EQUIPMENT

How Direct Injection Systems Work

Chemical direct injectors provide one of the most effective ways
of applying precise doses of several chemicals to different parts
of a field. The system automatically mixes pure chemical and
carrier on-the-go and adjusts the spray rate in accordance with
the change in ground speed of the sprayer. The result is an
assurance of exact application rates.

Injection systems use either a piston pump on the injection side
to inject the chemical into the carrier for in-line mixing, or a
series of peristaltic pumps to ration a specific quantity of
chemical into the carrier on the inlet side of the carrier pump
close to the boom.

Practically speaking, a rig equipped with a direct injection
system is able to spray one crop in one part of a field, then
spray an entirely different crop in another part of the field
with an incompatible chemical without losing time due to tank
mixing. With no leftover solution, there is no chemical waste.
And best of all, the process is controlled from the cab so that
risk of chemical exposure to the driver is virtually eliminated. 

How the System Works

The direct injection system provides custom chemical application
with little need for physical adjustment of machine parts by the
driver/applicator. The process goes like this:

1. Cable signals from the rate controller are sent to the
   chemical tanks and chemical injection pumps, and the carrier
   tank. At the prescribed rate--partially determined by the
   sprayer's ground speed--the chemical and carrier go through
   the suction line.

2. The chemical and carrier are blended in the in-line mixer,
   then the solution runs through the in-line filter and passes 
   the flow control valve.

3. The amount of solution to be sprayed is regulated by the flow 
   meter.

4. Finally, the exact amount of several chemicals (up to four or
   five on most models) is dispensed from the spray booms in
   varying doses. This not only allows incompatible chemicals to
   be sprayed in one pass, but also eliminates chemical waste.

5. Most injection systems are compatible with global positioning
   system (GPS) receivers. With GPS hookup, the entire process
   starts when field information is picked up by a GPS receiver.
   That information is then sent to a computer with a mapping
   program and relayed to the control console inside the cab.

(Prepared by: Vernon Hofman, Extension Agricultural Engineer).