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Analysis of flash explosion accidents in atmospheric and vacuum units On September 12, 2003, Jinzhou Petrochemical Company’s 3 million tons/year atmospheric and vacuum unit was put into operation after maintenance, 17: At 10 minutes, when the decompression furnace was ignited, a flash explosion occurred. The accident resulted in serious consequences for 3 deaths, 1 serious injury, and 5 minor injuries. It also caused serious damage to the furnace wall and frame, and the entire decompression furnace was destroyed and scrapped. ； The direct economic loss of the accident was 450,000 yuan. 1. After the accident, on August 25, 2003, the 3 million tons/year atmospheric and vacuum unit began routine maintenance. September 11 8: At 00:00, the inspection is completed and the machine is ready for production start-up. September 11 8: 00:00 to 17:00: At 00:00, the device performs a purge and pressure test, 17: Stop the steam at 00:00, remove the blind plate of the oil inlet and outlet device, and prepare for the start of work. 20: At 00:00, the fuel oil and high-pressure gas blind plates are drawn out. September 12 8: 30 minutes of diesel cycle, dehydration test instrument ； 14: At 00:00 the heating furnace is ready for ignition. Stoker worker Lei Zhigang was assigned by workshop production director Li Zhongling to ask safety officer Cui Baoxian to contact the central laboratory to take samples and analyze the combustible gases in the atmospheric furnace and decompression furnace. The results showed that the analysis was qualified. 16: At 00:00, crude oil is circulated. 16: At 30 minutes, Li Zhongling, the production director of the workshop, arranged for the furnace workers Zhang Liqun, Lei Zhigang, and Wang Jian to prepare the furnace and conduct final inspections before starting the furnace. He also arranged for the squad leader Pan Jianzhong to lead people to put in the gas system and prepare for ignition. 16: After completing the ignition of the normal pressure furnace at 55 minutes, Wang Jian, the furnace stoker, went directly to the first floor platform of the decompression furnace to prepare for opening the valve. When Lei Zhigang entered the No. 9 burner of the decompression furnace at the bottom of the furnace, a flash explosion occurred in the decompression furnace. 2. Analysis of accident causes 1. Illegal command. September 12 14: At 00:00, the workshop production director did not understand the process, did not undergo on-site inspection, and mistakenly believed that the furnace gas system process was in place, so he assigned a safety officer to contact the central laboratory to sample and analyze the combustible gases in the normal pressure furnace and decompression furnace. In fact, the gas flow of the decompression furnace has not been laid out, the blind plate has not been removed, and the furnace is still in a state of maintenance. When the blind plate was not removed and the process was not set up, the laboratory was asked to take the furnace gas and analyze the combustible gas content in the furnace. The laboratory analysis results showed that the analysis was qualified. This analysis result was completely false. After taking the furnace gas sample, the workshop production director paradoxically assigned operators to smooth out the gas flow. Two hours and 40 minutes after sampling, the furnace is scheduled to be operated. According to regulations: Confirm that the burner valve is closed, the gas is introduced to the furnace and the blind plate is removed, and the sampling and analysis within 1 hour before ignition are valid. This operation exceeded the specified time and no one confirmed it. Wrong sampling results and illegal command laid the root of the accident. 2. Illegal operation. 16: 55 points. Guided by the wrong sampling results, we started to click on the atmospheric pressure furnace and the decompression furnace, 17: A flash explosion occurred when the decompression furnace was turned on at 10 minutes. Through on-site inspection after the accident: It was found that four valves in the gas system of the pressure reducing furnace were open to varying degrees, one DN80 valve and three DN50 valves. It was determined that the DN80 valve was a connecting valve between high-pressure gas and low-pressure gas. After the process transformation, the valve should be a normally closed valve and should be blinded with a blind plate. The three DN50 valves were low-pressure gas burner valves and were also normally closed valves after the process transformation. The openings of these four valves are 10% (6 buckles) for the DN80 connecting valve and 40% (7 buckles), 40% (7 buckles) and 50% (8 buckles) for the DN50 gas burner valve. According to the analysis of the on-site situation, the accident was caused by the fact that the boiler of the decompression furnace did not conduct careful and rigorous inspections during the preparation and inspection work before ignition of the decompression furnace, and did not find out that the high-pressure gas and low-pressure gas connecting valves and the three low-pressure gas burner valves were open, which caused the high-pressure gas gas to flow into the furnace through the low-pressure gas pipeline before ignition, resulting in a flash explosion during ignition. The operator did not follow the correct steps to close the low-pressure gas burner valve and the high- and low-pressure gas connecting valve of the pressure reducing furnace before ignition. The illegal operation was the direct cause of the accident. 