Materials Handling

Whether for multi-machine molding plants, blown film operations, profile extruders or compounders, high-volume materials handling systems have several features in common. Centralized blending, drying and conveying are standard; controls must be easy to use; measuring accurate; and material changes quick.

A high-volume processor is much more likely to receive resin in truck- or railcar-load quantities than in bags or gaylords, so bulk unloading systems are a potential area of improvement.

“Processors are concerned about occasional discrepancies between the stated amount in the railcar and the actual amount of material conveyed to a silo,” explains Richard Hamilton, president of Hamilton Avtec Inc. “We have designed and manufactured various systems which monitor material coming out of the railcar, weigh it and then convey it to the silo.”

Rob Miller, president of Nucon Systems Inc., believes that more engineering knowledge is required to design a high-volume materials handling package than a typical lower-volume system. “You can’t just take carbon copy 40,000 lb./hr. systems and put them in different plants. In high-volume applications it is very easy to degrade the material and special pump and piping configurations may be necessary.” Nucon has installed several 40,000 lb./hr. railcar systems for resin producers and distributors.

CENTRAL CONVEYING: CONTROL IS THE ISSUE

In central conveying systems, the most notable trend is the desire for improved control. Novatec offers an alternative to the traditional central conveying controller with its Exxpand distributed control network. It is suitable for plants with as few as three machines to those with 55 or more.

Exxpand provides lower-cost, beside-the-press control of loading station functions through individual intelligent devices called nodes. Exxpand may reduce downtime compared with more conventional controls because if a problem occurs with one node, the rest of the system continues to function.

Foremost Machine Builders’ Format IV is a user-friendly, PLC-based vacuum loading system controller. The Format IV can remember the time necessary to load each station and periodically adjusts load time automatically for optimum overall cycle. It can control up to three vacuum pumps and 27 loading stations. System configurations are accomplished by manually entering commands on a membrane switch touch pad, directed by printed instructions on screen.

AEC/Whitlock has added a twist to its SR Series stainless steel vacuum receivers: a sequence valve that is integral to the hopper cover. The new, patent-pending approach offers processors an alternative to conventional sequence valves located on the vacuum header of a central multistation conveying system. Moving the valve down to the hopper cover simplifies wiring and pneumatic connections in most applications. The SR Series can be purchased as standard hopper loaders or vacuum receivers. They are a modular design, so that tube studs, hopper bodies, quick clamps and motor assemblies are interchangeable and are compatible with existing Whitlock designs.

SOFTWARE IMPROVES BLENDER THROUGHPUT

Recent software upgrades have made it possible for Conair’s AutoWeigh blenders to weigh batches more quickly, which means more batches can be weighed per hour and overall throughput is increased by 25 percent or more in large models.

Central, real-time access to multiple GXB blenders is provided by Mould-tek’s new T-Com software. The software provides two-way communications between a central PC and the multi-task, touch-screen controls of GXB blenders.

Each blender is continually monitored for materials usage, formulas, settings, total throughput and parameter settings. Formulas can be generated at the central computer and downloaded to the selected blender.

Maguire Products’ large blenders, blending up to 18,000 g (40 lb.) at a time, use a double “reverse flow” mix chamber to ensure proper blending at high output rates. The Series 1800 units are suitable for central blending systems, with throughput ranging from 3000 to 5000 lb./hr.

AUTOMATED INGREDIENT CONTROL IMPROVES ACCURACY

At Huntsman Film Products of Canada (Toronto), the desire for more accurate, consistent weighing prompted the switch to an automated system for measuring and weighing minor ingredients for PVC compounds.

Huntsman installed a MicDos system from Riemelt to handle powder and solid ingredients needed for its PVC compounds used to produce thin-gauge film for food packaging. Each MicDos has six to ten hoppers for ingredient storage and a mobile scale with electric drive to weigh materials. Metering is automatic, driven by recipes. At Hunstman, the weighed material is then released to a pneumatic conveying system.

“Choosing an automated system was not a productivity issue; it was a consistency issue,” says Bryce Atkinson, plant manager. “MicDos has given us more accuracy and more consistency, and of course, cost savings.”

John Little, sales manager with Riemelt, says many high-volume processors choose to automate in-house compounding, especially when using PVC. “We have installed outdoor silos for calcium carbonate at several locations, with conveying and feeding equipment.”

O.A. Newton has upgraded its Micro Ingredient Controller for compounders with electronic load cells, variable frequency drives, and bulk bag handling capacity in excess of 2000 lb. The Micro Ingredient Controller dispenses, weighs and conveys minor ingredients, as part of O.A. Newton’s complete compounding systems.

GAS-FIRED DRYERS PROVIDE BIG SAVINGS

For high-volume operations, using gas-fired dryers instead of more traditional electric units can provide significant savings.

Consider this example, provided by Conair.

A typical large-volume dryer, like Conair’s 3200H Series (4050 lb./hr. of nylon), might consume 250 kW per hour to yield about 853,000 btu of drying energy. At $0.06 per kWh, the hourly cost of that electricity will be approximately $15. The same amount of drying energy (853,000 Btu) will require about 850 cu. ft. of gas. At $4 per 1000 cu. ft., the hourly gas cost would be about $3.41, for a savings of $11.58 per hour. In a plant where that dryer runs 7000 hours per year, the savings achieved by using gas instead of electricity would total about $81,000 per year.