Pumpjack
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- “Nodding donkey” redirects here. For the train, see British Rail "Pacer".
A pump jack, nodding donkey, pumping unit, or horsehead pump is the overground drive for a submersible pump in a borehole. It is used to mechanically lift liquid out of the well if there is not enough bottom hole pressure for the liquid to flow all the way to the surface.
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 string of steel (or occasionally fiberglass) rod connects the head to the pump, located at the bottom of the well at an oil producing reservoir.
An 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 converts the rotary mechanism of the motor to a vertical reciprocating motion to drive the pump shaft, and is exhibited in 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.
[edit] See also
[edit] External links
- All Pumped Up : Evolution of Oilfield Technology, The American Oil & Gas Historical Society, Vol. 3, No. 3, September 2006
