Production Technology [Weekly Topic]: Handling of Gas Leaks (2011-03-28~04-03)

1. First, the equipment or piping must be kept under positive pressure to prevent the formation of a gas mixture within the explosive limits. Nitrogen purging can be performed. 2. If it’s a standalone device and wasting it is acceptable, it can simply be set on fire using an open flame until it burns out. 3. Remember never to close the valve connected to the atmosphere! Please let me know if there’s anything else!

A combustible gas alarm is installed. 1. In an open area, the gas supply can be shut off directly, and fire-resistant steam can be used to disperse the gas； 2. In enclosed spaces, a small leak can be addressed by cutting off the gas supply and ventilating the area. However, in cases of a large leak, ventilation must be avoided to prevent the formation of an explosive mixture. Instead, the gas supply should be cut off, and nitrogen should be used for purging. Only after the purging is confirmed successful can ventilation and repairs be carried out ； 3. Also, as mentioned above, when the leakage becomes uncontrollable, set it on fire.

First, cut out the area where the leak is occurring, evacuate unauthorized personnel, prohibit any operations that involve open flames or that could generate static electricity or sparks. Dilute the area using water mist or steam, and then displace the leaking gas with nitrogen.

1. When the amount of leakage is small, nitrogen should first be used for displacement to prevent the formation of explosive mixtures; the root cause of the incident should be identified. Mobile phones and similar devices must not be used in the area where there is a leakage to avoid the generation of static electricity. 2. If a large amount of toxic gas leaks and cannot be controlled, an emergency shutdown should be carried out and personnel should be evacuated

Cover your mouth and nose with a wet towel, then turn off the main valve. If the valve cannot be closed, fold the gas hose in half and tie it up to contain any gas leaks. After that, immediately notify the gas company. 2. Open all doors and windows to reduce the gas concentration. 3. All sources of ignition are strictly prohibited. Cut off the main power supply at home, unplug the telephone line, and turn off mobile phones. 4. Call 119

This post was last edited by shmily327 on 2011-3-28 at 17:08. 1. Cover your mouth and nose with a wet towel, close the main valve; if it cannot be closed, fold and tie the gas hose to prevent gas leakage, and contact the gas company immediately afterwards. 2. Open all doors and windows to reduce the gas concentration. 3. All sources of ignition are strictly prohibited. Cut off the main power supply at home, unplug the telephone line, and turn off mobile phones.

