pressure vessels manufactured by welding, the welding joint coefficient shall be selected according to Table 3-5. When designed in accordance with the JB4732 standard, the welding joint factor is taken as 1.0. Article 44: The minimum wall thickness required for pressure vessels (excluding corrosion allowance) shall comply with the provisions of the relevant design codes and standards. 　　Article 45 Requirements for inspection holes in pressure vessels are as follows: 1. To check whether defects such as cracks, deformation, or corrosion occur in pressure vessels during use, inspection holes shall be provided in these vessels (except as specified in Article 46). Inspection holes include manholes and handholes. 　　2. The minimum number and minimum size of inspection holes shall meet the requirements. 　　3. The requirements for the location of inspection holes are as follows: (1) Inspection holes should be positioned reasonably and appropriately to facilitate observation or cleaning of the interior ； 　　(2) Manholes shall be provided on the head or on the cylinder near the head. 　　4. Spherical storage tanks should be provided with one manhole (or manufacturing process hole) on each of the upper and lower end plates. 　　Article 46 Pressure vessels that meet one of the following conditions may be exempt from having inspection holes: 1. Pressure vessels with an inner diameter of 300 mm or less. 　　2. The pressure vessel is equipped with removable end caps, covers, or other types of lids that can be opened and closed, and the dimensions of these end caps, covers, or lids are not smaller than those of the designated inspection holes. 　　3. Pressure vessels with no corrosion or only minor corrosion, that require no internal inspection or cleaning. 　　4. Pressure vessels for refrigeration units. 　　5. Heat exchanger. 　　Article 47: For pressure vessels that do not meet the conditions specified in Article 46 and for which it is not possible to install inspection holes due to special circumstances, the following requirements must also be satisfied: 1. 100% non-destructive testing (using X-rays or ultrasound) must be conducted on each longitudinal and circumferential weld. 　　2. The calculated thickness shall be indicated on the design drawings, and thickness measurements should be carried out regularly during the service of the pressure vessel or during inspections. 　　3. Correspondingly short inspection cycle. 　　Article 48: The types and technical requirements for the heads of steel pressure vessels, the design for strengthening the cylindrical portion under external pressure, as well as the connections to the vessel shell, the openings and dimensions of the shell, and the reinforcement requirements shall be in accordance with the relevant provisions of GB150 or JB4732. Pressure vessels made of non-ferrous metals shall meet the requirements of the corresponding standards. 　　Article 49: The quick-opening door (cover) of quick-opening pressure vessels shall be equipped with a safety interlock device and shall have the following functions: 1. An interlock control function that prevents pressurization until the quick-opening door reaches its designated closed position. 　　2. The interlock function for opening the quick-opening door can be activated only after the internal pressure of the pressure vessel has been completely released and the safety interlock device has been disengaged. 　　3. It has an alarm function that synchronizes with the aforementioned actions. 　　Article 50 For pressure vessels with insulation layers, if the designed insulation structure is non-removable, the drawings shall specify the requirement for comprehensive, regular, macroscopic inspections of the vessel’s insulation layer. If necessary, the drawing should specify special requirements such as non-destructive testing of all weld joints. 　　Article 51: The longitudinal joints of the cylinder body of welded pressure vessels, the circumferential joints connecting cylinder sections to end caps, as well as the joint seams of the end caps must all be of the butt joint type with full cross-sectional penetration. The shell plates of spherical storage tanks shall not be joined. The design of the butt joint can be carried out with reference to Appendix J of GB150 or Appendix H of JB4732. 　　Article 52: After verifying the strength of the fillet welds, the designer shall include the results of such strength verification in the design technical documents. 　　Article 53: Reinforcing rings installed on pressure vessels by welding, as well as gussets welded continuously around them to serve a reinforcing purpose, shall have at least one leakage signal indication threaded hole of size not smaller than M6. 　　Article 54: The design of pipe flanges, gaskets, and fasteners for steel pressure vessels shall comply with the provisions of the industry standards HG20592-20635. The design of the joints between the nozzles (flanges) of steel pressure vessels and the vessel shell, as well as the joint design for jacketed pressure vessels, can be referred to Appendix J of GB150 or Appendix H of JB4732. The fully penetrative type shall be adopted in any of the following situations: 1. Pressure vessels whose medium is flammable or possesses extremely high or high toxicity. 　　2. Pressure vessels for pressure testing. 　　3. Third category of pressure vessels. 　　4. Low-temperature pressure vessels. 　　5. Design pressure vessels according to fatigue criteria. 　　6. Pressure vessels directly heated by flames. 　　7. Mobile pressure vessels. 　　Article 55: The support between the inner tank and the shell of cryogenic mobile pressure vessels must be firm and reliable. The layout of the tank body in such mobile pressure vessels should be reasonable, and the connection structure and fixing devices between the tank body and the chassis must be capable of withstanding vibrations and shocks during transportation, as well as having sufficient stiffness and strength to resist inertial forces. 　　