Seek accident cases related to large fuel oil storage tanks

Search online for the gasoline tank farm fire at the Nanjing Refinery in 1993. At that time, 187 fire trucks were deployed, but many of them could not approach due to the complex network of pipes in the tank area. In the end, it was the firefighters who risked their lives by climbing up the tank with foam hoses to pour foam into it. . . If that storage tank collapsed and triggered a chain reaction explosion, it’s likely that Nan Lian would no longer exist. 7.3 Nanjing Refinery "10.21" Explosion Accident Analysis 7.3.1 After the Accident At 3 o'clock on October 21, 1993, Huang Yonghua, an operator in the unleaded gasoline tank area of the semi-finished product workshop of the Oil Products Branch of the Jinling Petrochemical Company Refinery, opened the No. 310 10000 m. gasoline tank outlet valve by mistake when he opened the No. 310 10000 m. gasoline tank outlet valve for cycle blending, causing a leak in the No. 311 tank. Gasoline was poured into the No. 310 tank, which was full but the inlet valve was open. At nearly 6:00 p.m., the floating roof of No. 31O tank was broken. A large amount of gasoline came out, vaporized, diffused, and flowed. The oil vapor exploded and burned when it encountered a spark from the exhaust pipe of a walking tractor traveling on the road in the tank area. A fire broke out in the 10,000-ton oil tank. The top of the tank, the tank area, valves, ditch pipes, and the mountain forest were burned together by multiple fire points at the same time, with a burning area of 2343 square meters.* * m. Municipal Fire Brigade"11 9" After hearing the alarm, the dispatching room mobilized 99 fire trucks across the city to the fire scene. Jiangsu Province and sister provinces and cities such as Shanghai and Anhui successively dispatched 88 fire trucks for reinforcements. A total of 187 fire trucks from 12 cities in the three provinces and cities, and the military More than 6,000 police and civilians fought together to fight the fire dragon. The firefighting forces on scene implemented unified command, first cooled down the control, and launched a general attack in 15 hours. After 17 hours of fighting, the fire broke out at 11:15 a.m. the next day. The fire was extinguished separately, plus fighting the re-ignited fire on the ground and continuous cooling. The battle ended after 22 hours. Two people died on the scene (one of them was a migrant worker), and the direct economic loss was 389,600 yuan. 7.3.2 Analysis of the cause of the accident After the fire was extinguished, the fire supervision department basically came to a conclusive opinion after investigation and investigation. However, for such a fire, there are many questions that require clear scientific basis, such as what happened to the oil in No. 310 and 311 oil tanks What is the total loss of gasoline and oil in the explosion and combustion? How much is the total loss of gasoline and oil? How is the combustion amount distributed? Is the cause of the explosion whether it is the exhaust pipe of a walking tractor or the static electricity of the human body, etc. These questions were all found by an expert group organized by the Nanjing Municipal Safety Committee through investigation and demonstration, and scientific calculation and analysis to find accurate answers. . 7.3.2.1 Explosion fuel consumption and T * After the T-equivalent No. 310 oil tank overturned and spilled oil, the oil vapor diffused and mixed with air, causing an explosion when it encountered a fire source. Traces of F were obviously left in the explosion space and burning parts. After measurement, the explosion area of ​​the flammable mixed gas was 2343 * * m2; Although the terrain at the site is uneven and the height of the burn marks varies, the baozha can be estimated based on the burnt branches and leaves on the trees and the height of the burn marks on the hillsides and buildings. * The average height of gas diffusion is 5m; the volume of explosion space is 11718 * * m3. (1) Determination of gasoline vapor concentration. Since the lower limit of gasoline explosion concentration is 1.3%, the on-site concentration must be greater than 1.3%. According to on-site measurement, the average concentration of gasoline vapor during space explosion is 2.2%, because an operator came out of the operating room after noticing the situation and couldn't stand the smell of oil vapor after walking a few steps and fainted to the ground. It was found that the concentration of oil vapor that can cause coma is 2.2%. Of course, the diffusion concentration at each diffusion point is different. (2) Calculation of the amount of gasoline lost by explosion G=S•H•C•M/22.4×10-3 In the formula, G-the amount of gasoline lost by explosion, t S-the explosion area, m., take S=2343 * * m2; H—average height of explosion, m, take H=5m; C—average oil vapor concentration, %, take C=2.2%. M—average molecular weight of oil and gas; take M=96. According to the above formula, the space explosion loss of gasoline is 11.15t. (3) Calculation of space explosion equivalent The gasoline explosion energy is 10300kcal/kg, converted into T * T equivalent is equivalent to 96.737t. It can be seen that the total energy of this explosion is very large, but it is not a "point source" or an effective closed space, but a completely open space of 20,000m2. Therefore, no overpressure or shock wave is formed, and only slight damage is caused to the affected buildings. 