Spiral Nozzles: Full Cone, Hollow Cone and Why They Don't Clog

A spiral nozzle is the anti-clog workhorse. Where a flat fan or misting tip blocks on grit, a spiral keeps running because it has no internal parts and a wide, open path. Liquid spirals down a single twisted vane into a cone. That simplicity is the whole point: it trades fine atomisation control for the ability to pass debris that would siege any other tip. The same family appears in catalogues and on search results as spiral spray nozzles, spiral jet spray nozzles, or a spiral nozzle spray pattern; every name describes this one open-vane body.

The Selection Framework: Four Numbers

Every spiral duty reduces to four numbers. Write them down before you touch a catalogue:

1. Cone type: full cone (even coverage of a surface or gas stream) or hollow cone (rim-only, for gas-liquid contact). This is the first and most common mistake to nail.
2. Flow at pressure: litres per minute at your line pressure. This picks the body size.
3. Free passage: the open path that beats clogging. Match it to your largest suspended particle, with margin.
4. Material: the chemistry and temperature of the fluid. PP for acids, PVDF for oxidisers, 316L for process water, ceramic for abrasives.

A spiral chosen without these four is a guess. With them, the selection is arithmetic.

Reference Flow Table (Clean Water)

Our standard spiral line, flow quoted at 1.5 bar:

Model	Pattern	Flow @ 1.5 bar	Free passage	Connection	Material
BJ-SP1/8	Full cone	0.2–0.8 L/min	2.5 mm	1/8“	316L / PP
BJ-SP1/4	Full cone	0.6–2.5 L/min	4.0 mm	1/4“	316L / PP / PVDF
BJ-SP3/8	Full cone	1.5–6 L/min	6.0 mm	3/8“	316L / PP
BJ-SP1/2	Full cone	4–18 L/min	9.0 mm	1/2“	316L / PP
BJ-SP3/4	Hollow cone	8–40 L/min	12 mm	3/4“	316L
BJ-SP1	Hollow cone	20–90 L/min	18 mm	1“	316L

Flows are at 1.5 bar with clean water. Viscous or hot fluid shifts the numbers. Send your duty for a real sizing.

Full Cone vs Hollow Cone

A spiral can be cut to make either:

• Full cone: liquid distributed across the whole circle; even coverage of a surface or gas stream. The default for scrubbing and cooling.
• Hollow cone: liquid on the rim only, a ring; used where you want the drops at the edge (some gas-liquid contact, some coating).

The cone type is set by the vane cut, not by a separate insert. So you pick full or hollow at spec time and the body stays the same.

Why It Doesn’t Clog

The path is a single open helix. There is no orifice cap, no pin, no small chamber to trap a particle. A solid of any size up to the inlet bore passes through. That is why spiral nozzles dominate:

• Gas scrubbing (particulate-laden gas streams).
• Quench tanks (dirty, hot water).
• Dirty process water (recycled, silt-laden).

Every other nozzle type in those duties clogs within shifts; a spiral runs for seasons.

Flow, Pressure and Droplet

Spiral flow scales with pressure (≈√P) and orifice. Droplet size is coarser than a misting tip at the same flow. You trade fineness for freedom from blockage. For scrubbing and quenching that is the right trade: you need throughput and uptime, not 20 µm drops. Sizes run from <1 L/min to >100 L/min, covering bench scrubbers to tank quenches.

Material for Abuse

• 316L stainless for most process water.
• PP / PVDF for chemistry; PVDF for heat and oxidisers.
• PTFE-lined for broad resistance.
• Ceramic or silicon-carbide in abrasive slurries (the vane erodes, body doesn’t).

For scrubbers on acidic gas, PP or PVDF spiral bodies survive where metal corrodes.

Troubleshooting

1. Reduced flow, no block → pressure sag, not clogging. Hold pressure.
2. Uneven cone → vane damaged (impact). Replace the body.
3. Wrong cone type → specified hollow, needed full (or vice versa). Re-spec the vane cut.
4. Erosion → abrasive fluid, metal vane wearing. Step to ceramic/silicon-carbide.

