Regulations on Safety Inspection of Pressure Vessels

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Regulations on the Safety Supervision of Pressure Vessels, Document No. Guo Fa 154 issued by the Quality and Technical Supervision Bureau. Chapter 1: General Provisions. Article 1: These regulations are formulated in accordance with the relevant provisions of the Interim Regulations on the Safety Supervision of Boilers and Pressure Vessels, in order to ensure the safe operation of pressure vessels, protect the lives and property of the people, and promote the development of the national economy. Article 2 The scope of application of these regulations is as follows: 1. These regulations apply to pressure vessels that meet the following conditions: (1) The maximum operating pressure (Pw) (Note 1) is greater than or equal to 0.1 Mpa (excluding hydrostatic pressure; the same applies hereafter); (2) The inner diameter (for non-circular cross-sections, it refers to the largest dimension) is greater than or equal to 0.15 m, and the volume (V) (Note 2) is greater than or equal to 0.25 m3; (3) The medium contained is a gas, liquefied gas, or a liquid whose maximum operating temperature is greater than or equal to its standard boiling point..(Note 3) 2. Chapters 3, 4, and 5 of these regulations apply to the following pressure vessels ； (1) Storage tanks or cylinder banks in boiler rooms that are not independent of mobile compressors and have a volume of 0.15 m3 or less; (2) High-pressure vessels with a volume of less than 0.25 m3; (3) Non-independent pressure vessels in cryogenic units, pressure vessels in direct-fired absorption refrigeration units, and cryogenic chambers in air separation equipment ； (4) Spiral plate heat exchanger ； (5) Pressure tanks in hydraulic automatic air-supplementing pressure water supply systems (towerless water supply), and gas or pressure water supply (foam-based) pressure tanks in fire protection systems ； (6) Pressure vessels for ion exchange or filtration in water treatment equipment, expansion tanks for hot water boilers ； (7) Fully enclosed vertical combined electrical apparatus (capacitor pressure vessel) specifically designed for the power industry ； (8) Tire vulcanizing machines and pressure-resistant rubber molds for rubber storage. 3. These regulations apply to the safety accessories used in the aforementioned pressure vessels, such as safety valves, rupture disc devices, emergency shut-off devices, safety interlock devices, pressure gauges, level gauges, and temperature measuring instruments. 4. The pressure vessels to which these regulations apply shall include, in addition to the vessel itself: (1) the welding groove of the first circumferential weld where the pressure vessel is welded to external pipes or devices, the first threaded joint in the case of threaded connections, the first flange sealing surface in the case of flanged connections, and the first sealing surface in the case of connections using special fittings or pipe components ； (2) Pressure-bearing cover for the opening part of the pressure vessel and its fasteners ； (3) Weld joints connecting non-compressed components to the pressure vessel body. Article 3 These regulations do not apply to the following pressure vessels: 1. Ultra-high pressure vessels. 2. Various types of gas cylinders. 3. Pressure vessels manufactured from non-metallic materials. 4. Nuclear pressure vessels, auxiliary pressure vessels on ships and railway locomotives, pressure vessels used in defense or **related equipment, pressure vessels operating under vacuum (excluding jacketed pressure vessels), and devices directly heated by flames falling within the scope of various boiler safety inspection regulations (such as flue-type waste heat boilers, etc.). 5. The maximum operating pressure under normal operation is less than 0. Pressure vessels with a pressure of 1 Mpa (including those that need to withstand a pressure greater than or equal to 0 momentarily during feeding or material handling processes). Pressure vessels with a pressure of 1 Mpa, excluding those that need to withstand a pressure of 0 or higher for a short period of time during processes such as disinfection and cooling. Pressure vessel of 1 Mpa). 6. Non-independent pressure-bearing components on the machine (including compressors, generators, pumps, diesel engine cylinders or pressure-bearing housings, etc., excluding drying drums in papermaking and textile machinery as well as auxiliary pressure vessels for compressors). 7. Shellless coil exchangers, corrugated plate exchangers, air-cooled exchangers, cooling tubes. Article 4: The design, manufacturing (welding), installation, use, inspection, repair, and modification of pressure vessels shall all be carried out in strict accordance with the provisions of these regulations. Safety supervision agencies for boilers and pressure vessels at all levels (hereinafter referred to as safety supervision agencies) are responsible for the safety supervision of pressure vessels and ensure the implementation of these regulations. Article 5 These regulations constitute the basic requirements for quality supervision and safety inspection of pressure vessels. In the event that any technical standards, departmental rules, or internal regulations of enterprises and institutions related to pressure vessels conflict with the provisions of these regulations, the latter shall prevail. Article 6 Pressure vessels falling within the scope of application of Article 2 of these regulations are classified into three categories (the pressure rating, type, toxicity level of the medium, and classification of flammable media for pressure vessels are shown in Annex 1): 1. Pressure vessels fall under Category 3 in any of the following situations: (1) High-pressure vessels ； (2) Medium-pressure vessels (only for media with extremely high and high toxicity) ； (3) Medium-pressure storage vessels (only for flammable or moderately hazardous media, with a PV product greater than 10 Mpa·m3); (4) Medium-pressure reaction vessels (only for flammable or moderately hazardous media, with a PV product greater than or equal to 0). 5 Mpa·m3); (5) Low-pressure vessels (for media with extremely high or high toxicity levels, and a PV product of 0.2 Mpa·m3 or greater) ； (6) High-pressure and medium-pressure shell-and-tube waste heat boilers ； (Note 4) (7) Medium-pressure glass-lined pressure vessels ； (8) Pressure vessels manufactured from materials with a high strength level (meaning that the minimum specified value for tensile strength in the relevant standards is 540 Mpa or higher) ； (9) Mobile pressure vessels, including railway tank cars (for liquefied gases and cryogenic liquids), tank trucks, and tank containers (for liquefied gases and cryogenic liquids), etc ； (10) Spherical storage tanks (volume greater than or equal to 50 m3) ； (11) Storage vessels for cryogenic liquids (volume greater than 5 m3). 2. A pressure vessel falls under Category II in one of the following situations (except as specified in Paragraph 1 of this article): (1) Medium-pressure vessels ； (2) Low-pressure vessels (media with extreme and high toxicity levels) ； (3) Low-pressure reaction vessels and low-pressure storage vessels (for flammable media or media with moderate toxicity) ； (4) Low-pressure shell-and-tube waste heat boiler ； (5) Low-pressure glass-lined pressure (6) Pressure vessel. 3. Low-pressure vessels are classified as Class 1 pressure vessels (except as provided in paragraphs 1 and 2 of this article). Article 7: When designing and manufacturing pressure vessels whose technical requirements and operating conditions do not comply with the provisions of these regulations, it is necessary, on the basis of academic research and experimental studies, to submit the basis, conditions, data, results of the conducted tests, as well as third-party inspection reports and other relevant technical documents to the provincial safety supervision agency for review. Only upon approval by this safety supervision agency may trial production and testing be carried out. After verification through a certain period of trial use, type tests or technical evaluations are carried out, and the results are filed with the **safety supervision agency. Article 8: The design and manufacturing of pressure vessel products (including welding, the same hereinafter) shall comply with the requirements of relevant **standards, industry standards, or corporate standards. To directly adopt international standards or advanced foreign standards, they must first be converted into enterprise standards, and such standards shall comply with the provisions of Article 7 of these regulations. Design and manufacturing of pressure vessel products shall not be carried out in the absence of corresponding standards. Article 9: Foreign manufacturers of imported pressure vessels must obtain a safety and quality license issued by the **Quality and Technical Supervision Bureau. Imported pressure vessels shall undergo safety performance supervision and inspection in accordance with the \"Measures for the Supervision and Management of the Safety Performance of Import and Export Boilers and Pressure Vessels\", and shall be registered for use and subject to regular inspections as required by these regulations. For imported pressure vessels, or pressure vessels manufactured in domestic enterprises (including foreign-invested enterprises) using foreign technologies and standards for domestic use, if their technical requirements and operating conditions do not comply with the provisions of these regulations, the procedures specified in Article 7 of these regulations shall apply. Note 1: ① For pressure vessels subjected to internal pressure, the maximum operating pressure refers to the highest pressure that may occur at the top during normal use ； ② For pressure vessels subjected to external pressure, the maximum operating pressure refers to the highest pressure difference that may occur within the vessel during normal operation ； The jacketed vessel refers to the maximum pressure difference that can occur at the top of the jacket. Note 2: P represents the design pressure, PW represents the maximum operating pressure, and V represents the volume. Volume refers to the geometric volume of a pressure vessel, that is, the volume calculated from the dimensions specified in the design drawings (without considering manufacturing tolerances) and rounded off, without deducting the volume of the internal components. Multi-chamber pressure vessels (such as the tube side and shell side of heat exchangers, the drum and heat exchange chambers of waste heat boilers, jacketed vessels, etc.) are classified according to the chamber with the highest pressure, and are managed and used under that category. However, when categorizing by each pressure chamber, the design pressure shall be taken as this pressure, and the volume shall be taken as the geometric volume of that pressure chamber. Note 3: When the main medium inside the container is a liquid whose maximum operating temperature is below its standard boiling point, and the gas space (non-transient) is 0.025 m3 or more, along with a maximum operating pressure of 0.1 Mpa or more, it is also covered by the provisions of these regulations. Note 4: Includes pressure vessels whose application falls under pressure vessel categories and which are designed and manufactured primarily in accordance with pressure vessel standards and codes, and that are directly heated by flames. 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 **safety supervision agencies. The material manufacturer shall provide the user with a quality certificate (original) in accordance with the relevant standards, and shall affix a clear and durable stamp or other mark in a readily visible location on the material. Such 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 safety supervision 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 manufacturing unit. 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 account. The phosphorus content (as determined by melting analysis, the same applies hereafter) of steel dedicated for pressure vessels should not exceed 0.030%, and the sulfur content should not exceed 0.020%. When pressure vessels (except glass-lined pressure vessels) are manufactured using carbon steel boiling steel plates and carbon steel killed steel plates, they shall comply with the provisions of 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 conditions, such as when using steel with a carbon content exceeding 0.25%, the carbon equivalent shall be limited to no more than 0.45%. The manufacturer must obtain the user’s consent and get approval from the person in charge of pressure vessel technology at the manufacturer’s facility; in addition, a report on material crack susceptibility tests and a report on welding procedure qualification 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 subject 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 highly hazardous toxicity level. 