Flat Fan Spray Nozzles

A flat fan nozzle produces a flat, elongated sheet of liquid. It is the workhorse pattern for anything that has to be covered evenly on a moving line — washing, rinsing, coating, cooling and dust knockdown all lean on it.

Two things decide whether a flat fan works: the spray angle and the edge distribution. Get either wrong and you either miss coverage or double-dose the middle of the belt.

Spray Angle and Coverage Width

Coverage width is a function of angle and distance. Wider angles cover more ground from the same standoff but lose impact, because the same energy is spread over a longer line.

Coverage figures assume spraying perpendicular to a flat surface. Angled installations and overlapping headers change the effective width, which is why header layouts are worth checking rather than assuming.

Tapered Edge Versus Even Distribution

Tapered edge fans thin out towards the ends of the sheet. That is what you want when nozzles are mounted in a row and their patterns overlap — the thin edges blend into a uniform line without a heavy band where they meet.

Even distribution fans put roughly the same volume across the whole width and stop abruptly. These suit single-nozzle duties where there is no overlap to worry about.

Mixing the two on the same header is a common cause of streaking on coated products.

Flat Jet Versus Wide Angle Jet

A narrow flat jet concentrates energy into a thin high-impact line — that is the deburring, descaling and cutting end of the range. Wide angle jets trade that impact for a broad curtain at low pressure, which is what dust suppression and humidification duties want.

The practical rule: if you are trying to remove something mechanically, go narrow and raise pressure. If you are trying to wet something evenly, go wide and drop pressure.

Reference Specifications

Flow figures below are quoted at 3 bar. Flow through a fixed orifice scales with the square root of pressure, so a nozzle rated 4 L/min at 3 bar delivers roughly 5.7 L/min at 6 bar rather than 8.

How to Select a Flat Fan Nozzle

• Target width and standoff distance — these two together set the spray angle. Fix the mounting distance first, since it is usually constrained by the machine.
• Impact required — cleaning duties need narrow angles and higher pressure; wetting duties need the opposite.
• Overlap — if nozzles sit in a row, specify tapered edge and plan the overlap rather than butting patterns together.
• Flow budget — total flow is nozzle flow multiplied by nozzle count. Header sizing and pump capacity fall out of this.
• Fluid and solids — larger free passage resists clogging; strainers belong upstream of small orifices.
• Material — stainless for most duties, hardened or ceramic inserts where abrasive wear dominates, plastics where chemical attack is the concern.

Frequently Asked Questions

What spray angle should I use for a 400 mm wide belt? At 300 mm standoff a 65 degree nozzle gives roughly 380 mm, so one nozzle nearly covers it and two overlapping 40 degree nozzles give a more even result with more impact.

Why does my flat fan pattern look streaky? Usually either mismatched edge types across a header, partial clogging in one nozzle, or patterns butting rather than overlapping. Check the pattern of each nozzle individually against a dry surface.

Can I raise pressure to get more coverage? No. Pressure raises flow and impact but barely changes spray angle. Coverage comes from angle and distance.

What is the difference between a flat fan and a flat jet? They describe the same family. In practice flat jet is used for the narrow, high-impact end and flat fan for the wider, general-coverage end.