The gun and the spray tip of an airless paint sprayer have the most direct impact on the quality and efficiency of the job. They also can be the components given the least consideration by rental dealers.

The spray tip is the least understood of the two components. It helps determine the quality of the job. There are flat and reversible tips for airless paint sprayers as well as special tips designed for airless line stripers.

One of the first things to understand is how airless spray tips are sized. The industry standard is that the first digit stamped on the tip is half of the spray fan width when the tip is held 12 inches from the surface. For example, a 517 spray tip — five times two equals a 10-inch spray fan. The second set of digits identifies the diameter of the tip orifice measured in thousandths of an inch (the 517 a .017-inch-diameter orifice).

Although a few tip sizes are the most popular, it would be a mistake for rental dealers or customers to use just these as a guide. The most popular sizes are the .015 and .017 because the majority of rental airless pumps flow at a half-gallon per minute. With sprayers this size, capacity is the most significant determinant of tip orifice size. Some rental dealers and contractors with larger sprayers require larger tips in order to work at a speed their pumps can support. Moreover, customers applying lacquers, oil-base enamels, stains, sealers or other light coatings require smaller tips.

Abrasion and corrosion

Tip wear rate depends on the abrasiveness and corrosiveness of the material being sprayed along with the flow and pattern width. The number of gallons that wears the tip to the next larger size varies from a few gallons to 100 gallons. Usually, the cheaper the paint, the quicker the wear. Coatings that contain more abrasive solids result in faster wear.

Rental centers should replace worn tips as soon as they adversely affect spray pattern and pump performance. Many savvy paint contractors who spray high quantities of contractor-grade latex paint replace their tips every day. A rule of thumb is to replace each tip after five rentals.

Remind your customers to spray at the lowest pressure that will atomize their paint. It saves paint and money. Before painting, the spray pattern should be tested on cardboard. Set the pressure on the low side and raise it until the “tails” are gone and coverage is uniform. This reduces tip wear, prevents over-spray and gives the best finish.

Proper settings

Several major airless sprayer manufacturers have added solid-state pressure readouts to their sprayers. These readouts help customers adjust to the proper pressure setting for the material being sprayed. For example, lighter-viscosity fluids such as stains require spraying pressure to be 450 to 800 pounds per square inch, and latex, 1,700-2,200 psi. A number of paint manufacturers also list on their labels the proper spraying pressure for their product. The pressure readout also helps your maintenance department monitor machines' performance and speed up trouble-shooting.

Another important factor to consider is the flow capacity of the pump being used. If the tip is too large or worn, the sprayer won't be able to keep up, and the spray pressure will drop. It is also important to select a tip that is not too close to the maximum flow rate of the sprayer.

In addition, consider the coating to be applied. Coatings have variables such as water base, solvent base, percentage of solids, particle size (that must pass through the tip orifice) and atomization pressure. Another factor in tip selection is application requirements such as surface area thickness and the speed of the gun movement. To help select the proper tip size, see the Tip Selection Chart (right).

Remember, before renting your airless, don't forget the tip. Check it for wear and change it frequently to ensure your customer will get a professional paint-spraying job. Also be sure that when the unit is returned, the spray unit, gun and spray tip are cleaned. Once a standard check-in and check-out procedure is established, airless sprayers can become one of your most profitable rental items.