Pumpjack
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A pump jack, nodding donkey or horsehead pump is the overground drive for a submersible pump in a borehole.
A pumpjack is usually driven by an electric motor and 'nods' at a regular rhythm. Depending on the size of the submersible pump, it produces 5 to 40 litres of petroleum-water mixture at each stroke. A 2 inch (50 mm) diameter metal rod connects the head to the pump, located underground in the oil reservoir.
The electric motor (or, more rarely, a natural gas or diesel engine ) turns a pair of cranks, which by their action raise and lower one end of the beam. The other end of the beam has a curved end, resulting in the shape likened to a donkey or horse's head. This totally converts the rotary mechanism of the motor to a vertical reciprocating motion to drive the pump shaft. This is what sets up the characteristic nodding motion. The engineering term for this type of mechanism is a walking beam. It was often employed in stationary and marine steam engine designs in the 1700s and 1800s.
This system is also commonly referred to as a beam pump, rod pump, grasshopper, thirsty bird or jack pump. This type of arrangement is commonly used in onshore applications for relatively low-production oil wells.
Pumpjacks are common in many oil-rich areas, dotting the countryside and occasionally serving as local landmarks.
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