Plugging of LPG leakage accident

2022-05-18
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Plugging of LPG leakage accident

Abstract: combined with the experience and lessons of several LPG leakage accidents, this paper analyzes the significance of plugging in LPG leakage accidents, and introduces the preparation before plugging, various methods of plugging, the protection and logistics support of plugging personnel for discussion

key words: liquefied petroleum gas; leak; Leakage stoppage

LPG leakage accidents have occurred many times throughout the country, and some even form vicious explosion accidents, resulting in many casualties and huge property losses. Liquefied gas leakage accident has always been regarded as a major difficulty in emergency rescue, but its development has laws to follow. As long as the rescue personnel master its characteristics and laws and use the correct plugging methods, they can not only achieve the success of rescue, but also avoid and reduce casualties

The typical development process of LPG leakage accident is leakage, gas deflagration, stable combustion, tank explosion and chain explosion. Liquefied gas leakage accident develops rapidly and cruelly. After the leakage of liquefied gas, it will volatilize and diffuse rapidly and mix with air to form explosive gas mixture, which may explode in case of Mars at any time. After the explosion, the high-temperature flame causes the temperature and pressure of the storage tank to rise rapidly, resulting in the explosion of the storage tank. The power of tank explosion far exceeds that of gas explosion. The high temperature, shock wave and explosion debris produced by it cause damage to rescue personnel and seriously destroy other tanks, resulting in chain explosion. However, blocking the leakage can control the development of dangerous situation

when plugging, the rescue personnel are surrounded by flammable gas and may be injured by Mars explosion at any time

2. Preparation before plugging

2.1 determine the parking position and spring fatigue testing machine according to the gas diffusion. It is a kind of precise experimental equipment in the laboratory. The attack direction

the volatilization and diffusion of LPG follows a certain law. After leakage, liquefied gas will quickly volatilize into gas, and its density is 1.5 to 2 times that of air. The gas will diffuse along the ground and gather on the ground surface and low-lying areas, which is not easy to diffuse. The gas concentration gradually decreases outward from the leakage center. The gas concentration in the close area is higher than the upper limit of explosion concentration, which is a high concentration area; The gas concentration in a slightly distant area is within the range of explosion concentration, which is an explosion risk area; The outward gas concentration is lower than the lower limit of explosion concentration, which is a low concentration area. If Mars appears in the explosion risk area or high concentration area, the gas in the explosion risk area will explode, and the gas in the high concentration area will burn and consume rapidly. In this short process, the gas temperature in the high concentration area and explosion risk area will soar, the volume will expand instantaneously, and the harm range is larger than the original high concentration area and explosion risk area. It is an injury area, and personnel will be injured in this area; Outside the injury area is the safety area. As can be seen from Figure 1, the injury area includes high concentration area, explosion risk area and some low concentration areas. The diffusion of gas is affected by the leakage. If the leakage is large, the diffusion range is large. On December 18, 1979, the spherical tank of the liquefied gas station of Jilin gas company broke, and the gas diffused to 250m within a few minutes, and exploded in the presence of open fire. On December 29, 1986, when a liquefied gas train tanker arrived at Hengyang station, the safety valve of a tanker jumped, and the gas diffusion range was only 50 meters

the diffusion of gas is also affected by wind and terrain. The site of leakage accident often has wind or uneven terrain. The diffusion speed of gas in the downwind direction and low terrain direction is significantly faster than that in other directions, forming irregular high concentration area, explosion risk area and injury area

the fire truck should be parked in the upwind, crosswind of the leakage point or at a place far away from the leakage point in the direction of high terrain, and the front of the truck should be outward to prevent the parking point of the fire truck from being adjusted quickly when the wind direction changes. When the engine belt of the fire truck runs at high speed, it will produce thousands of volts of electrostatic voltage, and its discharge energy is enough to ignite liquefied gas. Many electrical equipment of the car are not explosion-proof appliances, so the fire truck must be arranged outside the explosion risk area. For example, on July 17, 2000, in he6, Meihekou City, Jilin Province, the impact height was set according to the experimental requirements. In case of a leakage accident in Chengcheng liquefied gas station, the firefighters arranged the fire truck in the upwind direction and crosswind direction 150 meters away from the tank farm, and dispersed and diluted the gas through long-distance water supply through the water belt, so as to ensure the safety of personnel and equipment

emergency rescue should choose to approach the leakage point from the upwind direction of the leakage point and the direction with higher terrain. In this direction, the radius of explosion danger area and injury area is small, while the radius of explosion danger area and injury area is large in the downwind direction and low-lying direction. Therefore, it is easier to approach the leakage point from the upwind direction and high-lying direction for reconnaissance and plugging

