Riverdale Global (Aston, PA), an international supplier of sealed liquid colorants and additives to the plastics industry, has developed a material handling system that automatically refills one or more liquid color drums during the molding or extrusion process. The technology eliminates downtime for switching drums and reduces the occurrence of transitional or off-specification product with little or no color.

Riverdale Global supplies liquid color in patented pump-equipped drums that remain sealed while color is metered to processing machines. The RGInfinity auto-refill system eliminates the need to replace empty drums by refilling them from a large central container, or "tote." One central container can serve one or multiple machines running the same color. Sealed connections throughout the system, from tote to delivery tubes to drums to metering tubes, keep liquid color completely sealed off from the workplace. Each drum is mounted on a Riverdale Gravimetric Stand (RGS), which monitors the weight of color in the drum and signals a pump valve on the tote when the drum is nearly empty and again when it is full. This prevents uncolored product. When the central container needs to be replaced with a full one, the sealed connectors enable a quick changeover. Containers are available in various shapes and sizes. A typical example is a 200-gallon rotomolded plastic vessel within a steel supporting framework, but it is possible to use a standard-size drum for refilling the on-line drum, replacing the empty "refill" drum with a full one while color metering continues uninterrupted.

"Besides preventing downtime, the RGInfinity auto-refill system eliminates the time and labor required for operators to monitor color levels, transport and prepare replacement drums, and wait until on-line drums are finally ready for replacement," said Kevin Cabana, Vice President, Process Technologies, in a prepared statement. "Also prevented is the human error that creeps in during these procedures, particularly when there are multiple drums metering color to multiple processing machines."

By preventing off-spec production, the RGInfinity auto-refill system saves time and labor as well as reducing scrap, according to Riverdale. "The higher the production volume, the greater the benefits," said Cabana. "Without the RGInfinity auto-refill system, operators of extrusion and molding lines often choose to generate off-color product during drum replacement rather than stopping production. The resulting scrap material must be culled out, removed from the work area, and disposed of."

The RGInfinity auto-refill system is an extension of Riverdale Global's Sealed Color technology, which eliminates the complications of handling liquid color. Central to the technology is the proprietary "pump in a drum" design, which enables the drum to remain sealed during delivery from Riverdale Global, metering into the process, and replenishment through return of the drum to Riverdale Global.

In the Riverdale Gravimetric Stand, used as part of automating the RGInfinity auto-refill system, a liquid color drum is mounted on a self-calibrating loss-in-weight scale that continually reports the weight of the contents to the RGS 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 pump inside the sealed drum. The gravimetric control holds color-delivery tolerance to within 0.1%, preventing over-coloring and making it possible to reduce costs while maintaining target color levels.