Pharmaceutical & medical
users requiring process flush cycles, demands a hygienic flow meter. This means a sensor that is 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.
F
VoluMetric or MASS FloW MeASureMent? 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 grams and kilograms is redundant and an unnecessary extra cost. Furthermore, an MFM is also bettered in hygienic terms.
SurFAce AcouStic WAVe tecHnology Measurement using surface acoustic waves (SAW), which occur naturally such as in seismic activity, is 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 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 Based on a 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
22 January 2022 Instrumentation Monthly
or any purified water metering device in the pharmaceutical sector, hygiene is fundamental. Measurement of water for clean utilities applications, from OEMs developing skids through to end
Hygiene, accuracy and cost effectiveness for pharma-grade water flow measurement
For pharmaceutical-grade water and ultra-pure media applications when volumetric flow rather than mass flow measurement is needed, surface acoustic wave (SAW) technology provides optimum hygiene with high accuracy. Able to measure low conductivity fluids, flow meters with SAW technology also provide the most cost effective measurement for purified water. Damien Moran, field segment manager, Hygienic-Pharmaceutical at Bürkert, explains the benefits of SAW technology and the advantages over traditional measurement sensors for purified water and clean utilities.
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 As a result of the precision of the surface acoustic wave technology, FLOWave flow meters achieve an accuracy of 0.4 per cent of
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