Question bank for the theoretical examination of pressure vessel operators: IV. Essay questions
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IV. Essay Questions: 542. What are the special equipment referred to in the “Regulations on the Safety Supervision of Special Equipment”? 543. What is the definition of safety supervision as stipulated in the “Regulations on the Safety Supervision of Special Equipment”? 544. What requirements are placed on personnel working with pressure vessels under these regulations? 545. What are the common safety accessories used for pressure vessels? 546. What are the key points for the safe operation of pressure vessels? 547. What are the criteria for determining that a pressure vessel is in good condition? 548. According to the “Technical Regulations for the Safety Supervision of Pressure Vessels”, under which abnormal conditions must operators take immediate emergency measures and report to the relevant authorities in accordance with the prescribed procedures? 549. What components make up the main body of a cylindrical pressure vessel? 550. What information should generally be included in the operation records of pressure vessels? 551. What are the three main aspects of routine inspections for pressure vessels? 552. What are the key safety considerations for the maintenance of medium and low-pressure vessels? 553. What are the key safety considerations for the maintenance of high-pressure vessels? 554. What is the procedure for hydraulic testing during pressure resistance tests? 555. What is the procedure for pneumatic testing during pressure resistance tests? 556. How many types of pressure resistance tests exist? To what extents are they applicable? 557. What is hydrogen embrittlement? Is it easy to occur under those conditions? What do those devices generate? 558. What are the causes of brittle fracture in pressure vessels? 559. What are the causes of ductile fracture in pressure vessels? 560. Why is it necessary to pay special attention to safety and take appropriate protective measures at the site where pressure vessels are inspected and maintained? 561. What are the basic requirements for safety valves? 562. When performing internal inspections on pressure vessels that contain flammable, explosive, oxidizing, toxic, or asphyxiating substances, what aspects are included in the sampling and analysis of the internal gas composition? 563. Briefly describe the working principle of spring-loaded safety valves, as well as their advantages and disadvantages. 564. Briefly describe the working principle of lever-type safety valves, as well as their advantages and disadvantages. 565. What are the special requirements for safety valves in tanks and tank trucks? 566. What are the main structural and performance differences between full-open safety valves and slightly-open safety valves? 567. What is the working principle of emergency shut-off valve systems? 568. Describe the working principle of rupture disks, and outline their advantages over safety valves. 569. Identify the causes of errors in the readings shown by pressure gauges. 570. Describe the working principle of a rotating tubular level gauge. 571. Describe the working principle and usage characteristics of pressure thermometers. 572. What is the scope of application of the “Regulations on the Safety Supervision of Gas Cylinders”?573. What are the main accessories of gas cylinders?
574. What requirements must cylinder valves meet as stipulated in the “Regulations on the Safety Supervision of Gas Cylinders”?
575. What rules must be observed when filling liquefied gases, as specified in the “Regulations on the Safety Supervision of Gas Cylinders”?
576. Briefly describe the inspection intervals for various types of gas cylinders. 577. What requirements must be followed when transporting and handling gas cylinders as stipulated in the “Regulations on the Safety Supervision of Gas Cylinders”? 578. What requirements must be observed when storing gas cylinders as stipulated in the “Regulations on the Safety Supervision of Gas Cylinders”? 579. What requirements must be adhered to when using gas cylinders as specified in the “Regulations on the Safety Supervision of Gas Cylinders”? 580. What is the scope of application of the “Regulations on the Safety Supervision of Dissolved Acetylene Gas Cylinders”? 581. What requirements must valve components of acetylene cylinders meet according to the “Regulations on the Safety Supervision of Dissolved Acetylene Gas Cylinders”? 582. Under what circumstances may acetylene cylinders not be filled, as stipulated in the “Regulations on the Safety Supervision of Dissolved Acetylene Gas Cylinders”? 583. For acetylene cylinders found to have certain issues upon inspection, what procedures or tests must be carried out prior to filling them? 584. What requirements must be met during the filling process of acetylene cylinders? 585. After being filled, what requirements must acetylene cylinders meet? 586. What information should be included in the filling record filled out by the acetylene cylinder filling unit? 587. What is the regular inspection cycle for acetylene cylinders? In what situations should inspections be conducted in advance during use? 588. What regulations must be followed when transporting and handling acetylene cylinders? 589. What regulations must be followed when storing acetylene cylinders? 590. What regulations must be followed when using acetylene cylinders? 591. What are the regulations in the \"Safety Inspection Procedures for Dissolved Acetylene Cylinders\" regarding the repair or replacement of attachments? 592. Please briefly describe what process pipelines are available in the filling workshop and the residue disposal workshop IV. Essay Questions: 542. Special equipment refers to boilers, pressure vessels (including gas cylinders), pressure pipelines, elevators, lifting machinery, passenger cableways, and large-scale amusement facilities that are related to life safety and pose a high degree of risk. 543. Safety supervision refers to the sum total of activities—such as decision-making, organization, management, control, and supervision and inspection—carried out by administrative authorities responsible for the safety of special equipment in order to achieve safety objectives. 544. Personnel operating special equipment must strictly follow the operating procedures and relevant safety regulations during their work. Upon discovering any potential safety hazards or other unsafe factors, one must immediately report them to the on-site safety managers and relevant persons in charge of the unit. Those who violate operating procedures and relevant safety regulations, or fail to report potential accident hazards or other unsafe factors to the on-site safety managers and relevant responsible persons of the unit immediately, shall be given criticism and disciplinary action by the entity that operates the special equipment ； Those who violate criminal laws shall be investigated for criminal responsibility in accordance with the provisions of the Criminal Law regarding the crime of gross negligence resulting in serious consequences or other crimes. 545. Safety accessories for pressure vessels generally include safety valves, rupture disc devices, emergency shut-off devices, pressure gauges, level gauges, temperature measuring instruments, and safety interlock devices for quick-opening pressure vessels. 