What’s a Sand Trap?

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Sand traps remove sand or silt from water pumped from wells and boreholes. They use a cyclonic flow pattern to separate heavier sand particles, making them easier to maintain than filters. There are two types: above ground with a purge valve, and in-well with an automatic flapper valve.

A sand trap is a device used to remove sand or silt from fluid suspensions, typically water pumped from wells and boreholes. Most sand separation devices work by imparting a cyclonic flow pattern into the water that passes through them. This action swirls the heavier sand particles out of the separator, where they deposit in the collection chambers for later removal. This distinguishes the sand trap 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 located in a well.

Many well or borehole environments have sand contamination to one degree or another. This suspended silt is not only undesirable from a sanitary point of view, but also creates damage to parts of pumps, valves, pipes and irrigation systems. The removal of suspended sand from well water can be achieved by using physical filters or by placing a sand trap in line with the pump inlet or outlet piping. Filters are very efficient at removing suspended sand from the water, but are also prone to clogging and require considerable effort to clean and maintain. Furthermore, the elements used as physical barriers in a filter are often very expensive.

The sand trap is a sand removal option that is much easier to operate and requires less maintenance and financial commitment to maintain. These devices use a rotating cyclonic action within their enclosures to impart a centrifugal force to the water flowing through them. Most sand traps are enclosed, cylindrical devices and perform cyclonic action by drawing water into the cylinder through inlet ports located 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 to the suspension causes the heavier sand particles to be thrown out of the tube where they settle and are collected. The clean water is then drawn from the cylinder and into the exhaust pipes. How collected sand is removed from the separator depends on which of the two basic types of device is used. The first of these is the above ground separator, which is generally easy to access. This type of device is equipped with a purge valve at the bottom of the cylinder which allows the sand to be manually discharged from the device at regular intervals.

The second type of sand trap is the in-well or submerged device placed at the bottom of the well or borehole, which obviously is not accessible. These separators feature an automatic flexible flapper valve at the bottom of the separator housing. When a predetermined amount of sand has collected at the bottom of the cylinder, the valve opens automatically and the sand falls to the bottom of the well.

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