Table of Contents
An atv sprayer with a 6 m boom carries 12 tips at 0.5 m spacing. That boom must pass 12.0 L/min for 100 L/ha at 12 km/h. Each tip therefore needs 1.0 L/min. A 110-02 tip is rated 0.8 L/min at 3 bar. Fit it and the rig applies 80 L/ha, a 20 percent miss. Closing that gap with pressure needs 4.7 bar. That also moves the droplet class a full step finer.
A 3 point sprayer with a 12 m boom and 24 tips needs 24 L/min. A 400 L tank then empties in about 17 minutes. One worn tip passing 10 percent over rated flow lays a stripe. That stripe is 110 L/ha down a 0.5 m band on every pass. It stays invisible until the crop answers it.
This guide covers the flow method and the square root pressure law. It then works width, overlap, droplet class and the plumbing behind each rig class. PWM control, filtration and a clean water calibration close the list.
Four Names, One Machine
Buyers search this rig class under every name it has: atv sprayers, a four wheeler sprayer, a side by side sprayer, a utility vehicle boom sprayer, an enclosed utv sprayer with boom, and dealers list the whole family as sprayers for sale. The badge and the search phrase change; the flow arithmetic below does not.
The Snapshot
- 12.0 L/min is the boom flow for 100 L/ha at 12 km/h across 6 m, from Q = L/ha x width x speed / 600. At 0.5 m spacing that is 1.0 L/min per tip.
- 41 percent is the flow gain from doubling pressure, because Q follows the square root of P, and the droplet class moves one step finer with it.
- 1.43 m is the width of a 110 degree tip at a 0.5 m standoff, from width = 2 × standoff × tan(angle / 2). Spacing at 70 to 75 percent of that gives a 25 to 30 percent overlap.
- 10 percent is the flow error a worn tip adds before it looks worn, which on a 24 tip boom is a 10 percent chemical error across the block.
Why the Rig Class Sets the Nozzle
Boom width, tip count and pump margin change with the rig class. A colour that suits a 3 point sprayer at 12 m is often wrong for a UTV at 4 m. The ranges below are typical industry figures.
| Rig class | Boom width | Tank | Pump flow |
|---|---|---|---|
| atv sprayer or utv sprayer | 2 to 6 m | 60 to 200 L | 5 to 20 L/min |
| 3 point sprayer | 6 to 18 m | 300 to 800 L | 40 to 80 L/min |
| tow behind sprayer or pull behind sprayer | 8 to 24 m | 400 to 1200 L | 40 to 100 L/min |
| tractor sprayer or self-propelled boom sprayer | 18 to 36 m | 1500 to 4000 L | 150 to 400 L/min |
The width row sets flow demand. A 20 m boom at 120 L/ha and 16 km/h needs 64 L/min. A pump rated 60 L/min free flow falls short at the boom. A diaphragm pump loses 10 to 20 percent of its free flow at 4 bar.
Tip count sets error tolerance. One worn tip is a 25 percent error on a 4 tip atv sprayer boom. The same tip is about 4 percent on a 24 tip boom. That is why wide ag spray equipment splits the width into 3 to 6 m sections.
The Flow Method: Litres per Hectare to Nozzle Flow
Boom flow in litres per minute is rate times width times speed, divided by 600. The constant folds in 60 minutes per hour and 10,000 square metres per hectare.
Flow (L/min) = L/ha x width (m) x speed (km/h) / 600
For 100 L/ha, 6 m and 12 km/h the sum is 12.0 L/min. That figure is the whole boom, not one tip. Flow per tip uses the same law with spacing in place of width.
Flow per tip (L/min) = L/ha x spacing (m) x speed (km/h) / 600
At 0.5 m spacing, 100 L/ha and 12 km/h that is 1.0 L/min. Coverage = flow x 60 / area gives the same answer. At 12.0 L/min the boom passes 720 L/h. It covers 7.2 ha/h, so the rate is 100 L/ha.
Run the law backwards for a label rate. A pasture job at 150 L/ha from a 9 m boom at 10 km/h needs 22.5 L/min. At 18 tips that is 1.25 L/min per tip. A 110-03 blue at 1.2 L/min reaches that figure at 3.25 bar. A 110-025 lilac at 1.0 L/min would need 4.7 bar and lose a class.
Pressure and Flow: The Square Root Trim
Flow through any hydraulic tip follows Q = K x the square root of P. K folds the orifice area and the discharge coefficient into one constant. Divide rated flow by the square root of rated pressure. Every pressure then maps onto one flow.
| Pressure | Square root of P | 110-02 at K = 0.462 | 110-03 at K = 0.693 |
|---|---|---|---|
| 2.0 bar | 1.414 | 0.65 L/min | 0.98 L/min |
| 3.0 bar | 1.732 | 0.80 L/min | 1.20 L/min |
| 6.0 bar | 2.449 | 1.13 L/min | 1.70 L/min |
A 110-02 rated 0.8 L/min at 3 bar has K = 0.462. A 110-03 at 1.2 L/min has K = 0.693. Doubling pressure raises flow 41 percent, because the square root of 2 is 1.414. Halving pressure cuts flow 29 percent.
