Sterling SDA AP-1 Functional Description, Models Covered in This Manual, General Description

Chapter 2: Functional Description

2-1 Models Covered in This Manual

This manual provides operation, installation, and maintenance instructions for 600-3000 cfm Large Dehumidifying Dryers with AP1 control. These dryers are available with electric heaters or gas burners. Gas dryers are indicated with a “G” in the model number. Model numbers are listed on the serial tag. Make sure you know the model and serial number of your equipment before contacting the manufacturer for parts or service.

Our dehumidifying dryers are designed to generate heated, dehumidified air at carefully controlled temperatures for use in closed-loop plastic drying systems. Dehumidifying dryers are sized to meet the specific requirements stated by the Customer at the time of purchase.

2-2 General Description

Moisture removal from hygroscopic (moisture attracting) plastic pellets is an essential step in the manufacture of high-quality plastic products.

Our Dehumidifying Dryers are used by the plastics industry to generate very low dewpoint air that is heated to a controlled temperature for drying plastic pellets and regrind.

The drying system consists of a dry air source and drying hoppers with process heating controls. The dry air source controls two primary sub-systems, the process air and the regeneration circuit. Each dryer has a left and a right desiccant bed so that one bed can regenerate while the other is in use. 2000-3000 cfm dryers feature two sets of desiccant beds, for a total of four desiccant beds.

The drying system can be configured for one drying hopper or for as many as 20 hoppers. The process air heater can be located on the dryer or on each individual drying hopper. Heaters that are located on the drying hoppers can be set up with their own independent controls or can be controlled centrally using the main dryer controller.

Specifying a Drying System

There were many variables considered in the selection of your drying system, including: type of materials, residence time, throughput of the extruder or injection molding machine, ambient air moisture and temperature, and the altitude at the processing site. Should your operating environment change, we can advise you on necessary equipment, process time and temperature modifications.

What is Desiccant?

Desiccant is a material that attracts and holds (absorbs) water from the air. The desiccant our dryers use is a synthetic crystalline metal aluminosilicate that is blended with a clay binder and formed into beads.

Absorbed water is driven from saturated desiccant by heating it to a high temperature (reducing the desiccant's capacity to hold water) and forcing air through it. This moisture removal process is called "regeneration".

The Closed Loop Drying System

These dehumidifying dryers force hot, dry air through the resin in the drying hopper, where the air picks up moisture from the material and is drawn back to the dryer. In the dryer,

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