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A pump is any device that is used to move gases or liquids, usually from a low place to a higher one. Many pumps require an external power source to operate, but hydraulic pumps need no external power source. In a hydraulic pump, the water or other fluid is put to work to pump itself. In other words, the water’s kinetic energy is the power that operates a hydraulic pump.
When this type of pump operates, a portion of the water is lifted to a point higher than where the water originally started. In addition, the water that exits the pump is moving at a different rate than the input water. This happens as a result of a phenomenon called stagnation pressure. Stagnation pressure is based on Bernoulli’s principle, which states that an increase in the speed of a fluid happens simultaneously with a decrease in the fluid’s pressure. This principle is what the operation of a hydraulic pump is based on.
A simple hydraulic pump starts out with a pipe that brings the water from the source. At the very end of the pipe is a valve, called the waste valve. When under pressure, the waste valve closes, backing up water pressure against another valve further back, called the delivery check valve. This valve leads to the outlet or delivery pipe. When water pressure in the delivery pipe falls, the delivery check valve closes, allowing pressure to build against the waste valve once more.
This cycle usually repeats every one to two seconds. The process is made more efficient by the addition of a device called a pressure vessel between the delivery check valve and the outlet of the delivery pipe. A pressure vessel is a small metal tank that has a portion of air in it. The air acts as a cushion from the stresses of rapid pressure changes inside the pump, also helping prolong the life of the pump itself.
The hydraulic pump has been in use for centuries, but began to fall out of favor when electricity and electric pumps became widely available. More recently, though, there has been a renewed interest in the hydraulic pump as a way to bring clean water to rural areas of developing countries. Hydraulic pumps are simple enough to be maintained by even the most remote villages. They also provide the advantage of bringing up deep sources of groundwater that are less likely to be contaminated. Water sanitation and availability are constant concerns in developing countries, and the hydraulic pump helps to ease both of these problems.