Why Is My Hydrocyclone Sending Coarse Particles to Overflow?

If you've noticed coarse particles—material that should be reporting to the underflow—showing up in your hydrocyclone overflow, you're facing one of the most common and frustrating problems in mineral processing. Coarse solids in the overflow (often called "overflow run coarse" or "coarse misplacement") impacts downstream processes, reduces recovery, and can lead to environmental compliance issues.

The good news: most causes are identifiable and fixable—often without replacing the entire cyclone.

Common Equipment Wear Points Causing Coarse Particles in Overflow

1. Worn Vortex Finder – The #1 Equipment Cause

A worn vortex finder has an enlarged inner diameter, increasing short-circuit flow. Even 1mm of wear can measurably affect performance.

Field insight: The vortex finder is an "invisible killer." Inspect at least every 3–6 months. Measure the inner diameter and check wall thickness.

2. Worn Apex (Spigot) – Responsible for 90% of Field Problems

For every 1mm of spigot wear, coarse particles in overflow increase. Establish a weekly spigot measurement schedule. Replace immediately once it exceeds 10% of original diameter.

3. Worn Feed Head and Cone Liners

Uneven wear disrupts inlet velocity and swirl pattern.

4. Spigot Size Imbalance

Too small = increased turbulence; too large = excessive circulating flow.

How Feed Pressure, Flow Rate, and Slurry Concentration Affect Coarse Particle Misplacement

Feed Pressure

• Higher pressure reduces coarse misplacement

• Lower pressure shifts cut size coarser

• Pump impeller wear causes gradual pressure drift—check pressure first

Slurry Concentration
High feed concentration causes hindered settling. When you see both overflow coarsening and underflow becoming finer, measure feed concentration first. Dilution often solves the problem.

Overflow Back Pressure
Degrades separation, allowing more coarse particles to bypass.

Design or Geometry Factors

• Vortex Finder Length – Shorter reduces coarse carryover

• Cone Geometry – Lengthening or convex cone reduces misplacement

• Ratio Between Vortex Finder and Apex Diameter – Critical for controlling overflow particle size

• Dense Media Effect – Light coarse particles misplace to overflow

Step-by-Step Diagnostic Process

If Everything Checks Out: Feed Stability Issues

Hydrocyclones require stable, non-pulsing feed flow. A faulty VFD setting or pipeline pulsation causes vortex collapse, allowing coarse particles to escape.

HUATAO: Your Partner for High-Performance Hydrocyclone Wear Components

What HUATAO Offers:

• Precision-machined vortex finders – ±0.3 mm tolerances

• High-performance polyurethane spigots – 3–5× longer wear life

• Complete hydrocyclone liner sets

• Feed head and cone section liners – full geometry matching

Why Choose HUATAO:

• Dimensional Precision

• Batch-to-Batch Consistency

• Proven Performance – 40% maintenance cost reduction

• Rapid Global Supply

• Technical Support

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Contact Us

Contact: Annie Lu
Email: annie.lu@huataogroup.com
Phone / WhatsApp: +86 180 3242 2676
Website: http://www.tufflexscreen.com

 Hydrocyclone, Coarse Overflow, Troubleshooting, Mineral Processing, Wear Parts, Vortex Finder, Spigot, HUATAO Group