ARMAC DevNotes · pages: Overview · Design & Calculations · Throttle Pressure-Drop Tables · Build & Commissioning · Calibration
The boosterless design is driven by the pressure drop the manual throttle tap develops when it brings delivery down from wide-open flow to the throttled sprinkler flow. Because that flow reduction was originally a guesstimate, the tables below give the resulting drop across the tap (DeltaP) and the low-side pressure for every combination -- so once the two flows are measured, the real numbers are a lookup, not an estimate.
Model
Two well-established relations, no fitting beyond reading the pump curve:
- Pump head h(Q) -- digitised from the 10 HP High-Flow 3" curve. Shut-off 5.30 bar (530 kPa), essentially flat to the knee at ~400 L/min: h(120) ~= 5.08, h(220) ~= 4.92 bar.
- Sprinkler square law -- sprinklers are fixed orifices, so P_spr proportional to Q^2. Anchoring at the wide-open point (tap out of circuit, sprinklers see ~= pump head):
P_low = h(Qopen) x (Qdel / Qopen)^2 DeltaP_tap = h(Qdel) - P_low
Qopen = wide-open (unthrottled) delivery; Qdel = throttled delivery to the sprinklers. Cells with Qdel > Qopen are non-physical (a throttle cannot raise flow) and are shown as middot.
Reading it for the branch: the Dosatron needs only ~0.5 bar of drop to run, so any cell with DeltaP >= 0.5 bar drives the branch -- essentially the whole physical region. The Dosatron inlet parks at roughly P_low + 0.5 bar, always well under its 6 bar ceiling. The design point (Qopen ~= 220, Qdel = 120) reads DeltaP ~= 3.6 bar, P_low ~= 1.5 bar.
Table 1 -- DeltaP across the tap (bar): the branch driving pressure
Rows = wide-open flow Qopen; columns = throttled delivery Qdel (both L/min).
| Qopen \ Qdel | 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 | 210 | 220 | 230 | 240 | 250 | 260 | 270 | 280 | 290 | 300 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 100 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 110 | 0.9 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 120 | 1.6 | 0.8 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 130 | 2.1 | 1.5 | 0.8 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 140 | 2.5 | 2.0 | 1.4 | 0.7 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 150 | 2.9 | 2.4 | 1.8 | 1.3 | 0.7 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 160 | 3.1 | 2.7 | 2.2 | 1.7 | 1.2 | 0.6 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 170 | 3.4 | 3.0 | 2.6 | 2.1 | 1.6 | 1.1 | 0.6 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 180 | 3.6 | 3.2 | 2.8 | 2.5 | 2.0 | 1.6 | 1.1 | 0.6 | 0.0 | · | · | · | · | · | · | · | · | · | · | · | · |
| 190 | 3.7 | 3.4 | 3.1 | 2.7 | 2.3 | 1.9 | 1.5 | 1.0 | 0.5 | 0.0 | · | · | · | · | · | · | · | · | · | · | · |
| 200 | 3.8 | 3.6 | 3.3 | 3.0 | 2.6 | 2.2 | 1.8 | 1.4 | 1.0 | 0.5 | 0.0 | · | · | · | · | · | · | · | · | · | · |
| 210 | 4.0 | 3.7 | 3.5 | 3.2 | 2.9 | 2.5 | 2.2 | 1.8 | 1.4 | 0.9 | 0.5 | 0.0 | · | · | · | · | · | · | · | · | · |
| 220 | 4.1 | 3.9 | 3.6 | 3.4 | 3.1 | 2.8 | 2.4 | 2.1 | 1.7 | 1.3 | 0.9 | 0.5 | 0.0 | · | · | · | · | · | · | · | · |
| 230 | 4.2 | 4.0 | 3.8 | 3.5 | 3.3 | 3.0 | 2.7 | 2.4 | 2.0 | 1.7 | 1.3 | 0.9 | 0.5 | 0.0 | · | · | · | · | · | · | · |
| 240 | 4.3 | 4.1 | 3.9 | 3.6 | 3.4 | 3.2 | 2.9 | 2.6 | 2.3 | 2.0 | 1.6 | 1.3 | 0.9 | 0.4 | 0.0 | · | · | · | · | · | · |
| 250 | 4.3 | 4.2 | 4.0 | 3.8 | 3.6 | 3.3 | 3.1 | 2.8 | 2.5 | 2.2 | 1.9 | 1.6 | 1.2 | 0.8 | 0.4 | 0.0 | · | · | · | · | · |
| 260 | 4.4 | 4.2 | 4.1 | 3.9 | 3.7 | 3.5 | 3.2 | 3.0 | 2.7 | 2.5 | 2.2 | 1.9 | 1.5 | 1.2 | 0.8 | 0.4 | 0.0 | · | · | · | · |
| 270 | 4.5 | 4.3 | 4.1 | 4.0 | 3.8 | 3.6 | 3.4 | 3.2 | 2.9 | 2.7 | 2.4 | 2.1 | 1.8 | 1.5 | 1.1 | 0.8 | 0.4 | 0.0 | · | · | · |
| 280 | 4.5 | 4.4 | 4.2 | 4.1 | 3.9 | 3.7 | 3.5 | 3.3 | 3.1 | 2.9 | 2.6 | 2.3 | 2.0 | 1.7 | 1.4 | 1.1 | 0.7 | 0.4 | 0.0 | · | · |
| 290 | 4.5 | 4.4 | 4.3 | 4.1 | 4.0 | 3.8 | 3.6 | 3.4 | 3.2 | 3.0 | 2.8 | 2.5 | 2.2 | 2.0 | 1.7 | 1.4 | 1.0 | 0.7 | 0.4 | 0.0 | · |
| 300 | 4.6 | 4.5 | 4.3 | 4.2 | 4.1 | 3.9 | 3.7 | 3.5 | 3.4 | 3.2 | 3.0 | 2.7 | 2.4 | 2.2 | 1.9 | 1.6 | 1.3 | 1.0 | 0.7 | 0.3 | 0.0 |
Table 2 -- Low-side pressure P_low (bar): Dosatron return pressure
Add ~0.5 bar for the Dosatron inlet pressure.
