Abstract: A method and apparatus for monitoring density fluctuations in a spiralling flow within a hydrocyclone. The invention involves the use of a nuclear density gauge which directs a beam of radiation asymmetrically across the hydrocyclone away from the centrally located air column. This air column within the hydrocyclone is created by the spiralling or cyclonic action of the flow and exists when the hydrocyclone is in operation. In a preferred embodiment, the flow is particulate solids in a carrier liquid such as water which has a substantially constant specific gravity so that the fluctuations in the intensity of the radiation received at the detector are inversely proportional to the amount of particulate solids in the flow. In one embodiment, the radiation is directed along a path substantially perpendicular to the axis of symmetry of the hydrocyclone and in another embodiment, the radiation is directed along a path at an inclined angle to the axis.

Abstract: A valve assembly for controlling the flow of material in a duct such as a pipeline, outlet of a cyclone, nozzle and the like. The assembly is particularly suitable for controlling spiralling flows and includes a plurality of elongated valve members pivotally mounted at a first end to a support. Each valve member has at least two elongated and substantially planar sides extending from the first end to a second end. The two planar sides are joined to form a leading edge. The valve members are supported in an overlapping relationship and a mechanism closes the valve assembly by moving the second ends of the valve members toward each other. As the valve assembly closes, the leading edge of each valve member pivots about an axis and moves in a path along a plane extending radially from the axis of the valve assembly.