2. Pressure vessels whose medium at mid-night is liquefied petroleum gas and whose sulfur and hydrogen content is 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 grade of the steel plates used for the containers referred to 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, while the qualified grade of the steel plates used for the containers specified in paragraph 4 of this article shall comply with the requirements of GB150, GB151, or GB12337. For mobile pressure vessel shells, 2 steel plates shall be sampled from each batch for Charpy (V-notch) low-temperature impact testing at a test temperature of minus 20°C or as specified in the drawings; the sampling direction for the test specimens shall be transverse. 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 specified in the product quality certificate. 2. The design pressure and design temperature shall comply with the following requirements: (1) The design pressure of gray cast iron pressure vessels shall not exceed 0.8 Mpa, and the design temperature shall be 0~250℃ ； (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 vessels shall not be used to hold media with an extreme, high, or moderate degree of toxicity, nor those with a design pressure of 0.0 Mpa or higher. The pressure-bearing components of flammable medium pressure vessels at 5 Mpa shall not be used either as pressure-bearing components in shell-and-tube waste heat boilers or in 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 for casting shall be specified in the product quality certificate. Cast steel materials should not be used for the pressure vessel shell and the sealing front (except where the pressure vessel manufacturer has prior experience in using such materials and it has been approved by the provincial or relevant safety supervision agency). 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 location 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 to 200°C. 2. When the design temperature is above 65°C, aluminum alloys with a magnesium content of 3% or more are generally not 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 sheets 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 manufactured 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, stiffeners 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, as well as 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 for manufacturing pressure vessel components must 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 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 in nickel village hot forming 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 930–1200°C. 5. The following welds of nickel alloy pressure vessels shall be subjected to magnetic particle or 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) Laminated weld 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 instances of use abroad shall be selected; their scope of use shall comply with the relevant codes and standards of the country of origin of the materials, and a quality certificate for such materials 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 shall generally 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 specified 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 products must undergo evaluation and approval by the relevant safety supervision authorities; in such cases, they can be treated as foreign steel products in accordance with the provisions of this clause. Article 23: When pressure vessels are prototype-tested 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 manufacturer of such materials shall submit the test data and third-party inspection reports to the National Pressure Vessel Standardization Technical Committee for technical evaluation. The committee shall issue a document granting permission for trial use (specifying the conditions under which the material may be used), and the approval procedures specified in Article 7 of these regulations shall be followed. 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 by inspecting, evaluating, and tracking 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 grade M36 and above, the main bolts, as well as pipe connections 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 be reinspected. 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 in accordance with 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 for which there is a guarantee of quality, such as those with complete items on the quality certificate (original), only retesting of hardness and chemical composition is required; if abnormal results are obtained from this retesting, then retesting of mechanical properties must be carried out ； (3) forgings forged by pressure vessel manufacturing units for their own use may be exempted from re-inspection. 4. Materials that have obtained a product safety and quality certification from a **safety supervision agency 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, re-inspection, storage, drying, distribution, and recycling of welding materials. Article 27: When manufacturing pressure vessels or carrying out on-site welding, units shall, in principle, obtain prior approval for design changes issued by the design unit before substituting materials for the main pressure-bearing components, and detailed records of such modifications shall be made in the as-built drawings. When the manufacturing unit has experience in using such materials and the performance of the substitute material is superior to that of the original material (applicable only to the interchange of steel plates in the 16MnR, 20R, Q235 series, as well as forgings or steel pipes of 16Mn, 10#, and 20# grades), and provided that the manufacturing unit assumes corresponding responsibility, it 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 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 designs, 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 permitted to affix their pressure vessel design qualification stamp on drawings designed by other firms (except for those drawings designated by the authority authorized by the pressure vessel design firm). 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 a completion stamp shall not be used for manufacturing pressure vessels. The design general plan should bear the signatures of the design, verification, and approval (finalization) personnel. For the 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. Name and category of the pressure vessel. 2. According to the design requirements, a loading factor should be added for storage tanks used to store liquefied petroleum gas ； For materials prone to stress corrosion, the allowable concentration 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 grades and requirements for the main stressed components. 4. Main characteristic parameters (such as the volume of pressure vessels, 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 the pressure vessel. 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 must 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) Where internal inspection is not possible due to structural reasons, the calculated thickness shall be indicated; for regular inspections 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 unit ； (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. Article 31: 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 32: 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 performing 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 33 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 operating instructions. 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 unit 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 unit with a strength calculation report. 4. When designing in accordance with JB4732, the design unit shall provide a stress analysis report to the user unit. 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 unit 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 agree on 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 containing liquefied gases is specified as follows: 1. The design pressure of fixed liquefied gas pressure vessels shall not be lower than the values specified in Table 3-1. Table 3-1 Design pressure of liquefied gas pressure vessels. 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 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 less than the pressure specified in Table 3-2. Table 3-2 Design Pressure for Mixed Liquefied Gas Pressure Vessels Article 35: When designing storage vessels, if the metal temperature of the shell is affected by the ambient air temperature, the lowest design temperature may be determined based on the meteorological data for that area, using the lowest value among the monthly average minimum temperatures recorded 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. Regions 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 designed 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 designed 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 with a liquefied gas as the medium shall be calculated using the following formula: W=фvV, where W is the maximum allowable filling volume of the vessel, in tons ； fv– the amount of material filled per unit volume, determined based on 8% of the tank volume being occupied by gas at 50°C and the density of the material 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 the common media in mobile pressure vessel tanks are selected according to Table 3-3. Table 3-3: Design pressure, corrosion margin, and content per unit volume for common media. Article 37: When designing storage containers for liquefied petroleum gas, it is necessary to follow the provisions of the industry standards HG20592–20635, and select pipe flanges, gaskets, and fasteners with a pressure rating higher than the design pressure. 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 trucks. The safety accessories of mobile pressure vessels include safety relief devices (built-in full-opening safety valves, rupture disc devices, fusible plugs, rupture disc devices with fusible plugs, etc.), emergency shut-off devices, level indication devices, static discharge devices, thermometers, pressure gauges, and so on. Mobile pressure vessels whose filling medium is a liquefied gas or a cryogenic liquid shall be equipped with surge plates, and the volume of each surge compartment in 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 tank structure, with a design temperature of minus 20 to 50°C. 2. Low-temperature type: The tank uses a piled-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 unit, 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 **safety supervision 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 based on the mechanical properties specified by those same **standards and industry standards along with the safety factors given in Table 3-4. Table 3-4 Article 41: Strength design of 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 ； Malleable cast iron and ductile cast iron are based on 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. and multiplied by the casting coefficient, a value for which should not exceed 0.9 ； When the operating temperature is greater than 300°C, the value is obtained by dividing the yield strength of the material at that temperature by a safety factor of 1.5 and then multiplying by a casting factor; this factor 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 set at 1.0. Article 44 of Table 3-5 states that the minimum wall thickness required for pressure vessels (excluding the corrosion allowance) must comply with the provisions of the relevant design codes and standards. Article 45 specifies the requirements for inspection holes in pressure vessels as follows: 1. In order to check for defects such as cracks, deformation, or corrosion in pressure vessels during use, inspection holes must 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 of Table 3-6. Table 3-6 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. 3. The spherical storage tank shall have 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 mild 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 reinforcement design of the outer pressure cylinder as well as its connection 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 relevant standards. Article 49: The quick-opening door (cover) of a quick-opening pressure vessel 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 predetermined 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 conducting 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, and 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 full penetration type shall be adopted in any of the following situations: 1. Pressure vessels whose medium is flammable or highly toxic or poses extreme hazards. 2. Pressure vessels for pressure testing. 3. Third category pressure vessels. 4. Low-temperature pressure vessels. 5. Design pressure vessels according to fatigue criteria. 6. Pressure vessels heated directly by flame. 