Spray Guns and Lances

A spray gun is the interface between a pressurised line and a human hand. Unlike a fixed nozzle, it has a trigger or valve the operator controls, which means the selection problem is as much about ergonomics and inlet as about the spray pattern. The lance is the extension that puts the pattern where the hand cannot reach.

This page covers washdown guns, air-assisted guns and agricultural boom guns, the hand-held end of industrial cleaning and crop spraying, and walks through the four model classes in the reference table above the way a buyer actually narrows the range down: flow first, then pattern, then the inlet that has to match the hose already on the wall.

Flow, Pattern and Inlet

Flow is set by the gun’s internal orifice and the supply pressure, and a wash gun can pull a lot of volume at line pressure, relevant wherever water or chemical is metered or shared. The flow figures in the reference table are quoted at 3 bar. Flow through a fixed orifice rises with the square root of pressure, so doubling pressure raises flow only about 40 percent; if the pattern sags, the usual cause is supply, not pressure.

Pattern follows the fitted tip: flat fan for even wash or boom coverage, jet or cone for targeted work. The gun is the valve; the tip is the nozzle, and the two are selected together. A gun is never bought on its body alone, the tip decides what comes out of it.

Inlet: BSP thread size and type, must match the supply hose. A mismatch is a leak or a poor fit, not a spray problem, and it is the most common reason a new gun never makes it into service.

Range Walkthrough: What Each Model Is For

SG-WASH: wash gun. The workhorse for washdown duty. 3–20 L/min at 3 bar through a flat or jet tip, with a 1/2“ BSP inlet and PP or stainless construction. This is the widest flow band in the range because washdown is a volume job: rinse equipment, floors and vehicles, shift light residue, flush a line before changeover. If the duty reads as “spray a lot of water at something”, this is the starting point, flat tip for an even band over surfaces, jet tip when the water has to reach into frames and corners.

SG-AIR: air-assisted gun. A different class of tool: 0.5–5 L/min at 3 bar, cone pattern, 1/4“ BSP, aluminium or PP body. Compressed air shears the liquid into a fine, controlled cone for coating, dosing and finish work where raw volume would flood the surface. The flow looks small next to the wash gun, that is the point. Air-assisted atomisation produces fine droplets in roughly the 10–60 µm band at flows a pressure tip cannot control, which is what makes it the choice for finishes and for chemical applied in measured doses.

SG-BOOM: boom gun. The hand-held end of agricultural spraying. 5–25 L/min at 3 bar through a flat-fan tip, 3/4“ BSP inlet, stainless and nylon for field service. Built to push chemical across a row or a field edge in an even band, not a puddle. The flat fan is what earns its place: uniform coverage across the whole pass is exactly what herbicide and insecticide work demand, and the wider inlet keeps pressure loss low on long hose runs to the sprayer.

SG-LANCE: extension lance. A rigid extension rather than a standalone sprayer: flow follows the gun it is fitted to, 4–20 L/min across the range, with a 1/2“ BSP inlet and stainless or PP construction. It puts the pattern into a vat, over a hedge or down a pipe without the operator standing in the spray. The longer the lance, the more pattern steadiness depends on supply pressure and a well-matched tip at the far end.

Application Matrix

Industry	Typical duty	Recommended model	Why
Industrial cleaning	Equipment and floor washdown	SG-WASH	High flow at line pressure, flat / jet pattern
Food & beverage	Sanitiser application and line rinsing	SG-WASH with wide flat tip	Even wet, low overspray, PP / SS chemical service
Vehicle & fleet	Degrease and rinse-down	SG-WASH (jet tip)	Volume shifts detergent, jet reaches into frames
Coating	Fine finish and touch-up	SG-AIR	Air atomisation, fine cone, low overspray
Chemical dosing	Metered low-flow application	SG-AIR	0.5–5 L/min controlled cone, dose not flood
Agriculture	Row-crop herbicide and insecticide	SG-BOOM	Flat-fan band, even coverage across the pass
Agriculture	Field edges, trees, awkward rows	SG-LANCE + boom tip	Reach without standing in the spray
Tank & vessel	Interior washing through an opening	SG-LANCE + wash tip	Puts the pattern where the hand cannot go

Three-Step Selection: Flow → Pattern → Inlet

If the checklist below feels heavy, the decision collapses to three questions in order:

1. How much flow? Match the duty to the model’s flow band. Washdown is a volume job: SG-WASH at 3–20 L/min. Coating and dosing are low-flow precision jobs: SG-AIR at 0.5–5 L/min. Boom work sits between: SG-BOOM at 5–25 L/min. Then confirm the supply can deliver it: check flow at the gun connection, not at the pump, because long hose runs sag under load and the pattern follows.
2. What pattern? Flat fan for even coverage over a surface or a row, jet for targeted washdown, cone for air-assisted finish and dosing. The gun is the valve and the tip sets the pattern, changing the tip changes what comes out of the same body.
3. What inlet? Match the BSP thread to the supply hose: 1/4“ for the air gun, 1/2“ for wash guns and lances, 3/4“ for the boom gun. Fit is decided here, a mismatch leaks or fits poorly regardless of spray quality.

Reference Specifications

Flow quoted at 3 bar; air-assisted guns are a low-flow class by design. Inlet thread must match the supply. The figures are compiled from public industry sources as a sizing starting point, not as a datasheet.

How to Select a Spray Gun or Lance

Work through these in order and the choice usually narrows to one or two options.

• Duty: washdown, crop spraying or targeted application sets the gun type.
• Flow versus supply: confirm the line can deliver the gun’s flow at pressure without sagging; check at the connection, not at the pump.
• Pattern via the tip: pick the flat / jet / cone tip for the job; the gun is the valve.
• Inlet thread: match BSP size and type to the hose; fit is decided here.
• Reach: add a lance where the hand cannot go; longer lances need steadier pressure.
• Build for the environment: PP and stainless for wash and chemical, aluminium and PP for air work, stainless and nylon for field service.

Frequently Asked Questions

Wash gun or boom gun for crop work? Boom gun, high flow, flat-fan tip, built to push chemical across a row. A wash gun wastes most of its volume outside the target.

Why does my lance pattern wander? Usually supply pressure sag under the longer column, or a tip not matched to the flow. Steadier pressure and the right tip steady the pattern.

What inlet do I need? Match the gun’s BSP thread to the supply hose, 1/4“ for the air gun, 1/2“ for wash guns and lances, 3/4“ for the boom gun. A mismatch leaks or fits poorly regardless of spray quality.

Can I change the pattern on a gun? Yes, by changing the tip. The gun is the valve; the nozzle tip sets the pattern, and the same body runs flat, jet or cone tips within its flow band.

Why is my air-assisted gun’s flow so much lower than the wash gun’s? Because it is a different class of tool. Air atomisation is about droplet control, not volume: 0.5–5 L/min in a fine cone covers a finish or a dose without flooding the surface. If the job needs volume, that is the wash gun’s job, not the air gun’s.

How much flow do I need from the supply line? The model’s flow band at 3 bar is the reference. Remember flow rises with the square root of pressure, doubling pressure only raises flow about 40 percent, so a sagging pattern is usually a supply problem, not a pressure problem.

Can I fit a lance to my existing gun? Yes, if the inlet matches. A lance carries the gun’s flow to the work, 4–20 L/min across the range, and the pattern is set by the tip at the far end.

What material for chemical washdown? PP for corrosive chemicals and detergents, stainless where temperature or abrasion is involved, and aluminium for dry air work and occasional chemical use, not for aggressive fluids.