When Wear on the DMS Cyclone Vortex Finder Causes Loss of Efficiency Through Misplacement
When it comes to dense media circuits, it’s important to minimize product loss for obvious reasons.
Loss of efficiency in a Dense Media Separation (DMS) circuit is generally due to poor density control, media contamination and over feeding, as well as excessive cyclone wear especially to an internal cyclone component such as a vortex finder.
In one case, a client who had been operating eight cyclones on two parallel circuits for ten months in a highly abrasive environment noticed a loss of production efficiency. The operating staff wondered what was going on with their process, as the wear measuring protocols in place indicated minimal cyclone wear.
Poor separation in DMS caused by wear occurs over time when the length of the vortex finder is reduced and the interface between cone and spigot becomes grooved. Other components may also show signs of grooving. The rate of wear depends on the ore properties, so it is important to initially monitor your cyclones for wear and determine how many tonnes they can treat before separation efficiency deteriorates below acceptable levels.
Wear changes the internal geometry and dimensions of the cyclone and therefore alters the cyclone’s performance parameters over time, density cutpoint and media differential.
For that specific case, we, at Multotec Canada, were convinced that wear had played a major role in the loss of efficiency and immediately recommended the replacement of one circuit (four units) with new cyclones.
We have also asked to receive the replaced units our warehouse for further inspection by our team. Finally, because DMS is such a complex circuit with numerable different equipment, we sent one of our process engineers at the client site to take a quick look at the circuit to determine if anything around the cyclone could be affected the efficiency.
Majority of the damage observed occurred on the vortex finder.
In all cases, the vortex finder had lost an average of 39% of its thickness and 8% of its height, which caused increased misclassification.
Uneven wear in the barrel and cone resulted in the creation of steps at the junction of the two causing further turbulence within the cyclone body, and cavitation was found in the inlet head, as shown in the figure below.
Upon our process engineer visit on site, it was determined the client that the process was running fairly normally, although the client had initiated a change back to the previous process parameters.
Once the cyclones had been replaced and in conjunction with the client reverting back to previous process conditions, production returned to normal. The client was satisfied that its process was not to blame and a preventive maintenance procedure was put in place.
If you want to maintain optimum performance with minimum misclassification due to the wear of internal parts, preventive maintenance is the key and we recommend replacing your DMS cyclones when they reach the end of their life. The life of a cyclone is about four to six months in highly abrasive DMS environments.