2.2 delimit the warning area according to the gas diffusion

for emergency rescue, the explosion risk area and injury area are of great significance. All fire sources shall be prohibited within the explosion risk area to prevent gas deflagration. Except for the rescue personnel with effective protection, other rescue personnel shall be arranged outside the injury area. In the actual rescue, it is generally to delimit a warning area including explosion danger area and injury area, and consider the safety factor. Combustible gas concentration tester can be used to test the gas concentration in all directions around the leakage site. The warning area is within the range of concentration greater than 1%. Since the density of gaseous petroleum gas is higher than that of air, the tester shall be arranged close to the surface. As the gas diffusion is constantly changing due to the influence of leakage, wind and other conditions, the warning range shall be adjusted at any time according to the measured value

all ignition sources shall be prohibited in the warning area. The ignition energy of liquefied petroleum gas is only 0.175 to 0.38mj. Communication equipment such as and radio, publicity equipment such as camera and camera, lighting equipment such as flashlight, searchlight, fire truck, wrench and other rescue equipment commonly used in ordinary fire sites are potential fire sources and cannot enter the warning area. The tools used to enter the warning area must be non sparking tools, and the electrical appliances must be explosion-proof electrical appliances. The surface of ordinary iron tools is coated with paraffin to prevent sparks. The exposed metal parts such as hose interface are bound with adhesive tape to prevent sparks from colliding with cement floor or other metals when the hose is dragged. The parts where sparks may occur due to collision between metals during rescue operation can be targeted with a water gun to prevent sparks

2.3 deployed the water gun position to disperse the gas

. After delimiting the warning range and selecting the attack direction, it should organize the powerful water gun echelons from the periphery as soon as possible, and use the water driven smoke exhauster and spray water gun to disperse the LPG fog in the air. The water

deposition gas, and the whole step will be progressively pushed forward, and the gas will be dispersed in the downward direction of wind and the lower direction of the earth artificially, so that the reconnaissance personnel can be easily dispersed. The plugging personnel shall approach the leakage source for reconnaissance or plugging

2.4 choose the time of leakage stoppage

in the process of rescue and rescue, the leakage stoppage operation must be carried out in the daytime to avoid lighting lamps and switches from igniting liquefied gas

it will benefit from the internal technical and engineering synergy of Volvo cars and the resulting significant economies of scope

3. Select the appropriate plugging method according to the leakage

the rescue personnel should find out the specific situation of the leakage by asking the gas station staff, on-site inspection and other methods, so as to prepare for plugging. The matters that rescue personnel should find out include: whether the system is leaking air or liquid, whether the leakage is pipeline or storage tank, and whether the shape of the leakage point is round hole, ring, strip or irregular shape

3.1 plugging in case of gas leakage and liquid leakage

the risk of gas leakage is less than that of liquid leakage. When the LPG system leaks, the liquefied gas gasifies and absorbs heat in the system, which reduces the temperature and pressure in the system, which is conducive to plugging and rescue operations. In case of liquid leakage,

liquefied gas vaporizes and absorbs heat outside the system, and the pressure and temperature in the system do not drop. In addition, if the liquid is sprayed on the skin of the rescue personnel, it will also cause personnel frostbite, which is not conducive to the plugging operation

how to judge whether the LPG system is leaking gas or liquid? In case of air leakage, white fog will not be formed because the petroleum gas will no longer absorb heat from the air; During liquid leakage, due to the vaporization and heat absorption of the leaked liquid outside the tank, the ambient temperature drops rapidly, and the water in the air solidifies to form a vast white mist. At the same time, ice will appear at the leakage point

the methods of plugging in case of gas leakage and liquid leakage are also different. The freezing method can be used to plug the leakage in case of liquid leakage, but not in case of gas leakage. The freezing method is to wrap a certain thickness of bandage around the leakage, which can be reinforced with copper wire, and then water to soak the bandage. The leaked liquid gasifies and absorbs heat to cool and freeze the soaked bandage, so as to achieve the purpose of stopping leakage

after the leakage stops, the temperature of the bandage will rise gradually, especially in summer or under the sun, which will destroy the ice and leak again. In order to prevent the rise of temperature and the damage of ice layer, cotton quilt can be used to cover and fix it, which can block the sun and maintain local low temperature. For example, on March 8, 2000, a liquefied gas tanker in daimagou section of Heilongjiang Province overturned and leaked liquid, and the rescue personnel used the freezing method to stop the leakage. However, at noon on March 10, the temperature rose, and there was a risk of loosening at the frozen place. The rescue personnel covered it with cotton quilt to block the sun, maintained the low temperature at the frozen place and eliminated the danger

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