| Qopen \ Qdel | 100 | 110 | 120 | 130 | 140 | 150 | 160 | 170 | 180 | 190 | 200 | 210 | 220 | 230 | 240 | 250 | 260 | 270 | 280 | 290 | 300 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 100 | 5.1 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 110 | 4.2 | 5.1 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 120 | 3.5 | 4.3 | 5.1 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 130 | 3.0 | 3.6 | 4.3 | 5.1 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 140 | 2.6 | 3.1 | 3.7 | 4.4 | 5.1 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 150 | 2.2 | 2.7 | 3.2 | 3.8 | 4.4 | 5.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 160 | 2.0 | 2.4 | 2.8 | 3.3 | 3.9 | 4.4 | 5.0 | · | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 170 | 1.7 | 2.1 | 2.5 | 2.9 | 3.4 | 3.9 | 4.5 | 5.0 | · | · | · | · | · | · | · | · | · | · | · | · | · |
| 180 | 1.5 | 1.9 | 2.2 | 2.6 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 | · | · | · | · | · | · | · | · | · | · | · | · |
| 190 | 1.4 | 1.7 | 2.0 | 2.3 | 2.7 | 3.1 | 3.6 | 4.0 | 4.5 | 5.0 | · | · | · | · | · | · | · | · | · | · | · |
| 200 | 1.2 | 1.5 | 1.8 | 2.1 | 2.4 | 2.8 | 3.2 | 3.6 | 4.1 | 4.5 | 5.0 | · | · | · | · | · | · | · | · | · | · |
| 210 | 1.1 | 1.4 | 1.6 | 1.9 | 2.2 | 2.5 | 2.9 | 3.3 | 3.6 | 4.1 | 4.5 | 5.0 | · | · | · | · | · | · | · | · | · |
| 220 | 1.0 | 1.2 | 1.5 | 1.7 | 2.0 | 2.3 | 2.6 | 2.9 | 3.3 | 3.7 | 4.1 | 4.5 | 4.9 | · | · | · | · | · | · | · | · |
| 230 | 0.9 | 1.1 | 1.3 | 1.6 | 1.8 | 2.1 | 2.4 | 2.7 | 3.0 | 3.3 | 3.7 | 4.1 | 4.5 | 4.9 | · | · | · | · | · | · | · |
| 240 | 0.8 | 1.0 | 1.2 | 1.4 | 1.6 | 1.9 | 2.2 | 2.4 | 2.7 | 3.0 | 3.4 | 3.7 | 4.1 | 4.4 | 4.8 | · | · | · | · | · | · |
| 250 | 0.8 | 0.9 | 1.1 | 1.3 | 1.5 | 1.7 | 2.0 | 2.2 | 2.5 | 2.8 | 3.1 | 3.4 | 3.7 | 4.1 | 4.4 | 4.8 | · | · | · | · | · |
| 260 | 0.7 | 0.9 | 1.0 | 1.2 | 1.4 | 1.6 | 1.8 | 2.0 | 2.3 | 2.5 | 2.8 | 3.1 | 3.4 | 3.7 | 4.1 | 4.4 | 4.8 | · | · | · | · |
| 270 | 0.6 | 0.8 | 0.9 | 1.1 | 1.3 | 1.5 | 1.7 | 1.9 | 2.1 | 2.3 | 2.6 | 2.9 | 3.1 | 3.4 | 3.7 | 4.1 | 4.4 | 4.7 | · | · | · |
| 280 | 0.6 | 0.7 | 0.9 | 1.0 | 1.2 | 1.3 | 1.5 | 1.7 | 1.9 | 2.2 | 2.4 | 2.6 | 2.9 | 3.2 | 3.4 | 3.7 | 4.0 | 4.4 | 4.7 | · | · |
| 290 | 0.6 | 0.7 | 0.8 | 0.9 | 1.1 | 1.2 | 1.4 | 1.6 | 1.8 | 2.0 | 2.2 | 2.4 | 2.7 | 2.9 | 3.2 | 3.5 | 3.7 | 4.0 | 4.3 | 4.6 | · |
| 300 | 0.5 | 0.6 | 0.7 | 0.9 | 1.0 | 1.2 | 1.3 | 1.5 | 1.7 | 1.8 | 2.0 | 2.3 | 2.5 | 2.7 | 3.0 | 3.2 | 3.5 | 3.7 | 4.0 | 4.3 | 4.6 |
How to use at the bench
- Wide open (bypass loop only, manual tap fully open), read the delivery flow -> Qopen.
- Throttle to your operating point, read the delivery flow -> Qdel.
- Look up the cell: DeltaP drives the Dosatron branch; P_low + 0.5 is the Dosatron inlet. Any DeltaP >= 0.5 confirms the boosterless design works.
Assumptions & caveats
- Pump head read from the 3" curve by eye (+-~0.1-0.2 bar); the shut-off checks against the stated 530 kPa, so the digitisation is anchored.
- High side taken at the delivery flow. If the high-pressure bypass raises total pump flow, the high side sits slightly lower per the (flat) curve, marginally reducing DeltaP -- negligible below the 400 L/min knee.
- Sprinkler K assumed constant (fixed nozzle set, no zone changes between the two readings).
- Elevation between tap points assumed small (< ~0.2 bar); add it in if the branch rises or drops more than ~2 m.