Jul. 07, 2025
Is a rotary screw air compressor right for you? Screw compressors are the workhorses of industry and manufacturing. These tough industrial air compressors are widely used for applications requiring high efficiency and continuous airflow, including conveyor systems, manufacturing equipment, process manufacturing, and more.
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Our complete guide to rotary screw compressors will help you understand how these compressors work and decide whether a screw compressor is the right choice for your application. Plus, how to install and maintain your compressor system for optimal performance.
A rotary screw air compressor (sometimes called a “twin-screw compressor”) is a type of air compressor that uses a pair of enmeshed helical screws to compress air. As the screws turn, the air is continually compressed. Screw air compressors are widely used for applications that require high CFM (Cubic Feet of air per Minute) and continuous use. This is the most commonly used air compression technology for heavy industrial applications such as powering pneumatic production lines and conveyor systems.
They can be contrasted with a reciprocating air compressor, which uses pistons driven by a crankshaft to compress air.
Read more: Reciprocating vs. Rotary Screw Air Compressors: What’s the Difference?
A rotary screw air compressor works by forcing air through a pair of rotating helical
screws (or rotors). The two rotors interlock as they turn, creating a series of chambers. As air is forced through the rotors, it is squeezed into a smaller volume. This reduction in volume compresses air as it moves the chambers. A rotary screw air compressor is a form of positive displacement compressor. The compression process is continuous and controlled by a drive motor and a system of inlet and discharge valves.
There are two basic kinds of rotary screw air compressors: oil-injected and oil-free. Oil-injected screw compressors are the most common type of industrial air compressor and work well for most applications. Within these categories, there are also some subtypes to consider.
Read more: Why Choose or Upgrade to a Variable Speed Drive Air Compressor?
An oil-injected (or oil-flooded) rotary screw air compressor uses oil to lubricate the screw unit and ensure its smooth operation. The oil also helps to cool the compressed air and prevent overheating of the unit. After the air is compressed, the oil is removed using an oil separator. A small amount of oil may be left in the compressed air (oil carryover), which can be further reduced using inline filtration.
An oil-free (or oil-less) rotary screw air compressor uses a two-stage compression process. Air passes through an intercooler between compression stages to bring temperatures down and prevent overheating. Oil-free rotary screw air compressors eliminate any oil carryover, producing very clean air. However, they tend to be more expensive, more complicated to maintain, and noisier than their oil-injected cousins. Oil-free screw compressors are most commonly used for specialty applications requiring very high-purity air. However, in most cases, it is possible to obtain the required purity levels using dryers and air filtration.
Read more: Do You Need an Oil-Free Compressor? Probably Not.
These are the basic components of a rotary screw air compressor.
The air-end is where the work of air compression happens inside the rotary screw air compressor. The air-end consists of several component parts.
A rotary screw air compressor must have several other components in addition to the air-end.
Read more: How to Adjust the Air Compressor Regulator.
Filters keep contaminants out of the air supply. Filters for a rotary screw air compressor may include:
Read more: What Type of Filtration Does Your Air Compressor Need?
Rotary screw air compressors generate a lot of heat during compression. This heat must be dissipated by a cooling system to prevent overheating. An aftercooler acts as a heat exchanger, absorbing heat from the compressed air and carrying it away where it can be dissipated. The aftercooler cools air and removes the majority of the moisture before it goes into the drying system and filters. There are two basic types of air compressor after-coolers: air-cooled and water-cooled.
Most screw compressors are air-cooled. Air-cooled rotary screw compressors use a series of coils that are cooled by a fan. Cooling fins provide additional surface area for air to move across, increasing the heat transfer capacity.
Water-cooled rotary screw compressors use water (or, sometimes, another liquid) to carry away excess heat. Water-cooled aftercooler system options include:
An oil-injected (or oil-flooded) rotary screw air compressor will have additional components as part of the oil injection system.
A complete compressed air system will include a number of other components in addition to the air compressor itself.
Hot, compressed air coming out of the air compressor will contain excess moisture. For most applications, it is desirable to remove moisture from compressed air to ensure a supply of clean, dry air for industrial processes. There are two basic types of compressed air dryers.
Read more: Refrigerated vs. Desiccant Air Dryers — How to Choose a Compressed Air Dryer.
The air receiver tank (or compressed air storage tank) stores compressed air after it leaves the air compressor. The air receiver tank may be placed either before or after the air drying system.