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 4: Manufacturing I. General Requirements Article 60: Units engaged in the manufacturing of pressure vessels (including on-site welding, the same below) shall establish a quality assurance system for such vessels, prepare a quality assurance manual, and develop corporate standards (including management systems, procedural documents, work instructions, as well as standards for general processes and special methods), in order to ensure the safety and quality of the pressure vessel products. The legal representative of the enterprise must be responsible for the manufacturing quality of pressure vessels. The chief quality engineer for pressure vessels (with a Quality Assurance Engineering certificate) should be appointed by a representative of the enterprise management or by the person in charge of pressure vessel technology, and must hold a valid certificate obtained after completing relevant training and assessments. Article 61: Manufacturers of fixed-pressure vessels shall obtain a pressure vessel manufacturing license of grade AR or BR ； Manufacturers of mobile pressure vessels must obtain a CR-class pressure vessel manufacturing license ； And manufactured within the approved scope. Before mass production of fixed-pressure vessels, type tests shall be conducted ； Before mass production of mobile pressure vessels, type testing or technical evaluation must be carried out; only after registration with the **safety supervision agency can they be put into formal production. Manufacturing units shall strictly comply with **laws, regulations, administrative rules and norms, as well as standards, and manufacture and weld pressure vessels in strict accordance with the design documents. Article 62 The manufacturing unit must install a product nameplate and a registration nameplate in a prominent position on the pressure vessel (see Annex 6). Article 63: When pressure vessels leave the factory, the manufacturer shall provide the user with at least the following technical documents and information: 1. As-built drawings. The as-built drawings must bear the qualification seal of the design unit (a photocopyed seal is invalid). If there are any changes such as material substitution, alterations to non-destructive testing methods, or modifications to machining dimensions during manufacturing, the manufacturer shall directly indicate these on the as-built drawings in accordance with the requirements of the design modification notice. The marked area should contain the signatures of the person who made the changes and the reviewer, along with the date of the changes. The as-built drawings shall be stamped with the as-built seal, and they shall bear the name of the manufacturing unit, the manufacturing license number, and the words “As-Built Drawings”. 2. A certificate of product quality (see Annex 3 for details) and photocopies of the product nameplate. 3. Safety and quality supervision and inspection certificate for pressure vessel products (except for products that have not undergone such supervision and inspection). 4. Mobile pressure vessels shall also be provided with a product user manual (including instructions for the use of safety accessories), a list of tools and safety accessories included, as well as an instruction manual for the chassis. 5. The strength calculation report required under Article 33 of these regulations. The manufacturers of pressure vessel pressure-bearing components (heads, forgings, etc.) shall, in accordance with the relevant provisions of the product quality certificate for such components (see Annex 7), provide a quality certificate for those components to both the pressure vessel manufacturer and the user of the pressure vessel. Article 64: After the pressure vessel welded on-site is completed and inspected, in addition to providing the aforementioned technical documents and materials as required, the construction unit shall also supply the user with the technical data related to welding and quality inspection. The quality inspection of on-site welded pressure vessels should include the participation of representatives from the local safety supervision agency. Article 65 Mobile pressure vessels must undergo complete assembly of the tank body, safety accessories, and chassis by the manufacturing unit, and must pass pressure tests, airtightness tests, and other inspections before they can be released from the factory. Article 66 The manufacturing unit shall obtain written approval from the original design unit for any modifications to the original design, as well as corresponding certification documents, and shall keep detailed records of the modified parts (except in cases that meet the material substitution requirements specified in Article 27 of these regulations). II. Welding Processes and Welders Article 67: The requirements for evaluating welding processes for pressure vessels are as follows: 1. Before welding pressure vessel products, full penetration must be achieved between the pressure-bearing components and the non-pressure-bearing components. Article 68: Welders who work on pressure vessels must pass examinations in accordance with the \"Rules for Welding Examinations for Boilers and Pressure Vessels\"; only after obtaining a welder’s certificate can they carry out welding work within the scope of approved tasks during its valid period. Welders shall carry out welding in accordance with the welding procedure guide or welding procedure card. The manufacturing unit shall establish a welder’s technical file. The manufacturer’s inspector shall check the actual welding process parameters and keep records of them. Article 69 The requirements for welding pressure vessels are as follows: 1. Cross welds should not be used. The longitudinal seams between adjacent tube sections, as well as the welds used to join the end caps, should be offset from the longitudinal seams of the adjacent tube sections. The length of the outer arc between the centers of these welds should generally be more than 3 times the thickness of the cylinder wall, and at least 100 mm. 2. The gussets, pull plates, and other similar components welded to pressure vessels should be made of materials identical to those used for the vessel’s shell, or of materials with similar mechanical and welding properties; they should also be welded using appropriate welding materials and welding techniques. The weld scars remaining after the removal of the temporary lifting lugs and pull plates must be polished smooth, and penetrant testing or magnetic particle testing must be carried out as specified in the drawings to ensure that there are no defects such as cracks on the surface. The thickness after polishing should not be less than the designed thickness of that area. 3. Forced assembly is not allowed. 4. When tack welding is performed between compressed components or when compressive components are assembled with non-compressed components, and if it is to remain as part of the weld metal, it shall be welded in accordance with the requirements for welds on compressed components. Article 70: A welder’s identification stamp shall be affixed to the designated area 50 mm near the weld of the main pressure-bearing components of pressure vessels. For those that cannot be stamped, the welder’s code should be recorded using a diagram, and this diagram shall be included in the product quality certificate and provided to the customer. Article 71 The requirements for rework of welded joints are as follows: 1. The cause of the defect shall be analyzed, and a corresponding rework plan shall be formulated. 2. For rework, a detailed rework procedure must be prepared, and it can only be carried out after approval by the welding responsible engineer. The rework process should at least include the causes of the defects ； Technical measures to prevent the recurrence of defects ； Determination of welding process parameters ； Designation of welders for repairs ； Grade and specifications of welding materials ； Signatures of the person who developed the rework procedure and the person who approved it. 3. The number of rework attempts for the same area (referring to the area where the filler metal used for welding overlaps) should not exceed 2 times. If there are more than 2 repairs, approval from the technical director of the manufacturing unit is required. The number of repairs, the affected areas, the results of non-destructive testing after each repair, and the technical director’s approval signature must be recorded in the product manufacturing change report attached to the pressure vessel quality certificate. 4. The on-site records for repair work should be detailed, and should include at least the groove type and dimensions, the length to be repaired, the welding process parameters (welding current, arc voltage, welding speed, preheating temperature, interpass temperature, post-heating temperature and holding time), the grade and specifications of the welding material, the welding position, as well as the name of the welder and his/her signature. 5. For pressure vessels that require post-weld heat treatment, welding repairs shall be carried out prior to the heat treatment ； If welding repairs are carried out after heat treatment, heat treatment must be performed again after the repairs. 6. For austenitic stainless steel pressure vessels that require resistance to intergranular corrosion, the repaired areas must still maintain their original resistance to intergranular corrosion. 7. If repair is required after the pressure test, the repaired area must pass non-destructive testing in accordance with the original requirements. Pressure vessels that require repair due to leaks at weld joints or fittings, or those for which the repair depth exceeds 1/2 of the wall thickness, shall also undergo a pressure test again. III. Heat Treatment Article 72 Steel pressure vessels and their pressure-bearing components shall undergo post-weld heat treatment in accordance with the relevant provisions of GB150. When other stress-relief methods are used in place of post-weld heat treatment, approval procedures shall be followed in accordance with Article 7 of these regulations. Pressure vessel pressure components made of ferritic materials welded by electroslag welding, or those welded in the vertical position with high welding heat input, should undergo normalizing treatment to refine the grain structure after welding. Pressure vessels (storage vessels or mobile pressure tank bodies) containing mixed liquefied petroleum gas at room temperature shall undergo post-weld heat treatment. Spin-formed heads should undergo stress relief treatment after spinning (except for those made of austenitic stainless steel). Article 73 The post-weld heat treatment of steel pressure vessels shall meet the following requirements: 1. High-pressure vessels, medium-pressure reaction vessels and storage vessels, horizontal storage tanks for storing mixed liquefied petroleum gas, and mobile pressure vessels shall undergo overall heat treatment in a furnace. Other pressure vessels shall undergo overall heat treatment. For large pressure vessels, sectional treatment can be employed; the length of the overlapping heat-treated sections should be no less than 1500 mm, and insulation measures should be applied to the parts outside the furnace. 2. Local heat treatment can be used for the circumferential weld joints that have been repaired, as well as for the weld joints connecting the nozzles to the vessel body or heads. For welds that have undergone local heat treatment, the entire weld must be included. The heating width on each side of the weld shall be not less than 2 times the thickness of the base material; when joining a nozzle to the shell, the heating width shall be not less than 6 times the thickness of the thickest part (whichever is greater). The housing near the heating area should be insulated to prevent large temperature gradients from forming. 3. Post-weld heat treatment shall be carried out after all welding work is completed and the inspections are successful, prior to the pressure test. 4. The heat treatment apparatus (furnace) shall be equipped with temperature measuring instruments that can automatically record the temperature curve, and it must be ensured that the difference between the highest and lowest temperatures in the heating zone is no more than 65°C (except for spherical storage tanks). Article 74: Welded pressure vessels made of austenitic stainless steel or non-ferrous metals generally do not require heat treatment. If heat treatment is necessary due to special requirements, it shall be specified in the drawings. IV. External Inspection Article 75 The main control items for the manufacturing of cylinders (including spherical shells and inner cylinders of multi-layer pressure vessels) and end caps are as follows: 1. Groove geometry and surface quality. 2. The straightness of the cylinder body, the angle of its edges, the misalignment amount of the longitudinal and circumferential welds, and the difference between the maximum and minimum diameters at the same cross-section. 3. The loose area of the multi-layer wrapped pressure vessel and the gap in the fitting surface of the pressure vessel sleeve. 4. Splicing and forming of the end cap and major dimensional tolerances. 5. Dimensional tolerances and surface quality of the spherical shell. 6. Requirements for the butt joint of cylinders and end caps with varying thicknesses. Article 76 The surface quality requirements for the welded joints of pressure vessels are as follows: 1. The shape, dimensions, and appearance shall comply with the provisions of the thermal nuclear standards and design drawings. 2. There shall be no defects such as surface cracks, lack of penetration, lack of fusion, surface pores, arc pits, unfilled areas, and visibly visible inclusions; slag on the weld seam and spatter on both sides must be removed. 