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December 1, 1998

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Product News - Gravimetric Batch Blender Addresses Issue Of Homogeneity

Gravimetric Batch Blender Addresses Issue Of Homogeneity

pn2-1298.jpgThe Guardian Series of gravimetric batch blenders are the first in a line of such units said to offer high performance at a relatively low price: $11,950.

According to the manufacturer, Process Control Corp., the new design is the result of discussions with processors about the features that they wanted but found lacking in other batch blenders on the market.

Poor homogeneity was one of the major problems cited. According to the company, when long-term blend accuracy is specified by batch blender manufacturers, it is usually representative of feeding accuracy only, not mixing accuracy. Blend homogeneity, however, is claimed to be the more important measure and requires precise feeding and thorough mixing.

Based on comparative tests with a competitive batch blender, the Guardian blender is said to offer a significant improvement in blend homogeneity, translating to improved end product quality and reduced materials costs.

In the test, consecutive small samples of blend were taken as the process would consume them. The company chose to use a single screw flight of an extruder processing 600 lb/hr at 80 rpm as the sample size, which works out to about 57 grams.

The competitive batch blender had a two-sigma accuracy of 50%, as compared with 6% for the Guardian blender. According to the test methodology provided by Process Control, "statistically, this means that 96% of all samples will fall within the ± 2 sigma range and correlates to a large potential reduction in the amount of additive that processors need to use to meet product needs. With additive prices as high as they are, the Guardian could allow [processors] to reduce additive usage by as much as 50%, as compared to the competing blender."

Material clean out is performed via an integral drain pan that can be folded out to allow complete draining of each hopper. Access doors into the material compartments allow thorough cleaning with the included air hose or cloth wipe down if necessary.

The operator interface is designed to lead the operator step-by-step through recipe entry and blender operation, which is shown graphically on the keypad by lights indicating current status.

Blender hoppers are available in several sizes and mount below the Guardian mixer and are said to provide storage of blended material for the process.

A variety of communications protocols are supported, including Allen Bradley, Modbus, GE CCM2, SPI and ASCII. An available Windows DDE server allows communications with Windows applications such as Wonderware or FactoryLink.

The initial unit is designed for two to four ingredients at up to 700 lb/hr. Other sizes and configurations are being designed and tested for release later this year. For more information on the tests conducted, contact the manufacturer directly (see our Key Contact/Company Directory, p 38).

Process Control Corp.
Atlanta, GA

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