To select the right air compressor, you must first determine the frequency of use according to the compressed air needs of your application.
You also need to know if the compressor needs to be portable or if it is to be installed in a single location. In this instance, you want to make sure that the compressor is fully vented for optimal cooling.
Another important element is the compressor’s continuous operating time. Manufacturers usually specify a load factor for their products. This factor determines how long the compressor can run per hour.
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KAESER Air Compressor
A compressor with a duty cycle of 30% can only run for 18 minutes and must cool down for 42 minutes. If you select such a compressor, you need to make sure that 18 minutes of run time is sufficient to fill the air receiver to the suitable pressure for your use for one hour.
Air compressors allow you to use a variety of portable air tools: Hammers nail guns, air screwdrivers, demolition hammers, blowguns, paint guns, sandblasters, etc.
Stationary or mobile air compressors can also play an important role in industry or agriculture:
- Use of air tools on production lines.
- Pushing out parts from production tools.
- Blowing out to form bottles or cups.
- Feeding pneumatic cylinders.
- Sandblasting for finishing metal parts.
- Spraying of crops.
- Feeding of dairy machines.
- Ventilating greenhouses, etc.
What size air compressor should you use?
BOGE Air Compressor
Before sizing a compressor, you need to know the maximum pressure require to supply your air tools or circuits. This can be express in pounds per square inch (psi), in a bar, or Pascal’s (Pa).
Depending on the pressure, you may need a single-stage compressor (maximum 135 psi or 9 bar) or a multi-stage compressor that increases the pressure significantly (maximum 5800 psi or 400 bar).
You also need to know the maximum airflow rate. The flow rate is the amount of air available to operate the various devices that need to be connected to the compressor.
It can be express in cubic feet per minute (cfm), liters per second (l/s), or cubic meters per hour (m3/h). It is better to allow for a safety margin of about 30% of the calculated demand to avoid unpleasant surprises and to avoid oversizing the compressor.
The capacity of the compressor
The capacity of the compressor depends on the required air volume and the output pressure. If a compressor is an offer with high capacity but low airflow, it is designed for occasional use and its cooling requires long breaks.
Compressors usually have a compressed air reservoir that allows you to adjust the start-up of the motor to the amount of compressed air require. You need to properly calibrate this reservoir so that the engine does not run constantly. Some compressors are equipped with a vertical tank, which reduces the space required for installation in confined spaces.
What type of compressor should you choose?
INGERSOLL RAND Air Compressor
There are two types of compressors:
Positive displacement and centrifugal (called dynamic)
Many compressors are positive displacement compressors, which indicates that the mechanism reduces the volume of air to compress it. These compressors normally operate by electric motors. There are different technologies available:
Piston compressors:
They can be single-cylinder. This type of compressor can produce pressures up to 10 bar. They can also be multistage for a step-up pressure and reach up to 400 bar. Piston compressors are usually the cheapest.
You can choose this type of compressor if you need intermittent operation:
The duty cycle is no more than 60%, i.e. it can only run for 35 minutes per hour. The compressed air supply should be sufficient relative to the design flow so that the compressor does not have to run more often.
Another possible disadvantage of this type of compressor is that it ejects oil along with compressed air. If you want clean air, you should use a filter system or take an oil-free compressor (e.g., for the electronics, pharmaceutical, and food industries, or cleanrooms).
Recirculating compressors are also relatively noisy, which can be uncomfortable for people working nearby.
Screw compressors
This is the most common industrial model. It uses screws instead of a piston. The pressure achieve can range from 5 bar in a single-cylinder model to 13 bar in a multistage model.
This type of compressor typically offers a high flow and high compression ratio at a single stage, allowing manufacturers to offer compressors with smaller dimensions than similar piston compressors (which must be multi-stage to achieve the same pressure level).
Efficiency
The duty cycle of a screw compressor can be 100%, which means it can run continuously. Some screw compressors have variable speeds. They can adjust their speed depending on compressed air demand to optimize energy consumption.
Rotary plate compressors
Vanes are plates that slide in an eccentric rotor to compress air. The energy efficiency of these compressors is usually quite high. These compressors are quite compact compare to compressors using other technologies.
At comparable pressure and capacity, these compressors have lower speeds than screw compressors, which reduces wear and tear on parts and reduces maintenance. This allows the compressor to last longer.
These compressors are used in various industries such as printing, woodworking, or packaging. For industries that require clean air, such as the energy industry or medicine, many models are available without oil.
Centrifugal compressor (Dynamic compressor)
The second type of compressor is a centrifugal compressor (also called a dynamic compressor). In these compressors, the air sucks through the machine by the rotation of a radial impeller. This is the same principle as turbochargers in the automotive industry.
They typically use where high capacities at high pressures require continuously. This is especially the case in the energy and chemical industries.
These compressors are usually equipped with a built-in reduction gearbox that allows the engine to run at optimum speed. These compressors can deliver flow rates up to 500,000 m3/h at 200 bar.
There are three basic configurations of compressors:
1. Stationary compressors
These machines do not design to move. They are usually very powerful and provide high flow and high pressure.
2. Portable compressors or semi-stationary compressors
In common, they have similar features to stationary monoblock compressors, but move to other locations (e.g. construction sites).
Their base usually design to pass forklift forks. These compressors are equipped with an internal combustion engine.
3. Mobile compressors
They not usually design for heavy use but have the advantage that they are very easy to move.
