A Guide to Buying Compressors

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A Guide to Buying Compressors

There is energy in air stored under pressure, and this energy can be used constructively to drive tools. This is achieved with an air compressor. Air compressors are used along with air tools in a variety of manufacturing, industrial, and commercial applications as well as in households. Simple jobs such as inflating pool toys are done by simple air compressor models. Powerful air tools used for complex automotive and other industrial jobs run on the same principle of obtaining energy from compressed air.

Air tools are also called pneumatic tools and are designed specifically to be used with air compressors,, which come in various types. Air compressors can power an impressive array of tools, from spray guns and nail guns to wrenches and many more. Buying a compressor can be tricky, as the user has to find the type of compressor that accommodates specific needs. Whether the air compressor is to be used in a workshop or home and what type of air tools it needs to be used with are pertinent questions that help the selection of the right machine. Compressors are available at brick-and-mortar stores; however eBay offers a reputable online option with a vast inventory of compressors.

Types of Compressors

The basic parts in a compressor are the tank, the pump, and the motor. The motor activates the pump to draw in air, which is then compressed to a pressure higher than atmospheric pressure. The compressed air is stored in the tank to be used as required. To replace the used up compressed air, the pump is worked automatically to draw in more air. Various compressors are designed differently, but the end result is the same, in compressing the air to occupy a smaller area. The features where the design of a compressor differs is in the cooling method, lubrication, power source, and compression stages. There are, however, three basic designs for compressors.

Piston-Type Compressors

Also called reciprocating compressors, these are the more common type of compressors and are categorised as positive displacement compressors. These work by filling air in a chamber or tank, and then, using pistons, crankshafts, and valves, the volume of the air is reduced so it occupies lesser space in the tank. When this air is depleted, the motor refills the tank with more compressed air. A reciprocating compressor, based on the number of compression stages may be a single-stage compressor with a single piston,, or two pistons for a double-stage compressor.

Single-stage compressor systems are normally found on light-duty compressors where the  maximum rating is below 150 lbs of pressure per square inch, or PSI. These compressors are ideal for home repair jobs.

In two-stage compressors, the first piston compresses the air, pushing it through a check valve to the second piston. Further compression is achieved by the second piston, which also delivers the air to the storage tank. Found on commercial heavy-duty compressors with maximum ratings above 150 PSI, two-stage compressors are typically used by small businesses and shops that have continuous usage.

Rotary Air Compressor

The positive displacement configuration in rotary screw air compressors is the same as in piston-type compressors, except that two spinning rotors or helicals in a mesh are used to compress air.

Centrifugal Compressor

When the demand for compressed air is high, a centrifugal compressor is the solution. Also called a dynamic compressor, the unit has a high-speed rotating impeller to increase air velocity as the air is allowed into the impeller, and the air at high speed is then directed towards a diffuser. The gradually increasing passageway of the diffuser slows down the air, and the resultant kinetic energy, the energy by virtue of its motion, is converted to increase air pressure. Operating a centrifugal compressor requires more energy that other compressor types.

Specifications on a Compressor

Compressor ratings are based on four criteria, elucidated below.

The air pressure rating of a compressor is indicated by PSI, or lbs per square inch. This is the measure of air pressure delivered by the compressor. A higher PSI indicates that there is room for further compression, which means large volumes of compressed air can be stored in the tank.

The pumping power of the compressor, indicated by SCFM or standardised cubic feet per minute, is the measure of the airflow of the compressed air. This is the factor that determines how well the air tools function, and one should choose a compressor with a CFM, or cubic feet per minute, rating that is one-and-a-half times the rating of the most powerful power tool in one's kit. For workers using several tools, sum up the CFM rating and multiply the number by 1.5 to obtain the ideal CFM rating of the compressor.

Horsepower, or HP, is the measure of the power of the compressor's motor. Compressor engines with higher HP deliver greater air pressure or create greater PSI.

Tank size,, measured in gallons is the storage capacity of compressors, generating higher levels of PSI for longer lengths of time and therefore providing greater power to air tools.

Other Factors to Consider When Buying Compressors

Two other important factors to consider while buying a compressor is its portability and the power source for running the engine of the compressor.


Portable compressors are available in many sizes, and these include small ones that can be carried around. Some of these compressors are equipped with wheels. Small jobs like inflating tyres or powering a finish nail gun can be easily done using an oil-free compressor with 2 to 6 gallons of tank capacity. Powerful portable compressors with greater storage capacities such as 20 to 30 gallons are available as space-saving vertical compressors..

Stationary compressors, or industrial compressors, are generally huge, with 60- to 80-gallon tanks and motors with 4 to 10 HP. These are used by garages and workshops so they can operate a wide variety of air tools.

Power sources

Electric compressors are a better choice for indoor applications as they do not emit toxic fumes. Compressor motors that exceed 2 HP require 220/240V outlets, while there are smaller motors that use standard household voltages of 110/120V as well.

Petrol-- and diesel-driven compressors are more suited to heavy-duty industrial applications where availability of electrical power supply is erratic or not available, such as at construction sites. High output and convenience at the job site make these compressors ideal for outdoor jobs. Petrol-powered compressors, if used indoors, should be in well-ventilated work areas.

Accessories to Use with Compressors

A vast array of accessories may be needed for use with compressors, depending on the type of job at hand. These may range from blow nozzles and spray guns to air impact wrenches.

The air hose line is an accessory that every compressor, regardless of size needs. Quality hoses of adequate length and diameter should be chosen so sufficient volume of air is supplied to the air tools.

Quick-connect end fittings are needed when the air tools are to be changed. Couplers comprise two parts and have female ends that fit at the hose, while the male end is fitted on the air tool. Couplers vary with the air tool and type of job to be done. Pressure gauges and regulators on the compressor indicate the air pressure, and the adjustments that can be made while operating the compressor.

Nail guns,, spray guns, sanders, wrenches,, and a whole variety of air tools may be used with compressors for carrying out different jobs.

Buying Compressors on eBay

eBay shoppers have numerous choices, and with Top-rated sellers offering quality products, finding a good product at affordable rates is easy on the website. Quality compressors from leading brands such as Draper,, SIP,, Ingersoll Rand, Clarke, Atlas Copco, and Sealey are available on eBay, offered by the website's Top-rated sellers.

Shoppers desirous of buying compressors on eBay need to begin the search under an appropriate category, such as 'Industrial Tools', which is a subcategory under the 'Business, Office & Industrial' category. The subcategory of 'Compressors' offers listings for compressors from various brand names. The listings page gives important information about the product, including the seller and the price. If you have questions that are not answered by this information, then you can communicate directly with the seller to learn more about the product. eBay offers numerous secure and safe payment options so shoppers can select one that is convenient to use.


Compressors are versatile machines that work pneumatic tools for a wide range of applications in households and small, medium, and large businesses. These air tools have more torque and power than conventional tools that run on electricity and need less maintenance, as they have fewer moving parts. Three types of compressors,, namely, piston-type, rotary, and centrifugal compressors are available in the market. The basic design of a compressor comprises the motor, pump, and the tank. Variations in the capacities of the tank, pumping, and motor power make for compressors of various types that can be used for small home improvement jobs and for large industrial applications as well.

Thanks to its wide network of sellers, an online retailer such as eBay is able to make available a large inventory of air compressors that are suitable for a variety of uses. Once a shopper has identified his or her needs, it is only a matter of utilising the website's user-friendly search tools before locating and purchasing the right air compressor for the job.

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