MATERIALS HANDLING: Liquid-Color System Adds Gravimetric Control

The addition of gravimetric control reportedly makes liquid color as easy to handle as pelletized color concentrate.

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Riverdale Global’s, Perth Amboy, N.J., latest enhancement to its “no spill / zero waste” system for the supply, dosing, and replenishment of liquid color is the Riverdale Gravimetric Stand (RGS). The system will be demonstrated at NPE2015 by Riverdale Global (Booth S19189) and Maguire Products (Booth W5663).


With the new RGS technology, 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 to ensure the target let-down ratio is maintained. In Riverdale’s “no spill / zero waste” technology, the color container is never opened, while drip-proof connections keep the color completely contained.


Flow is modulated through an air-regulated actuator that is connected to the liquid color pump, which is located inside the sealed drum, in accordance with Riverdale Global’s proprietary “Pump in a Drum” design.


By holding the color-delivery tolerance to within 0.1%, gravimetric metering can prevent over-coloring, reducing costs and maintaining target color levels. Paul Maguire, president of Riverdale Global, noted in a release that the technology can reduce color usage by 5 to 10% in comparison with properly calibrated volumetric metering systems.


In an injection molding application, for example, the RGS allows operators to simply enter the target shot weight and letdown ratio into the controller. The controller then automatically maintains accuracy after determining cumulative error over a number of cycles, which eliminates the most costly cause of color waste—operator setting errors.


The RGS can also be supplied with networking software, connecting it to central control and monitoring. The RGS also 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 costs to track inventory value on a real-time basis.


The RGS also eliminates the urethane delivery tube required for the peristaltic pump in a volumetric system. If not frequently replaced, Riverdale noted that the tube can wear out and break, spilling colorant into the workplace or the feed throat of the processing machine.


The RGS has sealed delivery tubes with quick disconnects available in custom lengths. The system also includes a rack to store the tubes, as well as a custom-design feed-throat adapter.


Riverdale notes that the RGS is part of a total system designed to prevent handling complications associated with liquid color by sealing off the liquid. The pump is permanently installed inside a standard-size drum, and color is metered through a sealed tubing assembly, with automatic shutoffs preventing spillage. Riverdale’s “return for refill” sustainability program credits processors for residual color in the container and avoids the problem of discarding it.