Air compressor trading knowledge

General-purpose air compressors are regulated by national standards and the discharge pressure is 0.7 MPa. If it is higher or lower than this pressure, it is a non-standard special air compressor.

The following are the main types of air compressors: According to the volume of gas (refers to the volume of the discharged gas per minute when the air compressor is working, it is converted into the volume of the inhaled state). There is a small machine (discharge is less than 10 m3/min) Medium-sized aircraft (with displacement of 10 to 100 m3/min) and main engines (with displacement of 100 m3/min or more).

According to the structure type, there are rotary, piston and membrane air compressors. Common piston type and rotary type, screw type, sliding type. Screw rotor air compressors have complex rotor profiles and high manufacturing costs, but they are small, lightweight, and small parts. In the case of the same displacement, screw-type air compressors are much more expensive than piston air compressors, and maintenance personnel must also have specialized knowledge and experience.

According to the cylinder center line and relative position can be divided into vertical, horizontal, angle type air compressor. Among them, the angle type is divided into V type, W type, L type and so on. In general, because the piston air compressor is a reciprocating machine, there is a certain degree of vibration. The angle type can well balance its inertial force. Therefore, most of the small and medium-sized piston air compressors are made into an angle type, and only the air compressor for vehicles and boats is established because of the limitation of the floor space. Horizontal air compressors are the initial products and, due to their lack of superiority, are almost never produced. According to the cooler mode, it can be divided into water-cooled and air-cooled air compressors. The water-cooled type uses tap water open circulation cooling; the air-cooled type is fan cooling.

According to the different engine can be divided into motor drive and diesel engine air compressor. The large electric type is equipped with a distribution cabinet, and the diesel-driven type is started by a battery. Both types of air compressors have a direct connection and a side connection (ie belt drive).

Lubrication can be divided into oil-free and oil-lubricated air compressors. The latter is divided into splash-type and forced-type (ie, oil pumps and lubricators are oil-lubricated).

According to the basic configuration of the wide generation of air compressors can be divided into fixed (basic, no foundation) and mobile air compressors.

The basic criteria for choosing an air compressor are economy, reliability and safety.

One is to consider the level of exhaust pressure and the size of the exhaust. The general purpose aerodynamic air compressor exhaust pressure is 0.7 MPa, the old standard is 0.8 MPa. At present, there is an air compressor with an exhaust pressure of 0.5 MPa in the society, which is irrational from the perspective of use because of the wind In terms of tools, the pressure margin is too small. If the gas transmission distance is a little longer, it cannot be used. In addition, from the design point of view, this type of air compressor is designed to be one-stage compression with a large pressure ratio, which can easily cause the exhaust gas temperature to be too high, causing the cylinder to deposit carbon and cause accidents. If the air compressor used by the user is larger than 0.8 MPa, it must be specially manufactured. It is not possible to use forced air pressure to avoid accidents.

The displacement is one of the main parameters of the air compressor. The air volume of the selected air compressor must be matched with the required exhaust gas volume, and a 10% margin is left. If the gas volume is large and the air compressor discharge volume is small, the pneumatic tool will start to move, which will cause the air compressor discharge pressure to be greatly reduced, and it cannot drive the pneumatic tool. Of course, blindly pursuing large displacements is also wrong, because the larger the displacement is, the larger the motor equipped with the air compressor is, which not only increases the price, but also wastes the acquisition of funds, and wastes electricity and energy when used.

In addition, the peak usage, normal usage and trough consumption should also be considered when selecting the exhaust gas volume. If the amount of trough is relatively large, and the amount of usage and peak usage are not large, the common method in foreign countries is to use a relatively small amount of air compressor in parallel to obtain a larger amount of exhaust gas, and to turn on the power one by one as the air volume increases. Not only is it good for the power grid, but it also saves energy.

The second is to consider the use of gas conditions and conditions. Such as the use of gas space is small (vehicle, vehicle), should choose the vertical; if the gas occasions have long-distance changes (more than 500 meters), you should consider the mobile; if you can not supply power, you should choose diesel-driven If there is no tap water on the occasion, you must choose the air-cooled type. In air-cooled and water-cooled cooling systems, users often have the wrong understanding that water cooling is good, but it is not. The air-cooled type of domestic and foreign small air compressors accounts for about 90% of the total, because it is designed to be air-cooled and easy to use, requiring no water when used.

The fatal disadvantages of water-cooled air compressors are: they must have a complete water system, large investment; water-cooled coolers have a short life; in the north winter, they can easily freeze cylinders; in normal operation, a lot of water is wasted.

The third is to consider the quality of compressed air. Compressed air produced by general air compressors contains a certain amount of lubricating oil and a certain amount of water. In some cases, oil is banned and water is banned. At this time, attention must be paid not only to the selection of air compressors, but also to the attachments if necessary.

The solution: First, use a non-lubricated air compressor. This type of air compressor cylinder is substantially free of oil and its piston rings and packing are typically PTFE. However, this kind of machine also has disadvantages, poor lubrication, high failure rate; PTFE is also a harmful substance, food and pharmaceutical industry can not be used; non-lubricated air compressor can only achieve gas transmission without oil, can not be without water . The second and most common method is to add an air compressor (regardless of the type) to a primary or secondary purifier or dryer. This device can make the air compressor air contains neither oil nor water, so that the amount of oil and water in the compressed air below 5ppm, to meet the process requirements.

The fourth is to consider the safety of air compressor operation. The air compressor is a working machine with pressure, working with temperature rise and pressure, and the safety of its operation should be given priority. The state implements a standardized "two certificates" system for the production of air compressors, namely the air compressor production license and the pressure vessel production license (gas storage tank). Therefore, in the selection of air compressor products, the "two certificates" must be strictly examined. Usually, the product quality assurance system of certified manufacturers is perfect and there will be no major quality problems. Even if there are some problems, the manufacturers will be responsible for the three guarantees.