The Maguire Low Pressure Dryer (LPD) is a revolutionary device that uses
vacuum to accelerate the resin drying process. The use of vacuum provides many
process and cost benefits compared to conventional drying technology.
Maguire Products did not invent the science of low pressure (vacuum) drying. In
fact vacuum drying has been used in the manufacturing process of plastic
resins, chemicals, food and pharmaceuticals for many years. But, Maguire
Products is the first to bring this technology to the plastics industry in a
package that is affordable, reliable and simple to operate.
Why is the LPD Better?
- Speed of DryingTypically the vacuum dryer will dry materials in one-sixth
the time of a desiccant dryer. If your desiccant dryer drying time is 4 hours,
the vacuum dryer will do the job in 40 minutes. The result is time-savings of 3
hours and 20 minutes every time you start up a dryer. This not only represents
reduced energy cost (see below), but could also represent 3 hours and 20
minutes of additional production time.
- Energy SavingsSide-by-side testing of the vacuum dryer and a desiccant
dryer shows reduced energy consumption of 70 - 80%. The key to the reduced
energy consumption is that the vacuum dryer does not rely on desiccant.
Desiccant, once saturated, must be regenerated by a heating and cooling process
so it will again be able to absorb moisture. All energy required to regenerate
desiccant is lost to ambient.
- Reduced MaintenanceSince desiccant degrades over time it must be replaced
on a regular basis. This expense is avoided with a vacuum dryer. In addition
the need to monitor the condition of desiccant is eliminated.
- Low Material StressLong drying times at elevated temperatures can cause
thermal, chemical and physical material degradation. Materials if exposed to
prolonged elevated temperature during drying run the risk of degradation
including discoloration and/or IV drop which leads to reduced physical
properties of the end product. The reduced drying time required with the vacuum
dryer dramatically reduces the risk of material degradation. Since the vacuum
dryer first heats up the material, then applies vacuum to accomplish drying the
heating cycle is only 20 to 30 minutes.
- On-The-Fly Material ChangeAdditional savings can be achieved with the
vacuum dryer in the form of on-the-fly material changes. Since the vacuum dryer
dries in batches a material or color change can be accomplished on-the-fly.
This means no downtime related to clean-out of the drying hopper during a
material change. Every time you have a material change with a desiccant dryer
the dryer must be shutdown and the drying hopper cleaned. This is normally a
time-consuming, labor-intensive process. The vacuum dryer will automatically
notify the operator when it's time to conduct an on-the-fly material change. No
interruption of the drying process occurs during the on-the-fly material
change.
- The LPD Dryer Microprocessor ControllerThe LPD controller is very simple to
use. The dryer may be operated by simply setting the proper temperature and
cycle time on the thumbwheels located to the right. The display will indicate
temperature and elapsed cycle time or, alternatively, temperature and vacuum
level. If a problem occurs during operation an alarm strobe and horn will be
activated and the nature of the problem will be indicated on the display. The
controller monitors numerous alarm conditions to ensure proper
performance. Comparable to a dew point monitor, vacuum level is always
monitored to ensure proper vacuum level is maintained. As an aid to
monitoring dryer performance and documenting operation a printer port is
provided on the controller. A printed output of dryer operation may be obtained
for each drying cycle.
The controller can be easily removed for service or replacement. If you have a
controller problem a complete new control panel may be installed in
minutes.
How the LPD Dryer Works:
The dryer operates with 3 Stainless Steel canisters that are mounted
directly onto a carousel that indexes counterclockwise 360 degrees. Through
this 3 step process each canister systematically goes through the following 3
stages to dry materials.
Stage 1:
Filling: In the first stage the canister is filled with material
using a specially designed dispense valve to ensure the canister can never
overfill. Mounted above the dryer is a surge hopper for material resin which
ensures the canister can be filled in the minimum amount of time necessary.
Heating: As the canister is being filled the heating process also
begins. Temperature settings are made easily by simply dialing in the required
temperature on the thumbwheels of the controller.
Due to the relatively small volume of the canisters when compared to
traditional large drying hoppers the material can come up to the required
temperature rapidly. Once the canister has been heated for the time set it will
then index automatically to the next stage.
Stage 2:
Vacuum: When the canister indexes from Stage 1, it is sealed and
very strong vacuum is applied. As air pressure drops, water boils at lower
temperatures. Once the material is under vacuum, the boiling point of water
falls from 212ºF (100ºC) to 133ºF (56ºC). Moisture is rapidly driven from the
material and evacuated to ambient air. The dryer controller continuously
monitors vacuum level ensuring the vacuum remains high. If the proper level of
vacuum is not maintained an alarm will sound.
Stage 3:
Material Removal: After the Vacuum cycle is completed the
canister indexes again to the material take off position. Under automatic
operation a valve in the bottom of the canister is opened and material then
flows from the canister into a material take off pan. Dry material is then
drawn by a vacuum loader to the process machine. Material level in the takeoff
pan is monitored continuously by a proximity sensor. At the end of the cycle
time the canister will index back to Stage 1.
Changing Materials on the LPD Dryer
The dryer comes with an innovative and time saving Clean Mode. When this is
selected as soon as the proximity sensor detects that all material has been
removed from the canister or the cycle time has expired, it will notify the
operator by alarm. This allows for the canister to be quickly removed, cleaned
and prepared for a new material.
Canister Removal and Cleaning:
Each canister is easily removed from the central carousel by releasing two
latches.
Once the canister is removed and emptied all material contact surfaces can be
readily accessed for quick and simple cleaning. By turning the canister upside
down operators can access the screen by rotating the retaining plate and then
both the plate and the screen are removed for complete cleaning.
Surge Hopper Removal and Cleaning:
The surge hopper above the dryer is also designed to be quick and easy to
remove. The lightweight hopper includes a shut-off slide gate and can be easily
lifted out. The frame can then be rotated out of the way, allowing access and
removal of the fill valve.
Material Take-off Pan Cleaning:
The material take off pan slides out of position for complete access and
easy cleaning.
Filter Cleaning:
The dryer includes a filter that protects the blower from any carry-over of
dust or fine particles. The filter requires cleaning periodically and this can
be achieved by removal of the quick access panel on the front of the dryer.