Abstract: A process for controlling a variable in respect of material in a series of interconnected vessels of a plant includes monitoring a variable in respect of each vessel. The monitored value of the variable is compared with a set point value of the variable. The differences between the monitored values and set point values of the variable resulting from at least one disturbance are summed. When such a disturbance in any one vessel results in a signal representative of the summed value being generated, each of a plurality of actuators of the plant are manipulated in a predetermined direction from the one vessel to cause rapid reduction of the disturbance. The invention extends to a control system for controlling a variable in respect of material in a series of interconnected vessels of a plant.

Abstract: A method and means for measuring a characteristic, in particular one associated with particle size, of any of the feed, underflow or overflow streams of a hydrocyclone is provided. Information as to the flowrate and density of the feed stream as well as the angle of flare or other related variable associated with the shape of the underflow stream are fed to processing means which applies a formula or algorithm, which is usually empirically derived, to such information to provide a value of the required characteristic. The characteristic may be related to particle size, particle size distribution in any of the streams or the liquid content or the flowrates of solids or liquids in the underflow or overflow. Measurement apparatus comprising a dedicated hydrocyclone is also provided.

Abstract: A method is disclosed of controlling the operation of a hydro-cyclone or a circuit embodying same. The method involves the measurement of a variable associated with the shape of the slurry underflow emanating from the hydro-cyclone outlet. The variable is generally the cone angle or, in effect, the radius or diameter of the conical shaped stream of slurry flowing from the outlet at a selected position below the outlet and this diameter can be measured using an arm or arms which operatively rides on the outer boundary of the slurry underflow stream.