3. The weld shall transition smoothly to the base metal. 4. The requirements for undercut in welds are as follows: (1) For pressure vessels manufactured from steel with a minimum tensile strength of 540 Mpa or higher, as well as chromium-molybdenum low-alloy steel; for pressure vessels made from austenitic stainless steel, titanium, or nickel; for low-temperature pressure vessels, spherical pressure vessels, and those for which the weld coefficient is set at 1.0, there shall be no undercut on the surface of the welds ； (2) Except as specified in item (1) above, the root gap depth on the weld surface of pressure vessels shall not exceed 0.5 mm, the continuous length of root gaps shall not exceed 100 mm, and the total length of root gaps on both sides of the weld shall not exceed 10% of the length of that weld. 5. The root depth of fillet welds shall meet the requirements of technical standards and design drawings, with a smooth transition in shape. V. Requirements for Product Test Plates and Specimens Article 77 The requirements for welding test plates and specimens of pressure vessel products are as follows: 1. To examine the mechanical properties and bending performance of the product’s welded joints and other pressure-bearing components, longitudinal weld product welding test plates shall be fabricated, specimens shall be prepared, and tensile, cold-bending, and necessary impact tests shall be conducted. When manufacturing forged-welded pressure vessel products using new materials and new welding processes, welding test plates simulating ring welds should be prepared. 2. For those falling under one of the following circumstances, a product welding test plate shall be prepared for each pressure vessel: (1) Mobile pressure vessels (except those produced in batches) ； (2) Pressure vessels with a design pressure of 10 Mpa or higher ； (3) Spherical storage tanks welded in situ ； (4) Medium and high-pressure vessels manufactured from non-ferrous metals, or pressure vessels made of high-strength steel with an ab value of 540 Mpa or more ； (5) Pressure vessels welded from dissimilar steels (different groups) ； (6) Pressure vessels for which welding test plates are to be manufactured unit-by-unit as specified in the design drawings or per user requirements ； (7) GB150 stipulates that a welding test plate shall be prepared for each pressure vessel manufactured. 3. For pressure vessels other than those covered in Paragraph 2 of this article, if the manufacturer can provide test data from welding test plates of 30 consecutive units made from the same grade of material, using the same welding process (with the key welding parameters and additional key parameters remaining within the acceptable range; the same applies hereafter), and following the same heat treatment specifications (with the welding test plates and inspection reports to be archived for reference), thereby demonstrating stable welding quality, then with the approval of the technical supervisor of the manufacturer, it is permissible to produce welding test plates on a batch basis. The specific requirements are as follows: (1) Products of the same steel grade, using the same welding process and following the same heat treatment specifications should be produced in batches; production interruptions shall not exceed six months, and each batch shall consist of no more than 10 units. The manufacturer shall select one unit from this batch to use for producing the welding test plate ； (2) For pressure vessels with a design pressure not exceeding 1.6 Mpa and made of materials from the Q235 series, 20R, or 16MnR, products of the same steel grade shall be grouped together; one product per batch shall be selected for welding test plates to be manufactured at the beginning of each year ； (3) Laminated glass equipment does not require welded plates made of low-carbon steel (except when special requirements are specified). If production is interrupted for more than an hour past midnight, one unit of the product should be selected to create a welding test plate ； (4) For mobile pressure vessels produced in batches based on nearly identical design drawings, when manufactured manually in succession (with production interruptions not exceeding one year), no more than 10 units per batch shall be selected by the same manufacturing unit to be used for producing welding test plates. Welding test plates are produced in batches rather than one by one. If one of these test plates fails the tests, an additional number of test plates must be made for reinspection and metallographic analysis. If they still fail, the process must revert to producing welding test plates individually, until 30 test plates made from the same steel grade, using the same welding procedures and heat treatment specifications all yield satisfactory test results. 4. In addition to complying with the provisions of Paragraph 2, Article 3 of this clause, the preparation of product welding test plates shall also adhere to the following principles: (1) The materials, welding, and heat treatment processes used for the product welding test plates must fall within the range approved for the welding process evaluation of the welded joints of the pressure components they represent ； (2) When the scope of welding procedure qualification for different longitudinal weld joints on a pressure vessel’s shell (including those on the head, tube sheet, and cylinder) is different, separate welding procedures shall be applied to each type of longitudinal weld joint, with test plates welded accordingly ； (3) For pressure vessels with different requirements regarding post-weld heat treatment, separate welding test plates for the products should be prepared ； (4) When the inner and outer liner materials of a heat-exchange pressure vessel are different, one welding test plate should be fabricated for each material; if the materials are the same and fall within the same thickness range, only one test plate is required ； (5) For the on-site welding of spherical storage tanks, three welding test plates—vertical, horizontal, and overhead—should be prepared. Meanwhile, while the product is being welded on site, the welder responsible for welding that spherical storage tank should carry out the welding using the same conditions and welding techniques ； (6) The product welding test plate for the longitudinal weld joints of cylindrical pressure vessels shall, as an extension of the longitudinal weld joints of the vessel sections (except for electroslag welding), be continuously welded under the same conditions and using the same welding process as those applied to the actual pressure vessel ； (7) The product welding test plates for steel multi-layer wrapped pressure vessels and heat-shrouded pressure vessels shall be welded in accordance with the provisions of GB150 ； (8) The product welding test plates shall be welded by the welder who works on the product in question, and after welding, the welder’s and inspector’s identification stamps shall be applied to them ； (9) The product welding test plates are subject to visual inspection and radiographic (or ultrasonic) testing; if they fail these tests, repair is permitted. During repair, the requirements for repairing welded joints in Article 70 shall be complied with. If rework is not performed, a sample can be taken by avoiding the defective area. The requirements for product specimens of cast (forged) components, fittings, and studs shall be specified in the design drawings. 6. For pressure vessels that require heat treatment to meet or restore the mechanical properties, bending properties, or corrosion resistance requirements of the material, a heat-treated test plate made from the base material shall be prepared for each vessel, in compliance with the provisions of GB150. Article 78: The dimensions of the welding test plates for steel pressure vessel products, the method of sampling and the number of samples required, the testing items, the acceptance criteria, and the requirements for retesting shall be in accordance with the provisions of Appendix E to GB150, \"Inspection of the mechanical properties of welded joints of product welding test plates\". The sampling of pipe end specimens for butt welding, the test items, and the acceptance criteria shall be carried out in accordance with the relevant provisions of the «Regulations on Safety Supervision of Steam Boilers». The following pressure vessels shall undergo Charpy (V-notch) low-temperature impact tests in accordance with the requirements of GB150: 1. Pressure vessels manufactured from 16MnR and 15MnVR steel plates when the design temperature is below 38°C, as well as from 18MnMoNbR and 13MnNiMoNbR steel plates of any thickness. 2. When the design temperature is below -10°C, pressure vessels shall be manufactured using 20R steel plates with a thickness of more than 12 mm, and 16MnR, 15MnVR, and 15MnVNR steel plates with a thickness of more than 20 mm. 3. Mobile pressure vessels manufactured from low-alloy steel plates of any thickness. Article 79: The sample dimensions, sampling method, and quantity of welding test plates for pressure vessels made of non-ferrous metals may be determined in accordance with the requirements for steel pressure vessels or as specified in the drawings. The test items and acceptance criteria are as follows: 1. Tensile test – The tensile strength of the tensile test samples shall meet one of the following requirements: (1) Not lower than the lower limit specified in the standards for the base material ； (2) For welded joints formed from base metals of different strength grades, it shall not be lower than the lower limit of the specified value of the two tensile strengths. 2. Bending test: The diameter of the bending shaft, the distance between the supports, and the bending angle for the bending test shall comply with the specifications in Table 4-1. Table 4-1 3. Impact Test: When the design specifications require it or the material standards stipulate the use of an impact test, the acceptance criteria must comply with the relevant standards, and the average value of the three specimens shall be no lower than the lower limit specified for the base material. Article 80: For austenitic stainless steel pressure vessels required to undergo intergranular corrosion tendency testing, test specimens can be cut from the product material test plates, and the number of such specimens shall be no less than two. The type, dimensions, processing, and testing methods of the specimens shall comply with GB4334 \"Test Methods for Intergranular Corrosion Susceptibility of Stainless and Acid-Resistant Steels\". The evaluation of test results is carried out in accordance with the requirements of the product’s technical specifications or design drawings. VI. Non-Destructive Testing Article 81: Non-destructive testing personnel must undergo assessment in accordance with the \"Rules for Assessing the Qualifications of Personnel Engaged in Non-Destructive Testing of Boilers and Pressure Vessels\" and obtain a qualification certificate before they can carry out non-destructive testing tasks corresponding to the type and technical level of their qualification certificate. Article 82: For the welded joints of pressure vessels, inspections for shape, dimensions, and visual quality shall be carried out first; only after passing these inspections can non-destructive testing be performed. Materials prone to delayed cracking should undergo non-destructive testing 24 hours after welding is completed ； Materials prone to reheat cracking should undergo another non-destructive testing after heat treatment. Article 83 The non-destructive methods for pressure vessels include radiography, ultrasonic testing, magnetic particle testing, penetrant testing, and eddy current testing, etc. Pressure vessel manufacturers shall select the inspection methods and inspection lengths in accordance with the design drawings and relevant standard specifications. Article 84: The proportion of non-destructive testing for butt weld joints of pressure vessels is generally divided into two types: full (100%) and partial (20% or more). For ferritic steel cryogenic vessels, the proportion of localized non-destructive testing should be greater than or equal to 50%. Article 85: In any of the following situations, all radiographic or ultrasonic testing must be carried out on the butt joints of pressure vessels: 1. Pressure vessels for which all radiographic or ultrasonic testing is required according to standards such as GB150 and GB151. 2. Class III pressure vessels. 3. Reaction pressure vessels and storage pressure vessels for flammable media in the second pressure vessel. 4. Pressure vessels with a design pressure greater than 5.0 Mpa. 5. Design shell-and-tube waste heat boilers with a design pressure greater than 0.6 Mpa. 6. Pressure vessels with a weld coefficient of 1.0 shall be selected for design (except for seamless tube shells). 7. Pressure vessels designed using fatigue analysis. 8. Pressure vessels using electroslag welding. 