How Do I Select a Spray Nozzle? The Duty-Led Spray Nozzle Selection Guide

A spray nozzle selection guide exists to stop a specifier locking a part number before the duty is fixed. Get the family wrong and no pressure tweak recovers the job. A hollow cone where a flat fan was needed leaves wet and dry stripes. A solid stream where atomisation was needed soaks one spot and misses the rest. Five inputs decide the outcome: pattern, flow, pressure, droplet class and material, with the connection as the sixth.

This page is the map of that territory, organised by duty and by nozzle family. Where the step-by-step route suits you better, work through the seven-stage frame in the how to choose a spray nozzle page. Where you want the whole landscape in one read, stay here.

The Snapshot

• 30 to 50 percent overlap between adjacent flat fans is the usual target for an even band. Below about 20 percent the stripes start to show.
• 41 percent is the flow gain from doubling pressure, because flow follows the square root of pressure. Spray angle does not move with it.
• 10 percent above the stamped flow at rated pressure is the common replacement trigger. A bore worn 10 percent oversize passes about 21 percent more flow.
• 150 micron VMD marks the fine to medium boundary, with medium running 150 to 300 and coarse running 300 to 500.

What a Nozzle Specification Has to Fix

A nozzle is not one choice but six locked together, and moving any one of them shifts the others. Fix the pattern first, because pattern decides coverage geometry. Then flow at a stated pressure, then the pressure itself, then droplet class, then material, and finally the connection.

Pattern fixes coverage shape. A flat fan lands as a band roughly 1 to 2 units wide per unit of standoff. A full cone covers a filled circle, and a hollow cone covers its rim.

Flow and pressure are one variable, not two. Published flow is quoted at a stated pressure, usually 3 bar or 40 psi for general duty. Move to another pressure and the square root law applies.

Droplet class fixes how the liquid behaves after it leaves the orifice. A coarse spray near 400 micron VMD lands and stays. A fine spray near 100 micron VMD drifts before it arrives.

Material fixes life rather than day-one performance. Ceramic inserts outlast stainless in abrasive duty by a factor of 5 to 10 in published practice.

Connection fixes compatibility. BSP and NPT threads look alike and are not interchangeable, which is worth confirming before a purchase order rather than after. The standards are separated in the nozzle thread sizes BSP and NPT reference.

Start From the Duty, Not the Catalogue

The fastest route into any nozzle selection guide is to name the duty in operational words, then read back the family. Duty decides droplet class, droplet class narrows pressure, and pressure plus flow fix the orifice. Start from what the liquid must do on contact.

Cleaning and rinsing want impact plus coverage. A full cone or a flat fan at 3 to 10 bar delivers medium to coarse droplets with the mass to break a surface film. Vessel work needs reach and rotation instead.

Cooling wants a controlled film and even coverage. Flat fans and full cones at 2 to 5 bar hold a uniform band on a moving surface, with higher overlap at the edges of the work.

Coating and lubricating want a thin, even deposit. Air atomising at 0.5 to 2 bar liquid pressure and a few bar of air gives the finest control, with droplet size set by air pressure.

Dust suppression wants the finest droplets that still reach the source. Misting at 3 to 20 bar makes droplets from about 20 to 100 micron VMD.

Mixing and eductor duty wants momentum transfer, not coverage. A motive jet at 2 to 5 bar entrains a secondary fluid, and the ratio of motive flow to suction flow decides the performance.

Field spraying wants even area coverage with controlled drift. Boom sections run flat fans at 1.5 to 4 bar, often with air inclusion to keep medium droplets on target.

Blow-off wants a high velocity air sheet, not a liquid spray. Air nozzles at 2 to 6 bar convert compressed air into a flat jet.

The Six Questions That Resolve Most Specifications

Most specifications collapse to six questions answered in order. Each one narrows the field, and a later question cannot undo an error in an earlier one.

Question one asks what the spray must do on contact: coat, cool, clean, atomise, suppress or mix. The answer names the family.

Question two asks what flow the duty needs at operating pressure, in litres per minute or gallons per minute. The answer fixes the orifice size, and the method sits in spray nozzle flow rate calculation.

Question three asks what pressure the header can actually hold at the nozzle. Pump discharge is not nozzle pressure, and the gap is often 0.5 to 1.5 bar.

Question four asks what droplet class the duty tolerates, which decides whether a fine, medium or coarse nozzle is even eligible.

Question five asks what fluid, temperature and abrasion decide material, since corrosion, wear and food contact each remove options.

