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What Are Screw Air Compressor

May. 28, 2020

1.    What is the screw air compressor:

A screw compressor is a type of volume gas compression machine that works as a swing movement. Gas compression depends on the volume change to achieve, and the volume change is achieved by a pair of rotors of the compressor in the chassis for a swing movement.
Single-stage compression screw air compressor - the head is a screw air compressor consisting of a pair of Yin and Yang rotors. This model is a widely used screw air compressor.

Two-stage screw air compressor - the head is composed of two pairs of rotors, the gas after the first level of compression into the second-level compression, compression ratio increased, the power than the first-stage compression air compressor reduced.


2.The basic structure of the screw compressor:

In the compressor's body, a pair of meshing spiral rotors are configured in parallel, usually with a convex rotor outside the knot circle, called a yang rotor or an impotence screw. The rotor with concave teeth in the knot circle, called the yin rotor or the en noun screw, is generally connected with the prime rhododendron, and the yang rotor turns the yin rotor. The last pair of bearings on the rotor achieves axial positioning and is subject to axial forces in the compressor. 
The sub achieves radial positioning and is subject to radial forces in the compressor. At both ends of the compressor body, a particular shape and size of the hole are opened. One for suction called an air intake, and the other for exhaust, called an exhaust port.

3.Screw air compressor working principle:

screw compressor working cycle can be divided into the intake, compression, and exhaust three processes. As the rotor rotates, each pair of meshing teeth completes the same work cycle in succession.


1) Intake process: When two rotors rotate, the trench space is empty when it is turned to the air intake

Between the largest, at this time, the rotor tooth ditch and the air intake port, because in the exhaust of the tooth ditch gas is wholly discharged, in a vacuum state, when the air intake, the external gas is inhaled, into the two rotors of the tooth ditch. When the gas fills the entire trench, the rotor intake side turns away from the air intake, and the gas in the tooth ditch is closed.

2) Compression process: Yin and Yang rotor at the end of inhaling, its yin and yang rotor tip will be closed with the service. At this time, the gas in the tooth ditch no longer outflow. The meshing surface gradually moves towards the exhaust end. The gap space between the meshing surface and the exhaust port is slowly smaller, and the gas in the trench is compressed.

3) Exhaust process: When the rotor's meshing end surface is transferred to connect with the enclosure exhaust port, the compressed gas begins to drain until the meshing surface of the tip, and the tooth trench is moved to the exhaust end surface, at which time the meshing surface of the yin and yang rotor and the tooth trench space of the enclosure exhaust port of the enclosure is zero, that is, the exhaust process is completed, at the same time the meshing surface of the rotor and the air intake between the attachment of the machine shell reaches the longest and the most extended air intake process.


The capacities of rotary-screw compressors are typically rated in horsepower (HP), Standard Cubic Feet per Minute (SCFM)* and pounds per square inch (PSI.)

Rotary-screw compressors are commonly available in the 5 through 500 HP range and can produce air flows in excess of 2500 SCFM. While there are high pressure rotary-screw compressors, within the compressed air community, the upper pressure limit is generally around 125 PSI.For units in the 5 through 30 HP range the physical size of these units are comparable to a typical two-stage compressor.

5. Screw air compressor benefits:

1) High reliability: the screw compressor components are few, no consumables, so it runs reliably, has a long life, and can have a service interval of 4-8 million hours.

2) Smooth operation and maintenance: the operator does not have to be professionally trained to operate without human supervision.

3) Right power balance: the screw compressor does not have an unbalanced inertial force, the machine can work smoothly at high speed, can achieve no foundation operation.

4) Steadfast response: The screw compressor has the characteristics of forced gas transmission. Exhaust volume is almost immune to the impact of exhaust pressure. A wide range can ensure high efficiency.

5) Can mix input: the rotor flank of the screw compressor has a gap so that it can withstand liquid impact, can be pressured to deliver liquid gas, dust gas, natural polymerization gas, and so on.

6.Screw air compressor disadvantages:

1) High cost: the rotor flank of the screw compressor is a space surface, need to use particular tools, inexpensive special equipment for machining. Also, the processing accuracy of screw compressor cylinders has high requirements.

2) Not suitable for high-pressure situations: due to the rotor stiffness and bearing life restrictions, screw compressor can only be applied to the medium and low-pressure range, exhaust pressure generally can not exceed 3.0Mpa.

3) Can not be made into a miniature: screw compressor relies on the gap seal gas, at present, only the volume flow is higher than 0.2m3/min, screw compressor has superior performance.

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