Cylinder storage capacity: How many cylinders can be stored on site at most?

Thread Content

Question: Our company uses about 15 cylinders of acetylene and oxygen per day at the site. **The expert we hired said that our practices are illegal. What are the required storage amounts for acetylene and oxygen cylinders at the site? Answer: After checking the relevant regulations regarding gas cylinders, we found that the standards in use now vary to some extent. We have listed them all here for your reference. I. According to Article 45 of the **Regulations on the Safety Supervision of Gas Cylinders** issued by the Quality and Technical Supervision Bureau (revised in 2015): Entities that store filled gas cylinders must have dedicated warehouses for holding such cylinders. These warehouses must comply with the requirements of the Code for Fire Protection Design of Buildings, and the number of cylinders stored there must meet relevant safety regulations. II. Chapter 3 of the Code for Fire Protection Design of Buildings stipulates: 1. At sites where acetylene cylinders are used, the storage volume of acetylene shall not exceed 30 m³ (equivalent to 5 cylinders, referring to acetylene cylinders with a nominal capacity of 40 L). When the storage volume of acetylene exceeds 30 m³, a separate storage area shall be created using non-combustible materials, with one side of this area being a solid wall. 2. When the storage volume of acetylene gas exceeds 240 m³ (equivalent to 40 cylinders), a 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. III. In accordance with AQT7009 \"Standards for Safety Production Standardization in Machinery Manufacturing Enterprises\" 4.2.27.4.3, the maximum number of gas cylinders that can be stored in one location at the work site is 20 ； If there are more than 20 cylinders, a secondary cylinder storage facility should be established. IV. In accordance with CNPC Natural Gas Group Standard QSY1365-2011 \"Safety Management Specifications for the Use of Gas Cylinders\", section 4.4.6: 1. At the site where acetylene cylinders are used, the storage volume of acetylene shall not exceed 30 M³ (equivalent to 5 acetylene cylinders with a nominal capacity of 40 L each) ； 2. When the storage volume of acetylene gas exceeds 30 m³, a separate storage room should be partitioned off using non-combustible materials; one side of this room must be a fixed wall ； 3. When the storage volume of acetylene gas exceeds 240 M³ (equivalent to 40 cylinders), a 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 meters; otherwise, it should be separated by a fire wall. V. Since the \"Safety Supervision Regulations for Dissolved Acetylene Cylinders\" have been repealed, and in line with the principle of strict management, HSE authorities currently recommend that if your company does not have a cylinder storage facility, the amount of acetylene stored on-site should not exceed 5 cylinders. People always ask why gas cylinders need to be kept upright Anti-tipping? Leave residual pressure? ......Let’s give a unified answer now! Why must acetylene cylinders be stored and used upright, rather than lying down? There are four reasons for this: Reason 1: Acetylene cylinders contain fillers and solvents (propane). When used in a horizontal position, propane tends to flow out along with the acetylene gas, which not only increases the consumption of propane but also lowers the combustion temperature, affecting performance. Additionally, backfire can occur, leading to explosions of the acetylene cylinder. Acetylene in the cylinder is dissolved in a propane solvent under pressure. When the valve is opened, the pressure decreases, and the dissolved acetylene turns into a gas and is released. Laying an acetylene cylinder on its side may cause acetone to leak out; the acetylene dissolved in acetone will rapidly vaporize and mix with air to form an explosive mixture. The explosion limit is 2.3%-72.3% (vol), and the minimum ignition energy is 0.019 mJ. It can catch fire and explode when exposed to open flames or heat. It not only increases the consumption of propane but also lowers the combustion temperature, affecting its use; meanwhile, it can cause tempering and lead to explosions of acetylene cylinders ； Additionally, pressure will blow out both the solvent and the dissolved acetylene, leading to an increase in acetylene pressure and a potential explosion. Reason 2: When acetylene cylinders are placed horizontally, they tend to roll, and the cylinders may collide with each other or with other objects, generating energy that can lead to accidents involving these cylinders. Reason 3: The acetylene cylinder is equipped with shock-absorbing rubber rings to prevent collisions during loading, unloading, transportation, and use. The rubber ring is an insulating material; when the cylinder is placed in a horizontal position, it is equivalent to placing the acetylene cylinder on an electrical insulator. This prevents the static