Question six asks what connection and installed geometry exist, because thread standard, standoff and manifold spacing close the choice.

Order	Question	What it fixes	Typical values	Point of reference
1	What must the spray do?	Pattern family	flat fan, full cone, hollow cone, spiral	pattern families below
2	What flow is needed?	Orifice size	0.5 to 20 L/min per nozzle	flow section below
3	What pressure is at the nozzle?	Orifice and band	2 to 20 bar by duty	pump versus nozzle
4	What droplet class is allowed?	Orifice and pressure	20 to 500 micron VMD	droplet class section
5	What material suits the fluid?	Wetted parts	brass, 316 stainless, ceramic	material section
6	What connection exists?	Fits and seals	1/4, 3/8, 1/2 inch BSP or NPT	connection section

Pattern Families and What Each One Buys You

A flat fan lands as a tapered band. Coverage is linear, so centre spacing is the design variable and adjacent fans should overlap 30 to 50 percent. It suits cleaning, cooling and coating of flat surfaces, as detailed in the flat fan nozzles overview.

A full cone fills the whole circle with a spread of droplet sizes. Coverage is area-based, so fewer nozzles cover a given footprint, which suits washing, quenching and dust knock-down near the source.

A hollow cone concentrates liquid at the rim. That ring gives finer droplets and a lower flow for the same angle, which suits evaporative cooling and scrubbing. The comparison is set out in full cone vs hollow cone nozzles.

A spiral nozzle is a one-piece cone with an open bore and no internal vanes. It passes slurries and high solids without clogging, at a low unit cost of coverage. See the spiral nozzles overview.

A solid stream gives the highest impact per litre and the least coverage, so it suits descaling, cutting and lance work.

Air atomising separates liquid and air. Droplet size is set by air pressure and the pattern by the air cap, which suits coating where liquid pressure alone cannot reach the class needed. See the air atomizing nozzles overview.

A misting nozzle makes a fog from about 20 to 100 micron VMD using high pressure or a small orifice.

Family	Pattern shape	Coverage character	Typical overlap	Droplet tendency
Flat fan	tapered band	linear, edge-tapered	30 to 50 percent	medium
Full cone	filled circle	area, uniform	10 to 20 percent	medium to coarse
Hollow cone	ring at the rim	area, ring-weighted	20 to 30 percent	fine to medium
Spiral	cone, open bore	area, high flow	20 to 30 percent	coarse
Solid stream	narrow jet	point impact	not applicable	coarse
Air atomising	tunable, wide	linear or round	25 to 40 percent	fine
Misting	fog	volume	30 to 50 percent	very fine

Flow, Pressure and the Square Root Law

Flow through a nozzle follows Q = K times the square root of P, where K is the nozzle constant and P the pressure drop across the orifice. Doubling pressure raises flow by about 41 percent, from a factor of 1.414.

Work the arithmetic. A nozzle rated at 2.0 L/min at 3 bar has K equal to 2.0 divided by the square root of 3, which is 1.155. At 6 bar the same nozzle passes 1.155 times the square root of 6, or 2.83 L/min, which is 41 percent above rated.

Pressure	Square root factor	Flow for K = 1.155	Position against rated band
1.5 bar	1.22	1.41 L/min	about 29 percent below rated
3.0 bar	1.73	2.00 L/min	rated point
6.0 bar	2.45	2.83 L/min	about 41 percent above rated
12.0 bar	3.46	4.00 L/min	about 100 percent above rated

Pressure changes flow, not spray angle. A 110 degree fan stays near 110 degrees across its useful band, and a 10 percent pressure change shifts the angle by only a couple of degrees.

That is why you size the orifice before the pump. Fix the flow the duty needs at the pressure the header can hold, solve for K, then choose the nozzle. A pump chosen first forces pressure into a range the nozzle was never matched to, which is the most common sizing failure in the field. The method is in water spray nozzle design calculation.

Droplet size also falls as pressure rises, so a nozzle run far above its band atomises finer and drifts further. Doubling pressure costs about four times the pumping power for 41 percent more flow, so pressure is the expensive variable.

Choosing a Droplet Class Before a Nozzle

Droplet class is a duty decision, not a preference, and finer is not better by default. Published practice splits sprays into fine below about 150 micron VMD, medium from 150 to 300, and coarse from 300 to 500. VMD is the volume median diameter, the drop size that splits the sprayed volume in half.

Fine sprays under 150 micron cover area well and evaporate fast, which suits evaporative cooling, humidification and thin coating. They also drift, and wind above about 3 m/s carries a 100 micron droplet well off target.

