- Cubic Feet Per Minute (CFM) - Cubic feet per minute is the amount of air (volume) being delivered by the compressor to the tool. It is used as a measure of the compressor's capabilities. Compressors with high CFM ratings provide more air, making higher CFM units more practical for longer usage.
- Pressure (PSI) - Pounds per square inch (PSI) is the measure of air pressure or force delivered by the compressor to the air tool. Most paint equipment will operate 40-50 PSI while other tools usually require 90-100 PSI.
- Single Stage Compressor - A single stage compressor has one or more cylinder. If there is more than one, both cylinders are the same size. It is not recommended for operating pressures exceeding 100 PSI except if the tool will be used intermittently.
- Two-Stage Compressor - A two-stage compressor always has a minimum of two cylinders. One cylinder will be smaller than the other, making it easy to identify the difference between the two types of compressors. Two-stage compressors are recommended where operating pressure exceeds 100 PSI or when tool usage is continuous. Normal operating pressure of a two-stage compressor is 175 PSI.
- ASME vs. Non Code Tanks - ASME stands for American Society of Mechanical Engineers. An ASME certified tank has been welded to certain established standards. Powermate tanks larger than 11.25 gallons are generally ASME certified.
- Single Phase/Three Phase Electric Motors - A single phase electric motor is 115 volt or 230 volt with 10 being the largest horsepower. It is available in standard duty capacitor start and heavy duty magnetic starter types. Standard duty motors are usually found on smaller portable units and on commercial single stage compressors up through 60 gallon models. Heavy duty models (230 volt) are on all two-stage compressors.
Three phase motors are 230/460 volt and are available up through 25 horsepower. It can be found only in heavy duty units. Three phase electric motors are much more efficient to operate but the cost of having it installed can be very costly.
Both types of motors require magnetic starters for warranty purposes. A magnetic starter acts as a voltage booster on the start up and protects the motor during voltage fluctuations.
- Compressor Location - Select a compressor location near the point where the compressed air will be used, but where the compressor may obtain an ample supply of cool, clean, dry and well circulated air. If necessary, put the intake outdoors and pipe it through the wall to the compressor in order to obtain sufficient cool air. For longer runs, a larger pipe size is required. Outdoor intakes should be covered by a hood or other device to prevent such things as snow and rain from being carried into the compressor.
A stationary compressor should be lagged or bolted securely to a firm, solid foundation (preferably concrete), making sure the compressor is level and equally supported on all of its feet.
- The pulley side should be placed to the wall, but not any nearer to the wall than twelve inches.-This will assure an adequate circulation of air for cooling.
- Tool Ratings- Air requirements for air tools vary. The size of the compressor and output in CFM's will determine the air tools that can be operated. The Air Guide will provide you with the approximate information. You must remember that air tools are rated on an intermittent, 25 percent usage and duty cycle.
For example: A Dual Action Sander has a rated CFM requirement of 4.0 CFM. If this tool is used continuously for one minute, it will actually use 16 CFM. For this type of application at continuous use, a two-stage compressor would be required.
- Basic Components of Air Compressors
- Air Regulator - Used to control the amount of pressure received from the tank.
- Check Valve - Ensures the air flows in one direction.
- Line Pressure Gauge - Reads amount of pressure in the air hose, which supplies the tool with air.
- Motor - Runs the pump.
- Piston - Compresses the air by pulling air into the cylinder of the pump when it moves downward and the pushes the air out when it moves upward.
- Pressure Switch - Stops the motor when the tank is full (cut out pressure) and starts the motor when the pressure falls to a specific setting (cut in pressure).
- Pump - Part that compresses the air and pushes it into the tank.
- Tank - Holds the compressed air until used by an air tool or for some other purpose.
- Tank Pressure Gauge - Indicates amount of pressure in tank.