Pressure is a trim, not a sizing tool. A 0.5 bar move around 3 bar changes flow about 8 percent. A 25 percent shortfall needs 1.56 times the pressure. That takes a 3 bar tip past 4.5 bar and fines the spectrum. Changing the tip is cheaper. Flow scales with the square of the bore. A 10 percent oversize orifice passes 21 percent more liquid. Doubling pressure also raises hydraulic power 2.83 times.
Pattern Width from Standoff and Angle
Pattern width at the target follows one geometric law. It is twice the standoff times the tangent of half the spray angle.
width = 2 × standoff × tan(angle / 2)
A 110 degree tip has a half angle of 55 degrees. Its tangent is 1.428, so the pattern is 2.86 times the standoff. A 120 degree tip has a tangent of 1.732. Its pattern is 3.46 times the standoff.
| Standoff | 80 degree | 110 degree | 120 degree |
|---|---|---|---|
| 0.5 m | 0.84 m | 1.43 m | 1.73 m |
| 0.75 m | 1.26 m | 2.14 m | 2.60 m |
| 1.0 m | 1.68 m | 2.86 m | 3.46 m |
Gravity and drag pull the outer sheet down. A real footprint lands 5 to 10 percent narrower at a 0.5 m standoff. Confirm the working width with catch cans.
Standoff is a rate variable. Doubling it halves the deposit per unit area at fixed flow and speed. A 0.1 m error on a 110 degree tip moves the width 0.29 m. That is about 20 percent of the pattern, so it belongs on the calibration sheet.
Overlap and Nozzle Spacing
Adjacent patterns have to sum to a flat deposit. A fan carries less at its edge than at its centre. Tips are therefore spaced shorter than the pattern width.
Spacing (m) = width (m) x (1 minus overlap fraction)
A 25 to 30 percent overlap means spacing at 70 to 75 percent of the width. A 110 degree tip at a 0.5 m standoff throws 1.43 m. Spacing then lands between 1.00 m and 1.07 m.
| Spacing | Overlap of width | Tips on 6 m | Flow per tip for 100 L/ha at 12 km/h |
|---|---|---|---|
| 1.00 m | 30 percent | 6 | 2.00 L/min |
| 0.75 m | 48 percent | 8 | 1.50 L/min |
| 0.50 m | 65 percent | 12 | 1.00 L/min |
| 0.35 m | 76 percent | 17 | 0.70 L/min |
The two right hand columns trade against each other. A wide spacing needs a bigger tip per position. A tight spacing needs more tips but lets every tip run mid band. Broadcast booms commonly run 50 to 65 percent overlap at 0.5 m. That is why a boom flattens rate errors well.
Below 25 percent overlap the taper shows as a stripe. The deficit runs 15 to 25 percent in a narrow band. It repeats at the same spacing on every pass. A centre-fed boom also needs an inner overlap check. The patterns under the machine can double up at roughly double rate.
Droplet Class and the ISO Colour Codes
Droplet size is set by the tip, the pressure and the liquid. Volume median diameter splits the sprayed volume in half. The ASABE S572.1 bands below are the reference when a label names a class.
| ASABE S572.1 class | VMD (microns) | Field behaviour |
|---|---|---|
| Very fine | below 145 | travels far in light wind |
| Fine | 145 to 225 | high drift risk |
| Medium | 226 to 325 | moderate drift |
| Coarse | 326 to 460 | lower drift, contact products |
| Very coarse | 461 to 650 | low drift, residual work |
| Extremely coarse | above 650 | minimal drift, soil and stubble |
ISO 10625 colours the tip body by flow at a reference pressure. The values below are the typical low flow series at 3 bar.
| ISO code | Colour | Flow at 3 bar |
|---|---|---|
| 015 | green | 0.6 L/min |
| 02 | yellow | 0.8 L/min |
| 025 | lilac | 1.0 L/min |
| 03 | blue | 1.2 L/min |
| 04 | red | 1.6 L/min |
Read the two named cases side by side. A 110-02 at 3 bar is a yellow body passing 0.8 L/min. A 110-03 at 3 bar is a blue body passing 1.2 L/min. That is 50 percent more liquid from one position. Mixing the two on one boom is a 50 percent rate step between sections.
