Besides the main items mentioned in other tags there are lot of other equipments which are required for operating a mineral processing plant. A brief discussion of these small, auxiliary equipments are made here. Though size and function wise these are small but nonetheless absence of these will definitely make the operation of other major equipments almost impossible. The list of the equipments mentioned here is definitely not an exhaustive one.
Centrifugal Pumps – These are one of the most common items required in a processing plant. The application may range from plain water or fluid pumping to slurry pumping. In some cases these pumps have become the main ore transport medium where ore is sent over cross land pipe lines in the form of slurry. The pumps can be of single or multiple stage type depending on the application requirement. In single stage pumping a vertical lift of 30 meters can be achieved and in some extreme cases it may be up to 100meters. However main disadvantage in centrifugal pumps is high velocity in the impeller chamber, which may result in fast wear of the chamber and impeller due to presence of abrasive particles in the slurry. Technology is also developing to overcome this problem where a coating of Teflon or rubber based compound is applied to the impeller and the chamber to reduce the rate of wear to the metal parts.
Electromagnets – These are hung over conveyor belts to catch pieces of tramp iron and steel. These are generally placed before crushing units to protect the same from overloading and jamming due to foreign pieces. However this may not be very effective in sorting tramp metal from magnetic ores and in case of non magnetic material passing under it.
Metal detectors – These are better option than electromagnets as they measure the electrical conductivity of the ore being carried over conveyor belt. The unit can be mounted over the belt or around the belt. Since the conductivity of ore is much less than any metal piece, any fluctuation in electrical conductivity can be easily measured and belt can be stopped with accompanying alarm signal for removing the piece manually. This type of safety devices can prevent processing equipments specially crushers from major breakdowns and stoppages.
Launders – These are gently sloping troughs of rectangular, triangular or semicircular section, in which the solid is carried in suspension, or by sliding or rolling. This is a form of hydraulically transporting the ore. This type of transportation is better than dry transportation at the grinding stage when most of the process is carried out in wet circuit. The slope of launder depends on particle size, on solid content of the suspension, and on specific gravity of the solid.
Pipelines – This is one of the less obvious components in a process plant; however this also requires equal importance in design and maintenance. The slurry or pulp in most mills is moved through pipelines via centrifugal pumps. Pipelines should be as straight as possible to prevent abrasion at bends. The use of oversize pipe is dangerous whenever slow motion might allow the solids to settle and hence choke the pipe. The factors involved in pipeline design and installation are complex and include the solid-liquid ratio, the average pulp density, the density of the solid constituents, the size analysis and particle shape, and the fluid viscosity.
Feed Chutes – Feed chutes are another critical component in any process plant. These are used in all transit points, i.e. whenever material fall from equipment to belt or vice versa.
While discharging material on the belt chutes must be designed to deliver the bulk of the material to the centre of the belt and at a velocity close to that of the belt. Ideally it should be the same, but in practice this condition is seldom obtained, particularly with wet sand or sticky materials. Where conditions will allow, the angle of the chute should be as great as possible, thereby allowing it to be gradually placed at lesser angles to the belt until the correct speed of flow is obtained. The material, particularly if it is heavy, or lumpy, should never be allowed to strike the belt vertically.
While discharging material to crusher, screen etc. the chute design should be such that material should enter it centrally and evenly otherwise there will be uneven wear of the components resulting abnormal failures. Care should be taken to avoid unnecessary piling up of material in the chute due to sticky material, though a layer of material can help in reducing the wear of chute due to impact of the falling material. Lining material is also available in metal as well as fibre for protection of chute walls, which can be used judiciously.
Tripper – This is an arrangement of pulleys by which the belt is raised and doubled back so as to give it a localized discharge point. This is necessary if material has to be unloaded from belt before the head pulley. It is usually mounted on wheels, running on tracks, so that the load can be delivered at several points, over a long bin or into several bins. The tripper may be moved by hand, by head and tail ropes from a reversible hoisting drum, or by a motor. It may be automatic, moving backwards and forwards under power from the belt drive. The discharge chute on the tripper can deliver to one or both sides of the belt.