3. There is no supervision in the work process. According to the requirements of the new version of the operating procedures, after the boiler has improved the gas flow and checked that there are no problems, he should open the baffles of the direct and incoming air preheaters, turn on the blower and induced draft fan to control the negative pressure in the furnace. After the steam is dehydrated, purge the furnace and burners, and close them after ten minutes. However, during the investigation after the accident, it was found that the induced draft fan of the pressure reducing furnace was not turned on, and the blower was not turned on. This important operation step was missed and there was no one to supervise it. As a result, the gas in the furnace was not evacuated in time, which was the main reason for the accident. 4. Blind board management has not been confirmed. During the accident investigation, it was found that there was no start-up blind plate table in the workshop's start-up plan. Instead, the blind plate was inserted according to the blind plate table in the shutdown plan. The person in charge of the blind plate is responsible for all the work of inserting and inserting the blind plate. After the person in charge of the blind plate pulled out the blind plate of the high and low pressure gas communication valve to burn it in the pressure reducing furnace on August 26, he forgot to restore the blind plate before starting work. According to the requirements of the line cleaning division table at the start of the workshop, a squad leader and a furnace worker were responsible for the high-pressure and low-pressure gas line cleaning, connection, and pressure testing. However, in the actual operation, the two men worked irresponsibly and carelessly. The line cleaning, connection, and pressure test were incomplete. They failed to find that the high- and low-pressure gas connecting valves were open. Without controlling the first few gates, the hidden dangers of the accident were unimpeded and turned into a catastrophic reality. First of all, the 9.12 accident was a fatal accident caused by serious violations of command and illegal operations. The operators were not serious and careful in their work, were careless and unskilled, and did not carefully check the gas flow before ignition. Secondly, steps were omitted and the induced draft fan and blower were not turned on as required by regulations. ； Before ignition, the valve switches of the process flow were not checked and confirmed, and the openings of the three low-pressure gas burner control valves and the high- and low-pressure gas connecting valves were not checked, allowing high-pressure gas to flow into the furnace, which was an illegal ignition operation. ； Third, the workshop did not effectively supervise and control the operating steps of the operators during the start-up process. ； Fourth, the workshop arranged the furnace sampling and analysis procedures incorrectly, failed to follow the procedures stipulated in the regulations, and failed to avoid accidents in time. Fifth, the workshop craftsman worked irresponsibly and missed inserting the blind plate. Therefore, this was a liability accident caused by a serious violation of regulations. 3. Treatment of those responsible for the accident The "9.12" accident was a liability accident. According to the safety production regulations and the group company's regulations on accident handling, we followed the principles of clear responsibilities and strict handling, and gave corresponding sanctions to a total of 21 people who were directly and indirectly responsible at all levels. Among them, 6 people were notified of criticism, 3 people were given administrative warnings, 4 people were given administrative demerits, 1 person was given a major administrative demerit, 1 person was administratively demoted, 2 people were administratively dismissed, and 4 people were expelled from the factory and kept on probation. 4. Accident Lessons The serious consequences of the "9.12" accident caused three deaths and six injuries, which had a serious negative impact on the company and caused huge trauma to the injured employees and their families. Three deaths and six injuries are a bloody lesson and a heavy price. We must learn profound lessons from the following six aspects. 1. The "people-oriented, safety first" thinking of leading cadres at all levels from the company to the workshop is not firmly established, safety awareness is not strong, work style is not solid, management methods are extensive, rules and regulations are not perfect, and the responsibility system is not implemented. “Although the 9.12 accident occurred in the workshop and was manifested at the operational level, its root cause lies in leadership. The essence is a management issue. The accident exposed the company and the production workshop's lack of strict organization and strict management of major production operations such as the start-up of major devices and the ignition of the decompression furnace. The responsibilities for the management of the start-up and shutdown of the installation were unclear, and the leading cadres were negligent in management. They even did not go to the site to supervise and check whether the safety precautions were implemented during operations such as the installation of the furnace. At this point, irresponsible leadership, careless employees, management full of loopholes, and a system that was in name only, ultimately led to this major accident. 