Technology for easier operations in most occupations: The air compressor

Hand drills, sanders, powered screwdrivers, impact hammers and wrenches, staplers, nail guns – the number of power tools used in a workshop or on a work site is as varied as the tasks required.

While all of these tools can be electrically powered, by cord or battery, there is an alternative: pneumatically driven, powered by an air compressor.

air compressorThere are many advantages to the use of an air compressor, but it is important to understand how they work and how to choose the right model to maximise its effectiveness. Even smaller sized compressors can be perfect for your particular situation. Using a smaller air compressor enables more flexibility in your tools use. You can get into harder to reach places and does not come with the noise that is produced by larger machinery.

The advantages of an air compressor

By working as a central power source for a variety of tools, an air compressor allows a worker to user tools without separate, individual motors. This makes each tool lighter, quieter, more compact and easier to use. Also, without individual electric motors, each tool is less expensive and has fewer parts to wear out, making it more durable and with a longer working life. Gas-powered air compressors also allow for the use of powered tools in areas where electrical sources are unavailable and the use of electric battery tools is not practical.

How compressors work

The most basic explanation of the function of a compressor is that it increases the pressure of air by reducing the amount of space a given amount of air occupies. This space, called the pressure tank, stores the air until required. The power of this pressurized air is then released in sudden bursts to power a tool. In other words, a compressor converts electrical energy into kinetic energy.

There are a number of different methods used to force air into a tank and bring it up to a desired pressure. Some compressors use rotary screws, scrolls or sliding vanes, while others use centrifugal mechanisms. The most common method, however, uses a reciprocating piston. Much like an internal combustion engine, piston compressors draw in air into the chamber through a valve before the cam shaft and connecting rod push the piston forward to compress the air, which is then vented through another valve into a tank. This cycle is repeated until the air in the tank reaches the desired pressure.

Performance

As with any power source, compressors can be rated by the amount of work force they can deliver. They can be rated by three separate measurements: power, tank size and air flow rate. The amount of power delivered by the engine driving the compressor is, in many ways, the least reliable way to judge the effectiveness of a compressor. Whether the motor is 3 HP or 10, its effectiveness depends upon the efficiency of the compression mechanism. Of greater importance is the size of the tank: It should be large enough to store sufficient compressed air to accomplish the job at hand, but without excess capacity (since compressor models increase in price depending upon the size of the tank). If a tool powered by the compressor requires continuous air to drive it, a tank that is too small can quickly deplete its air. This requires a “recovery time,” during which the tank re-pressurizes – and during which no work gets done.

Air flow rate

When selecting a compressor, the most important consideration should be the air flow rate, expressed in cubic feet per minute (CFM). This is a value of the amount of air that can be compressed to a given value over a specific amount of time, and is a product of the cylinder bore, stroke and RPM of the cylinder that the motor can achieve. Ideally, a compressor should be able to deliver 4 CFM @ 100 psi per HP. A reliable method of measurement, across the range of air compressor styles and models, is expressed as the SCFM (standard cubic feet per minute), for air measured at sea level, 35% relative humidity at 68° F temperature. This gives an indication of the relative speed at which a compressor can bring the tank up to the required pressure and, if necessary, cycle through recovery time if the tank is depleted during operation.

Other considerations

Air compressor motors can be powered by electricity or gas motors. The advantage of gas motors is, of course, that they can be operated in field conditions in which electricity is not available. Because of their exhaust, however, they cannot be used indoors and tend to be noisier than electrically driven motors. Electric compressors are safer and tend to be less expensive, but naturally require a source of power.

Lubrication is another consideration. Oil-lubricated compressors keep the cylinder walls, piston and other moving parts from overheating, using piston rings to separate the oiled mechanism from the compressed air. These rings can weaken and fail, however, which can cause the lubricant to mix with the air; this can cause problems when the compressor is being used for a paint sprayer or tools used for woodworking. Oil-free compressors, such as those available from HTE Technologies, use permanently lubricated bearings, which do not require the same type of maintenance as oil-lubricated compressors.

Air compressors provide a reliable, controlled source of power for tools used in a wide variety of applications. Once restricted to factories and commercial workshops, air compressors are now available in styles and sizes that make them affordable for home workshops and for use by hobbyists. By considering the power requirements for a particular workshop or work place, a model of air compressor of air compressor can be found that will meet their specific needs.


Charles Sims is an automotive mechanic. He likes to write about his work experiences on the internet. His posts can be read on a majority of industry blog sites.