electricity generated on the cylinder from dissipating into the ground, causing it to accumulate on the cylinder itself, which can lead to the formation of static sparks. In the event of an acetylene leak, this can easily result in fires and explosions. Reason 4: When in use, the cylinder valve of the acetylene cylinder is equipped with a pressure reducer and a flame arrester, as well as rubber hoses connected to it. Since it tends to roll when placed on its side, rolling can easily damage the pressure reducer and flame arrester or cause the rubber hoses to come loose, resulting in the leakage of acetylene gas and leading to combustion and explosion. In summary, acetylene cylinders must be placed upright. Why do gas cylinders need anti-tilt measures? Answer: Dumping can cause the cylinder valve to fall off and result in gas leakage; due to the strong reaction force caused by this leakage, the cylinder may shoot forward or roll on the ground, which could injure anyone nearby. If it is a flammable gas, it can cause an explosion, which is even worse! 1. Why should oxygen and acetylene cylinders be stored separately? Answer: Acetylene is flammable, while oxygen is a combustion supporter. If acetylene leaks and mixes with air, it can cause a violent explosion when exposed to sparks or an open flame. The explosion then damages the oxygen cylinders, causing oxygen to leak out; the oxidizing property of oxygen makes the explosion even more intense. It cannot be controlled. So the two of them cannot be put together. 2. Why should the bottle temperature not be exposed to direct sunlight? Answer: The temperature of an acetylene gas cylinder must not exceed 40 degrees. The boiling point of propyne is 58 degrees; the higher the temperature, the faster propyne evaporates, resulting in the release of acetylene and a sharp increase in pressure inside the cylinder. 3. Why must there be residual pressure in acetylene cylinders and oxygen cylinders? Answer: Leaving a few kilograms of pressure in the bottle, so that the pressure inside is higher than that outside, prevents other gases from entering and ensures safe use. Because acetylene has a very low explosive limit, even a small amount of air mixed in can cause an explosion when the temperature reaches a certain level. Therefore, an exhaust valve must be installed on the outlet of the acetylene cylinder to prevent air from entering the cylinder; otherwise, there is a risk of explosion during the next use. The pressure relief valve is used to prevent the pressure inside the cylinder from dropping below that of the surrounding air, thus avoiding backflow of air into the acetylene cylinder; oxygen cylinders should retain a residual pressure of at least 0.098–0.196 MPa gauge pressure. Acetylene cylinders should maintain a residual pressure of 49Kpa to 98KPa in winter, and 196KPa in summer. 4. Why must oxygen cylinders, especially their openings, not be contaminated with or in contact with oily substances? Answer: Oils, especially those containing unsaturated fats and fatty acids, easily vaporize and release heat. Oil-soaked gauze and oilcloth can self-ignite because of oxidation occurring in the air; the heat generated is not dissipated, and when it reaches the ignition temperature, self-ignition takes place. Oils, on the other hand, vaporize more slowly in the air, and the heat generated is dissipated quickly, so they generally do not accumulate heat to the point of spontaneous ignition. Due to its strong oxidizing property, pure oxygen can cause combustible materials to burn violently. When oily substances come into contact with pure oxygen, their vaporization rate **increases**. A large amount of heat is released at the same time. The temperature rises rapidly, which can easily lead to combustion. If grease gets on the nozzle of an oxygen cylinder, the rapid flow of oxygen causes the grease to undergo rapid oxidation. Moreover, the heat generated by the friction between the high-pressure gas stream and the nozzle further accelerates this oxidation process. As a result, grease attached to the oxygen cylinder or pressure regulator can lead to combustion, or even an explosion. This is why grease must absolutely not come into contact with oxygen cylinders, especially their nozzles and other components that come into contact with oxygen. 