A hydrocyclone much like a desander except that its design incorporates a greater number of smaller cones. As with the desander, its purpose is to remove unwanted solids from the mud system. The smaller cones allow the desilter to efficiently remove smaller diameter drill solids than a desander does.
A desilter uses smaller hydrocyclones (usually 4″ or 5″ I.D.) than a desander and therefore, generally removes smaller particles. The smaller cones enable a desilter to make the finest particle size separation of any full flow solids control equipment—removing solids in the range of 15μm and larger. This makes it an important device for reducing average particle sizes and removing abrasive grit from unweighted drilling fluids.
The cyclones in desilter units operate on the same principle as the cyclones used as desanders. They simply make a finer cut and the individual cone throughput capacities are less than desander cones. Multiple cones are usually manifolded in a single desilter unit to meet throughput requirements. Desilters should be sized to process 100%–125% of the flow rate entering the suction tank for the desilters. (Note that this does not say 100%–125% of the flow rate down the hole.)
Installation of the desilters is normally downstream from the shale shaker, degasser, and desander and should allow ample space for maintenance
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