Plastic screw conveyors are light in weight, inexpensive to fabricate and repair, corrosion and chemical-resistant and able to withstand high temperatures. They can also handle abrasive wear. Plastics like polyurethane, polyethylene and polypropylene can be injection molded to become these conveying systems. Polyurethane screw conveyors are acid resistant, durable and at times more wear resistant than steel. Polypropylene and polyethylene exhibit a smooth surface, making them easy to clean and sterilize. They are therefore used as a food grade material that will not contaminate edible material and is used in the food and beverage processing industries.
All three of these thermoplastic materials can also withstand high temperatures without melting, burning or chemically changing. Plastic screw conveyors can be easier to handle and replace than other kinds of conveyors, and they can convey loose, granular, powder and pellet materials. The food, chemical and mineral processing, wastewater treatment and construction industries all use screw conveyors made of plastic in plants and manufacturing facilities as components in large processing lines.
Like most screw conveyors, plastic screw conveyors are generally powered by an electric motor. They are available in six, nine or 12 inch diameters and may be any length, which is defined by the amount of space the facilities have. While plastic conveyors are used when impact and abrasive wear is a problem, they do have some limitations. Static electricity may accumulate and produce a spark while plastic screw conveyors are in motion. Therefore, absolutely no combustible or flammable materials may be transported via plastic screw conveyors in order to ensure workplace safety.
All plastic components of screw conveyors – the screw shaft and trough or tubular casing – are manufactured by the injection molding process, where molten thermoplastic resin is forced into a mold, where it takes the shape and hardens. Injection molding is fast, inexpensive and able to produce complex plastic parts. Screw conveyors made of plastic may be three different orientations: horizontal, which transports material on a level plane and often doesn’t require a tubular casing; vertical, which conveys material straight up and down; and inclined, which moves material from one container to another on an angle. Most plastic screw conveyors, however, are modular or portable. They are smaller and can be relocated to anywhere they are needed around a facility.