Article 56: The requirements for post-weld heat treatment of steel pressure vessels or pressure components shall, in addition to meeting the provisions of these regulations, also comply with the relevant requirements of standards such as GB150 or JB4732. Any special heat treatment requirements for the material should be indicated on the design drawings. 　　Article 57: The heat treatment of austenitic stainless steel pressure vessels generally refers to solution treatment at 1100°C or stabilization treatment at 875°C. 　　Article 58: When the medium contained in a pressure vessel is highly toxic or extremely hazardous, or when even trace leaks are not permitted, requirements for a gas-tightness test of the pressure vessel shall be specified in the design. For gas-mediated cast pressure vessels, requirements for airtightness testing should also be specified in the design drawings. 　　Article 59: The water quality used in pressure vessels and shell-and-tube waste heat boilers that are directly heated by flames and operate continuously, with a design pressure of 2.5 Mpa or less and using water as the working medium, must comply with the requirements specified in GB1576 \"Water Quality for Low-Pressure Boilers\". The water quality requirements for the aforementioned equipment with a design pressure greater than 2.5 Mpa are specified by the design unit in the design drawings. 　　Note: 1. For the wall thickness of cylindrical and spherical shells under external pressure, it can be calculated by referring to the calculation charts for similar or equivalent materials in domestic standards, based on the grade of the selected colored metal material. 　　2. For materials whose tensile strength has been increased due to cold or hot working, or heat treatment, when used in the manufacture of welded pressure vessels, the allowable stress for their weld joints shall be determined using the allowable stress value of the material in its annealed state. 　　3. When the design temperature of the air separation equipment is below 20°C, the performance shall be calculated based on 20°C. Chapter 6: Periodic Inspections Article 129: The entities responsible for periodic inspections of pressure vessels, as well as the inspectors themselves, must obtain qualification recognition from provincial or relevant regulatory authorities, pass the necessary qualification assessments, and be under the supervision of local safety regulatory bodies. They must carry out inspection work strictly within the scope approved and authorized for them. The inspection unit and inspectors shall be responsible for the results of the regular inspections of pressure vessels. 　　Article 130: The entities that use pressure vessels and the authorities in charge of them must arrange for regular inspections of such vessels in a timely manner, and submit the annual inspection plans for these vessels to the local safety supervision authorities as well as the inspection agencies. The safety inspection agency is responsible for supervision and inspection, while the testing unit is responsible for carrying out the testing tasks. 　　Article 131: In-use pressure vessels shall undergo regular inspections, safety assessments, and registration in accordance with the Provisions for Inspection of In-Use Pressure Vessels and the Rules for the Registration and Management of Pressure Vessel Use. 　　Article 132: The periodic inspections of pressure vessels are divided into: 1. External inspection: This refers to regular on-line inspections of pressure vessels while they are in use, to be carried out at least once a year. External inspections can be carried out by pressure vessel inspectors qualified by inspection agencies, or by specialized personnel from the using unit who have been approved by safety supervision authorities. 　　2. Internal and external inspections: refer to the inspections conducted when a pressure vessel in use is shut down. Internal and external inspections shall be carried out by qualified pressure vessel inspectors from the inspection agency. Its inspection cycle is divided as follows: (1) For those with a safety rating of 1 or 2, inspections must be carried out at least once every six years ； 　　(2) For those that are safe and rated at level 3, at least once every 3 years. 　　3. Pressure test: Refers to the hydraulic or pneumatic test carried out during the shutdown inspection of pressure vessels, at a pressure higher than the maximum operating pressure. For fixed pressure vessels, a pressure resistance test must be carried out at least once during the inspection period every three years; for mobile pressure vessels, such a test must be conducted at least once every 6 years. The provisions regarding external inspections, internal and external testing contents, and safety classification levels shall be in accordance with the \"Inspection Regulations for In-service Pressure Vessels\". 　　Article 133: The general period for the first internal and external inspection upon commissioning is 3 years. The subsequent internal and external inspection schedules shall be determined by the inspection agency in consultation with the user unit, based on the results of previous internal and external inspections, and then submitted to the local safety supervision authority for record-keeping. For pressure vessels that fall under any of the following conditions, the external inspection interval should be reduced accordingly: 1. When the degree of corrosion of the pressure vessel material by the medium is unknown, or when the corrosion rate of the material caused by the medium is greater than 0.25 mm/year, or when the corrosion data determined by the designer do not match the actual situation. 　　