Allan,
I refer to the DOSATRON in another post. The worst part of using a venturi
or proportional injector is the radical drop in water pressure. I wasted
money on small venturi's - large ones are very expensive. Venturi's are
inaccurate, which is a function of physical properties such as viscosity and
temperatures etc....
The proportional injector is basically a water driven injection pump - you
set the mix rate (per pulse) on the instrument, and regulate the flow rate
by two different methods, depending on your plumbing arrangement (note -
these basic configurations can be used for any fertigation system):
First arrangement:
tank ---- pump ---- proportional injector ---- filter ----- irrigation
system
The proportional injector must be able to handle your pumping flow (volume)
and pressure. The DOSATRON can be set up to deliver the injected solutions
at very precise rates, and is used in medical applications.
Second, by-pass, arrangement:
tank ---- pump ---T--- hand-valve to regulate flow ---T --- filter ---
irrigation system
| |
| |
hand-valve to shut-off one-way-valve
| |
|---- proportional injector --------|
(with optional flow / volume restrictor)
The second arrangement caters for a smaller capacity proportional injector,
as the water is split between the two legs. The "hand-valve to regulate
flow" is needed to force the water through the proportional injector. It's
setting determines the pulse rate of the injector. Thus, by setting the mix
percentage on the injector, and setting the hand valve to X pulses per
minute, I can achieve an approximate dilution of 1:1000 :: EM:water, which
is the required application concentration of EM. This arrangement is not as
accurate as the first.
The problem with these instruments is that there are great frictional losses
in pressure and delivery volumes.
The alternative, grossly expensive, is an electric injector. I don't have
any experience with these.
These options are based on the assumption that you have a ball-valve or
float switch which controls the filling of the tank. The cheapest and
easiest solution is to add the desired amount of tea to your irrigation tank
if you have a batch system - i.e. full and pumped empty before filling
again.
Hope this helps.
Stephen Barrow
