Wilfley Shaker Table

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The most popular of several similar devices, the Wilfley Shaking Table was developed in the 1890s. It has been in use since and is a common device for concentrating particles in the intermediate range, such as 10-200 mesh (1.65 mm-74 pm) particles for ore and 3-100 mesh (6.7 mm-150 pm) for coal. It is an oblong, shaken deck, typically 1.8- to 4.5-m wide; the deck is partially covered with riffles that taper from right to left. The deck is gently sloped downward in the transverse direction. Feed enters at the upper right and flows over the riffled area, which is continually washed from a water trough along the upper edge of the deck. Heavy particles are concentrated behind the riffles and are transported by a bumping action (of 12-25 mm throw at 200-300 strokes/min) to the left end of the table where flowing film concentration takes place.
Three stages of gravity concentration were used. The primary concentrator was a Reichert Mark VII spiral. The spiral was fed 4.77 m³/hr (21 gpm) of slurry at approximately 30-40% (w/w) solids from a conditioner. The spiral middlings split was recirculated to lend stability to the system. A wetting agent, Aerosol OT-75, was added at the conditioner to yield a 10 ppm level in solution. The use of a wetting agent was suggested from previous spiral concentration work by Walsh and Kelly, 1992. Spiral concentration data is summarized in Table 2. Spiral tailings were collected in a 1.14 m³ (300 gallon), steel sump, where they were allowed to settle for 16 hours. After settling the water was decanted and the solids were collected in buckets for classification.
Spiral concentrates were upgraded on a laboratory Wilfley table, again in the presence of a wetting agent. Table concentrates were collected and table middlings were recirculated until the table reached equilibrium, after which the middlings were collected separately. Table 3 summarizes Wilfley table concentrate data. Table middlings and tailings were dried, weighed and returned with the classified spiral tailings for batch grinding after stages 1 and 2. Stage 3 table middlings and tailings were analyzed separately.
Wilfley table concentrates were upgraded at the third stage a gravity concentration, a Gemeni table, in the presence of a wetting agent. Table 4 summarizes Gemeni table concentrate data. Gemeni table concentrates were fire assayed in total. The middlings and tailings products were each batch ground for 5 minutes in a laboratory ball mill, then panned to check for the presence of gravity recoverable gold values liberated by additional grinding.

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