As one of the most important domestic gas and industrial fuels in China, accidents that occur during the production, storage, transportation, etc. of liquefied petroleum gas cause leakage, causing explosions and fire accidents to increase. Once the leakage of LPG occurs, due to its special physicochemical properties, the on-site disposal of the accident is very complicated and difficult. It is necessary to take effective measures to eliminate the danger and completely eliminate the dangers without leaving hidden dangers.
Disposal of Leakage of Liquefied Petroleum Gas Tanker
1 Set the alert area
The potential danger of leaking liquefied petroleum gas is continuous evaporation of the leaking gas, and it is difficult to accurately predict the diffusion range. Any weak fire source within the diffusion range can cause combustion or explosion. Therefore, the greater the scope of its spread, the greater the risk of fire, the greater the scope of the area designated on the scene. The method and procedure for setting a guard zone are as follows:
(1) Measuring gas diffusion range
After the disposal personnel arrives at the site of the leakage accident, the instrument shall be used to determine the explosive concentration limit of the liquefied petroleum gas leakage zone and the scope of the leakage of the liquefied petroleum gas leaked at the accident site, and the warning zone shall be determined accordingly. The value of the boundary concentration in the guard zone shall be based on 1/2 of the lower limit of the explosion concentration . When measuring, the pointer of the explosion tester is adjusted to 0.75% (the lower limit of the explosion concentration of LPG is 1.5%) . It is unsafe to exceed 0.75%, and it is safe to be less than 0.75% . Underground trenches, tunnels, basements, and low-lying areas should be carefully tested.
(2) Set warning signs
Measuring the alert range must be done at the same time as setting the alert sign. The personnel who arrive at the accident site in advance should master the wind direction, wind speed, topography, surrounding buildings, and the liquefied gas diffusion and flow range. In addition, signs such as “No Entry†and “Danger here†should be set at the boundary and pass point of the guard zone. Yellow and red flags can also be used instead. Signs should be prominent; there should be lights at night to facilitate pedestrian observation.
( 3) Establishment of alert posts
Relevant departments that arrived at the scene of the accident should cooperate closely to cut off all traffic leading to the warning area and set up fixed posts at all intersections. All non-related personnel are not allowed to enter the area. At the same time, there must be a mobile whistle and pay close attention to the personnel in the warning area. Action, and always pay attention to changes in the direction of the wind in order to take emergency measures.
2 Elimination of fire and evacuation of the masses
After the leakage of liquefied petroleum gas, in order to prevent the accident from expanding, it is necessary to take resolute and decisive measures to eliminate all fire types in the dangerous area and actively organize the people to evacuate to safe areas.
(1) Elimination of fire
Elimination of fires includes all open fires, electric fires, static sparks, and impact friction sparks. The specific methods of eliminating fire are as follows:
1 Send a danger alert and mobilize people to turn off. After the disposal personnel arrive at the scene, they should quickly identify the warning area and use the means of broadcasting to describe the people and mobilize the people to actively extinguish the fire. At the same time, it is also necessary to notify the production units in the hazardous areas to stop, stop the fire, and stop all operations that can generate sparks.
2 Turn off the power. After the accident, immediately notify the electric power department to cut off all power for production, living or public lighting in the hazardous area, and the power supply department must not supply power until it has received notification of cancellation of the alarm.
3 No vehicles are allowed to pass. After the accident, all motor vehicles in the vigilance area must stop and turn off immediately, and all types of motor vehicles, livestock vehicles and bicycles are prohibited from entering the warning area and must be parked or bypassed.
4 Control personnel carry fire. People who enter dangerous areas are not allowed to use loudspeakers and flashlights; they are not allowed to use common communication equipment; if they must use it, the equipment used must be explosion-proof; they must not carry iron; they must not wear nail shoes and chemical fiber fabrics; Randomly throw and kick stones to ensure that your actions are safe.
(2) Evacuation of the masses
After the disposal personnel arrive at the site, they must take effective measures to actively rescue and guide the people in the dangerous areas from escaping the dangerous areas and evacuation to safe areas.
1 Establish a safe area. It is necessary to establish a safe area in the direction of the higher ground, in order to allow the people to take refuge temporarily. The security area should set up broadcasting stations and safety signs to guide the people and make clear the direction of evacuation.
2 Determine the evacuation route. In order to prevent people from panicking and acting blindly in dangerous areas and causing chaos, evacuation routes should be established in advance so that after the evacuation of the danger zone, the people will arrive at the safe area in accordance with the prescribed route.
