Different Types of Air Compressor
Once you are clear on the type of air compressor you are going to use, your next choice will be to pick between rotary screw compressors, VSD compressors, and other centrifugal compressor options.
The good news is that picking them is simple when you know what to use them for and whether you need a continuous or intermittent duty cycle. To help, we’ve shared our guide to picking the best air compressors based on your needs.
Table of Contents
Considering Your Air Compressor Types
Before you can choose the best air compressor for your needs, it’s important to have a good grasp of the following considerations:
- What you need it for
- Any specific industry requirements that you need to adhere to
- What air pressure ranges do you need access to
- How much usage your air compressor will get
- The quality of the air compressor output
- Any future plans you have for expansion
Once you have all this information to hand, you can then start searching for the best air compressors for your specific needs.
- Piston Air Compressors
Reciprocating or piston air compressors are a classic and time-tested technology in the compressed air industry. They operate by using a piston within a cylinder to draw in air, compress it, and then discharge it at a higher pressure. This process is similar to how a car engine works, but instead of igniting fuel, it focuses solely on compressing air.
Piston compressors are known for their simplicity, durability, and lower initial cost compared to other compressor types. They are relatively easy to maintain and repair, making them a popular choice for smaller workshops, garages, and applications with intermittent air demand.
Piston compressors deliver pressure ranges from 7 bar (100 psi) to 30 bar (450 psi), meeting the demands of many standard industrial applications, including power tools and spray painting.
That being said, these compressors are inherently less efficient than the other compressors on this list. This is primarily due to their reciprocating motion, which creates friction and heat. They can also be noisy and produce pulsating air, which generally require additional filtration or dampening for certain applications. Additionally, their capacity is generally lower than that of other compressor types, making them less suitable for high-volume demands.
Piston compressors are well-suited for smaller operations with intermittent air usage, such as automotive repair shops, tire inflation, and DIY projects. Their simple design and lower cost make them an attractive option for businesses and individuals who don’t require high volumes of compressed air. However, they might not be the most efficient or quiet choice for continuous operation or applications sensitive to pulsation.
- Rotary Screw Compressor
Rotary screw air compressors are positive displacement compressors that utilise a pair of helical rotors to compress air. They are widely regarded as the workhorses of the compressed air industry and are the most popular for applications with constant air demand.
They are available in both oil-injected and oil-free versions, catering to diverse industrial needs. Oil-injected models are generally more efficient and durable, while oil-free versions are preferred in applications requiring clean, contaminant-free air.
Modern rotary screw compressors also feature integrated variable speed drive (VSD) technology, which allows for dynamic adjustments to energy consumption based on demand.
The primary advantages of rotary screw compressors lie in their reliability, efficiency, and relatively low maintenance requirements. They’re also pretty quiet, so they’re suitable for environments where noise pollution is a concern.
However, rotary screw compressors typically have a higher upfront cost compared to reciprocating compressors. Their efficiency decreases at lower loads, making them less ideal for intermittent use. Also, while they can handle a range of pressure requirements, they are bad at changing their PSI in real-time.
Rotary screw compressors are everywhere in industries like manufacturing, construction, automotive, and food processing, where their reliability, efficiency, and continuous airflow are crucial. Their versatility and ability to handle a wide range of pressures and flow rates make them a popular choice for diverse industrial applications.
- Centrifugal Compressors
Centrifugal compressors are dynamic machines that increase air pressure by accelerating it through a spinning impeller and then slowing it down. They excel in large-scale industrial settings where high volumes of continuous airflow are needed. While highly efficient for those uses, they are less suitable for smaller operations.
These compressors are capable of delivering flow rates of up to 18,000 m³/h and pressures exceeding 200 bar, ideal for chemical plants and oil refining.
However, these compressors are quite complex and expensive. They often necessitate specialised filtration and conditioning systems to maintain optimal performance, as they are sensitive to changes in gas composition and inlet conditions. Additionally, the high rotational speeds and tight tolerances demand meticulous maintenance, including regular inspection and cleaning of the impeller and bearings.
Despite these challenges, the benefits of centrifugal compressors often outweigh the drawbacks in large-scale operations. Their ability to reliably deliver high volumes of high-pressure air with minimal energy consumption makes them indispensable in industries like chemical processing, steel production, and power generation.
- Scroll Compressors
Scroll compressors are a type of positive displacement compressor that utilise two spiral-shaped scrolls to compress air. One scroll remains stationary while the other orbits around it, creating crescent-shaped pockets of air that decrease in volume as the scrolls rotate, leading to compression.
Scroll compressors offer unmatched reliability due to their fewer moving parts, reducing the likelihood of mechanical failures.
Scroll compressors are quiet, oil-free, and highly efficient at lower pressures. The absence of oil lubrication ensures clean, contaminant-free air, making them ideal for applications where air purity is critical. Their simple design with fewer moving parts also translates to lower maintenance requirements compared to other compressor types.
The downside to scroll compressors is lower capacity, limiting their suitability for high-volume demands.
Otherwise, they are commonly used in medical facilities, dental clinics, laboratories, and food processing plants where oil-free air is essential. Their quiet nature also makes them suitable for environments like offices, hospitals, and schools where noise disruption needs to be minimised. A fun fact about scroll compressors is that they’re often found in refrigeration and air conditioning systems due to their high efficiency at lower pressures.
- Rotary Vane Compressors
Rotary vane compressors are positive displacement compressors that use rotating vanes to compress air within a cylindrical chamber. They are known for their quiet operation and oil-free options, making them suitable for applications requiring clean air and minimal noise disruption.
Rotary vane compressors excel in delivering consistent airflow and are particularly effective in maintaining stable pressure levels across operations.
