All the operator has to do is set the water injection rate. The Hydrosizer™ control monitors the classification environment and adjusts the underflow valve to maintain a consistent performance. The McLanahan Hydrosizer™ maintains separation automatically through a simple PID control loop. Maintenance of this bed is easily done through a simple set of controls. This phenomenon slows down the settling rates of particles and allows them to be more critically reviewed as either a member of the coarse or fine fraction. Within this teetered bed, solids settle through the tank in an environment known as hindered settling. This accumulation is described as a teetered or fluidised bed, similar in many ways to quick sand. Particles that are near the size of separation, being neither massive enough to migrate to the underflow cone nor small enough to be lifted out, begin to accumulate in the separation chamber. Coarser and denser particles pass downward through this current and are collected in the underflow cone to await discharge. As particles in the feed meet this rising current of water, finer and less dense fractions are lifted out and swept over the overflow weir. This water injection causes an upward rising current of water that flows over the peripheral weir and is collected in the overflow launder.

Simultaneously, process water is injected through an array of pipes located near the bottom of the separation chamber. This phenomenon is the result of a fluidised (teetering) bed of particles or dense media created in the vertical-walled separation zone.įeed material (typically Hydrocyclone underflow) enters the top of the unit via a central feed-well. The light coffee and brokens move further down the screen for discharge in front of the machine.To make its sharp wet classification, Hydrosizers™ use the hindered settling principle. The coffee moves on an air cushion and due to the rocking motion and tilt of the machine, the heavy particles move to one side of the machine for discharge. Gravity Tables can be supplied with or without feed Elevators. Separate discharge spouts for broken beans, lights and heavies are provided for bagging or for further processing. Where desired, a hood can be provided for dustless operation and suitable piping for connection to an aspiration system (As an add on accessory). The machine is equipped with an input hopper with regulating device for feed control. The Gravity Tables can be adjusted for throw and tilt in laterally and in vertically.Ī well designed fan and air distribution system, at the bottom of the machine, ensures even supply of air. Ideally, best results can be achieved, if the coffee is graded, catadored and then passed through these Tables. McKinnon Gravity Tables, when adjusted well, effectively remove all triage besides providing coffee of uniform weight. They can be used in conjunction with Closed Circuit Catadors for best results or even as an alternate to Catadors. The McKinnon Gravity Tables are used after hullers and peeler polishers to separate heavy and light beans.

Wet gravity circuit