Spiral Spray Nozzles

A spiral nozzle has no internal vane, no swirl chamber and no removable insert. The liquid follows a helical ramp machined into a single piece of metal and leaves as a series of concentric cones. That one design decision — an open flow path with nothing narrow inside — is why spiral nozzles dominate duties where the liquid is dirty and downtime for unclogging is expensive.

They are not the most precise nozzle in the catalogue. What they are is the nozzle that keeps running when the water is recycled, gritty or carrying fibre.

Why the Open Path Matters

In a conventional cone nozzle, the pattern is created by forcing liquid through a swirl chamber or around a vane before it reaches a small orifice. Every one of those internal features is a place for solids to lodge. A spiral achieves the same rotational component externally, on an open ramp, so the narrowest point in the whole nozzle is the exit itself.

The practical consequence is a free passage substantially larger than a comparable cone nozzle at the same flow rate. Recycled scrubber liquor, cooling tower water and quench water all carry solids that a conventional cone would eventually catch.

Full Cone Versus Hollow Cone Spirals

Full cone spirals produce overlapping cones that fill the whole spray envelope, including the centre. Coverage is even across the footprint, which is what gas cooling, quenching and dust suppression want — the gas or dust has to meet droplets everywhere, not just at the edges.

Hollow cone spirals leave the centre open and concentrate the liquid into a ring. Scrubbing and absorption duties often prefer this, because the ring pattern presents more liquid surface area per litre to the gas stream, and the open centre lets gas pass without being shielded by a dense core of droplets.

The choice is not cosmetic. Putting a full cone where a scrubber was designed for hollow cone changes gas-liquid contact and can drop removal efficiency measurably.

Droplet Size and Coverage Trade-off

Spirals produce a broad droplet distribution rather than a tight one. That is a consequence of the open design: without a precision swirl chamber, you get a range.

For gas cooling that breadth is often an advantage — fine droplets flash off quickly and the coarser fraction reaches further into the duct. For anything requiring a controlled droplet band, an air atomizing nozzle is the better tool.

Where Eductors Fit

An eductor is a close relative worth knowing about. Instead of spraying into open air, an eductor nozzle uses the momentum of the pumped stream to draw in surrounding liquid, multiplying the volume moved without extra pumping capacity. Submerged in a tank, a small pumped flow can circulate several times its own volume.

That makes eductors the standard answer for in-tank mixing and keeping solids in suspension, where a spray nozzle would be the wrong device entirely. If your problem is stratified liquid or settling solids rather than surface cleaning, this is the direction to look.

Reference Specifications

Flow figures are quoted at 1.5 bar, which is the typical design point for spiral nozzles in scrubbing and cooling service. These nozzles run at low pressure by design.

How to Select a Spiral Nozzle

• Pattern requirement — full cone for coverage and cooling, hollow cone for gas contact and scrubbing.
• Solids content and particle size — this drives the free passage you need, and therefore the minimum nozzle size regardless of flow.
• Available pressure — spirals are low-pressure devices. Pushing them hard does not improve the pattern much and wastes pumping energy.
• Material — 316L for most scrubbing duties; PP, PVDF and PTFE where the liquor is aggressive; brass only for clean water service.
• Orientation — spirals can spray up, down or horizontally with the pattern intact, which is why they suit multi-level scrubber headers.
• Whether you actually need a spray — if the duty is in-tank mixing, an eductor moves far more liquid per unit of pumping.

Frequently Asked Questions

Why is my spiral nozzle pattern uneven? Usually erosion of the spiral ramp after long service, or a partially blocked exit. Unlike insert nozzles there is nothing to replace internally — a worn spiral is replaced whole.

Can a spiral nozzle handle slurry? Mild slurries, yes, which is a large part of their appeal. Heavily abrasive slurries will erode the ramp over time, so hardened material or scheduled replacement should be part of the plan.

What pressure should I run? Most spiral duties sit between 0.7 and 3 bar. If your system runs much higher, check whether a different nozzle class fits the duty better rather than throttling to suit.

Are spiral and full cone nozzles the same thing? No. Full cone describes the pattern; spiral describes how the pattern is made. You can get a full cone pattern from a vaned nozzle or from a spiral, and they behave differently on dirty water.