The new dosing unit integrates the design expertise of Bürkert Fluid Control Systems, a manufacturer of measurement and control systems for liquids and gases, with the experience of Biosystems, a Spanish manufacturer of clinical diagnostics products.
The dosing unit forms one of the cores of the new BA400 analysis device, which is designed to carry out fully automatic analysis of up to 400 tests per hour. The operator prepares the device with the corresponding samples and reagents before starting the analysis process. The design of the new dosing unit has also reduced water and material consumption, which allows the analyser to operate continuously for eight hours without intervention to replace or refill containers.
The aim of the project was to develop a modular dosing unit that would be suitable not only for use on the new system, but also for existing analysis devices available from Biosystems. This posed a considerable design challenge that would need to integrate the various components such as the injection unit, two or three valves, a pressure sensor and a filter, all of which would be mounted onto a transparent, injection-moulded structure.
The solution required considerable design skill and expertise in fluid control in order to deliver very high dosing precision in an extremely compact space. The engineers at Biosystems decided to take advantage of the Bürkert Systemhaus facilities that offer bespoke design solutions that can be manufactured and assembled in-house.
One of the crucial aspects of the design was the detection and prevention of air bubbles which can substantially corrupt the analysis results. Coupled with the requirement for a transparent inspection window, it was essential that the Bürkert designers avoid any rough surfaces, dead zones and sharp edges while creating the new dosing unit.
The engineers developed an injection-moulded component that would house the control elements and machined it in such a way that all of the internal passages had a very high quality surface finish. The control valves, based on the Type 0127 solenoid valve and the Type 6628 Twin Power rocker solenoid valve, were positioned to minimise dead zones and deliver maximum flexibility of control.
The Bürkert solenoid valves have been specifically designed to deliver complete back pressure tightness, excellent flushability and a low internal volume while offering precision switching of micro volumes. In addition, the basic design of these solenoid valves ensures complete fluid separation that enables them to be used with aggressive fluids, which is essential for applications using specific cleaning chemicals as part of the process.
The co-operative approach to the design and manufacture of the new dosing unit has brought together technological innovation and a desire to overcome the technical challenges associated with the development of a unique solution. The final design can be used in a number of analysis devices, thanks to its flexibility, which means that the overall demand for the product increases. This increases the demand for components and reduces manufacturing costs, making the new dosing unit a very cost effective project.