TM 43-0139
e.
Defective Spray Patterns
(1)
Heavy top pattern is due to:
(a)
Horn holes that are partially plugged.
(b)
An obstruction on top of the fluid tip.
(c)
Dirt on the air cap seat or fluid tip seat.
(2)
Heavy bottom pattern is due to:
(a)
Horn holes that are partially plugged.
(b)
An obstruction on the bottom side of the fluid tip.
(c)
Dirt on the air cap seat or fluid tip seat.
(3)
Heavy right side pattern is due to:
(a)
The right side of the horn holes is partially clogged.
(b)
Dirt on the right side of the fluid tip.
(c)
On a twin-jet cap, the right jet is clogged.
(4)
Heavy left side pattern is due to:
(a)
The left side of the horn holes is partially clogged.
(b)
Dirt on the left side of the fluid tip.
(c)
On a twin-jet cap, the left jet is clogged.
(5)
Heavy center pattern is due to:
(a)
The spray width of the adjusting valve is set too low.
(b)
The twin-jet cap, because the atomizing pressure is too low, or the material is of too great a viscosity.
(c)
The pressure-feed fluid pressure is too high for the air cap's capacity.
(d)
The nozzle is too large for the material being used.
(6)
Split spray pattern is due to an imbalance in the air and fluid pressure.
(7)
To remedy the conditions described in (1) through (4) above, determine if the obstruction is on the air cap
or the fluid tip. Rotate the cap one-half turn and spray a test pattern. If the defect is inverted, the obstruction is on the air
cap; if it is not inverted, the obstruction is on the fluid tip. Clean the air cap as instructed in paragraph 5-6. See figure 5-8
for examples of the conditions described in (1) through (4) above.
(8)
To remedy the conditions in (5) and (6) above, readjust the atomizing pressure, fluid pressure, and spray
width adjustment until the desired spray is obtained. See figure 5-8 for examples of the conditions described in (5) and (6)
above.
5-11