5. Why are cylinder caps needed for gas cylinders? Answer: This is because the valve caps on gas cylinders are mostly made of copper alloys, which are relatively fragile. Although some are made of steel, their structure is smaller than that of the cylinder body; when screwed onto the cylinder body, it creates a right angle between the cylinder neck and the valve cap connection. This area is both a weak point and a protruding part of the cylinder body, making it most susceptible to mechanical damage or external impacts. During handling, storage, or use, if the cylinder is accidentally damaged due to drops, falls, rolling, or impact with other hard objects, the connection between the cylinder valve fitting and the cylinder neck can easily break completely. Consequences of a broken bottleneck or valve: When the valve on an oxygen cylinder breaks, the high-pressure gas inside the cylinder, at 150 kilograms per square centimeter, escapes uncontrollably. The force generated by this escaping gas causes the cylinder to shoot in the opposite direction, which can damage machinery, buildings, and even result in injuries or deaths ； When the valve of an acetylene gas cylinder breaks, the flammable gas escapes and mixes with air to form an explosive mixture, which explodes when exposed to an open flame. The high-speed ejection of gas from the bottle will, depending on the properties of the gas in the cylinder, lead to more severe secondary accidents (such as fires, explosions, poisoning, etc.). If the bottle contains a flammable gas, static electricity generated by the intense friction from high-speed spraying, or exposure to other ignition sources, can cause combustion and explosion. On the other hand: since the bottle valve is exposed, it is prone to being contaminated by dust or oils during handling and storage, which poses a risk. Wearing a safety helmet can prevent dust or oily substances from sticking to and entering. To eliminate the aforementioned risks, it is required that bottle manufacturing units equip cylinders with safety caps at the time of production. When using the gas, remove the safety helmet and place it in a designated location; after use, put the bottle cap back on and tighten it properly – never discard it carelessly. Never forget to wear a safety helmet when lifting and loading/unloading. 6. Why should acetylene cylinders not be collided with? Answer: Collisions can cause the activated carbon to break apart, increasing the volume available for expansion; as a result, acetylene gas accumulates under high pressure, posing a risk of explosion ； At the same time, as the temperature rises, gaseous acetylene undergoes polymerization and explodes. 7. Why is it required to handle gas cylinders gently, and why is throwing, rolling, or colliding with them strictly prohibited? Answer: If a gas cylinder is subjected to severe collisions or impacts, an explosion can occur, with very serious consequences. During the loading and unloading of gas cylinders at a company in Shanghai, an employee was hit, resulting in their immediate death! Image Image Image 8. Why cannot oxygen cylinders be lifted? Answer: Oxygen cylinders are high-pressure containers, and if they fall accidentally, they can easily explode. For bulk transportation, there are specialized containers for holding oxygen cylinders, suitable for the one-time transport and handling of multiple cylinders. Image 9: Why do acetylene gas cylinders explode? Answer: The explosion of acetylene cylinders is mainly caused by a sharp rise in temperature and pressure, which leads to the decomposition of acetylene. Characteristics of acetylene decomposition: If flashback occurs, the temperature of the bottle wall rises (starting from the top of the bottle), or smoke-containing gases with an abnormal odor escape from the open bottle valve. This indicates that acetylene has begun to decompose; if the acetylene cylinder is exposed directly to flames or radiant heat, there is a risk of decomposition at any time. Reasons for acetylene decomposition: (1) welding tempering ； (2) External heating (flammable materials near the acetylene cylinder, with unextinguished welding or cutting tools hanging on the cylinder) ； (3) Fire of acetylene near the cylinder valve or pressure regulator ； (4) Severe impact or vibration. Precautionary measures: (1) Install a flame arrester ； (2) It is strictly prohibited to expose it to direct sunlight, heat the bottle, or place it near heat sources ； (3) It is strictly prohibited to hang unextinguished welding or cutting tools on acetylene cylinders ； (4) Handle with care to avoid severe impacts or vibrations. 10. Why cannot oxygen tape and acetylene hoses be used together? Answer: Oxygen tape is for high-pressure pipes, while acetylene tape is for low-pressure pipes ； Additionally, acetylene pipes may experience slight backfire during use, and carbon deposits can form inside them; these deposits, when mixed with oxygen, can cause explosions. 11. Why cannot gas cylinders be mixed or used together? Answer: Filling a gas cylinder with other gases can cause violent explosions, with extremely serious consequences. 12. Why must the bottom of an oxygen cylinder be insulated when it is used at the same work site as welding? Answer: To prevent the gas cylinder from becoming charged. When working alongside welders (which is a prerequisite), insulating material is placed at the bottom of the oxygen cylinder to prevent the cylinder from becoming charged. Metallic equipment such as pipes in contact with gas cylinders must have a proper grounding system to prevent static electricity from causing fires or explosions. 