Pumps are among the most important and widespread machines built and used by people all around the world. They are used to transport liquids, gases or compounds or to increase pressure and overcome height differences and physical distances.
Peristaltic tube pumps are positive displacement pumps and at Spetec, they are made up of a roller head driven directly by a wear-resistant stepper motor and an arrangement for securing the tubing used. This type of pump operates on the principle of constantly compressing and releasing a tubing. The tubing is pressed into holders around a rotating roller head using pressure arms. The liquid is thus conveyed along the occlusion point of the tubing by an alternating surface of the roller head caused by the rollers and their movement.
The first tube pumps were initially used to pump blood in the 1960s. They soon found their way into industrial applications as self-priming pumps of this kind are very easy to use and are also suitable for abrasive or viscous media. In common with all tube pumps, designs with a pump head – initially often with just two rollers – exhibit considerable pulsation.
Where a constant flow was required for an application, it was necessary to increase the number of rollers to eliminate the pulsating interruptions. Another essential element in achieving this characteristic is suitable tubing material which retains its elasticity for as long as possible and which is resistant against different liquids.
Tube pumps from Spetec use 6 to 16 pressure rollers. The figures show two types with different numbers of rollers as OEM versions. One special feature is that they are custom-produced in terms of performance, size and color. Because all the component parts are produced in-house, it is also possible to meet special requirements. The concept pursued by Spetec gmbH is to provide pumps that not only feature excellent technical properties such as extremely low pulsation, high precision and a stable flow rate, but which also have their own attractive, individual appearance. There are no traditional production models. Instead just some of the basic components, such as the roller head, the tube holders and the pressure arms, are reused. But the visual appearance can always be adapted to customer requirements. For instance, the color and shape of the base plate on which the actual pump is mounted and other components can be custom built. This results in a personalized product that carries the “signature” of the device manufacturer. And smaller pumps have also been designed to take account of the trend towards more compact analysis equipment.
The Perimax is a standalone version of the tube pump. This pump contains 12 or 16 rollers per pump head and can be supplied with up to 6 channels. The Perimax 12 delivers a flow rate of up to 20 ml/min. The Perimax 16 achieves double this flow rate by splitting and phase-shifting the 16 rollers, thus allowing the use of dual tubing. Phase-shifting also leads to virtually pulsation-free delivery.
Peristaltic pumps are frequently used in instrumental analysis, ICP spectrometry and atomic absorption spectroscopy (AAS). Other fields of application extend to areas such as medical engineering, the pharmaceuticals industry and the foodstuffs industry.
Extensive automation of the processes in chemical analysis labs requires the use of pumps suitable for delivering a constant flow of sample solutions, for instance in systems carrying out water analysis and environmental analyses. And the partially automated processes in ion chromatography demand the use of high-precision tube pumps.
Most emission spectrometers for the direct analysis of solutions, such as those using ICP excitation, nowadays contain tube pumps such as these. Particularly in the context of the plasma flame, it is important that there is virtually no pulsation, as the plasma tends to induce pulsating movement.
The advantages of using tube pumps are that they are closed systems, that they are easily sterilized and that delivery is gentle, with the result that unstable components in solutions, such as blood cells, are not destroyed.
Other advantages of tube pumps include the ability to pump slurried and higher-viscosity fluids. To do this, pump tubing is needed.
For many years, Spetec has been manufacturing tubing in-house and offers a wide range of tubing materials. Depending on the medium being pumped, the tubing is manufactured from different mate-rials and recommended for different applications:
PVC Standard suitable for medical products, ETO sterilization; meets USP Class VI,
Polyurethane (ATB Medical Grade) suitable for medical products, γ sterilization, meets USP Class VI,
Solvent Flex (solvent-resistant) suitable for gasoline, oils; RoHS and REACH compliant,
Santoprene® for non-fatty foodstuffs, meets NFU Standard 51 (no medical products),
Silicone (MF 160U) for technical products as per ISO 10993 and
Fluorinated rubber (comparable with Viton®) high thermostability; RoHS and REACH compliant.
A data sheet is available for each of the materials and can be obtained on request. All tubing is available in a variety of configurations. On request, bridges can be fitted at different intervals to suit the application scenario. The internal diameters of the tubing range between 0.12 mm and 3.2 mm.
The metering capacity of tube pumps is restricted to the milliliter range. Some manufacturers therefore offer syringe pumps that are used for microfluidic methods in analysis labs, for instance.
And Spetec gmbH has also developed a syringe pump with special characteristics. The use of a stepper motor drive made it possible to achieve the high resolution of 25,600 steps per revolution. This permits metering volumes in the range of microliters and nanoliters, which is particularly important in research in medical and analytical labs.
Direct displacement and the high step resolution allow the volume of the medium to be maintained with a precision of ±1 %. The precision of the flow rate remains at a constant high level, so that in this respect also these syringe pumps are unmatched in terms of metering tiny volumes: No better technology exists at present. As is the case with tube pumps, the medium does not come into contact with any mechanical parts of the pump. The syringe is easily replaced, so it is quick to switch between different solutions. Unlike tube pumps, a syringe is able to pump in both directions, i.e. infusing or withdrawing.
