Buying the right air compressor

Buying the right air compressor for the job

Air compressors are pneumatic devices that convert power using electric motor, diesel or gasoline engine, etc. into potential energy stored in pressurized air i.e., compressed air. They have many uses, from powering small tools up to large industrial applications.

Air compressors provide clean, consistent, energy for many different applications, and they don’t lead to frequent overloading, unlike electrical power. Industrial grade compressors such as rotary screw compressors, are particularly efficient at saving long-term costs, and can even channel by-products such as heat into further business savings. This explains why air compression is such an essential component in many businesses.

However, with all the various options available in the market today, buying the right air compressor can be a guessing game without the right set of guidelines. There are nearly as many different air compressor and option combinations as there are types of applications and making a mistake when buying the right air compressor can cost you efficiency, extra service, and event production.

What you need to consider

The intended use of the compressed air

The most common use of compressed air is simply to power pneumatic tools. In the shop setting, for example, the air compressor powers tools like impact wrenches, nail guns, drills, grinders, and blowguns amongst hundreds of other stationery and portable tools.

Each device has manufacturer specifications for the appropriate amount of pressure in either psig, bar, or kPa units and airflow in either cfm, l/sec or m3/min units. The performance of the equipment is largely dependent on these factors, and they must be kept in mind when selecting an air compressor.

When buying the right air compressor, if the compressed air is to be used as a source of power for certain precision apparatus, the selection becomes even more critical. For Example, a pneumatic drill can operate with a certain maximum level of contamination that would not be acceptable for a precision dentist’s drill. Although both drills must have the incoming air filtered to remove dust and water before entering the tool, a dentist’s drill should not receive any contamination at all, including the oil that is commonly used in operating an air compressor.

Special types of compressors are available that use no lubricating fluid in the compression chamber – either oil-free or oil-less.

The duty cycle of the equipment.

Certain types of compressors are chosen for continuous duty based on their robust design and ability to run at a constant temperature, regardless of demand.

Air-cooled compressors (usually a piston-type) are generally ideal for intermittent duty usage that requires them to operate at most 60 to 70% of the time. If the compressor is not allowed to discharge, or rest, at least 30% of its operating cycle, heat could damage the head and valves.

Some replacement compressors include forced lubrication, heavyduty valves, and efficient intercooling, which allow the equipment to operate at very high-performance cycles and continue to provide years of operation. Rotary screws and centrifugal compressors are designed for continuous operation. Because they have internal cooling, this type of compressor can operate 24 hours a day, 365 days a year as needed. However, this type of design comes at a premium.

The cost of the air compressor

The “initial purchase price” of any durable item is the deciding factor when choosing one model over another. The initial purchase price is affected by a number of factors, such as design, pressure, and flow, lubricated or oil-free, and any special features that may be required. In general, rotary screws and centrifugal compressors tend to be more expensive than reciprocating compressors because they are designed for heavier work and longer maintenance intervals.

The second part of the cost estimate is the overall cost of ownership. Generally, the initial purchase price for an air compressor represents approximately 10% of the cost of owning a compressor over the first five years. Other components include installation, maintenance, and power consumption. The biggest contributor to ownership costs is power, ranging from the same costs per year as the initial investment to three or four times the initial cost per year. In choosing the lowest price beforehand, the customer can pay almost double the amount compared to the initial cost of a slightly more efficient compressor. To assist in this part of the decision, all air compressor manufacturers provide data sheets that clearly show the strength and power of their equipment. These data sheets can be obtained from each manufacturer or their respective local distributor.

Amount of customization required

This can include special cooling equipment for hot or cold environments, sound reduction devices such as enclosures or active noise cancellation, control devices to integrate into existing equipment, non-standard voltage among many other adjustments. If a standard piece of equipment nearly meets the requirements, it is a great advantage to make a compromise in the name of economy and long-term service.

The selection process should take into account these factors. The above information is not intended to make the final choice, it serves to give you an idea of the questions you should ask when faced with the problem of equipment selection.

The main objective of the article is to make sure that the impact of a proper selection, based on real requirements like airflow, pressure, and ultimate lifecycle cost, is considered rather than simple power rating and initial purchase price.

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