A thickener is a processing plant equipment that is used for de-waters slurry, separating the liquid from the solids – aiding ore processing. Thickeners plants are designed to operate continuously. They operate on a particle/floccule sedimentation principle which means the solids are made to settle at the bottom of the thickener tank and the water or less dense material gets to float and overflow to be collected through a dedicated channel, whereas the dense material is drawn with the aid of underflow pumping system

Figure 1-Thickener operating principle

The thickener in a mineral processing plant plays a crucial role in the mineral recovery process. Any failure causing the thickener to stop literally cripples the whole processing plant. Hence the equipment criticality.


The thickener as a unit is made up of systems or assemblies that can be classified into 4 namely:

  1. Structure
  2. Drive system
  3. Instruments
  4. Underflow system

Each assembly on the thickener acts as a parent to several constituent maintainable items (msi). In all equipment failure or primary source of failure for the ultimate equipment takes place at maintainable item level – See table 1 below

Failure modes can be characterized as age-related which involve equipment that is subjected to continuous stresses throughout their lives, while non-age-related failure modes are linked to equipment that receive intermittent stresses during their lives. It is also important to note that several different failure modes can occur on an individual maintainable item hence the need to have in place a dedicated mitigation measure or task for each individual potential failure mode – See table 2.


Just like all other equipment/components failure on a thickener can also be attributed to two main factors:

  1. Maintenance oversight
  2. Improper operation of equipment

See some of the prominent and potential failures that occur on thickener units – see table 3

What is your experience with a thickener, prominent failures and how did you resolve the issues?

By Cecil Kgosi Manala