Polymer keeps viscous fluids in check

April 15, 2004
The monitoring of highly viscous fluids such as cola syrup can be problematic.

The Swiss company Plastechnik molds the hollow bodies and covers for the Flowmeter EPI's vanes using nonreinforced Victrex PEEK polymer from Victrex USA Inc., Greenville S.C. (www.victrex.com). The meter body and cover are welded together.

So say some catering operations that report they don't charge for up to 25% of their cola due to inaccurate metering. That's about to change thanks to a flowmeter from Switzerland-based Firma Digmesa AG. It can monitor the volume of not only thick syrups and other beverages but also viscous oils, detergent concentrates, and caustic liquids to an accuracy of ±1%. Such accuracies are a challenge, as these fluids typically have viscosities on the order of 5 to 8,000 centistokes and dispense at flow rates of 0.016 to 4.2 gallons/min.

Key to accurate metering with low-pressure drop (i.e., 3.3 psi for cola syrup flowing at 1.3 gallons/min) is the ease of movement and geometric precision of the flowmeter's two epicycloid turbines. The fluids drive the turbines. Gear wheels engage and control the position of the two turbine vanes relative to each other, while magnets generate measurable pulses.

Digmesa AG uses Victrex PEEK, a nonreinforced polyaryletherketone polymer, to build the turbine's two epicycloids vanes. The polymer maintains dimensional stability despite exposure to aggressive chemicals and high temperatures. This makes for a consistant gap between the turbine vanes and motor casing. The polymer also resists wear over a wide range of pressure, velocity, and temperatures and complies with U.S. Food and Drug Administration regulations.

The high-purity polymer has a continuous-use temperature of 500F. It can be sterilized via common methods making it suitable for aseptic processing and packaging equipment applications that use Clean-In-Place processes. Jean M. Hoffman

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