Colour does not carry the class. A yellow 02 runs medium to coarse in a standard flat fan. The same colour runs very coarse in an air-induction body. Pressure is the class trim. A tip run 1 bar above rated loses about one class step. A weed killer sprayer near a boundary should hold very coarse.
ATV and UTV Builds: Narrow Boom, Tight Plumbing
An atv sprayer or utv sprayer is a low width, low volume machine. Booms run 2 to 6 m and tanks 60 to 200 L. The pump is a 12 V diaphragm unit in the 5 to 20 L/min band. It runs at up to 6 bar and draws about 96 W. A UTV charging system may deliver 400 to 650 W in total.
Most owners call this machine an atv boom sprayer or a utv boom sprayer, and both names describe the same plumbing constraint. The pump is the part that fails the arithmetic, not the tip: the amp draw of a 12 volt sprayer pump against the charging margin is the first line on the sizing sheet, worked in sprayer pump selection.
On a 3 m boom at 12 km/h the covered width is 3.6 ha/h. At 100 L/ha that is 360 L/h, or 6.0 L/min. A 100 L tank then gives 1 ha per fill. That is 16.7 minutes of spraying.
Plumbing here is small and must be tight. A bypass regulator holds boom pressure. An anti-drip check valve sits behind each tip. A line strainer and tip screen protect the 1 mm orifice class. A full bar of gauge error on a 0 to 6 bar dial is 15 percent of flow.
Three Point and Tow Behind Rigs: Wide Boom, Big Pump
A 3 point sprayer and a tow behind sprayer move to a different scale. A pull behind sprayer sits in the same class. Booms run 6 to 24 m and tanks 300 to 1200 L. Pumps deliver 40 to 100 L/min from PTO, hydraulic or 12 V drive.
Flow demand rises linearly with width. A 12 m boom at 120 L/ha and 16 km/h needs 38.4 L/min. Size the pump at the boom figure plus 15 to 20 percent.
The regulator behaves differently at this scale. A bypass valve returns the flow the open sections do not use. With half the boom shut off, up to 19 L/min recirculates. That flow runs through the tank, and pump energy warms the liquid.
Machine attitude matters on a tow behind sprayer. Ride height changes 0.05 to 0.10 m between a full and an empty tank. On a 110 degree tip that moves the pattern width 0.29 m. The rate moves about 10 percent with it. Set the standoff with the tank half full. Level the frame within 2 degrees, because a hitch pitches over a rise.
Filtration, Anti-Drip and Wetted Materials
Filtration follows the orifice. Use a screen opening near one quarter to one third of the orifice diameter.
Orifice area = flow / (discharge coefficient x square root of 2P / density)
A 110-02 passing 0.8 L/min at 3 bar moves 1.33 x 10 to the minus 5 cubic metres per second. With a discharge coefficient of 0.9 the orifice is 0.88 mm. A quarter to a third of that is 0.22 to 0.29 mm. That is a 50 to 60 mesh screen.
Anti-drip check valves stop the line draining at the end of a pass. Cracking pressures run 0.3 to 1.0 bar. A tip run at 2 bar behind a 1.5 bar valve will weep. Twelve tips losing one 0.5 mL drop per second release 0.36 L in a minute.
Wetted material sets service life. Hardened stainless steel holds within about 5 percent of rated flow. That covers several hundred hours against abrasive powders. Ceramic inserts last longest in slurries but crack under impact. Acetal (POM) bodies suit ATV and UTV booms on cost. They wear faster against abrasives than steel or ceramic.
PWM Control on Narrow Nozzle Arrays
Pulse width modulation switches each tip on and off many times a second. Average flow is rated flow at working pressure times the duty cycle. Speed changes are absorbed by duty, so pressure stays fixed. A 10 Hz system has a 100 ms cycle. A 30 percent duty is a 30 ms pulse.
The turn down ratio defines the map. Six tips passing 2.0 L/min each give 12 L/min at full duty. That is 100 L/ha on a 6 m boom at 12 km/h. At 20 percent duty the boom passes 2.4 L/min. That is 2.4 x 600 / (6 x 12), or 20 L/ha.
Solenoid latency is the first distortion risk. A 5 to 10 ms lag is 5 to 10 percent of a 100 ms cycle. True duty therefore runs below commanded duty at every setting. A 0.8 L/min tip has little margin against a 0.05 L/min error.
Partial lift at the pulse edges is the second. The first and last milliseconds of a pulse pass liquid at partial lift. Both ends of each pulse are coarser than the mid pulse. At short duties the average spectrum drifts one class coarser.
Array phasing is the third. Unsynced tips fire out of step somewhere in the cycle. At 10 Hz that becomes a moving stripe, worst at low duty. Frequency limits close the list. Below about 10 Hz the pulses band across the ground. Above about 30 to 40 Hz many coils cannot complete a full stroke.