7.3.2.2 The space explosion and large-area combustion of the overflow oil distribution tank area, the burning of No. 310 oil tank in the state of oil spillage on the top of the tank after the explosion in the tank area, and the fact that the oil level in No. 311 oil tank dropped after the fire shows that No. 310 and No. 311 oil tanks in the tank area exploded. The oil level in the front tank has undergone abnormal changes. Oil tank No. 310 was in a self-circulating state before the explosion, and the oil level should neither increase nor decrease; oil tank No. 311 was in a stationary state before the explosion, and the liquid level should not change, nor should it be in contact with any tank. However, after the fire, it was measured that the oil volume in tank No. 310 had increased to the point where the tank was full and burned and overflowed, and the oil level in tank No. 311 had dropped by 1.822m. Therefore, the balance, process of change, and reasons for the oil volume in the two tanks No. 310 and 311 are the key to uncovering the accident. The key to the mystery. After investigation, it was found that the delivery capacity of the circulating pump in Tank No. 310 was 35lm3/h, and the decrease in oil in Tank No. 31l was exactly the amount of oil pumped into Tank No. 310 between the start of the pump and the explosion. The liquid level in Tank No. 310 before the pump was operated was l 4·26m, the floating roof was exposed after the explosion, and the oil volume has increased. It means that the inlet valve of No. 310 tank was open before the accident, and the amount of oil entering No. 310 tank should be the decrease of No. 311 tank. The total material balance and distribution is: (1) Total burn loss: The original oil level of No. 31l oil tank was 13.972m. After the explosion, it was checked to be 12·15m, a decrease of 1.822m. The total loss was 855.588t. All this oil entered the No. 310 tank. In 31 After the No. O tank fire was extinguished, in order to repair the valve at the bottom of the tank, water was added to the tank and 78.984t of oil was pressed into the No. 304 tank at the same time. The net increase in oil volume retained in the No. 310 tank after the fire was 594.207t. From this, it can be concluded that the total amount of oil burned in the accident and lost was 182.394t. (2) Combustion volume of the 310 tank. When the No. 310 tank explodes and burns, the floating roof bulges, and the liquid level at the annular seal on the tank top is completely exposed to the air, forming a raging fire in an annular area of 17.78m. Calculate according to the following formula: G1=W•S1•h where G1—the amount of fuel on the top of the tank, t;, w—is the gasoline burning weight rate, taken as 80.85kg/m2·h; S1 is the annulus area at the top of the tank, m.; take 17.78m2; h is the burning time, h=17 h. Calculate G1=24.439t. At that time, the wind speed was 3m/s and the annular area with a height of 16m had sufficient oxygen supply to the inner and outer rings, so the burning speed would accelerate. In addition, with the overflowing fire curtain on the top of the tank, more oil was burned than the theoretical calculation. If doubled, the approximate amount of oil burned was 48.874t. Considering the leakage of the valve at the bottom of the tank at 1474kg per hour, the amount of oil burned was 25.064t, and the total combustion loss of the oil tank was 73.938t. (3) Tank area ground penetration and flood control open ditch burning volume 3l0 When the tank was ejected, part of the gasoline atomized and spread, part flowed to the ground, was absorbed by the ground, penetrated, and flowed to the flood control ditch along the terrain. The distance of the flow was about 480m and the area was 1160m. After the explosion, a fire broke out in the tank area and the open ditch continued to burn. It took about half an hour for the open ditch fire to go out. The ground in the tank area burned like a candle. Due to the fire resistance of the ground itself, the ground fire was quickly extinguished. The amount of oil lost by ground adsorption and open ditch burning is: G=Total amount of gasoline lost (the amount of fuel in the valves at the top and bottom of the tank + the amount of fuel in the space explosion) =182.394-(48.874+25.064+11.15) =97.306(t) The amount of oil burned in the open drainage ditch is: 80.85×1160×O.5 =46893kg (46.893t). The amount of ground adsorption and burning oil is: 97.306-46.893=50.412t. Therefore, the total loss of gasoline in the No. 310 oil tank fire is 182.394t. 7.3.2.3 Determining the ignition source: What energy (ignition source) ignited the combustible mixed gas after the No. 310 tank gasoline spread from the roof was also one of the difficult problems that the expert group had to demonstrate and determine. At that time, there were two possibilities for the fire source. One was sparks from the exhaust pipe of the walking tractor driven by Lu Guosheng on the road in the tank area, and the other was that it was caused by static electricity. After careful analysis and demonstration, the expert group agreed with the conclusion of "the exhaust pipe of the walking tractor detonated" determined by the fire department. (1) Possibility of static electricity detonation When gasoline overflows