A pair of intermeshing helical male and female rotors are installed in the cylinder of a screw air compressor, and they rotate in opposite directions. The clearance between the rotors and between the casing and the rotors is only 5 - 10 threads. The main rotor is driven by an engine or an electric motor, and the female rotor is driven by an oil film formed by injection oil from the main rotor, or driven by the synchronous gears at the ends of the main rotor and the driven rotor. When the groove of the helical rotor passes through the suction port, it is filled with gas. When the rotor rotates, the rotor groove is closed by the casing wall to form a compression chamber. After the rotor groove is closed, lubricating oil is injected into the compression chamber, playing the roles of sealing, cooling and lubricating. When the rotor rotates to compress the mixture of lubricant + oil - gas, the volume of the compression chamber decreases, and the oil - gas mixture is compressed towards the exhaust port; when the compression chamber passes through the exhaust port, the oil - gas mixture is discharged from the compressor, completing a suction - compression - exhaust process. Each rotor of the screw machine is supported by anti - friction bearings, and the bearings are fixed by the end cover near the end of the rotating shaft. The intake end is supported by a roller bearing, and the exhaust end is supported by a pair of opposed tapered roller bearings. Usually, the bearing at the exhaust end positions the rotor, that is, a thrust bearing, which resists the axial thrust, bears the radial load, and provides the necessary minimum axial running clearance. The working cycle can be divided into three processes: suction, compression and exhaust. As the rotors rotate, each pair of intermeshing gear teeth completes the same working cycle.

03 Advantages of Scroll Air Compressors

1. There is no reciprocating motion mechanism, so the structure is simple, the volume is small, the weight is light, and there are few parts (especially few wearing parts), and the reliability is high.
2. The torque change is small, the balance is high, the vibration is small, and the operation is stable, so the operation is simple and easy to realize automation.
3. It has high efficiency within its applicable refrigeration capacity range.
4. Low noise.

04 Advantages of Screw Air Compressors

1. Similar to piston compressors, screw compressors are positive - displacement compressors. In terms of application effects, screw air compressors have the following advantages.
2. High reliability. Screw compressors have few components and no easily - worn parts, so they operate reliably and have a long service life. The overhaul interval can reach 40,000 - 80,000 hours.
3. Convenient operation and maintenance. Screw compressors have a high degree of automation. Operators don‘t need long - term professional training and unmanned operation can be achieved.
4. Good dynamic balance. Screw compressors have no unbalanced inertia force. The machine can work stably at high speeds and can operate without a foundation. It is especially suitable as a mobile compressor, with a small size, light weight and small floor area.
5. Strong adaptability. Screw compressors have the characteristic of forced gas delivery. The volumetric flow rate is hardly affected by the discharge pressure. They can maintain high efficiency within a wide range. Without any changes to the compressor structure, they are suitable for various working conditions.

05 Disadvantages of Scroll Air Compressors

1. The surfaces of the moving parts are mostly curved. The processing and inspection of these curved surfaces are complex, and some even require special equipment, so the manufacturing cost is relatively high.
2. Between the moving parts or between the moving parts and the fixed parts, a certain movement gap is often maintained to achieve sealing. Gas leakage through the gap is inevitable, which restricts the rotary compressor from achieving a relatively large compression ratio. Therefore, it is mostly used under air - conditioning conditions.

06 Disadvantages of Screw Air Compressors

1. The tooth surfaces of the rotors are spatial curved surfaces, which require the use of special cutters and processing on expensive equipment. There are also high requirements for the processing accuracy of the compressor components, and high - precision equipment must be used.
2. Due to the periodic connection of the tooth - space volume with the suction and exhaust ports, the noise of the compressor is relatively high.
3. Due to the limitations of rotor rigidity and bearing life, the interior of the compressor can only rely on gap sealing. Therefore, the screw compressor is only suitable for medium - and low - pressure ranges and cannot be used in high - pressure situations.
4. Due to the large amount of injected oil, the oil treatment system is complex, so there are many auxiliary equipment for the unit.
5. The screw compressor relies on gap sealing for gas. It does not have superior performance within a small volume range.

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