Types Of Air Compressors: A Complete Overview

Air compressors are used in many industries, but in the USA alone, there is a 70 percent dependence placed upon air compressors. These machines are powerhouses built to serve many purposes. With so many use cases comes an array of types. Unless you are an industry expert, finding the right one might be difficult for you. We’re going to sort through all the types of air compressors to give you the most comprehensive overview.

Air Compressors And Their Use Cases

Known for their versatility, air compressors are used mainly to increase the pressure of air by reducing its volume. This creates a powerful action of the air compressor exerting a great amount of air. The pressure of the air does the work it was assigned to. These machines can be found in industries ranging from construction to food and beverage and everything in between.

So as we can understand, compressed air is a hidden powerhouse that drives countless processes across different sectors.

Now that we have a clear picture of what an air compressor is and what it does, let us categorize air compressors.

The Main Types Of Air Compressors

To best understand how air compressors work, you must know that there are two broad categories that compressors fall into: positive displacement type compressors and dynamic compressors.

Positive displacement compressors give the user a constant flow of air without any regard to outlet pressure.

A dynamic compressor sucks air from the outside, rather than using an inbuilt storage tank.

Axial Flow Compressors

The axial flow compressor falls under the dynamic type of compressor. Operating at about 10,000 RPM, this makes them suitable for jet engines, ship engines, and small-scale power stations that require speed.

Axial compressors work similarly to a fan pushing air forward. Air comes in one end and is pushed out the other by spinning blades. These compressors are great for moving large amounts of air quickly with a minimal pressure increase.

Centrifugal Compressors

Centrifugal compressors are another dynamic type of compressor known for their high flow rates, which can range from 1000 cfm to about 1000,000 cfm. These compressors are used in industries like chemical & petroleum processing and automotive industries.

The mechanism of the air compressor is such that the air sucked is into the center of the wheel and then thrown outwards by the spinning blades. This makes the air move faster and faster, and as it slows down it turns into pressure.

Reciprocating Compressors

Compared to the two above, the reciprocating compressor is a positive displacement compressor. This compressor works a bit differently than the other two; the main “unit” of this compressor is a piston mechanism that works to suck in air and then compress it. These are more robust, with abilities to handle higher pressures which sometimes exceed 30,000 psi, making them ideal for oil refineries or gas processes.

Additionally, a subtype of this compressor, which contains a similar working mechanism, would be the diaphragm compressor. This air compressor uses a flexible membrane, which is called the “diaphragm” due to its similar characteristics to the medical term of diaphragm.

The following part then separates the compressed air from the mechanical outputs. In terms of handling certain gases and if you desire an air compressor with reduced maintenance, this might be something to explore.

Rotary Compressors

Rotary compressors are positive displacement type compressors. These compressors can handle flow rates up to 300 kh/s and utilize two interlocking rotors that rotate and efficiently compress air. This style of air compressors has two common types which include rotary screws and rotary vane compressors.

Rotary screw compressors employ intermeshing screws to trap and compress air, while rotary vane compressors use vanes that rotate within a cylindrical housing to achieve compression. These compressors offer smooth operation, high efficiency, and low noise levels.

Air compressors after a certain time require maintenance, part of that being lubrication. Choosing the correct type of air compressor for your needs is important for the most optimal experience of having compressors that last long. For heavier industrial applications, it is important to understand the two variations of compressors which are lubricated and oil-free air compressors.

Oil Air Compressors

Known by names such as oil-flooded compressor or lubricated air compressor, this type is well suited for high-intensity industry-level applications. These compressors use various oil-based lubricants to cool the air compressor and smooth the wear and tear that occurs due to the friction of gears.

The oil’s job is not only to act as a coolant when machines get overheated but can also be used as a sealant, trapping unwanted contaminants in the air. Often used in industries where oil contamination isn’t a concern, these machines are designed to need as little maintenance as possible.

Oil-Free Air Compressors

Oil-free compressors use alternative methods for sealing and cooling, such as water or Teflon-coated components. These types of compressors are suited for applications where contamination of oil in the air would pose a great risk.

