Medium SG drift is usually the first point to consider separately against your actual washability curve. Density drift shifts the achieved cut point directly, even when the cyclone itself is mechanically sound. If your medium density isn’t holding at the target you designed the cut point around, no amount of cyclone geometry corrects for it.

Medium rheology is the second factor, and it’s driven largely by magnetite granulometry and solids concentration rather than anything happening inside the cyclone body. Poor medium viscosity widens Ep directly because particles don’t respond cleanly to the density gradient the cyclone is trying to create; the medium itself is behaving inconsistently before separation even happens. We go into the specification numbers that hold this steady in our post on magnetite quality and granulometry.

Cyclone wear changes the internal geometry the design assumes. Liner wear, particularly at the spigot, gradually alters the flow pattern inside the cone. A worn spigot that’s grown beyond its design diameter changes the underflow density the cyclone can hold, which widens Ep well before the wear becomes visually obvious from outside the unit.

Feed pressure outside the design range works against separation from a different angle. Heavy media cyclones are sized for a specific feed head run below it and centrifugal force drops, widening EP run. meaningfully above it, and turbulence increases inside the cone, which also degrades separation sharpness rather than improving it.

When spigot capacity is exceeded, roping becomes visible, where the underflow discharge loses its normal spray pattern and instead ropes out in a dense, coherent stream, which is the clearest sign that something upstream has pushed more solids through the spigot than it can properly discharge. Once roping starts, Ep degrades quickly, and it’s usually a downstream symptom of one of the other four causes rather than an independent fault.

The vortex finder-to-spigot diameter ratio sits behind several of these symptoms at once. That ratio is what the cyclone’s design assumes when balancing overflow and underflow splits, and it’s fixed by the geometry John Finlay specifies for a given duty. Spigot wear changes the ratio directly. Feed pressure outside the range changes the effective split even with the physical geometry unchanged. Medium rheology issues change how the solids actually distribute across that split regardless of what the ratio nominally is. None of these show up as a single obvious fault; they show up as the ratio no longer doing the job it was sized for, and Ep is usually the first number to reflect that.