Types of Air Compressors
Introduction
Compressed air is essential to keeping industry moving. From powering pneumatic tools on construction sites and keeping production lines operational in food and beverage plants, to supporting offshore operations and rail maintenance, air compressors play a critical role across virtually every sector. Reliable compressed air systems help ensure operational efficiency, product quality and safety, especially in environments where even minor contamination can disrupt processes or compromise standards.
In this guide, we’ll explore the main types of air compressors used across industry, highlighting how each works, their advantages and which applications they best suit. We’ll also help you identify the right system for your operation.
Compressor Technology Basics
All air compressors serve the same purpose – to convert power into compressed air – but the way they achieve this varies depending on the underlying technology. Broadly, there are two main categories:
- Positive displacement compressors
These work by mechanically trapping a fixed volume of air and reducing its space to increase pressure. Common examples include reciprocating (piston), rotary screw and scroll compressors. These types are typically favoured for applications that require a steady, continuous flow of air and are valued for their reliability and versatility across a wide range of pressures and capacities.
- Dynamic or kinetic compressors
Dynamic compressors, such as centrifugal and axial compressors, use high-speed impellers to accelerate air and convert that kinetic energy into pressure. They are ideal for large-scale, continuous operations where high volumes of air are needed, for example, in petrochemical plants, power generation and other heavy industrial settings.
Choosing the right compressor type goes beyond capacity. Factors such as air quality requirements, duty cycle, energy efficiency and maintenance expectation all play a role. For instance, a manufacturing line that operates 24/7 demands a different setup to a temporary installation at a construction site. Selecting the correct technology helps minimise downtime, reduce energy consumption and extend equipment life.
Another key distinction lies in whether a compressor is oil-lubricated or oil-free . Oil-lubricated units rely on oil for sealing and cooling, but even with filtration, there’s always a risk of contamination in the compressed air stream. Oil-free compressors, by contrast, eliminate that risk entirely, making them essential in industries such as food and beverage, pharmaceuticals and data centres, where air purity is critical.
This is where Aggreko’s oil-free compressors stand apart. Available in electric and diesel-powered configurations, they deliver 100% clean, dry air that meets the highest purity standards, while offering the flexibility and efficiency required for various applications.
Types of Air Compressors
Air compressors come in several designs, each suited to different operational needs, pressures and duty cycles. The characteristic of each type helps ensure you select the most efficient, reliable and cost-effective system for your application.
Reciprocating Compressors
Reciprocating or piston compressors use a crankshaft-driven piston within a cylinder to compress air. As the piston moves down, it draws air into the chamber; as it moves up, it compresses that air and forces it into a storage tank.
These units are typically used in smaller workshops, maintenance operations or facilities with intermittent air-demand cycles. Their main advantages include relatively low initial cost, straightforward design and the ability to achieve high pressures.
However, they are not ideal for continuous-duty industrial applications. Frequent cycling can generate heat, noise and vibration, leading to increased maintenance requirements and reduced efficiency over time. For operations that require constant air supply, such as manufacturing or process industries, other compressor types are generally a better fit.
Rotary Screw Compressors
Rotary screw compressors are among the most widely used in industrial settings. They use two interlocking helical rotors to trap and compress air as it moves through the chamber. This continuous process produces a steady flow of compressed air with minimal pulsation, making rotary screw compressors well-suited to high-volume, continuous-duty applications.
Oil-free rotary screw compressors replace oil-based sealing and cooling with advanced materials and precision engineering, dramatically reducing the risk of oil contamination. This makes them ideal where air purity is critical. Aggreko’s oil-free screw compressors combine clean air delivery with flexible, dependable performance.
Visit our Product Explorer and select ‘Oil-Free Air Compressors’ to explore Aggreko’s diesel/HVC or electric compressors.
Scroll Compressors
Scroll compressors use two spiral-shaped scrolls – one fixed and one orbiting – to compress air smoothly and continuously. The result is a compact, quiet and efficient compressor that delivers clean, pulsation-free air.
