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Gravimetric control has added a new dimension of accuracy and economy to Riverdale Global’s “no spill / zero waste” system for the supply, dosing, and replenishment of liquid color.

January 15, 2015

3 Min Read
Riverdale global’s total system eliminates liquid color handling problems

Gravimetric control has added a new dimension of accuracy and economy to Riverdale Global’s “no spill / zero waste” system for the supply, dosing, and replenishment of liquid color.

With the Riverdale Global system, liquid color is as easy to handle as pelletized color concentrate. The color container is never opened, and drip-proof connections keep the color completely contained. To enhance this system, Riverdale Global has developed the new Riverdale Gravimetric Stand (RGS), which will be demonstrated at NPE2015 by Riverdale Global (booth S-19189) and Maguire Products (booth W-5663).

In the RGS, a liquid color drum is mounted on a self-calibrating loss-in-weight scale that continually reports the weight of the contents to the controller as a means of ensuring that the target let-down ratio is maintained. Flow is modulated through an air-regulated actuator that is connected to the liquid color pump. The pump is located inside the sealed drum, in accordance with Riverdale Global’s proprietary “Pump in a Drum” design.

“Gravimetric metering holds color-delivery tolerance to within 0.1%, preventing over-coloring and making it possible to reduce costs while maintaining target color levels,” said Paul Maguire, president of Riverdale Global. “Often it is possible to reduce color usage by 5 to 10% in comparison with properly calibrated volumetric metering systems.”

The RGS controller adds to this accuracy, noted Maguire. “In injection molding, for example, the operator simply enters into the controller the target shot weight and letdown ratio. The controller automatically maintains accuracy after determining cumulative error over a number of cycles, eliminating the most costly cause of color waste—operator setting errors.”

Riverdale Global also supplies networking software so the RGS can easily be networked for central control and monitoring. In addition, the RGS tracks real-time consumption data so inventory levels can be monitored and re-order points can be flagged when low levels are reached. A material accounting record allows entry of material cost to track inventory value on a real-time basis.

The RGS eliminates the urethane delivery tube required for the peristaltic pump in a volumetric system. If not frequently replaced, the tube wears out and breaks, spilling colorant in its mineral oil carrier out into the workplace or even into the feed throat of the processing machine. With each RGS, Riverdale Global provides sealed delivery tubes with quick disconnects. The tubes are available in custom lengths. A rack on the RGS permits storage of the tubes. Also supplied is a custom-design feed throat adapter.

The Riverdale Gravimetric Stand is part of a total system designed by Riverdale Global to prevent the handling complications and workplace mess traditionally associated with liquid color. In this system, liquid color is sealed off from any contact with the workplace or environment. The pump is permanently installed inside a standard-size drum that stays sealed from the moment it leaves Riverdale Global to its return from the customer for refill. During processing, color is metered through a sealed tubing assembly, with automatic shutoffs preventing spillage.

Through Riverdale Global’s “return for refill” sustainability program, the processor is credited for residual color in the container and avoids the problem of discarding it. Because Riverdale Global refills used drums for any repeat order of a given colorant, the typical 1 to 3% residual content left in a drum is not lost. The company takes responsibility for pump maintenance, tubing replacement, and other color-handling logistics.

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