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Many users would like to know the working principle of oil-free rotary screw air compressors, product features, what applications , how to select and purchase 无油螺杆式空气压缩机s, today we are here to introduce the 无油螺杆式空气压缩机. I hope this article can help you and add some values when you buy an oil free screw air compressor.
As user requirements for the quality of compressed air sources increase, 无油的空气压缩机s are more and more widely used in industries that require high quality of compressed air sources, such as biology, medicine, electronics, food, medical, etc. In the automotive and chemical industries, the output accounts for more than 90% of the total output of 无油螺杆式空气压缩机s.
There are many types of 无油螺杆式空气压缩机s, with various types, and the value ranges from a few hundred dollars to tens of thousands of dollars.
Commonly used oil-free compressors are dry-type 无油螺杆式空气压缩机s, water-lubricated 无油螺杆式空气压缩机s, 无油涡旋式空气压缩机s, and oil-free centrifugal air compressors.
Air end of water-lubricated 无油螺杆式空气压缩机.
Star Wheel for air end
Star Wheel for air end
Rotors of screw air compressor
Dry oil free air end assembly
Today we only talk about dry 无油螺杆式空气压缩机s and water-lubricated 无油螺杆式空气压缩机.
1. The working principle of 无油的空气压缩机
1) The single-screw water-lubricated air compressor uses pure water for lubrication and cooling. The internal parts of the body are made of special materials, medical-grade stainless steel, and will never corrode.
Dry-type 无油的空气压缩机s still rely on lubricating oil to cool, and the body will have oil odor.
2) The pure water of the water-lubricated air compressor system always circulates in the system. The system will automatically change the water at the set time to ensure the quality of the water, and the operating temperature of the body is not higher than 50 degrees, so the water inside the body is not affected And the problem of scale.
The operating temperature of dry-type oil-free machines is higher than 200 degrees, which directly affects the life of the cooling oil and bearings.
3) The single-screw water-lubricated oil-free machine adopts imported special bearings, so there is no problem with direct water lubrication, high efficiency, low head noise, and few bearing combinations.
Twin-screw air compressors generally use FAG or SKF bearings, which are low-temperature bearings with short life and high noise, and there are many combinations of double-head bearings.
4) The single-screw water-lubricated air compressor sprays pure water directly into the body. Because of the high specific heat value of water, the compression chamber is almost in the ideal state of isothermal compression, and the compression process with the lowest energy consumption.
The cooling oil of the dry-type oil-free machine is about 100 degrees, and the temperature of the compression chamber exceeds 200 degrees. The temperature difference is relatively large, so the energy consumption is relatively high.
5) Single-screw water-lubricated oil-free machine, the body and the motor are directly connected, the speed is as low as 3000 rpm, there is no speed-increasing gear, the bearing life is long, and the maintenance cost is low.
A speed-increasing gear must be added between the body of the dry-type oil-free machine and the motor. Because the speed is higher than 18,000 rpm, the speed-increasing gear is required to increase the speed, the bearing life is short, and the maintenance cost is high.
6) The water-lubricated air compressor uses water to cool and lubricate the seal, the air quality is guaranteed, and the speed is about 3000 rpm. The temperature is around 55 degrees, and the maintenance cost is low.
The dry twin-screw air compressor uses oil to cool the bearings. The air quality cannot be completely clean and environmentally friendly. The secondary compression speed reaches about 18,000 rpm, which consumes labor, and the temperature reaches about 200 degrees, which is unsafe and high maintenance costs. .
2. Working principle of oil-free water lubrication air compressor
Oil-free water-lubricated screw air compressors belong to a relatively common type of 无油的空气压缩机 family. They are lubricated by pure water, so the compressed air is 100% free of any oil. The biggest feature is that the operating temperature is not high. The theoretical "isothermal compression" can be achieved, and the noise emitted during work is also very small, which will not cause any impact on the surrounding environment. Therefore, oil-free 水润滑 screw air compressors have also attracted many customers' attention.
Water cooling is a heat dissipation method, in addition to 空气冷却; and water lubrication also has 空气冷却 and water cooling heat dissipation methods, its advantage is that ordinary air compressors need to add air compressor oil, while water lubrication air compressors Only pure water is needed to replace lubricating oil.
Benefits of Oil-Free 水润滑 Air Compressed
The following is a brief list of the advantages of oil-free 水润滑 screw air compressors.
Features:
(1) Reasonable structure and ideal force balance.
The main characteristics of oil-free screw compressors are caused by the symmetrical structure of a star wheel on each side of the screw.