How We Compare to the Catalogue Brands

The spiral lines (Spraying Systems, BETE, Lechler) publish full/hollow cone flow and angle per size. Our spirals track the same ratings. A 1/2“ full-cone at rated pressure flows what their equivalents do, with the same anti-clog path. What a buyer weighs is material cert for the gas/liquid, spare-body stock, and lead time. We publish flow and cone per size so you size against the same numbers.

The Physics of the Open Path

A spiral nozzle is a single twisted vane inside a body: no orifice cap, no pin, no small chamber. Liquid enters and spirals down the vane, exiting as a cone. The geometry explains the two things spirals are famous for:

• Anti-clogging: the path is as wide as the inlet bore, all the way through. A particle that fits the inlet passes the whole body. There is no narrow seat to sieve on.
• Coarser drops: the vane does less fine atomisation than a swirl chamber or a pin. You trade droplet fineness for an open path and uptime. For scrubbing and quenching that is the right trade.

The spiral is the answer to the question “what do I use where everything clogs?”. And the answer is the nozzle with nothing inside to clog.

Industry Applications: Where Spirals Earn Their Keep

• Gas scrubbing (wet scrubbers): full-cone spirals saturate particulate-laden gas streams; the open path survives the grit that sieges every other tip.
• Quench tanks: hot, dirty water at high flow; a spiral keeps running shift after shift where a misting tip blocks in hours.
• Washdown in dirty service: recycled water, silt, debris; the spiral passes it.
• Cooling towers: full-cone spirals distribute water evenly over the packing; the open path shrugs off scale and slime.
• Chemical reactors: PVDF or PTFE spirals on corrosive service; the chemistry is the spec, not the clog.
• FGD and flue-gas systems: abrasive, acidic slurry; ceramic or PVDF spirals survive the duty.

Each application is the same four numbers with a different answer set.

Worked Example

You scrub a particulate-laden exhaust (dirty, slightly acidic) at 40 L/min per point.

1. Cone → full cone for even gas-liquid contact.
2. Flow → pick the size at your line pressure (say 1/2“ full cone ~40 L/min).
3. Material → acidic → PP or PVDF body.
4. Anti-clog → spiral path passes the particulate; no screen needed.

Runs seasons without a blockage.

FAQ: Spiral Questions We Actually Get

Q: Full cone or hollow cone for my scrubber? A: Full cone for even saturation of the gas stream; hollow cone when you want the drops at the rim for gas-liquid contact. The vane cut sets it. Specify at order time.

Q: Why does my spiral “clog” when it’s supposed to be anti-clog? A: It doesn’t clog internally. The blockage is at the inlet or the line ahead of it. Check the strainer and the pipe, not the nozzle.

Q: Are spirals always coarser than other nozzles? A: Yes, at the same flow. The open vane does less fine atomisation. Use a spiral where uptime beats droplet fineness (scrubbing, quenching); use a misting or flat-fan tip where the drop matters.

Q: What pressure do spirals run at? A: Typically 1–4 bar; the flow scales with the square root of pressure. Higher pressure gives more flow and finer drops but more wear.

Q: 316L or ceramic for my duty? A: 316L for clean process water; PVDF or PP for chemistry; ceramic or silicon-carbide when the fluid is abrasive (the vane erodes, the body doesn’t).

Maintenance: What Kills a Spiral

• Vane erosion: abrasive fluid slowly wears the vane; the cone distorts and flow rises. Ceramic or silicon-carbide vanes survive where metal erodes.
• Scale and deposits: hard water scales the vane; the pattern narrows. Descale on a schedule.
• Chemical attack: the wrong material for the fluid. Match material to chemistry with margin.
• Mechanical impact: a dropped or struck spiral bends the vane; the cone is never right again. Replace, don’t straighten.

A spiral is a wear part. Inspect the cone pattern on a schedule; a distorted vane is a process drift you can’t see from the outside.

