Analysis and preventive measures of jacket explosi

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Analysis of glass lined reaction tank jacket explosion accident and preventive measures

since a glass lined reaction tank in a chemical plant in a city was put into use in 2001, no abnormal phenomenon has occurred. At 9:00 a.m. on April 26, 2003, the operator of the plant pressed dichloromethane and 7-ACA into the oxidation tank, filled the jacket with ice salt water to cool down, pressed the ice salt water out of the jacket, and then added trimethylhexamide to the reaction tank. Half an hour later, Inject steam into the jacket of Dow's material products for high-end cars. At 10 a.m., just before closing the steam valve, the jacket of the glass lined reaction tank exploded

1 cause of accident

after the accident, the professionals of the municipal boiler and pressure vessel inspection institute who participated in the investigation carried out visits to relevant personnel, on-site investigation, wall thickness measurement and other work, and applied fracture analysis, chemical composition analysis, mechanical property test, metallographic analysis and other methods and means to draw a conclusion:

1.1 explosion caused by overpressure operation. The design pressure of the jacket of glass lined reaction tank is 0.59mpa, and the allowable operating pressure is 0.5MPa. During intermittent production and operation, the actual working pressure in the jacket changes with the alternate circulation of ice salt water and steam. The pressure of steam entering the jacket is completed by the amount of steam. There is no pressure relief device in front of the steam inlet valve in the original design. At the time of the accident, except for this reaction tank, other steam equipment in the whole workshop were stopped in succession. The steam pressure sent out by the steam main line was 0.8MPa, which was actually all supplied to the reaction tank. The operator failed to find and adjust the steam inlet valve in time. There was no pressure relief device in front of the valve, and there was no safety valve on the jacket. When the steam with a pressure of 0.8MPa directly entered the jacket, the pressure in the jacket suddenly increased to 0.8MPa, Thus, the jacket will operate under overpressure and explode

1.2 explosion caused by corrosion and thinning of the vessel wall. The jacket of the reaction tank is made of A3 steel. The reaction process is indirect cooling and heating through ice salt water and steam. It is used alternately. The ice salt water reacts with iron, causing corrosion of the tank body, thinning of wall thickness, and explosion during overpressure operation

2 preventive measures

2.1 replace corrosive cooling medium with non corrosive medium. The corrosive cooling medium used in the chemical industry is salt water. When adding salt, in order to change the freezing point of water, and the chloride ion is corrosive to the equipment, according to the current process conditions, it is difficult to change the process to normal temperature in a short time, and there is a certain technical resistance. So finding a non corrosive low-temperature medium to replace salt water has become one of the necessary means to solve problem 2. Record the required load value. At present, some enterprises use ethylene glycol instead of ice salt water, which also meets the process requirements and receives good results. Therefore, the impact testing machine is also the common impact testing machine used by Zui in the market at present, which we can learn from

2.2 adopt corrosion-resistant equipment. In view of the practical problem of long-term use of salt water as a medium for cooling in the chemical industry, developing corrosion-resistant special equipment to fill the gap of domestic corrosion-resistant chemical equipment is a problem that our equipment manufacturing department needs to solve. Therefore, a bridge should be built between process design and equipment manufacturing. The data in the process experiment should be fed back to the equipment manufacturing unit at any time, and the equipment manufacturing unit should also take technical means to meet the special requirements of the process as far as possible, and jointly carry out technical research on the mechanism of chloride ion corrosion in brine. On the one hand, some substances are added to reduce the corrosivity of chloride ions, on the other hand, special materials are used to produce special corrosion-resistant equipment. At present, we can use asi316l or titanium alloy in the material selection of manufacturing equipment. These two materials have strong corrosion resistance. Using them to replace A3 steel will achieve good results

2.3 strengthen safety management. At present, ice salt water is still used as the cooling medium and under the existing process conditions, in order to achieve safety production, strict management must be carried out in accordance with the relevant national regulations, and the following measures should be taken:

2.3.1 safety education should be carried out for employees, and the process discipline, labor discipline and safety operation procedures should be strictly enforced. Especially when the steam pressure is high, it is necessary to strengthen the heart and operate carefully to prevent accidents

2.3.2 in terms of steam source management, the steam inlet valve should be installed with a pressure reducing device

2.3.3 install a safety valve on the jacket body to prevent accidents caused by the sudden rise of steam pressure, and regularly check its wall thickness to check the corrosion

2.3.4 strictly implement the supervision regulation on safety technology of pressure vessels, regularly inspect the safety technical performance, calibrate the pressure gauge and safety valve on schedule, and establish and improve the equipment archives

2.3.5 the equipment management department, maintenance personnel and operators should carry out daily inspection, maintenance and repair of the glass lined reaction tank in use at any time. If abnormal conditions are found, corresponding measures should be taken immediately to properly handle them, so as to ensure the safe operation of the equipment and achieve safe production

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