Possible accidents in the operation of liquefied natural gas

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Accidents that may occur in the handling of liquefied natural gas: In the industry dealing with liquefied natural gas, fires, leaks, and frostbite accidents related to this gas can occur. Guided by the principle of “people-oriented and prevention-first” ； Unified leadership with hierarchical responsibility ； The principle of “rapid response and integration of peacetime and wartime operations”. Great emphasis is placed on the safety of liquefied natural gas, with continuous efforts to prevent problems before they occur. Strengthen the sense of urgency, adhere to a combination of prevention and emergency response as well as normal and abnormal situations, and make all necessary preparations to deal with liquefied natural gas accidents. I. Physical Hazard Characteristics of Liquefied Natural Gas: Liquefied natural gas is flammable, explosive, prone to diffusion, capable of generating static electricity, toxic, and requires low temperatures to exist. 1. Flammability: Liquefied natural gas is classified as Category A/B in terms of fire hazard; such gases are highly flammable, requiring only a small amount of energy to ignite – even a tiny spark is sufficient to cause ignition. 2. Explosiveness: When liquefied natural gas mixes with air to reach its explosive limit, it can explode upon encountering an ignition source. The wider the range of explosive limit concentrations for a chemical substance, and the lower the lower limit of those concentrations, the greater its explosive hazard. The explosive limit for natural gas is 4.96%–15.3%. 3. Static charge accumulation: Liquefied natural gas is an insulating gas; during pipeline transportation, friction between the natural gas and the pipe walls generates static electricity, which is difficult to eliminate. When electrostatic discharge occurs, electric sparks are generated; if the energy of these sparks is equal to or greater than the minimum ignition energy of natural gas, and the concentration of natural gas is within its explosive range, an explosion or combustion can occur immediately. 4. Diffusibility: Liquefied natural gas does not tend to accumulate in low-lying areas after leaking, exhibiting good diffusibility. However, when a large amount of natural gas leaks, and under suitable weather conditions (such as low wind speeds), it can accumulate in a small area, forming an explosive vapor cloud that can explode upon contact with a fire source. Severe accidents have occurred both domestically and internationally, where leaked natural gas spread and ignited in the presence of open flames, leading to explosions. 5. Asphyxiation, toxicity: Although methane, the main component of natural gas, is non-toxic in itself, high levels of methane in the air can cause oxygen deprivation and asphyxiation in people. When the methane concentration in the air reaches 25%-30%, it can lead to symptoms of oxygen deficiency and even asphyxiation. Like natural gas, it is a hydrocarbon mixture and belongs to substances that are sensitive to low temperatures; long-term exposure to it can lead to neurasthenia syndrome. 6. Low-temperature properties: The storage of liquefied natural gas takes place under low-temperature conditions at around -162°C. In the event of a leak, apart from the potential for frostbite and similar effects on personnel in close proximity to the leak site, the extremely low temperature may also cause brittle fracture in other structures, equipment, and instruments that are not designed to withstand such cold conditions, thereby leading to secondary damage. II. Analysis of Hazardous Factors 1. Fires and Explosions: The liquefied natural gas stored at gas stations is a flammable and explosive hazardous chemical. During the production process, if it is affected by various external factors and leaks, an explosive mixture can be formed; in the presence of an ignition source, fires and explosions can occur. Fires and explosions are the main hazard factors for the production facilities at this station. a. LNG leaks can cause fires and explosions. Factors such as corrosion of equipment and pipelines, poor installation quality, and fluctuations in temperature can easily lead to leaks in pipelines, equipment, their connection points, valves, flanges, etc., resulting in fires and explosions. b. Inhaling air can cause explosions in equipment or systems. When a production system is not in normal operation, factors such as improper connections, operational errors, failed safety interlocks, inadequate inspections, as well as defects in the equipment and pipelines can result in negative pressure within these components. Air then enters the equipment or pipelines, where it mixes with combustible gases present there, forming explosive gases. Under the influence of high temperatures, friction, static electricity, and other such factors, an explosion can occur. c. The oxygen content exceeds the specified limit, leading to an explosion due to \"peroxides\". When operational errors or equipment defects cause the oxygen content in the equipment or production system to exceed the prescribed levels, it reaches the explosive threshold and an explosion occurs. d. Fires and explosions caused by electrostatic discharge of high-pressure gases. During the loading, unloading, storage, and transportation of liquefied natural gas, fast-flowing high-pressure flammable gases can easily generate and accumulate static electricity. In dry weather, charges can also accumulate on the ground. If anti-static measures for equipment and facilities are not in place or are ineffective, the static electricity cannot be eliminated in time; when the static potential rises to a certain level, electrostatic discharge occurs, resulting in static sparks that can lead to catastrophic accidents. 