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System Description Of Screw Air Compressor I

Time: 2020-09-25

After the dust is filtered out by the air filter, the air enters the main compression chamber through the intake valve for compression, and is mixed with the lubricating oil. The compressed air mixed with the oil enters the oil-gas tank, and then passes through the oil-gas separator, the pressure sustaining valve, after cooler, and the gas-water separator, and then into the use system.
This article takes a certain brand of air compressor as an example to briefly introduce the system process of screw air compressors. The data and accessories mentioned in article are for reference only.


Function description of each component in the main air source passage

1.Air Filter

The air filter is a dry paper filter. The pore size of the filter paper is about 10um. Usually every 600-1000 hours (depending on the environment) it should be taken out to remove the dust on the surface. The cleaning method is to use low-pressure air to remove the dust from the inside out. The air filter is equipped with a differential pressure indicator or pollution indicator. If the display panel shows that the air filter is clogged or the red line on the pollution indicator is visible, it means that the air filter must be cleaned or replaced.

2.Air Inlet Valve

a.When starting, the intake valve is in the closed state, which enables the compressor to start under low load, and reduces the load when the motor starts, then facilitates the normal operation of the motor. At the same time, the no-load air inlet hole of the air inlet valve body avoids over-vacuum in the compressor body. And the required air pressure of the system could be established as soon as possible.
b.Empty and Heavy Conversion After the compressor starts, the intake valve opens. The compressor is converted to the heavy vehicle state, and that is the normal working state.
c. Automatic pressure relief and check function after shutdown After stopping, the air intake valve can quickly remove the air pressure of the oil-gas tank, so that the motor will not be overloaded next time; at the same time, it can prevent the compressed air in the oil-gas tank from flowing back, causing the rotor to reverse and the oily air to be ejected from the air filter.


3. Temperature probe

In the case of water loss, oil loss, insufficient water, or insufficient oil, the exhaust temperature may be too high. When the exhaust temperature reaches the set temperature value, the system will automatically shut down. The trip temperature is generally set at 105-110℃, and the exhaust temperature can be read on the LCD panel.


4.Oil-gas Tank

The side of the oil-gas tank is equipped with an oil level indicator, and the oil level of the static lubricating oil should be between the high oil level line and the low oil level line of the oil level gauge. An oil drain valve is installed under the oil drum, and the oil drain valve should be slightly twisted to remove the condensed water in the oil drum before each start. Please note: Once oil flows out, immediately close the drain valve to avoid excessive oil flow out. There is a refueling hole on the barrel for refueling.


5. Oil-gas separator 

The compressed air from the air compressor head entrains oil droplets of various sizes. Large oil droplets are easy to separate when passing through the oil and gas separation tank, while small oil droplets (suspended oil particles below 1um in diameter) must be filtered through the micron and glass fiber filter layer of the oil and gas separation filter. The oil particles are directly intercepted by the filter material through the diffusion effect of the filter material, and the mechanism of inertial collision condensation makes the suspended oil particles in the compressed air quickly condense into large oil droplets. Under the action of gravity, the oil collects at the bottom of the oil core and passes through the bottom. The inlet of the oil return pipe in the recess returns to the lubricating oil system of the machine head, so that the compressor discharges more pure and oil-free compressed air.


6. Safety valve

When the system pressure is set improperly or malfunctions, and the pressure in the oil and gas barrel is higher than the set exhaust pressure by more than 0.1MPa, the safety valve will trip to make the pressure drop below the set exhaust pressure. The safety valve has been adjusted before leaving the factory, please do not adjust it at will. 


7. Relief valve

The relief valve is a mechanical vent valve. When the vehicle is stopped or empty, the valve is opened to discharge the pressure in the barrel to ensure that the compressor can be started or run under no load.


8. Pressure maintenance valve (also known as minimum pressure valve and pressure maintaining valve)

Located at the outlet of the oil fine separator above the oil and gas barrel, the opening pressure is set at about 0.45Mpa, and the function of the pressure maintaining valve is:  
A.   Priority is given to establishing the circulating pressure required by the lubricating oil to ensure the lubrication of the body;
B. It can be opened only after the pressure exceeds 0.45MPa, which can reduce the air flow rate through the oil fine separator, in addition to ensuring the effect of the oil fine separator, and protect the oil fine separator from damage due to excessive pressure difference.


9. After cooler

1) If it is an air-cooled cooler, use a cooling fan to draw in cold air and cool the compressed air through the cooler. The exhaust temperature is generally below (atmospheric temperature + 10°C). Air-cooled air compressors are more sensitive to ambient temperature conditions. When choosing a place for placement, it is best to pay attention to the ventilation conditions of the environment.
2) If it is a water-cooled model, use a shell-and-tube cooler and use cooling water to cool the compressed air. The exhaust temperature is below 45°C (the temperature of the cooling water inlet should not exceed 35°C). Water-cooled air compressors are not sensitive to ambient temperature conditions, and it is easier to control their exhaust temperature. If the quality of the cooling water is too poor, the cooler will easily scale and become blocked. Special attention must be paid.


10. Gas-water separator

The cyclone centrifugal structure can remove the moisture, oil droplets and impurities that are condensed after the air is cooled. The compressed air passes through the regulating valve under the air-water separator and is slightly opened to just allow the condensate to flow out without causing a large amount of air leakage. . There are automatic drainage and manual drainage for users to choose.


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