A rope pump is a simple water pump used in developing countries for potable water and sanitation projects. It consists of a rope threaded through PVC tubing with washers or knots. The design is in the public domain, but improvements can increase effectiveness. The pump can be powered by hand, motor, wind, or animals and can achieve 80-85% efficiency.
A rope pump is a type of water pump often used in developing countries to provide potable water and assist in sanitation projects. The simple device consists of a heavy rope threaded through polyvinyl chloride (PVC) tubing. The rope is either knotted or has washer-like devices fixed at about 20cm intervals. One end of the tube is submerged and the string is pulled through, kicking up the water. Rope pumps can be powered by hand, motor, wind or animals.
The technology involved in a rope pump is simple and the design is in the public domain. A functional form of pump can be fashioned from a number of items that are widely and readily available. However, there are design recommendations that greatly improve the effectiveness of a rope pump for a modest increase in cost.
The pumping elements are the rope and its washers or pistons. Typically, the rope used is polypropylene fiber. It passes through a hole in the center of a piston and the piston is secured with a knot immediately below and above it. The size of the pistons is determined by the diameter of the PVC pipe used, which in turn is determined by the depth of the well. The diameter of the pipe is inversely proportional to the depth of the well.
Since standard size PVC pipe is used for all applicable well depths, the various piston sizes can be manufactured in advance and in quantity. After passing the rope and its connected pistons through the tube, the ends of the rope are twisted together to form an endless chain. The submerged end of the tube rests in a guide which ensures proper entry of the pistons into the tube and helps maintain sufficient tension on the rope. At the head of the shaft, the rope passes over a pulley which is attached to a support structure on the shaft cover.
The wheel assembly can be configured to operate with a hand crank or be motor driven. When the wheel is turned and the tube fills with water, the pumping action begins. The weight of the water in the tube is distributed downwards with equal pressure on each of the pistons. Each individual piston pushes the water upwards.
Inherent in the rope pump design is a loss of efficiency due to friction and water leakage. However, a properly designed and built rope pump can achieve 80-85% efficiency. Operated by one person, it can pump approximately 10 gallons (38 L) of water per minute from a depth of 33 feet (10 m). A rope pump can be installed for a small fraction of the price of a traditional water pump.
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