2. Regarding the production and operation of the device, especially the start-up and shutdown operations, there is a lack of strict management and control in terms of system system, change operations, process discipline, employee behavior, on-site supervision, etc. “The 9.12 "accident occurred due to illegal command and out-of-control management, which exposed the lax operating discipline of the production workshop, imperfect rules and regulations, loopholes in implementation, and arbitrary reversal and change of work procedures, which led to the accident. The production safety responsibility system in the production workshop is not implemented. We also have relatively strict regulations on the process procedures, operating steps and safety precautions for the start-up and shutdown of the equipment. If the management and implementation are in place, the accident can be completely avoided. Because our safety production only stays on the slogans and does not implement them enough, we do not turn strict implementation of the rules and regulations into our own actions. There are lax and detailed system implementations in the work. Some safety production processes are artificially simplified and omitted in the implementation. There are rules and regulations and laws. This has developed into * habitual violation of rules and regulations * , safety management is gradually weakened. These are painful lessons learned by employees at the cost of their blood and lives. Especially in combination with the "four and one card" operating method currently implemented by the joint-stock company, and through comparative analysis of the old and new operating procedures, we have a deeper understanding of the root cause of the accident. In the "9.12" accident, we did not have the "four haves" of the "four haves and one card" operating method. Although there were instructions for sampling and analysis, the wrong instructions were equivalent to no instructions. ； Although there are procedures for lighting the furnace, they are very general, rough and inconvenient to implement. ； The stoker's operation to introduce gas and light the furnace was not confirmed ； There is no monitoring of the start-up process ； There are no operating procedure cards for employee post operations. “The 9.12 "accident reflected that we had no organizational, management, and personnel monitoring during the operation of the production equipment, and lacked operation confirmation links, resulting in uncontrolled production operations and burying major safety hazards in the production operations. 3. Change management is not in place. Change management includes instruction changes, process changes, equipment changes, and personnel changes. This time the installation was started, the production process was changed, and a high-pressure gas burner was added to the pressure reducing furnace fuel system. After the process change, the workshop lacked sufficient understanding, did not carefully organize employees to familiarize themselves with the start-up plan and process, did not explain the changes to operating employees, and did not organize employee training on the changes. Operations were made in advance at will, coupled with management confusion, resulting in operators not implementing the start-up plan according to process technical requirements and steps and operating at will. 4. The operating procedures are unscientific and not very operable. Article 3.3.1 of the original operating procedures stipulated the relevant requirements for the ignition of the heating furnace, such as "Comprehensive inspection of furnace tubes, hangings, return elbows, explosion-proof doors, burners, flue baffles, pressure gauges, thermocouples, valves, fans, preheaters, etc., and all valves are closed." The provisions are quite general ； Inaccurate location ； No concept of order ； No confirmation required ； Only employees who are familiar with the process can operate it. Those who are not familiar with it are prone to mistakes or carelessness and omissions. The operating steps are not detailed, the responsibilities are unclear, there is a lack of procedural and quantitative rules, and it is not clear how long after sampling the furnace must be lit. As a result, the prescribed actions are not clear, detailed, and in place, and the operability is not strong. 5. Staff operation training is not in place. “The "9.12" accident exposed serious problems in our on-the-job operational skills training, which failed to truly "learn what you do and know how to do it"” ； Failure to achieve 100% mastery of what should be known and understood. One of the two stokers assigned by the workshop to be responsible for lighting the furnaces scored 61 points and the other one scored 63 points in the induction examination, which just passed. This reflects that our training and assessment are not strict, resulting in unskilled operation and weak basic skills. 6. The start-up process is not properly managed. Carry out project finishing and cross-cutting operations while starting work. The ignition operating procedures for the start-up of the device clearly stipulate that personnel not related to the ignition operation should be promptly cleared and evacuated away from the site before ignition. However, during the ignition on September 12, the workshop did not conduct careful inspections according to regulations and organize the evacuation of irrelevant personnel. There were still three workers from the surviving company's engineering system performing maintenance and valve replacement operations on the decompression furnace. Three outsourced construction workers from the Shihua Engineering Team were performing civil construction work 15 meters away from the decompression furnace. As a result, when the decompression furnace flashed and exploded, one of the six people mentioned above died and five were injured, increasing the number of accidental casualties and expanding the story.