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Screw compressor

Screw compressors work by trapping air between two mesh rotors and reducing the volume of trapped air as it moves down the rotors. This reduction in volume results in the production of compressed air that can be used to power air tools, inflate plastics, or in many other applications.

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In the rest of this article, we will learn more about the screw compressor, including:

Introducing types of screw compressors

Comparison of oiled and oil-free screw compressors

Air compressor components

Basic functions and operations

Power supplies for mobile air compressors

Advantages of screw compressor

Disadvantages of screw compressor

Types of screw compressors

Introduction of screw compressor

Introducing types of screw compressors

When most people think of air compressors, reciprocating air compressors, also known as reciprocating air compressors, come to mind. These air compressors use a piston to push air into a smaller space and compress it, and then that compressed air is collected in an air receiver tank. Reciprocating air compressors are relatively inexpensive and have been around for decades.

Screw compressors are a newer and improved type of air compressor. They can be more expensive than traditional reciprocating models, but they have several advantages that make rotary air compressors the system of choice for large companies around the world.

Screw compressors work by trapping air between two meshed rotors and reducing the volume of trapped air as it travels down the rotors. This reduction in volume results in compressed air that can be used to power wind instruments, inflate plastics, and more.

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You can learn more about screw compressors versus other types of air compressors in this article:

Types of air compressors for your industry

The difference in the performance of screw compressors versus piston air compressors

Air compressor with reciprocating motor or air compressor with rotary screw motor?

Oil-lubricated screw compressors compared to oil-free screw compressors

Applications of screw compressor

Screw compressors used in a variety of industries are often oil-injected, meaning that oil is used to lubricate and seal the rotors at the air end. This allows the rotors to quickly build up high pressures and compress the air in one step. The oil is then separated from the air before it exits the system and is recycled to the air section for reuse. Oil-injected screw compressors allow compressor systems to consistently deliver high CFM and psi.

Oil-free screw compressor models are used in industrial, manufacturing or medical applications when no oil can enter the air stream, such as food packaging or medical oxygen. Oil-free rotary air compressors are more expensive because they require two stages of compression to achieve the same pressures as an oil-injected rotary system. Most companies only use oil-free rotary air compressors when they need them, so oil-free air compressors are not usually used in small workshops.

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Functions and basic operation of screw compressor

Screw compressors are pressurized systems made up of many interconnected components that work together to compress air.

Air and oil are essential aspects of many screw air compressor systems. Compressed air is the final product that requires atmospheric air, but lubrication is just as important. Oil is used to lubricate the system, which makes the screw compressor more efficient at a lower cost.

But the use of oil also complicates air compressor systems. In addition to requiring a mechanism to produce compressed air, rotary screw compressors also require oil circulation, filtering, and recycling.

Two separate systems work together. One creates air and the other circulates oil.

System flow process in screw compressor

Step 1: Atmospheric air enters the inlet valve.

Step 2: Air flows through the system pressure line to a valve on the regulator that adjusts the pressure for the entire system.

Step 3: Air is mixed with oil and compressed through the rotors.

Step 4: Air mixed with oil is discharged from the end of the system through the air discharge hose.

Step 5: Air mixed with oil enters the primary oil separator tank and separates most of the oil from the air.

Step 6: Air enters the secondary separation filter and captures the remaining oil in the air.

Step 7 – A: Oil-free air leaves the system. If an air tank is used, air will collect in the tank.

Step 7 – B: The oil is transferred to the oil cooler, cooled and then sent to the oil filter.

Step 8: The oil filter catches any contaminants left in the oil.

Step 9: The recycled oil is returned to the air through the scrub return line.

Note that visualizing the process in steps makes it easier to understand the overall flow, but these steps operate simultaneously. As soon as the air compressor is turned on, all the steps mentioned above are performed simultaneously and continuously.

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Advantages of screw compressors

Screw compressors have many advantages that make them ideal for a variety of applications. As a result, you will find air screw compressors in industrial, manufacturing and medical facilities where high quality equipment is required.

The advantages of rotary screw air compressors compared to other types of compressors are:

Continuous airflow / 100% duty cycle

Larger amounts of air

Higher CFM per HP

Longer lifespan

Better guarantees


Energy efficient

Most people prefer screw air compressors because of their longevity, reliability, and easy access to compressed air. Since rotary air compressors can run continuously, there is no need to wait for the air receiver tank to fill before starting to use air. These are the most popular advantages of rotary screw air compressors.

The long life of screw compressors is a significant advantage over reciprocating air compressors, which are jokingly called “throwaway air compressors” because they are often expected to fail after 3-5 years.

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Disadvantages of rotary screw air compressors

Screw air compressors have many advantages, but they are not the right choice for everyone. Common disadvantages of screw air compressor include:

High initial cost

Maintenance skills

The number one reason people choose a reciprocating air compressor over a screw compressor is the initial cost. Screw air compressors often cost twice as much as reciprocating air compressors, but there are situations where you really need a screw compressor.

Rotary screw air compressors may cost twice as much, but on average they last at least four times longer and produce more air. This makes them a safe investment for any business that intends to use compressed air for the long term.

Another disadvantage of rotary screw compressors is that they require skilled maintenance. Every type of air compressor needs regular service, but the complex nature of rotary systems requires a higher degree of expertise.


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