13. Why cannot acetylene cylinders be used on insulators? Answer: The ignition energy of acetylene is only 0.019 millijoules; a tiny static discharge (a few millijoules) can ignite (explode) acetylene. When acetylene flows through pipelines or leaks, static electricity is generated, and any form of static discharge can ignite the acetylene. Since the combustion and explosion of acetylene do not require oxygen, there is a high possibility of an explosion once it is ignited. If the acetylene cylinder is directly grounded to prevent it from accumulating static electricity, it certainly will not explode on its own. 14. Why should the copper content in copper alloy tools used with acetylene cylinders be below 70%? Answer: When acetylene comes into prolonged contact with copper or silver, it forms explosive compounds such as copper acetylide and silver acetylide. These compounds can explode when subjected to strong vibrations or when the temperature reaches 110–120°C. Summary of key points for using gas cylinders Oxygen cylinders: 1. The oxygen in the cylinder must not be used up completely; a residual pressure of 0.1 Mpa should always remain to prevent explosions caused by acetylene backflow. 2. It is prohibited to operate gas cylinders with oily hands or tools to prevent explosions. 3. Oxygen cylinders must not be subjected to severe impacts. Throwing, dropping, and other methods that may cause collisions are prohibited for loading, unloading, or handling; lifting with cranes is strictly forbidden. 4. When opening the bottle valve and pressure reducer, one should stand to the side ； The start-up speed should be slow to prevent excessive heating of the organic material components or the generation of static sparks due to rapid airflow, which could lead to combustion. 5. In winter, when the pressure regulator and piping of the gas cylinder freeze, it is strictly forbidden to use fire to heat them or to strike the cylinder with tools such as iron; moreover, the adjustment screw of the pressure gauge must not be twisted forcefully, in order to prevent a sudden release of large amounts of oxygen that could cause an accident. 6. The use of oxygen cylinders without pressure regulators is prohibited. Acetylene cylinder: 1. An acetylene gas cylinder must be equipped with a dedicated pressure regulator and a backfire arrestor when in use. It is necessary to check whether these devices are functioning properly before use; otherwise, the cylinder shall not be used. When opening the cylinder, the operator should stand to the side and behind the valve, and move slowly. 2. Gas cylinders must not be placed near heat sources or electrical equipment. In summer, shading measures should be taken to prevent exposure to direct sunlight, and the distance from open flames must be more than 10 meters (for work at heights, this refers to the horizontal distance from the vertical ground surface). 3. When the bottle valve freezes, it is strictly prohibited to use heat to thaw it; instead, warm water at below 10°C can be used for thawing. 4. When the work location changes frequently, it should be placed on a dedicated trolley; acetylene cylinders and oxygen cylinders should not be kept together. 5. Copper, silver, mercury, and their products must not come into contact with acetylene; copper alloy utensils that come into contact with acetylene must have a copper content of over 70%. 6. The gas in the bottle must not be exhausted completely; a residual pressure of no less than 0.05 Mpa must remain. 7. When transporting acetylene cylinders by car or trolley, handle them gently. Throwing, sliding, rolling, or touching is strictly prohibited. When lifting and transporting, specialized clamps and rainproof transport vehicles should be used; it is strictly prohibited to use cranes or chain hoists for such purposes. Cylinder placement: 1. Oxygen cylinders and acetylene cylinders must not be placed near heat sources, electrical equipment, oils, or other flammable materials. 2. When using an acetylene cylinder, it is necessary to secure it properly to prevent it from tipping over; it must never be used in a horizontal position. If an acetylene cylinder is already in a horizontal position, it cannot be used immediately – it must first be placed upright and left to stand still for 15 minutes before the pressure regulator can be connected. 3. When using, transporting, and storing acetylene cylinders, the ambient temperature must not exceed 40°C. 4. Acetylene cylinders should be placed upright, with measures in place to prevent them from toppling over, and must not be placed on insulators such as rubber. 5. The distance between gas cylinders and open flames should generally be no less than 10 meters. The distance between oxygen cylinders and acetylene cylinders should be more than 5 meters. 6. Oxygen cylinders and acetylene cylinders must be placed in fixed positions and marked, using yellow lines with a width of 50 mm.