Lengthened vibratory feed conveyors for rectangular hopper outlets
Skako Comessa are probably best known for their modular vibratory feeder assembly featuring an inlet hopper section with a square opening, which is bolted directly to a corresponding square hopper outlet. However, where the feed hopper has a rectangular discharge opening, for example 1,000mm wide x 3,000mm long, Skako Comessa can custom design a lengthened vibratory feeding conveyor to suit the exact application.
By utilizing a rectangular-shaped dump hopper, a significantly greater volume of material can be held than in a square unit of similar height. This is particularly relevant for below-ground lorry and rail wagon receiving hoppers, and ‘low-height’ feed loading stations, where it is necessary to feed over the side with a front-end loader. Over the years, Skako Comessa have provided numerous special long vibratory feeders, and in the process have developed an expertise and refined the required design parameters.
The units range from 800–2,000mm in width, and generally from 3,000–6,000mm in length. Operational capacities are usually in the range 300–800 tonnes/h, although units for significantly higher throughputs are easily achievable. To maintain a competitive positioning, the feeders are of heavy-duty ribbed and welded construction, with replaceable base and side liner plates, and are driven by twin unbalanced motors. By the inclusion of an electrical frequency inverter, infinitely variable feed rate control can be achieved between approximately 30–100% of the preset maximum. Additionally, as the drives do not need to be tuned to the feeder weight, and are not affected by varying head loads, they are suitable for handling differing materials, including those with fines and inherent moisture content (such as sub-base materials).
Owing to the design of the rectangular dump hopper discharge opening, the vibratory feeder can be subjected to varying loads. However, this can be easily countered by the inclusion of a ‘breaker plate’ in the hopper and special spring and support arrangements on the feeder, including captive helical springs, rubber ‘bump stops’ and damper cylinders. These measures successfully mitigate damaging dynamic shock loads and ensure that the feeder reliability is maintained for many years.
Recently, Skako Comessa have replaced a number of belt feeders (located under rectangular-shaped hoppers) with custom-designed vibratory units. The replacement vibratory feeders are considerably more robust and virtually maintenance-free in comparison. Additionally, the inherent spillage problems of belt feeders have been eliminated.
The accompanying photo shows how Skako Comessa solved an operational problem at a quarry site earlier this year, by utilizing an 1,100mm wide x 4,300mm long vibratory feeding conveyor. Handling –250mm primary crushed granite, and fed by a belt conveyor, the original hopper had a restricted opening at the bottom to suit the existing feeder preceding an impactor, resulting in considerable dead zones and a very limited live area. By utilizing a longer feeder, the discharge opening of the hopper was extended back into the previous dead zone, creating a rectangular outlet and, in the process, significantly increasing the live area. At the same time, the feed rate to the impactor was uprated, thereby increasing operational productivity.
For further information, contact Skako Comessa Ltd on tel: (01937) 838010; fax: (01937) 838011.