Selection Checklist (Print This)

• Cone type chosen: full for even coverage, hollow for rim contact
• Flow at line pressure summed across all nozzles
• Free passage ≥ largest suspended particle, with margin
• Material matched to chemistry + temperature + abrasion
• Strainer upstream: spirals don’t clog, but lines do
• Spare bodies on the shelf: the vane wears

Material Selection Table

Material	Max temp	Chemistry	Best for
316L SS	~300 °C	Process water, mild corrosives	The default
PP	~80 °C	Acids, alkalis	Light chemical duty, cheap
PVDF	~140 °C	Oxidisers, halogens, acids	Aggressive chemistry
PTFE-lined	~200 °C	Broad	Worst-case chemistry
Ceramic / SiC	~600 °C	Abrasives	Slurries, grit, FGD

The material is chosen by the chemistry first, then the temperature with margin, then the abrasion. A 316L spiral on an acidic scrubber fails; a PVDF one on clean water is overkill.

Worked Sizing: A Scrubber Ring

A wet scrubber on a particulate-laden, slightly acidic exhaust needs even gas saturation at 40 L/min per spray point, 1.5 bar line.

1. Cone → full cone for even gas-liquid contact.
2. Flow → BJ-SP1/2 full cone at ~18 L/min; two per ring point covers 36 L/min at 1.5 bar. Or BJ-SP3/4 at 40 L/min.
3. Free passage → the exhaust carries grit; the 9–12 mm passage passes it. No screen needed.
4. Material → acidic → PVDF body.

Answer: BJ-SP1/2 full cone, PVDF, two per point. Runs seasons without a blockage.

The Five Mistakes to Avoid

1. Hollow cone where full was needed: the rim-only pattern leaves the gas stream under-saturated in the centre. Nail the cone type first.
2. Sizing flow, ignoring free passage: a fine-orifice spiral on gritty water still blocks at the inlet. Match the passage to the particle.
3. 316L on chemistry: the fluid eats it. Match material to chemistry with margin.
4. No strainer upstream: spirals don’t clog internally, but the line and strainer do. Strain the supply.
5. Forgetting the vane wears: an eroded vane drifts the cone invisibly. Inspect the pattern on schedule.

Every one is a system error. Size the four numbers and the five mistakes disappear.

What to Send a Supplier for a Quote

1. Cone type and flow: full or hollow, litres per minute at your line pressure.
2. Fluid and temperature: chemistry, hot/cold, pH, suspended solids.
3. Abrasion: is the fluid gritty? This decides ceramic vs metal.
4. Count and layout: how many points, ring or header, spacing.

With those four, the quote comes back with a model. Without them, every supplier picks blind.

Flow, Pressure and the Cone That Scales

Spiral flow follows the standard nozzle curve: flow scales with the square root of pressure. Double the pressure, flow rises ~41%. Three practical consequences:

• The 1.5 bar rating is a baseline, not a law: a BJ-SP1/2 at 3 bar flows ~26 L/min instead of 18. Size against your actual line pressure.
• Higher pressure, finer drops, more wear: the vane cuts better at speed but erodes faster. In abrasive service, run the lowest pressure that meets the flow; the cone lasts longer.
• Low pressure stalls the cone: below ~0.5 bar the pattern collapses into a dribble. Keep the line pressure in the rated band.

The same body covers a wide flow range, that is the spiral’s flexibility, but the droplet and wear change with it. Set the pressure for the job, not the pump’s maximum.

Droplet Size and What It Buys

Spirals are coarser than misting tips at the same flow, typically 300–1000 µm depending on pressure and size. That coarseness is the point in the spiral’s three core jobs:

• Scrubbing: coarse drops have the momentum to collide with particulate and carry it down; a fine fog passes through the gas stream without contact.
• Quenching: hot parts need a drop that reaches the surface before it flashes to steam; coarse drops deliver mass fast.
• Washdown: dirty surfaces need volume and impact, not fine coverage.

If your job needs fine drops (coating, humidification), a spiral is the wrong tool. It is built for throughput and survival, not finesse.

The One-Paragraph Summary

A spiral makes a full or hollow cone through one open vane with nothing inside to clog: pick the cone type, size the flow at your line pressure, match the free passage to your dirt, and match the material to your chemistry. Then let the open path do its job in the duties that kill other nozzles.

