Industrial “heart”
A pump is a device used to move fluids, such as liquids or slurries. A pump displaces a volume by physical or mechanical action. Pumps fall into five major groups: direct lift, displacement, velocity, buoyancy and gravity pumps. Their names describe the method for moving a fluid. Pump can be simply divided into several catalogs, such as, positive displacement pumps, buoyancy pump, impulse pumps, velocity pumps, gravity pumps, steam pumps and so on.
Pumps are used throughout society for a variety of purposes. Early applications include the use of the windmill or watermill to pump water. Today, the pump is used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewage movement, flood control, marine services, etc. Because of the wide variety of applications, pumps have a plethora of shapes and sizes: from very large to very small, from handling gas to handling liquid, from high pressure to low pressure, and from high volume to low volume.
One sort of pump once common worldwide was a hand-powered water pump over a water well where people could work it to extract water, before most houses had individual water supplies.
From this came the expression “parish pump” for “the sort of matter chattered about by people when they meet when they go to get water”, “matter of only local interest”. However water from pitcher pumps are more prone to contamination since it is drawn directly from the soil and does not undergo filtration, this might cause gastrointestinal related diseases.
Today, hand operated village 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 like 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 type of pumps in some regions of Africa has diminished their utility for these areas.
Finally, let’s talk about pump efficiency. Pump efficiency is defined as the ratio of the power imparted on the fluid by the pump in relation to the power supplied to drive the pump. Its value is not fixed for a given pump, efficiency is a function of the discharge and therefore also operating head. For centrifugal pumps, the efficiency tends to increase with flow rate up to a point midway through the operating range (peak efficiency) and then declines as flow rates rise further. Pump performance data such as this is usually supplied by the manufacturer before pump selection. Pump efficiencies tend to decline over time due to wear (e.g. increasing clearances as impellers reduce in size).
One important part of system design involves matching the pipeline headloss-flow characteristic with the appropriate pump or pumps which will operate at or close to the point of maximum efficiency. There are free tools that help calculate head needed and show pump curves including their Best Efficiency Points (BEP).
Pump efficiency is an important aspect and pumps should be regularly tested. Thermodynamic pump testing is one method.
