The Buying Guide to Choose the Right Air Compressor
An air compressor is a piece of equipment driven by an electric, diesel or gas motor that takes ambient air and delivers it into a closed system (system piping and/or tank) resulting in increase of air pressure until the pressure reaches the users desired limit. The stored energy contained in the compressed air is held until called into use for a variety of applications.
With so many options, sizes and designs, it can be difficult to decide what air compressor is right for you. There are general questions to ask yourself and few guidelines to follow when choosing the right compressor.
Continue reading to find some helpful information that can take you through the process of owning the right air compressor that perfectly fits your requirement.
1. Air compressor grades
The air compressor grade determines the capacity and application.
Consumer grade: Consumer grade compressors are for small garage workshop and can handle small demands; handling a single tool at time. These are typically a reciprocating type compressor, either single or two stage.
Contractor grade: Contractor grade compressors are portable compressors that are used in enabling small tools on work sites such as nail guns or impact wrenches. These are typically a two stage reciprocating type compressor.
Commercial grade: Commercial grade compressors are larger and provide a steady supply of compressed air to power multiple tools or pieces of equipment. Most commonly, they are a lubricated rotary screw type that are typically driven by a diesel engine and are widely used in the construction field.
Industrial grade: Industrial grade compressors are electric motor driven and are stationed in a compressor room or power house of a facility. They are designed to produce all the compressed air required by a facility including pneumatic driven equipment, pneumatic cylinders, valves, blowoff and conveying. Small to medium applications are rotary screw type compressors, oil free or lubricated. Large applications can be either rotary screw or centrifugal type compressors.
2. Air pressure and delivery of the air compressor
An air compressors specification depends upon pressure (PSI), and flow (CFM). This determines the size of the compressor in horsepower (HP) or kilowatt (kW).
PSI- Pounds per Square inch, is the amount of force that an air compressor delivers.
CFM- Cubic Feet per Minute, is the measurement of the amount of atmospheric air that an air compressor can compress and deliver at a rated pressure level.
3. Power source of the compressor
Gas Engine Driven Compressor: Gas engine driven compressors are typically smaller horsepower ranges (Consumer or Contractor grade). They have higher running and maintenance costs than electrical or diesel.
Diesel Air Compressor: Diesel air compressors are used in areas where power is not available, or in extreme regions (Commercial grade). Their robust nature and lower fuel cost compensates for the higher initial cost.
Electric Air Compressors – To ensure air compressors run efficiently after installation, power available should match the power requirements of the machine. Consumer or Contractor electric compressors can operate on 115 or 230-volt single phase power – typically no larger than 10 HP. Larger electric compressors for Industrial applications run on 200, 230 or 460-volt three phase power.
4. Type of Compressor- Rotary Screw Compressor or Piston Air Compressor
If the size of the compressor has been determined, the answer to the below questions will help in selecting the right type compressor. The two most popular options of the type of compressor available are piston compressor and rotary screw compressor.
- What is the application
- Quality of compressed air
- Operation duty of the compressor
- The number of shifts per day
- Fluctuation in flow demand between shifts
- Future expansion plans
Piston Air Compressor
The most cost effective air compressor is the Piston Air compressor. They are relatively easy to maintain and require minimum investment. However, they have a 50% duty cycle therefore they can only be used intermittently. This type of compressor is much louder than other options. They often require additional dryers with high inlet temperature capabilities due to the high discharge temperatures. They are used in automotive service industry and small manufacturing facilities.
Rotary Screw Air Compressors
A rotary screw air compressor is designed for a 100% continuous duty cycle. They are fluid cooled and have a range of control options to ensure the most efficient operation based on the application. A standard dryer can be paired with the compressor and can be used in application where dry/clean air is a requirement. They are available in various HP ranges. They are highly recommended for applications that need continuous volume of air
Oil-lubricated or Oil Free Air Compressors-which one should I choose
Apart from the several parameters such as size, CFM rating and pressure that helps in deciding the compressor, you also have to choose between an oil-free and oil-lubricated system.
The kind of application where the compressor is intended to operate determines the choice. Each type offers advantages for certain applications. It is important to know the differences between the two types and consider certain parameters when choosing the type that is right for your specific needs.
Oil-lubricated Air Compressors
The compression chambers are injected with oil. This helps in dissipating the heat and keeping the system cool. The fluid acts like a lubricant to reduce the friction between the parts that move and also acts as a seal to ensure efficiency in production of compressed air. Lubricated compressors are also much quieter than oil free.
With good maintenance, oil lubricated compressors have a longer life. Keeping in mind that regular change of oil extends the life of the compressor. Maintenance costs need to be factored into the total cost of ownership.
Oil lubricated compressors are robust, efficient in providing compressed air to continuous applications.
Oil free compressors do not have lubricant / oil in the compression chamber. Oil free units are used where compressed air quality must be exceptional with no trace of oil. Oil free compressors have a significantly higher up front cost. Without lubricant to remove the heat of compression, the compressors typically run at much higher temperatures. Without lubricant to seal the rotors or cylinders the efficiency will be reduced, meaning you need more power to produce the same capacity than a lubricated unit. Typically, oil free are used in the following applications:
- Food and beverage manufacturing or packaging
- Medical equipment
- Electronics and semi-conductor manufacturing
5. A reliable compressed air partner
There are many brands available, however choosing a manufacturer with a good warranty and service network to support their product can help you take care of your investment and protect you from failures in the future.
A reliable partner will be able to deliver quality products, assist with your design selection of the right compressor, either though an audit, or engineered estimations based on your end use equipment. They should have qualified technicians, parts inventory and preventive maintenance programs designed to suit your specific needs. A good service provider will ensure you get the longest compressor service life.
If you have any further questions, we welcome you to contact Pattons for a non-obligatory discussion.