546. Operation at excessive temperature or pressure is strictly prohibited: to avoid misoperations, prevent excessive feeding or the presence of impurities in the feed (which can generate pressure through chemical reactions), and prevent overfilling or accidental heating (in the case of liquefied gases) ； (1) Operators should follow the operating procedures carefully (process and safety procedures). (2) The operation must be carried out smoothly – loading and unloading should be done slowly, the load should remain relatively stable during operation, and temperature changes should also occur gradually ； (3) Do not remove the compression bolts while under pressure ； (4) When operating the heat exchanger, the cold flow should be introduced first followed by the hot flow, and the speeds of both the cold and hot flows when introduced should be low ； (5) Stay at your post and pay attention to changes in process parameters ； (6) Adhere to the routine inspection system during operation. It is required to check the operating conditions from a process perspective (pressure, temperature, liquid level, chemical composition of the medium and its mixing ratio, feed volume, etc.) ； Check the condition of the equipment in terms of its components (look for any leaks or seepages at the various connection points) ； Check for plastic deformation, corrosion, and other defects or suspicious signs on the equipment ； Whether there is vibration or wear on the containers and pipes) ； Check the safety devices to ensure they are in good condition and that their calibration or verification is still valid. Routine inspections should be conducted at regular intervals, at specific locations (key equipment, pipelines, pumps, valves, containers, measuring instruments, and areas where failures have occurred), and along designated routes (the production process or areas prone to accidents) ； (7) Fill in the operation records carefully, requiring that the operating conditions of the containers be recorded thoroughly, promptly, accurately, and truthfully ； (8) Handling of running, steaming, dripping, and leaking ； (9) Emergency shutdown of the container. 547. Operating normally with good performance. Its specific indicators are: ① The various operational performance parameters of the container meet the design requirements and can satisfy the needs of production. ② It operates normally during use, and the operating parameters can be easily controlled smoothly. ③ It has good sealing performance with no leakage. ④ A container with a stirrer, whose stirring mechanism is operating properly, without any abnormal vibrations or noises. ⑤ Containers with jackets perform well in heating or cooling the medium inside them. ⑥ The heat exchanger has no severe scaling. Expansion joints and welds of shell-and-tube heat exchangers ； Between the plates of a plate heat exchanger ； The flange connections of all types of heat exchangers can be sealed properly, with no leaks or seepages. (2) Fully equipped and in good condition. It includes the following requirements: ① The components, safety devices, auxiliary devices, and instruments must be complete, and their quality must meet the design specifications. ② The container body is clean, especially the insulation layer is intact, with no severe rust or mechanical damage. ③ The container has a lining, which is in good condition, with no leaks or bulging. ④ There are no leaks, drips, or seepages at the valves and all types of detachable connections. ⑤ The foundation is solid, the supports show no severe rust, and the external pipes are in good condition. ⑥ All types of technical documents are complete, accurate, and come with full technical archives. ⑦ The container has undergone regular inspections within the specified period, maintains good safety performance, and has a registration certificate for use. ⑧ Inspection, calibration, and replacement of safety accessories. 548. (1) When the operating pressure of a pressure vessel, the temperature of the medium inside it, or the wall temperature exceeds the specified values, and measures taken still fail to bring these conditions under effective control ； (2) Cracks, bulging, deformation, leakage, or other safety-threatening defects occurring in the main pressure-bearing components of the pressure vessel ； (3) Failure of safety accessories ； (4) Damage to the connectors and fasteners, making it difficult to ensure safe operation ； Fires, etc., directly threaten the safe operation of pressure vessels ； (5) Overfilling ； (6) Occurrence of fires or other situations that directly threaten the safe operation of pressure vessels ； (7) The liquid level in the pressure vessel exceeds the specified limit; measures taken still fail to bring it under effective control ； (8) Severe vibration in pressure vessels and pressure pipelines, posing a threat to safe operation ； (9) Other abnormal conditions. 549. It generally consists of components such as end caps, cylinders, flanges, nozzles, and supports. 550. (1) Dispatch orders issued by the production command system ； (2) Temperature, pressure, flow rate, time, quantity of various materials entering and leaving the container, as well as the interval between operation cycles ； (3) Actual operating conditions of the container ； (4) Operations performed during shift work ； (5) Are the operating tools and various records complete and intact? 551. Process parameters ； Condition of the equipment itself ； Status of safety accessories. 552. (1) During a shutdown of a single system or the entire system, the cooling and depressurization of the containers must be carried out strictly in accordance with the operating procedures. It is not allowed to remove bolts or other fasteners from the container while it is under pressure. It is prohibited to tighten bolts and other fasteners on pressurized containers without permission (except as permitted by the process operating procedures) ； (2) Cut off the relevant power supply on the container ； (3) Isolate the maintenance vessel from the production system using a blind flange ； Containers that must be purged with an inert gas require further purging with air after that. Only after sampling to confirm that the oxygen content is within acceptable levels and approval is obtained from the safety department can the container be entered for cleaning or maintenance ； (4) When entering the container, only 12V lanterns are allowed for lighting; for instruments used for inspection and maintenance, if their voltage exceeds the safe level, insulated flexible cables without any connections in between must be used, along with a reliable grounding system ； (5) Safety measures must be taken when maintenance personnel enter the container for cleaning and maintenance. The lifting tools or scaffolding provided for this purpose must be safe and reliable, and attention must be paid to ventilation. There must be supervisors inside and outside the container to maintain communication. Guardians are not allowed to leave their posts without permission, and should be familiar with first aid techniques ； (6) Other matters related to maintenance shall be handled in accordance with the safety technical regulations for the container under maintenance. 