The basic criteria for selecting the air compressor is economy, reliability and security.

　   First: Consider the level of exhaust pressure and exhaust size. General purpose aerodynamic compressor discharge pressure of 0.7MPa, the old standard of 0. 8MPa. At present, there is a society with an exhaust pressure of 0.5MPa air compressor, from the point of view is unreasonable, because the pneumatic tools for its pressure margin is too small, the gas distance slightly longer can not be used. In addition, from the design point of view, this compressor is designed to a level of compression, pressure ratio is too large, easily lead to exhaust temperature is too high, resulting in carbon deposition of the cylinder, leading to accidents. If the compressor used by the user is greater than 0.8MPa, it should be specially made and can not be forced to pressurize to avoid accidents.

　　Displacement is one of the main parameters of the air compressor, air compressor to choose the amount of gas required to match and the displacement, leaving 10% margin. If the gas consumption is large and air compressor displacement is small, pneumatic tools, a start, will result in greatly reduced pressure on the compressor exhaust, but can not drive pneumatic tools. Of course, blind pursuit of large displacement is wrong, because the greater the displacement of the compressor with a larger motor, not only the high price, but also a waste of funds purchased, the use of electricity and energy will be wasted.

　　In addition, the election of the amount of displacement should also consider the peak amount and the amount of consumption and the amount of low. If the lower the amount of larger, and the amount of the peak and the amount is usually not large, the usual foreign approach is to have a smaller displacement of the air compressor in parallel to obtain a larger displacement, with the gas used to start one by one, so Not only beneficial to the grid, but also to save energy.

　　Second: Consider the use of gas and conditions. Such as the gas field is small (marine, car), should be elected vertical; such as gas occasions with long-distance changes (more than 500 meters), you should consider the mobile; if the occasion can not be powered, you should choose diesel-driven ; If there is no use of tap water, you must choose air-cooled.　

       In air-cooled, water-cooled two cooling methods, users often have a wrong understanding, that water is good, it is not. Small compressors at home and abroad in the air-cooled accounted for about 90%, this is because the design is simple and easy to use, no need to use water.

      The water-cooled compressor has four fatal flaws: There must be a complete water system, large investment; water-cooled cooler life is short; easy to freeze in the north winter cylinder damage; in normal operation will waste a lot of water.

　　Third: Consider the compressed air quality. Compressed air generated by the general air compressor contains a certain amount of lubricating oil, and a certain amount of water, in some cases is banned oil and water, then not only the compressor selection to pay attention to, if necessary, to increase the attachment.

　　Solutions: 1. Use non-lubricated compressor. This compressor cylinder is essentially free of oil, its piston rings and packing are typically polytetrafluoroethylene. However, this machine also has shortcomings, poor lubrication, high failure rate; PTFE is also a hazardous material, food, pharmaceutical industry can not be used; non-lubricated compressor can only do gas without oil, can not do without water.  

                       2. It's also commonly used method is to air compressor (no matter what) plus one or two purification device or dryer. This device allows the compressor air is neither oil nor water, the compressed air oil content of less than 5ppm, to meet the process requirements.

　    Fourth: Consider compressor safety. Air compressor is a kind of work machine with pressure, work with temperature rise and pressure, the safety of its operation should be placed in the first place. The state implements the standardized "two certificates" system for the production of compressors, namely compressor production license and pressure vessel production license (gas tank). Therefore, the purchase of compressor products, we must strictly review the "two cards." Usually there is a certified manufacturer's product quality assurance system is perfect, there will be no major quality problems, even if there are some problems, manufacturers will be responsible for three bags.

　　Air compressor purchase guide:

•  The pressure of the decision

　　1. The higher the pressure, the greater the power consumption. The pressure drop caused by the pipe size and length shall be taken into consideration, together with the pressure at the lower limit of the working pressure.

　　2. List the use of various models of the pressure, such as the use of pressure is too much difference, you have to purchase different pressure of the air compressor or the use of turbocharger, can not reduce the pressure to increase the cost of electricity.

• Model choices:

　　1.Calculate the total actual use of air volume plus margin is appropriate.

　　2. The actual displacement listed in the catalog of the company are all tested according to the American ASME wind measurement equipment.

　　3. Pay attention to energy ratio, in order to save electricity.

• The site:

　　1. To be a good place for good lighting, to facilitate the operation and maintenance.

　   2. Low temperature, low dust, clean air and well-ventilated place, the room temperature should be below 

          40 ° C.

•  Cooling water and water quality

　　1.  Cold water temperature should be low, with cooling towers to do the cooling.

　　2. It should be noted that the cooling of the PH value should be maintained at about 7 to prevent scaling, increase clean-up costs.

　3. Should pay attention to the cooling effect of the cooler, in general, compressed air outlet temperature should be about 40 ℃.

•  Compressed air quality and requirements:

　　Compressed air contains a large amount of water with a relative humidity of 100%, which causes great harm to precision instruments, pneumatic tools, pneumatic equipment, valves, instruments, pipes, etc., as water will cause corrosion, plug the instrument and reduce the finished product quality, Damage to the equipment and the loss of a lot of money to repair and maintenance work, so the installation of compressed air purification system is indeed necessary.