![]({{media url="Will_the_air_compressor_explode_The_cause_and_measures_of_air_compressor_explosion.jpg"}})
Will the air compressor explode
The air compressor will explode. However, air compressors are not easy to explode. The accident rate of the air storage tank of the piston type air compressor is very small. Only when the air pressure switch and the safety valve of the air compressor are broken at the same time will the air compressor have the possibility of explosion.
The air compressor is driven by the motor directly, which causes the crankshaft to rotate, and drives the connecting rod to reciprocate the piston, causing the cylinder volume to change. Due to the change in pressure in the cylinder, the air enters the cylinder through the air filter (muffler) through the intake valve. During the compression stroke, due to the reduction in the volume of the cylinder, the compressed air passes through the exhaust valve and passes through the exhaust pipe. The check valve (check valve) enters the air tank, and when the exhaust pressure reaches the rated pressure of 0.7MPa, it is automatically shut down by the pressure switch. When the pressure of the gas storage tank drops to 0.5-0.6MPa, the pressure switch is automatically connected and started.
The air compressor is to provide air source power and is the core equipment of the pneumatic system. The main body of the electromechanical air source device is the device that converts the mechanical energy of the original motion (usually an electric motor or diesel engine) into gas pressure energy. It is compression Air pressure generating device.
Three elements forming an air compressor explosion
![]({{media url="Will_the_air_compressor_explode_The_cause_and_measures_of_air_compressor_explosion2.jpg"}})
According to the working characteristics of the air compressor, the air is compressed by one or more levels to make compressed air. The cylinder block and piston need lubricating oil to inevitably generate carbon deposits, and air compression will greatly increase the temperature. The air contains oxygen, which forms the three elements of the air compressor explosion: coke, temperature, and air.
Coking
According to experiments, it is proved that the exothermic reaction of forming carbon deposits on the exhaust valve occurs at a temperature ranging from 154℃ to 250℃. The process is lubricating oil that is misty or sticks to the metal surface. Under high temperature and high pressure, especially under the condition of metal contact, it is quickly oxidized by air to form an oxidized polymer (colloid sludge, etc.), which is deposited on the metal surface In the above, continue to be heated, thermal decomposition dehydrogenation reaction occurs, and the formation of hydrogen deposits. There is a risk of spontaneous combustion when the thickness of the carbon deposit exceeds 3mm. In addition, carbon deposits affect its heat dissipation efficiency, accumulating heat to form a flash point. A part of the lubricating oil sticks to the fire point of the carbon deposit, and is evaporated and decomposed to produce cracked light carbonized hydrogen and free carbon. When mixed with high temperature and high pressure air, the explosion occurs when it reaches the explosion limit. Generally, the lubricating oil is decomposed by heat, and the explosion limit of light hydrocarbons that can be produced in the air is: CH4 5-15%, C2H6 3-12.5%, C3H8 2.1-9.35%, C3H6 2-11%, etc.
From this we can see that carbon deposits and local overheating are the main causes of the explosion, and the gas mixture of hydrocarbon gas and air is the main medium of the explosion.
The amount of carbon deposits is related to the oxidation stability of the lubricating oil, the amount of refueling, the quality of the lubricating oil and the maintenance.
Lubricating oil required for air compressor piston lubrication is made by adding various additives on the basis of refined base oil. The quality of the base oil directly affects the amount of residual carbon. The base oil (such as Lanzhou and Xinjiang) has good thermal oxidation stability, the residual carbon value is small, and the speed of lubricating oil to form carbon deposits is low, which is not easy to form a large amount of carbon deposits. , So it is important to choose the compressor oil.
The size of the oil filling device of the air compressor cylinder directly leads to the generation of carbon deposits, sludge, and oil and gas. For example, a 40m3 secondary compression air compressor, the standard stipulates that the primary cylinder is filled with 12 to 18 drops/min, the secondary cylinder 12 to 15 drops per oil. Exceeding this regulation, excess lubricating oil will be adsorbed on the depressions and pipeline walls, producing sludge and carbon deposits, and only a part will be discharged with the compressed gas.
Incorrect maintenance and poor cleaning effect are also the reasons for the large amount of accumulated carbon. According to the survey, the intermediate cooling tank, aftercooler and pipeline are the parts that are not easy to clean the carbon, and the amount of carbon deposits and sludge generally generated here is also large.
Temperature
The temperature increase of compressed gas is an important condition to promote the explosion. According to statistics, 50% of the air compressors exceed 170°C. Explosion occurs, so all countries stipulate that the exhaust temperature should not exceed 150°C.
If the intake air volume is reduced by 10%, the exhaust gas temperature will rise by 20℃. Therefore, the inlet must have sufficient intake air volume.
Exhaust valve carbon deposits cause valve leakage and can also cause exhaust gas to heat up. For example, the normal discharge temperature of a 700kPa compressor is 130°C, and a 270°C temperature will be generated when the valve leaks, which is prone to explosion accidents.
Insufficient water cooling and serious scaling will cause poor compressed air cooling, resulting in high temperature rise, which is very important.
Air
Because the compressed working medium is air, the air contains 20% oxygen. Oxygen will promote the oxidation and decomposition of lubricating oil, it is the basic element of combustion support and explosion.
Air compressor explosion-proof measures
In view of the above description of the three elements and causes of the reciprocating air compressor explosion, the following aspects of work can be strengthened.
Strengthen lubricant management
In order to control the formation rate of carbon deposits, the base oil should be selected with good residual carbon value; suitable viscosity (ISOVG68100); good thermal oxidation stability (Kang type residual carbon value-added "3%); lubricating oil with high ignition point. Such as: Lan Refinery produces LDAB air compressor oil. The oil supply of the cylinder should not be too large, and the maximum should not exceed 50g/m3, in order to prevent the increase of oil and gas and the increase of coking and coke. It is strictly forbidden to open the oil storage mode to prevent the oil machine from exceeding the standard to block the oil injector. In addition, the air compressor oil must have a product certificate and oil test sheet.
Strengthen equipment maintenance management
The status of each component of the air compressor should be verified regularly, and a complete large and medium repair plan should be formulated. The project should be specific and have acceptance criteria. Especially for regular charcoal cleaning work, there must be someone responsible for acceptance. The suction port should not be installed indoors, and ensure the prescribed suction volume, to prevent the air filter from clogging and reduce the intake air volume, resulting in an increase in exhaust temperature. Strengthen water cooling to ensure that the temperature difference between the inlet and outlet of the cooling tank is not higher than 10°C. Even in summer, the temperature of the outlet of the cooling tank must not exceed 50°C. Regularly remove the carbon deposits inside the compressor, generally check and clean the exhaust valve every 600h, and replace the exhaust valve every 4000h.
Strengthen operation management
Air compressors can be treated as a source of danger, so operators are required to hold certificates after training. The operator must be able to determine and deal with general air compressor failures while operating strictly in accordance with the operating regulations. The operator is required to have a clear understanding of the working principle of the air compressor, the cause of the explosion, reasonable oil injection, regular blowdown, and strict implementation of the on-off system.
Improve the monitoring ability of the operating state of the air compressor
On the basis of ensuring the basic safety facilities such as air compressor air cooling, temperature and pressure instrument display, safety valve, etc., an automatic temperature alarm should be installed at the connection of the outlet pipe of the exhaust valve, and the temperature should be strictly controlled not to exceed the specified 150℃.