Medium sprays from 150 to 300 micron balance coverage and throw, suiting general cleaning, washing and dust suppression at moderate range.

Coarse sprays from 300 to 500 micron carry momentum and resist drift, which suits impact cleaning, descaling and long-throw coverage.

The same nozzle makes different classes at different pressures. A hollow cone that runs medium at 3 bar may run fine at 10 bar, which raises drift risk without any change to the part number. The relationships are worked in droplet size calculation.

Drift and evaporation are the consequences to weigh. A 100 micron droplet settles at roughly 0.3 m/s, so it will not reach a target 5 m below, while a 400 micron droplet settles near 1.5 m/s and lands. Where the target is close and the air still, finer wins.

Material Selection: Metal, Plastic or Ceramic

Material sets life and compatibility rather than day-one performance, on corrosion class, abrasion class, temperature ceiling and wear rate. Performance is near identical across materials on the first day, and the difference appears at 500 to 2000 hours.

Brass resists water and mild fluids and costs little. Its temperature ceiling sits near 120 C, and it corrodes quickly in acids and ammonia.

316 stainless steel handles most process fluids, weak acids and alkalis, and temperatures to about 400 C. It is the default for general industrial duty.

Ceramic inserts resist abrasion far better than metals. Published practice puts their wear life at 5 to 10 times that of hardened stainless in slurry duty, but they are brittle, so a metal body carries the thread.

Plastics such as PVDF and polypropylene resist strong acids and avoid metal contamination. Their temperature ceiling is lower, often 80 to 100 C, and they wear faster under abrasion.

Wear shows up as flow, not as a visible defect. A bore worn 10 percent oversize passes about 21 percent more flow, because flow scales with the square of the diameter. The replacement rule is a measured 10 percent rise above the stamped rating at rated pressure, as set out in nozzle wear silent over application.

Connection, Thread and Installed Geometry

A nozzle that behaved on the bench can behave differently on the header, because installed geometry sets the effective standoff. Three variables matter: thread standard, standoff and manifold spacing.

BSP and NPT threads both appear in 1/4, 3/8 and 1/2 inch sizes and are not interchangeable. The thread angle is 55 degrees for BSP and 60 degrees for NPT, and the pitch differs as well. A 1/4 BSP male will start a 1/4 NPT female and then leak under pressure.

Standoff sets the width. Spray width equals two times the standoff times the tangent of half the spray angle. At a 30 cm standoff, a 110 degree fan is about 86 cm wide, while a 65 degree fan is about 38 cm wide. The measurement rules are in the nozzle spray angle guide.

Header spacing follows from width and overlap. If the 110 degree fan is 86 cm wide and you want 40 percent overlap, centre spacing is about 52 cm.

Manifold layout then fixes nozzle count, total flow and header pressure drop. A dozen nozzles on a long header can lose 0.5 to 1.5 bar from the first position to the last, so the far nozzles deliver less than the spec sheet claims. Size the header at the worst-case pressure.

A Comparison Matrix: Duty Against Nozzle Family

One table maps duty to family, droplet class and a typical pressure band. The bands are typical published ranges, and they shift with flow, orifice and fluid.

Duty	Preferred family	Droplet class	Typical pressure band	Read next
Surface cleaning and rinsing	flat fan or full cone	medium to coarse	3 to 10 bar	flat fan overview
Vessel and tank cleaning	rotating cone or spiral	medium to coarse	3 to 8 bar	tank cleaning guide
Cooling and quenching	flat fan or full cone	medium	2 to 5 bar	full cone versus hollow cone
Thin film coating	air atomising	fine	0.5 to 2 bar liquid	air atomising guide
Dust suppression	misting or full cone	fine to medium	3 to 20 bar	misting selection
Humidification	misting or hollow cone	fine	5 to 20 bar	droplet size guide
Mixing and eductor duty	eductor with motive jet	coarse stream	2 to 5 bar	eductor guide
Burner and combustion	oil burner	fine	7 to 20 bar	burner nozzle guide
Crop and boom spraying	flat fan, air inclusion	medium to coarse	1.5 to 4 bar	agricultural guide
Slurry and high solids	spiral	coarse	1 to 4 bar	spiral overview
Paper machine showers	low-flow flat fan	coarse	3 to 20 bar	paper shower guide
Area irrigation	sprinkler	coarse	1 to 4 bar	sprinkler guide

The Four Numbers to Put on a Purchase Spec

A purchase spec that carries four numbers and a filtration grade gets the right part, while a spec that says “1/4 nozzle, stainless” does not. The four are flow at a stated pressure, pattern and angle at a stated standoff, material, and connection, with filtration as the fifth line.