553. (1) When a single unit or the entire system is shut down, the cooling and pressure reduction of high-pressure vessels must be carried out strictly in accordance with the operating procedures. It is not allowed to remove bolts or other fasteners from the container while it is under pressure. Do not tighten the bolts and other fasteners on pressure vessels without permission ； (2) Cut off the relevant power supply on the container ； (3) Isolate the maintenance vessel from the production system using a blind flange ； Then, the medium inside the container must be completely removed. For containers containing toxic, flammable, or explosive substances, the container must be filled with an inert gas; after that, it should be filled with air as well. Only after sampling to verify that the oxygen content is within acceptable limits and after obtaining approval from the safety department can the container be entered for cleaning or maintenance ； (4) Special tools must be used during disassembly and lifting. To ensure safety, cranes and lifting equipment must be carefully inspected. During disassembly, care must be taken to protect the sealing surface of the cylinder. The sealed surface that has been removed should be immediately coated with lubricant, and protective measures should be taken to prevent tools and other debris from falling into the container. The walls of the container should not be struck or hammered arbitrarily, to avoid causing mechanical damage ； (5) When entering the container, only 12V lanterns are allowed for lighting; for instruments used for inspection and maintenance, if their voltage exceeds the safe level, insulated flexible cables without any connections in between must be used, along with a reliable grounding system ； (6) Safety measures must be taken when maintenance personnel enter the container for cleaning or repairs. The lifting tools or scaffolding provided for this purpose must be safe and reliable, and attention must be paid to ventilation. There must be supervisors inside and outside the container to maintain communication. Guardians are not allowed to leave their posts without permission, and should be familiar with first aid techniques ； (7) Any other matters related to maintenance shall be handled in accordance with the safety technical regulations for the container under maintenance. 554. The hydraulic testing procedure is as follows: (1) Before the test, all the fastening bolts at the connections of the pressure vessel must be properly installed, and the system must be equipped with two pressure gauges of the same range that have been calibrated correctly ； (2) The test site must be equipped with reliable safety protection devices. The test plan and test date must be reviewed and approved by the unit’s technical supervisor and safety department. (3) Clean up the site: Stop tasks unrelated to the experiment, and evacuate personnel who are not involved in it ； (4) Fill the container with liquid, and purge all gas remaining in the pressure vessel ； (5) Check whether the outer surface of the container is dry and free of liquid traces ； (6) Slowly increase the pressure to the maximum operating pressure; once no leaks are detected (it is not allowed to inspect the pressure vessel at this stage), continue to raise the pressure to the specified test pressure, and maintain that pressure for 10 to 30 minutes depending on the volume ； (7) Reduce to the maximum operating pressure and conduct a pressure hold test. The holding time should be no less than 30 minutes ； (8) Reduce the pressure slowly; attention should be paid to the rate of pressure reduction. In cases with special requirements, the pressure reduction must be carried out strictly in accordance with the pressure testing procedures. 555. The pressure test procedure is as follows: (1) Before the test, all the fastening bolts at the connection points of the pressure vessel must be properly installed, and the system must be equipped with two pressure gauges of the same range that have been calibrated correctly ； (2) The test site must be equipped with reliable safety protection devices. The test plan and test date must be reviewed and approved by the unit’s technical supervisor and safety department. (3) Clean up the site: Stop tasks unrelated to the experiment, and evacuate personnel who are not involved in it ； Personnel from the security department of the using unit shall be present on site ； (4) Drain all liquid remaining in the pressure vessel ； (5) Check whether the valves in the container pressure testing pipeline are properly installed and whether their operation meets the requirements ； (6) First, slowly increase the pressure to 10% of the specified test pressure, hold it at that level for 5–10 minutes, and inspect all welds and joints; if there are no leaks, proceed to the next step ； (7) Raise the pressure to 10% of the specified test pressure; if no abnormalities are detected upon inspection ； Continue to increase the test pressure by 10% at each stage until the specified test pressure is reached. Depending on the volume, maintain this pressure for 10 to 30 minutes ； (8) Reduce to the maximum working pressure and perform a pressure hold check. The holding time should be no less than 30 minutes ； (9) Reduce the pressure slowly; attention should be paid to the rate of pressure reduction. In cases with special requirements, the pressure reduction must be carried out strictly in accordance with the pressure testing procedures. 556. Pressure tests include hydraulic tests and pneumatic tests. In principle, pressure testing should be carried out primarily using hydraulic testing; since clean water is commonly used for this purpose, it is often referred to as hydrostatic testing. If other liquids are used as the medium for hydraulic testing, such media must be non-hazardous and their temperature must be below the boiling point. When using a flammable liquid for a sub-hydrostatic test, the test temperature must be below the flash point of the flammable liquid. At the same time, there must be no sources of ignition near the test site, and appropriate fire-fighting equipment should be provided. The pneumatic test may be conducted as specified in the design drawings when it is not possible to completely fill the pressure vessel with liquid due to structural or support-related reasons, and for pressure vessels where operating conditions do not permit any residual test liquid. For example, in situations where the volume of the container is too large to bear the weight of water; cases where it’s difficult to use large spherical tanks, concrete foundations, supports, etc ； Those with complex structures for which hydrostatic testing is insufficient to fully verify the pressure testing requirements of certain components ； Since only gaseous-phase loads are considered in the structural design, if a hydrostatic test is conducted, those loads may damage the structure ； Or in situations where the medium used for hydrotesting may cause corrosion and damage to the container’s shell walls and lining. 