9. Pressure vessels that cannot be subjected to internal or external inspections or pressure tests after use. 10. Pressure vessels made of aluminum, copper, nickel, titanium, or their alloys that meet one of the following conditions: (1) The medium is flammable or has an extremely high, high, or moderate level of toxicity ； (2) Those using pneumatic testing ； (3) Those with a design pressure of 1.6 Mpa or higher. Article 86 The selection requirements for inspection methods of welded joints in pressure vessels are as follows: 1. When the wall thickness of a pressure vessel is 38 mm or less, radiographic inspection shall be used for its butt joints ； When radiographic testing cannot be used due to structural reasons or other factors, recordable ultrasonic testing is permitted. 2. When the wall thickness of the pressure vessel is greater than 38 mm (or less than or equal to 38 mm but greater than 20 mm, and the minimum specified value for the tensile strength of the material used is greater than or equal to 540 MPa), if radiographic testing is employed for the butt joints, local ultrasonic testing shall also be carried out on each weld ； If ultrasonic testing is used, each weld shall also be supplemented with local radiographic testing. When radiographic testing or ultrasonic testing is not possible, other testing methods should be employed for additional local non-destructive testing. The additional local inspection shall cover all weld intersections, and the proportion of this additional local inspection shall be 20% of the original non-destructive testing proportion specified in Article 84 of these regulations. 3. For fillet joints and T-joints for which non-destructive testing is required, and when radiographic or ultrasonic testing is not possible, 100% surface inspection shall be carried out. 4. Magnetic particle testing should be given priority for surface inspection of ferromagnetic material containers. 5. Radiographic inspection should be preferably used for the butt joints of pressure vessels made of non-ferrous metals. Article 87: For other pressure vessels other than those specified in Article 85 of these regulations, their butt joints shall undergo local non-destructive testing and shall meet the requirements of Articles 84 and 86. The areas for local non-destructive testing are designated by the manufacturing unit’s inspection department based on actual conditions. However, all weld intersections as well as those weld areas covered by additional components in the open areas must be subjected to radiographic testing. The butt joints of welded end caps (excluding those that are first formed and then welded together) and welded tube sheets must undergo 100% ultrasonic or radiographic testing, with the acceptance criteria being the same as those for the corresponding butt joints of the pressure vessel shell. The welded head shall undergo non-destructive testing after forming; if non-destructive testing is carried out before forming, then non-destructive testing shall be performed again in the arc transition area after forming. For the welding joints of the upper and lower connection rings and jackets on glass-lined equipment, those of the nozzles of glass-lined equipment with a nominal diameter of less than 250 mm are exempt from non-destructive testing; however, a welding procedure qualification shall be carried out in accordance with JB4708, and a practical welding procedure specification shall be prepared. After approval by the technical director or chief engineer of the manufacturing unit, leakage tests shall be conducted on the welding joints connecting the upper and lower connection rings to the cylinder. For welded joints that have been subjected to local radiographic or ultrasonic testing, if any defects exceeding the specified limits are found at the tested areas, supplementary local testing covering at least 10% of the length of that welded joint shall be carried out promptly ； If it still fails, the entire weld joint in that section shall be inspected. Article 88: The non-destructive testing of pressure vessels shall be carried out in accordance with JB4730 \"Non-Destructive Testing of Pressure Vessels\". Full (100%) or partial (20%) non-destructive testing shall be carried out on the butt joints of pressure vessels: when radiographic testing is used, the quality of the inspections shall be at least grade AB, with a satisfactory grade of III; incomplete penetration is not allowed ； When ultrasonic testing is performed, its qualified grade is Grade II. For pressure vessels that are subject to 100% non-destructive testing as specified in standards such as GB150 and GB151, Class III pressure vessels, pressure vessels for which the weld coefficient is set at 1.0, and pressure vessels for which internal and external inspections or pressure tests cannot be carried out, 100% non-destructive testing must be conducted on their butt joints: when radiographic testing is used, the quality of the inspection shall not be lower than grade AB, and the acceptable grade is II ； When ultrasonic testing is used, the qualified grade is Grade I. The nominal diameter is 250 mm or more (or the nominal diameter is less than 250 mm). For pressure vessel nozzles with wall thicknesses greater than 28 mm, the proportion of non-destructive testing and the acceptance criteria for their butt joints shall be the same as those required for the welds in the main body of the pressure vessel ； For those with a nominal diameter of less than 250 mm and a wall thickness of 28 mm or less, only surface non-destructive testing is performed, and the acceptable quality level is Grade I as specified in JB4730. The acceptance level for non-destructive testing of butt joints in pressure vessels made of non-ferrous metals, as well as the quality requirements for radiographic inspection, are specified according to relevant standards or in the design drawings. Article 89: Full or partial non-destructive testing shall be conducted on the butt joints of pressure vessels; when both radiographic and ultrasonic methods are used, the results must be satisfactory. Their quality requirements and acceptable levels shall be determined in accordance with their respective acceptance standards. Article 90 For pressure vessels subjected to partial non-destructive testing, the manufacturer shall also be responsible for the quality of the untested portions. Article 91 The requirements for non-destructive testing of the surface of pressure vessels are as follows: 1. For the grooved surfaces, butt joints, corner joints, and T-joints of steel pressure vessels, if they meet the conditions specified in Article 69 of these regulations and the minimum required tensile strength of the materials used is 540 Mpa or higher, magnetic particle testing or penetrant testing shall be carried out in accordance with the relevant provisions of standards such as GB150, GB151, and GB12337. The inspection results must show no cracks, pores, or delamination, and must meet the Grade I requirements for the evaluation of trace defects as specified in the penetrant testing standards JB4730. 2. Pressure vessels made of non-ferrous metals shall be manufactured in accordance with the relevant standards or design drawings. Article 92 For pressure vessels assembled and welded on-site, surface non-destructive testing of the welds made on-site shall be carried out in accordance with standard specifications prior to the pressure test ； After the pressure test, local surface non-destructive testing shall be carried out in accordance with relevant standard specifications. If defects such as cracks are detected, additional testing shall be performed as specified by the standards; if it still fails to meet the requirements, then full surface non-destructive testing of that welded joint shall be conducted. Article 93: The manufacturing unit must maintain accurate records of non-destructive testing. The diagrams showing the areas to be inspected should clearly and precisely indicate the actual locations of the inspections (such as the position, numbering, and direction of radiographic tests), and reports must be issued correctly. Non-destructive testing records and film negatives (including those showing the original defects) or ultrasonic testing data must be stored properly, with a retention period of no less than seven years. If the user needs it seven years later, it can be handed over to the user for keeping. VII. Pressure test and airtightness test Article 94 The pressure tests for pressure vessels are divided into hydraulic tests and pneumatic tests. When the materials used for various components of a pressure vessel (cylinders, heads, nozzles, flanges, and fasteners) are different, the minimum value of the material/tonnage ratio for each component shall be used in calculating the pressure test requirement. The pressure resistance requirements for jacketed pressure vessels are as follows: 1. Jacketed pressure vessels whose design pressure of the inner cylinder is lower than that of the jacket ； For jacketed glass-lined equipment with a volume of 1000 L or less, with the approval of the technical responsible person of the manufacturing unit and the consent of the user, the hydraulic test on the inner cylinder may be waived, but the hydraulic test on the jacket cannot be waived. 2. For jacketed glass-lined equipment with a volume greater than 1000 L but less than or equal to 5000 L, after hydraulic testing has been conducted on 30 units of the same specification in succession, and with the approval of the technical supervisor of the manufacturing unit, testing can be carried out in batches of 15 units, with one unit taken from each batch for hydraulic testing (except as required by the customer). If that unit fails the test, hydraulic testing must be performed on each unit individually. 3. Jacketed glass-lined equipment with a volume greater than 5000 L shall undergo a hydraulic test for each unit. The pressure for the withstand test shall meet the requirements specified in the design drawings, and shall be no less than the value calculated using the following formula: Pr=ηP/t. Here, p represents the design pressure of the pressure vessel (for existing pressure vessels, this is generally the maximum operating pressure, or the maximum allowable operating pressure specified on the vessel’s nameplate, in Mpa) ； pr--pressure for withstand test, Mpa ； η--Voltage withstand test pressure coefficient, to be selected according to Table 4-2 ； Allowable stress of the material at the design temperature, MPa. Table 4-2 Article 95: During the pressure test, the circumferential membrane stress value of the pressure vessel shell shall meet the following requirements: 1. During the hydrostatic test, it shall not exceed the product of 90% of the material’s yield strength at the test temperature and the welding joint factor of the cylinder. 2. During the pressure test, the value shall not exceed the product of 80% of the material’s yield strength at the test temperature and the welding joint factor of the cylinder. When verifying the pressure for the pressure test, the wall thickness used should take into account the additional wall thickness; for the pressure used in the hydraulic test, the static pressure of the liquid column must also be included. For shell-and-tube heat exchangers where the shell side pressure is lower than the tube side pressure, no corrosion allowance need to be deducted. Article 96: Before the pressure test, all the fastening bolts at the connection points of the pressure vessel must be fully installed and properly tightened. The pressure gauges used for testing shall comply with the relevant provisions of Chapter 7; at least two pressure gauges with the same range and that have been calibrated shall be used, and they shall be installed at a position on the top of the container under test that is convenient for observation. Article 97: The voltage withstand test site must be equipped with reliable safety protection facilities, and it must be inspected and approved by the unit’s technical supervisor and safety department. During the voltage withstand test, no work unrelated to the test shall be carried out, and unauthorized personnel are not allowed to be present at the test site. Article 98 The requirements for hydraulic testing of pressure vessels are as follows: 1. Liquids that will not cause danger during testing can be used as hydraulic testing media at temperatures below their boiling point. Water should generally be used. When using flammable liquids for hydraulic testing, the test temperature must be below the flash point of the flammable liquid; there must be no sources of fire in the vicinity of the testing area, and appropriate firefighting equipment must be available. 2. Hydraulic testing is carried out using water as the medium, and the water used must be clean. When conducting hydraulic testing on austenitic stainless steel pressure vessels using water, the chloride ion content in the water must be strictly controlled to not exceed 25 mg/L. Once the test is passed, the water stains should be removed immediately. 