Their simplicity and low vibration levels make them an excellent choice for medium-duty applications where reliability and low noise are important, such as laboratories, healthcare, pharmaceuticals and food production.
Centrifugal Compressors
Centrifugal compressors use a high-speed impeller to accelerate air outward, converting kinetic energy into pressure through a diffuser. These compressors excel in large-scale industrial operations where high flow rates and continuous operation are essential.
Their advantages include high efficiency at large capacities, continuous operation with minimal pulsation and a compact footprint relative to output. However, centrifugal compressors are less effective at lower flow rates and can be more complex to install and maintain, making them better suited to centralised, fixed installations rather than smaller or variable-demand sites.
Portable vs Stationary Compressors
Portable compressors are designed for mobility. Often diesel-powered, they are used in industries such as construction, events, rail maintenance and offshore operations where flexibility and on-site reliability are vital. These units are positioned on wheels can be relocated, providing compressed air wherever it’s needed.
Stationary compressors are fixed installations built into plant systems. Typically electric-powered, they offer higher capacity and efficiency for continuous processes in factories, data centres and other large industrial environments.
Aggreko’s range caters to both needs, offering portable oil-free diesel compressors for, and stationary oil-free electric units . This flexibility enables customers across every sector to access clean, reliable and compliant compressed air, wherever and whenever it’s needed.
Choosing the Right Type of Air Compressor
Selecting the right compressor is about matching the system to your operational environment, duty cycle, air purity requirements and mobility needs. The decision often comes down to whether you need a portable or stationary compressor type, the level or air quality and the power source available on site.
The table below summarises the key sectors Aggreko supports:
|
Sector |
Typical Duty Profile |
Required Air Quality |
Mobility Need |
Preferred Power Source |
Why Oil-Free Matters |
|
Aquaculture |
Continuous aeration and oxygenation |
Clean, dry air |
Stationary or portable |
Electric |
Prevent oil contamination of water systems |
|
Construction |
Intermittent, high-demand tools |
Standard to clean air |
Portable |
Diesel |
Enables mobility and reduces environmental risk |
|
Data Centres |
Continuous cooling, system control |
Class 0 oil-free |
Stationary |
Electric |
Protects sensitive electronics from contamination |
|
Events |
Temporary, variable demand |
Clean, dry air |
Portable |
Diesel |
Reliable, mobile solution for short-term use |
|
Film & TV |
Low-noise, short-term operations |
Clean, quiet air |
Portable |
Electric or diesel |
Quiet and contamination-free air on set |
|
Food & Beverage |
Continuous production |
Sterile, oil-free air |
Stationary |
Electric |
Prevents product contamination and ensures hygiene |
|
Government & Defence |
Variable, mission-critical |
Clean, reliable air |
Stationary or portable |
Electric or diesel |
Supports critical infrastructure without downtime |
|
Healthcare |
Continuous, clean air supply |
Class 0 sterile air |
Stationary |
Electric |
Essential for patient safety and equipment reliability |
|
Manufacturing |
Continuous or batch operations |
Clean, dry air |
Stationary |
Electric |
Ensures product quality and reduces filtration needs |
|
Oil & Gas |
Harsh, continuous duty |
Clean, dry air |
Stationary or portable |
Diesel |
Avoids contamination in sensitive refining processes |
|
Petrochemical & Refining
|
Continuous, large-scale |
High-purity, oil-free air |
Stationary |
Electric |
Maintains compliance and process integrity |
|
Pharmaceuticals |
Continuous precision processes |
Sterile, oil-free air |
Stationary |
Electric |
Prevents contamination of medical products |
|
Rail |
Maintenance and testing |
Clean, reliable air |
Portable |
Diesel |
Supports mobile maintenance without contamination |
|
Shipping
|
On-board or dockside use |
Clean, dry air |
Portable |
Diesel |
Reliable compressed air in marine environments |
|
Utilities |
Continuous supply, large plants |
High-purity, oil-free air |
Stationary |
Electric |
Maintains consistent performance in mission-critical systems |
|
Wind Farms |
Intermittent, remote use |
Clean, dry air |
Portable |
Diesel |
Ideal for remote maintenance and testing operations |
Why Oil Free Matters
The distinction between oil-lubricated and oil-free compressors is one of the most important considerations when specifying an air system, especially in industries where air purity directly affects product quality, safety or operational integrity.
