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Alicat Mass Flow Meters Vs Rotameters in Bioprocessing

Wednesday, September 14, 2022

All bioprocesses need flow meters; be it to drive chromatography and filtration, feed reactors, or monitor crucial process parameters.

For decades, the humble Rotameter has been a staple of flow instrumentation, providing low cost and high reliability solutions across industry. But what if there were an alternative; one with increased precision, automation, scalability, and customisation? That would be worth knowing about, right?

How do they work?


Rotameters measure the volumetric flow rate and consist of a float inside a tapered tube. The vertical force of a gas or liquid flowing through the tube determines the position of the float, which is then read off a printed scale or magnetically coupled indicator. This is all very well and good until conditions change. A fluctuation in temperature or pressure can dramatically alter the volume of the gas passing through your meter. Adjusting the flow rate to compensate can appear to solve the problem, but Ideal Gas Laws mean we’re now flowing a different “Mass Flow” (read the difference between volumetric flow), or number of particles at any given point. This can be disastrous for repeatability or consistency of product and requires careful management to avoid.

Alicat Mass Flow Meters

An Alicat Mass Flow Meter on the other hand, utilises a differential pressure measurement principle. By measuring the pressure difference across a known geometry, and with the help of the Hagen-Poiseuille equation, we can calculate a volumetric flow rate. Interesting enough, but at this point we simply have the equivalent of a very accurate Rotameter, still susceptible to the same process changes discussed earlier. The clever part is when we introduce instantaneous fluid pressure and temperature measurement. Now we can calculate Mass Flow, a flow rate that accounts for process conditions, and one that is comparable with any other Mass Flow reading.

Learn how differential pressure is used to measure laminar flow - Video demonstration

Flow meters For Bioprocessing Applications

The tried and tested Rotameter delivers on simplicity and cost, but industry is increasingly looking to Alicat Mass Flow Meters to drive the next generation of Bioprocess applications.

Sub ±0.6% of reading accuracy statements facilitate Increased Precision across the process. Analog, and Serial Communication protocols with Pharma 4.0 in mind allow for deeper integration and automation, whilst significantly Higher Operating Ranges open up options of increased scalability.

The Alicat Bio-Series take this one step further with the use of ASME-recommended materials, including 316L stainless steel and USP Class VI FDA-grade certified elastomers.

Whatever your process, PCT have a solution suitable for your application. Contact a PCT Sales Engineer today to discuss things further.

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