In daily life, especially in some industrial production process, compressed air becomes more and more important. Compressed air is made of electric air compressor. Based on the important role of compressed air, if the displacement of air compressor, especially some multistage and high-pressure compressors is insufficient, the storage of compressed air will be insufficient, which will seriously affect the normal industrial production. Moreover, since the compressor and its cooling water pump are driven by the motor, if the compressor displacement is insufficient, the energy consumption will increase. Therefore, we must find a way to increase and maintain the displacement of the air compressor as much as possible. As shown in the figure below, we can start from　Analyze this:

　　1. Air valve leakage

　　The air valve is a very important part of the suction and discharge pipeline of the air compressor. If the air valve leaks, it may cause a significant decrease in the displacement. The main reasons are as follows:

　　1.1 improper assembly of air valve

　　(1) The red copper gasket on the contact surface between the valve housing and the mounting hole must be annealed during the installation, and the compression degree must be appropriate, otherwise it will cause leakage of the air valve and insufficient displacement of the air compressor.

　　(2) Due to the different pressure of the air valves at all levels, the diameter of the spring steel wire and the thickness of the valve disc of the air valves at all levels are different, so the air valves at all levels can not be installed wrongly, otherwise the air valves will leak and the displacement of the air compressor will be insufficient.

　　1.2 air valve components damaged

　　(1) Because the speed of air compressor is very high, some of them are 22 revolutions per second or even higher, the suction valve and exhaust valve should be opened and closed 22 times per second or even more, and there is a certain pressure difference on both sides of the valve plate, so it is easy to cause the spring of the air valve to lose its elasticity and the valve plate to be broken, resulting in gas backflow, reducing the actual displacement of the air compressor.

　　(2) Even if the air valve is new, the air valve assembly may be defective. If the unqualified air valve is installed on the compressor, leakage will occur, which will cause gas backflow and reduce the actual displacement of the air compressor.

　　In the management and maintenance, the air valve shall be carefully inspected and assembled in strict accordance with the relevant technical regulations to ensure the displacement of the air compressor.

　　2. Failure of cylinder and piston

　　The cylinder and piston are the main parts of manufacturing compressed air, and their matching requirements are very strict. If the cylinder and piston fail, resulting in gas leakage, it will also lead to the reduction of the displacement of the compressor.

　　2.1 serious abrasion of cylinder mirror

　　The cylinder is affected by the side thrust of the piston connecting rod assembly, resulting in uneven wear and ovality of the cylinder, increasing the clearance between the piston and the cylinder, and increasing the possibility of leakage. At the same time, because the exhaust temperature of each stage of the cylinder is very high, if the cooling and lubrication effect is not good, it is easy to cause the carbon deposit of the lubricating oil, resulting in the abrasion or roughening of the cylinder surface, making the gas leak and reducing the displacement of the air compressor.

　　2.2 clearance increase

　　With the increase of the working time of the compressor, the volume efficiency will decrease with the increase of the clearance volume due to the mechanical wear and other reasons. However, since the stroke volume of the pistons at all levels and the volume of the pipelines and coolers between all levels remain unchanged, each level will be caused

　　The suction capacity will be reduced, and the displacement of the air compressor will be reduced.

　　2.3 failure of piston ring

　　When the piston ring works under high temperature and high pressure, the lubrication condition is poor, which makes the outer surface of the piston ring wear faster, the width of the ring decreases, the elasticity weakens, the gap between the opening and the piston and the cylinder wall increases, and the air leakage increases. It will reduce the suction capacity of the lower level and reduce the displacement of the air compressor. In the management and maintenance, the compressed air and cylinder shall be kept well cooled, the cylinder, piston and piston shall be kept well lubricated, the clearance volume shall be adjusted within the specified range in time, and the damaged piston ring shall be replaced in time to ensure the displacement of air compressor.

　　3. Leakage of sealing part

　　The working pressure of the air compressor is very high, so the sealing requirements of each connecting part are also very high. If the sealing of each connecting part is poor, it is bound to cause leakage and reduce the displacement of the compressor, mainly due to:

　　3.1 parts out of tolerance

　　The clearance fit between piston and cylinder is very close. If the clearance fit between the two exceeds the tolerance range, the gas leakage will increase and the displacement of compressor will be reduced. For example, the fourth stage piston has no piston ring, but has a curved neck groove on the piston. When it is seriously worn, the clearance between the piston and the cylinder is too large, and the fourth stage compressed gas leaks into the first stage, reducing the displacement of the air compressor.

　　3.2 improper assembly

　　It is mainly between the cylinder bodies and cylinder heads at all levels. Due to the uneven and improper tightening of nuts during the assembly, air leakage occurs and the displacement of the air compressor is reduced. Improper fitting of seals during the installation will also cause air leakage and reduce the displacement of the compressor. During the management and maintenance, the fit clearance shall be measured in time, and the four-stage piston shall be replaced if necessary; during the installation, the nuts between the cylinder blocks and cylinder heads at all levels shall be tightened diagonally; the seals shall be assembled in strict accordance with the relevant technical regulations to eliminate the leakage and ensure the displacement of the air compressor.

　　4. Suction blocked

　　When the outside air is sucked into the cylinder, it passes through the suction filter screen, suction pipe and suction valve, and is subject to resistance. When the suction stops, the air pressure in the cylinder will be lower than the atmospheric pressure, which will reduce the weight of the air actually sucked in in the cylinder, reduce the suction capacity of the compressor, and cause the compressor to reduce the exhaust volume due to the loss of suction pressure. In the management and maintenance, pay attention to cleaning the suction filter screen to prevent the suction valve from jamming, and select the air valve spring with appropriate elasticity to ensure the displacement of the air compressor.

　　5. Effect of suction temperature

　　According to the first law of thermodynamics of the state equation p1V1 / T1 = P2V2 / T2 of ideal gas, under the same compression condition, the suction temperature of compressor is affected to a great extent