3.5.9 Contraction pump

Contraction pump

A contraction pump consists of a special rubber hose which is reinforced in such a way that when it is stretched by means of applying an axial force the diametral contraction is such that the volume is reduced. Pumping effect is acquired by fitting non-return valves to each end of the hose. Suction is achieved as a result of the hose returning to its original length and volume as a result of releasing the axial force.

Efficiency is very good since the only losses, valve losses and hysteresis losses in the rubber, can be reduced to a minimum within the pump’s most suitable operating range. Typical values are 95 percent to 98 percent.

Typical applications are hand operated or motor driven deep-well pumps for well depths of 30 to 100 meters and borehole diameters of 50 to 150 mm. Pump performance depends upon the type of hose. Normally hose stretch is 10 percent of its length and the transported volume is 5 to 20 percent of the internal hose volume. For hand operated pumps the flow volume is within the region of 5 to 20 liters per minute depending upon the depth of the well. A particular advantage is the  simplicity of installation and removal and the single tube, which functions both as a pull-rod and a delivery pipe, resulting in considerable weight and cost savings.

Figure 3.59a Contraction pump shown here as a deep-well pump.