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Litigation and prosecution of China's petroleum and chemical standards and quality in November (below) patriotic Jiangsu Province Special Inspection Institute Jiangyin Branch Jiangsu Jiangyin 214400 Xin Shang to analyze the study of a compressed air pipeline explosion. The causes of the explosion accidents were analyzed, and effective preventive measures were proposed. 1 Accident Overview A compressed air pipeline explosion occurred in a steel factory in Jiangyin City in 10 years. One accident was caused and one person was seriously injured. The direct economic loss exceeded 2 million yuan.
2 The main technical parameters of the equipment The air compressor is a reciprocating piston oil-lubricated compressor. The lubricating oil used is No. 220 compressor oil and compressed air outlet pressure. 8Mpa. Compressed air pipeline is not designed by the design unit. It is designed by engineers and technicians in the unit. The installation process has not been monitored. Material 20, size 1219mmX6mm, air tank design pressure 0.98Mpa, design temperature KXTC, material Q235B, nominal thickness 8mm. 3 Analysis of the cause of the explosion The picture after the explosion is as follows: the pipe after the explosion, the air storage tank after opening the manhole.
After the manhole is opened, the explosion of the air storage tank occurs on the pipeline between the production system after the air is compressed. The inner wall of the blasted pipe has obvious oil and carbon black, and the explosion pipeline has no obvious plastic deformation. After the manhole of the gas storage tank was opened, there was a lot of oil pollution. Before the explosion occurred, there was a phenomenon that the flange of the compressed air pipe valve was leaking and oil leakage, but it did not cause the use unit to pay attention.
According to the analysis, the piston and the cylinder are lubricated with mineral oil when the compressor is working, and it is a combustible material. The compressed air system does not have a compressed air degreasing and cooling device, so that the compressed gas contains a certain amount of lubricating oil. When the compressor is working, the lubricating oil and the high-temperature, high-pressure air are continuously compressed in the compressor, and an oxidative splitting reaction occurs. The reaction product is mixed with the metal grinding material in the compressor and the dust impurities in the inhaling gas to deposit deposits in the compressor exhaust valve and the pipe. The longer the time, the more carbon deposits. When there is more carbon deposit, the compressor exhaust valve may be inflexible or not tightly closed, causing the gas discharged from the compressor to recirculate and repeat compression, the temperature of the compressed gas rises rapidly, and the higher gas temperature intensifies the lubricating oil. Oxidative splitting reaction, the flash point of the lubricating oil drops. When the temperature of the compressed gas rises to the flash point of the lubricating oil, the lubricating oil accumulated in the pipe begins to burn and explode. Generally, when the carbon content of the carbon is up to 30%, the oxidative splitting product of the lubricating oil, the oil mist and the air form an explosive mixed gas, and an explosion accident occurs.
4 Main factors affecting the explosion of compressed air pipelines 4.1 Compressed air temperature After the air is compressed, the temperature is too high to be effectively controlled. If a certain limit is exceeded, a large amount of explosive mixture will be generated. If the conditions are met, it will result in explosion. This limit is a variable value that is related to the thickness of the deposit in the pipe.
4.2 Carbon deposit thickness If the exhaust gas temperature does not increase and the thickness of the carbon deposit increases continuously, it will reduce the auto-ignition temperature limit of the carbon and spontaneous combustion will occur. The thicker the coke, the lower the auto-ignition limit temperature; the thinner the coke, the higher the auto-ignition limit temperature. Generally, when the thickness of the carbon deposit is 1mm, the limit auto-ignition temperature is 160°C. 4.3 Lubricant quality In the operation of the air compressor, the unqualified oil is used, and the volatile oil is used for cleaning during the maintenance. When the air compressor is running, If a large amount of combustibles are volatilized, the operating temperature and other conditions may cause a combustion explosion.
5 Preventive measures U) Strictly control the exhaust temperature, equip the rear cooler, and reasonably select the cooling water quality, timely remove the fouling of the cooler pipe wall and the cylinder cooling water wall, and also control the temperature difference between the inlet and outlet of the cooling water is not more than Urc. A thermocouple is added to the exhaust line of the compressor outlet closest to the cylinder to detect the exhaust temperature. All test temperatures are connected to the instrument panel on the compressor site for display. When this value is exceeded, an audible and visual alarm will be given to remind the operator to deal with it in time.
Qualified compressor oil was tested at 215 °C. From the actual operating experience, the use of oil with too high flash point, due to its heavy fraction, high viscosity, and a lot of colloidal content, there are safety hazards. Generally, low-viscosity and deep-refined lubricating oils have low residual carbon values ​​and are not easy to deposit carbon during use. Compressor oil shall not be mixed with other lubricating oils. Record and count the fuel consumption per unit operating time of the air compressor. The lubricating oil should be properly and should not be excessive or insufficient. If the fuel consumption increases abnormally, stop the machine and check the air pressure. The sealing of the machine.
Gas line. Strict maintenance and repair operations are an important means of preventing compressor explosions. An accident investigation of an exhaust pipe explosion in an air compressor found that there was more carbon deposit in the exhaust system. The reason was that most of the coke was not removed during maintenance of the compressor. The carbon deposit on the exhaust valve causes the exhaust valve to be closed tightly, causing leakage and repeated compression, which increases the temperature of the exhaust gas, allowing the high-temperature compressed air to directly enter the gas storage tank. During the daily maintenance and overhaul of the compressor, it is especially important to remove the carbon deposits on the exhaust valve and clean the exhaust pipe (especially the bent pipe part) and the gas storage tank. According to the data, when the thickness of the carbon deposit is 1mm, the limit auto-ignition temperature is 160. When the thickness of the deposit is 2mm, the limit auto-ignition temperature is 150°C; when the carbon deposit thickness is 3mm, the limit auto-ignition temperature is 115°. C. Therefore, to ensure the safety of the air compressor, regular cleaning of carbon deposits is the key.
Prevents the inhalation of dust and a gas with hard particles. When a dusty and impurity air is washed into the cylinder, not only the cylinder mirror and the piston rod are worn, but also due to the high temperature in the cylinder, some impurities and oil mixture are easily adhered to the gas valve, the cylinder wall and the piston groove. Fouling. The spindle oil is usually immersed in the metal mesh filter. When the dirty air passes, the dust and impurities adhere to the wire mesh through the barrier of the filter and the adsorption of the oil. The cleaning filter was boiled with 1% 5% caustic soda solution.
6 Summary Compressors and compressed air pipelines are commonly used in many units, but many units do not pay attention to safety management and eventually lead to major safety accidents. By analyzing the causes of explosions in compressed air pipelines, only by paying attention to safety management and taking corrective measures can we effectively eliminate the hidden dangers of air compressor accidents and ensure safe production.
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