3. The pressure vessel should be filled with liquid, and any gas remaining inside the vessel must be removed completely. The outer surface of the pressure vessel should be kept dry; pressure can be increased slowly to the design pressure only when the wall temperature of the vessel is close to the temperature of the liquid ； After confirming no leakage, continue to increase the pressure to the specified test pressure and hold it for 30 minutes. Then, reduce the pressure to 80% of the specified test pressure and hold it for a sufficient period of time for inspection. The pressure must remain constant during the inspection; continuous pressurization shall not be used to maintain the test pressure. During the hydraulic testing of pressure vessels, bolts must not be tightened under pressure, nor shall any external force be applied to the pressure-bearing components. 4. During hydrostatic testing of pressure vessels made of carbon steel, 16MnR, and normalized 15MnVR, the liquid temperature shall not be lower than 5℃ ； For other low-alloy steel pressure vessels, the liquid temperature must not be below 15°C. If factors such as plate thickness cause an increase in the material’s ductile transition temperature, the liquid temperature must be increased accordingly; the hydraulic testing temperature for pressure vessels made of other materials is specified in the design drawings. During the hydraulic testing of ferritic steel low-temperature pressure vessels, the temperature of the liquid should be 20°C higher than the higher of the specified temperatures for the Charpy impact test of both the vessel material and the welded joints. 5. The hydraulic testing procedure for heat exchange pressure vessels shall be carried out in accordance with GB151. 6. After the hydraulic test of the newly manufactured pressure vessel is completed, its interior should be dried using compressed air. Article 99 A pressure vessel after a hydrostatic test is considered qualified if it meets the following conditions: 1. There are no leaks. 2. No visible deformation. 3. No abnormal noises were heard during the test. 4. For materials whose specified minimum tensile strength is 540 Mpa or higher, no cracks were detected on their surfaces as a result of random non-destructive testing. Article 100 The requirements for the pneumatic testing of pressure vessels are as follows: 1. For pressure vessels in which it is not possible to fill them with liquid due to structural or supporting reasons, or those for which the operating conditions do not permit the retention of test liquid, pneumatic testing may be carried out in accordance with the provisions specified in the design drawings. 2. The gas to be used in the experiment should be dry and clean air, nitrogen, or other inert gases. 3. The temperature of the test gas for pressure vessels made of carbon steel and low-alloy steel shall not be lower than 15°C. For pressure vessels made of other materials, the temperature of the gas used for testing shall comply with the specifications in the design drawings. 4. During the pressure test, the safety department of the testing unit shall conduct on-site supervision. 5. The pressure should first be increased slowly to 10% of the specified test pressure, held at that level for 5–10 minutes, after which a preliminary inspection of all welds and joints should be carried out. If there is no leakage, the pressure can be increased further to 50% of the specified test pressure. If no abnormal phenomena occur, the pressure is then increased step by step to 10% of the specified test pressure, until reaching the test pressure, after which it is held at that level for 30 minutes. Then reduce it to 87% of the specified test pressure, and maintain that pressure for a sufficient duration for inspection; the pressure must remain constant during the inspection. Continuous pressurization shall not be used to maintain the test pressure constant. It is strictly prohibited to tighten bolts under pressure during the pressure test. 6. During the pressure test, if there are no abnormal noises from the pressure vessel components, and no leaks are detected using soap solution or other leak detection fluids, along with no visible deformation, then it is considered acceptable. Article 101: The airtightness test pressure for pressure vessels is the design pressure of the vessel. Article 102 The requirements for the airtightness test of pressure vessels are as follows: 1. Pressure vessels whose medium is extremely or highly toxic, or for which minor leaks are not permitted due to design considerations, must undergo an airtightness test. 2. The airtightness test shall be conducted after the hydraulic test is successful. It shall be specified in the design drawings whether pressure vessels required to undergo a pneumatic test according to the design requirements need to undergo an airtightness test as well. 3. For pressure vessels made of carbon steel and low-alloy steel, the temperature of the gas used for testing shall be no lower than 5°C; for pressure vessels made of other materials, it shall be as specified in the design drawings. 4. The gas used for the airtightness test shall comply with the provisions of Article 100, Paragraph 2 of these regulations. 5. When conducting a airtightness test on pressure vessels, safety accessories should generally be installed in their entirety. If it is necessary to install safety accessories on-site prior to commissioning, the report on the airtightness test provided in the pressure vessel quality certificate should indicate that an additional on-site airtightness test is required after the installation of those safety accessories. 6. After checking for leaks, maintaining the pressure for no less than 30 minutes qualifies it as successful. Article 103: The pressure test and airtightness test of pressure vessels made of non-ferrous metals shall comply with the provisions of relevant standards or the requirements of the design drawings. VIII. Expansion Joining Article 104: The manufacturing unit shall formulate an expansion joining process procedure based on the technical requirements specified in the drawings and the results of expansion testing. The expansion jointing operator must carry out the expansion jointing operations in strict accordance with the expansion jointing procedure. For the expansion joining of the heat exchange tubes and tube sheets in heat exchangers, flexible expansion joining methods can be used, such as hydraulic expansion, rubber expansion, and fluid-bag expansion. When there is prior experience, the mechanical expansion method can also be used; when opting for mechanical expansion, it is necessary to control the expansion ratio to ensure the proper degree of tightening. The expansion joint end shall be free from defects such as peeling, wrinkles, cracks, cuts, and misalignment. During the expansion joining process, the quality of the expanded joint should be checked at all times to identify and eliminate defects promptly. After the expansion joining is completed, a pressure test must be carried out to check the tightness of the expanded joint. Article 105 Basic requirements for expansion joining: 1. Requirements for flexible expansion joining: Flexible expansion joining is divided into adhesive expansion joining and strength expansion joining. The inner surface of the tube sheet holes does not need to be grooved during flanging. For strong expansion welding with a pleasant-looking finish, a rectangular groove should be created inside the hole; the width of this groove is (1. 1~1. 3) (where d is the average diameter of the heat exchange tube and t is the wall thickness of the heat exchange tube), the groove depth is 0. 5mm。 Before expansion joining, the expansion pressure should be calculated for proper expansion; at least 5 test specimens should be used for this purpose. The pull-out force q of the expanded joints should be measured, with a value of 1 MPA required for partial expansion joining and 4 MPA required for full strength expansion joining. During expansion joining, the specified pull-out strength can be achieved by appropriately increasing the expansion pressure. 2. Requirements for mechanical expansion joining: Before carrying out the actual expansion joining, a trial expansion should be performed first. During expansion, a comparative inspection of the specimen should be carried out to check for cracks in the expanded sections, any sudden changes in the transition areas where expansion occurs, and whether the connection between the base of the flared portion and the tube wall is proper. Additionally, the impressions and fit of the contact surfaces between the tube sheet holes and the outer wall of the tubes should be examined. Based on the expansion results, a reasonable tube expansion rate is determined. 9. Requirements for pressure vessels made of steel, cast iron, stainless steel, and non-ferrous metals – Article 106: For steel pressure vessels without longitudinal welds, the following requirements apply: 1. The design entity shall establish specific technical specifications that detail the requirements regarding material selection, design, manufacturing (machining, welding, heat treatment, etc.), inspection, and repair. 2. The elongation rate of the material used for forgings must be no less than 12%, and must not be lower than the value specified in the standards for forging materials. 3. The inner surface of the cylinder must be finely processed. The difference between the maximum and minimum inner diameters in the same cross-section shall not exceed 1 of the average inner diameter of that section. 0%. The roughness of the inner surface should not be less than 12. 5m。 4. The requirements for quality inspection shall be in accordance with JB4726~4728 \"Steel Forgings for Pressure Vessels\". 5. Before welding the forged parts, their weldability should be evaluated. Article 107 The requirements for cast-iron pressure vessels are as follows: 1. The entities that manufacture cast-iron pressure vessels must obtain prior approval from the **safety inspection agency in accordance with the procedures specified in Article 7 of these regulations. It should also possess the appropriate production capacity and experience, and its equipment must be capable of meeting the processing requirements for cast iron pressure vessels. 2. The surface of cast iron compression components after processing must be free of cracks ； In the event of casting defects such as shrinkage cavities, sand holes, pores, or shrinkage porosity, these shall not exceed the requirements specified in relevant standards or technical specifications. At the protruding edges and recessed corners, sufficient radius of curvature should be provided to avoid sudden changes in the surface shape and wall thickness at the joints. 3. The tensile strength and hardness requirements for cast iron pressure vessels must meet the specifications given in the design drawings. 4. Surface defects can be repaired by installing plugs, but the depth of the plug shall not exceed 40% of the cross-sectional thickness; the diameter of the plug head (the outer diameter of the thread) shall not exceed the depth of the plug head, nor shall it be greater than 8 MM. 5. For products manufactured in the first trial run, hydraulic failure tests should be conducted to verify the rationality of the design; if the tests fail, they shall not proceed to mass production. The experiment must have a comprehensive plan and reliable safety measures, and the test results should be submitted to the provincial safety supervision agency for record-keeping. Article 108: The manufacturing of pressure vessels made of stainless steel and non-ferrous metals, as well as their pressure-bearing components, must take place in dedicated manufacturing workshops or with specialized equipment and facilities; such production shall not be carried out alongside the manufacture of ferrous metal products or other goods. The workplace should be kept clean and dry, with dust strictly controlled. Additive forming equipment and welding equipment should be capable of meeting the requirements for stainless steel and non-ferrous metals. Surface mechanical damage and spatter must be strictly controlled. The surfaces of pressure vessels manufactured from austenitic stainless steels with corrosion resistance requirements and their composite steel plates shall undergo surface pickling and passivation treatment. Austenitic stainless steel components that require corrosion resistance undergo heat treatment as specified in the drawings, followed by pickling and passivation. Article 109 The other requirements for pressure vessels made of aluminum and aluminum alloys are as follows: 1. The corrosion tests on the base material and welded joints shall comply with specific technical specifications and design requirements. 2. The surface in contact with corrosive media should be free of mechanical damage and splatter. 3. All supports of horizontal pressure vessels must maintain full contact with the vessel itself. 4. The groove surface of the weld joint shall be prepared using appropriate methods; the surface must be smooth and even, and it should be thoroughly cleaned before welding. Article 110: The other requirements for pressure vessels made of titanium and titanium alloys are as follows: 1. The groove surfaces of welding joints must be prepared by mechanical methods. 2. Welding materials must undergo degassing and rigorous cleaning. 3. The personnel responsible for aligning the welded joints must wear clean gloves, and must not touch the groove or the areas surrounding it with their fingers. It is strictly prohibited to strike the surface of the titanium plate and the groove with iron tools. 