A Simple Guide On Screw Compressors

Thinking about purchasing rotary screw air compressors (RSACs)? This article will help people understand how these things work, what they are used for, as well as how they are properly maintained.

What are RSACs?

It is a type of compressor that uses enmeshed helical screws to compress the gas.Because of the rotation of these screw, the gas inside is under constant pressure. Applications that require a lot of CFM of airflow on a consistent basis use this technology extensively.

For heavy industrial applications like running pneumatic production lines or conveyor systems, this is a common air compression device. Reciprocating compressors use pistons driven by crankshafts to compress the gas.

What are heavy industries? Check out this site for more info.

How do these things work?

These things work by forcing air through rotors or rotating helical screws. These two screws interlock as they turn. It creates a series of chambers. As gas is forced through the screws, it is squeezed into smaller volumes. The reduction in volume compresses gas as it moves the chambers. These devices are forms of positive displacement compressors.

The two rotors or screws turn rapidly, powered by the compressor motor. The revolution of the rotors forces gas through the chambers. It creates a vacuum that pulls more gas into the chamber through the compressor intake. As the draft moves through the chambers of the paired screws, it is squeezed into smaller volumes. It results in air compression. The compressed draft exits the screw unit, where it can be dried, captured, used, filtered, and stored.

Types of RSAC: Oil-Free (OF) versus Oil-Injected (OI)

There are two common types of rotary screw air compressors: oil-free and oil-injected.

OI RSAC uses oil to lubricate the rotor unit and make sure it runs smoothly. The oil also helps cool compressed gases and prevent overheating the devices. Compressing the draft then passing it through a separator to remove the oil is the standard procedure. An in-line filtration system can reduce the amount of oil that is left in the compressed draft. OI compressors are one of the most common types of RSACs and work well with a lot of applications.

A OF compressor uses a two-stage compression process. The air passes through the intercooler between compression stages to help bring the temp down and prevent the device from overheating. These things eliminate oil carryover. It produces a very clean draft. But they tend to be pretty expensive, more complex to maintain, and a lot noisier compared to their OI counterpart.

What are intercoolers? Visit https://www.enginebasics.com/Advanced%20Engine%20Tuning/Intercooler.html to find out more.


RSAC accessories

A complete system will include a number of components in addition to the compressor itself.


Hot and compressed drafts coming out of the compressor will contain moisture. For most apps, it is desirable to remove these moistures from the draft to make sure that there is enough supply of dry and clean gas for industrial processes.

Refrigerated dryers remove moisture from air by cooling compressed drafts to the point where water condenses out of the air. It can lower the dew points of the compressed draft to -38°F, which is enough for most apps, It’s the standard for drying RSACs and widely available. Desiccant dryers remove water vapor from the draft using absorptive materials.

As opposed to refrigerator dryers, these items are more costly. Still, they will get gases much dryer – at least down to a dew point of negative forty degrees Fahrenheit to negative one hundred degrees Fahrenheit. These things are used for apps needed ultra-dry drafts.

Receiver tanks

These devices store compressed gases after it leaves the compressor. Depending on your setup, you can put the tank either before or after the dryer.

Drain valves

These valves are used to remove residual water from the system. When compressed gas comes out of the RSAC, it is pretty hot – and hot drafts can hold more moisture compared to cold ones. As the draft cools back down to a manageable atmospheric temp, excess water will fall out of the gas as condensation. The compressor, receiver tanks, dryers, air pipes, and other parts of the system that may collect water are all equipped with drain valves to allow for their removal.

Advantages of RSAC

RSACs are the most common types of screw compressors for industrial apps – and there is a good reason for it. These devices are the workhorses of the industrial industry: quiet, reliable, powerful, and energy-efficient. High-traffic apps that require a steady stream of drafts can benefit from using one of these devices. The advantages of using these things include the following:

Cleaner air

RSAC delivers a very clean draft with a pretty low carryover. Oil-injected RSCs will have an oil carryover of negative three PPM. These devices have no carryover to slow down the operation.

Quiet operation

Is RSAC quiet? Compared to other alternatives, the answer is a resounding yes. When compared to the noise made by moving pistons, the operation of these screws is much less audible. These devices may also have an enclosing that can dampen sound. A typical RSAC will operate at sixty-five to seventy-five decibels A (dBA) or between the noise levels of car engines and vacuum cleaners. RSAC will also produce less vibration.