One of the most critical issues when designing a slurry system is sedimentation of solid particles in pipelines and pumps. In pipelines, sedimentation will occur when the transportation velocity of a slurry through the pipe is below the deposition velocity. As soon as particles are settled, there is a considerable risk that, in time, a plug will be created which will block the pipeline completely. Settling of solids can, however, also be detrimental for piston diaphragm pumps; large and heavy solids may settle within the diaphragm housing, on top of the suction valves. This layer of solids will cause diaphragms to rupture. In addition, there is a risk that the settling particles may block the valve, causing pressure surges and further damage to the downstream equipment. In order to determine the settling behaviour of a slurry, costly and time-consuming loop tests need to be executed in specialised laboratories for which large quantities of solids are required. This test may also be an indication of the settling behaviour of solids within a piston diaphragm pump, but would not be very accurate, leaving risk of damage to diaphragms. Therefore, a simple, quick and inexpensive test (SE: sedimentation detection system with evaluation algorithm) was developed which indicates if a slurry is prone to settling or not, by determining how fast solids will settle within a diaphragm housing. For this test, just a few kilograms of solids are required, and the result of the test is known within a very short period of time. In principle, the test is based on the measurement of the speed at which particles settle on a scale; the faster the particles settle, the higher the risk of a settled pipeline and the higher the transportation velocity needs to be. This paper will describe the methodology of this test, its results and interpretation. Also, a technology will be presented which prevents settling of solids within the diaphragm housing of piston diaphragm pumps.
?To explore the spatial strength distribution of backfill in the stope, a group of experiments in a large similar stope model was designed for simulating the consolidation of cemented tailings backfill (CTB) in a stope. The height of CTB in similar stope model was measured to analyse the flow and sedimentation characteristics. The unconfined compressive strength (UCS) test on specimens cored in the different position of CTB sample in similar stope model was conducted. Moreover, the particle size and cement content of CTB sample were tested to help to explain the mechanism. The results show that during the flow and sedimentation of filling slurry in the model, inconsistency of the particle size and cement content leads to the inconsistency of strength. In the flow direction (horizontal direction), the median particle size of CTB first increases and then decreases, the cement content of CTB decreases slowly and then increases sharply, and the strength of CTB first decreases and then rises. In the sedimentation direction (vertical direction), the cement content of CTB decreases with the increase of depth, while the strength of CTB increases with the increase of depth. The strength is affected by the interaction between particle size and cement content, and the higher cement content of CTB does not translate into higher strength. The results provide a theoretical basis for improving the quality of CTB and optimizing the design.