When it comes to modern industrial machinery, the screw compressor is always one of the most widely used technologies in this field. Screw compressors are very popular due to their high reliability and adaptability, making them essential tools in many industrial processes and applications. This durable technology is so suitable for hard and permanent tasks that many businesses worldwide would face operational challenges without it.

What is a screw compressor and what applications does it have?

Screw compressors are positive displacement machines with rotary movement, also known as "screw compressors" or "lobe screw compressors." They have gradually expanded their range of applications to be used as a third force in the compression industry. These devices are now primarily used in low-pressure and refrigeration applications. Screw compressors are also relatively simple and cost-effective.

The features of this device allow it to have more applications compared to other compressors and be used in various industries and businesses. Typically, screw compressors are used for applications that require a large volume of compressed air.

How does a screw compressor work?

In a screw compressor, based on the rotary movements of the blower, air is compressed while suction and discharge occur simultaneously and in parallel. This is why one of the features of this type of air compressor is the constant flow rate, which prevents impacts.

The precise explanation of how this compressor operates is somewhat complex. In simple terms, the screw-shaped blower helps to draw in air by rotating on its axis. The sucked air is compressed in a sealed chamber and exits from the other side. This screw must be positioned at the closest distance to the body to achieve maximum efficiency.

How a screw compressor operates

1. The surrounding ambient air enters the compressor chamber through a valve. One or two rotors (blades) are situated inside the chamber and rotate at a very high speed while the device is running.

2. The rotation of the blades traps air within the internal cavities and thus directs the air downward out of the chamber.

3. The internal chamber size of the screw compressor reduces and moves away from the valve. The reduction in air volume within the chamber significantly increases its pressure.

4. The increased pressure applied to the trapped air leads to further compression.

5. The air pressure causes the compressor's discharge valve to open, ultimately allowing the pressurized air to enter another receiver or holding tank.

6. All the previous stages compress the air as much as possible, and then it can be directed to other device equipment such as dryers or oil or water separators for drying and contamination removal.

How the screw compressor was created and evolved!

Early screw compressors were more similar to oil-free or dry machines. They rotated at high speeds to minimize internal gas circulation and were also very noisy. In the 1950s, oil-injected machines entered the market and became useful in natural gas compression and refrigeration; on the other hand, the noise produced was significantly reduced so they could be used in various environments.

Types of screw compressors

Screw compressors are generally presented in two main designs:

Dry screw compressors

Both types of compressors consist of rotors that are paired closely together. In other words, a dry compressor consists of two rotors; a pair of rotors that are closely matched and installed firmly inside a cylinder. Dry screw compressors do not use any oil between the rotors. This type of machine has significantly lower power compared to oil-injected models.

The reason for producing such compressors is their use in sensitive industries like pharmaceuticals and food production. Screw compressors have a maximum capacity of 3 bar, meaning that the output air pressure from this model is a maximum of three times the input air pressure.

Wet/oil screw compressors

Oil-injected screw compressors have much higher power than dry models. Oil in these compressors serves as a lubricant and is injected into the blower and bearings of the machine.

In a wet compressor, a certain amount of oil is used between the screws. Oil compressors consist of a pair of rotors that are tightly paired and installed within a cylinder. However, oil screw compressors also don't need as much cleaning as their dry counterparts.

This model of compressor has two sections for air purification and oil cooling to separate oil from the compressed air, ensuring that the outgoing air is not contaminated with oil; also, the oil does not burn due to high heat. Overall, the role of oil in oil screw compressors is somewhat similar to its role in a car engine. Oil screw compressors typically generate up to 8 bar of pressure, and this number can increase under specific conditions.

Features of the screw compressor

The screw compressor, as one of the widely used technologies in various industries, has a lot to offer customers:

Continuous operation – Air compressors do not require constant turning on and off thanks to their ability to provide a steady air flow and pressure. This means that when using them, there is no need to worry about pressure drops.

Reduced need for continuous maintenance – Since screw compressors have few moving parts, internal wear is minimized. This reduces the servicing and maintenance time involved. On the other hand, all repairs on this equipment are carried out quickly, easily, and hassle-free.

Powerful performance – Screw compressors can operate without issues in challenging conditions such as high air flow and extreme temperatures. These machines effectively power pneumatic tools and heavy equipment.

Low energy consumption – These durable machines generate less heat over time, while saving more energy compared to other tools. This capability will lead to a reduction in energy consumption in the long term.

Low noise – The quiet operation of these devices is due to their compact size and the minimal presence of moving parts. This means you can safely use screw compressors in large workshops and even home workshops.

Advantages of screw compressors

Screw compressors have the advantage of not needing suction or discharge valves compared to reciprocating types. In comparison with centrifugal compressors, the issues and failures related to screw types are less severe, and this type of compressor is very durable and requires minimal repairs.

Since screw compressors are designed for oil injection, they have little resistance to liquid pressure; however, constant liquid exposure can cause problems.

A large portion of the heat generated during compression in a compressor is absorbed by the oil. This feature is essential for preventing excessive pressure in desirable gases; because overheating can lead to polymerization or explosion. By using oil, this additional heat can be managed, allowing these types of air compressors to be used in various industrial applications.

Single screw or twin screw model?

In another classification, screw compressors include two models: single screw and twin screw. The term "screw" refers to the rotating element in the body of the device responsible for the air suction and compression process. Single screw models have lower power compared to twin screw models. Also, it's interesting to know that twin screw models use an interlocking space for the screws; their arrangement and rotation shape increase the machine's power.

Price of screw compressors

Naturally, the greater complexities of twin screw compressors make their purchase price and maintenance costs higher compared to single screw models.

Buying a screw compressor

As mentioned earlier, the price of screw compressors is significantly lower than similar devices, which is why many people are seeking to use them. Among the factors influencing the price of this device are aspects like tank capacity, manufacturing brand, motor power, single or twin screw, oil or oil-free version, dimensions, etc. If you are looking to buy a screw compressor for your business, contact the consultants at Pars Vacuum.

Other products of this Company

Liquid ring compressor

screw compressor

Vacuum pump or vacuum pump

Blower air or air blowing and sucking device