The Desiccant-free Zone

At NPE 2000, advances in vacuum or compressed air drying brought into question the future viability of desiccant-based drying systems. Today, desiccant systems remain a drying stalwart, but the field of nondesiccant systems continues to expand.

AEC Inc. and Sterling, siblings in the ACS family of auxiliary companies, brought several compressed-air models to the show. The machine- or floor-mount AC and ACM Series dryers use AEC’s DH Series mass-flow drying hoppers. The AC lowers the compressed air’s dewpoint to 20F, and the ACM’s membrane assembly provides a –40F dewpoint. Along similar lines, Sterling offered the SMD and SCD Series compressed air dryers as an alternative to its STT Series desiccant line. Stainless steel heater boxes for the dryers are available in 30 or 60 cfm.A smaller system was put forth by Motan Inc., with the added flexibility of a throat-mounted design. The LCA15 and LCA30 compressed air dryers use only 2.5 to 9 cfm of shop air, conserving energy but offering dewpoints to –13F or as low as –40F with an optional membrane.

Comet Automation Systems Inc. (Dayton, OH) remains in the compressed air business, with the ERD Baby. Throughputs range from 2 to 3000 lb/hr, with dewpoints reported to be less than –40F, and the controls feature an integrated weekly timer.

Novatec Inc. and Maguire Products continue to ride the success of their NPE 2000 vacuum dryer innovations, expanding line sizes since the last show and offering field results as proof of their continued efficacy. Novatec’s patented NovaDrier, which operates without a process motor, regeneration heater, or valves, is said to provide dewpoints of –40F within 4 minutes of startup.

Maguire now offers its Low-Pressure Dryer (LPD) with a 1000 lb/hr throughput, five times the capacity of the next largest LPD. Maguire says the line is well suited for PET preform or large-part molding.

Using a counterflow of heated, subatmospheric air to convey moisture away, the Speedryer from Canam Manufactured Products has no desiccant. Instead, rapid heat transfer, generated by a series of tubes, conveys warmth directly to the pellets. Entrapped moisture is brought to the surface where it’s carried away. The hopper is manufactured from an epoxy composite for a smooth, strong, yet light component.

Desiccant Systems

Appreciating molders’ continued efforts to seek molding niches, many companies rolled out application-specific models. Addressing the needs of micromolders, Dri-Air introduced a Micro Dryer, which is able to dry as little as a few grams or as much as 5 lb. A desiccant media dries ordinary compressed shop air at airflow rates of .5 to 3 cfm. For medical molders, Dri-Air’s Med-X Series features stainless steel construction throughout and Hepa filters to clean air going to the hopper. To ensure no contamination downstream when material has been dried, it’s sent to the press with dried, clean air in a closed loop.

As the name would indicate, AEC’s Nomad II Series is a portable drying and conveying system integrated onto a single cart. It uses an AD Series desiccant dryer and has four configurations. AEC also displayed its new AD line of miniature cabinet dryers, with a dual-bed, closed loop design. A regenerative blower offers full-rated airflow at 15, 30, or 60 cfm. On the opposite end of the spectrum, AEC’s AD-3000 operates at 3000 cfm, and it comes with an optional gas-fired heater assembly for process and regeneration heat.

Matsui made a splash recently with its Plas-Aid line of portable material handling equipment, which came to NPE 2003 using the latest iteration of the company’s desiccant-rotor technology. Matsui bills it as pocketbook-friendly with lower maintenance needs thanks to solid-state relays and oversized filter elements.

Portability is the selling point of Una-Dyn’s GS Drying system, which has a dual-desiccant bed dryer mounted to a small-footprint, five-wheel cart. Sizes range from 30 to 150 cfm, and the modular hoppers have standard sizes from 50 to 800 lb.

Wittmann rolled out an all-new dryer for the show, the Drymax 30. It features a twin-bed desiccant for throughputs of 35 lb/hr, and it uses two high-capacity molecular sieves for constant dry air and an operating dewpoint of –40F. Wittmann reports that the unit has only one moving part.

Conair stressed value, promoting a D Series dryer under the slogan “New Value for a New Economy.” Prices start at $2800 and throughputs top out at 100 lb/hr in the compact 35-by-17-by-27-inch units. They use an indexing desiccant carousel to eliminate temperature spikes and create –40F dewpoint drying air.

With versatility in mind, Process Control rolled out its D Series desiccant dryer, offering a throughput range of 30 to 2500 lb/hr. The DP Series, which dries 30 to 100 lb/hr, has a portable configuration. All the models are closed loop to keep ambient moist air out, and hot exhaust air from the regenerative circuit is recaptured by the heater.

Finally, to see how well your dryer is working, check out Vaisala’s Drycap Dewpoint Transmitter DMT142. The miniature dewpoint measurement instrument can be mounted inside a dryer, in tight spaces, or in small-size pipelines. The sensor is accurate to ±3 deg C, and is said to remain on-spec for two or more years with no maintenance. It measures dewpoints from –50 to 60C (–76 to 140F).

Taking Control

Equipment suppliers continue to exploit the inherent advantages of microprocessor-based controls, giving molders the opportunity to link even the most mundane equipment into a complex chain. In this way, each link can be individually monitored and controlled, while giving continuous feedback. Nowadays, this can happen from a central computer on the floor, one slightly further removed in an office, or in the plant supervisor’s home as he or she logs in from the den.

In addition to networking, scalability was a buzzword at many booths, as suppliers increase installation flexibility and the ability to ramp up future capacity with distributed I/O systems. In this setup, a flat cable runs throughout the plant and attaches to a central control. As needed, modules hook equipment into the cables, and down the line, into the control box. This is much more flexible than individually hard wiring each device to the central control through miles of wire in a rigid design.

