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. |
