Answer: (1) The basic criteria for selecting an air compressor are economy, reliability and safety.
(2) When selecting an air compressor, pay attention to the following issues:
1) Consider the exhaust pressure and exhaust volume. The general air pressure is 0.7MPa. At present, there is an air compressor with an exhaust pressure of 0.5MPa in the society, which is unreasonable from the perspective of use, because its pressure margin is too small for pneumatic tools, and it cannot be used if the air transmission distance is a little longer. If the compressor used by the user is greater than 0.8MPa, it generally needs to be specially manufactured, and forced pressure cannot be used to avoid accidents.
2) Exhaust volume is one of the main parameters of the air compressor. The air volume of the selected air compressor should match the required exhaust volume, and leave about 10% margin. If the air consumption is large and the air compressor exhaust volume is small, once the pneumatic tool is turned on, the exhaust pressure of the air compressor will be greatly reduced, and the pneumatic tool cannot be driven. Of course, it is wrong to blindly pursue large displacement, because the larger the displacement, the larger the motor of the compressor, which is not only expensive, but also wastes purchase funds, and also wastes electricity when used.
3) When selecting the displacement, you should also consider the peak usage, normal usage and valley usage. If the valley usage is large, but the normal usage and peak usage are not large, the common method abroad is to connect air compressors with smaller displacement in parallel to obtain a larger displacement, and start them one by one as the gas usage increases. This is not only good for the power grid, but also saves energy.
4) Consider the gas usage occasions and conditions. If the gas usage site is small (for ships and cars), a vertical type should be selected; if the gas usage site has long-distance changes (more than 500m), a mobile type should be considered; if the usage site cannot be powered, a diesel engine drive type should be selected; if there is no running water in the usage site, an air-cooled type must be selected.
5) In the two cooling methods of air cooling and water cooling, each has its own usage characteristics. Air-cooled compressors account for more than 90% of small compressors at home and abroad. This is because air cooling is simple in design and does not require a water source when used. The disadvantages of water-cooled compressors are: ① A complete water system must be available, which requires a large investment; ② The life of the water-cooled cooler is short; ③ The cylinder is easily frozen in winter in the north; ④ A large amount of water is wasted in normal operation.
6) Consider the quality of compressed air. Generally, the compressed air produced by air compressors contains a certain amount of lubricating oil and a certain amount of water. In some occasions, oil and water are prohibited. At this time, not only should attention be paid to the selection of air compressors, but also auxiliary devices should be added if necessary.
7) Consider the safety of air compressor operation. An air compressor is a machine that works under pressure. When working, it is accompanied by temperature rise and pressure. The safety of its operation should be given priority. The state implements a standardized "two-certificate" system for the production of air compressors, namely, air compressor production license and pressure vessel production license (gas storage tank). Therefore, when purchasing air compressor products, the "two certificates" should be strictly examined.