2. Poor surface quality of the material or internal defects, poor weldability of the material, or multiple revisions during manufacturing. 　　3. In conditions of harsh operation or when the hydrogen sulfide and sulfur content in the medium is high (generally referring to levels above 100 mg/L). 　　4. Those that have been in use for over 20 years, and which, after technical assessment or as confirmed by inspectors, cannot be used safely within a normal inspection cycle. 　　5. Those that have been out of use for more than two or three years. 　　6. Continue to be used after passing the defect safety assessment. 　　7. Those that frequently change the medium used (such as printing and dyeing machines). 　　8. Glass-lined equipment. 　　9. Spherical storage tanks (manufactured from materials with σb≥540 Mpa; inspection inside the tank should be carried out one year after operation). 　　10. For media that are liquefied petroleum gas and have a tendency to stress corrosion due to hydrogen embrittlement, internal and external inspections shall be carried out annually or as needed. 　　11. For papermaking processes using the \"immonium method\" and without anti-corrosion measures, internal and external inspections should be carried out at least once a year, or more frequently as required by actual conditions. 　　Article 134: For pressure vessels with a safety and quality rating of 1 or 2, the internal and external inspection intervals may be appropriately extended under any of the following circumstances: 1. If the non-metallic lining is in good condition, the inspection interval may be extended, but not beyond 9 years. 　　2. The corrosion rate of the medium on the material is lower. 1 mm/year (based on actual measurement data); pressure vessels with a reliable corrosion-resistant metal lining (composite steel plates) or thermally sprayed metals (aluminum powder or stainless steel powder). If corrosion is minimal or the lining is in good condition, as confirmed through one or two internal and external inspections, the inspection interval can be extended, but it should not exceed 12 years. 　　3. The inspection cycle for containers holding angle media, as well as large pressure vessels containing fillers, shall be determined through consultation among the user unit, the design unit, and the inspection unit based on the design drawings and actual usage conditions, and shall be filed with the local safety supervision agency. 　　Article 135 Pressure vessels under any of the following circumstances shall undergo a pressure test after passing the external inspection: 1. Those that have been repaired or modified by welding, or whose main pressure-bearing components have been replaced. 　　2. Changing the operating conditions, exceeding the original design parameters, and resulting in a strength that is both high and sufficient, with compliance regarding nuclear standards. 　　3. Those that require lining replacement (before replacing the lining in severe cases). 　　4. Those that were discontinued after being used duplicitously and then reused again. 　　5. Units in use that are newly installed after being transferred from other units, or relocated within the same unit. 　　6. The user entity has doubts regarding the safety of the pressure vessel. 　　Article 136: In addition to complying with the relevant provisions on pressure tests outlined in Chapter 4 of these regulations, the pressure resistance (airtightness) tests of pressure vessels in use must also meet the following requirements: 1. The disposal of the liquid used in the hydrostatic test, as well as any special treatments applied to the inner surfaces, shall be specified in the management regulations of the entity that operates the vessel. 　　2. For pressure vessels in use that contain flammable media, a thorough steam cleaning and conversion must be carried out prior to pressure or airtightness tests, with samples taken for analysis to confirm compliance; otherwise, air is strictly prohibited from being used as the testing medium. 　　Article 137: The periodic inspection items for low-temperature liquid (adiabatic) pressure vessels shall include at least the following: 1. Investigation of the user’s usage patterns: (1) Operation records, including frequency of use and operating conditions, as well as any abnormal occurrences ； 　　(2) Changes in daily evaporation rate, as well as whether frosting or other issues occur on the outer shell. 　　2. External inspection, as well as inspection of the shell structure and corrosion conditions. 　　3. Inspection and calibration of pressure gauges, safety valves, level gauges, and internal vessel burst disc devices. 　　4. Inspection of the piping system and valves. 　　5. If necessary, conduct a pneumatic pressure test on the inner tank using an appropriate medium. 　　Article 138: For pressure vessels whose design drawings prevent internal and external inspections or pressure resistance tests, the user unit shall submit an application; after approval by the local or municipal safety supervision agencies, it shall be filed with the provincial safety supervision agency. For pressure vessels that cannot undergo internal and external inspections or pressure tests on schedule due to special circumstances, an application must be submitted by the unit using the vessel, approved by the technical supervisor of that unit. After obtaining the consent of the original design unit and the inspection unit, and after filing the matter with the safety supervision agency responsible for issuing the \"Pressure Vessel Use Certificate\" following approval from the higher-level authorities in charge, the inspection or test can be postponed or waived. For pressure vessels that cannot undergo internal and external inspections as well as pressure tests, or for which such inspections and tests cannot be carried out on schedule, reliable monitoring and emergency response measures must be established. If problems arise due to the failure to implement these monitoring measures, the using unit shall be held responsible. 　　