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How Peristaltic Pumps Work

Problem: The basic purpose of a peristaltic pump is to move fluids from A to B. This is not enough for manufacturers of analysis equipment and manufacturers of sensitive devices.

by Spetec
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Alongside the technical characteristics such as pulsation, accuracy, and stability, they want their pumps to have their own attractive, individual appearance.

Solution: Spetec has been designing and building peristaltic-pumps for an enormous range of applications. It also manufactures the required tubing, which must be as inert as possible in contact with solvents or acids and should have a long service life.

Applications in these fields demand precision metering, an extremely stable technical process flow and, depending on the intended use, the lowest possible level of pulsation. These are the criteria underpinning the design of the two laboratory pump variants Perimax12 (Figure 1) and Perimax16, which differ only in the number of rollers (12/16) in the pump head and the continuously adjustable flow rates they can achieve (0.0017 mL/ min to 20 mL/min against 0.0034 mL/min to 40 mL/min). The 16-roller pump produces no measurable pulsation.

Pumps such as those provided by Spetec have proven their value for instrumental analyses and are also used in the fields of biotechnology and bio-analytics, as well as in liquid and column chromatography applications, inductively coupled plasma emission spectrometry (ICP) and atomic absorption spectrometry (AAS). One reason for this is the ease of use of the pumps. The tube is guided around the pump head and its two ends are fixed to a special mechanism. The compression level can be set using the adjusting screw at the adjusting lever. The pump is switched on and off and the direction of rotation (left or right) is selected using push buttons. The speed of rotation of the pump head is continuously adjustable using a 10-turn potentiometer.

The drive unit used in the two pumps is identical. A stepper motor ensures constant fluid transport. Analog control (0-5 V) of the pump speed and operating direction is possible via a connector on the rear.

One advantage of Spetec’s peristaltic-pumps in particular is that they are not manufactured as a series. Only a small number of basic components are identical, such as the roller heads, pressure brackets or tube holders, all of which are manufactured in large quantities to help minimize cost. Because these pumps are constructed for use in another manufacturer’s end products, this means that each pump is developed to meet the customer’s requirements in terms of visual design. This applies to the color and geometry of the baseplate on which the 1- to 4-channel pump is fitted, as well as to the basic components whose coloring is also harmonized with the device in which the pump is to be installed. This ensures fidelity to the design of the OEM equipment. Designed to customer requirements, the baseplate can be fitted directly to the housing of the analysis unit as a complete assembly or can be integrated in the device construction. This means that the custom-built peristaltic-pumps can be installed more easily and economically during final assembly of analysis units. There are consequently many different variants, which can already be seen in the various brochures, and new designs are being added all the time. The Spetec concept not only takes account of the individual requirements placed on its peristaltic-pumps but also gives them their own specific, attractive appearance.

In all the models, the drive unit is constructed using a stepper motor, with the aim of achieving the greatest possible stability in terms of pump speed and flow rate, as well as the lowest possible pulsation level.

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