557. Hydrogen embrittlement is a phenomenon in which steel is exposed to high temperature and high pressure hydrogen, causing chemical changes in its metal structure; as a result, the strength and ductility of the steel decrease, and the fracture pattern becomes brittle. The cause is that under high temperature and pressure, hydrogen enters the interior of the steel and reacts with cementite to form methane, thereby significantly reducing the decarburization resistance of the steel. The generated methane cannot dissolve in the ferrite and escapes as a gas; it accumulates at the grain boundaries of the steel, creating high internal pressures that cause the steel to crack along those boundaries. Hydrogen does not cause significant corrosion of steel at normal temperature and pressure, but when the temperature exceeds 300°C and the pressure is above 30 MPa, a corrosion defect known as hydrogen embrittlement occurs, especially under high-temperature conditions. Such as the desulfurization tower, shift tower, and ammonia synthesis tower in the ammonia synthesis production process ； Some hydrogenation reaction units in the refining process ； Methanol synthesis towers in the petrochemical production process, etc. 558. Analysis of many brittle fracture accidents involving pressure vessels at home and abroad shows that there are three main factors contributing to brittle fracture: (1) certain stress-strain conditions ； (2) There are defects in the container ； (3) The material has poor toughness. Therefore, low temperature is an external factor that causes brittle fracture. Furthermore, the medium also affects the properties of the material. Overall, it can be concluded that defects in the structure and the poor toughness of the material are the internal factors causing brittle failure, whereas pressure (which thus creates a certain stress-strain state in the container), temperature, and the medium are the external factors that contribute to brittle failure. From the perspective of fracture mechanics, when a container has defects, under certain applied stresses (pressures), the stress and strain near the defect (at its tip) increase. Depending on the geometry of the structure and the defect, this increase is expressed using a stress intensity factor. When the combination of strain conditions and defect geometry results in the stress intensity factor reaching or exceeding the material’s fracture toughness, the defect (crack) undergoes rapid unstable growth, leading to brittle fracture of the structure. 559. Ductile fracture of pressure vessels is accompanied by significant plastic deformation of the vessel. This deformation can occur only when the material across the entire cross-section under stress is in a state of yield. Therefore, the ductile fracture of pressure vessels occurs because the thin film stress on the shell wall exceeds the yield strength of the material. Based on the design principles and manufacturing requirements for pressure vessels, as long as they are used properly and managed rigorously, ductile fracture of pressure vessels can be completely avoided. However, ductile fractures in pressure vessels also occur from time to time. Such failure incidents usually arise under the following circumstances: (1) Overfilling of pressure vessels containing liquefied gases. During storage, transportation, or use, if the temperature of a pressurized container rises (such as when a filled liquefied petroleum gas cylinder is exposed to the sun), the saturated vapor pressure of the liquefied gas increases. In particular, the volume of the liquid expands, resulting in a sharp rise in pressure inside the container, which may lead to overpressure explosion. It is calculated that when the temperature of a cylinder filled with liquefied petroleum gas rises by 3–5°C, the pressure generated by the expansion of the liquefied gas can cause the cylinder to overpressurize and explode. (2) The pressure vessel experiences overpressure during use. Rupture occurs because the pressure exceeds the allowable pressure of the container due to violations of operating procedures, operational errors, or malfunctions of indicating instruments and safety accessories. (3) Pressured vessels are poorly managed, with no inspections or maintenance carried out over time; corrosion and other factors cause the wall thickness to decrease significantly. As a result, under normal operating pressure, such vessels undergo plastic deformation due to insufficient wall thickness, and may even rupture. 560. (1) On-site maintenance of pressure vessels, especially large ones, often involves working at heights. Workers need to concentrate on operating the relevant maintenance equipment and instruments; if the scaffolding is not properly set up or safety measures are inadequate, it is easy for accidents resulting from falls to occur. (2) When staff enter the interior of the container for inspection, the high humidity and temperature inside the pressure vessel, combined with the demanding nature of the tasks, result in high oxygen consumption. The human body becomes more sensitive to hypoxia when oxygen consumption increases. Therefore, in pressure vessels, even the slightest carelessness can lead to suffocation. (3) The media in pressure vessels used in petrochemical production generally possess characteristics such as flammability, explosiveness, toxicity, and strong corrosivity. During maintenance, residues such as acid, dust, and smoke toxins are inevitably present inside the container. When the temperature inside the container rises, it promotes the volatilization of these residues. High humidity and temperature, along with high levels of physical strain, increase the amount of toxins absorbed by the body. They also enhance the harmful effects of certain toxins (for example, hydrogen chloride and hydrogen fluoride cause more severe irritation to the body at high temperatures), thereby increasing the risk of poisoning among workers. In some pressure vessels that store flammable and explosive materials, if the purging process is not thorough, the materials remaining in certain dead corners may cause accidental explosions. (4) High humidity inside pressure vessels, combined with excessive sweating from the human body, **increases the risk of electric shock accidents for people. According to relevant calculations, the commonly used safe voltage is 36V ； Inside the container, due to the moist and sweaty human skin, the safe voltage is 12V. In short, there are many safety hazards associated with the maintenance of pressure vessels, especially when working inside them. Additionally, the work area is often cramped, ventilation is poor, lighting is inadequate, and it is difficult for people to enter and exit as well as to communicate with one another. Even a slight carelessness during such work can lead to accidents such as falls, poisoning, suffocation, electric shocks, and explosions; therefore, special attention must be paid to safety measures. 561.. Safety valves shall meet the following basic requirements: (1) They must have good sealing properties, being able to remain airtight under normal operating pressure; furthermore, they should be capable of closing again after the discharge pressure drops, while still maintaining their sealing integrity ； (2) The operation is sensitive and reliable; when the pressure reaches the opening pressure, the valve disc can quickly lift automatically to facilitate the smooth discharge of the medium ； (3) Under discharge pressure, the valve disc should reach the fully open position, allowing the valve to achieve a safe discharge volume ； (4) Compact and reasonable structure, easy to adjust. 562. It mainly includes: (1) Analysis of flammable gas content. Flammable gases refer to gases that, when mixed with air, have an explosion limit of less than 10%, or a difference in explosion limits of 20% or more. (2) Oxygen content analysis. The oxygen content inside the equipment is 18~23%. An oxygen content of less than 18% constitutes a hypoxic environment, which is not conducive to meeting the oxygen needs of the personnel inside the container ； An oxygen content exceeding 23% indicates an oxygen-rich environment, which has strong combustion-supporting properties and is unfavorable for explosion prevention. (3) Analysis of toxic gas content. It is mainly based on GB5044 \"Classification of the Hazard Levels of Occupational Exposure to Toxic Substances\". 