4. Welding should be carried out immediately after the cleaning of the welded components is completed. 5. The purity of argon and helium used for welding should be no less than 99. 99%, the dew point should not be higher than minus 50°C. 6. Before welding titanium materials, the groove and the area within 25 MM on the side opposite it must be thoroughly mechanically cleaned and degreased. During the welding process, measures should be taken to prevent groove contamination. 7. Effective measures should be taken to prevent interdiffusion between steel and titanium during welding. When required by the pattern, an iron contamination test should be conducted. 8. During the welding process, after each weld is completed, it is necessary to check the color of the weld surface; the surface color of the weld and the heat-affected zone should be silver-white or golden-yellow. Those with unacceptable surface color should be completely removed and then rewelded. The inspection of surface color shall be carried out in accordance with the provisions of relevant standards. 9. Inert gas shielded arc welding or plasma welding must be used. The connection between titanium tubes and tube sheets should preferably be made using strength welding or welding after expansion. 10. The surface of the weld after welding must be free from defects such as undercutting, pores, cratering, and cracks. Article 111: The other requirements for pressure vessels made of copper and copper alloys are as follows: 1. The groove surface of welding joints and the areas adjacent to both sides thereof shall be carefully cleaned to reveal a metallic luster, and welding shall be carried out promptly. 2. If welding is carried out using a hydrogen-oxygen flame or an oxygen-acetylene flame, the following requirements must be met: (1) Use copper in its annealed state ； (2) Use bottled acetylene gas, and the purity of the acetylene gas should be controlled. (3) Depending on the material and welding process, preheating to the specified temperature range is required before welding ； (4) During multi-layer welding, the welding process should be completed continuously without interruption ； (5) An appropriate flux should be applied to the electrode or the workpiece to be welded ； (6) A neutral to slightly oxidizing flame should be used for copper-based materials, while a neutral to slightly reducing flame should be used for copper-nickel alloys ； (7) The welding ambient temperature should generally not be lower than 0°C; otherwise, preheating is required ； (8) Pure copper should not be welded using a hydrogen-oxygen flame; gas shielded welding or plasma welding can be used instead. Article 112: The requirements for pressure vessels made of nickel and nickel alloys are as follows: 1. The cutting of the material shall be carried out using shearing, mechanical processing, or appropriate thermal cutting methods (such as plasma cutting). After thermal cutting, the contaminated area on the cut edge should be removed by grinding, cutting, or other mechanical methods before use or welding. 2. When welding nickel materials, the groove and the area within 25 MM on each side thereof must be thoroughly mechanically cleaned to remove all oil stains and sulfur-containing impurities; after cleaning with a detergent, welding should be carried out promptly. The oxides on the surface of the intermediate weld bead should be removed by grinding until a metallic luster is exposed. 3. During welding, the welding heat input and interpass temperature should be strictly controlled. The interlayer temperature should generally not exceed 150°C. 4. The surface of the weld after welding must be free from defects such as undercut, pores, crater, and cracks. The surface color of the weld and heat-affected zone should be silver-white or yellow. 5. Before hot forming or heat treatment, all sulfur- or lead-containing contaminants such as oil, paint, and lubricants on the workpiece must be thoroughly removed. The sulfur content in the atmosphere of the heating furnace should be strictly controlled. The sulfur content of gas or natural gas used for heating should be less than 0.57 g/m3, while the sulfur content of fuel oil should be less than 0.5%; coke or coal shall not be used for heating. Chapter 4: Installation, Use, 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 complete training and assessments recognized by safety supervision authorities before they can take up their duties 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 details such as the name and quantity of the vessels, as well as the information on 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. Steam compress. 4. Various types of pressure vessels installed simultaneously in the integrated production facility. 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 design, manufacturing (or welding) units with 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 work of units using pressure vessels mainly includes: 1. Implementing these regulations as well as relevant safety technical standards and rules for pressure vessels. 2. Establish safety management rules and 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 pressure vessels, as well as the main problems encountered and the measures taken to address them. 8. Rescue, reporting, assistance in investigations, and follow-up actions 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 Attachment 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 plans, 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 start-up 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 who operate such vessels. The assessment of this training is the responsibility of local or municipal safety supervision agencies, or of 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 a timely manner 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. The safety attachment has failed. 4. The fittings are damaged due to takeover, making 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 vibration in pressure vessels and pipelines endangers 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 certificates 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 shall 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 straightening 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 by welding, patching or replacement should generally be used, rather than patch welding; furthermore, the following requirements must be met: 1. The technical requirements for patching, replacing cylinder sections of pressure vessels, and post-weld heat treatment shall be based on the corresponding manufacturing specifications, and construction plans along with appropriate technical requirements shall be formulated. The welding process must be approved by the welding technology supervisor. 2. After the defects are removed, surface non-destructive testing is generally performed 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 on the base material 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 **safety supervision agency, 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 submit an application for safety registration with the provincial safety supervision agency; only after approval may they carry out filling operations. Chapter 5: 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 supervision agencies, pass the required qualification assessment tests, and be under the supervision of local safety supervision agencies. 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 from qualified inspection agencies, or by specialized personnel from the using unit who have been approved by the safety supervision authorities. 2. Internal and external inspections: refer to the inspections carried out 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 as follows: (1) For those with a safety rating of 1 or 2, at least once every six years ； (2) For those that are safe and classified as level 3, at least once every 3 years. 3. Pressure resistance test: refers to the hydraulic or pneumatic test carried out during the shutdown inspection of pressure vessels, at pressures exceeding 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 grades shall be implemented 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 cycles 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 reported to the local safety supervision authority for record-keeping. For pressure vessels with any of the following conditions, the external inspection interval should be reduced appropriately: 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 environments with harsh operating conditions or high levels of hydrogen sulfide and sulfur in the medium (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. Laminating equipment. 9. Spherical storage tanks (manufactured from materials with σb≥540 Mpa; inspection inside the tank should be carried out one year after commissioning). 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 one 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 below 0.1 mm/year (based on actual measurement data); the pressure vessel is equipped with a reliable corrosion-resistant metal lining (composite steel plate) or thermally sprayed metal (aluminum powder or stainless steel powder). If it is confirmed through one or two internal and external inspections that corrosion is minimal or that the lining is in good condition, the inspection interval can be extended, but it should not exceed 12 years. 3. The inspection cycle for containers holding melon pests and 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 suitable, with compliance regarding nuclear standards. 3. Those that require lining replacement (before replacing the lining for severe cases). 4. Those that were stopped being used due to duplicity and then reused again. 5. Units that have newly installed them by transferring them from other units, or those that have moved them internally within their own 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. After the hydraulic test is completed, the disposal of the liquid used for the test, as well as any special treatments required for the inner surfaces, shall be specified in the management procedures of the entity using 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 conditions: (1) Operation records, including frequency of use and operating conditions, as well as any abnormalities that may have occurred ； (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 housing 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 do not permit internal or external inspections or pressure resistance tests, the using 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, external inspections or pressure tests on schedule due to special circumstances, an application must be submitted by the unit using the vessel, and it must be approved by the technical supervisor of that unit. The original design team and the inspection agency must also give their consent. After obtaining approval from the higher-level supervisory authority in charge, and after registration with the safety supervision agency that issues the \"Pressure Vessel Use Certificate,\" 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 application to the **safety supervision agency, having first obtained the approval of the entity’s supervising department as well as the provincial safety supervision agency 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 must also be submitted. 2. For the safety assessment of defects in in-service pressure vessels, the **Safety Assessment Color** system is used, with safety 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 possesses the appropriate inspection qualifications and has been approved by the **safety supervision agency. 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, thereby indicating 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 entity 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 units that use the pressure vessels in question, as well as to the competent authorities of those units and to the provincial and municipal safety supervision agencies. 5. The entity using the equipment 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 agency in accordance with relevant regulations. Chapter 7 Safety Appendices 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 is under reliable control, a safety relief device need not 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 disks to direct the discharged media to a safe location where they can be properly disposed of; such media shall not be released 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 venting 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 that the discharge diameter be calculated to prevent a spatial explosion. 