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FEATURE SENSORS & SENSING SYSTEMS


Constructed from 316L stainless steel, this prevents corrosion of the flow meter and the bacteria that can develop within it. The smooth, polished design also conforms with the highest grades of pharmaceutical standards


GO WITH THE FLOW Hygiene is fundamental for any purified water metering device


in the pharmaceutical sector. Damien Moran, field segment manager, Hygienic-Pharmaceutical at Bürkert, looks into how SAW technology can be beneficial for this sector


process flush cycles – demands a hygienic flow meter. The sensor therefore needs to be free of mechanical obstructions where bacteria can accumulate, and with a free flow that enables complete flushing and prevents collection of water residue. For processes that involve purified water (PW), deionised water (DI) and water for injection (WFI), the sensor also has to be able to accurately measure fluids with low conductivity.


M


AN ACCURATE SOLUTION Combined with the essential hygienic design and low conductivity measurement capability, the flow meter requires the necessary accuracy to achieve product quality and to help maintain process cost efficiency. For these reasons, mass flow meters (MFM), such as those featuring Coriolis sensors, are often specified. However, for purified water hygienic pharmaceutical applications, measurement of volumetric flow, rather than mass-flow, is most commonly the only requirement. Providing the flow meter can accurately measure real time flow rate, total flow and flow velocity, the additional technology of an MFM to measure


10 DESIGN SOLUTIONS FEBRUARY 2022


easurement of water for clean utilities applications – from OEMs developing skids through to end users requiring


grams and kilograms is redundant and an unnecessary extra cost. What’s more, an MFM is also bettered in hygienic terms.


BENEFITS OF SAW TECHNOLOGY Measurement using surface acoustic waves (SAW), which occur naturally such as in seismic activity, is a tried and tested technology dating back to 1885. Used for the in-line flow measurement of fluids, the technology provides highly accurate volumetric measurement. Bürkert’s FLOWave flow meter generates


surface acoustic waves that travel from the tube’s surface, through the process fluid at a controlled angle in both directions. Calculating the time differences of the waves proportional to the flow, FLOWave determines real time flow rate, total flow and flow velocity in m3


/hr or l/min, measuring irrespective of water conductivity.


HYGIENIC DESIGN Thanks to its completely obstruction-free tube, the key advantage of SAW technology is its hygienic performance, making FLOWave the most hygienic design of flow meter for purified water applications. The straight-through measuring tube means there are no protruding components to come into contact with the purified water,


removing the potential threat of contamination through accumulated bacteria. Some MFMs incorporate a u-bend, preventing water from fully draining away – with the potential for bacterial growth. Instead, FLOWave enables free-draining flush for a hygienic clean in place (CIP) process. Constructed from 316L stainless steel, this


prevents corrosion of the flow meter and the bacteria that can develop within it. The smooth, polished design, also conforms with the highest grades of pharmaceutical standards.


MEASUREMENT PERFORMANCE Due to the precision of surface acoustic wave technology, FLOWave flow meters achieve an accuracy of 0.4% of the measured value, repeatable to just 0.2%. These margins are capable of providing the required performance for any purified water pharmaceutical application including batching, and as there are no moving parts to wear, this level of accuracy endures over time. For the same reason, FLOWave is also maintenance-free. It is also capable of simultaneously measuring


real time flow rate, total flow and velocity. Measurement of flow velocity in a clean utility application is useful to ensure that a minimum flow rate within the loop, for example 0.9 – 1.5m/s


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