Calibration on Clean Water
Calibration turns a table of numbers into a working rig.
Time the speed over a marked 50 m course. Use the gear and throttle you will actually run. At 12 km/h the run takes 15 seconds. Divide 180 by the seconds to get km/h. A wheel sensor on a UTV reads 5 to 10 percent high in soft soil. Trust the stopwatch over the screen.
Solve the flow law for the flow the boom must deliver. For 100 L/ha at 12 km/h across 6 m that is 12.0 L/min. Catch every tip for 60 seconds at working pressure. A tip within 5 percent of rated flow passes. One more than 10 percent above rated is worn.
Check the gauge against a reference once a season. A gauge reading 1 bar low sets true pressure 1 bar high. At 3 bar that is 15 percent extra flow across the boom. Reset the tank mix from the area the tank covers. A 400 L tank at 100 L/ha covers 4 ha.
Section Control, Row Spacing and Part Width Arithmetic
A 12 m boom split into four 3 m sections can shut one section. That saves 25 percent of flow over that distance. Manual marking doubles about 3 percent of the area on a rectangular block. Point rows and waterways push that to 10 percent or more. Automatic section control cuts the overlap to about 1 percent.
Row crop changes the target area itself. A 0.25 m band on 0.75 m rows covers 33 percent of the field. An 8 ha block is then sprayed across 2.67 ha. The flow law works on the band width, not the row spacing.
A narrow ATV boom usually has 1 to 2 m sections or none. On this class the useful automation is rate control by duty cycle. On a 12 m ag sprayers boom at 38.4 L/min, closing three sections leaves 9.6 L/min. About 29 L/min then bypasses the regulator as heat.
The Failure Modes That Cost Money
A worn tip is the most expensive and least visible fault. Wear opens the orifice, so flow rises without changing the colour. A 110-02 worn 10 percent passes 0.88 L/min instead of 0.80 L/min. On a 20 ha block at 100 L/ha the boom uses 2,200 L instead of 2,000 L.
A blocked tip is the second. One blocked position on a 12 tip boom removes about 0.5 m of coverage. That is 8 percent of the swath, repeated at the same spacing every pass.
Wrong standoff is the third. A boom riding 0.2 m too high widens the pattern 40 percent. The rate drops about 29 percent across the whole width.
Over-pressure to fix a rate gap is the fourth. A tip taken from 3 bar to 6 bar adds 41 percent flow. The class moves a step finer with it.
Speed drift is the fifth. An operator running 14 km/h instead of 12 applies 86 L/ha. A weeping check valve is the sixth, and it leaves a band at every headland. Mismatched tips are the seventh. One brand can sit 5 percent away from another at the same nominal size.
Frequently Asked Questions
How do I pick a tip size for an ATV sprayer at 100 L/ha?
Work the flow law with spacing in place of width. At 0.5 m spacing and 12 km/h, 100 x 0.5 x 12 / 600 gives 1.0 L/min per tip. A 110-025 lilac delivers that at 3 bar. A 110-02 yellow would need 4.7 bar.
How much does a worn nozzle change my rate?
A 10 percent flow gain is a 10 percent rate gain at the same speed. That is 200 extra litres of solution on a 20 ha block at 100 L/ha. Replace anything more than 10 percent above rated flow.
Does PWM control change droplet size on small tips?
It changes at the edges of each pulse, and the effect grows as duty falls. A 30 percent duty on a 10 Hz system is a 30 ms pulse. Partial lift at each end shifts the average spectrum one class coarser.
Is a boom sprayer easier to set up than a tow behind?
More forgiving, not easier. A 24 tip boom averages a 10 percent tip error down to about 4 percent. A 4 tip ATV boom carries that error on half its width.
The Bottom Line
The rig class sets the tip count and the overlap. The flow law sets the colour. Work the arithmetic before the first fill. 100 L/ha at 12 km/h across 6 m is 12.0 L/min. At 0.5 m spacing that is 1.0 L/min per tip. Hold pressure inside the rated band. Keep standoff within 0.1 m of the setting.
Size a wide 3 point or pull behind sprayer pump at the boom flow plus 15 to 20 percent. On an atv sprayer or utv sprayer, spend the budget on anti-drip valves first. A stable boom beats extra width.
Browse the agricultural nozzle range for flat fan and air-induction tips. Send your boom width, spacing, label rate and working speed to the application team. The agricultural nozzle types guide covers flat fan, cone and air-induction behaviour. The herbicide nozzle selection guide covers class choice near a boundary. The agricultural spraying application page covers the machines.
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Written by
Ray ChanIndustrial spray nozzle specialist. I size tank cleaning, atomizing, flat-fan and spiral nozzles against real duty conditions, flow, pressure, fluid and target, rather than catalogue numbers. Every guide here comes from actual sizing work.