Conair advanced this trend by introducing its Intelligent Loading System (ILS). The distributed I/O system is built around Control Logix or Compact Logix industrial-grade CPUs from Rockwell Automation. Up to 96 loaders can be attached to the DeviceNet cable via Armorblock modules. Conair reports that upfront costs are higher, but ROI is realized in large-scale layouts or down the road, if capacity is increased. It also offered a semidistributed ILS to handle 32 loaders, 16 pumps, and 32 materials. In this layout, equipment is situated in clusters, which in turn are linked to the main I/O ribbon.

Motan updated its conveying controls, adding bus-system communication and distributed I/O capabilities. Its Metro A Series central conveying control now uses color touch-screen displays and can run from two to eight blowers and 15 to 60 receivers. In addition, the Metronet bus system uses a Mitsubishi PLC as the heart of a distributed I/O layout that Motan claims saves electrical installation costs by as much as 80 percent.

Labotek has applied TCP/IP networking to allow communication for all its its desiccant dryers so that they can be monitored and controlled from any Web browser without external software. The Windows NT-based system, which allows real-time and historical trending, was recently installed at Winzeler Gear (Chicago, IL), and Labotek representatives took interested parties to see the system in action during NPE. Further stretching the distance between operators and control panels were the infrared, handheld remote controls that can operate up to 99 of Labotek’s Mini-Feed hoppers.

Novatec used NPE to announce that its NovaTouch PLC controls will now be a standard option on most Novatec equipment. In the system, a single plug-in module can be moved from one piece of equipment to another for service teams to perform maintenance remotely.

Blend, Load, and Feed

In lieu of major overhauls, many companies chose instead to streamline their material conveying equipment, whether feeders, hoppers, or blenders—eliminating hangup points and going to mechanically actuated valves —to provide customers with greater efficiency and consistency.

AEC and Sterling also brought new equipment to the handling table. The BD-2500 gravimetric batch weigh blender from AEC includes load-cell technology to manage six materials. The device uses stroke-limiting restrictors to ensure accurate metering. Sterling’s entrant in this field is the SGB Series gravimetric blender. Accurate to .1 percent, the SGB uses load cells to track additives on a gain-in-weight basis.

On the receiver side, AEC’s SRC30 and SRC60 boast a redesign that includes stainless steel construction, a brushed interior finish, and a stainless steel filter screen, with 6-inch discharge throats. Sterling brought out the new SDD Series digital dosing system, which uses a disk rather than an auger to feed granulate, pellets, or powder additives.

Motan stressed economy, rolling out its S Series receivers with a positive sealing plunger and 500-mesh screen. In feeders, Motan brought the Minicolor volumetric feeder that can be mounted between the receiver or hopper and the machine’s throat. On the gravimetric side, Motan displayed the Gravicolor line with throughputs ranging from a few pounds to 4000 lb/hr.

After 15 years, Wittmann decided it was time to redesign its Feedmax line of vacuum loaders. The company removed interior hangups from the stainless steel drum and installed quick-release toggle clamps throughout the modular unit for simple disassembly to perform cleaning and maintenance. The discharge valve shuts off pneumatically and interchangeable machined aluminum reducers work with all standard line sizes.

L-R Systems upgraded its WSB-Series weigh scale blender line to include a color touch-screen interface, which shows online operation of the blender. It can now feed material at a 1000 lb/hr clip and blend everything from pellets to regrind to powder.

On the material feeding side, Colormax Ltd. used NPE 2003 to debut its Posimax B200 additive feeder. The Posimax uses a rotating channel to feed materials, creating what it calls true mass flow in a screwless design.

Novatec emphasized speed with its new Quick Change Auger Feeder—a blending product with a removable hopper for cleaning or swapping hoppers or augers.

Promising precision, TSM Control Systems rolled out the Midibatch Blender, a gravimetric blender for up to four materials that, through the use of two patented Micradose valves and a reverse-flight auger, can dispense individual pellets.

On the control side for extrusion, Maguire Products continues to fine tune its LineMaster software for the company’s gravimetric blenders. The new blender control software, Gravimetric Gateway (G2), features a yield control that adjusts extruder speed by calculating throughput based on two parameters: target line speed (length of product per time unit) and target yield (weight per length of extruded product) to provide greater accuracy.

Material Selection

Material handling equipment suppliers declared war on downtime brought on by material changes with a series of innovative material selection systems that provide flexibility for custom shops with lots of material changes, and hands-off operation to ease use. (For Wittmann’s robotized solution, see August 2003 IMM, p. 27.)

Motan’s Metrolink system is a completely hands-off model, with a standard unit that manages up to 15 destinations for up to 16 material sources. It can be set to run automatically, as a slave to a central PLC, or through a touch pad.

Conair was waxing philosophic at its booth during NPE for the introduction of the ResinWorks system, which it billed as a change in material handling philosophy. Drying, blending, and conveying are combined in a modular format riding a mobile sled and offering any material to any machine at any time. Conair claims 10-minute material changes are possible, and after every batch of material is sent from dryer to press, the lines are purged to prevent contamination.

Sterling appreciated the premium on shop-floor space as evidenced by its offering, the SDRW rotary valve. Used for automatic material changes, the SDRW has hardened surfaces to handle abrasive materials, and its 10 input/output ports can receive material from 10 different locations. They can also send materials to 10 different locations, so if placed back to back with another valve assembly, Sterling says there are 10 sources and 10 outlets for a total of 100 different conveying options.