materials handling | Technology Right: The
MCHybrid from Movacolor
combines batch blending with in-line dosing and is said to offer the best of both options
with all of Movacolor’s gravimetric systems, the company’s current MCLan software provides real time monitoring for quality control and material management purposes. Motan Colortronic recently introduced the
volumetric Miniblend V dosing and mixing unit. Intended to be mounted on the extruder between the machine hopper and feed throat, the unit takes up very little space. The company says that the disc dosing technology used on the Miniblend V provides high dosing accuracy, even for small dosing quantities. Three different disc sizes are available, as well as different dosing modules made of materials such as stainless steel or glass. Special wear-resistant discs are available for handling hard and abrasive materials, while module exchange is claimed to be quick and easy to allow for fast colour changes. The Miniblend V is designed to dose free and normal-flowing materials and micro-batches. It can be operated by Motan’s VOLU MC or VOLUnet MC volumetric controls.
Below: The volumetric Miniblend V dosing and mixing unit from Motan- Colortronic
Conveying powders Compounders handle considerable amounts of powder and this can present major challenges in terms of materi- als handling. US-based Conair has developed a new system for improved conveying of powdered resins and dusty materials such as regrind. “Conventional loaders that rely on screens to separate material from conveying air work very well with virgin pellets,” says Doug Brewster, Conveying Product Manager with Conair. “However, when pow- dered material is being transported,
screens can become laden with accumu- lated dust, decreasing the performance of the conveying system. The same thing can happen with dusty regrind and, as plastics processors attempt to use more reclaimed material - either for environ- mental or economic reasons - the issue becomes more acute.” In order to address these prob-
lems, Conair recently introduced two new powder-handling units that the
company says are ideal for conveying PVC and other powders, as well as regrind. Available in a PR (powder receiver) model for use in central vacuum systems and a self-contained PM model with
integral vacuum motor, both are said to offer good conveying and filtration rates. The integral-motor
70 COMPOUNDING WORLD | February 2016
version comes in three sizes with conventional DC brush or brushless motors that can transport up to 454
kg/h (1,000 lb/h) over distances up to 15.25m (50ft). The PR receivers range in volume from 4-85 litres (0.14-3.0ft3
) and lines
sizes up 101mm (4-inch) OD. Both units operate in the same way. Air and material are drawn into the top of the receiver
by the central vacuum pump or the integral motor. A specially- designed filter guard directs the powder toward the bottom of the receiver and past as many as three
pleated polyester cartridge filters that separate air from powder. When the receiver is full (as indicated by an integrated fill sensor), a blowback system directs accumulated, high-power blasts of compressed air down through the filters, blowing off accumulated material, dust and fines. A 3:1 air-to-cloth ratio ensures maximum filtration efficiency. Conair has also recently developed the R-PRO
(Resin-Protection) conveying system to prevent damage to materials and equipment due to high speed vacuum conveying. “In conventional vacuum conveying systems, plastic pellets are widely dispersed in large volumes of air that move through conveying tubes at high speeds,” says Brewster. “Pellets smear against the sides of aluminium tubing, deforming and creating long streamers or ‘angel hair’ that can clog the system. Brittle materials can break up and create dust and fines that also clog the system. Hard and abrasive pellets can quickly wear away the inside of the conveying lines eventually causing leaks and failure. If not controlled, static electricity build-up on and around the conveying tubes can shock operators and cause dust to accumu- late on the inside to the tubes making purging difficult.” The R-PRO conveying system has been developed to
transport material at speeds much slower than conventional high-speed vacuum systems, where pellets move in compact slugs of material at speeds that can range from as slow as 91.5 m/min (300 ft/min) up to 366 m/min (1,200 ft/min). The R-PRO can be an effective way for compounders to convey pellets as raw material from silo or rail car to the compounding extruder or as finished compounded product from the processing line to storage or transport. There may be particular benefits for compounders producing heavily-filled or reinforced materials looking to reduce pellet damage before shipment to the customer. Preliminary testing on R-PRO has also suggested that it
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