EN
News
Three Nozzle Patterns And The Faces Each One Misses
Three patterns, one header, forty nozzles. The part comes out clean on the faces that point at the header and untouched on the faces that run parallel to it, and the pressure gauge reads exactly what it read on the last machine.
This is the most common way a washer underperforms while looking correct. The pressure is right, the flow is right, the nozzles are new, and a third of the surface is still being missed. What is wrong is the shape of the jet, not its force.
1. Pattern Decides Where The Energy Goes
A nozzle converts a pressure drop into a jet with a particular shape. The total energy delivered is roughly the same whatever the shape, but the shape decides whether that energy lands on a strip, a disc or a point.
A flat fan concentrates the flow into a narrow band. A full cone spreads it over a circle. A solid stream concentrates it into a coherent column. Each is the correct choice for a different surface, and each has a characteristic blind spot that no increase in pressure removes.
Impact force also falls off with distance. At twice the stand-off the jet has spread and slowed, and the force per unit area is a fraction of what it was. That is why a nozzle set chosen for a 100 mm gap behaves nothing like the same set at 250 mm, and why copying a header from one machine to another rarely reproduces the result.
2. Flat Fan: Strong Along A Line
A flat fan is the default for parts that pass under a header on a conveyor. The jet forms a thin band, often described by its spray angle, and a row of nozzles produces overlapping bands across the width of the part.
Its strength is impact per unit area. Because the flow is concentrated rather than spread, a flat fan at 1.0 MPa delivers more force to the strip it covers than a full cone of the same flow. On a flat machined face moving under the header, that is exactly what is wanted.
Its blind spot is everything not perpendicular to the jet. A face running parallel to the direction of travel receives the band edge-on, which is a glancing contact rather than an impact. On a housing with four vertical walls under a horizontal header, two walls get a direct hit and two get almost nothing, and the difference is invisible in any pressure reading.
3. Full Cone: Area Without Depth
A full cone distributes the flow across a circular footprint, with the highest density near the axis and a falling edge. It is the choice for parts with no dominant face: castings, brackets, irregular components that present several surfaces at once.
Its advantage is coverage. A single full cone can wet a circle several hundred millimetres across, which means fewer nozzles and a simpler header. Where the requirement is to get liquid onto every surface rather than to blast one of them, that is efficient.
Its blind spot is depth. The same flow spread over a large area produces a much lower impact force, and a cavity more than a few diameters deep receives wetting without displacement. A blind hole under a full cone fills with liquid and keeps its contamination; the liquid has reached the surface without moving anything off it.
4. Solid Stream: Depth Without Area
A solid stream produces a coherent column rather than a spray. It holds together over a longer distance, which is why it is used for bores, galleries and anywhere the target is a hole rather than a face.
At high pressure, a solid stream is the only pattern that reaches the far end of a deep passage with enough force to displace what is in it. This is the reason oil gallery cleaning runs at pressures an order of magnitude above general washing: the pattern is being used as a lance, and a lance needs velocity rather than flow.
Its blind spot is everything outside the column. A solid stream covers a circle measured in millimetres, so a face needs either an array of streams or a scan to cover it. On a part with both a gallery and large external faces, a solid-stream header cleans the gallery and does nothing useful elsewhere.
| Target on the part | Pattern | Why the others fail |
|---|---|---|
| Flat machined face, moving under the header | Flat fan | Full cone spreads force too thin; stream covers too small an area |
| Irregular casting, several faces at once | Full cone | Fan misses faces parallel to the band; stream needs aiming per feature |
| Oil gallery, bore, deep blind hole | Solid stream, high pressure | Fan and cone wet the entrance and stall |
| Thread roots, cross-drillings | Solid stream at an angle | Any pattern aimed along the axis passes over the root |
5. Mixing Patterns On One Header
Most production headers need more than one pattern, and this is where a well-designed machine and a copied one diverge.
Nozzles fed from a common manifold do not share flow equally. Each nozzle presents a resistance, and a solid stream nozzle with a small orifice presents more than a full cone with a large one. On a shared header the higher-resistance nozzles receive less flow, and the pressure gauge at the manifold reports an average that describes none of them.
The practical fix is separate circuits for circuits with different duties, or individual flow control at each branch. It costs more pipe and it is the difference between a header that works as designed and one that works on the nozzles with the least resistance.
6. Finding Which Pattern Is Underperforming
The diagnosis does not need instruments. It needs a part and a pattern of where the dirt survived.
If the failures are on faces parallel to the header, the coverage is wrong and the pattern is a fan where a cone was needed. If the failures are at the bottom of holes, the pattern cannot reach the depth. If the failures are in a ring around where a stream lands, the jets are too few and too narrow. If the failures follow one nozzle position across many parts, that nozzle is blocked or worn rather than misapplied.
Testing a header takes an hour: clamp a sheet of water-sensitive paper or a thin layer of flour at the working distance, run one cycle, and look at the footprint. What appears is the coverage the part actually receives, which is often nothing like the drawing.
7. What To Specify
A nozzle specification that can be built to names four things: the pattern per circuit, the spray angle, the stand-off distance at which the angle applies, and the flow per nozzle at the working pressure. Everything else is a consequence.
What should not be specified is a single pressure for the whole machine. Pressure is what a pump delivers, not what a surface receives, and the surface receives whatever the pattern and the distance allow. Machines that fail while meeting their pressure specification are almost always machines where this distinction was never written down.
The useful summary is that a washer has three ways to be wrong and only one gauge to show it. Pattern, distance and coverage do not appear on the gauge at all, and on a header with forty positions, that is where most of the missed surface lives.
