Advances in the Theory and Practice of Hydrocyclone Technique
With numerical simulation of hydrocyclone separation based on the Navier-Stokes and mass transfer equations, it is possible to perform hydrocyclone experiments on a computer. With the help of computational engineering, the cost of conducting hydrocyclone experiments in the planning phase of new hydrocyclone units can be cut drastically. The simulation models also enable a deeper insight into the static and dynamic process behaviour in hydrocyclones. It is shown that the solids stored in the hydrocyclone represents a sensitive process variable for separation in the hydrocyclone. On this basis, a new control concept for a hydrocyclone battery has been developed. As the solids concentration in the feed increases, the combined overflow of all the hydrocyclones in the battery is throttled. At the same time, the feed pump speed is increased. In this way, while the total throughput remains constant, the volume split changes to effect that more solid material is discharged in the hydrocyclone underflow. This computer-based process control system is ideally suited for hydrocyclones in separation plants for tunnel driving projects as well as for those integrated closed-circuit grinding
Mechatronik für eine Hydrozyklonbatterie
Hydrocyclones are sensitive to variations in the solid concentration and the particle size composition of the feed material. This problem can be solved by a mechatronic control of the hydrocyclone. The elements of this control system comprise sensors for measuring the operating state, a process control computer for recording and processing the measured data and the actuator, in this case a valve at the overflow receiver tank of the hydrocyclone battery. With this system, the hydrocyclone can be operated at the optimum operating point, the transition from strand to fan discharge. Les hydrocyclones sont sensibles aux variations de la concentration de solides et de la composition granulometrique de la matiere d'alimentation. Ce probleme peut etre resolu moyennant le reglage mecatronique de l'hydrocyclone. Les elements de ce reglage sont les capteurs destines a mesurer l'etat de service, un ordinateur de processus destine a l'enregistrement et au traitement des valeurs mesurees ainsi que l'element de reglage, constitue, dans le cas present, par une valve se trouvant sur le collecteur de la surverse de la batterie d'hydrocyclones. De cette maniere, l'hydrocyclone peut travailler a son point de service optimal, c'est-a-dire au point de transition entre la decharge sous forme de boudin et la decharge sous forme de parapluie.
Traceability strategy for gear-pitch-measuring instruments: development and calibration of a multiball artifact
There is a strong demand to ensure the traceability of gear-measuring instruments (GMIs). We propose a multiball artifact (MBA) for the evaluation of pitch-measuring accuracy. The aim of the MBA is to transfer the minimum uncertainty from a calibrated value at the National Metrology Institute of Japan (NMIJ) to a measured value of GMIs at a shop floor. The MBA is composed of equally spaced high-accuracy balls around an axis. The pitch-measuring accuracy of GMIs is evaluated by measuring the angular pitch deviation of the balls instead of the angular pitch deviation of a gear. We calibrated the angular pitch deviation using a coordinate measuring instrument (CMM) at the NMIJ and adapting a multiple-orientation technique. We proposed a calibration strategy of the angular pitch deviation. The calibration value of the pitch deviation for the MBA at the NMIJ was obtained with a measurement uncertainty (U95) of 0.2 µm. We evaluated the pitch-measuring accuracy of a GMI using the calibrated MBA. Each value of U95 for the cumulative and single pitch deviations for the left and right flanks was less than or equal to 0.5 µm. The small uncertainty was transferred from the NMIJ to the GMI.