Oil-lubricated compressors use oil to seal, cool and lubricate internal components. While effective, this design can allow oil vapour or aerosols to enter the compressed air stream. Even with advanced filtration, complete removal isn’t always guaranteed. Over time, trace oil contamination can damage sensitive equipment, compromise sterile environments or result in costly product recalls.
By contrast, oil-free compressors are engineered to deliver clean, dry air with no risk of hydrocarbon contamination. Their internal components operate without lubricating oil in the compression chamber, eliminating the primary source of oil carryover. The result is Class 0 certified air quality – the highest standard defined by ISO 8573-1 – ensuring zero risk of oil contamination.
Installation, Operation and Maintenance Considerations
Selecting and operating the right air compressor means aligning performance with the specific needs of your site and process. Before installation, several key factors should be assessed to ensure efficiency, reliability and compliance:
- Duty cycle: will the compressor run continuously, intermittently or during specific shifts?
- Required flow and pressure: what volume of air and pressure levels are needed to sustain your operations?
- Air quality and purity: does your process demand Class 0 oil-free air or are standard levels acceptable?
- Power source: is an electrical supply available or will a diesel-powered solution be required?
- Mobility: do you need a portable unit for site flexibility or a stationary system for fixed operations?
-
Space and installation footprint: how much room is available, and does the environment suit indoor or outdoor placement?
Maintenance and Reliability by Compressor Type
Each compressor design carries its own maintenance profile:
- Reciprocating compressors: robust and simple, but higher maintenance in continuous duty settings due to more moving parts (pistons, rings, valves) and higher vibration/heat.
- Rotary screw compressors: known for reliability and continuous duty performance, they require routine filter and separator changes, particularly in lubricated systems. Oil-free models simplify this by removing oil-related maintenance.
- Scroll compressors: with fewer moving parts and no need for oil changes, scroll units offer low-maintenance, quiet and efficient operation. Ideal for clean environment where uptime and simplicity are key.
-
Centrifugal compressors: designed for high-capacity, large-scale operations, these systems demand more specialised installation, monitoring and maintenance, including alignment, vibration analysis and periodic overhauls.
Efficiency and Air Treatment Savings
Energy consumption is one of the largest lifecycle costs of any compressor system. Selecting the right type can have a measurable impact:
- Reciprocating compressors: can be efficient at low duty cycles and when sized for high-pressure, intermittent tasks, but they incur efficiency penalties at continuous loads due to cycling losses, higher heat generation and less favourable part-load performance compared with rotary screw or centrifugal designs.
- Rotary screw compressors: maintain consistent efficiency under continuous operation, with variable-speed options helping to reduce idle losses.
- Scroll compressors: deliver excellent energy efficiency for medium-duty applications due to minimal mechanical losses.
- Centrifugal compressors: offer high efficiency at scale, making them ideal for large, constant-load facilities.
Choosing an oil-free system also delivers hidden saving by eliminating downstream filtration and condensate treatment requirements. Without oil contamination, dryers, filters and separators last longer and maintenance intervals can be extended without compromising air quality.
Simplifying Operations with Rental Solutions
Installing and maintaining permanent compressor infrastructure can be complex and capital intensive. Aggreko’s rental air compressor solutions simplify this process, offering plug-and-play systems designed for rapid deployment, minimal site preparation and full compliance with air purity standards.
Our expert team handles installation, commissioning and ongoing servicing, reducing downtime and allowing operators to focus on core operations. Whether you require a temporary, portable diesel unit for fieldwork or a stationary electric oil-free system for continuous industrial use, Aggreko provides a turnkey, low-maintenance solution that delivers clean, efficient air from day one.
Contact Aggreko today to discuss your air purity requirements and find out more about our oil-free air compressors.