563. A spring-type safety valve utilizes the elastic force of a compressed spring to balance the internal forces acting on the valve disc, and the opening pressure of the safety valve is adjusted by regulating the degree of compression of the spring. This safety valve features a compact structure, high sensitivity, few restrictions on its installation location, low sensitivity to vibrations, and relatively simple adjustment procedures. However, since the elasticity of springs gradually decreases due to prolonged exposure to high temperatures, ordinary spring-loaded safety valves are not suitable for use in environments with excessively high temperatures. 564. The lever-type safety valve operates based on the principle of leverage; through a lever and a valve stem, the gravitational moment of a weight is applied to the valve disc to balance the internal forces acting on it. The set pressure of this valve is adjusted by moving the position of the weight (or changing its mass). This type of safety valve features a simple structure, easy adjustment, and reliable operation. The load applied does not increase as the valve disc rises, nor is it limited by the operating temperature. However, due to its relatively bulky structure, the size of the heavy hammer is disproportionate to that of the valve body; it is also quite sensitive to vibrations. During installation, it is essential to ensure that the axis of the valve disc is perpendicular to the horizontal plane. Additionally, its reseating force is generally quite low; sometimes it must drop below 70% of the opening pressure in order for the valve to reseat. 565. Tankers have the following specific requirements regarding safety valves: (1) To prevent the safety valves from being damaged due to collisions while the tanker is in motion, it is required that the height of the valve body above the top of the tank does not exceed 150 mm. Therefore, an internal safety valve must be used and protected. (2) The safety valves of tank trucks must be designed to be fully open type. (3) The safety valve spring shall be corrosion-resistant. 566. The disc of a fully open safety valve is larger in diameter than the seat, and it is equipped with a rebound disk; the seat itself has an adjusting ring. When the medium flow rushes out of the seat, it flows in the opposite direction to that of the disc’s upward movement thanks to the rebound disk, thereby exerting a counterforce on the disc and causing it to rise further. The degree of flow deflection can be adjusted using the control ring. Therefore, fully open safety valves perform well; they feature a rapid opening action, large discharge capacity, and an opening height of no less than 1/4 of the seat throat diameter. When the lift height is 1/4 of the throat diameter, the cross-sectional area of the valve seat throat is equal to the annular discharge area of the valve disc; therefore, the discharge capacity of a fully open safety valve is related to the throat diameter of the valve seat. Due to its different structure from fully open safety valves, the opening height of micro-open safety valves is generally less than 1/20 of the valve seat diameter. Its emission capacity is also related to the opening height. 567. An emergency shut-off valve device is a valve with a special structure and purpose; it is usually installed in series with a globe valve on the medium outlet pipeline adjacent to the pressure vessel, and is equipped with independent local and remote operating systems to open and close the shut-off valve, thereby enabling remote emergency leakage stoppage in the event of a large-scale leak in the pipeline. The emergency cut-off device also has the functions of overcurrent shutdown and overtemperature shutdown. For some reason, if the flow rate in the pipeline becomes too high and exceeds the valve’s rated flow capacity (overflow condition), or if a fire occurs or the temperature rises sharply causing the fusible plug on the shut-off valve to melt, this will enable the main valve disc to return to its closed position, thus maintaining the seal. 568. Shrapnel, also known as explosion-proof plates or membranes, is a type of failure-based safety relief device that reduces the pressure inside a pressure vessel by causing a bursting element (membrane) to break under specified pressure, thereby releasing the medium. Compared with safety valves, it has advantages such as simple structure, good sealing performance, fast pressure relief response, and strong adaptability. 569. The deviation between the reading of a pressure gauge and the actual pressure value of the medium being measured is called the indication error of the pressure gauge, and it is divided into basic error and additional error. The error produced by a pressure gauge under normal operating conditions is called the basic error. It is caused by structural and manufacturing defects in the pressure gauge. Additional errors are those that occur in pressure gauges under abnormal operating conditions. They include reading errors caused by the line of sight not being perpendicular to the dial markings during reading, temperature errors resulting from a large difference between the ambient temperature and the operating temperature required by the pressure gauge, and errors caused by the pressure of the liquid column resulting from the condensation of the medium. As working conditions change, the magnitude of the additional error varies greatly. 570. Rotary tubular level gauges can only measure the liquid level of liquefied gas media such as liquefied petroleum gas; they work by using a rotating handle to cause a curved connecting tube inside the pressure vessel to rotate, thereby moving the tube opening up and down. When filling a pressure vessel with a medium, first align the pointer connected to the pipe outside the vessel with the level indicated on the gauge for the desired liquid level, and then open the valve on that external pipe. Once white mist is observed coming out of the end of the pipe, filling should be stopped immediately. When it is necessary to measure the liquid level, slowly turn the connecting tube from the highest position indicated by the pointer towards lower levels. When a white mist emerges from the opening of the connecting tube, it means that the opening is aligned with the liquid surface; at this point, the position indicated by the pointer represents the height of the liquid surface. 571. A pressure-type thermometer consists of a bulb, a capillary tube, and a display instrument. It works by utilizing the change in pressure of the gas or liquid inside the bulb due to heating; this pressure change drives the mechanism in the display instrument through the capillary tube, with the pointer indicating the measured value. The measurement range is generally from -80°C to 400°C, and it can measure the temperature of liquids and gases ； The length of the capillaries ranges from 3 to 20 meters, allowing for on-site centralized measurement ； But its precision is low, with a precision grade of 2.5 ； Capillaries have poor mechanical strength and are difficult to repair once damaged; therefore, mechanical damage should be avoided during installation ； Care should also be taken not to lay the capillaries along the pipes of the hot and cold media or along the walls of the equipment, to avoid affecting accuracy. 