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 Drying
Typically 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.
Side-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.
Since 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 Stress
Long 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.
Additional 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 Controller
The 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.
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.
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 212°F (100°C) to 133°F (56°C). 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.
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.
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.
LPD 100 (LPD 12)
Standard version max.
0.32 cu ft
1.1 cu ft
2 cu ft
Packing dim. (LxWxH)
Total Power Supply
3.47 kW/16 A
3.47 kW/16 A
6.96 kW/20 A
6.96 kW/20 A
7.7 kW/30 A
7.7 kW/20 A
Compressed air requirement
6 - 8 bar
6 - 8 bar
6 - 8 bar
* US voltage: 480, Europe / Asia voltage: 400
Final Moisture % *
Cycle Time (Min.)**
PET (Molding Grade)
PET (Preform, Ext.)
Please note the following:
Final moisture content as recommended by the raw material manufacturer.
Recommended cycle time is based on average initial moisture content. For high initial moisture content cycle time should be extended 5 minutes. When in doubt please contact Maguire service.
Drying temperature as recommended by the material manufacturer.