Test bench for dialysis filters
Diaphragm valves with tube valve bodies ensure plant availability – Cooperation with B. Braun Avitum Saxonia GmbH
Sustainability, low operating costs and high plant availability are key issues in the medical technology, pharmaceutical and food industries today. All components installed in the plants and involved in the processes must play their part. This also applies to the countless diaphragm valves that are mainly used in sterile and pharmaceutical applications and must meet strict hygiene requirements and standards. Diaphragm valves in innovative tube valve bodies are an excellent choice. Meeting the demanding regulations of the industry, they can make a significant contribution to reducing operating costs and increasing the available production time. This has been proven, for example, by their use in an automatic test station for dialysis filters.
Dialyser at the heart of dialysis
People with chronic kidney disease must regularly undergo dialysis therapy to purify their blood. At the heart of dialysis is the dialyser: a filter that acts as an artificial kidney and removes toxins from the metabolism as well as excess water from the blood through various physical processes. During dialysis process, the patient’s blood is passed through up to 15,000 hollow fibres in the dialyser, the walls of which consist of a thin diaphragm. This diaphragm has extremely fine pores that allow toxins to pass through but retain the patient’s essential blood components. B. Braun Avitum Saxonia GmbH, a subsidiary of the medical technology company B. Braun SE, manufactures precisely this centrepiece of dialysis – the dialyser – in three plants at its Dresden site. With the help of around 900 employees, fibres are spun and bodies shaped, assembled and packaged here.
It is vital for patients that dialysers work correctly. The filter diaphragms are therefore tested for fibre integrity under clean room conditions in a complex process. For the leak test, the fibres are wetted with sterile water and exposed to sterile test air. Sterile water (highly purified water, HPW for short) of high microbiological quality flows on the dialysate side, while the test air is applied to the blood side. In the event of faults, air passes through the diaphragm and bubbles form. At the end of the test, the tested filter diaphragms are then dried with warm air.
Diaphragm valves from Bürkert in particularly lightweight tube valve bodies save energy and operating costs in SIP processes and increase plant availability. They have been demonstrating their reliability at B. Braun Avitum Saxonia GmbH in an automatic test bench for dialysis filters since 2018.
All test sequences are automated, starting with loading and unloading to clamping the dialysis filters at the test stations and applying the different media in a defined order. This requires numerous valves so that the air and water flow at the many test stations can be precisely regulated.
“In total, more than 600 diaphragm valves are used on the test bench.”
In operation around the clock
Alphaplan GmbH, a specialist in the field of diaphragm filter technology, has designed and built an automatic test bench so that dialysis filters can be tested around the clock in three-shift operation. It consists of several cells, which in turn are divided into several blocks with several test stations.
The requirements on the valves installed in the test bench are high. They must be hygienic, but also offer good thermal and process properties: they need to be easy to clean and suitable for the high temperatures involved in the SIP processes between the actual test phases. A long diaphragm service life is absolutely essential because the plant area is only shut down once a year for maintenance work. For these reasons, the test bench manufacturer, who has been working with Bürkert for many years and appreciates the expertise of the fluidics specialists, decided in favour of diaphragm valves in a tube valve body, which are already in their third generation on the market and have been perfectly adapted to their area of application in the pharmaceutical, food and cosmetics industries.
The dialysis filters are tested around the clock in three-shift operation in an automatic test bench under clean room conditions.
Fast heating and cooling
The particularly lightweight tube valve bodies help to save energy and costs in SIP processes, as they heat up and cool down quickly. With a temperature difference of 100 K, energy savings of more than 50% can be achieved per SIP cycle, which can lead to considerable cost savings depending on the number of CIP/SIP processes per year. Production becomes more sustainable and the CO2e footprint of the process is reduced. At the same time, the productivity of the plant increases, as the fast heating and cooling process reduces non-productive cleaning times. What’s more, the temperature-sensitive diaphragms are subject to less thermal stress. Depending on the application, this can more than double their service life, significantly extending the necessary service cycles and also reducing hydrocarbon-intensive elastomer waste. The diaphragm valves in the tube valve body have also proven their reliability in extensive quality tests.
Innovative tube valve body housing in use in an automatic test station for dialysis filters.
Test procedure takes into account the usage conditions
The B10 value according to the DIN EN ISO 13849 standard is important in connection with the life expectancy of a valve. This is the statistical expected value of the number of cycles in which 10% of all components have exceeded specified limit values (number of switching cycles) under defined conditions (90% probability of survival). The “problem area” with diaphragm valves is the diaphragm, which is always subject to a certain amount of wear. However, this in turn depends on the usage conditions, such as the temperatures, the number of switching cycles or the media. Realistic data was therefore determined in a special test facility to be able to specify an application-specific B10 value. For the test bench, this means that the valve diaphragms only have to be replaced every two years during the regular maintenance interval.
“This has proved to be accurate in practice and the diaphragm valves work very reliably.”