Points to consider when selecting a compressor

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The basic criteria for selecting a air compressor are cost-effectiveness, reliability, and safety. 　 First, the level of exhaust pressure and the volume of exhaust gas should be taken into consideration. The exhaust pressure of general-purpose aerodynamic compressors is 0.7 MPa, while the old standard was 0.8 MPa. Currently, there are air compressors on the market with an exhaust pressure of 0.5 MPa, which is unreasonable from a practical standpoint, as this pressure level provides too little headroom for pneumatic tools; they cannot be used when the distance over which air needs to be delivered is any significant. Furthermore, from a design perspective, this compressor is designed for single-stage compression; the high pressure ratio can lead to excessively high exhaust temperatures, resulting in carbon buildup in the cylinders and potentially causing accidents. If the compressor used by the user has a pressure greater than 0.8 MPa, it generally needs to be specially manufactured; forced pressure increase should not be employed to avoid accidents. 　 Displacement is one of the key parameters of an air compressor. When selecting an air compressor, its displacement should match the required output volume, with a 10% margin added. If the air consumption is high while the compressor’s output volume is low, starting the pneumatic tools will result in a **decrease in the compressor’s exhaust pressure**, preventing the tools from being powered. Of course, it is also wrong to blindly pursue a large displacement, as a larger displacement means a larger motor for the compressor, which not only results in higher costs but also represents a waste of money spent on purchase; moreover, it wastes electrical energy during use. 　　 Additionally, when selecting the exhaust volume, peak usage, normal usage, and low-usage periods must also be taken into account. If the demand during low-usage periods is high, while the normal and peak usage levels are low, a common practice abroad is to use air compressors with smaller displacement connected in parallel to achieve a higher total discharge volume; these compressors are turned on one by one as the demand increases. This approach not only benefits the power grid but also helps save energy. Second, the gas usage scenario and conditions need to be considered. If the space where gas is used is limited (for ships or vehicles), a vertical type should be chosen ； If there are long distances involved in the gas usage area (over 500 meters), then a mobile unit should be considered ； If the installation site does not have power supply, a diesel engine-driven model should be chosen ； If there is no tap water at the place of use, an air-cooled type must be chosen. Regarding the two cooling methods of air cooling and water cooling, users often have a misconception that water cooling is better, but this is not the case. In small compressors both at home and abroad, air-cooled types account for over 90% of the total, as they are simple to design and do not require a water source for operation. The fatal disadvantages of water-cooled compressors are four: a complete water supply and drainage system is required, and the investment is high ； Water-cooled coolers have a short lifespan ； In the north, cylinders are prone to damage from freezing in winter ； A large amount of water is wasted during normal operation. 　 Third, it is necessary to consider compressing air quality. Compressed air produced by ordinary air compressors generally contains a certain amount of lubricating oil as well as water. In some applications, the presence of oil and water is not allowed; in such cases, it is necessary to pay attention to the selection of the compressor, and additional devices may be required when needed. Solution: One is to use a lubrication-free compressor. Such compressors’ cylinders essentially contain no oil, and their piston rings and gaskets are generally made of polytetrafluoroethylene. But this type of machine also has disadvantages: poor lubrication and a high failure rate ； Polytetrafluoroethylene is also a harmful substance and cannot be used in the food and pharmaceutical industries ； Lubrication-free compressors can only ensure that the gas delivered is free of oil, but not free of water. The second, and also commonly used, method is to add one or two more purification units or dryers to the air compressor (of any type). This device ensures that the air supplied to the compressor is free of both oil and water, keeping the oil and water content in the compressed air below 5 ppm, thus meeting the requirements of the process. 　 Fourth, the safety of compressor operation must be considered. An air compressor is a machine that operates under pressure, generating heat and pressure during operation; its safety must be given top priority. **A standardized \"two-certification\" system is implemented for compressor production, namely the compressor production license and the pressure vessel production license (gas storage tank). Therefore, when purchasing compressor products, it is necessary to carefully examine the “two certificates”. Generally, reputable manufacturers have sound quality assurance systems, so major quality issues do not arise. Even if some problems occur, the manufacturer is responsible for providing warranty services.