When the Spiral Is the Wrong Tool

The spiral loses when the drop matters: coating wants an air atomizer, humidification wants a misting tip, and a graded band wants a flat fan. The spiral owns dirty, high-flow, no-finesse duty: scrubbing, quenching, washdown. Outside that, the tool changes.

Troubleshooting: The Full Checklist

When a spiral “isn’t working,” walk this list in order:

1. Reduced flow, no visible block: pressure sag. Check the line pressure at the tip, not the gauge at the pump.
2. Uneven or lopsided cone: vane damage (impact) or heavy scale. Inspect; replace if bent.
3. Dribble instead of cone: pressure below ~0.5 bar, or the vane is worn to nothing. Raise pressure or replace.
4. Pattern narrows over weeks: scale building on the vane. Descale; feed filtered or softened water.
5. Flow rises over months: vane erosion enlarging the path. In abrasive service this is wear, not malfunction. Replace on schedule.

Ninety percent of “bad spiral” tickets are pressure or upstream blockage, not the nozzle.

How We Compare to the Catalogue Brands

The spiral lines (Spraying Systems, BETE, Lechler) publish full/hollow cone flow and angle per size. Our spirals track the same ratings. A 1/2“ full cone at 1.5 bar flows what their equivalents do, with the same open anti-clog path. What a buyer weighs is material cert for the gas or liquid, spare-body stock, and lead time. We publish flow and cone per size so you size against the same numbers, and we stock ceramic and PVDF bodies for the same duties their catalogs cover.

Spiral vs Spiral: Full-Cone Grades

Full-cone spirals also come in distribution grades, even and “peak” (centred) profiles:

• Even distribution: uniform liquid across the whole circle. For scrubbing and cooling where every point of the gas stream or packing gets the same.
• Peak/centred distribution: more liquid in the core. For duties that want a heavier centre impact, or where the spray overlaps with neighbours and the centres need the boost.

Most scrubbers want even; some quench rings want peak. It is a spec-time choice, the same body, another reason to send the duty, not just the size.

Sizing the Ring: More Than One Spiral

Most spiral installations are rings or grids, not single nozzles:

• Ring spacing: the cone’s coverage at the target distance sets the ring radius; space rings so the cones overlap at the packing or the gas stream.
• Total flow: a 12-nozzle ring at 18 L/min each is 216 L/min; the pump and header must hold pressure at that total.
• Header balance: loop the header or size it so the last nozzle sees the same pressure as the first; a dead-end line starves the far side.

The single-nozzle spec is the easy part. The ring is where scrubbing performance is won or lost.

The Bottom Line on the Open Path

The spiral’s whole reputation rests on one sentence: nothing inside to clog. Every other nozzle type trades uptime for finesse; the spiral trades finesse for uptime. In a scrubber, a quench tank, or any dirty high-flow duty, that is the winning trade. The open vane passes the grit, the cone stays true, and the line runs while the fine-orifice tips next door are being rodded out. Choose full or hollow, size the flow and passage, match the material. And let the open path work.

Quick Reference: Cone Type by Duty

Duty	Cone	Why
Wet scrubber, gas saturation	Full	Even contact with the gas stream
Quench ring	Full or peak	Volume to the surface, coarse drops
Gas-liquid contact column	Hollow	Drops at the rim where the gas rises
Cooling tower packing	Full	Even distribution over the packing
Dirty washdown	Full	Coverage + open path
Chemical reactor	Full or hollow by spec	Chemistry drives material, not pattern

The cone type is the spec, the material is the survival. Pick both at order time and the spiral does the rest.

Bottom Line

A spiral nozzle makes a full or hollow cone with one open vane and no internal parts, which is why it doesn’t clog when every other tip blocks. Use it for dirty water, gas scrubbing and quench tanks where uptime beats fine atomisation. Pick full or hollow cone at spec, size by flow and pressure, and let the open path handle the debris.

Need a spiral rated for your flow, pressure and particle size? Send your duty to our enquiry form or compare the spiral nozzle range.