2. Frostbite: During the evaporation of liquefied natural gas, a large amount of heat is absorbed, causing the surrounding temperature to drop significantly, which can lead to frostbite in humans. At gas filling stations, workers may suffer from frostbite when they come into contact with cold areas, or with leaked liquids or gases, due to equipment failures or damages during operation or maintenance. 3. Poisoning and asphyxiation: The main hazardous substance in gas stations that can cause poisoning and asphyxiation is natural gas. Methane, the main component of natural gas, is essentially non-toxic to humans; however, at high concentrations it significantly reduces the oxygen level in the air, leading to suffocation. When methane levels in the air reach 25%–30%, it can cause headaches, dizziness, fatigue, difficulty concentrating, accelerated breathing and heartbeat, and even coma. If not removed in time, it can lead to death from suffocation. Prolonged exposure to natural gas may lead to neurasthenia syndrome. Therefore, poisoning from natural gas leaks is also a very prominent hazard and harmful factor at this station. Leaks in gas pipelines, containers, and valves, combined with poor ventilation in the environment and prolonged exposure of workers to low concentrations of oil and gas, can easily cause harm to their physical and mental health. In the event of a sudden large-scale leakage of natural gas, people in the affected area are at risk of suffocation. 4. Electric shock: Gas stations use a large number of electrical devices. The distribution circuits used in the production process, various electrical-powered production equipment, lighting circuits and lighting fixtures, as well as distribution boxes and mobile electrical equipment or hand-held power tools used for equipment maintenance, all pose risks of electrical injuries, direct contact electric shock, and indirect contact electric shock. 5. Container explosion: The storage tanks, boosters, flow meters, etc. at gas stations are all pressure-bearing devices and thus classified as pressure vessels. If these pressure vessels and pipelines are not equipped with the necessary safety devices such as safety pressure relief devices, safety valves, and explosion-proof plates, it is possible for excessive pressure to build up within them, preventing timely pressure release and leading to explosion accidents. 6. Mechanical injuries: In gas station pumping and other rotating equipment, if the protective measures are inadequate or defective, mechanical injuries can occur, especially during accidents or maintenance activities. Various mechanical devices used in production, such as air compressors and hydrocarbon pumps, are machines that rotate at high speeds or move back and forth; their components or parts can cause mechanical injuries to operators, maintenance staff, and inspectors, including accidental pinching, collisions, shearing, entanglement, crushing, and cutting. 7. Fall from height: In the storage tank areas and production equipment areas of gas stations, there are often work locations at heights of 2 meters or more (including 2 meters) where tasks require performing specific operations or inspections at such heights, and falls from height can pose a risk in such situations. When performing tasks at heights such as routine inspections, sampling, and maintenance, falls from height can result in injury accidents. Furthermore, when performing operations, inspections, and maintenance at heights, if the work platforms or scaffolding used do not comply with safety regulations ； Without taking protective measures, there is a risk of falling in all cases. 8. Vehicle accidents: Accidents that pose a threat to the safety of people and vehicles can occur due to external LNG transport vehicles, as well as vehicles within the facility – factors such as mechanical braking failures, poor road conditions, the driver’s lack of attention, improper loading and unloading procedures, adverse weather conditions, speeding, and illegal driving by the driver.   The potential risk levels of LNG refueling stations are shown in Table 2-3. III. Responsibilities of the Fire Fighting and Rescue Team: Strengthen the development of emergency response teams based on local management, build a well-trained and highly skilled team capable of handling complex situations, raise the awareness of all employees regarding the prevention of work-related safety accidents, and integrate daily work, training, learning, and emergency rescue activities. Make adequate preparations in terms of mindset, organization, and resources to deal with production safety accidents; continuously improve emergency equipment, facilities, and methods, and enhance the technical capabilities for emergency response. Establish a coordinated mechanism for joint action, fully mobilize the role of each station, and rely on their capabilities to create an emergency management system that features unified command, rapid response, comprehensive functions, orderly coordination, and efficient operation. 