572. These regulations apply to seamless, welded, and special-type gas cylinders used under normal ambient temperatures (–40~60°C), with a nominal working pressure of 1.0~30 Mpa (gauge pressure, the same below) and a nominal volume of 0.4~3000 L, and which are used to hold inert gases, liquefied gases, or mixed gases. “Special-type gas cylinders” refer to vehicle-mounted gas cylinders, cryogenically insulated gas cylinders, fiber-wound gas cylinders, and non-refillable gas cylinders; among these, the minimum nominal working pressure for cryogenically insulated gas cylinders is 0.2 MPa. These regulations do not apply to cylinders containing dissolved gases or adsorbed gases, nor to bottle-type pressure vessels attached to machinery and equipment. 573. Cylinder accessories include special rupture disks for cylinders, safety valves, fusible alloy plugs, cylinder valves, cylinder caps, level gauges, shock-absorbing rings, emergency shut-off and filling limit devices, etc. 574. Bottle valves shall meet the following requirements: (1) The material of the bottle valve shall comply with the provisions of relevant standards; the material used shall neither react chemically with the gas contained in the bottle nor affect the quality of the gas. (2) The thread on the cylinder valve that connects to the gas cylinder must match the internal thread of the cylinder mouth and comply with the requirements of relevant standards. The design of the gas outlet on the bottle valve should effectively prevent incorrect installation or misuse of the gas. (3) The sealing material for the cylinder valves of oxygen and highly oxidizing gas cylinders must be an oil-free, flame-retardant material. (4) The material of the handwheel for liquefied petroleum gas cylinder valves should have flame-retardant properties. (5) If a rupture disc is installed on the body of the cylinder valve, its nominal burst pressure shall be equal to the hydrostatic test pressure of the gas cylinder. (6) For bottle valves of the same specification and model, the weight tolerance shall not exceed 5%. (7) The valve for non-refillable bottles must be assembled to the non-refillable gas cylinders in a non-removable manner. (8) When bottle valves leave the factory, a certificate of conformity should be issued for each one. 575. The following regulations must be observed when filling liquefied gases: (1) A system of rechecking the quality of each bottle after filling must be implemented, and overfilling is strictly prohibited. Cylinders with excessive filling are not allowed to leave the factory. When filling is carried out using continuous automatic weighing, random sampling shall be used in place of retesting each bottle; a corresponding sampling system must be in place and approved by the filling registration authority ； (2) The weighing scale must remain accurate, with its maximum weighing capacity being 1.5–3.0 times the value used for regular measurements. Weighing instruments shall be calibrated regularly in accordance with relevant regulations, and the instruments should be checked once per shift. Weighing instruments must be equipped with an overloading alarm or a device to automatically cut off the gas supply ； (3) Filling gas cylinders directly from LPG storage tanks or tank trucks is strictly prohibited; direct transfer of gas from one cylinder to another is also not allowed ； (4) After filling, each gas cylinder should be inspected individually; if any leakage or other abnormalities are detected, they must be dealt with properly ； (5) The inspection records prior to filling, the filling operation records, and the re-inspection and check records after filling must be complete. The information included should at least cover: the cylinder number, the cylinder capacity, the actual amount filled, any abnormalities detected, the names or codes of the inspector, the person who performed the filling, and the person who conducted the re-weighing, as well as the filling date. The records should be properly kept for future reference ； (6) The operators should be relatively stable; they must obtain certificates after being assessed by the enterprise and receive regular safety training. 576. The inspection cycle for various types of gas cylinders shall not exceed the following provisions: (1) Gas cylinders containing corrosive gases, diving cylinders, and those that are frequently in contact with seawater shall be inspected every two years. (2) Cylinders containing general gases shall be inspected every three years. (3) Cylinders filled with inert gas shall be inspected every five years. (4) Liquefied petroleum gas cylinders, in accordance with the provisions of **Standard GB 8334. (5) Cryogenic insulated gas cylinders shall be inspected every three years. (6) LPG cylinders for vehicles must be inspected every five years, while CNG cylinders for vehicles must be inspected every three years. When a car is scrapped, its gas cylinders are also scrapped. During the use of gas cylinders, if severe corrosion or damage is detected, or if there are doubts regarding their safety and reliability, inspections should be carried out in advance. Cylinders whose inventory or downtime exceeds one inspection cycle should be inspected before being put back into use. After a traffic accident, the vehicle’s gas cylinders, cylinder valves, and other accessories should be inspected; they can be reused only after passing the inspection. 577. When transporting and handling gas cylinders, the following requirements must be complied with: (1) The vehicle shall have visible safety markings ； (2) The cylinder caps must be properly fitted (except for cylinders with protective covers), and shock-absorbing rings must be used (except for packaged gas cylinders). Handling should be gentle; throwing, sliding, rolling, or knocking is strictly prohibited ； (3) During lifting, the use of electromagnetic cranes and metal chains is strictly prohibited ； (4) Gas cylinders in which the gases inside come into contact with each other, potentially causing combustion, explosion, or the generation of toxic substances, shall not be transported in the same vehicle (compartment) ； Flammable, highly flammable, corrosive substances, or items that react chemically with the gas inside the cylinder must not be transported together with the gas cylinder ； (5) When transported by vehicle, the gas cylinders must be properly secured. When placed upright, the height of the cargo compartment should be at least 2/3 of the bottle height. When laid horizontally, the valve ends of the bottles should face the same direction. The stack height must not exceed five layers, nor should it exceed the height of the cargo compartment ； (6) Shade facilities should be provided for summer transportation to avoid exposure to direct sunlight ； Transportation during the day should be avoided in busy areas of the city ； (7) When transporting cylinders of flammable gases, open flames and smoking are strictly prohibited. Fire extinguishing equipment should be available on the vehicle ； (8) Vehicles and ships used to transport gas cylinders shall not stop near busy urban areas, schools, theaters, large stores, and other places with dense crowds ； When the vehicle or ship is docked, the driver and escort personnel must not leave at the same time ； (9) Cylinders containing liquefied petroleum gas must not be transported over distances of more than 50 kilometers ； (10) The transportation of gas cylinders filled with gas must strictly comply with the regulations regarding the transport of hazardous materials ； (11) Transportation enterprises should formulate emergency response measures for accidents; drivers and escorts should be able to handle them properly. 