Article 139: For large, critical pressure vessels in use, regular inspections reveal a large number of severe defects that are difficult to repair. When the user entity, due to urgent production needs, must determine through a safety assessment of the defects whether the equipment can be used until the next inspection cycle or until it is replaced, it shall follow the procedures and requirements outlined below: 1. The user entity of the pressure vessel shall submit a written request to the **supervisory authority, having first obtained the approval of the entity’s supervising department as well as the provincial safety supervision authority in the location where the vessel is situated. The reason should be stated at the time of application, and the inspection report for the equipment should also be submitted. 　　2. For the safety assessment of defects in operating pressure vessels, the **assessment color** system is adopted, with supervision agencies approving each item individually. The entity using pressure vessels shall enter into a safety assessment contract for defects in such vessels with an assessment body that has been approved by the **supervisory authority and possesses the appropriate inspection qualifications. 　　3. The units responsible for conducting safety assessments of defects in pressure vessels in use must provide clear assessment conclusions based on the nature of the defects, the causes behind them, and predictions regarding their development, explaining the impact on safe operation. These include: usage conditions, monitoring measures for use, and the usage period, which should not exceed one inspection cycle. 　　4. The units responsible for the safety assessment of defects in pressure vessels in use must be accountable for the inspection results of those defects, the conclusions drawn regarding those defects, and the safety performance of the pressure vessels for continued use, and must assume corresponding responsibilities. The evaluation report and conclusions must be reviewed by the technical supervisor of the evaluating unit and approved by the legal representative. They are to be sent to the entity that operates the pressure vessel in question, as well as to the competent authorities of that entity and to the provincial and municipal safety supervision agencies. 　　5. The user entity shall, based on the evaluation report and conclusions, propose measures for supervised use as well as conditions restricting such use, and go through the procedures for supervised use at the local safety supervision authority in accordance with relevant regulations. Chapter 7 Safety Accessories Article 140: The safety valves, rupture disc devices, emergency shut-off devices, pressure gauges, level gauges, temperature measuring instruments used in pressure vessels, as well as the safety interlock devices for quick-opening pressure vessels, shall comply with the provisions of these regulations. The units that manufacture rupture disc devices must hold a manufacturing license issued by the **Quality and Technical Supervision Bureau. Units that manufacture safety valves, emergency shut-off devices, level gauges, and safety interlock devices for quick-opening pressure vessels must be approved by a safety supervision agency at or above the provincial level (including provincial agencies). 　　Article 141: Pressure vessels in use within the scope of application of these regulations shall be equipped with safety relief devices (safety valves or burst discs) in accordance with the design requirements. When the pressure source is external to the pressure vessel and can be reliably controlled, a safety relief device does not need to be installed directly on the pressure vessel. 　　Article 142: When a safety valve cannot operate reliably, a burst disc device shall be installed, or a structure combining a burst disc device with a safety valve device shall be employed. When a composite structure is used, the relevant provisions of Appendix B of GB150 shall be complied with. Any burst disc connected in a composite structure must not generate fragments when it activates. 　　Article 143: The design and manufacture of safety accessories shall comply with the corresponding **standards and industry standards. 　　Article 144: For pressure vessels containing flammable media or media with an extremely high, high, or moderate degree of toxicity, ducts shall be installed at the discharge outlets of safety valves or rupture discs to direct the discharged media to a safe location where they can be properly disposed of; such media shall not be discharged directly into the atmosphere. 　　Article 145: The discharge capacity of safety valves and rupture discs must be greater than or equal to the safe discharge capacity of the pressure vessel. The calculation of discharge capacity and safe release volume is provided in Appendix 5. For pressure vessels filled with a gas-liquid mixture in a saturated or superheated state, the design of the rupture disc device requires calculating the discharge diameter to ensure that no spatial explosion occurs. 　　Article 146: When only one safety valve is installed on a fixed-pressure vessel, the opening pressure Pz of that safety valve shall not be greater than the design pressure P of the vessel, and the sealing test pressure Pt of the safety valve shall be greater than the highest operating pressure Pw of the vessel; that is, Pz ≤ P and Pt > Pw. When multiple safety valves are installed on a fixed-pressure vessel, the opening pressure of one of those safety valves shall not be greater than the design pressure of the vessel, while the opening pressures of the remaining safety valves may be increased appropriately, but must not exceed 1.05 times the design pressure. 　　