and spreads, analysis of the conditions for the generation of static electricity: a. Possibility of static electricity sparks generated by static electricity on the human body. Because the operator Teng Daoyue found that the oil tank had collapsed and ran to close the valve and walked about 300 meters, static electricity may be generated and reach the level of discharge; the friction of the wind speed on the tractor operator may also generate static electricity, and the person is in an insulated state, so the generated static electricity is not easily conducted away from the four tires. b. Other factors may produce static electricity. For example, when the gasoline tank is filled, the spray aerosol is charged, and the gasoline evaporates and is charged on the ground. However, after demonstration by the expert group, static electricity detonation was ruled out. This is because: the air humidity at that time was 70---75%, and the possibility of generating static electricity under such weather conditions was extremely small; a large amount of gasoline overflowed from the top of the tank, and the oil The concentration in the center of the tank was so high that the concentration would exceed the explosion limit where Teng Daoyue ran to close the valve. After the explosion, when his companions found Teng Daoyue, he was severely burned, his clothes were burned off, and his hair was singed, but he was still moving slowly and kept talking. Although he died on the way to the hospital, he was obviously not at the center of the explosion. (2) Identification of spark detonation in the exhaust pipe of a walking tractor a. It was identified that although the walking tractor driven by Lu Guosheng had a flame arrester, the exhaust pipe was blocked by carbon deposits and had lost its fire arresting effect. Sparks appeared at the initial speed of starting. b. A test was conducted on the same model of tractor. The unloaded tractor (the tractor in the explosion area was a heavy load) had carbon deposits removed from the flame arrester (the tractor in the explosion area had severe carbon deposits). After driving for 8 minutes, sparks clearly appeared in the flame arrester area. c. The road that Lu Guosheng drove the tractor happened to be a little inside the edge of the diffusion and volatilization of gasoline vapor, and the vapor concentration was at its best. d. According to the autopsies of tractor driver Lu Guosheng and operator Teng Daoyue, Teng Daoyue had 80% burn area, including 45% II burns and 30% III burns; Lu Guosheng's burn area reached 95%, including 55% mutual burns and 45% III burns. And Lu Guosheng The burn locations were obviously different. The left side of the face and neck was severely burned. There were several ground-breaking wounds on the chest, while the injuries on the back were obviously minor. This was due to the initial state and propagation direction of the combustible gas detonated by a spark from the tractor exhaust pipe in the front. 7.3.3 Identification of the cause of the accident Based on the above analysis, it can be determined that the cause of the accident is: around 15:00 that day, when the day shift operator was performing a pump circulation operation after adding additives to the 310 tank, he should have opened the outlet valve of the tank on the circulation line, but mistakenly opened the outlet valve of the 311 tank on the circulation line. After the oil extracted from the 311 tank entered the 310 tank, the computer continued to alarm, but never caused the operator to pay attention. The shift handover was not strict and detailed, and no accident was found. After the shift, the accident continued, causing the 310 tank to overflow, and gasoline vapor to spread over a large area in the tank area and outside the tank area. At around 18:15, the exhaust sparks of the walking tractor that drove into the deflagration area ignited the mixture of gasoline vapor and air that spread over a large area, and finally led to this major fire accident. The specific process of the accident is: (1) After the 311 tank is full of oil, the tank valve should be closed to seal the tank. However, it has become a common practice at this position not to close the tank valve to seal the tank. This resulted in the misoperation of opening the wrong valve on the circulation line, pumping the oil in the 311 tank into the 310 tank, causing the full tank to overflow. (2) The operators did not have a strong sense of responsibility and seriously violated operating disciplines. They were indifferent to the high liquid level alarm of the 310 tank. They neither reported nor carefully searched for the cause. It was too late to check when they smelled the smell of gasoline. (3) The operators did not attend the handover on site when the shift was over, and did not carefully check the operation process. They only handed over verbally, resulting in process errors that could not be discovered in time. (4) The post responsibility system such as the patrol inspection and tagging system is just a formality and in vain (the tags have been rusted and have not been listed for a long time). There is no one to inspect and supervise the implementation of the patrol inspection system. (5) There are no marks on the valves of the tank farm valve group, and the valve groups of several tanks are arranged side by side in a line, which