578. When storing gas cylinders, the following requirements must be followed: (1) They should be stored in a dedicated warehouse, and such a warehouse must comply with the relevant provisions of the Code for Fire Protection Design of Buildings ； (2) There shall be no sewers or hidden passages in the warehouse; open flames and other heat sources are strictly prohibited. The warehouse should be well-ventilated and dry, with direct sunlight avoided ； (3) Cylinders containing gases that are prone to polymerization or decomposition reactions must have the maximum temperature in the storage area controlled according to the properties of those gases, a specified storage period must be set, and they should be kept away from radiation sources ； (4) Empty bottles and full bottles should be stored separately, with clear markings. Bottles containing toxic gases, as well as those whose contents can cause combustion, explosion, or the release of toxic substances when in contact with each other, should be stored in separate rooms, with gas protection equipment or fire extinguishing devices placed nearby ； (5) Gas cylinders should be placed neatly, with their caps properly on. When standing upright, it must be properly secured ； When placed horizontally, the heads face the same direction. 579. The following rules shall be observed when using gas cylinders: (1) Purchase and use qualified products from enterprises with manufacturing licenses; do not use gas cylinders that have passed their inspection deadline ； (2) Users must purchase gas from units that have completed filling registration or distribution registration ； (3) Before use, gas cylinders must undergo a safety inspection to verify the contents; cylinders that do not meet safety and technical requirements are strictly prohibited from being stored or used ； When using, the gas cylinder must be used strictly in accordance with the instructions in the user manual ； (4) The location where gas cylinders are placed must be away from heat sources and open flames; the cylinder bodies must be kept dry. Cylinders containing gases that are prone to polymerization or decomposition reactions should be kept away from radioactive sources ； (5) When the gas cylinder is placed upright, measures should be taken to prevent it from tipping over ； (6) Protection from exposure to sunlight should be ensured in summer ； (7) Knocking and colliding are strictly prohibited ； (8) It is strictly prohibited to strike an electric welding arc on gas cylinders ； (9) It is strictly prohibited to heat gas cylinders using a heat source with a temperature exceeding 40°C ； (10) The gas in the cylinder must not be exhausted; there must be a remaining pressure or weight. The remaining pressure in permanent gas cylinders should be no less than 0.05 Mpa ； For liquefied gas cylinders, there should be a residual gas volume of no less than 0.5%–1.0% of the specified filling amount ； (11) In applications where backflow may occur, the equipment must be equipped with devices to prevent backflow, such as check valves, non-return valves, and buffer tanks ； (12) LPG cylinder users and distributors are strictly prohibited from transferring the gas in one cylinder to another, and are also prohibited from handling the remaining liquid in the cylinders on their own ； (13) After the gas cylinder is put into use, the cylinder body shall not be repaired by patching or welding ； (14) It is strictly prohibited to alter the steel stamp and color markings of gas cylinders without permission. 580. These regulations apply to portable acetylene cylinders with steel bodies, containing porous filler and solvent, that can be refilled with acetylene gas. These regulations do not apply to fixed pressure vessels containing acetylene gas. 581. Bottle valves shall meet the following requirements: (1) The threads connecting the bottle valve to the cylinder valve seat must match the internal threads of the cylinder valve seat and comply with the provisions of the relevant **standards ； (2) For bottle valves of the same specification and model produced by the same manufacturer, the weight tolerance shall not exceed 5% ； (3) Upon leaving the factory, each cylinder valve shall be accompanied by a certificate of conformity, which shall indicate the tightening torque. 582. Acetylene cylinders shall not be refilled if they fall under any of the following circumstances: (1) Acetylene cylinders manufactured by units without a manufacturing license ； (2) Imported acetylene cylinders that do not comply with the provisions of Article 5 of these regulations ； (3) Acetylene cylinders whose records are not kept at the current filling unit (except those with a temporary change in filling unit). 583. Before filling an acetylene cylinder, the filling facility shall assign dedicated personnel to inspect the cylinder; the results of the inspection shall be recorded in the filling report and signed by the inspector. In any of the following situations, treatment or inspection must be carried out first; otherwise, filling is strictly prohibited: (1) The steel stamp markings are incomplete or unreadable ； (2) Beyond the inspection deadline ； (3) The color marking does not conform to the requirements of GB7144, or the surface paint is severely worn off ； (4) Incomplete, damaged, or non-compliant attachments ； (5) No residual pressure in the bottle or suspicion of contamination with other gases ； (6) The weight of the solvent in the bottle does not meet the requirements specified in GB13591 \"Regulations for Filling with Dissolved Acetylene\" ； (7) Visible damage was found upon visual inspection, requiring further inspection ； (8) After the first filling or after the bottle valve and fusible alloy plug have been removed and replaced, without undergoing proper purging. 584. Filling operations for acetylene cylinders: (1) The volumetric flow rate during filling should be properly controlled, generally not less than 0.015 m3/h·L ； (2) The wall temperature of the bottle must not exceed 40°C. During filling, it can be cooled by spraying with tap water or through forced cooling ； (3) Generally, it is filled in two stages, with an interval of no less than 8 hours between them. 585. After filling, acetylene cylinders shall meet the following requirements: (1) The amount of acetylene filled and the pressure inside the cylinder after 8 hours of standing shall comply with the provisions of the relevant **standards ； (2) There shall be no leaks or other abnormal phenomena. Acetylene cylinders that do not meet the above requirements must not be released from the factory and should be disposed of properly. 586 The acetylene cylinder filling units shall carefully fill out filling records for each cylinder; such records should include: the inspection results prior to filling, the filling date, the room temperature in the filling area, the cylinder number, the tare weight, the actual weight, the remaining pressure, the amount of acetylene remaining, the amount of solvent added, the amount of acetylene filled, the pressure after standing still, any problems that occurred and the measures taken to address them, as well as the operator’s signature. The acetylene cylinder filling records must be retained for at least 12 months. 