Article 147: The opening pressure of the safety valve on mobile pressure vessels shall be 1.05 to 1.10 times the design pressure of the vessel; the rated discharge pressure of the safety valve shall not exceed 1.2 times the design pressure of the vessel, and the reset pressure shall not be less than 0.8 times the opening pressure. 　　Article 148: When a rupture disc device is installed on a fixed-pressure vessel, the designed burst pressure PB of the rupture disc shall not be greater than the designed pressure of the vessel, and the minimum designed burst pressure of the rupture disc shall not be less than 1.05 times the highest operating pressure PW of the vessel; that is, PB ≤ P, and PBmin ≥ 1.05Pw. Article 149: When designing a pressure vessel, if the maximum allowable operating pressure is used as the basis for selecting safety valves or rupture discs, this shall be indicated on the design drawings and on the vessel’s nameplate. 　　Article 150: Safety valves must be supplied with a product quality certificate upon leaving the factory, and a sturdy metal nameplate must be installed on the product. 　　Article 151: Lever-type safety valves shall be equipped with a device to prevent the weight from moving freely and guides to restrict the lever from extending beyond its limits ； Spring-loaded safety valves should be equipped with a lead seal to prevent the adjustment screws from being twisted arbitrarily ； A gravity-type safety valve should be equipped with a device to prevent the heavy disc from coming loose. 　　Article 152 The requirements for the installation of safety valves are as follows: 1. Safety valves shall be installed vertically, and shall be placed in the gas phase space above the liquid level of the pressure vessel, or on a pipe connected to the gas phase space of the pressure vessel. 　　2. The cross-sectional area of the connection pipe between the pressure vessel and the safety valve, as well as the openings in the fittings through which they connect, must not be smaller than the inlet cross-sectional area of the safety valve. The connecting pipes should be as short and straight as possible. 　　3. When two or more safety valves are installed at one connection port of a pressure vessel, the area at the inlet of that connection port shall be at least equal to the total cross-sectional area of the inlets of these safety valves. 　　4. It is generally not advisable to install stop valves between the safety valve and the pressure vessel. To enable online calibration of safety valves, a burst disc device can be installed between the safety valve and the pressure vessel. For pressure vessels containing media with extremely high, high, or moderate toxicity, flammable media, corrosive or viscous media, or valuable media, in order to facilitate the cleaning and replacement of safety valves, a shut-off valve may be installed between the safety valve (rupture disc device) and the pressure vessel only with the approval of the technical responsible person in charge of pressure vessel safety at the facility using the vessel, and provided that reliable preventive measures are put in place. During the normal operation of the pressure vessel, the stop valve must remain fully open (sealed with a lead seal or locked); the design and diameter of the stop valve must not interfere with the safe venting of the safety valve. 　　5. The installation location of the safety valve should facilitate inspection and maintenance. 　　Article 153: Before installation, a new safety valve must be adjusted according to its intended use before it can be installed and put into operation. 　　Article 154: A regular inspection system shall be implemented for safety accessories. The regular inspection of safety accessories is carried out in accordance with the provisions of the \"Inspection Regulations for In-service Pressure Vessels\". Where the Provisions for Inspection of In-service Pressure Vessels do not provide specific guidelines, the inspection agency shall prepare an inspection plan and submit it to the provincial safety supervision authority for approval. Safety valves should generally be calibrated at least once a year; when it is difficult to remove them for calibration, on-site calibration (in-line calibration) should be used. The rupture disc devices should be replaced regularly; those that have exceeded the maximum designed rupture pressure without rupturing must be replaced immediately ； Blowout valve devices used under harsh conditions should be replaced annually ； Generally, blast disc assemblies should be replaced within 2–3 years (except where the manufacturer specifies that the service life can be extended). Pressure gauges and temperature measuring instruments shall be calibrated within the periods specified by the user unit. 　　Article 155: The calibration unit for safety valves shall have calibration technicians, calibration equipment, instruments, and facilities suitable for such calibration work, and shall establish necessary rules and regulations. Inspectors should possess basic knowledge of safety valves, be familiar with and able to follow the relevant regulations and standards for safety valve inspection, and work with appropriate certifications; detailed records should be kept of the inspection work. Upon successful verification, the verifying entity shall issue a verification report and apply a lead seal to the safety valve that has passed the verification. 　　Article 156 On-site calibration of safety valves on in-use pressure vessels