30 Mar The Use of Spindle Pumps
The Use of Spindle Pumps in Ancient and Modern Times
Aptly named, due to its long and relatively narrow design, the vertical spindle pump may be a present-day device, but its origins are buried deep in ancient history. During a visit to Egypt in around 234 BC, the Greek mathematician, engineer and inventor, Archimedes observed a rotating helical device used by locals to raise water from the river Nile. Some authorities have suggested that bronze water screws, cast 350 years earlier, may have been the irrigation mechanism used to sustain the famed Hanging Gardens of Babylon.
When introduced to Greece, the device later became known as an Archimedes Screw. It was the first positive displacement pump and a distant forerunner of the spindle pumps in widespread use today. Based on the design of its central component, the modern device is often known alternatively as a screw pump. Interestingly, that main component shares one of the properties of a conventional impeller. While it can be driven by a motor to transport liquids, its design also allows it to be driven by water and thus operate a generator. When operating in this fashion, it is known as a screw turbine.
Unlike those used to aerate fish tanks, power garden fountains, or draw water from a borehole, vertical spindle pumps are only semi-submersible devices. The other types mentioned above are designed to contain the motor and all moving parts within a single water-tight housing. This means their power must be supplied from the surface by suitably sealed electrical cables.
By contrast, only the inlet and screw-like component are located beneath the liquid surface in these semi-submersible units. The motive power to the screw is still provided by an electric motor or an internal combustion engine. However, the latter will be mounted well above the surface of the liquid, at the end of a long driveshaft or spindle from which these pumps derive their name.
These are sealless units that rely on a close fit between the screw-like impeller and the cylinder wall within which it rotates to minimise any tendency for the pumped fluids to drain backwards between the two. While a well-built unit will be able to transport clean or dirty water without significant leakage, one of these units’ greatest strengths lies in the ability to handle more viscous liquids such as crude oil and slurries. As well as being far less prone to leakage, when spindle pumps are used to transport a viscous fluid, the latter can act as a form of self-lubrication, thus helping to reduce some of the natural wear and tear and operating noise.
In practice, these units are of particularly robust construction and will generally display a correspondingly long working lifespan. Furthermore, they have several other significant benefits. For a start, although it will invariably be possible to perform most of the same tasks when employing a suitable submersible unit, these are bulky and require a fixed installation. Consequently, unlike the readily portable spindle pumps, it is not such a simple matter to relocate a previously installed submersible unit for use elsewhere. The vertical shaft-driven model will be the unit of choices where there may be an occasional need to conduct a drainage operation at another site.
Among the other benefits referred to earlier, one of the most useful is versatility. The same unit can be used for a wide range of tasks, including dewatering, and clearing accidental spills. Also, because of its simple design and inherent efficiency, a spindle pump will typically consume less electricity or fossil fuel than alternative types of pumping equipment. Not only are they cheaper to run, but this advantage also makes them a tool of choice for a company that has committed to lowering its carbon footprint.
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Often there will be a need for a portable unit capable of handling corrosive liquids such as strong acids and alkalis. For such cases, there are models made from stainless steel, titanium, or superalloys such as Hastelloy. However, these materials are not only more expensive than bronze or cast iron; they are also very heavy. For something lighter with greater resistance to corrosive and abrasive materials, spindle pumps in which all wettable parts are made from lightweight, thermosetting resins are also available. For more about these and other world-class pumping equipment, talk to an expert at Prochem Chemical Pump Manufacturers.