What are the precautions for using pure oxygen? That boss gave me a detailed introduction.

This post was last edited by jbcyf on 2011-11-17 at 15:31. Properties of oxygen: Oxygen is one of the most widely distributed elements in nature, and it is a substance upon which living organisms depend for survival. It exists in the air in a free state; by volume, oxygen makes up 20.93% of the air. Oxygen exists in combined form in water, minerals, as well as in all animals and plants. Oxygen is a colorless, transparent, tasteless, and odorless gas at room temperature and pressure, and it is slightly heavier than air. At atmospheric pressure, when cooled to -182.96°C, oxygen condenses into a sky-blue, transparent, and fluid liquid; when the temperature reaches -218.4°C, it forms blue solid crystals. Oxygen has highly reactive chemical properties; it is a strong oxidizing agent and a fuel accelerator. Apart from generally not reacting with gold, silver, and the inert gases helium, neon, argon, krypton, and xenon, it can react with other substances to form oxides. The intensity of the oxidation reaction depends on the concentration and pressure of oxygen; if the oxidation reaction takes place in pure oxygen, it is extremely intense, with a large amount of heat being released. (For example, when metals react with oxygen, increasing the purity and pressure of oxygen significantly accelerates the oxidation reaction; the ignition point of metals decreases as the oxygen pressure rises.) When oxygen is mixed in a certain proportion with flammable gases such as acetylene, hydrogen, and methane, an explosion occurs upon exposure to fire. After being compressed, oxygen generates a large amount of frictional heat during transportation when there is oil, iron oxide particles, or small combustion residues (such as coal dust, carbon particles, or organic fibers) present; these substances rub against the pipe walls or the machinery as they move with the airflow, resulting in fires in the pipes and machinery. 2. Selection of oxygen hoses 2.1 Oxygen hoses are composed of an inner rubber layer, an outer rubber layer, and a middle cotton fiber layer; the entire hose must undergo special chemical treatment to prevent its high flammability. The following safety requirements should be observed in the manufacturing, storage, transportation, and use of hoses: 2.1.1 Hoses shall possess sufficient strength and flame-retardant properties ； 2.1.2 It is essential to pay attention to the proper maintenance of hoses during storage, transportation, and use, to keep them clean and undamaged ； For example: avoid exposure to sunlight and rain or snow, and prevent contact with substances such as acids, alkalis, oils, and other organic solvents that can affect the quality of the rubber hoses. The storage temperature is -15 to 401°C. It should be kept at a distance of at least 1 meter from heat sources. If proper maintenance is not carried out during storage and use, or if the rubber hoses age over time and become brittle, the sulfur compounds in these hoses can decompose, often leading to flashback explosions ； 2.1.3 Before using the new hose, the talcum powder on its inner wall must be thoroughly blown away. During use, it should be protected from external compression and mechanical damage; it must not come into contact with substances that can affect the quality of the rubber hose, and the hose body must not be folded ； 3. Degreasing of oxygen pipelines: Compressed oxygen will ignite violently and cause an explosion upon contact with even a small amount of grease; therefore, the pipes, fittings, gaskets of oxygen pipelines, as well as all materials that come into contact with oxygen, must be thoroughly degreased before installation and use. 3.1 Degreasing Agents The properties and uses of commonly used degreasing agents are shown in the table below: Chart showing the properties of common degreasing agents. Name of degreasing agent, range of application, and notes: Industrial ethylene dichloride, C2H3Cl2 – Can hydrolyze metal parts to produce trace amounts of hydrochloric acid. Industrial carbon tetrachloride, CCl4 – Black metals, copper, and non-metallic parts can undergo hydrolysis in the presence of water and metals, resulting in trace amounts of hydrochloric acid; it also reacts violently with certain highly reactive light metals, potentially leading to explosions. Industrial trichloroethylene, C2HCl3 – The product must not contain stabilizers. Pure trichloroethylene without stabilizers does not corrode ordinary metals. Industrial alcohol, C2H5OH – With a concentration of at least 95.6%; its degreasing ability is relatively weak for equipment and components that do not require high levels of degreasing. 3.1.1 Ethylene dichloride, carbon tetrachloride, and trichloroethylene can undergo hydrolysis under certain conditions to produce trace amounts of hydrochloric acid; therefore, pipes and fittings that need to be degreased must be free of moisture, otherwise corrosion will occur ； 3.2 Degreasing method: Before degreasing the pipes, the rust, oil, and organic substances on their surface must be removed first, after which a degreasing agent is used for degreasing. 