A coil pump is a low-cost and simple pump that uses a rotating coil of hollow tubes partially submerged in fluid. It operates horizontally and requires minimal energy to operate, making it ideal for rural agricultural irrigation. It was developed as an alternative to Archimedean screw pumps and is easy to build and maintain with cheap materials. The pump is partially immersed in fluid, and as it rotates, fluid is collected and forced through the coil. Its design reliability and low cost make it an ideal option for developing countries.
A coil pump is a simple and inexpensive pump consisting of a rotating coil of hollow tubes partially immersed in a fluid. One end of the coil is left open at the outer diameter of the coil, with the other end folded towards the center of the coil and exiting in a straight line with the axis of the coil. This end of the coil has a rotating seal which presses against the pump outlet pipe. As the spool rotates, the open end collects fluid each time it dips into the body of fluid, with the twisting action moving the fluid through the spool and out of the discharge tube. While these pumps are only capable of delivering low heads, they are extremely cost effective and require minimal energy to operate, making them ideal for rural agricultural irrigation applications.
Originally developed as an alternative to the Archimedean screw pumps used in many developing countries to irrigate crops, the coil pump offered the benefit of horizontal operation with equal or better head capabilities. The auger must operate at about 30° with respect to the horizontal, requiring very specific profiles of the ground floor of the place of installation. The inclined layout of these pumps also reduces the number of convenient actuation options possible. The coil pump, on the other hand, operates horizontally, allowing the pump to be installed on the same plane as the fluid body and not on a slope. It’s also easy to build and maintain with cheap, easily accessible materials and requires minimal effort to drive.
A basic scroll pump consists of a coil of tubing, typically a flexible PVC pipe, supported on one end by a drive disc. The end of the tube adjacent to the drive disc is left open at the outside diameter of the reel. The opposite end is bent at right angles towards the center of the coil, and then at right angles again to exit along the axis of the coil. This allows this end of the coil to rotate around its axis in a static position. It features a seal that rotates against the pump delivery pipe, forming a tight seal between the pump and the delivery circuit.
The entire coil is partially immersed in a fluid body, usually a lake, pond or river. As the coil rotates, the open end dips below the fluid surface at regular intervals, collecting an amount of fluid with each pass. This fluid is then forced through the coil by rotational forces, finally passing through the sealed end and out into the waste loop. While the coil pump may not achieve impressive head ratings, its design reliability, low cost, and ease of maintenance make it an ideal option for irrigation and general rural pumping for developing countries.
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