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 exceed 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 reseating 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, as well as 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 space above the liquid level of the pressure vessel, or on a pipe connected to the gas 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 these pipes pass, 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 on a 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 rupture 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, provided that it is approved by the technical responsible person in charge of pressure vessel safety at the unit using the vessel, and reliable preventive measures are put in place. During the normal operation of the pressure vessel, the stop valve must remain fully open (sealed or locked). The design and diameter of the stop valve must not interfere with the safe venting function 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 assemblies should be replaced regularly; those that have exceeded the maximum designed rupture pressure without bursting 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 agency shall issue a verification report and apply a lead seal to the verified safety valve. Article 156: During the on-site calibration (in-line inspection) of the safety valves of pressure vessels in use and during pressure adjustment, technical personnel in charge of pressure vessel safety at the using unit, along with inspectors with the appropriate qualifications, must be present to oversee the process. A properly calibrated safety valve should be sealed with a lead seal. The accuracy of the pressure gauges used for tuning and calibration devices should be no less than grade 1. Reliable safety protection measures should be in place during checksum verification and adjustment. Article 157: A safety valve shall be taken out of service and replaced if it is in one of the following conditions: 1. The valve core and seat of the safety valve do not seal properly and cannot be repaired. 2. The valve core and seat of the safety valve are stuck together, or the spring is severely corroded or rusted. 3. Incorrect selection of safety valves Article 158: When the maximum operating pressure of a pressure vessel is lower than that of the pressure source, a pressure reducing valve must be installed on the pipeline leading to the inlet of the pressure vessel. If the pressure reducing valve cannot ensure reliable operation due to medium conditions, a control valve can be used as a substitute. A safety valve and a pressure gauge must be installed on the low-pressure side of the pressure reducing valve or control valve. Article 159: Blasting disc devices shall meet the requirements of GB567 \"Blasting Discs and Blasting Disc Devices\". Article 160: The requirements for selecting pressure gauges are as follows: 1. The pressure gauge selected must be suitable for the medium inside the pressure vessel. 2. The accuracy of the pressure gauge used in low-pressure vessels should not be lower than grade 2.5 ； The accuracy of pressure gauges used in medium-pressure and high-pressure vessels should not be lower than grade 1.5. 3. The maximum scale value on the pressure gauge dial should be 1.5–3.0 times the highest operating pressure, and the diameter of the dial should not be less than 100 mm. Article 161: The calibration and maintenance of pressure gauges shall comply with the relevant regulations of the **metrology authorities. The pressure gauge should be calibrated before installation; a red line indicating the maximum operating pressure should be marked on the dial, along with the date for the next calibration. After calibration, the pressure gauge should be sealed with a lead seal. Article 162: The installation requirements for pressure gauges are as follows: 1. The installation location should allow operators to easily observe and clean the gauge, and it should be protected from adverse effects such as radiant heat, freezing, or vibration. 2. A tee stopcock or needle valve should be installed between the pressure gauge and the pressure vessel ； The through-stopcock or needle valve should be equipped with an opening mark and a locking device ； No accessories or fittings for other purposes shall be connected between the pressure gauge and the pressure vessel. 3. For pressure gauges used in steam media, a trap should be installed between the pressure gauge and the pressure vessel. 4. For pressure gauges used with corrosive or highly viscous media, a buffer device that can isolate the medium should be installed between the pressure gauge and the pressure vessel. Article 163: A pressure gauge shall be discontinued from use and replaced if it is in one of the following conditions: 1. For a pressure gauge equipped with a limit pin, the pointer cannot return to the limit pin when there is no pressure ； For pressure gauges with an unlimited scale, when there is no pressure, the pointer’s position relative to zero exceeds the allowable error of the gauge. 2. The glass covering the dial is cracked, or the dial markings are blurred. 3. The seal is damaged or has exceeded its verification validity period. 4. Leakage in the gauge spring tube or a loose gauge pointer. 5. The pointer is broken or the casing is severely corroded. 6. Other defects that affect the accurate indication of the pressure gauge. Article 164: Level gauges for pressure vessels shall comply with the provisions of relevant standards and meet the following requirements: 1. They shall be selected appropriately based on the medium contained in the pressure vessel, its maximum operating pressure, and temperature. 2. Before installation and use, level gauges for low- and medium-pressure vessels shall undergo a hydraulic test at a pressure 1.5 times the nominal pressure of the gauge ； The level gauge of high-pressure vessels shall undergo a hydrostatic test at a pressure of 1.25 times the nominal pressure of the level gauge. 3. On pressure vessels containing media at temperatures below 0°C, frost-proof level gauges should be used. 4. For level gauges used outdoors in cold areas, those with a jacketed or insulated design should be selected. 5. Pressure vessels for liquefied gases that are flammable and pose an extremely high level of toxicity must be equipped with protection devices to prevent leaks ； 6. For applications requiring a stable liquid level indication, float-type level gauges should not be used. Article 165: The level gauge shall be installed in a location where it is easy to observe. If the installation location of the level gauge does not facilitate observation, additional auxiliary facilities shall be provided. Large pressure vessels should also be equipped with centralized control facilities and alarm devices. The highest and lowest safe liquid levels on the level gauge should be clearly marked. Article 166: Operators of pressure vessels shall strengthen the maintenance and management of level gauges to ensure they remain in good condition and readable. The user unit should implement a regular maintenance system for the level gauge; the maintenance interval can be determined based on the actual operating conditions, but it must not exceed the inspection intervals for the interior and exterior of the pressure vessel. Article 167: Level gauges shall be discontinued from use and replaced if any of the following conditions apply: 1. The maintenance cycle has been exceeded. 2. The glass plate (tube) is cracked or broken. 3. The valve component is stuck. 4. False liquid level appears. 5. The gauge gives an unclear reading. Article 168: Pressure vessels where it is necessary to control the wall temperature must be equipped with temperature measuring instruments (or thermometers) to monitor the wall temperature and prevent overheating. Thermometers should be calibrated regularly. Article 169: The safety interlock devices for quick-opening pressure vessels must meet the functional requirements specified in Article 49, and they must undergo testing and evaluation before they can be put into widespread use. Chapter 8 Supplementary Provisions Article 170 In the event of an accident involving a pressure vessel, the entity responsible for the accident must report it and handle it in accordance with the Regulations on the Handling of Accidents Involving Boilers, Pressure Vessels, and Pressure Pipelines. Article 171: These regulations shall be interpreted by the Boiler and Pressure Vessel Safety Supervision Bureau of the **Quality and Technical Supervision Bureau. Article 172 These regulations shall come into force as of January 1, 2000. Appendix 1: Pressure grades, types of pressure vessels, degree of toxicity of the media, and classification of flammable media
I. Classified by the design pressure (P) of pressure vessels into four pressure grades: low pressure, medium pressure, high pressure, and ultra-high pressure. The specific classifications are as follows:
1. Low pressure (code L): 0.1 MPa ≤ P < 1.6 MPa
2. Medium pressure (code H): 1.6 MPa ≤ P < 10 MPa
3. High pressure (code H): 10 MPa ≤ P < 100 MPa
4. Ultra-high pressure (code U): P ≥ 100 MPa
II. Classified according to the working principle of pressure vessels in the production process into reaction pressure vessels, heat exchange pressure vessels, separation pressure vessels, and storage pressure vessels. The specific classifications are as follows: 1. Reaction pressure vessel (code R): primarily used for carrying out physical and chemical reactions of the medium. Such as reactors, reaction kettles, decomposition pots, decomposition towers, polymerization kettles, autoclaves, ultra-high pressure reactors, synthesis towers, shift furnaces, cooking kettles, steam balloons, autoclaves for autoclaving, gas generators, etc ； 2. Heat exchange pressure vessel (code E): Mainly used for carrying out heat exchange of media. Such as shell-and-tube waste heat boilers, heat exchangers, coolers, condensers, evaporators, heaters, vulcanization kettles, sterilization kettles, dyeing machines, drying cylinders, sulfonation kettles, steaming and frying kettles, preheating kettles, solvent preheaters, steam boilers, steam stripping machines, electric steam generators, gas generator water jackets, etc ； 3. Separation pressure vessel (code S): Mainly used for achieving fluid pressure balance of the medium as well as gas purification and separation. Such as separators, filters, oil collectors, buffers, washers, absorption towers, copper washing towers, drying towers, stripping towers, steam separators, deaerators, etc ； 4. Storage pressure vessels (code C, with spherical tanks coded as B): These are primarily pressure vessels used to hold raw material gases, liquids, liquefied gases, etc., for production purposes. Such as various types of storage tanks. In a pressure vessel, when it possesses two or more process principles simultaneously, the types should be classified according to the primary function within the process. III. Appendix II: Regions across the country where the monthly average minimum temperature is less than or equal to –20°C and –10°C. I. Based on the contour maps of monthly average minimum temperatures at national meteorological stations from 1971 to 1988, as provided by the **Meteorological Bureau, contour lines for the monthly average minimum temperature were drawn using county-level administrative units as the basis. (1) Areas with temperatures below or equal to –20°C, including: 1. Xinjiang Uyghur Autonomous Region, Tibet Autonomous Region, Qinghai Province, Inner Mongolia Autonomous Region, Heilongjiang Province, Jilin Province ； 2. The counties and directly-administered units under the jurisdiction of the following provinces: Shanxi Province – counties such as Tiantian, Datong, Huairen, Pinglu, Youyu, Yanggao, Zuo Yun in the Yanbei region, as well as Pianguan and Hequ counties in the Xinzhou region ； Counties in Hebei Province’s Zhangjiakou area such as Huai’an, Wanquan, Chongli, Yicheng, Kangbao, and Guyuan, as well as counties in Chengde area such as Fengning, Longhua, Weichang, and Pingquan ； Liaoning Province – Lingyuan, Kalaqin Left Wing, Chaoyang and other counties in Chaoyang City; Beizhen, Yixian, Heishan and other counties in Jinzhou City; Xinmin County in Shenyang City; Fushun, Qingyuan, Xinbin and other counties in Fushun City; Zhangwu and Fuxin Counties in Fuxin City; Tieling and Tieling, Kaiyuan Counties in Tieling City; Tiefa City; Beipiao City. (II) Areas with temperatures below or equal to –10°C, including: 1. The areas with temperatures below or equal to –20°C as specified in paragraph (I) of Annex I ； 2. Hebei Province, Shanxi Province, Ningxia Hui Autonomous Region ； 3. The counties and areas listed in the following provinces: Shaanxi Province – Yulin Region, Yan’an Region; counties such as Hancheng, Pucheng, Tongguan, Baishui, Huayin, Chengcheng, Heyang, Dali in the Weinan Region; Yijun County in Tongchuan City; counties such as Bin County, Changwu, Xunyi in Xianyang City ； Gansu Province – Pingliang Region, Dingxi Region, Qingyang Region, Wuwei Region, Zhangye Region, Jiuquan Region, Linxia Hui Autonomous Prefecture, as well as counties in Gannan Tibetan Autonomous Prefecture such as Lintan, Zhuoni, Diebu, Maqu, Luqu, and Xiahe; Lanzhou City, Jinchang City, Baiyin City, Jiayuguan City ； In Sichuan Province, counties such as Markam, Ruoergai, Hongyuan, Jinchuan, and Rangtang in the Aba Tibetan and Qiang Autonomous Prefecture, as well as counties like Danba, Luhuo, Xinlong, Daofu, Yajiang, Baiyu, Litang, Shiqu, Batang, Degé, Seda, and Daocheng in the Ganzi Tibetan Autonomous Prefecture ； Liaoning Province – Areas designated as areas other than those at –20°C in Appendix 1, Item (i) of this document. II. If there is a microclimate in certain areas, local meteorological data should be taken as the reference. Appendix 3 – Appendix 7 (omitted)