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What is Compressed Air?

Compressor Selection

Choosing the right compressor is essential to your long-term satisfaction and profitability of your business. Many times compressors are selected by a single factor alone, such as horsepower or tank size, which is only part of the story. This page will help guide you in choosing the right compressor for your and your business.

Air- It's All Around Us! What are we compressing? Just plain and simple air. It's free and it's readily available. Air is invisible, colorless, odorless, tasteless gas consisting of 78% nitrogen, 21% oxygen and 1% trace gases.

Compressors Speak

Many terms used to evaluate compressors need to be defined and clarified. Here is a list of common terms that will be useful in understanding.

- CFM- Cubic feet per minute. This is a measurement of the volume of compressed air over time required to perform a particular function- normally to power a tool or equipment.

- PSI- Pounds per square inch. Just like the psi rating of a tire, this is the amount of pressure inside of the vessel or system.

- Horsepower (HP or hp). Mechanical units of power or work. The more horsepower, the stronger the motor or engine of a compressor, so the more work it can do. Generally, more horsepower means the compressor is able to generate more compressed air.

Piston Compressor

Why is Compressed Air Useful?

The compressed air energy contained within a balloon is equal to the energy required to inflate it. The energy is stored as pressure.

When the balloon bursts, the pressure equalizes and the energy is released. This energy can be used to complete work.

Why Use Compressed Air?

Advantages over other types of power:

- Cleanliness: Unused air is exhausted to the atmosphere. Air leaks are much cleaner than oil, gas, or battery leaks.

- Availability: Air is readily available and does not have to be generated like electricity or created like oil/gas does.

- Simplicity of Design and control: Compressed air is easy to control with pressure gauges and valves. Controlling oil and electricity can be very difficult.

- Reliability: Tools using compressed air tend to have long operating lives and require very little maintenance compared to tools operating on oil or electricity.

- Storage: Compressed air can be stored in receiver tanks, allowing use of tools when electrical or hydraulic power is lost.

- Safety: Very small fire hazards (compared to hydraulic oil or electrical short circuiting). Air equipment can be designed to be inherently safe.

Types of Chicago Pneumatic Compressors

Homepage QRS

Rotary Screw Compressors: Variable Speed Compressors Quiet Rotary Screw Compressors

Piston Compressors: Contractor Series Professional Series Industrial Series

Reciprocating (Piston) Compressors

How do they work? Just like an engine of a car, as the pistons rise, they press the air into a tighter space which creates pressure. CP compressors can have 1 stage or 2 stages of compression.

Single-Stage Piston air is compressed once and then discharged. Max Pressure = 130 PSI. Two-Stage Piston air is discharged once in a low pressure side and again in a higher pressure side before discharge. Max pressure = 175 PSI.

-Advantages of Piston Compressors:
- Low Price
- Easy to Understand
- Simple to Maintain

Duty Cycle: Piston compressors generate a lot of heat during the compression process, they are restricted to the amount of time they can operate. This is what we can the "duty cycle". Single-stage pistons normally have a 50% duty cycle and two-stage pistons have a 75% duty cycle.

Rotary Screw Compressors

Rotary screw compressors act like superchargers in a sports car. Two helical rotors match each other and rotate together. As they do, air is squeezed into a smaller and smaller cavity, creating increasing pressure. A thin film of oil lubricates the rotors and keeps them from overheating.

Advantages of Rotary Screw Compressors OVER Piston: - Runs cooler so it can operate continuously - More stable pressure - Air always available when you need it - Low sound level- 7 times quieter than a Piston - Better work environment for your team - Lower Oil Carryover - Reduces product contamination - BEST choice for painting - Better for the environment

Duty Cycle: For rotary screw compressors, the cooling systems are much better, so the compressors can run constantly with no issues. They are designed to run 100% of the time (100% duty cycle) so you can get your job done without needing to wait.

Sizing the Compressor

To size the compressor, we need some basic information.

1. Maximum Operating Pressure: - Look at the pressure ratings on the equipment - Are there any known pressure issues?

2. Total Air Requirements (Total cfm) - Add up all the cfm ratings on the equipment (they are listed on all tools) - Do you want to wait on the compressor for air? - How many tools are you using at once? - Have existing compressors and storage tanks?

Calculate the Correct Air Requirements 1. Determine the total air requirements (in cfm) for all equipment 2. Make adjustments: - Add 10% for leaks and growth in business - Use consumption x 1.5 for piston compressor - Use consumption x 1.0 for rotary screw 3. Determine final air requirement in cfm for the equipment 4. Check your air requirements with the "benchmarks" below on the number of workers

Rotary screw used for a compressor instead of a rotary vane


5 cfm per person in mechanic shop 12 cfm per person in paint & body shop

More is sometimes better..

- Consider (2) smaller compressors instead of (1) large compressor. - Provides redundancy for compressed air - Allows maintenance on one compressor while the other operates, reducing downtime. - In case of compressor shutdown, compressed air is still available. - Provides energy savings in time of low air demand (one compressor is shut-down) and enough capacity during periods of high demand

Things to Remember

Réseau d'air AIRNET

Don't forget the piping:

Verify airline sizes are adequate in the building and airline drops are properly sized. Fittings should be adequately sized and not restrict air flow at the tool. NEVER use PVC pipes.

Why to Not Use PVC Piping for Compressed Air

Stop the Leaks!

- According to the Department of Energy, 26% of all compressed air leaks out of the system and back into the atmosphere.

- Conduct a simple air audit. Find out how much air is needs vs. how much the customer is using.

- Listen for leaks and use an ultrasonic leak detector.

Any additional questions?

CP service technician in fron t of CP compressor
Whether you have questions about which compressor is right for you, or if you’re ready to improve your operations and start saving on expenses. Chicago Pneumatic has been around for over 100 years because we offer reliable and hardworking air compressors, as well as expert advice and support.