3 effective organization evacuation. In the process of evacuating the masses, we must organize the masses to help the old and the young, take care of the wounded and sick, and reassure the masses not to panic; mobilize the masses not to carry metal articles or nail shoes so that the evacuation of the masses is organized, orderly, safe and secure. get on.
3 Take measures to stop leaks
After the disposal personnel arrive at the accident site, they should find ways to stop further leakage so as to prevent the accident scope from expanding.
(1) Closed valve system leakage method
When liquefied petroleum gas (LPG) leaks due to the rupture of pipelines, the valve closing method should be adopted to stop the leakage. When closing the valve, the person should stand in the upwind direction and should preferably be operated by a skilled worker. The pliers used should have a protective layer to avoid the risk of metal sparks resulting from sparks.
(2) Water Injection System Leakage Method
If the liquefied petroleum gas leaks from the bottom of the tank, the waste water can be used to pressurize and fill the tank. Using the characteristics of the water being heavier than that of the liquefied petroleum gas, the liquefied petroleum gas floats above the leakage port to stop the gas leakage until the leakage. When the air is sprayed on the air outlet, repair the broken outlet. For frozen liquefied petroleum gas tanks, this cannot be used to stop leaks under any circumstances. Because the water will freeze in the tank.
(3) Frozen plugging method
Plugging method is to freeze when a leak of liquefied petroleum gas container is leaking cracks, cotton (linen) fabrics will crack and bandaged watering cloth (not with strong currents), by evaporation latent heat characteristics of LPG (liquefied petroleum The boiling point of the gas is -42 °C ) . The wet cloth and cracks are frozen to stop the leak and then processed one after the other.
(4) Cork plugging method
The cork plugging method is a method in which when the leakage is caused by the opening of the valve of the liquefied petroleum gas container from the root, the plugging device is quickly plugged with a cork plugging device. This approach is very dangerous, but when the valve is broken from the root, this method is only effective. For example, in 1983 , the storage and distribution station of Shenyang LPG Company stood in a railroad tanker and poured liquids into a storage tank. The tanker valve was accidentally broken from the root and the gas inside the tank was quickly sprayed. The station leader quickly organized personnel. Looking for a cork, setting a guard, and a fire-retardant source, and organizing strong measures to implement storms, it is imperative that a broken valve be blocked with a cork and effectively avoid a big explosion.
(5) Active ignition of leaking tanks
1 Ignition principle: In the disposal of liquefied petroleum gas leakage accidents, sometimes an “emergency risk aversion†action is taken in order to avoid greater danger and casualties, that is, active ignition measures are implemented. However, the gas diffusion on the site is relatively large, which can cause large-energy deflagration, resulting in a huge shock wave, resulting in unpredictable sites and igniting measures.
2 Ignition Preparation To actively ignite a leaking tank, you must be fully prepared. Including the covert personnel reaching the designated location, no high concentrations of mixed gas were detected in the surrounding area. Make long-type ignition rods, etc., and follow corrective measures.
3 Ignition timing: Active ignition of leaking storage tanks generally has the following two timings: First, the top opening of the tank leaks, and it is impossible to implement plugging. In case of a large number of leaked gases, the explosion may cause an explosion accident; second, the top of the tank has burst. The combustion is formed and the tank is protected by cooling. When the pressure in the tank is not too high, the flame is blown out by the wind or quenched by the cooling water. However, the gas diffuses out. If it does not relight, the diffusion gas can still cause damage. While continuing to cool the tank, it should be ignited decisively.
3 to disperse gas clouds and eliminate hidden dangers
At the same time as the plugging work is started and completed, it is necessary to dilute and disperse the liquefied petroleum gas cloud formed in the accident site to completely eliminate the fire hazards.
(1) Water spray method
Practice has proved that using a water jet gun to disperse liquefied petroleum gas clouds is an effective method. It can cause agitation of air and water vapor to convect, which serves to dilute the liquefied petroleum gas.
(2) Foam coverage
When liquefied petroleum gas flows into the ground along the surface, it is best to use medium multiple foam coverage to reduce its evaporation rate and narrow the scope of steam clouds. The key to using this method is to pay attention to the fact that when the water in the foam is in contact with the liquefied petroleum gas, the volatilization rate of the liquid liquefied petroleum gas may be increased due to the impact before the foam cover is formed. Using multiple foams can balance the two conflicting factors of moisture content and stability.
(3) Air Dispersion
For liquefied petroleum gas clouds that accumulate in buildings and trenches, open doors or trench cover plates must be used to blow dangerous gases through natural ventilation, and can also be driven by mechanical ventilation.
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