Rotary vane compressors are relatively simple, compact, and require less maintenance compared to other types. Their oil-free versions provide clean, contaminant-free air, ideal for sensitive applications like food processing and pharmaceuticals.
The downside is these compressors generally have lower capacities compared to rotary screw or centrifugal compressors, making them less suitable for high-volume demands. Their oil-lubricated versions may introduce oil carryover into the compressed air, requiring additional filtration for applications where clean air is critical.
Rotary vane compressors find their niche in industries and settings that prioritise clean air, quiet operation, and compact size. They are commonly used in medical facilities, dental clinics, laboratories, and certain manufacturing processes where contamination-free air is essential and compactness is welcome. It helps that their quiet nature is best for offices, hospitals, and schools.
- Axial Compressors
Axial compressors are dynamic compressors that compress air in a continuous flow using a series of rotating blades and stationary vanes. They are known for their exceptional efficiency and ability to handle massive air flow volumes. These compressors excel in specialised, high-demand applications like gas turbines, jet engines, and large-scale industrial processes.
Axial compressors achieve compression ratios of up to 30:1 across multiple stages, making them highly efficient for applications requiring high pressures and volumes.
Their unique design, with multiple stages of blades and vanes, allows them to achieve high compression ratios and deliver compressed air at incredible speeds. However, this complexity also makes them costly and intricate, requiring knowledge and maintenance procedures.
While axial compressors play a critical role in industries where massive volumes of compressed air are required, 99% of commercial businesses will be better off with another compressor. These compressors are really only suitable in applications like power generation, aerospace, and large-scale chemical processing.
Variable Speed Drive Technology
Variable speed drive (VSD) air compressors are not really compressors. VSD is more of a “technology” that can be applied on existing compressors to adjust their motor speed to match the demand for compressed air in real-time. This dynamic adjustment contrasts with fixed-speed compressors, which operate at a constant speed regardless of air consumption fluctuations.
The primary advantage of VSD technology is in their energy efficiency. By only consuming the power necessary to meet the current demand, they significantly reduce energy wastage compared to fixed-speed models, leading to substantial cost savings over time.
Modern VSD technology can reduce energy consumption by up to 35% compared to fixed-speed systems, making them an excellent choice for businesses prioritising sustainability.
Moreover, VSD compressors offer smoother operation and reduced wear and tear. The gradual ramp-up and ramp-down of motor speed minimise mechanical stress and strain on the compressor components, extending their lifespan and reducing maintenance needs. While VSD compressors generally have a higher upfront cost than fixed-speed models, the energy savings and reduced maintenance expenses often result in a faster return on investment.
Does your business have a changeable demand for air?
VSD compressors are the best type of air compressor in this situation, as they will work hard to meet the demand you put on them, no matter how large.
To do this, the VSD is able to recognise the level of flow being used and then works to adjust the motor to meet your needs as the airflow increases and decreases. This means less electricity being used on quieter days and energy savings when you need them the most.
Modern VSDs come with new and exciting ways to monitor your use and ensure that you are being truly energy efficient with your use. They can provide your company with data to understand how your operation of the unit is working for you and also show simple ways to avoid expensive maintenance requirements.
Advanced monitoring systems in modern VSD units provide detailed energy consumption and operational efficiency analytics, enabling users to optimise their processes.
At Control Gear, we offer a VSD installation service to help you get the best solution for your needs!
However, if the cost is just too much, then most rotary screw equipment will work just as well. On the other hand, if you know exactly how much air supply you are looking for, fixed speed engine models could be an even better choice. Whatever your needs are, the Control Gear team are here to help and provide you with an installation offer perfectly suited to your needs.
What Are Fixed Speed Compressors?
When considering the type of compressor you need, fixed-speed compressors are perfect when you are only ever using your air compressor at one speed.
These compressors are ideal for processes with consistent demand, as they maintain maximum efficiency at constant load conditions.
This could be high-pressure or low-pressure, but it requires you to know what you are looking for.
Fixed-speed compressor capacity is a much better choice if you are in need of a 100% airflow solution.
Other Considerations When Choosing the Right Air Compressors
So far, we’ve shared information about how to pick the right compressors for your specific needs. However, you may still be uncertain about the best way to compress air for your business need or find yourself worried about spending too much or too little.
Take a look at some of the other important factors that you need to consider when looking for compressor capacity and air quality:
Compressor Size
Whether you opt for centrifugal compressors, a rotary compressor or another type of positive displacement compressors, knowing the size you need is important.
Always assess the free air delivery (FAD) and pressure requirements (measured in bar or psi) to match your operational needs accurately.
To do this, you should consider the psi and bar you require—the heavier the work, the bigger the compressor capacity you will need.
You should also consider the free air compressor delivery, which is measured in cubic feet. The quicker you want to get heavy jobs done, the larger the airflow you will need.
Oil Considerations
When you are clear on size, you will also need to consider oil-injected options vs. oil-free compressors to get the right air compressor for your needs.
Oil-injected options use oil to lubricate the system and ensure that friction is kept to a minimum, but this can result in oil particles being found in the compression chamber and oil seals.
Modern oil-injected systems incorporate advanced filtration to minimise carryover, ensuring cleaner air while maintaining efficiency.
Oil-free compressors are better options for food and medical needs as they offer the best air tools and uncontaminated air so that you can be confident that your precious goods are clean.
Types of Air Compressor
Let Us Help Find The Right Type of Air Compressor
If you need help choosing between centrifugal and dynamic compressors or deciding whether a reciprocating compressor would be better than a VSD, our team is here to help!
Get in touch today and we’ll do our best to answer your questions and provide you with competitive quotes for installation and maintenance.