Read more: Air Receiver Tank Full Guidelines
Drain valves are used to remove excess liquid water from the compressed air system. When compressed air comes out of the rotary screw air compressor, it is very hot — and hot air can hold more moisture than cold air. As the air cools back down to atmospheric temperatures, excess liquid will fall out of the air as condensation. Drain valves are used to drain excess liquid out of the air compressor, air receiver tanks, air dryers, compressed air piping, and other parts of the system where liquid may accumulate.
Before selecting a rotary screw air compressor, make sure it is the right choice for your application. Here are five important questions to ask when making your decision.
Rotary screw air compressors are especially durable and are able to handle large amounts of demand for extended periods of time. They are still more efficient and durable than piston compressors, even at smaller sizes, but the efficiency benefits are most noticeable when getting into larger demands (i.e., 15 HP and more). Rotary screw air compressors are designed to run at 100% duty cycle, day in and day out.
While a rotary screw compressor may have higher air compressor maintenance costs and/or initial capital costs, its life expectancy is much greater than a piston-type air compressor. Piston-type (reciprocating) compressors typically last about 10,000 - 20,000 hours before a rebuild is necessary. On the other hand, a rotary screw compressor will last between 80,000 - 100,000 hours. Rotary screw compressors are known for their reliability and longevity.
Rotary screw air compressors are known for their quiet operation. Since most rotary screw air compressors come standard with sound-dampening enclosures, they generally operate between 65 – 75 dBA, which is much lower in comparison to other types of compressors. For comparison, a reciprocating or piston-type air compressor can operate at around 80 – 85 dBA.
Rotary screw air compressors are designed to have no more than 3 PPM of oil carryover, while piston compressors can have 10 PPM or more as they age. Less oil carryover means that you have to change your filter elements less often, therefore decreasing compressor maintenance costs.
Rotary compressors have become more and more popular because of their efficiency and their ability to keep up with constant high demand. Many rotary screw compressors are used 24/7.
Even if you don’t have a constant demand, rotary screw reliability, and durability come in a variable-speed drive version. A VSD compressor will speed up and slow down in relation to your demand at any given moment. This option should definitely be considered if your demand varies, because yesterday’s controls — including online/offline, modulation, and even turn valves — have proven to be costly when compared to the benefits of a VSD.
Rotary screw air compressors are the most popular type of air compressor for industrial applications — and for good reason. These air compressors are the workhorses of the industry: reliable, quiet, energy-efficient, and powerful. They are an excellent choice for high-volume applications requiring a continuous supply of air.
Rotary screw air compressors are used across many industries that require high CFM or continuous airflow (100% duty cycle), including manufacturing, food processing, pharmaceuticals, processing plants, paint lines, packaging lines, and much more. These industry staples provide a reliable source of compressed air for many applications in manufacturing and industry, from powering equipment to pneumatic conveying, to process air.
Read more: Top 10 Industrial Compressed Air Applications.
Many manufacturing facilities rely on screw compressors to power production equipment, conveyors, and packaging lines. Rotary screw compressors provide consistent airflow and pressure for robotic production applications in manufacturing sectors such as automotive, aerospace, and general fabrication. Manufacturing plants also use compressed air to lift and move heavy parts and power manual tools. Other applications in manufacturing include:
Process industries, including chemical manufacturing and pharmaceutical manufacturing, rely on rotary screw compressors for both process air and to power machinery and conveyors. Air for pharmaceutical and process industries may need to meet very strict standards for purity. Screw compressors can be used to power applications such as:
Food and beverage manufacturers may use screw compressors in a variety of ways, from product blow-off and cleaning to packaging lines. A rotary screw compressor provides consistent and reliable air for food and beverage applications, including:
While small family farms may be more likely to use a reciprocating or piston compressor, large-scale commercial farming can benefit from the high efficiency and high CFM of a rotary screw compressor. Applications for screw compressors in farming include:
Rotary screw compressors are widely used throughout the energy sector for a variety of purposes. In the oil & gas industry, screw compressors are used to power drilling equipment and pneumatic systems for transporting drilled oil. Compressed air may also be used to power equipment for compressing natural gas and refining petroleum. Other uses in the energy sector include:
What kind of maintenance is required for a rotary screw air compressor? Rotary screw air compressors require regular inspection and maintenance to operate at peak performance and protect the system from excessive wear and tear. Check your owner’s manual for specific guidelines for your make and model of rotary screw air compressor. Air compressor maintenance tasks may include:
Read more: Maintaining Your Air Compressor.
Checking and changing the oil is one of the most important maintenance tasks for an oil-injected rotary screw air compressor. Depending on your compressor model and the type of oil used, you can expect to change the oil every 4,000 – 8,000 hours. However, if your rotary screw air compressor is operating in a dirty environment, the oil may need to be changed more often. Check oil levels and inspect oil for contaminants at least weekly. At least once a year, oil should be completely drained and flushed. Always replace your oil filter after flushing.