can easily cause errors during operation. (6) The oil tank area is a first-class fire and explosion-proof area, and tractors and other motor vehicles should be prohibited from entering. However, the factory did not strictly manage the issuance of passes to motor vehicles from external units. The hand-held tractor driver actually drove the tractor across the road next to the oil tank area with an expired pass. The sparks from the exhaust gas directly led to the "10.21" fire accident. (7) The fire-fighting foam line of the oil tank was not designed according to the formal design, and the condition was not carefully checked since it was put into use in 1988. The bottom valve of the semi-fixed foam fire-extinguishing line of the oil tank was not installed (four valves were buried under the soil, and none of them were installed). It was not discovered for a long time. During the fire-fighting, the foam was short-circuited and ran away, which did not play the role that the fire-fighting line should play, delaying the opportunity to extinguish the fire. (8) The open drainage ditch in the fire dike out of the tank area was not equipped with gates or valves as required, causing the overflowing gasoline from the full tank to flow out of the dike. (9) The oil tank area lacked an overall design that complied with fire protection regulations, and the built gasoline tank area did not form an annular fire passage. As a result, ordinary fire trucks were unable to approach the fire source for effective fire fighting, which prolonged the time to put out the fire. Analysis of the cause of the accident 7.3.4 Lessons from the accident 7.3.4.1 The legal system must be strengthened to prevent accidents. Fundamentally speaking, this accident was caused by managers and operators not paying attention to safety laws and regulations for a long time. It was caused by the factory's ineffective rectification of fire hazards. According to the investigation by the fire department, the tank area where the No. 310 oil tank is located was built in 1965 and converted into gasoline tanks in 1982. During the implementation of the project, fire safety facilities were not inspected according to fire regulations. Roads, etc. were renovated, and fire prevention approval procedures were not completed as required. There were no fire escapes in the entire tank area, and fire embankments were not set up as required. In addition, fire protection facilities were insufficient, and most of the existing ones were damaged and could not function. What was particularly serious was the lax management of motor vehicles in the reservoir area, and motor vehicles without flame arresters could enter and exit at will. The fire was caused by a tractor without a flame arrester. Regarding these problems, the Nanjing Fire Department has issued major fire hazard notices many times, requiring it to make rectifications as soon as possible. It also issued notices twice on August 3 and September 17, 1993, and instructed it to report the rectification information to the Municipal Fire Prevention Committee before September 30, but the factory still did not pay attention to it. Due to the long-term neglect of fire safety in this factory, fire hazards have continued to occur in recent years. Just on June 30 last year, the platinum reforming workshop of this factory was operating illegally, causing a hydrogen tank to burn and explode, killing three people on the spot. However, this factory has not learned its lesson, resulting in the "10·21" fire that shocked the country. 7.3.4.2 To prevent accidents, we must strengthen people's management and education. This fire has gone through a series of links. As long as one link is blocked, it will not lead to such a big accident. However, the statistical results of Sinopec Corporation's statistics on the causes of accidents in the petrochemical industry show that due to technically unsolved problems Problems or accidents caused by unexpected and irresistible reasons are almost never encountered, but accidents often occur in management and discipline. It is understood that similar phenomena exist in other industries. In this way, the elimination and reduction of production accidents must start from all aspects of the production process. Use scientific methods, advanced management, systematic prevention, and do a good job in the basic work of essential safety in production. The emphasized approach is usually that enterprise safety management must strengthen leadership, conduct regular education on safety rules and regulations, implement safety funds, build on-site protection facilities, and strengthen safety inspections and concealment These were once effective methods and experiences in enterprise safety management. However, fundamentally speaking, these successes were the result of external forces. They did not properly unleash the potential of producers, the inheritors of management and discipline, and did not create a "disease-resistant" body group with regenerative capabilities. To eliminate and reduce production accidents, we must start from the main support body of production - people, strengthen the education and management of people, and transform administrative management into contract integration and natural pursuit to achieve the purpose of safe regeneration, which is also the fundamental way to reduce production accidents.