A sand separator is a device used to remove sand or silt from fluid suspensions, typically water pumped from boreholes and wells. Most sand separation devices work by imparting a cyclonic flow pattern in the water passing through them. This action spins the heavier sand particles towards the outside of the separator, where it settles in collection chambers for later removal. This sets the sand separator apart from conventional filters and also makes it more reliable and easier to maintain. These devices fall into two basic categories: those located above ground and those situated in a well.
Many borehole or well environments feature sand contamination to one degree or another. This suspended silt is not only undesirable from a health perspective, but also plays havoc with pump parts, valves, piping, and irrigation systems. Removing suspended sand from well water may be achieved using physical filters or by placing a sand separator in line with the pump discharge or suction pipes. Filters are very efficient at removing suspended sand from water, but are also prone to clogging and require considerable effort to clean and maintain. In addition, the elements used as physical barriers in a filter are often very expensive.
The sand separator is a sand removal option far simpler in operation and requiring less maintenance and financial commitment to maintain. These devices make use of a rotary cyclone-like action within their casings to impart a centrifugal force on the water passing through them. Most sand separator units are closed, cylindrical devices and achieve the cyclonic action by drawing water into the cylinder through inlet ports placed at a tangent to their linear axis. This causes the water to rotate in a spiral pattern as it passes through the device.
The centrifugal force imparted on the suspension causes the heavier sand particles to be flung to the outside of the tube where it settles and is collected. The clean water is then drawn out of the cylinder and into the discharge pipes. How the collected sand is removed from the separator depends on which of the two basic types of device are being used. The first of these is the above-ground separator, which is generally easily accessed. This type of device features a purge valve at the bottom of the cylinder allowing the sand to be manually flushed from the device at regular intervals.
The second type of sand separator is the in-well or submerged device located at the bottom of the well or borehole, which is obviously not accessible. These separators feature an automatic, flexible flap valve at the bottom of the separator casing. When a pre-determined amount of sand has collected in the bottom of the cylinder, the valve opens automatically and the sand falls out into the bottom of the well.