(2) High efficiency
1. The volume utilization rate of the screw groove is high (the screw groove is used twice for one rotation of the screw).
2. No clearance volume, large single machine capacity.
3. Ideal isothermal compression. Due to the good thermal conductivity of water, when lubricating water is injected into the compression chamber, the temperature will drop to within 45°C, which is close to the suction temperature.
(3) No oil
Water is used instead of oil to realize the four major functions of lubrication, cooling, sealing, and noise reduction, providing high-quality 100% oil-free air, pollution-free, and no special treatment of discharged water, which meets environmental protection requirements.
(4) Low noise and low vibration
The oil-free screw compressor has good force balance, so the vibration is small, and there is no special requirement on the foundation, especially the star wheel material is made of special customized polymer composite material, the working cavity is sprayed with lubricating water, and there is no speed-increasing gear, so it runs Low noise.
(5) Long life of the host
The symmetry of the structure and the possibility of setting the return hole make the radial and axial forces generated by the oil-free screw compressor work to be completely balanced. Therefore, the load of the rotor bearing is extremely small and can run for 50,000 hours; the star wheel made of resin material can be used for 25,000 to 30,000 hours, and the design life of the compressor is as high as 300,000 hours.
However, its shortcomings are also obvious:
That is, the ambient temperature cannot be lower than 0°C, otherwise the pure water used as a lubricating medium will freeze!
How to select and purchase an 无油螺杆式空气压缩机 not only involves how to use funds rationally, but also has a direct relationship with the economy and reliability of normal operation in the future.
General-purpose 无油螺杆式空气压缩机s are in accordance with national standards, and the exhaust pressure is 0.7MPa-1 Mpa. If it is higher or lower than this pressure, it is a non-standard special 无油螺杆式空气压缩机.
The basic criteria for choosing 无油螺杆式空气压缩机s are economy, reliability and safety.
One is that the level of exhaust pressure and the size of the exhaust volume should be considered. The exhaust pressure of the 无油螺杆式空气压缩机 for general-purpose aerodynamics is 0.7MPa, and the old standard is 0.8MPa. At present, there is an 无油螺杆式空气压缩机 with an exhaust pressure of 0.5MPa, which is unreasonable from the perspective of use, because the pressure margin is too small for pneumatic tools, and the air delivery distance is a little longer. use.
In addition, from a design point of view, this 无油螺杆式空气压缩机 is designed for one-stage compression. If the pressure ratio is too large, it will easily cause the exhaust temperature to be too high, causing the cylinder to deposit carbon and causing accidents. If the 无油螺杆式空气压缩机 used by the user is larger than 1MPa, it should be specially manufactured, and the method of forced pressurization cannot be adopted to avoid accidents.
The air displacement is one of the main parameters of an 无油螺杆式空气压缩机. The air volume of an 无油螺杆式空气压缩机 should be matched with the required air displacement, and a 10% margin should be left. If the air consumption is large but the displacement of the 无油螺杆式空气压缩机 is small, when the pneumatic tool is started, the exhaust pressure of the 无油螺杆式空气压缩机 will be greatly reduced, and the pneumatic tool cannot be driven. Of course, blindly pursuing a large displacement is also wrong, because the larger the displacement, the larger the motor equipped with the 无油螺杆式空气压缩机, not only the higher the price, but also a waste of purchase funds, as well as a waste of electricity when used.
In addition, when selecting the exhaust air volume, the peak volume, the usual volume and the low volume volume should also be considered. If the trough consumption is large, but the usual and peak consumption are not large, the usual method abroad is to use 无油螺杆式空气压缩机s with smaller displacements in parallel to obtain a larger displacement, which will increase one by one as the air consumption increases. Turn on the machine, which is not only good for the grid, but also saves energy.
The second is to consider the occasion and conditions of air use. If the air space is narrow (for boats, vehicles), vertical type should be selected; if there is a long-distance change (more than 500 meters) in the air usage occasion, mobile type should be considered; if the occasion cannot be used for power supply, diesel engine-driven type should be selected ; If there is no tap water in the application, the air-cooled type must be selected.
In the two cooling methods of 空气冷却 and water cooling, users often have the wrong understanding that water cooling is good, but it is not. The air-cooled type accounts for more than 90% of the small 无油螺杆式空气压缩机s at home and abroad. This is because the air-cooling is simple in design and does not require a water source when in use.