Combustible gases (liquefied petroleum gas) belong to the category of liquefied gas hazardous chemicals, and their main components include low-molecular-weight hydrocarbons such as propane, propylene, isobutane, butenes, and isobutylene. I. Physical and chemical properties of liquefied petroleum gas (1) Gas properties: It is in gaseous state at normal temperature and pressure, possessing the properties of a gas; its relative density is greater than 1.52, meaning it is heavier than air, and it can spread in all directions along the ground surface. (II) Expansibility: It turns into a liquid upon cooling or pressurization; its relative density is 0.495–0.57, and it can be stored in steel cylinders. Liquefied petroleum gas, which is in liquid form at room temperature when leaked or released, is highly volatile, and its volume can increase rapidly by 250 to 350 times. (III) High calorific value: Burning 1 kilogram of liquefied petroleum gas releases approximately 4.98 x 10^7 joules (11,900 kilocalories) of heat. The expansion rate of its liquid phase upon heating is about 10–16 times greater than that of water. The liquefied petroleum gas inside the container experiences a rapid increase in pressure as the temperature rises. (IV) A colorless gas or yellow-brown oily liquid with a distinctive odor; it is flammable, with an explosion limit of 2.25%-9.65%. Its vapor is heavier than air, allowing it to spread over considerable distances at lower levels; it can cause backdraft when it encounters a fire source. When exposed to high heat, the internal pressure of LPG cylinders increases, posing a risk of rupture and explosion. Liquefied petroleum gas is non-toxic to the human body at low concentrations; at high concentrations, it can cause suffocation by diluting the oxygen in the air. Generally, liquefied petroleum gas contains a certain amount of sulfides such as hydrogen sulfide, which gives it toxicity. Furthermore, starting with propane, the higher the number of carbon atoms in the alkane, the stronger its effect; symptoms associated with liquefied petroleum gas include dizziness, headache, shortness of breath, nausea, vomiting, and a slow pulse ； In severe cases, **loss of consciousness and state of consciousness may occur, and death from asphyxiation is even possible. II. Location and conditions of LPG leaks (1) Locations of LPG leaks and methods for sealing them (2) Dangers and characteristics of LPG leaks 1. Characteristics of LPG leak incidents (1) Rapid spread and wide range of damage. Liquefied petroleum gas typically leaks in a gaseous form, as it changes from a liquid state to a gas state; its volume expands rapidly and it drifts with the wind, creating a large area of dispersion. It is necessary to evacuate people within the affected area promptly and to take measures to prevent the presence of any fire sources. (2) Explosive and combustion accidents are likely to occur. Due to the low explosion threshold of liquefied petroleum gas, when it leaks and mixes with air, it can easily form an explosive mixture that will explode or ignite upon contact with a fire source, resulting in severe casualties and significant property damage. (3) Difficult to dispose of. Due to the variations in the location of the LPG leakage, the size of the cracks, and the pressure inside the container, implementing measures such as sealing the leak, transferring the gas, or igniting it requires high technical skills and makes the handling process very difficult. 2. Characteristics of LPG combustion: When LPG burns, the following phenomena occur: (1) During gas-phase combustion, it produces a bright yellow flame. When the pressure is high and the gas flow rate is large, the flame height can reach over 50 meters, accompanied by a hissing sound of combustion. (2) During liquid-phase combustion, an orange-yellow flame is produced; due to incomplete combustion, a large amount of carbon black is generated, resulting in dense smoke. (3) During mixed combustion of gas and liquid phases, the flame color alternates between yellow and orange-yellow, and the flame height varies periodically between high and low levels. When the flame is low, it is a good time to extinguish the fire. (4) The flame height of a flowing (diffused) LPG combustion is 2–2.5 times larger than the diameter of the combustion surface. 3. Characteristics of LPG explosions (1) The explosive limit range of LPG is relatively wide, approximately 2% to 9.65%. A small amount of liquefied petroleum gas, once dispersed, can create an explosive gas over a large area. When 1 kilogram of liquefied petroleum gas is completely vaporized, its volume is nearly 500 liters; at a concentration of 2%, this can result in 25 cubic meters of explosive gas. Liquefied petroleum gas has great explosive power; its detonation velocity is 2,000–3,000 meters per second. The explosive power of 1 kilogram of liquefied petroleum gas is equivalent to that of approximately 4–10 kilograms of TNT.** Explosions of liquefied petroleum gas can easily lead to large-scale fires, causing significant damage and casualties. (2) When containers holding liquefied petroleum gas (gas cylinders, storage tanks) are heated, the pressure rises rapidly; when it exceeds the design pressure, there is a risk of a physical explosion. When a container explodes, the damage is severe as well; the explosive fragments can be thrown several dozen meters to over 100 meters away. A large amount of liquefied petroleum gas escapes from the container, which may lead to a second explosion (a chemical explosion), resulting in widespread fires. (3) Chemical explosion. III. Measures for dealing with LPG leaks (1) Implement personal protection in accordance with standards. (1) Personnel entering high-risk areas and carrying out actual operations must use level 1 protection. (2) When entering the medium-risk area, personnel shall wear level 2 protective equipment. (3) All personnel involved in on-site handling must have a minimum protection level of Level 3. (II) Key points of rescue: (1) Adhere to the principle of \"evacuating and rescuing people, ensuring safety, and handling the situation in an orderly manner\", and assist professional rescue teams in their efforts. (2) Control and eliminate all potential sources of danger that could cause an explosion. (III) Procedures for dealing with LPG station leaks (1) Handling of leaks that have not caused a fire. Causes of leakage: damaged valves, cracked pipes, broken level gauges, damaged compressors, cracked storage tanks, etc., among which a cracked storage tank poses the greatest risk. (2) Cut off the gas supply and seal the leak. If the valve is damaged, wrap burlap around the leaking area, use a clamp to seal the leak, or employ an external sealing bag to stop the leakage ； In case of a pipe rupture, it can be sealed using wooden wedges or an external sealing bag ； If the compressor is damaged, its operation should be stopped ； The ice-blocking method is used to seal leaks. When liquefied petroleum gas changes from a liquid phase to a gas phase, it absorbs a large amount of heat energy, causing the temperature at the leakage point to drop sharply. When the ambient temperature is low, water is sprayed at the leak site to freeze it, thereby sealing off the leak. (3) Open the relevant valves to direct the liquefied petroleum gas from the leak site to other storage tanks, in order to reduce the pressure at the leakage location. (4) Use the steam or spray water from this unit to disperse the leaked liquefied petroleum gas and prevent it from reaching an explosive concentration. (5) Control all sources of fire. Eliminate all sources of ignition in areas where liquefied petroleum gas has spread; halt all general production activities ； In areas where liquefied petroleum gas has spread, keep the electrical systems as they are – do not turn them on or off. In areas near the zones affected by liquefied petroleum gas, cut off the power supply ； Personnel entering the LPG dispersion area to handle the hazard must be cautious to prevent sparks from static electricity or metal collisions. (6) Set up warning lines to strictly prevent all unauthorized personnel and vehicles from entering the area where liquefied petroleum gas has spread. If liquefied petroleum gas has spread beyond the premises, traffic in the vicinity must be blocked. (7) When the rescue vehicle arrives at the scene, it must not enter the area where liquefied petroleum gas has spread. Instead, it should be parked on the upwind side of the affected area and in a safe, elevated location, while remaining prepared to handle any potential fire or explosion incidents. (8) Issue warnings to people in areas where liquefied petroleum gas may spread; in cases of severe leaks, evacuate those who are not necessary there, and keep the number of people remaining on site for emergency response as low as possible. (9) In the case of an indoor leak, after taking measures to seal the leak, the doors and windows should be opened to vent the liquefied petroleum gas inside; however, ordinary non-explosion-proof exhaust fans must not be used for ventilation. (10) After the hazard has been eliminated, and following tests to confirm that the gas concentration is 10% below the lower explosive limit, normal operations can be resumed, and the safety perimeter can be lifted. IV. Precautions for dealing with LPG leaks (1) Minimize the number of people in the exclusion zone. (2) Operators must wear appropriate personal protective equipment, and all equipment must be grounded during operation. Persons entering the site or restricted area must wear respirators and various protective gear, as well as sealed or rescue chemical-protective suits. Personnel on the periphery should wear 100% cotton clothing, with trouser legs and sleeves tightly fastened. Tighten your belt, and if necessary, wet your entire body before entering the dispersion area. (3) Pay attention to observing the wind direction, terrain, and the status of the fire. Approach the fire site from the upwind or side-upwind direction, select an appropriate parking location. Rescue vehicles should use entrances and passages located in the upwind direction and park in suitable spots there; they should also make use of water sources situated in the upwind area. Choose an attack route on the upwind side of the spread area, approach that area, and set up water gun positions as well as a command post on-site. Be vigilant to prevent explosions, burns, and poisoning. (4) Action can be taken only after sufficient equipment and gear are prepared. While ensuring safety, plug leaks or invert leaking containers to prevent liquid from escaping. (5) Use a spray of water to suppress vapors or alter their direction of flow. It is prohibited to direct water at the leak or its source, in order to prevent the spread of leak-related vapors through sewers, ventilation systems, and enclosed spaces. (6) After extinguishing the fire, a thorough inspection of the scene must be conducted to eliminate all potential hazards and prevent re-ignition or re-explosion. (7) Eliminate all ignition sources (prohibit smoking in the vicinity of the leak area, and remove all open flames, sparks, or fires), and isolate the leak area until the gas has dissipated. (8) In the event of an emergency evacuation, vehicle and equipment can be abandoned to ensure the safety of personnel; commanders at various positions are authorized to have the authority to order an evacuation without seeking approval in cases of serious situations. (9) It is strictly prohibited for response personnel to stay on the tops of underground spaces such as sewers in the leakage area or at the wellheads, to prevent injury caused by explosive shock.

