Agriculture Reference
In-Depth Information
agitation and adequate withdrawal rates in both tanks. All tanks should have a
gauge to show the liquid level. External gauges should be protected to prevent
breakage. All tanks should have a shut-off valve for storing liquid pesticide
temporarily while other sprayer parts are being serviced. Figures 8.9A - E
show boom sprayers with large tanks.
2.
Pumps
The pump must have sufficient pumping capacity to supply the needed
volume to the nozzles and to the hydraulic agitator (if necessary) and to main-
tain the desired pressure. The pump parts should be resistant to corrosion and
abrasion if abrasive materials such as wettable powders are to be used. Select
gaskets, plunger caps, and impellers that are resistant to the swelling and
chemical breakdown caused by many liquid pesticides. Consult your dealer for
available options.
Never operate a sprayer pump at speeds or pressures above those recom-
mended b the manufacturer. Pumps will be damaged if run dry or with re-
stricted inlet or outlet. Pumps depend on the spray liquid for lubrication and
removal of the heat of friction.
a.
Roller Pumps
Roller pumps are among the least expensive and most widely used of all
sprayer pumps. They provide moderate volumes (8 to 30 gpm) at low to
moderate pressure (10 to 300 psi). Often used on low-pressure sprayers, roller
pumps are positive-displacement, self-priming pumps. The rollers, made of
nylon, teflon, or rubber, wear rapidly in wettable powders but are replaceable.
A pump that will be subjected to such wear should have a capacity at least 50
percent greater than that needed to supply the nozzles and agitator. This re-
serve capacity will extend the life of the pump. The pump case is usually cast
iron or a nickel alloy. Roller pumps are best for emulsifiable concentrates,
soluble powders, and other nonabrasive pesticide formulations ( Figure 14B ).
b.
Gear Pumps
Gear pumps are used on sprayers with low operating pressures. They
provide low to moderate volume (5 to 65 gpm) at low to moderate pressures
(20 to 100 psi). Often used on special-purpose sprayers, gear pumps are posi-
tive-displacement, self-priming pumps. The self-priming ability is rapidly
lost as the pump wears. These pumps are designed for oil solution formula-
tions and wear rapidly when suspensions of wettable powders are used. The
parts are generally not replaceable. The pump is not affected by solvents,
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