Published On: Sat, Mar 23rd, 2013

Vacuum Dryer of Totally New Design Is Trouble-Free, Yields Big Cost Benefits

Maguire® VBD™ Vacuum Dryer Is a New-Generation System that Will Supersede the LPD™ Vacuum Dryer Now In Use around the World

Vacuum Dryer of Totally New Design Is Trouble-Free, Yields Big Cost Benefits

Vacuum Dryer of Totally New Design Is Trouble-Free, Yields Big Cost Benefits

ASTON, PENNSYLVANIA, U.S.A., March 22, 2013: A resin dryer of fundamentally new design dramatically advances the concept of vacuum drying, making operation much simpler and more reliable than with previous vacuum systems while continuing to provide substantial reductions in drying time and energy consumption in comparison with desiccant dryers, it was announced today by Maguire Products, Inc.

While the concept of using vacuum to force moisture from within resin pellets remains a radical departure from conventional desiccant systems, the new Maguire® VBD™ Vacuum Dryer adds another simple concept: the use of 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. 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 sealing gaskets, which can be worn and compromised by resin dust, and with perforated screens, which require cleaning.

“The VBD Vacuum Dryer provides trouble-free, low-maintenance service, along with the same operator-friendly software and controller used with great success on the LPD dryer, and with the same five-year warranty,” said B. Patrick (Pat) Smith, vice president of marketing and sales. “The savings in energy and startup time in comparison with conventional desiccant systems enable the processor who switches to the new VBD dryer to pay back his investment in a matter of months.”

The first model in the new-generation system is the VBD-1000 Vacuum Dryer, with a throughput capability of up to 1,000 lb. (455 kg) per hour. The unit is 16 ft. (4.9 m) tall and has a footprint of only 6.8 ft. (2.1 m) by 3.7 ft. (1.1 m). It can be configured for mounting on the shop floor (as in the accompanying photo) or on a mezzanine. Maguire offers the unit for around USD $60,000. A series of smaller VBD dryers, starting with a throughput of 100 lb. (45 kg) per hour, will be introduced in coming months.

VBD™ Dryer Combines Low Cost of Vacuum Drying with Trouble-Free Operation

The cost savings achieved with vacuum drying result from a reduction in energy consumption of more than 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 80% less time than with the desiccant dryer, which means less processed-in stress.

Vacuum-drying in the new VBD dryer is a multi-stage, continuous batching operation carried out in three heavily insulated, stainless steel-lined vessels arranged vertically. High-speed slide-gate valves for dispensing material from one vessel to another have an accuracy per dispense of +/- 4 grams and are of the same design widely employed in other Maguire equipment. The system uses ambient air that is circulated by a blower whose variable-frequency drive saves energy.

From top to bottom the vessels are:

● Heating hopper. By means of a centrifugal blower and a 40 kW heating element, material is brought to a temperature that has been set on the control panel. The volume of this hopper is three times that of the next (vacuum) vessel, ensuring adequate heating time.

● Vacuum vessel. A vacuum applied by a venturi generator 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. The moisture is purged from the vessel with -40 dew point air constantly generated by a membrane air dryer.

● Retention / take-away hopper. The membrane air dryer also continually purges this pressurized vessel, ensuring that the target level of dryness is preserved until the material is discharged into the plastics extrusion or molding process.

Vacuum drying is a proven concept, with several thousand Maguire LPD dryers now in service around the world. Maguire expects the VBD dryer to supersede the LPD system, though the company will continue to make a small LPD version for laboratory use. Photo Caption: Maguire® VBD™ Vacuum Dryer is shown with frame for floor mounting. Vessels from top to bottom are heating hopper, vacuum vessel, and retention / take-away hopper. Visible in window at lower left is membrane air dryer for purging moisture from vessels. Controller is at upper left.

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