Number one is flow in L/min at a stated pressure, for example 2.0 L/min at 3 bar.

Number two is pattern and angle at a stated standoff, for example a 110 degree flat fan measured at 30 cm, because the angle alone does not fix coverage.

Number three is material of wetted parts, for example 316 stainless with a ceramic insert wherever abrasion applies.

Number four is connection, for example 1/4 BSP male, with both the standard and the size in full.

Number five is filtration grade, for example a 100 micron inline strainer ahead of a 1.2 mm orifice. The rule of thumb is a filter opening about one quarter to one third of the orifice diameter.

Filtration is the omission that costs most at commissioning. A 1.0 mm orifice needs protection from anything over about 250 to 300 micron, and a coarse strainer lets a 1.5 mm chip through to distort the fan.

Sizing Mistakes That Cost the Most

The costly errors repeat across industries, and each one carries a number.

Oversizing to leave headroom lowers pressure, which lowers flow and impact. A nozzle run at half its rated pressure delivers about 71 percent of rated flow, not 100 percent.

Sizing on pump discharge pressure ignores losses between pump and nozzle. A pump at 5.0 bar with 1.0 bar lost in line and fittings leaves 4.0 bar at the nozzle.

Ignoring wear runs the line against stated performance. At 10 percent oversize bore the flow is about 21 percent high, which shifts coverage, over-applies chemical and changes the droplet class.

Choosing the wrong thread prevents a correct fit and invites a leak, since BSP and NPT differ in both angle and pitch.

Skipping filtration lets debris set the pattern. A partly blocked orifice drops flow on one side and shifts the fan, so one nozzle starves while its neighbour over-delivers.

Reading the rating at the wrong base pressure is a related trap. A figure of 2.0 L/min at 3 bar is about 3.06 L/min at 7 bar, not 2.0 L/min.

A Short Commissioning Checklist

Commissioning is a measurement job, and five readings catch nearly every installation error.

Measure flow at each nozzle position against the rated figure at header pressure. A reading 10 percent high or low flags wear or a wrong part.

Check pattern shape at the real standoff, because a distorted fan points to debris, damage or a wrong cap.

Read the overlap on the work. Adjacent flat fans should show a 30 to 50 percent overlap band with no dry stripe between them.

Check the differential across the inline filter. A rising differential means the element is loading, and a filter close to bypass will pass debris that blocks orifices.

Read the pressure at the header, at the furthest position as well as the nearest, because a spread above about 1.0 bar means the far nozzles under-deliver.

Where to Go Next

This page is the hub. The cluster guides hold the depth, and the product ranges hold the hardware.

For cleaning and vessel work, read the tank cleaning nozzles overview. For fog and evaporative duty, read misting nozzle selection. For momentum and suction duty, read the eductor selection guide. For field and boom work, read the agricultural nozzles overview.

For hardware, browse the spiral range where slurries and high solids are involved.

Frequently Asked Questions

How do I choose between a flat fan and a full cone nozzle? A flat fan covers a linear band and needs 30 to 50 percent overlap between neighbours. A full cone covers a filled circle and needs less overlap, often 10 to 20 percent. Choose the fan for moving webs, belts and rolls, and the cone for open areas and vessel volumes.

Does raising pressure increase the spray angle? No. Pressure changes flow, not geometry. A 110 degree fan stays near 110 degrees across its useful band. Doubling pressure raises flow by about 41 percent and leaves the pattern alone.

What droplet size do I need for dust suppression? Aim for the finest class that still reaches the source, typically 20 to 100 micron VMD from a misting nozzle at 3 to 20 bar. Droplets under about 100 micron drift far in wind above 3 m/s, while coarser droplets from a full cone reach further but wet the material.

How often should I replace a worn nozzle? Replace when measured flow at rated pressure exceeds the stamped figure by about 10 percent. A bore worn 10 percent oversize passes about 21 percent more flow, because flow scales with the square of the diameter.

Can I swap a BSP nozzle for an NPT nozzle? Not directly. BSP and NPT threads differ in thread angle, at 55 and 60 degrees, and in pitch. A 1/4 BSP male will start a 1/4 NPT female and then leak under pressure, so confirm both standard and size before ordering.

Specify the Duty First

Start every nozzle decision with the duty, then fix flow at pressure, droplet class, material and connection in that order.

Send the duty, the flow at its stated pressure and the connection to our team through the contact page, or browse the flat fan range.