New vacuum resin dryer at K 2013

At K 2013, Maguire Products, Inc. will continue with the rollout of a fundamentally new-design vacuum resin dryer by introducing a model of its trouble-free, energy-saving VBD system with throughput, depending on the material being dried, of up to 89 kg (196 lb.) per hour, the company announced today (Hall 10, Stand A26).

The new VBD 150 dryer is sized for the throughputs of many injection molding machines as well as small extrusion lines for products such as medical tubing. Like the 455 kg/hr (1,000 lb./hr.) VBD 1000 model introduced earlier this year, the new model makes operation much simpler and more reliable than with previous vacuum systems, while continuing to dry resin six times faster than with desiccant dryers and using substantially less energy, according to Maguire Europe general manager Paul Edmondson.

"The VBD 150 vacuum dryer has the exact same design and mode of operation as our larger model, using gravity to move material through vertically arranged stages of the drying process, with the discharge of material from one stage to the next controlled by slide-gate valves," said Mr. Edmondson. "This eliminates most moving parts, in particular the three-station indexing carousel mechanism of the Maguire LPD vacuum dryer introduced in 2000. It also does away with gaskets, which can be worn and compromised by resin dust."

The VBD 150 also includes load cells whose value became prominent after the initial installations of the larger model: the capability for real-time monitoring, control, and documentation of material consumption, noted B. Patrick (Pat) Smith, Maguire Products vice president of marketing and sales. "The VBD dryer has a continuous batching operation that is carried out in three vertically arranged, heavily insulated, stainless steel-lined vessels for - respectively - heating, application of vacuum, and retention of resin in a dry state," said Mr. Smith, "Operators can precisely monitor and document material use because both the vacuum chamber and retention hopper are mounted on load cells, and because dispenses of materials from one vessel to the next are carried out by high-speed slide-gate valves with an accuracy per dispense of +/- 4 grams."

The availability of real-time consumption data provides the opportunity to certify processing conditions - a capability that is important for serving medical markets. In addition, the uses of load cells enables operators to set the dryer to the throughput required for optimum energy efficiency, avoiding the energy waste of drying excess material.

Both VBD models incorporate the same operator-friendly software and controller perfected for the LPD dryer, and the same five-year warranty. Additional VBD models will be introduced in the first half of 2014.

VBD 150 Dryer Provides Cost Benefits of Vacuum over Desiccant Systems

The cost savings achieved with vacuum drying result from a reduction in energy consumption of up to 60% in comparison with desiccant dryers; elimination of the need to regenerate desiccant; and reduction in startup time as a result of a drying cycle that is only one-sixth as long. In addition, resin is exposed to elevated temperature for as much as 83% less time than with the desiccant dryer, which means lower risk of material degradation.

In addition to the efficiency of vacuum drying, another reason why drying is six times faster than with desiccant dryers is Maguire's use of dry air to purge the vacuum chamber of the moisture that the vacuum has released from the resin pellets, thus preventing reabsorption.

As an example of the energy efficiency of the VBD system, the first model in the series, the VBD 1000, draws power at the rate of 53 W/kg/hr, as compared with 75 W/kg/hr for the most efficient wheel dryer, according to Mr. Smith.

The three vessels in the VBD dryer systems are, from top to bottom: a heating hopper that brings resin to a target temperature; a vacuum vessel in which vacuum reduces the boiling point of water, causing moisture within the pellets to volatilize and be forced out of the pellet into the low-pressure environment surrounding it; and a pressurized retention / take-away hopper that is continually purged by a membrane air dryer to maintain the target level of dryness until the material is discharged. The heating circuit of the VBD system includes a blower whose variable-frequency drive optimizes blower speed and saves energy.

Vacuum drying is a proven concept, with several thousand Maguire LPD dryers now in service around the world. Maguire will continue to produce and support the LPD system.