3.2.1 Degrease the inner surface of the tube by injecting a solvent into it, and seal the tube ends with wooden plugs or other methods. After pouring in the solvent, block the other end as well, then place it horizontally and keep it in that position for 15-20 minutes ； Flow the tube 3-4 times during this time: then introduce the degreaser into the container ； The tube can also be tilted on a frame, after which wire is used to tie the velvet cloth around it and pass it through the tube; then the degreasing agent is introduced into the tube, and the wire is pulled back and forth several times ； 3.2.2 When degreasing is required on both the inside and outside of the tube, pour the degreaser into a special tank, place the tube in the solution for 15–20 minutes; during this time, turn the tube several times and clean it with a brush ； The tanks should be equipped with sealing lids to prevent the evaporation of degreasers; large-diameter pipes can be cleaned by wiping ； 3.2.3 Before degreasing, the valve must be ground and pressure-tested to ensure it meets the requirements; thereafter it is disassembled into its components, immersed in a degreasing agent for 1–1.5 hours, and cleaned with gauze to be considered qualified ； Bolts and metal gaskets are degreased in the same way; for valve housings that cannot be submerged, the wiping method can be used ； 3.2.4 For the degreasing of non-metallic gaskets, carbon tetrachloride solvent should be used. The gaskets are immersed in the solvent for 1.5–2 hours, after which they are removed and hung in a well-ventilated area or within a ventilation system, where they are dried one by one until no odor of the solvent remains ； 3.2.5 After degreasing, the liquid degreasing agent inside the parts should be removed as soon as possible; this can be done by using clean, oil-free, dry air or nitrogen to blow it away ； For flammable solvents, use nitrogen with a purity of over 95% for drying ； Evaporation drying is prohibited as a method for removing residual liquid ； 4. Safe transportation and management of oxygen 4.1 Fire hazards during oxygen transportation The reasons for fires and explosions caused by valves in oxygen delivery pipelines include the following aspects ； Rust, slag, and other impurities in the oxygen pipeline rub against the inner wall of the pipeline, or collide with valve plates and elbows, as well as with each other; this friction generates high temperatures that lead to combustion. Its danger is directly related to the type and size of the impurities as well as the oxygen flow rate; for example, when the pipes contain iron oxide scale or slag and the oxygen flow rate is 44 meters per second, or when the impurities are anthracite and the oxygen flow rate is 13 meters per second. It can also heat the pipe wall red. The relationship between the particle size of iron powder and the combustion temperature is shown in the table below: Particle Size (mesh) Temperature (°C): 10–20: 421; 20–30: 408; 30–50: 392; 100: 385; 200: 315. Flammable substances such as grease, solvents, and rubber found in oxygen pipelines and their fittings will burn rapidly when exposed to high-purity, high-pressure oxygen streams. Their ignition points are listed in the table below: Ignition Points of Several Flammable Substances in Oxygen Name Ignition Point in Oxygen (°C): Lubricating oil: 273–305; Steel paper gaskets: 304; Rubber: 130–170; Neoprene: 474; Trichloroethylene: 392; Polytetrafluoroethylene: 507. 5. Requirements for Oxygen Use and Maintenance of Oxygen Equipment 5.1 The production workshop must be kept clean. Oil-stained rags and cloths should be removed regularly; lubricants should be stored in a separate area, and used oil must be collected and disposed of promptly. Workers who are exposed to oxygen, or whose clothing is contaminated with oil, should clean themselves or change their clothes immediately to avoid any hazards ； 5.2 The use of oxygen valves and related matters must be handled by a designated person ； 5.3 The opening of the oxygen valve must be done slowly; the operator should stand to the side of the valve. When using a valve equipped with a bypass valve, the bypass valve should be opened first. Pressurize the downstream side first; the main valve should be opened only when the pressure difference across it is less than or equal to 0.3 MPa. Moreover, the person who operates the oxygen valve must not wear gloves contaminated with oil ； 5.4 The valve must not be tampered with without the permission of qualified professionals ； 5.5 Once the valve is opened as specified, it is prohibited to use non-regulating valves for regulating purposes ； 5.6 When an oxygen pipeline catches fire, the upstream gas supply should be cut off immediately ； 5.7 Oxygen pipelines made of 5.7 carbon steel should be purged every 5 years, and their wall thickness should be tested every 5 years ； It mainly measures the pipes behind elbows and control valves ； (Our company has now replaced all oxygen pipelines with stainless steel pipes.) 5.8 Users who employ wet oxygen should regularly drain water from the pipelines ； 5.9 Before performing hot work on oxygen pipelines, a hot work plan must be prepared first ； Its contents include the person in charge, operation procedures, safety measures, role assignments, supervisors, and testers, etc.; it can only be carried out after approval by the relevant departments ； (The oxygen content must be kept below 21%) ； 5.10 When performing maintenance on oxygen pipelines or valves, the oxygen must be drained; work can only begin once the pressure has dropped to zero. Before starting the work, tools and spare parts must be thoroughly degreased to prevent fires and explosions ； 5.11 When repairing oxygen pipeline valves and pipelines, maintenance personnel must not wear gloves contaminated with oil ； Maintenance tools must be dedicated, and strict degreasing is required ； 5.12 No open-flame operations are allowed within 10 meters of the oxygen maintenance area, and the communication devices of the maintenance personnel and supervisors must be turned off ； Unrelated personnel must be taken outside the boundary area ； 5.13 If replacing the oxygen hose or check valve, nitrogen should be used to purge the hose and check valve in order to prevent impurities inside the hose from blocking the pipeline and causing safety accidents ； 5.14 Rubber gaskets are strictly prohibited from being used as spare parts for repairing oxygen valves and pipelines. 6. Compression of oxygen: Maximum compression ratio for oxygen is 1:6 ； Maximum operating pressure: 35MPa ； Oxygen is a highly reactive element that can combine with almost all substances. It is a gas with very active chemical properties, and improper use of it can lead to serious accidents such as fires or explosions. Therefore, when using oxygen, it is essential to strictly follow the operating procedures specified by the equipment in order to ensure its safe use and management.