587. The regular inspection of acetylene cylinders is carried out every three years. Acetylene cylinders that have been in stock or out of use for more than three years should be inspected before being put back into use. During the use of acetylene cylinders, if any of the following conditions are observed, an inspection should be carried out in advance: (1) Severe corrosion, damage, or deformation of the cylinder body or its attachments ； (2) Doubts about the quality of the filler and solvent inside the bottle ； (3) Abnormal dead weight of acetylene cylinder ； (4) There are signs of tempering, burning, or blackening of the surface paint ； (5) Abnormal bottle wall temperature during filling ； (6) When the inspectors deem it necessary to conduct an inspection in advance. 588. When transporting and handling acetylene cylinders, the following rules must be followed: (1) Transport vehicles and ships must have obvious signs indicating the transport of hazardous materials ； Unrelated persons are strictly prohibited from boarding ； When it is necessary to pass through the urban area, one must travel along the routes and at the times specified by the local public security authorities ； (2) Transport vehicles and ships are strictly prohibited from stopping in densely populated areas, important government offices, and locations where open flames are present ； During stopovers, the driver and the escort shall not leave simultaneously ； (3) Acetylene cylinders containing acetylene gas should not be transported over long distances ； (4) Handle with care; throwing, sliding, rolling, bumping, or turning upside down is strictly prohibited ； (5) Special clamps should be used for lifting acetylene cylinders; the use of electromagnetic cranes or chains to tie them is strictly prohibited ； (6) The bottle cap should be worn properly. When standing upright, it must be properly secured, and the height of the compartment shall not be less than two-thirds of the bottle’s height ； When placed horizontally, the heads of the acetylene cylinders should be aligned, and the stacking height must not exceed the height of the container ； (7) Open flames and smoking are strictly prohibited at the loading and unloading site, and fire extinguishers must be available. 589. The following regulations shall be observed when storing acetylene cylinders: (1) At the site where acetylene cylinders are used, the storage volume of acetylene gas shall not exceed 30 m3 (equivalent to 5 cylinders, referring to acetylene cylinders with a nominal capacity of 40 L, the same below) ； (2) When the storage volume of acetylene gas exceeds 30 m3, a separate storage area should be created using non-combustible or difficult-to-ignite materials, with one side of this area being a solid wall ； When the storage volume of acetylene gas exceeds 240 m3 (equivalent to 40 cylinders), a cylinder storage warehouse with a fire resistance rating of not less than grade II should be constructed, and the fire separation distance from other buildings should be no less than 10 m; otherwise, it should be separated by a fire wall ； (3) The storage warehouse or room for acetylene cylinders should be kept away from direct sunlight and radioactive sources; it must also be at a distance of at least 15 meters from open flames or areas where sparks may be generated ； (4) The storage warehouse or room for acetylene cylinders must be equipped with proper ventilation and cooling facilities; there should be no sewers, hidden passages, or vents at the bottom, and it is strictly prohibited for any pipelines to pass through it ； (5) The storage warehouse or room for acetylene cylinders must be under the supervision of a designated person, and signs stating “Acetylene – Hazardous” and “No Smoking” should be installed ； (6) Empty bottles and full bottles should be placed separately and neatly, with clear markings ； (7) Storage in the same room as oxygen cylinders, chlorine cylinders, and flammable materials is strictly prohibited ； (8) When storing acetylene cylinders, they should be kept in an upright position, and measures should be taken to prevent them from tipping over ； (9) Acetylene cylinders must not be stored in basements or semi-basements. 590. When using acetylene cylinders, the following rules must be followed: (1) Before use, check the steel stamp markings, color codes, and safety condition; acetylene cylinders that do not meet these requirements shall not be used ； (2) The storage location of acetylene cylinders must not be near heat sources or electrical equipment, and the distance from open flames must be at least 10 m (for work at heights, this distance is the vertical projection distance from the ground) ； (3) When using an acetylene cylinder, it must be held upright, and measures should be taken to prevent it from tipping over; it is strictly prohibited to use it in a horizontal position ； (4) Acetylene cylinders must never be used in areas with poor ventilation or in the presence of radioactive sources ； (5) Acetylene cylinders must not be struck or collided with; arcing on the cylinder body is strictly prohibited, and acetylene cylinders must not be used on electric insulators ； (6) Measures should be taken to prevent acetylene cylinders from being exposed to direct sunlight or heat; it is strictly prohibited to heat acetylene cylinders with hot water at temperatures above 40°C or any other heat source ； (7) When moving around, a dedicated trolley should be used for transportation. If acetylene cylinders and oxygen cylinders need to be placed on the same trolley, they must be separated by a non-combustible partition ； (8) A dedicated pressure reducer and flashback arrester must be installed at the outlet of the cylinder valve. Under normal use, the discharge pressure indicated by the pressure reducer shall not exceed 0.15 MPa, and the discharge flow rate shall not exceed 0.05 m3/h·L. When a higher flow rate is required, multiple acetylene cylinders should be used in parallel to supply gas ； (9) During the use of the acetylene cylinder, the special wrench for opening and closing the cylinder valve should always be attached to the valve. When temporarily stopping use, it is necessary to close the valves of the welding and cutting tools as well as the valve on the acetylene cylinder; it is strictly prohibited to adjust the pressure regulator or open/close the valve on the acetylene cylinder while holding a lit welding or cutting tool ； (10) If a leak is detected during the use of an acetylene cylinder, it must be addressed promptly; using it in the presence of a leak is strictly prohibited ； (11) The gas in the acetylene cylinder must not be used up completely; a residual pressure of not less than 0.05 MPa must remain. 591. Units and individuals using acetylene cylinders shall not repair or replace accessories such as cylinder valves and fusible alloy plugs on their own, and welding repairs to the cylinder bodies and bases of acetylene cylinders in use are strictly prohibited. Only units with the appropriate inspection qualifications can carry out maintenance or replacement as required. 592. The filling workshop contains liquefied petroleum gas liquid-phase pipelines and compressed air pipelines. The residue handling workshop contains liquefied petroleum gas vapor pipelines and residue liquid pipelines. The filling room is also equipped with water pipelines.