This page documents the alternative gel injection approaches that were considered but not adopted, as part of the design exploration. For the current design see Gel Dosing Overview; for the overall background see Gel Injection System.
Dosatron options evaluated
Several Dosatron-style proportional pump options were evaluated from Aliexpress before selecting the Huiji DN009:
| Model | Op. Pressure (bar) | Dilution % | Flow (L/min) | Thread | Price |
|---|---|---|---|---|---|
| DI16 (used by Wegener, now obsolete) | 0.3-6 | 0.2-1.6 | -- | -- | -- |
| D14MZ2 (replaces DI16) | 0.3-6 | 0.2-1.6 | 0.19-50 | NPT | ~$1,568 |
| D8 | 0.34-8 | 0.2-5 | 0-120 | -- | ~$1,530 Aliexpress |
| D25RE2 | 0.3-6 | 0.5-2 | 0.6-41 | 25 | $135 Aliexpress |
| Huiji DN009 (selected) | 0.2-6 | 1-10 | 0.8-42 | ?? | $223.31 inc GST & freight |
The Huiji DN009 gives 1-10% dilution at 0.2-6 bar with 0.8-42 L/min flow -- the widest dilution range at the lowest cost. Matt Wegener's full-flow approach (passing the entire 120+ L/min main through the Dosatron) required the expensive D14MZ2 (~$2,500 AU). A bank of four D25RE2 units in parallel was also considered but rejected as overly complex.
Alternative 1 -- Electric dosing pump
An alternative would have been a battery-powered 12V electric dosing pump injecting directly into the main line. Options considered:
- (i) ~$18.74, max outlet pressure 800 kPa, max flow 5 L/min -> dilution 5/120 = 0.8%.
- (ii) STARFLO 12V high-pressure diaphragm pump -- 4 L/min open flow, up to 5.5 bar, 2.6A. USD 9.00. Flow-vs-pressure curve not published.
- (iii) LEFOO 200GPD diaphragm pump -- 220W, 24V DC, 0.5 MPa, 1.9 A, 1900 ml/min working. Dilution ~1.9/120 = 1.5%.
- (iv) 12V irrigation pump BLD-09 -- 3-7 bar, 60W, max 6 L/min. USD 5.80.
- (v) 12V 100W diaphragm pump -- 8 L/min, 70m head, 100W. USD 58.90.
- (vi) RANKING FL86 12V DC 220PSI 220W 5-chamber diaphragm pump -- 15 LPM, 50m head.
- (vii) OSPump DP-60 -- 150m head, max 9.5 L/min, 12V. At 45 psi delivers 4 L/min (dilution ~3.3%) or 3.2 L/min at 60 psi (~2.6%). Possibly within range, but power draw and uncertain dose compared with the Dosatron speak against it.
The Dosatron is preferred because its dose is self-proportioning (concentration independent of pressure), it draws no electric power from the main line (it is powered by water flow), and the boosterless design eliminates the only remaining objection (needing to boost pressure above system ambient). See current design.
Alternative 2 -- Venturi injectors
Venturi injectors use a constriction in the feed line to create a partial vacuum that draws dosing fluid into the water stream. Commercial options include the Amiad 4-01 fertiliser injector kit ($1,260.05) and the 50mm Mazzei Venturi Fertilizer injector ($712.25). However, venturi injectors do not work reliably under back-pressure conditions, which is the normal operating condition for the ARMAC delivery line. Rejected on this basis. (Reference: Land&Water Technology website.)
Alternative 3 -- Pressure reduction valve bypass loop
Since the system has a pressure reduction valve for low-flow mode, a valve-controlled loop around it could theoretically draw fluid from a barrel. However, this would require all components to withstand the full ~7.3 bar (105 psi) system pressure and introduced additional complexity. Not pursued.
For more background and technical detail refer to Electronically controlled Valves, Motorised 3-way (and 2-way on/off) valves.
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