The fatal shortcomings of water-cooled 无油螺杆式空气压缩机s are four:
1. There must be a complete water supply and discharge system, and the investment is large;
2. Water-cooled cooler has a short life;
3. It is easy to freeze the cylinder in the northern winter;
4. In normal operation, a lot of water will be wasted.
The third is to consider the quality of compressed air. Generally, the compressed air produced by 无油螺杆式空气压缩机s contains a certain amount of lubricating oil and a certain amount of water. In some cases, oil and water are prohibited. At this time, not only should pay attention to the selection of 无油螺杆式空气压缩机s, it is necessary It is necessary to increase the air after-treatment device.
The solution: One is to use a non-lubricated and 无油螺杆式空气压缩机. This kind of 无油螺杆式空气压缩机 basically does not contain oil in its cylinder, and its piston ring and packing are generally PTFE. But this kind of machine also has shortcomings, poor lubrication and high failure rate; PTFE is also a harmful substance, which cannot be used in the food and pharmaceutical industries; non-lubricated and 无油螺杆式空气压缩机s can only deliver air without oil, and cannot be used. To no water.
The second and commonly used method is to add an 无油螺杆式空气压缩机 (no matter which type) to a primary or secondary purification device or a dryer. This device can make the air of the 无油螺杆式空气压缩机 contain neither oil nor water, so that the oily water content in the compressed air is below 3ppm, which can meet the process requirements.
We have some misunderstandings about 无油的空气压缩机s and the compressed air they produce.
1. The compressed air produced by an 无油的空气压缩机 is oil-free - Wrong
Although no oil is used in the compression chamber, the oil will not come into contact with the compressed air, but the oil vapor contained in the atmosphere itself cannot be removed, which makes the compressed air still contain a small amount of oil impurities. After measurement, there is no The oil content in the compressed air produced by the oil compressor has a very close relationship with the air quality, the air compressor room environment, and the cleanliness of the compressor.
2. 无油的空气压缩机s do not use oil - Wrong
Although oil is not used in the process of compressing air to come into contact with air, oil is still used to cool the compressor and lubricate the operating parts, so that the compressor can operate normally and stably.
3. The compressed air produced by the 无油的空气压缩机 is pollution-free - Wrong
There are many pollutants in the atmosphere, including dust, water vapor, oil vapor, microorganisms, etc. The compressed air produced by the 无油的空气压缩机 can only ensure that no oil is brought into the compressed air during the compression process, but it cannot remove the magazines in the air itself. This means that the compressed air produced by an oil-free compressor is not necessarily pollution-free, and the use of air treatment products can help reduce pollution to the required level.
4. 无油的空气压缩机 does not require air treatment products - Wrong
As described in point 3, the air quality of compressed air produced by 无油的空气压缩机s is largely restricted by the environment. Therefore, users need to configure corresponding 压缩空气处理设备 according to their own requirements for compressed air quality to meet their own needs and demand for compressed air quality.
5. Low cost of 无油螺杆式空气压缩机- Wrong
In fact, because the compression ratio is much lower than that of oil-lubricated compressors, the energy consumption is higher. Oil-free compressors with the same power can produce more than 40% less air than energy-saving screw compressors. Although the compression chamber is not lubricated by oil, other The grease and air filter in the parts still need regular maintenance. The core rotor is generally treated with a special coating, has a service life, has a high requirement for water, and is easily damaged. The maintenance of the air end is a necessary option for an oil-free machine. The high cost can account for 50% of the equipment cost.
We believe that for most users, it is not necessary to really need 0 grade oil-free compressed air, but more to solve the problem of oil impurities. For refrigeration dryers, heat-less regeneration dryers, 微热再生 dryers, etc. The pollution of equipment is a choice to prevent the efficiency of 压缩空气处理设备 from decreasing or even losing the water removal function. For users who need real grade 0 oil-free compressed air, it is difficult to obtain oil-free compressed air steadily and continuously by using 无油的空气压缩机s alone, and they still need to be equipped with corresponding 压缩空气处理设备.
Conclusion:
无油螺杆式空气压缩机s are widely used in textile, energy, transportation, medicine, food, petrochemical, and machinery manufacturing industries due to higher air quality requirements from customers.
Dry-type and water-injected oil-free have different working principles.
Dry-type 无油螺杆式空气压缩机 - have bigger airflow capacity, More expensive, because more maintenance cost
Oil-free water-injected screw air compressor- Due to the use of cheap pure water for lubrication, there is no air compressor oil, oil fine separation core, oil filter, and its maintenance cost is relatively low.
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