Spray Tip Selection - QTech QT830 User Manual

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SPRAY TIP SELECTION

Spray tip selection is based on paint viscosity, paint type and job requirements.
There are two variables that need to be identified - the tip orifice size and the
fan pattern width.
The main variable is the tip orifice. Generally use a smaller orifice tip for light
viscosities (thin coatings such as varnish) and a larger orifice tip for heavier
viscosities (thicker materials such as masonry, intumescents etc). Spray tip
orifice size is based around how many gallons of paint per minute can be
sprayed through the tip. At no time should a tip that can accommodate a flow
rate larger than the maximum of the pump be used.
The other variable is the fan pattern width. Two tips having the same orifice tip
size, but different fan widths will deliver the same amount of paint over a
different area (width of strip). A spray tip with a narrower fan width makes it
easier to spray in tight places. The thickness of the coat of paint per stroke is
determined by spray tip fan width, rate of the spray gun movement and the
distance to the surface.
The numbers that a tip is identified by indicate the fan width and the orifice size.
The first number is half the fan width in inches. The second two numbers identify
the orifice size in thousandths of an inch. For example, a 517 tip would have
a 10" fan width with a 0.017" orifice.
ATOMIZATION PRESSURE
The atomization pressure is the pressure at the gun. This will always be lower than
the pressure at the pump due to the viscosity of the paint - other variables that
will cause a pressure drop are the gun, the length and diameter of the hose, the
temperature and the humidity.
With these variables in mind, the operator will need to fine tune the pressure to
suit the actual conditions of the situation.
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SPRAY TIP REPLACEMENT
During use, especially with latex paint, grit and impurities in the paint under high
pressure will cause the orifice to grow larger from wear and for the fan pattern
width to degrade.
It is easy to determine the state of wear of the tip by observing the fan pattern.
As the tip wears, the fan width will become narrower. A new tip will have a
pattern shaped like a narrow long rounded-corner rectangle. As it wears it will
turn into an oval shape. When it is completely worn out it sprays a circle.
Once the fan width has decreased to about 2/3 of its original size, it should be
considered worn out.
NOTE: To minimize wear to the tip, piston, packings and seats, it is best to
always strain paint before use with a paint strainer bag and regularly clean all
filters and strainers.
Replace tips before they become excessively worn. Worn tips waste paint, cause
overspray, make cutting-in difficult, and decrease sprayer performance. If the tip
is the maximum rated size for your sprayer, when it wears, the flow rate capacity
will exceed that of the machine. If when using the maximum capacity tip size the
pump cannot keep up, then you know that the tip is worn beyond capacity.
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QTech QT830 Airless Sprayer