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How do Rotary screw air compressors work

April 23, 2021

How do Rotary screw air compressors work

Through this article, we can help you understand the basic knowledge of the rotary screw air compressor, the main technical parameters, how to select the screw air compressor according to these parameters.

Screw air compressor is designed according to the working principle of a twin screw (also known as a yin and yang rotor) rotating to make the volume change of the air, it can suck natural air and then go through several internal processes to complete the work, and finally Discharge compressed air that meets the pressure requirements. This machine is called a screw air compressor.

How do Rotary screw air compressors work

Basic knowledge of screw air compressor

1. The working pressure of the screw air compressor

There are many forms of pressure units. Here we mainly introduce the pressure units commonly used in screw air compressors;

① The working pressure is often called the exhaust pressure by the user. Working pressure refers to the highest pressure of the exhaust air from the air compressor;

② The commonly used working pressure unit is: bar or Mpa, 1 bar = 0.1 Mpa;

③ In general, users usually call the pressure unit: Kg (kg), 1 bar = 1 Kg.

2. Volume flow of screw air compressor

① Volume flow, the user often weighs the exhaust volume. Volume flow refers to the volume of air discharged by the air compressor per unit time under the required exhaust pressure, converted to the amount of intake state.

② The volume flow unit is: m³/min (cubic/minute) or L/min (liter/minute), 1m³ (cubic) = 1000L (liter);

③ In general, the commonly used flow unit is: m³/min (cubic per minute);

④ Volume flow is also called displacement or nameplate flow in China.

3. The power of the screw air compressor

① Generally, the power of the air compressor refers to the power of the matching drive motor or the nameplate of the diesel engine;

② The unit of power is KW (kilowatt) or HP (hp/horsepower), 1KW ≈ 1.333HP.

4. Selection guide for screw air compressor

Selection of working pressure (exhaust pressure):

When the user is preparing to purchase an air compressor, first determine the working pressure required by the air end, plus 1-2, The margin of bar, then select the pressure of the air compressor, (the margin is to consider the pressure loss from the installation location of the air compressor to the actual air end pipeline distance, according to the length of the distance between 1-2

Appropriate consideration of pressure margin between bar). Of course, the size of the pipeline diameter and the number of turning points are also factors that affect the pressure loss. The larger the pipeline diameter and the fewer turning points, the smaller the pressure loss; on the contrary, the greater the pressure loss.

Therefore, when the distance between the air compressor and each air end pipeline is too far, the diameter of the main pipeline should be appropriately enlarged. If the environmental conditions meet the installation requirements of the air compressor and the working conditions permit, it can be installed near the air end.

Selection of volume flow:

When selecting the volumetric flow rate of an air compressor, you should first understand the volumetric flow rate of all air-consuming equipment, and multiply the total flow rate by one.

Maintenance items. In addition to the three-level maintenance items, you also need:

1. Check the joint contact and insulation resistance of the electrical part of the screw air compressor;

2. Replace the motor grease (replace every 8000 hours of operation). If there are parameters in the equipment manual, the manual shall prevail;

3. Clean the relief valve (intake valve);

4. Clean the minimum pressure valve (pressure maintenance valve);

5. Clean the oil return check valve;

6. Clean the temperature control valve;

7. Clean the cooler;

8. Clean the water and air separator;

9. Correct all parameters.

Note: The above maintenance should only be carried out after the equipment is confirmed that there is no electricity and no pressure.

How to select the air compressor based on the main parameters

The new project can be selected according to the flow value provided by the design institute;

Learn about the volumetric flow parameters of the air-consuming equipment from the air-consuming equipment supplier for selection;

The air compressor station can be selected with reference to the original parameter value and the actual air consumption situation;

Appropriate selection is beneficial to both the user and the air compressor equipment. Excessive selection is wasteful, and too small selection may cause the air compressor to be in a long-term loading state or insufficient air or pressure can not reach the disadvantages.

The relationship between power, working pressure and volumetric flow

In the case of constant power, when the speed changes, the volumetric flow and working pressure also change accordingly; for example: a 22KW air compressor, the working pressure is determined to be 7bar at the time of manufacture, calculated according to the main compressor technical curve Speed, displacement is 3.8 m3/min;

When it is determined that the working pressure is 8bar, the speed must be reduced (otherwise the drive motor will be overloaded). At this time, the exhaust volume is 3.6 m3/min; because the speed is reduced, the exhaust air is also reduced, and so on.


The selection of power is to meet the working pressure and volume flow conditions, and the power supply capacity can meet the power of the matched drive motor.

Therefore, the steps for selecting an air compressor are:

1) Determine the working pressure

2) Determine the corresponding volume flow

3) Determine the power supply capacity

Dream Compressor have a wide range of rotary screw air compressor for sale including oil injected, oil free type, rotary screw air compressor with dryer, small rotary screw air compressor.

Product keywords: rotary screw air compressor,Screw air compressor, rotary screw air compressor for sale, rotary screw air compressor with dryer, small rotary screw air compressor

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