-23 TA 1-- 6 f. ut 1946
United States Department of Agriculture
Agricultural Research Administration
Bureau of Fmtomology and plant Quarantine
A POWER SPRAYER FOR APPLYING CONCENTRATED INSECTICIDES
By Joseph N. Tenhet
Division of Truck Crop and Garden Insect Investigations l/
In connection with the development of a concentrated pyre-
thrum-oil spray for use in tobacco-storage warehouses, it was
found necessary to design a new type of spray machinery, since
no commercial spray equipment was found which could do the work
desire&. The machine herein described was developed in 1942 from
the original ideas of the author.
Domestic cigarette types of tobacco are customarily stored
in wooden hogsheads of approximately 1000 pounds net weight, and
having a length of 48 or 54 inches and diameter of 48 inches.
These hogsheads are stored lying on their sides with their ends
very close together (fig. 1), and they are usually racked three
tiers high. Tobacco warehouses vary considerably in size, but
always have one feature in common: the floor space is almost com-
pletely covered with hogsheads except for an aisle about 10 feet
wide. This aisle is generally across the middle of the warehouse,
but is sometimes at one end or side of the building. Since the
tobacco hogsheads extend to a height of 10 to 12 feet above the
floor, it is impracticable to climb about over them with spray
equipment. Consequently the most feasible method of applying spray
is from the aisle. This means that the spray must be driven a dis-
tanoe of 30 to 100 feet, depending upon the size of the building.
In most warehouses the distance does not exceed 75 feet.
Spray applied in a tobacco warehouse must be finely atomized
to avoid wetting the hogsheads. Any appreciable wetting or deposit
of spray material is considered objectionable. Spray guns such as
are employed on large trees could not be used because they deliver
a solid stream of liquid. No orchard spraying equipment could be
found that would drive an atomized spray more than 3) feet.
l/Acknowledgment is made of indebtedness to W, D. Reed, who
supervised the work during its early stages, and to C. E. Broaden,
of the American Tobacco Company, and M. E. Turner, of the R. J.
Reynolds Tobacco Company, for assistance in the mechanical develop-
ment and construction of this machine.
Another problem was the time-volume factor. Orchard sprayers
are designed to deliver a large volume of Uquj, rapidly. In
spraying tobacco warehouses it was desired to Ieliver a small
amount of liquid (about 6 gallons in a large warehouse) slowly
enough to obtain adequate coverage. This time proved to be 20 to
30 minutes for most warehouses.
The machine designed to meet the foregoing specifications is
believed to embody a new application of well-known principles, end
the results obtained with it under commercial conditions have been
highly satisfactory. Although developed priarily for use in
tobacco warehouses, there seems to be no reason why this machine
should not prove satisfactory for use in other storage warehouses
and in ship holds. Perhaps under certain conditions it may also
be found to have a use in outdoor applicatbis of insecticides.
The machine consists of a small orchard-type spray tank and
compressor, a blower, an. atomizing unit comprising a group of oil-
burner type nozzles, and two electric motors (fig. 2). The corn-
pressor, A end the motor, B which operates it, are mounted on
top of the tank, C. The compressor, although capable of delivering
400 pounds of pressure, was usually operated at 300 pounds. It
was found necessary to enlarge the buffer air chamber, D. A gage
mounted on the rear of the tank shows the liquid contents at a
glance. The blower, E is mounted in front of the tank on an ex-
tension of the chassis, as is the motor, F that operates it.
From the blower an air stack, G. extends upward to a height of 7
feet. The top of this stack is bent over slightly, and the spray
nozzles, are placed in the mouth. The machine is so designed
that the spray is delivered upward at an angle of approximately
150 to 2CPfrom the horizontal, and as it leaves the nozzles it is
caught and driven by the blast of air from the blower (fig. 3).
The machine is similar to a power duster, except for the adapta-
tions necessary to the use of a liquid spray.
Tank--Capacity not more than 50 gallons, equipped with strainers
and a gage. Construction should be in accordance with stan-
dards of the National Board of Fire Insurance Underwriters.
Compressor--Reclprocal type, 2-cylinder, capable of delivering
400-pounds of pressure.
Air (or buffer) chamber--3 inches in diameter and 24 inches
in length or 4 inches in diameter and 15 inches in length;
the latter is preferable.
Blower--Air-pump type, capable of delivering 1250 cubic
feet of air per minute at 1725 r. p. m.., with fan of
Air staok--A pipe 8 inches in diameter and 7 feet high, and
bent over at an angle of approximately 750- 8o from the
Nozzles--10 of the oil-burner type, mounted in the mouth
of the air stack, each nozzle capable of delivering 1.5
gallons of No. 2 oil per hour, at 100 pounds of pressure.
Motors--2 electric, 1 hp., 220- 40 volts, 1.48-2.96 amperes,
1725 r. p. m., 60 cycles, 3-phase spark proof.
This machine will blow a finely atomized fog of spray 75 to
80 feet over the hogsheads of tobacco, as customarily racked, three
tiers high, in an open-type warehouse. Where there are no obstacles
in the path of the spray, and in a closed building, it will readily
drive the spray 100 feet or more. Even with a light breeze blowing
through the warehouse at right angles to the path of the spray,
this machine will drive the spray from 50 to 75 feet. Under such
conditions fairly satisfactory coverage is obtained by operating
the machine longer on the windward side of the building and allow-
ing the breeze to drift the spray across the warehouse.
For use in very large warehouses, where it is necessary to
drive the spray 100 feet or more, or where the hogsheads are
racked with dunnage between the tiers. the machine was modified
by using a taller air stack with a fishtail outlet. With the
taller air stack the spray can be delivered horizontally across
the tops of tiered hogsheads. In many warehouses the rafters are
STAT PLANT BOARD
at right angles to the path of the spray, and when the spray is
delivered upward at an angle the rafters tend to act as baffles
and reduce the distance the spray can be driven. By delivering
the spray in a horizontal plane, the difficulty is overcome. This
machine is a little more awkward to handle, and a 12-foot air
stack will not pass through ordinary doorways. Therefore, it
is necessary to hinge the stack so that it can be lowered for
moving from one warehouse to another. Such a sprayer, with the
air stack lowered, is shown in figure I.
Figure 1.--Interior of tobacco-storage warehouse showing
arrangement of hogsheads.
Figure 2.--Power sprayer developed for use in tobacco
Figure 3.--Power sprayer in use in tobacco storage
UNIVERSITY OF FLORIDA
3 1262 09240 8722
Figure 4.--Power sprayer developed for use in very large tobacco
storage warehouses, showing the tall air stack lowered.