Air Compressor

Purchasing

Guide

Air tools and compressors have become commonplace on jobsites across the country. This guide is meant to help you select the right compressor for your operating needs.

This guide will review the following:

TrendsTypesSpecsChoosing a Seller

For a more in-depth review of the these topics, please see our full length Purchasing Guide: http://www.purchasing.com/construction-equipment/air-compressors/purchasing-guide/

Air Compressor Purchasing Guide

Trends

Recent air compressor developments have revolved around ease-of-maintenance and increasing efficiency:

Air Compressor Purchasing Guide

Lower Maintenance

Fewer Emissions

Greater Efficiencies

• Oil free compressors lubricate components with Teflon or similar resins, removing most of the maintenance associated with air compressors

• Tier 4 category air compressors adhere to strict EPA guidelines lowering emissions while increasing fuel efficiencies – resulting in a lower total cost of ownership

• Lower maintenance, higher fuel efficiencies, and new variable speed drives have greatly increased air compressors capacity while saving substantial energy

Depending on your application needs, there are three main design types of air compressor you should be familiar with:

1) Reciprocating compressors – usually falling on the smaller end of the output scale, reciprocating compressors feature two different cylinders – ‘lubricated’, which use oil to maintain cylinder integrity, and ‘non-lubricated’, which use Teflon and are often lighter in weight

2) Rotary screw compressors – compress air by drawing it through two or more interlocking screws. Rotary screw compressors feature higher capacities (7.5-100hp), but can often suffer from excessive heat build-up

3) Centrifugal compressors – the largest of the three and powered by electric motors or steam turbines. Often used in large industrial manufacturing processes, output can range up to 500hp and 15k CFM at 125 psig

Types

Air Compressor Purchasing Guide

Alternatively, you can also categorize air compressors by:

Portable – sufficient to power common air tools, portable air compressors are lightweight and can feature wheels to ease transport. Portable compressors usually fall within the reciprocating compressor family

Stationary – designed for longer-term projects, stationary units provide much higher CFMs than their portable cousins. Higher end rotary screw compressors are usually stationary models

Types

Air Compressor Purchasing Guide

Truck mounted and towable – helpful for powering multiple air tools or operating more demanding equipment (common in heavy construction and forestry), truck mounted and towable compressors can offer much higher capacities, while remaining mobile enough to transport from job to job

Specs

When comparing air compressors, there are a few key technical specs you’ll want to be familiar with:

• Single stage compressors are built with one cylinder and often cap out at 120 PSI. These compressors are usually adequate for home use and smaller shops

• Multistage compressors can handle higher PSIs, but due to the extra mechanical processes involved and extra heat generated, often need a radiator to help cool the machine

1 - Stages

• Gas – great option for portable compressors used at jobsites and off the power grid. Unfortunately they can often weigh over 200lbs

• Diesel – provide the highest level of output and are often seen on towable or truck mounted models

• Electric – one of the more common types of air compressor, these are typically lighter and more compact (as well as being environmentally friendly and safe for indoor use)

• *Protip – make a list of all air tools that will require power simultaneously and plan ahead. Under-buying can quickly burn out your compressor

2 - Power

Air Compressor Purchasing Guide

Specs

Cubic-foot-per-minute (CFM) – a measurement of delivery with respect to the inlet (gauges flow, not volume)

Pounds-per-square-inch (PSI) – measurement of pressure that results from one pound-force directed at a square inch (gauges resistance to flow)

Horsepower (HP) – references the power the air compressor’s motor can produce and is measured as either peak or running HP

Air Compressor Purchasing Guide

Additionally, there are a few definitions that will be helpful to know:

1

2

3

The above glossary terms have been listed in priority order, in terms of importance when comparing models.

*Protip: If you plan on powering multiple tools from a single compressor, add up the CFMs for each to ensure you’ll have enough power.

Choosing a Quality Seller

Air Compressor Purchasing Guide

1 - Questions to Ask

How long have you been in business?

What industries do you specialize in?

With my application in mind, what are some of the common problems other buyers have encountered with this compressor?

What type of warranty covers this air compressor?

What are your service hours? And how quick is your average response time?

2 - Warranties

If a full warranty isn’t offered, be sure to inquire about 3, 5, 7, or 10 year coverage on: Airends Variable speed drives Drive motors Rings Gaskets Suction/discharge valves Air/fluid receivers Driver couplers Coolers

A quality seller can be an enormous benefit in the selection process and post-sale support. Here are a couple lists that can help ensure you’re dealing with a quality seller:

Thank You

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Remember, for a more in-depth review of the topics mentioned here, please see our full-length Purchasing Guide:

http://www.purchasing.com/construction-equipment/air-compressors/purchasing-guide/

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