Air compressors are critical pieces of equipment on most jobsites, used to power tools and complete many tasks. In choosing an air compressor, there is a wide variety of options available—with machines varying by size, weight, style, and output performance.
One key difference is choosing between an air compressor that uses an oil-lubricated pump and one that utilizes an oil-free design. Each style offers advantages for certain applications. It’s important to know the differences between the two styles and to consider some key factors when choosing the type that is right for your specific needs.
WHAT’S THE DIFFERENCE?
Some air compressors are designed with an oil-lubricated pump and others are designed to be oil-free. Just as with other large machines, proper lubrication in compressors and their pumps is essential to ensure long life and maximum service.
The two most common pump designs in air compressors used by contractors are:
Oil-free: This type of compressor does not use oil on the cylinder walls. Oil-free designs depend on the self-lubricating materials to allow the piston to slide in the cylinder and the grease in the sealed bearings.
Splash oil-lubricated: This type of lubrication relies on an oil dipper attached to the bottom of the connecting rod to randomly splash oil from the crankcase reservoir onto the bearings and internal parts of the compressor to keep them properly lubricated. This is the most common form of compressor lubrication and is used in most reciprocating-type air compressors.
Many air compressors on the market use oil-lubricated pumps, which means they require adding oil and changing oil on a regular basis—just as you would in a car engine. Oil-lubricated compressors have traditionally been a common choice for many contractors because they provide longer product life and offer the size and air capacity for several users to power tools simultaneously on the jobsite.
New advancements in oil-free compressor technology provide additional benefits such as extended product life and quieter operation, in addition to the maintenance-free ownership that this type of compressor has always offered.
FACTORS TO CONSIDER
For most contractors, the most important factor to consider when choosing between an oil-lubed and an oil-free air compressor is what type of jobs will be completed with the compressor—and how many workers might use the compressor at any one time. The more people tethered to the compressor, the more airflow needed to do the jobs.
Oil-free compressors can typically provide from 2 to 5 cubic feet per minute (cfm) of air flow and are driven by a 120-volt electric motor, which is enough to power trim nailers or complete finish work inside a structure. Compare that to oil-lubed wheelbarrow-style compressors, which can deliver 10 to 25 cfm of air. These compressors are generally engine-driven and provide enough power for heavier-duty tools or even a crew of up to 10 workers. Wheelbarrow-style oil-lubed compressors are typically used for roofing and framing work on the outside of a structure. Since they are engine-driven, they do not require power on site during this phase of construction and can power an entire crew.
Featured Image: Many contractors often use a larger oil-lubed compressor to power outside jobs like framing and roofing. These larger compressors can also power tools for multiple workers at once.
Above: Consider your needs and how you’ll be using the compressor before choosing the style that best meets your requirements. The right compressor—whether oil-free or oil-lubricated—will provide many years of reliable service when used in the right applications.
Many contractors like the flexibility of having both types of compressors. They may use a larger oil-lubed compressor to power outside jobs like framing and roofing—and often multiple workers at once—and then use oil-free compressors designed for quiet operation to complete smaller jobs inside a structure. This dual-compressor philosophy can provide greater versatility to meet the needs of many jobs and applications.
If having both types of compressors on your jobsite isn’t an option, keep in mind that cost is another consideration when choosing between the two styles—both the initial cost and the total cost of ownership over the life of the compressor.
Oil-lubed compressors are often two to three times the purchase price of an oil-free compressor, but they typically offer longer life and greater air capacity to power larger tools and entire crews. Most oil-lubed units have a working life of 100 to 15,000 hours with proper maintenance and oil changes, which are recommended after every 200 to 500 hours of use (depending on the type of oil used). Keep in mind that while oil changes extend the life of the compressor, they also need to be factored into the total cost of ownership for the air compressor.
An oil-free compressor, by comparison, has a lower cost of ownership over its lifetime because it does not require oil changes and has a lower initial purchase price. While the purchase price and ongoing maintenance is much less, oil-free compressors typically have a product life of around 200 hours, with higher-end units lasting up to 2,000 hours.
NEW ADVANCEMENTS IN OIL-FREE
Technology advancements in oil-free compressors have made new higher-end oil-free compressors better than old oil-free products. These advancements extend product life of this style of compressor for up to 2,000 hours of total life—which is up to four times longer than the average oil-free compressor and makes product life comparable to some conventional oil-lubed styles. The advancements also make the compressor much quieter, running 10 to 15 dBA quieter than oil-free units with older technology.
These advancements in oil-free units are mostly driven by the materials used in the sealing rings on the pistons. Additionally, most high-end oil-free compressors have pumps that run at half the speed of older compressors, which also contributes to longer product life and makes the units inherently quieter because they are running slower.
For example, the 6-gallon Quiet Compressor from Campbell Hausfeld has a 4-pole motor that runs slower, which helps extend product life, in addition to the oil-free pump design that provides maintenance-free and quieter operation.
CHOOSING THE RIGHT COMPRESSOR
Consider your needs and how you’ll be using the compressor before choosing the style that best meets your requirements. Always consider how large of a crew the compressor will be supporting, whether electricity will be available or if you need a gas engine compressor, and what fits your budget. The right compressor—whether oil-free or oil-lubricated—will provide many years of reliable service when used in the right applications.
About the Author:
Ben Echtenkamp is a commercial product manager with Campbell Hausfeld. For more information, visit www.campbellhausfeld.com.
Modern Contractor Solutions, December 2017
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