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A spiral pump , sometimes called a Wirtz pump, is a low lift pump which is composed of a long piece of metal plating, which is wound into a coil and sealed at the top and back extremities so as to resemble a cylinder. The outer cavity serves as the inlet, while the inner (partial) tube serves as the outlet. A coiled plastic tube will suffice for this arrangement. The outlet pipe is fixed to a water wheel, engine or animal which is capable of rotating the pump quickly. Due to this rotation, water is picked up by the outer cavity and pumped upwards in the hose.
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Application
The spiral pump, as many low lift pumps, is commonly used for irrigation purposes and for drainage of lands.
Advantages
The spiral pump is an alternative to the Archimedean screw and it is based on the same principle as the Archimedes' screw, a rotating tube or plane (screw) to move a liquid. Unlike the Archimedean screw, it can pump while horizontal. The Archimedean screw must be tilted at an angle. The spiral pump, if fitted with a suitable rotating seal, can deliver water to a greater height, typically 5-10m, above their discharge opening. Despite the emergence of new pumps that operate on other principles, the spiral pump remains an important tool as it can be built and repaired easily at a very low cost. This is possible as all the components can be built from local resources such as sheet metal bent into the desired form with or without machine tools.
Disadvantages
As mentioned before, the pump only allows the lifting of water over a small height. Such an inhibiting factor makes it unsuitable for use in water drainage or irrigation situations that require water to be lifted over larger heights.
Origins
In a publication by Thomas Ewbank regarding Hydraulics (Hydraulics. 16th ed., 1876. Fig. 165.), Ewbank attributes a drawing of a section of a spiral pump to H. A. Wirtz. It was said that Wirtz may have created the pump in order to provide water for a factory near Zurich. Very little is known about H. A. Wirtz other than he was from Zurich and was a pewterer. It is likely that he knew of the design of other devices such as the Archimedes' screw and the Persian wheel. It has been suggested that owing to his profession, he would have had the know how to create a tubular spiral from metal. Whilst the picture referenced in Ewbank's publication cites a date some time during 1876, it has been said that the device was originally created by H. A. Wirtz in 1746.