Air Compressors, Airless Paint Sprayers Buyer's Guide
The term airless refers to the fact that paint is pumped under high pressure, generally 1500 to 3500 PSI, to a spray tip on a spray gun at the end
of a 50 to 300 foot high-pressure paint hose.
by Robert Simpson
revolutionized an industry the way airless spray technology did after its introduction in 1958. Airless paint sprayers are now the most used tool in a contractor’s arsenal, so selecting the correct machine will help to improve productivity and profits.
Airless sprayers are relatively unpretentious pieces of equipment. They sport a motor, a pump to drive the coating through a hose, and a constricted nozzle that speeds and atomizes the coating as it escapes. “Airless sprayers operate on a simple, well-understood concept. Force a volume of paint through a confined space under pressure and a stream will emerge to strike the surface. Airless sprayers are application tools designed to paint large areas very quickly,” says Paul Wood, Export Manager for Moorpark, California-based Airlessco.
The term airless refers to the fact that paint is pumped under high pressure, generally 1500 to 3500 PSI, to a spray tip on a spray gun at the end of a 50 to 300 foot high-pressure paint hose. Here the paint is atomized into very small droplets directed toward the object being painted. The paint flow is regulated by the size of the spray tip and the pressure generated by the airless unit.
The amount and kind of work a contractor intends to do with an airless sprayer will determine the type of machine best suited for the job. “The difference between a big machine and a small machine is how quickly you get the job done,” says Wood.
The most common reason why professional paint contractors use airless sprayers is the speed of application-thus more jobs can be completed in less time using less labor. According to research conducted by the Painting and Decorating Contractors of America (PDCA), a professional association of painting contractors and related industry professionals, airless spraying can save painters between 50 and 75 percent of their painting time-airless spraying is four times faster than brush applications and twice as fast as roller applications.
Versatility is often cited as another motivating factor for selecting airless sprayers. Airless sprayers can be used for a wide range of coating materials, including interior and exterior jobs, and most can easily be transported from site to job site.
But selecting the right machine can be a daunting task if a contractor does not have good understanding of how airless sprayers are rated by manufacturers.
The principal method of rating airless sprayers is based on gallons per minute (GPM), a flow rate measurement associated with the pump’s output capacity and the tip orifice (hole) size. “The GPM is very important because it explains how much work the machine can do,” says Mike Peterson, marketing manager of Minneapolis, Minnesota-based Wagner/Spraytech.
But caution is advised. There is no single industry standard for rating a sprayer’s output capacity. Some pump manufacturers rate the sprayer’s capacity as free flow capacity. This means there are no restrictions (tip, gun, or hose) and the pressure is not at a level that can atomize paint. A second approach is to rate the GPM with the actual tip size a sprayer can support.
The maximum delivery rating indicates the amount of fluid that can flow through a particular tip, gun and hose. If, for example, the machine is rated for (.33) 1⁄3-gallon-per-minute the largest tip that can be used is a .015; for 1⁄2-gallon-per-minute it increases to a .021 and one-gallon-per-minute to a .031.
Pounds-per-square-inch (PSI) measures the maximum working pressure of the sprayer, that is, the maximum amount of pressure the sprayer is able to build. It should be remembered, however, that the pressure at the tip does not equal the maximum working pressure-hose length, tip size and the type of coating being sprayed all impact the amount of pressure at the tip while spraying. “Most airless sprayers range between 2,500 and 3,000 PSI and the typical atomization pressures required for latex coatings is above 2,000 PSI, while lacquers require 800 to 1,100 PSI and stains 1,200 to 1,800 PSI,” says Peterson.
Horsepower refers to the sprayer’s motor or engine. There are a variety of motor types, operating speeds and torque capacities available. This makes horsepower a confusing rating method for distributors and end users alike. Some contractors prefer to have the biggest motor available because they believe it means more power and longer sprayer life. However, more power doesn’t translate into getting the job done more quickly.
Dana Scharck, director of marketing and sales for Peosta, Iowa-based MI-T-M Corporation, thinks that paint contractors who choose airless sprayers based only on the GPM and PSI may be setting themselves up for disappointment. “The GPM and PSI game is way over-rated and contractors need to consider if the engine’s horsepower is large enough to provide the flow rate,” says Scharck.
is PSI x GPM divided by 1,460 x 1.5. Using this formula, a 3,000 PSI unit at .5 GPM requires a 1.6 horsepower engine. “Too often manufacturers put machines on the market with engines that are too small to perform over the long term. We preach horsepower,” says Scharck.
Maximum tip size is a rating that indicates the largest tip size a sprayer is capable of supporting, while maintaining a good spray pattern. The maximum tip size will depend on the type of coating being sprayed and the amount of pressure required to atomize the coating.
Three levels of airless sprayers are available. The smaller machines are manufactured with the home handyman in mind. Generally these machines are low-cost with small diaphragm and piston pumps. These small sprayers tend to be around 1⁄3 GPM. The next level of airless sprayer is designed for contractors, pumping .4 to .5 GPM and ideal for a contractor who uses the pump on a regular basis. The largest machines are rated at 1 GPM and higher and suitable for the large-scale contractor or individual who regularly applies heavier bodied coating.
1. How many gallons per week will you be spraying?
2. On what types of jobs will you be bidding-large scale or small and intricate?
3. How much money do you want to spend? Remember the cliché, “You can pay now or pay later.” Downtime from an undersized, overworked sprayer can wipe out any savings from the initial purchase.
4. What power sources are most available?
5. What materials will you be spraying? The type of material will determine the size of the tips.
Airless sprayers are available with two general types of pumps: diaphragm and piston.
A diaphragm pump will typically use the sprayer’s motor to create pulsing hydraulic pressure to drive the pump. During the upstroke or intake stroke, the diaphragm creates a partial vacuum and draws paint into the chamber. On the down stroke or pressure stroke the paint is discharged from the chamber to the sprayer hose.
“The diaphragm pump is less expensive to manufacture and is often found on smaller machines, but they operate at a much higher speed and cycle at the speed of the power supply — 1,725 revolutions a minute minimum. So they are sucking and pumping very small amounts of paint very fast. This results in more wear and tear on the parts and more maintenance,” says Wood.
“The primary advantage of the diaphragm pump was price and the zero fluctuation in the pump pressure (dead band), but in the last few years these advantages have been reduced or eliminated as piston pumps have come down in price and minimized pressure fluctuations-the perception is that diaphragm pumps are almost a thing of the past,” says Tony Tortore, vice president of sales for Minneapolis, Minnesota-based Spraytech Inc.
Brian Ray, president of Burnaby, British Columbia H.E.R.O Industries disagrees. “There is still a strong market for diaphragm pumps. They have fewer moving parts and are easier to clean and repair-that is an important factor in the equipment rental market, and an important function of the smaller jobs (e.g. enamel and lacquer work) that many contractors face each day,” says Ray.