Hand pump

Hand pumps are manually operated pumps; they use human power and mechanical advantage to move fluids or air from one place to another. They are widely used in every country in the world for a variety of industrial, marine, irrigation and leisure activities. There are many different types of hand pump available, mainly operating on a piston, diaphragm or rotary vane principle with a check valve on the entry and exit ports to the chamber operating in opposing directions. Most hand pumps are either piston pumps or plunger pumps, and are positive displacement. Hand pumps are commonly used in developing countries for both community supply and self-supply of water and can be installed on boreholes or hand-dug wells.

History

One sort of pump once common worldwide was a hand-powered water pump, or 'pitcher pump'. It was commonly installed over community water wells in the days before piped water supplies. In parts of Britain and Ireland, it was often called the parish pump. Though such community pumps are no longer common, people still used the expression parish pump to describe a place or forum where matters of local interest are discussed, or parish pump politics for politics which prioritizes local issues. Because water from pitcher pumps is drawn directly from the soil, it is more prone to contamination. If such water is not filtered and purified, consumption of it might lead to gastrointestinal or other water-borne diseases. A notorious case is the 1854 Broad Street cholera outbreak. At the time it was not known how cholera was transmitted, but physician John Snow suspected contaminated water and had the handle of the public pump he suspected removed; the outbreak then subsided. Modern hand-operated community pumps are considered the most sustainable low-cost option for safe water supply in resource-poor settings, often in rural areas in developing countries. A hand pump opens access to deeper groundwater that is often not polluted and also improves the safety of a well by protecting the water source from contaminated buckets. Pumps such as the Afridev pump are designed to be cheap to build and install, and easy to maintain with simple parts. However, scarcity of spare parts for these types of pumps in some regions of Africa has diminished their utility for these areas.

Types

Suction and lift hand pumps Suction and lift are important considerations when pumping fluids. Suction is the vertical distance between the fluid to be pumped and the centre of the pump, while lift is the vertical distance between the pump and the delivery point. The depth from which a hand pump will suck is limited by atmospheric pressure to less than seven meters. The height to which a hand pump will lift is governed by the ability of the pump and the operator to lift the weight in the delivery pipe. Thus the same pump and operator will be able to achieve a greater lift with a smaller-diameter pipe than they could with a larger-diameter pipe. In addition to their use in drawing water from shallow groundwater sources for water supplies, another version of the hand-powered suction pump, with low lift and high delivery, was developed in the later 19th century for use as a ship's bilge pump (for smaller coastal vessels) and as a building site contractor's pump. It was known as a deluge pump. One manufacturer who illustrated this product from the late 1880s onwards into the early 20th century was Goulds Manufacturing Co.

Force Pump Where it is necessary to raise water to a height above that to which a suction or lift pump will operate effectively (about seven metres), or to raise the pressure so that it will exit a nozzle with a strong force, such as through a fire hose, a force pump may be used. As with a suction pump, in its manual form it relies on an operator to pump a handle. The difference is, however, that after the water is sucked through the lower valve (as a result of raising the piston that is attached to the handle), its means of exit is via a pipe or nozzle in the side of the main cylinder. The water, once it has been drawn up above the lower valve and trapped there, is forced out the exit when the piston or plunger is pushed down again on the next stroke.

Siphon A siphon (or syphon) at its simplest is a bent tube with one end placed in the water to be moved and the other end into the vessel to receive the water. The receiving vessel must be at a lower level than the supplying vessel. Water will always try to find its lowest level. Using this principle, very simple bulb pumps, with flap valves at each end, are used for emptying fuel or water cans into tanks. Once the liquid fills enough of the tube the fluid will flow without further effort from the higher to the lower container. Many hand pumps will allow the passage of fluid through them in the direction of flow and diaphragm pumps are particularly good at this. Thus where the levels are correct large volumes of liquid, such as in swimming pools, can be emptied with very little effort and no expensive energy use.

Chain pump A chain pump is made of an endless chain carrying a series of discs that descend into the water, and then ascend inside a tube, carrying with them a large quantity of water. They are a simply made, old hand-powered pumping technology In the 18th century they were used as ship's bilge pumps. A chain pump is a type of water pump that uses a chain to move water from one place to another. It works on the principle of a continuous loop of chain moving through a series of sprockets, with attached buckets that lift water as the chain passes over the top sprocket and discharge it as the chain reaches the bottom.

Direct action Direct action hand pumps have a pumping rod that is moved up and down, directly by the user, discharging water. Direct action handpumps are easy to install and maintain but are limited to the maximum column of water a person can physically lift of up to 15 m. Examples of direct action pumps include the canzee pump and the EMAS pump.

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