1. Responsibilities of the fire fighting and emergency response team: Its task is, in the event of an accident, to immediately dispatch fire emergency responders to the scene based on the nature of the accident, to control potential hazards, carry out fire suppression, search for people trapped at the site, seal leaks in equipment and containers, and organize the evacuation of people. (1) Be familiar with the topography and landforms of the company’s affiliated units, as well as the characteristics of various types of equipment, and the physical and chemical properties of liquefied natural gas. (2) Be familiar with the purposes, operating methods, storage locations, and scope of use of various fire extinguishing equipment and facilities. (3) Understand various emergency response methods and routes, as well as the storage locations of repair tools, equipment, and accessories. (4) In the event of an accident, all team members must promptly proceed to the emergency assembly point, follow the instructions of the team leader, and carry out fire fighting and rescue operations as ordered. (5) After the public security fire brigade arrives at the scene, assist them in their fire fighting and emergency response efforts. (6) Responsible for assisting the public security fire brigade with on-site decontamination work after the accident is brought under control. 2. Responsibilities of the medical rescue team: Its task is to provide emergency assistance to those who are injured, poisoned, or suffering from suffocation. *Responsible for providing emergency treatment to injured people at the scene. *Responsible for escorting severely injured persons to the hospital for treatment. *Preventive measures IV. Prevention and early warning Preventive measures *Strengthen the management of ignition sources at gas stations; smoking (matches, cigarettes, lighters) and the use of mobile phones are strictly prohibited, and vehicles must have their engines turned off while refueling. *Strengthen the maintenance and management of equipment by regularly checking fire-fighting equipment installed in designated locations, gas detectors, tools for plugging leaks under pressure, explosion-proof tools, the sprinkler systems in tank areas, emergency water supply and power supplies for firefighting, as well as protective equipment (including positive-pressure air respirators and first-aid supplies). Ensure that fire evacuation routes remain unobstructed, and that all fire-fighting equipment, emergency response tools, facilities, and apparatus are in ready condition. *Strengthen on-site inspections, particularly those related to lightning and static electricity protection, to ensure their effectiveness. *Strengthen the management of equipment maintenance; keep the moving parts of pumps and machinery clean to prevent the accumulation of debris that could lead to combustion due to friction. *All electrical and instrumentation equipment is installed as explosion-proof devices. Lightning and static electricity protection grounding measures have been taken for buildings, storage tanks, pipelines, as well as filling and transfer equipment and facilities. *Strengthen electrical management by carrying out regular maintenance of electrical equipment. When poor insulation of the equipment or aging of circuit insulation is detected, the electrical equipment and circuits should be replaced promptly. *In the event of a fire, measures such as sealing leaks and extinguishing the fire are taken based on the conditions at the scene. *Strengthen the practice of emergency plans and continuously improve the accident emergency response plans. The company’s emergency response procedures are shown in the diagram: V. Provision of rescue materials and equipment: Emergency rescue equipment, leak-sealing tools, supplies, medicines, fire-fighting equipment, and personal protective equipment are all readily available, and regular inspections and maintenance are mandated to ensure they remain in good working condition at all times. The allocation of specific materials and other equipment. Emergency supplies and equipment for LNG refueling stations: Sufficient emergency supplies and equipment must be available as required, stored in designated locations, kept under the care of designated personnel, and regularly maintained, serviced, and inspected to ensure they are in good condition and ready for use at any time. Based on the operational conditions of this site, a certain amount of emergency equipment and supplies are allocated to each reserve station. For example: 1. Protective equipment: anti-static work clothes, anti-static safety shoes, low-temperature resistant protective masks, low-temperature resistant protective clothing, low-temperature resistant insulated gloves, positive-pressure air respirators. 2. Explosion-proof equipment: explosion-proof portable lighting fixtures, explosion-proof tools, portable combustible gas concentration detectors. 3. Communication equipment: landline phones, explosion-proof mobile phones, explosion-proof walkie-talkies (cell phones). 4. Medical equipment: first-aid kits, disinfectants, emergency supplies. 5. Fire extinguishing equipment: wheeled dry powder fire extinguishers, portable dry powder fire extinguishers, portable carbon dioxide fire extinguishers, fire blankets, fire buckets, fire axes, and fire shovels, which are stored in key areas throughout the gas station. 6. Lightning and static electricity protection facilities and equipment: static electricity grounding facilities, static electricity clamps for gas release, static electricity-resistant work clothes, static electricity-resistant safety shoes, surge protectors for power supplies in electrical control rooms, and emergency lights. 7. Safety equipment: safety helmets and personal protective equipment. 8. Equipment for repairs: explosion-proof tools, sealant materials, etc. 9. First-aid supplies: first-aid kits, medicines, etc. 10. Rescue vehicles.