Hydrocyclones are simple mechanical devices, with out moving parts, designed to speed up the settling process. Feed pressure is transformed into centrifugal force inside the cyclone or cone to accelerate particle settling. In essence, a cyclone is a miniature settling pit which alloys very rapid settling of solids under controlled conditions.
Hydrocyclones have become important in solid control systems because of their ability to efficiently remove particles smaller than the finest mesh screens. They are also uncomplicated devices, which make them easy to use and maintain.
A hydrocyclone consist of a conical shell with a small opening at the bottom for the underflow discharge, a larger opening at the top for liquid discharge through an internal "vortex finder" and a feed nozzle on the side of the body near the wide (top) end of the cone. Drilling mud enters the cyclone under pressure from a centrifugal feed pump. The velocity of the mud causes the particles to rotate rapidly within the main chamber of the cyclone. Light, fine solids and the liquid phase of the mud tend to spiral inward and upward for discharge through the liquid outlet. Heavy, coarse solids and the liquid film around them tend to spiral outward and downward for discharge through the solid outlet or under flow.
Design features of cyclones units vary widely according to the size. The cyclones are made of composite materials and hold up to wear quite well. The size of cyclones in use varies from 12" down to 2". The measurement refers to the inside diameter of the largest, cylinders section of the cyclone. In general, but not always, the larger the cone, the larger the cut point and the greater the thruput. Refer to the figures below:
Cone Size: 4" 5" 10"
Capacity (GPM): 50-75 70-80 400-500
Feed Pressure (PSI): 32-40 32-40 20-30
Cut Point (microns): 15-20 20-25 30-40
Manifolding multiple cyclones in parallel can provide sufficient capacity to handle the required circulating volume plus some reserve as necessary. Manifolding may orient the cyclones in a vertical position or nearly horizontal the choice is one of convenience & system design parameters. The position does not affect cyclone performance. The internal geometry of a cyclone also has a great deal to do with its operating efficiency. The length & angle of the conical section, the size and adjustment means of the underflow opening all play important roles in a cyclones effective separation of solids particles. Operating efficiencies of cyclones may be measured in several ways, but since the purpose of a cyclone is to discard maximum abrasive solids with minimum fluid loss, both aspects must be considered. Hydrocyclones are another important line of defense in the battle against the removal of solids from your drilling fluid.