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30 PROCESSING TECHNOLOGY


Owing to their diaphragm operation, rocker valves can process very small volumes and are easy to rinse. Tis has made them first choice in in vitro diagnostic applications.


Key to the performance of the Type 6650 valve is Bürkert’s Flipper technology.


Ensuring clinical flow-rate and reliability diagnostics


A redesigned miniature valve technology is setting standards for size and performance in the laboratory


Un système de valve miniature modifié met en place des normes en ce qui concerne la taille et le rendement en laboratoire.


Ein überarbeitetes Design für Miniaturventile setzt neue Standards im Hinblick auf Größe und Leistung in der Labortechnik


I


solated miniature solenoid valves (IMSV) that provide maximum power from a minimum sized


envelope are the current demand of original equipment manufacturers (OEMs) in the field of laboratory and analysis technology, and also medical engineering.


In clinical diagnostics, flow-rate and reliability are essential, while cleanliness is given top priority. In automated analytics, standard procedures such as titration, defined sampling and the precise dosage of reagents, based on integrated fluid control systems, require pinpoint precision and repeatability.


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In addition, manufacturers and users, when opting for a certain type of IMSV, also consider cost, wetted material type, cleanability, dosage capacity and flushing characteristics of the valve.


Flipper versus rocker valve Until very recently the operating principle of rocker valves – as introduced by German manufacturer, Bürkert, in the early 1990s had been considered state-of- the-art in valve technology. It set the standards for most miniature valves, especially with IVD devices, and has been copied many times.


However, since diaphragms react with a certain deceleration, rocker valves are less suitable for high speed or high precision applications. Tis is not the case with flipper valves; they have no diaphragm, so the pumping effect at the outlet of the valve is almost completely excluded – a big advantage when high precision dosing is needed. Tey are also suitable for small volumes, working quickly and being more durable than rocker valves with their sensitive diaphragm. However, due to their particular design, flipper valves usually have a larger internal volume than valves based on diaphragm technology of a comparable size. Tis increased volume, and especially the cleanability aspect of the valves, have, so far, been considered as the biggest disadvantages of flipper technology. Despite its disadvantages, Bürkert did not give up on the flipper valve – even though the company had developed its more successful competitor.


Instead, Bürkert sought to eliminate all the known problems with the technology. With the help of advanced digital R&D tools, researchers were successful in developing alternatives to the existing construction principles of flipper valves.


Bürkert’s engineers used computer- simulated flows and pressure paths and applied the finite element method (FEM) to optimise their calculations. Te FEM calculations supported the design of the body of the valve, so as to avoid residues that are typical in contaminated systems. Different mouldings were tested and the position of the valve seats was also iteratively defined.


Te resulting optimised internal design enables effective flushing of mediums through the device, in a way that was only previously


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