Sometimes, when there is not enough weight of material to perform many concentration tests, the metallurgist has to look for small equipments. The Flat Spiral is a good option and was developed based on the Humphreys spiral that was created a long time ago. The equipment is a rotary circular plate with a spiral on its surface. The plated is tilted and supported on a structure and the water is added from one side to the center. During the operation the material is fed on one side and the tails are discharged at the bottom and the concentrate is going to the center and discharge by a hole located in the center of the circular plate.
The equipment operates based on the action of gravity and hydraulic forces created by the rotation of the spiral and the water addition. Essentially, during the rotation, the heavy material is forced to pass into the canals. When the water is added the concentrate is cleaned and the lighter particles are directed to the tails.
The material to be tested by the equipment must be fine, approximately 100% passing 600 µm. Try to pass coarser material is more difficult and the separation efficiency and operatively of this equipment are reduced. Some manufacturers of this kind of equipment modify the number of spirals and the number. By doing this change the route to be followed by the heavy material is modified by the time exposed to water flow.
Schematic view of flat spiral