1. The facility should initiate an emergency state, report to the dispatch center, and take measures for evacuation and isolation. At the same time, locate the leak point and shut off the upstream and downstream shut-off valves at the leak point. Notify the fire department. 2. Immediately shut down any devices with open flames in the vicinity, such as heating furnaces. 3. If the leak point cannot be isolated immediately, immediately use fire-fighting steam for coverage. 4. Immediately take pressure relief measures or recover the combustible gas; if recovery is not possible, flare it.

Different flammable gas leaks require different handling methods. For example, the leakage of toxic combustible gases differs from that of non-toxic combustible gases. The handling methods for flammable and explosive gases differ from those for less flammable and explosive (relatively) gases. In short, there is one principle: find out the cause and stay calm. 1. When a gas leak is detected, never shut off the main gas supply valve without knowing the situation. Because tempering can easily occur, leading to explosions in gas pipelines ； 2. Once detected, maintain positive pressure in the system first; if gas leaks under this pressure, stay calm. For toxic gases, it is necessary to ensure that inspection and maintenance personnel do not get poisoned (appropriate safety measures must be in place). Positive pressure leak repair welding operations or other procedures for fixing leaks can be carried out ； 3. If the leak occurs indoors, it is necessary to ensure good ventilation; exhaust fans can be used to disperse the flammable gases that have leaked into the room, so as to prevent these gases from reaching their explosive limit inside the room ；

Actually, this is a very big topic. Generally speaking, regarding the handling of leaks. Our preferred method is to cut off or block it. When it is not possible to cut off or block the flow, measures such as reducing pressure, diverting the flow, and lowering concentration must be considered; meanwhile, various safety issues must also be taken into account before and after taking such actions.