Global Processing

How to increase confectionary production utilizing digital Coriolis technology

June 14, 2006

Many food producers encounter serious problems in accurate measurement of process material flows containing both liquid and gas. Example: the popular confectionary ingredient chocolate, a viscous substance produced in batches. Chocolate inevitably retains entrained gas in the form of air, in evenly distributed bubbles or larger “slugs.” The industry’s inability to accurately measure this liquid/gas flow has spawned a host of production problems. These include process interruptions and downtime; wasted material; costly rework; poor product quality; and expensive, time-consuming workarounds.

One problem lies with batch processing itself. In between batches of chocolate, lines must be completely cleaned out with caustic and demineralized water to meet sanitary requirements. Thus the system is empty when the next batch of chocolate arrives. In a typical, costly workaround, producers must start up and “pack the line” with 6 or 7 gallons of unmetered chocolate before any conventional Coriolis flowmeter begins to indicate a measurement. In plants running three shifts per production day, with at least two and often more startup/shutdown cycles per shift, this loss alone can provide troublesome bottom-line impact.

This is the “starting from empty” problem that, until now, even advanced Coriolis meters have been unable to handle. Nor can they accurately measure chocolate containing bubbles or slug flows that occur while the line is running. They exhibit bursts of no measurement, or wrong measurement — or even stall out completely.

In these last cases, starting from empty can overwhelm the meters’ software. This will result in having to purge the line and restart the batch from scratch, wasting material and accumulating downtime.

In many confectionary plants, managers have been told by Coriolis meter manufacturers that the problem is not the meter, it’s their process. So in another expensive workaround, they’ve been forced to construct expensive upstream air elimination reservoirs in attempting to get their process measurement under control. But air elimination can never be entirely successful. And such reservoirs, vented to atmosphere, raise new concerns regarding sanitary food production.

Some leading confectionary processors have at last found a reliable answer to this problematic liquid/gas flow. The Foxboro CFT50 digital Coriolis flow transmitter from Invensys uses breakthrough technology to accurately measure flows containing entrained gas, without stalls, or stoppage. This product’s patented software-based system uniquely prevents the erratic flowtube vibrations that cause measurement failures with problem liquid/gas flows. The transmitter maintains a digitally precise flow measurement, while simultaneously retuning the drive of the Coriolis flowtube every half-cycle of the drive frequency.
The Foxboro transmitter was developed by Invensys in a collaborative effort with Oxford University. The flowtube drive signal is digitally synthesized, providing excellent meter control in challenging conditions. And dynamic response is swift. Independent trials show the meter can respond to a step change in flow within 25 milliseconds (versus traditional response times measured in the tens of seconds), as its sophisticated algorithms correct for the effects of entrained gas.

Users confirm that the CFT50 transmitter shows a “remarkable ability” to meter viscous materials accurately during the difficult startup and end phases of their batch processes.

These processors report that the meter starts up fast. It provides batch flow measurement estimated as accurate to within half a percent of actual flow rate — a hitherto unobtainable result with a viscous material like chocolate running under “batch-from-empty” conditions! (Previous meters were fortunate to get within 10 percent of actual flow.) The plant can dispense with pre-measurement line packing, air elimination systems, and other costly, time-consuming workarounds.