Air Compressors

An air compressor is a mechanical device that converts energy, usually from an electric motor, petrol engine, or diesel engine, into pressurised air by compressing ambient air and storing it in a tank. This compressed air is then released in controlled bursts to power tools, machinery, and various industrial processes.

It acts as an energy converter: it takes in air at atmospheric pressure, reduces its volume, and increases its pressure to create potential energy that can be used for work.

Air compressors work by drawing in atmospheric air, compressing it to increase pressure, and then storing or releasing it for use.

• Air Intake: The compressor pulls in air through a filter to remove dust and debris.
• Compression:
• In piston compressors, a piston moves up and down to compress the air in a cylinder.
• In rotary screw compressors, two rotating screws trap and compress the air.
• Other types, like scroll or centrifugal compressors, use different mechanical methods but achieve the same result: high-pressure air.
• Storage & Discharge: The compressed air is either stored in a tank (receiver) or sent directly to tools. A pressure switch controls when the motor turns on or off.

Optional features include moisture traps, cooling systems, and pressure regulators to ensure clean, safe, and controlled air delivery.

1. Reciprocating (Piston) Compressors

• How they work: Use a piston driven by a crankshaft to compress air in a cylinder.
• Best for: Workshops, garages, and small industrial applications.

• Variants:

  • Single-stage: Compresses air once—suitable for lower pressure (up to 125 psi).

  • Two-stage: Compresses air twice—used for higher pressure (up to 175 psi).

2. Rotary Screw Compressors

• How they work: Two rotating helical screws trap and compress air continuously.
• Best for: Continuous use in factories, manufacturing, and large-scale applications.
• Advantages: Quieter, more efficient, and lower maintenance for long-term use.

3. Scroll Compressors

• How they work: Two spiral-shaped scrolls (one fixed, one orbiting) trap and compress air gradually.
• Best for: Clean air environments such as HVAC, medical, and food industries.
• Advantages: Very quiet, low vibration, and oil-free options.

4. Centrifugal (Dynamic) Compressors

• How they work: High-speed rotating impellers increase air velocity, which is converted to pressure using diffusers.
• Best for: Heavy-duty industrial use (e.g. power plants, refineries).
• Advantages: Oil-free, high flow rates, suitable for continuous operation.

5. Axial Compressors (less common for general use)

• How they work: Air flows axially through multiple rotating and stationary blades to gradually build pressure.
• Best for: Jet engines, large gas turbines—very high flow, low pressure.
• Not used for typical commercial or industrial air tools.

Direct Drive vs Belt Drive

• Direct-drive compressors have fewer moving parts and are compact, making them ideal for light-duty tasks.
• Belt Drive Compressors offer greater flexibility and are preferred for higher capacity, heavy-duty use due to better cooling and efficiency at different speeds.

Lubricated vs Oil-Free Compressors

• Lubricated (Oil-Based) compressors offer durability and are suited for industrial environments where oil contamination isn't an issue. For oil-lubricated air compressors, it's important to regularly maintain them with routine oil checks and oil changes to ensure longevity.
• Oil-free compressors provide cleaner air, ideal for medical, food processing, and sensitive electronic applications.

CFM (Cubic Feet per Minute) and L/min (Litres per Minute) both measure the airflow output of a compressor – essentially, how much air it can deliver.

To Convert Between the Two:
1 CFM = 28.3 L/min
1 L/min = 0.0353 CFM
So, to convert:

CFM × 28.3 = L/min
L/min ÷ 28.3 = CFM

The CFM or L/min rating tells you:

• What tools can the compressor power
• Whether it can keep up with the continuous demand
• How quickly will the tank refill

To determine the required CFM and L/min for your compressor, you can use a calculator to work out the necessary values.

• Read the Manual: Understand your model’s controls, pressure limits, and safety instructions.
• Check Setup: Ensure correct power supply, check oil level (if oil-lubricated), close the tank’s drain valve
• Connect Equipment: Attach the air hose to the outlet, and connect your pneumatic tool
• Set Pressure: Adjust the regulator to match your tool’s PSI/bar requirement, Use the regulator gauge (not the tank gauge)
• Power On & Pressurise: Switch on the compressor, wait for the tank to reach the cut-out pressure
• Use Your Tool: The compressor will automatically cycle as needed
• After Use: Turn off and unplug the unit, release air pressure, and open the tank’s drain valve to remove moisture
• Store Safely: Coil the hose and store the compressor in a dry, dust-free area

Reciprocating (Piston) Compressors:

• Construction sites (e.g. nail guns, jackhammers, compactors)
• Automotive workshops (e.g. impact wrenches, spray painting)
• DIY and home use (e.g. inflating tyres, running air tools)
• Agriculture and farming (e.g. crop spraying, milking machines)
• Sandblasting (when using high-capacity, two-stage models)
• Vehicle-mounted systems for lorry and bus air brakes

Rotary Screw Compressors:

• Manufacturing and industrial operations (e.g. production lines, CNC machinery)

• Automotive workshops (continuous tool operation and spray booths)

• Food and beverage processing (with oil-free models)

• Pharmaceutical and packaging environments (clean, steady airflow)

• Agriculture and farming (large-scale pneumatic equipment)

• Spray painting and finishing (consistent airflow)

• Sandblasting (sustained high-CFM output)

 Scroll Compressors:

• HVAC and refrigeration systems (quiet and compact)

• Medical and dental facilities (ultra-clean, oil-free air)

• Food and beverage industry (hygiene-critical applications)

• Pharmaceuticals and laboratories (sterile environments)

• Packaging lines (quiet, continuous duty)

 Centrifugal Compressors: 

• Large-scale industrial processes (e.g. power plants, refineries)
• High-volume air demand applications with continuous operation
• Air separation, large pneumatic systems, and process manufacturing

 Oil-Free Compressors (Scroll or Rotary Screw):

• Food, drink, and pharmaceutical industries (no contamination risk)
• Medical and dental applications (clean, dry, sterile air)
• Laboratories and electronics manufacturing (sensitive environments)

Belt-Drive Compressors

• Automotive workshops (robust performance, quieter than direct drive)
• Agriculture (durable for rough conditions)
• Spray painting (smoother, adjustable operation)