Air compressor filters (including air intake filters and inline filters) should be changed at a minimum every 2,000 hours for a rotary screw air compressor. If your environment is very dirty, you may need to change filters more often.
Water should be drained for a rotary screw air compressor at least daily, if not more often. To reduce maintenance time, look for automated drain valves. Electric drain valves can be set to open on a timer to drain condensate regularly. A zero-loss drain valve uses a float mechanism to activate the drain, so it only opens when needed. This can reduce compressed air loss.
Proper compressor installation is very important for a screw compressor. There are several factors to consider for installation of a rotary screw compressor.
Want more information on integrated variable speed screw air compressor? Feel free to contact us.
The experts at Fluid-Aire Dynamics can help you select the best rotary screw air compressor for your application. Choosing a rotary screw air compressor depends on your airflow requirements, production processes, and budget. Contact us for help in choosing the best compressor for your needs.
All in all, rotary screw compressors today have become popular because of their efficiency, noise level, and the fact that the cost for this type of compressor has dropped significantly in the last ten years. They have low oil carryover and are durable and reliable. They come in VSD for applications with varying demands throughout the day. Rotary screw compressors are a worthwhile investment for any manufacturer looking for a good quality, overall cost-effective unit.
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In this rotary screw air compressor buying guide, it's all about the workhorse of many industries: the rotary screw compressor. Rotary screw compressor can supply compressed air 24 hours a day, 365 days a week, if necessary. In this buying guide, I will reach you everything you need to know when buying a rotary screw air compressor. If you are still not sure whether a rotary screw compressor is the right choice for you, be sure to start at the air compressor buying guide main page. Are you looking for a reciprocating compressor? Visit my reciprocating compressor buying guide instead.
Do you want to be sure you buy the right air compressor, the air compressor that is right for you and your situation? Don’t worry, I am here to help you.
In this buying guide I will teach you:
Rotary screw air compressors are perfect for:
But... I have seen a lot of business that bought a rotary screw compressor, where a reciprocating compressor would have been better (they listened to the salesman who sold them the biggest machine they could). If any of the following applies to you, a rotary screw compressor is not for you:
In these cases, a reciprocating air compressor would be a better choice. ## How to choose the right capacity and pressure for your new rotary screw air compressor.
It is very important to buy a compressor that can supply you with enough amounts of compressed air, at the right pressure. Unforatunately, most people don't know exactly what they need, and end up buying a too big or a too small air compressor. Let me help you.
If you buy a rotary screw compressor, it is usually for one of the following reasons:
For each of the above cases, here is how to easily determine the right pressure and capacity for you:
1. This is your first air compressor
Check the manuals or spec sheets of your pneumatic equipment. It should tell you the pressure at which the equipment operates and the amount of air it needs. The part that needs the highest pressure dictates the required pressure. Add 1.5 bar to to minumum required pressure to account for pressure drop and load-unload differential of your air compressor. Now, add up the air consumption of all your equipment. This is the capacity of your air compressor.
It's a good idea to buy a bigger air compressor, but not too big. Rotary screw compressors don't like standing still. Keep in mind that some equipment state the 'average consumption', while other equipment state the 'maximum (or peak) consumption').
2. It's a replacement for an old rotary screw compressor
Check the current pressure and capacity of your old compressor. If your old compressor was adequate, buy a new compressor of the same pressure and capacity. Take a moment to decide whether is a good idea to buy a (slightly) bigger compressor, to account for future expansion of your business.
3. You now have a reciprocating compressor, but need more capacity (cfm).
Check the pressure at which your current compressor is set. Don't look at the maximum pressure of your current reciprocating compressor, as this is often much higher than the pressure needed to operate your machinery. If you want to replace the compressor, check the capacity of your current compressor. Now you know you need a bigger compressor than this. How much bigger? It depends on the tools/equipment you added that made your old compressor too small.
Also keep into account future expansion of your business when determining the right capacity. If you want to add the screw compressor as an additional compressor, keep in mind that rotary screw compressors don't like standing still for a long time. It makes them old and rusty. Always make the rotary screw compressor your primary compressor and the reciprocating compressor your secondary/backup compressor. Rotary screw compressors are more energy efficient anyway.
4. You already have a rotary screw compressor, but need more capacity.
Most of the time, I see people buy the same type or capacity of compressor as the current one. Which is a good idea. It allows you to easily use the two compressors alongside each other, and use one as the backup for the other. Another idea is to buy a bigger compressor and use the old one only as an emergency backup.
