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How do Hydrocyclones work?

27 Mar

In a Sand Washing and Production context, Hydrocyclones produce superior results. We compare sand washing plant and explain how hydrocyclones work.

How do Hydrocyclones work?

In a Sand Washing Plant context Hydrocyclones use Fluid Dynamics to separate different types of particles from each other; such as lighter silt and clay from heavier sand particles.

Hydrocyclones rely on centrifugal force of water being pushed throw a chamber of decreasing size to separate its material. The outlet cylinder at the top is responsible for the production of the cyclone, the subsequent vacuum and the 'cut point'. The cut point determines the size of the material being extracted as overflow, this would be silt, clay and very fine particles in a concrete sand production scenario. (Certain Hydrocyclone plants also offer the ability to recover these ultra-fines for specialist materials)

Material that is heavier than the cut-point that cannot be overcome by the vacuum are discharged out the bottom as underflow. This is the desired product in concrete sand production as it contains the grading of sand that has been fed from the washing and screening plant with the all the silt and clay removed.


Hydrocyclones have some significant benefits over other sand washing plants. These key benefits are:

  • Better sand extraction efficiency.
    Hydrocyclones extract with up 95% efficiency with the lowest loss of passing grade sand.
  • 100% potential throughput capacity without any sand loss.
    Hydrocyclones can be run at full throughput capacity, efficiency does not decrease with more material.
  • Coupled with an integrated dewatering screen, it produces sand with less moisture content.
    The MWS CSP range features a built in dewatering screen which means that off the moisture content is only 10% off the conveyor and can be sold straight away.
  • It has no moving parts.
    Since the Hydrocyclones use water for washing and moving material through it, there are no internal moving parts, just water pumps.


Although there is no 'one-size' fits all solution to sand aggregates there are a number of advantages to Hydrocyclone washing plant compared to traditional washing solutions.


Sand screws have been used in washing systems for decades and when setup correctly produce results that make money, hence their continued use.

Sand screws work by floating off the lighter clay and silts and auguring up the coarser sand. But they have a number of downsides namely:

  • They may have a rated throughput but can never been run at full capacity without losing valuable sand into the settling ponds. At best sand screws can be run 50% and could lose up to 30% of fine passing grade sand.
  • They produce a very wet product with a moisture content around 25-28%. This must be allowed dry before sale.


A much older style of washing system but still found in use in some areas.

Bucket wheels are capable of finer cuts that Sand Screws at an albeit slower rate and larger size. In comparison their downsides are:

  • Their extraction efficiency is around 80-85% with the fine passing grade sand going into ponds.
  • They produce a very wet product with a moisture content around 25-30%. This must be allowed dry before sale.

If you're looking at washing plant and want to understand more of the principles behind washing and achieving the products you want get in touch and we can discuss your operational goals.

See more of our MWS Washing Range here.

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