Used in industries that manufacture food and drinks, electronics, etc., they require less maintenance and are more compact. These types of air compressors might be expensive upfront but they make up for the price with the lack of frequent oil changes and less maintenance required in general.

Now that we have understood the differentiation between each of the compressors, being oil-free and oil compressors, let us gain in-depth knowledge regarding a very interesting type of air compressor which is the rotary air compressor.

Rotary Air Compressor (An In-depth View)

As we have understood, rotary air compressors are positive displacement machines, which means that this gives a user a constant source of airflow. These kinds of machines run using rotating elements as the name suggests. The combination of the airflow and the gear mechanism makes them efficient in an industrial setting. This type of air compressor divides into two more types which are further divided into two more subtypes of a rotary screw:

Rotary Vane Air Compressor

The rotary vane compressors consist of a rotor with slots that hold sliding vanes. As the rotor spins, centrifugal force pushes the vanes against the casing, trapping and compressing the air in chambers of varying sizes. These compressors are known for their durability, low noise levels, and steady air output.

They are commonly used in applications requiring a consistent air supply, such as in automotive service stations, refrigeration, and HVAC systems. Rotary vane compressors are also relatively easy to maintain, making them a popular choice for small to medium-sized industries.

Rotary Screw Air Compressor

Compared to the vane system, the rotary screw uses two helical screws (rotors) that rotate in opposite directions to compress air. As the rotors turn, air is trapped between the threads and compressed as the space between the rotors decreases.

Rotary screw compressors are highly efficient, quiet, and suitable for continuous-duty applications, making them a staple in large industrial plants, manufacturing facilities, and construction sites.

A common subtype of the rotary screw compressor is the lobe and liquid ring air compressor.

Lobe Air Compressor

This compressor uses intermeshing lobes instead of screws to compress air. These lobes rotate in opposite directions, trapping air and compressing it as it moves from the intake to the outlet.

While lobe compressors are generally less efficient than screw compressors, they are robust and reliable, often used in applications where contamination is a concern, such as in food processing or pharmaceutical industries.

Liquid Ring Air Compressor

Another subtype of rotary screw compressors is the helical screw air compressor. Distinguished by the shape of its rotors, the helical design allows for smoother, more efficient compression, reducing energy consumption and noise.

These compressors are often used in high-demand industrial applications where reliability and continuous operation are crucial, such as in manufacturing, mining, and large-scale refrigeration.

Depending on specific requirements and applications, other types of air compressors may be more suitable. To ensure you have a comprehensive understanding, let’s delve into these other types of air compressors, to understand each of their unique features.

Helical Screw Air Compressor

The helical screw air compressor is a variant of the rotary screw compressor, distinguished by the shape of its rotors. The helical design allows for smoother, more efficient compression, reducing energy consumption and noise. These compressors are often used in high-demand industrial applications where reliability and continuous operation are crucial, such as in manufacturing, mining, and large-scale refrigeration.

Portable Air Compressor

Portable air compressors are compact, lightweight units designed for mobility and ease of use. They are commonly used in construction, home improvement projects, and emergency repairs, providing a convenient source of compressed air wherever needed.

Despite their small size, they can be quite powerful, offering sufficient pressure and airflow for a wide range of tools and equipment.

2-Stage Air Compressor

A 2-stage air compressor compresses air in two stages for higher efficiency and greater pressure output. In the first stage, the air is compressed to an intermediate pressure and then cooled before entering the second stage, where it is further compressed to the desired pressure.

This design is ideal for applications requiring high-pressure air, such as in automotive repair, manufacturing, and heavy-duty industrial processes.

3-Stage Air Compressor

Similar to the 2-stage design, a 3-stage air compressor compresses air in three stages, with each stage progressively increasing the pressure. After each stage, the air is cooled to reduce the temperature and improve efficiency. These compressors are used in extremely high-pressure applications, such as in power plants, large-scale manufacturing, and oil and gas exploration, where reliability and durability are paramount.

Multi-Stage Air Compressor

A multi-stage air compressor can have more than three compression stages, allowing for even higher pressures and improved efficiency. These compressors are typically used in specialized industrial applications where ultra-high pressure is required, such as in aerospace, chemical processing, and deep-sea exploration. They offer precise control over pressure and are built to handle demanding conditions over extended periods.