You might think about getting a variable speed drive (VSD) compressor to take care of the compressed air need when your first compressor can't keep up. ## Don't be fooled: buy only the options and extras you really need!
Rotary screw compressors come in a large variety of flavors, with many optional extras and options. But what do you really need? Do you need an integrated air dryer? Do you need extra filters? Do you need electronic condensate traps?
Integrated air dryers and filters.
Most rotary screw air compressor manufacturers offer an all-in-one solution. This means you get an air compressor with integrated compressed air dryer and sometimes also compressed air filters. For example, at Ingersoll Rand they call it the "Total Air System" ("TAS" added to the model name), at Alas Copco they call it "Full Feature" ("FF" added to the model name).
For most systems, a compressed air dryer is highly recommended. Same goes for compressed air filters. Compressed air is wet and dirty by nature. Oily too, with oil lubricated compressors. Clean compressed air saves your equipment from premature failure. Keep in mind that all compressed air dryers and filters create and addition pressure drop in the system. This means addition energy costs (to overcome the pressure drop). This extra energy cost can run into the hundreds or thousands of dollars over the lifetime of the compressor.
Something to keep in mind.
Electronic condensate traps (instead of fully mechanical ones)
Do you need it? Not really. Is it better? Yes. A dirty, clogged and non-functioning (mechanical) condensate trap (the one with the floater), is maybe the number 1 maintenance issue with air compressors.
A non-functioning condensate trap will result in lots of water in your compressed air system. However, if you manually drain or check the drain on your air receiver every day / week, you will quickly discover when your air compressors condensate drain stops working. But, if you're like most people and don't want to check on your compressor every day, an electronic condensate drain is a good idea.
An electronic condensate drain can always be installed afterwards if you don't want to fork out the cash right now.
Variable speed drive (VSD)
A variable speed drive compressor matches the output capacity to the actual demand. In simple terms, it simple let's the compressor run faster or slower, depending on the current pressure. A VSD compressor is often advertised as the one and only way to save energy. This is true, but not always.
While it is true that a VSD compressor can save you huge amounts of energy, it is not always the case. A VSD compressor is NOT a good choice when:
A VSD compressor IS a good choice when it runs at 50 - 80% load. This is where the money-saving is. PLus it allows the compressor to heat up, which will prevent lot's of maintenance issues.
Belt drive or direct drive
Personally I would choose direct drive. Belt drive units are usually more compact, but are more noisy and in my experience require more maintenance (on the pulleys and belts), especially in dusty environments.
Aftercoolers
On most stationary screw compressors, an aftercooler in standard. I would always choose to have an aftercooler anyway. Without the aftercooler, the compressed air leaving your compressor would be around 80 - 100 degrees, which is too hot to fed into most air dryers, air piping or air tools.
Besides that, the aftercooler removes huge amounts of water from the compressed air. If you don't have an aftercooler, all this water stays in the compressed air (as gas) and condensates when it cools (in piping system, tools, equipment.) ## Energy: the single biggest expense
Most people buying an air compressor don't realize that the purchase of the compressor is just the beginning. Over the lifetime of the compressor, the purchase cost is only 10%. Another 15% is maintenance and spare-parts and w whooping 75% is energy cost.
If you have a choice between two otherwise comparable air compressors. Always choose the most energy efficient one. In can save you thousands of dollars per year. Unfortunately, most of the time this goes unnoticed. Even if the more energy efficient compressor is more expensive, I would still prefer it over a less energy-efficient one. I
n 10 years time, the payback will be huge, you can buy a brand new compressor just from the savings!
Everywhere you look online, you will see the same makes and models of rotary screw air compressors pop up. The main competitors are Quincy, Atlas Copco, Ingersoll Rand, Chicago Pneumatic. Sometimes you will see the odd cheap rotary screw manufacturer listed, but I would stay away from those and choose one of the established brands.
The difference between the series are usually the size range (HP / Capacity), or the maximum pressure. Some manufacturers have series for 'heavy duty' use, or 'high efficiency' use. The real difference between the series is sometimes hard to see. I'm sure some is only for marketing purposes (wouldn't you like to buy a 'carpenter compressor' when you are a carpenter?)
Inside a series, the difference between the individual models is mostly only the pressure and the capacity. Here's an overview of air compressor manufacturers and their rotary screw series available. I also created an extensive overview of screw air compressors with much more information.
Sometimes it seems like manufacturers or dealers like to confuse you with all their different models, options and extras.
For more information, please visit integrated fixed speed screw air compressor.
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