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Positive pumps: according to Tony Peters managing director AxFlow limited peristaltic pumps satisfy many fluid handling applications.

Choosing the pump type that best satisfies a fluid handling application is not necessarily a straightforward exercise, as there will be a large number of factors that will influence pump performance which need to be considered. Not least of these is the type of fluid being pumped.

Whilst there are any numbers of applications that will demand a specific pump type, there will be just as many if not more where a relatively simple low maintenance pump type will suffice. The peristaltic, or hose, pump slots neatly into this category. Suitable for applications where the pumped media can be viscous, of low lubricity or contain solids, the peristaltic pump delivers leak-free operation and high levels of dosing accuracy.

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The main features of the peristaltic pumps include:

* Sealless design

* Valve-free

* Dry self-priming

* Gentle pumping action

* Dry running

* High suction lift

* Abrasion resistant

* Low maintenance

* No slip

* Reversible

The peristaltic pump is a positive displacement pump where the fluid is contained within a hose or tube contained within a casing. The fluid in the hose or tube is moved into and out of the tube/hose by the action of rotating rollers or shoes which alternatively compress and relax the tube/hose. This action forms a vacuum behind the roller or shoe drawing fluid into the hose while the next roller or shoe gently pushes the fluid forward though the hose. This 'peristaltic' process ensures that the fluid is dosed accurately and without any variation in the volume. Pump wear is concentrated on the hose component, which is quick and inexpensive to replace in situ.

Because the fluid is always contained within the tube/hose, it never comes into contact with the pump's moving parts. This has the additional benefit of making the pump suitable for hygienic applications as there is no opportunity for leakage of the fluid and subsequent contamination. Apart from its accurate dosing capability, the peristaltic pump is economic with the liquid pumped because at the end of the processing cycle or operation, the pumping motion can be reversed and any fluid remaining in the hose/tube can be returned to its source for future use and the tube/hose is drained.

Shoes or rollers

The decision to opt for a shoe or roller peristaltic pump is largely dependent on the application and the operating pressures required for the application. Then there is the power consumption issue to be considered. Roller technology is far more suited to lower pressure applications, typically up to 4 bar, and is usually limited to a maximum of 8 bar. Therefore with roller peristaltic pumps smaller drives are required which results in less power being consumed. Roller technology is easier to maintain, with simple hose replacement and less waste fluids due to the elimination of hose lubricant. Shoe compression pumps are more suited for applications demanding for operating pressures up to 16 bar and higher flowrates, making it the obvious choice for medium and higher pressure applications. This pump is very much a robust, workhorse and built for the most arduous of operating conditions and fluids.

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The peristaltic pump is a mature product and a proven technology that has evolved over several decades. Making improvements has, therefore, presented a challenge to pump designers. However, in 2012, AxFlow introduced a new design of roller technology peristaltic pump offering users a combination of low pressure and low capacity. This new pump also addressed the issue of making maintenance easier by a redesign of the inspection window on the pump housing.

Generally, the inspection window of a peristaltic pump enables the operator to check the oil lubricant level in the pump housing. The new design of the inspection window, which is also incorporated in AxFlow's range of shoe compression hose pumps makes it easy for the operator to access the rotor and the hub and easy to change the number of shims in order to accommodate pressure changes demanded by the application. This facility eliminates the need to remove the front cover of the pump case, thereby saving valuable time and making maintenance easier.

Whether the application involves dosing small, precise quantities of fluid at low pressures or high accuracy pumping of large volumes of viscous or abrasive products, peristaltic and hose pumps provide an excellent solution.

Tel: 020 8579 2111
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Title Annotation:PUMPS
Publication:Finishing
Date:Sep 1, 2012
Words:718
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