Portable air compressors are versatile pieces of equipment, but these rugged machines are not one-size-fits-all. Contractors need to make sure they are getting the appropriate compressor for the job. The primary consideration when choosing a compressor is to determine what the compressed air is going to drive. Once you know the application, it's only a matter of matching the intended use to a specific compressor size. First, let's discuss the fundamentals of an air compressor: pressure and volume.

Pressure and volume

Pressure and volume are the two most important variables when selecting a compressor. Pressure is measured in pounds per square inch (psi) and volume is measured in cubic feet per minute (cfm).

Pressure

When selecting the compressor, the first variable to investigate is the pressure rating. The pressure rating can be derived from the particular model name on the compressor unit. For example, Doosan Infracore Portable Power assigns a lettering system to each Ingersoll Rand model in order to understand each unit's operating pressure output. The letter "P" equals 100 psi, the letters "HP" equal 150 psi, the letters "VHP" equal 250 psi and the letters "XHP" equal 350 psi.

Volume

The volume rating of a compressor also can be identified by the model number. Most manufacturers use the same numbering system for the volume rating-- cubic feet per minute -- so it is easy to identify the volume of air being delivered by the compressor. For instance, a compressor with a 185 in the model name denotes a unit that outputs 185 cfm of air.

Engine

After pressure and volume, the most important component of an air compressor is its engine. Most air compressors are rated as either continuous or intermittent duty. For continuous use, the ideal engine margin is 85 percent of its maximum rated horsepower. For intermittent use, 93 percent is the margin.

Of all components on an air compressor, the engine will have the highest amount of wear. Be sure to follow the engine manufacturer's recommended maintenance schedule.

Applications

The majority of uses for compressed air in construction applications are for cleaning, blasting, renovation, installation or demolition. Typically, portable air compressors range in volume from 90 to 1,600 cfm and pressure from 100 to 350 psi. For the majority of these applications, a contractor needs a compressor in the 90 to 250 cfm range. Some compressor distributors carry smaller, portable electric compressor models. Larger open-frame air compressors capable of 500 psi are used in heavy drilling operations, such as oil drilling, offshore, quarry and water well drilling.

Blasting

Blasting applications use compressed air to remove scale, paint and rust from surfaces in order to prepare metal surfaces for painting, enameling and tinting. Other materials can be used with compressors, such as sand and steel grit, to blast paint and residue off bridges and water towers.

Painting

For painting, compressors are used to supply power to painting tools and speed painting productivity on a variety of surfaces, such as bridges. Truck-mounted compressor models are often used for highway line painting.

Utility

Compressed air can be used to operate air tools in utility applications, such as repairing electric, water and sewer lines. Contractors also can use compressors for line testing to ensure there are no leaks and to determine whether or not a line is able to hold certain levels of pressure. Compressors are often used for powering directional drilling equipment that install fiber optic cable.

Demolition

Portable compressors are an ideal power source for pneumatic and hydraulic tools used to break concrete pavement, foundations and walls, as well as to cut pavement and sub-base.

Tool guidelines

Tools designed to be used with air compressors will have a pressure and volume rating listed on them. By knowing those two numbers, selecting the compressor model that provides enough pressure and volume to run the tool is easy.

Most general construction applications, which include operating light pneumatic tools, require a compressor with at least 100 psi. Applications such as blasting or painting can require compressors with operating pressure in the 150 psi range.

The more tools expected to run off one compressor, the higher volume of compressor will be needed. Any compressor dealer will be able to provide the necessary cfm for each tool and can help determine which size of compressor is needed to fulfill the requirements of the job.

Maintenance: an ounce of prevention

Air compressors are rugged machines and can handle rigorous environments, but they do require care and maintenance. A strictly followed maintenance routine will pay for itself in the long term with increased efficiency and jobsite safety. Here is a general guideline for maintenance best practices.

Daily checks

Daily maintenance is probably the most critical yet, many times, is ignored by contractors. Work productivity is important, but taking 10 minutes each day to check the air compressor is vital to ensure the machine doesn't go down during the day.

First, start with a general walk-around of the compressor, checking for leaks. Then check the oil and radiator coolant levels. Check gauges and lamps to make sure they are in working order, and drain any water from the fuel filters. Check the air cleaner service indicators and fuel/water separator drain. Clear out the pre-cleaner dumps, and make sure the radiator cap is secure. Finally, don't forget to check that the fuel system is free of debris with enough fuel for the day's run.

Extra checks

A few extra checks must be added to the daily routine. Fan and alternator belts should be inspected for wear. Check the battery for corrosion and for secure connections. If the air compressor is a mobile unit, check the tires each time it's transported.

Monthly checks

Every month, check the machine closely for wear. Parts may need to be replaced. Check the hoses and tire lug nuts. Make sure the automatic shutdown system is in good working order, and clean the air cleaner system, the exterior of the oil cooler and the engine radiator.

At 500 and 2,000 hours

Major maintenance is determined by hours the unit is in operation. The 500-hour mark is when all filters need to be replaced; however, if the air compressor is operating in a dirty environment, air filters should be checked daily and replaced when necessary. At 2,000 hours, the separator element will need to be replaced. The element may need to be replaced before 2,000 hours if the service air starts to fog or there is oil carryover.

Air compressors are designed to be flexible and dependable. In many instances, more is not necessarily better. When it comes to working efficiently and effectively with compressed air, it is important to consult experts. such as your dealer, to ensure you choose a compressor with the right amount of pressure and volume to match your application. Access online information on portable air compressors at http://www.ConstructionEquipment.com/Equip ment/21251.html .

Information provided by Doosan Infracore Portable Power.

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