Three elements that form an air compressor explosion
According to the working characteristics of the air compressor, the air is compressed by one or more stages to make compressed air. Cylinders and pistons need lubricating oil to inevitably generate carbon deposits, and air compression will greatly heat up. The air contains oxygen, which forms the three elements of an air compressor explosion: carbon deposition, temperature, and air.
charcoal
According to experiments, it has been proved that the exothermic reaction of coke formation on the exhaust valve occurs at a temperature ranging from 154°C to 250°C. The process is that the lubricating oil that is misty or sticking to the metal surface is rapidly oxidized by air under high temperature and high pressure, especially under the conditions of metal contact, to generate oxidized polymer (colloid sludge, etc.), which is deposited on the metal surface On top, continue to be heated, thermal decomposition and dehydrogenation reaction occurs, and hydrogen-based carbon deposits are formed. When the thickness of the carbon deposit exceeds 3mm, there is a danger of spontaneous combustion. In addition, carbon deposition affects its heat dissipation efficiency, accumulates heat and forms a fire point. Part of the lubricating oil sticks to the coke burning point, is evaporated and decomposed, and produces cracked light carbonized hydrogen and free carbon. When mixed with high temperature and high pressure air, it will explode when it reaches the explosion limit. Generally, when lubricating oil is decomposed by heat, the explosion limit of light hydrocarbon in the air: CH4 5-15%, C2H6 3-12.5%, C3H8 2.1-9.35%, C3H6 2-11%, etc.
It can be seen from this that coke deposition and local overheating are the main causes of explosions, and the mixture of hydrocarbon gas and air is the main medium of the explosion.
The amount of coke produced is related to the oxidation stability of the lubricating oil, the amount of lubricating oil, the quality of the lubricating oil and the maintenance.
The lubricating oil required for the piston lubrication of the air compressor is made by adding various additives on the basis of refined base oil. The quality of the base oil directly affects the amount of carbon residue. The base oil (such as Lanzhou and Xinjiang) has good thermal oxidation stability, and the carbon residue value is small. The rate of formation of carbon deposits in lubricating oil is low, and it is not easy to form a large amount of carbon deposits. , So it is very important to choose a good compressor oil.
The amount of oil added to the cylinder block oiler of an air compressor directly leads to the generation of carbon deposits, sludge, and oil and gas. For example, for a 40m3 two-stage compression air compressor, the standard stipulates that the first cylinder is injected 12 to 18 drops/min, and the second cylinder Oiling 12-15 drops/. If this requirement is exceeded, excess lubricating oil will be adsorbed on the depressions and pipe walls, generating sludge and carbon deposits, and only a part of it will be discharged with the compressed gas.
Delayed maintenance and poor charcoal removal are also the reasons for the large accumulation of carbon deposits. According to the survey, the intermediate cooling box, aftercooler and pipeline are the parts that are not easy to clean carbon. Generally, the amount of carbon deposits and sludge generated here is also relatively large.
temperature
The increase in the temperature of compressed gas is an important condition for the explosion. According to statistics, 50% of the air compressor explodes over 170℃. Therefore, all countries stipulate that the exhaust temperature should not exceed 150℃.
When the intake air volume is reduced by 10%, the exhaust gas temperature will rise by 20°C. Therefore, sufficient intake air volume is required at the inlet.
Carbon deposits on the exhaust valve cause valve leakage, which will also cause the exhaust to heat up. For example, the normal discharge temperature of a 700kPa compressor is 130°C, and when the valve leaks, it will produce a temperature of 270°C, which is prone to explosion accidents.
Insufficient water cooling capacity and serious scaling will cause poor cooling of the compressed air, leading to 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, which is the basic element for combustion and explosion.
Explosion-proof measures for air compressors
In view of the above description of the three elements and causes of the reciprocating air compressor explosion, the following aspects can be strengthened.
Strengthen lubricant management
In order to control the formation rate of coke deposits, a good base oil should be selected, with a small residual carbon value; a suitable viscosity (ISOVG68100); good thermal oxidation stability (Kang-style carbon residual value “3%); a lubricating oil with a high ignition point. For example, Lanlian produces LDAB air compressor oil. The fuel supply of the cylinder should not be too large, and the maximum should not exceed 50g/m3 to prevent the increase in the amount of oil and gas and the increase of coking and carbon deposits. It is strictly forbidden to open the oil storage method to prevent the lubricating oil machine from clogging the oil injector. In addition, the air compressor oil must have a product certificate and an oil product test report.
Strengthen equipment maintenance and management
The condition of each component of the air compressor should be verified regularly, a complete major and medium repair plan should be developed, the project should be specific, and there should be acceptance standards. Especially for regular charcoal cleaning work, a dedicated person is responsible for the inspection and acceptance. The suction port should not be located indoors, and the specified suction volume should be ensured to prevent the air filter from clogging and reducing the intake volume, causing the exhaust temperature to rise. Strengthen water cooling to ensure that the temperature difference between the inlet and outlet of the cooling tank is not higher than 10°C, and the water temperature at the outlet of the cooling tank shall not exceed 50°C even in summer. Regularly remove the carbon deposits inside the compressor, generally check the cleaning exhaust valve every 600h, and replace the exhaust valve every 4000h.
Strengthen operation management
Air compressors can be treated as dangerous sources, so operators are required to be trained and certified to work. Operators must be able to judge and deal with general air compressor failures while operating strictly in accordance with the operating procedures. Operators are required to have a clear understanding of the working principle of the air compressor, the cause of the explosion, reasonable oil injection, regular sewage discharge, and strict implementation of the startup and shutdown system.
Improve the ability to monitor the operating status of the air compressor
On the basis of ensuring the basic safety facilities such as air cooling of the air compressor, temperature and pressure instrument display, safety valve, etc., an automatic temperature alarm should be installed at the connection of the outlet pipeline of the exhaust valve to strictly control the temperature not to exceed the specified 150°C.