Scroll Air Compressor

Compressors that use two interleaved spiral elements, one stationary and one orbiting, to compress air are known as Scroll air compressors. As the orbiting scroll moves, it traps and compresses air in small pockets.

These compressors are known for their quiet operation, low maintenance requirements, and high efficiency. They are often used in refrigeration, air conditioning, and cleanroom environments where noise and vibration must be minimized.

V-Shaped Air Compressor

A compressor with an interesting design is the V-shaped air compressor which features two cylinders arranged in a V configuration. The specialty of this design is that it balances the load on the crankshaft, reducing vibration and wear.

V-shaped compressors are commonly used in automotive and industrial applications where durability and consistent performance are needed. Their compact design allows for easy integration into various setups, making them a versatile choice for many users.

Key Factors To Consider When Buying An Air Compressor

Now that we have encompassed the many types of air compressors, here are a few things to remember when purchasing an air compressor.

Purpose And Application

• Industrial vs. Home Use: Determine if you need the compressor for industrial tasks (e.g., automotive repairs, construction) or home use (e.g., inflating tires, small tools). Industrial applications require more powerful and durable compressors.

Compressor Type

• Single-Stage vs. Two-Stage Compressors: Single-stage compressors are suitable for light-duty tasks, delivering air at one pressure stage. Two-stage compressors are more efficient for heavy-duty tasks, providing higher pressures and consistent performance.
• Oil-Lubricated vs. Oil-Free: Oil-lubricated compressors are more durable and quieter but require regular maintenance. Oil-free compressors are maintenance-free but tend to wear out faster.

Power Source

• Electric vs. Gas-Powered: Electric compressors are quieter and suitable for indoor use, while gas-powered compressors offer more mobility and are better for outdoor or remote work where electricity is unavailable.
• Voltage Requirements: Ensure the compressor matches the voltage available in your workspace. Most home-use compressors run on 110-120V, while industrial models may require 220-240V.

Tank Size

• Capacity: Tank sizes range from 1 to 80 gallons or more. Larger tanks store more air, allowing for longer continuous use without the motor running, which is crucial for tasks requiring a constant air supply.
• Consideration For Portability: Smaller tanks (up to 6 gallons) are portable and sufficient for intermittent use, while larger tanks are bulkier but better suited for continuous or heavy-duty tasks.

CFM And PSI Ratings

• CFM (Cubic Feet Per Minute): Indicates the volume of air the compressor can deliver. Higher CFM ratings are necessary for tools requiring more air, such as sanders or grinders. A general range is 2-5 CFM for light tasks, while industrial tasks may require 10+ CFM.
• PSI (Pounds Per Square Inch): Refers to the pressure the compressor can generate. Most tools operate at 90-100 PSI, but some applications may require higher PSI.

Portability

• Portable vs. Stationary: Consider whether you need a portable compressor for moving between job sites or a stationary unit for a dedicated workspace. Portable models are typically smaller with wheels, while stationary models offer higher capacities and power.

Noise Level

• DB Rating: Noise levels are measured in decibels (dB). Compressors can range from 60 dB (quiet) to over 90 dB (loud). Consider the working environment and choose a quieter model if noise is a concern.

Duty Cycle

• Continuous vs. Intermittent Use: The duty cycle indicates how long the compressor can run before needing to cool down. A 50% duty cycle means the compressor can run for 5 minutes out of every 10. For industrial use, look for a higher duty cycle (75% or more).

Budget And Cost Of Ownership

• Initial Cost: Prices vary widely, from around $100 for basic models to $1,000+ for industrial-grade compressors. Determine your budget based on your needs and how often you’ll use the compressor.
• Maintenance And Operating Costs: Consider the long-term costs, including electricity, gas, oil, and replacement parts. Oil-lubricated models may have higher maintenance costs but last longer.

Brand And Warranty

• Reputation: Choose reputable brands known for quality and reliability. Brands like Ingersoll Rand, DeWalt, and Campbell Hausfeld are well-regarded in the market.
• Warranty: Look for a warranty that covers at least one year of use. Longer warranties (3-5 years) are preferable for industrial-grade compressors.

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