Airless spray systems atomize coating by forcing a fluid through
a small orifice at high pressure. (Think garden hose water sprayer.) They are
prized for their high production rates that can exceed 2 gallons per minute for
larger models.
Airless sprayers provide pressure from either a diphragm or
piston pump unit driven by an electric, gasoline, or air power motors. Some
models use a hydraulic driven pump powered by electricity or gasoline power.
The hose is an integral part of the system. Its expansion and contraction
provides volumetric cushioning of the fluid to provide steady paint flow at the
tip. It also conducts static electricity build up back to the sprayer where it
can be grounded.
Two things primarily determine the capacity of an
airless sprayer: Horsepower and Valve Openings. Many companies use one pump on
a variety of models. The difference comes from the motor and powertrain with
changes in horsepower or motor type. Bigger pumps have bigger valves and bigger
valves means more heavier fluids can pass through. For example, a small pump
such as the Graco 395 Ultra or SprayTECH 2105 has insufficient horsepower to
push elastomeric coatings. As the same pump body is put onto larger motors, its
ability to pump more fluid increases because the motor can turn it faster.
However, because of faster cycling, you can expect more wear than a larger
capacity pump.
One of the most important rules with airless sprayers is
to keep the pump clean. A dirty or rusted piston pump will quickly destroy
itself by eroding its packings, rod, cylinder and or valves.
Graco
sprayers are some of the best known on the market. They have a selection of
pumps that fill just about every niche one can think of for spraying liquid
coatings. Their recent homeowner line, the "Magnum" series is an attempt to
bring piston pump sprayers to the homeowner/DIY buyer. These are different than
their professional equipment because they are made with less durable materials
and a sport only a single action pump. They feature some of the desirable
properties of their larger brethren such as upright carts, hose reel on the
handle, manifold filters etc. However, much of this is light duty from a usage
point of view and these were not made for continuous use. In fact, parts for
the Magnum series are limited with pump repack kits not made at all.
Stronger motors can push higher loads of paint through larger orifices
and increase production for professional users. Bigger pumps with larger valves
are required for heavier viscosity liquids or for fulfilling the needs of large
volume users and these take bigger and bigger motors. Sprayers can be powered
with electric, gasoline, hydraulic or air motors.
The professional
painting contractor usually uses portable electric motor equipment but for
areas where electricty may not be available such as on large warehouse
projects, high rises, or new construction, gasoline power is preferred. Air
motors are typically used inside factories or shop application where large
compressors can keep them going without threat of fire or heat build up.
Hydraulic units are actually powered by gasoline or electric motors but produce
more power in a more compact design with less wear than if an equivalent
electric or gas motor. Of course, the hydraulics add complexity to the overall
package and cost at the time of purchase.
Specialty units include
texture sprayers for application of wall finishes such as spatter coat or
knockdown. These combine a specialty pump designed for heavy liquids and an air
compressor to spray the material on the wall. |
