How To Distinguish Between Screw Air Compressors And Piston Air Compressors

Screw air compressors and piston air compressors can be said to be the two models with a high market share in the current air compressor market. The piston air compressor was mostly used before. In recent years, with the characteristics of screw air compressors, they have gradually replaced piston air compressors and become the mainstream of the air compressor market. So, what is the difference between piston air compressors and screw air compressors?
1, Structure and working principle.
1. A piston type oil-free lubrication air compressor.
The piston type oil-free lubrication air compressor consists of a compressor host, cooling system, regulating system, lubrication system, safety valve, motor, and control equipment. The compressor and motor are fastened to the base with bolts, and the base is fixed with anchor bolts. During operation, the motor directly drives the crankshaft through a coupling, driving the connecting rod, crosshead, and piston rod, causing the piston to move back and forth in the compressor cylinder, completing processes such as suction, compression, and discharge. This machine is a double acting compressor, which means that the piston moves up and down to suck in, compress, and discharge air.
2. Screw air compressor.
The screw air compressor consists of a screw head, motor, oil and gas separation drum, cooling system, air conditioning system, lubrication system, safety valve, and control system. The entire machine is installed in a box, forming a self-contained unit and placed directly on a flat cement floor without the need for anchor bolts to fix it. A screw head is a dual axis volumetric rotary compression head. During operation, the motor directly drives the main rotor through a coupling (or belt). Due to the meshing of the rotors, the main rotor directly drives the secondary rotor to rotate together. The coolant is directly sprayed into the meshing part of the rotor through the nozzle at the lower part of the compressor housing, mixed with air, and takes away the heat generated by compression, achieving a cooling effect. Simultaneously forming a liquid film to prevent direct metal to metal contact between the rotor and the gap between the enclosed rotor and the casing. The sprayed coolant can also reduce the noise generated by high-speed compression.
The main components of a screw air compressor are the screw head and the oil and gas separation drum. The screw head is sucked in through an intake filter and intake control valve, while oil is injected into the air compression chamber to cool and seal the head, lubricate the screw and bearings, and generate compressed air in the compression chamber. The compressed oil and gas mixture is discharged into the oil and gas separation drum. Due to the effects of mechanical centrifugal force and gravity, the vast majority of oil is separated from the oil gas mixture. The air passes through the oil and gas separator core made of borosilicate glass fiber, and almost all oil mist is separated. The oil separated from the oil and gas separator core is returned to the screw head through the return pipe. An oil filter is installed on the return pipe. After being filtered by an oil filter, the clean oil flows back to the screw head. After oil separation, compressed air leaves the oil cylinder and enters the aftercooler through the minimum pressure control valve. The aftercooler will cool the compressed air and discharge it into the air storage tank for use by various gas consuming units. The condensate is concentrated in the air storage tank and drained through automatic or manual drainage. When the oil is separated, compressed air leaves the oil cylinder and enters the aftercooler through the minimum pressure control valve. The aftercooler will cool the compressed air cooler into the air storage tank.
2, Characteristics.
1. A piston type oil-free lubrication air compressor.
The piston rings in the cylinder of an oil-free air compressor and the packing in the packing device both use polytetrafluoroethylene with self-lubricating properties as the sealing element. Therefore, the cylinder and packing device do not need to be lubricated with lubricating oil. Under normal circumstances, the compressed gas is basically pure and free of oil stains, and there is no need to add an oil removal device. The disadvantages of this machine are high motor power, unstable exhaust pressure, high exhaust temperature, high noise, heavy maintenance workload, and high maintenance cost.
2. Screw air compressor.
The precise fit between the male and female rotors of the screw air compressor reduces gas reflux leakage and improves efficiency; Only the rotors mesh with each other, without the reciprocating motion of the cylinders, reducing vibration and noise sources. The unique lubrication method has the following advantages: continuously injecting coolant into the compression chamber and bearings, simplifying complex mechanical structures; Injecting coolant can form a liquid film between the rotors, and the secondary rotor can be directly driven by the main rotor without the need for high-precision synchronous gears; Injecting coolant can increase air tightness, reduce noise generated by high-frequency compression, and absorb a large amount of compression heat. Therefore, screw air compressors have advantages such as low vibration, no anchor bolt fixation, low motor power, low noise, high efficiency, stable exhaust pressure, and no vulnerable parts.
3, Main malfunction.
1. A piston type oil-free lubrication air compressor.
The piston ring and packing device do not require oil lubrication. Under normal circumstances, the compressed gas is basically pure and does not contain oil. However, due to incomplete oil scraping and poor sealing of the oil scraper ring, the oil often runs onto the packing device or even the piston ring, causing compressed air to contain oil. In addition, the exhaust temperature is high, sometimes up to 200 ℃; The cooler is blocked and the cooling effect is poor; The piston rings are stained with oil and are particularly prone to wear and tear; Valve leakage; Wear of cylinder liner, etc.
2. Screw air compressor.
Screw air compressors have very few malfunctions, and as long as the oil and gas separator, air, and oil filters are regularly maintained, their normal operation can be guaranteed. The maintenance of two 10m3 screw machines is due to blockage of sewage pipes and control panel failure. In the past two years, the host system has been running normally.
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