How to choose the right air compressor for your factory or workshop? (Guide to calculating CFM and bar pressure)
An air compressor is the lifeblood of any carpentry workshop, blacksmith shop, auto repair shop, or industrial production line. Choosing a compressor with a lower capacity than required leads to reduced air pressure and inefficient tool operation, while choosing one with a higher capacity results in wasted energy and high operating and maintenance costs.
In this simplified engineering guide from Ronak (RONAK.SA) , we will take you step by step to learn how to determine the ideal size and type of air compressor for the nature of your business.
1. What is the difference between airflow (CFM) and air pressure (PSI/Bar)?
Before starting the calculations, the two basic parameters upon which any compressed air system operates must be clarified:
- Flow rate (CFM - Cubic Feet per Minute): This refers to the actual volume of air the compressor produces and pumps per minute. This is the most important factor determining how many devices can be operated simultaneously.
- Air pressure (PSI/Bar): Measured in bars (Bar) or pounds per square inch (PSI), it represents the force of air pushing against pipes and tanks (1 bar is approximately 14.5 PSI). Most pneumatic tools used in workshops operate at pressures between 6 and 8 bar (approximately 90 PSI).
2. Formula for calculating the airflow (CFM) required for your workshop
To determine the correct compressor size, don't rely on guesswork, but follow these practical steps:
First step: Inventory the number of pneumatic tools you use
Each pneumatic tool has a specific CFM consumption listed on its technical data plate. Here are the average consumption of some common tools:
| pneumatic tool | Average air consumption (CFM at 90 PSI) | Recommended operating pressure |
| Tire removal gun (Impact Wrench 1/2") | 4-5 CFM | 6 – 6.5 bar |
| Professional paint gun (HVLP Spray Gun) | 8-12 CFM | 2-3 bar |
| Air Grinder | 6-10 CFM | 6 – 6.5 bar |
| Air Drill | 4-6 CFM | 6.5 bar |
| Dust blower and cleaning gun | 2-3 CFM | 4-6 bar |
Step Two: Identifying Concurrent Tools (Duty Cycle & Concurrency)
Add up the CFM consumption of the devices expected to be running at the same time .
Example: If you have a mechanic in your car repair shop who uses a paint gun (10 CFM) and another who works with a wheel removal gun (5 CFM) at the same time:
Total concurrent consumption = 15 CFM .
Step three: Applying the Safety Factor
To prevent the engine from constantly running at full power and burning out, a safety margin of 30% to 40% should always be added, also to accommodate any future expansion of the workshop:
$$\text{Required CFM} = \text{Sum CFM of synchronized instruments} \times 1.35$$
In our previous example:
$15 \times 1.35 = 20.25\text{CFM}$
Therefore, you need a compressor that generates an airflow of at least 20 to 22 CFM .
3. Belt/Piston compressor or Rotary Screw compressor?
| Comparison | Reciprocating/Piston Compressor (Piston/Belt-Driven) | Rotary Screw Compressor |
| Nature of work | Suitable for intermittent work (50% - 60% work cycle) | Designed for continuous, demanding work (100% work cycle) |
| sound level | Relatively high and emits vibrations | Very quiet and suitable for working inside production halls |
| The most suitable place | Maintenance workshops, carpentry, blacksmithing, and tire centers | Large factories, packaging lines, and CNC workshops |
| Cost | Economic and medium | Highly efficient industrial investment |
4. How do you choose the size of the air tank (Air Tank Capacity)?
The tank capacity (in liters) represents the reserve air supply that prevents the engine from rapidly repeating start-stop cycles:
- 50 to 100 liter tanks: suitable for light work, mobility, clamping guns and intermittent blowing.
Several options are available at the Rawnak store in various sizes such as 50 liters , 100 liters , and more.
- 150 to 300 liter tanks: Ideal for woodworking shops and medium-sized car repair centers for operating dismantling and grinding guns.
Several options are available at Rawnak store in various sizes such as 150 liters , 120 liters , 150 liters , 300 liters , and more.
- Tanks of 500 liters and above: essential for professional spray guns and painting, large workshops and production lines that consume a continuous flow of air.
Several options are available at the Rawnak store in various sizes such as 500 liters , 1000 liters , and more.
5. Important tips to ensure the efficiency of your factory's air network
- Use an air dryer and a moisture filter: humidity damages pneumatic tools and leads to damage to painting and dyeing work.
- Choose the appropriate pipe diameter: Avoid hoses that are too long and too narrow, as these cause a noticeable loss of bar pressure before air reaches the tool.
- Daily tank drainage: Make sure to empty the water drain valve at the bottom of the tank daily to protect the internal compressor body from rust and corrosion.
Equip your workshop with the best air compressors from Ronaq
Whether you are setting up a new maintenance workshop or upgrading production lines in your factory, at Ronak (RONAK.SA) you will find a wide range of industrial air compressors, workshop equipment, connection accessories and filters certified to the highest standards of quality and performance.