Popularity can be an indicator of performance, and that has long been the case for portable rotary screw air compressors with 185 cfm of free air delivery and at least 100 psi of working pressure. Ease of transport, compactness and the ability to crank out air for eight to 10 hours of uninterrupted use allows these units to dominate on a jobsite. If you’ve got a job that requires pneumatic tools for hammering, chipping, drilling, painting or sandblasting, a portable compressor in the above category or similar will deliver more than enough air to power through.
For heavy-duty jobs you may need a larger, two-stage rotary air compressor, but for standard light-duty construction, a single-stage rotary screw air compressor can usually handle the work.
Most common pneumatic tools, such as a jackhammer or rock drill, require between 90 to 110 psig. Air consumption, on the other hand, depends on the size of the tool. Take note of your tools’ air pressure and consumption rates to determine how much air volume your compressor needs to produce.
A compressor with a higher available pressure rating isn’t always better. “If you have a 90-psi air hammer, for example, and you jack it up to 125 psi, it will work harder,” says Eric Massinon, sales manager, GrimmerSchmidt. “But that’s only going to cause more wear and tear on the tool. Some tools do better with higher pressure, while others don’t. It just depends on what you’re using.”
(To see a list of common air tools’ consumption ratings, visit Jenny Products’ site at http://www.jennyproductsinc.com/howtochoose.html.)
You may run into other air pressure restrictions if you use a longer hose, as pressure drops the further it gets from the compressor. “If you experience serious pressure loss, check for air leaks,” Massinon says. “You can turn up psi to accommodate an air loss, but make sure to repair the leaks as soon as possible.”
A few key improvements in air compressor design over the past few years stand out. “Today’s portable rotary screw compressors are designed with two major issues in mind: energy efficiency and noise abatement,” says Chance Chartters, direct accounts manager, Kaeser Mobilair.
To allow users extended operation and improved fuel efficiency, compressors need more than just a large gas tank. “Units that pair oversized airends with motors turning at slower speeds offer better air-per-fuel consumption ratios,” Chartters says.
Some manufacturers have embraced plastic instead of steel to increase the canopy’s durability and reduce noise levels.
Most units offer lower noise ratings, typically between 72 to 74 decibels audible. OSHA requires compressors to be at least 76 dbA or less. “Noise pollution can be significantly reduced by a fully-enclosed package with a solid floor,” Chartters says. Enclosures with a solid steel floor, such as Kaeser’s, and a layer of sound-dampening foam help minimize noise.
Atlas Copco adopted the polyethylene canopy for its Hardhat oil-injected rotary screw compressors, introduced in the United States last year. “Compared to fiberglass or steel, this technology is able to withstand much more wear and tear,” says Attila Madarasz, product marketing manager, compressors, Atlas Copco. The double-walled Hardhat canopy muffles noise and returns to form if it’s struck. It also resists cracking, fading, corrosion and rust. “It’s not painted like a steel unit – the dye goes all the way through – so it doesn’t have paint that flakes off,” Madarasz says.
A durable plastic-like shell can save you money on external repairs. “We estimate external repairs expenses cost customers an average of $3,500 within three to five years of use,” Madarasz notes.
Lightweight, aerodynamic canopy models like Ingersoll Rand’s AirSource line can also increase a towing truck’s fuel economy, explains Rus Warner, small compressors and lighting systems product marketing manager, Doosan Infracore Portable Power. “Even on our traditional product (the Ingersoll Rand P185) we were able to modernize with new materials. We now use end caps with the same product technology as the AirSource, but the doors are steel,” Warner says.
Safeguard your site
Never use a compressor to clean dirt or debris off of a person, and be cautious when using compressed air to clean work areas. “Even the smallest piece of debris, such as metal shavings, wood chips or gravel, flying through the air at high velocities can be dangerous,” Chartters says. Not only is it an OSHA violation (with air more than 30 psig), air compressor misuse can result in serious eye injuries, skin abrasions or worse.
Also consider where to set up the compressor. “Try to keep it on firm, level ground,” Warner notes. “Chock the wheels, so it won’t roll anywhere, and know where the hoses will run. You don’t want them near a machine or in a high-traffic area where they could get snagged.” To be safe, use hose retainers so if the hose accidentally releases it won’t hit someone.
Compressors in the 185-cfm range should be towed by a 1/2-ton or 3/4-ton truck or utility vehicle with a gross vehicle weight rating of 2,000 pounds or more. Before you set out for the jobsite, check off the points below to ensure a safe haul.
- Examine the tires for excessive wear and check the tire pressure.
- Ensure pressure and temperature gauges are working.
- Tighten bolts and fittings, if necessary.
- Attach the safety chain to the towing vehicle, so it can support the load if the coupling accidentally disengages. Leave enough slack for the chain to catch the tow bar, but do not allow the chain to drag the ground. The vehicle should be able to turn without pulling the chain tight.
- Always match the vehicle’s ball hitch to the compressor’s tow bar.
- Check all lights before towing.
Tips provided by Kaeser Compressors.
For users who want a more permanent alternative, vehicle-mounted compressors are available. Truck-mounted (either above deck or below) units vary in size from 20 to 70 cfm, and larger underdeck units go up to 185 cfm. Similarly, underhood air compressors range from 1 to 150 cfm, with up to 175 psi. Most models fit Class 2 trucks or larger. Vehicles equipped with power take off (or PTO), such as Class 6 and 7 trucks, can handle a number of different compressor options.
Vehicle-mounted air compressor manufacturers cite their advantages: “They free up a tow hitch, costs less in vehicle insurance, require less engine maintenance and are easier to navigate as towing a trailer becomes unnecessary,” says Dan Hutchinson, product management specialist, VMAC. They also increase vehicle maneuverability in tight areas, allow use of the truck chassis and eliminate a theft target from the jobsite, according to Vanair.
Doosan Infracore Portable Power