Pelletizers are process machines that form materials into pellets for use in subsequent operations. There are many different types of products. Examples include disc pelletizers, drum pelletizers, and strand pelletizers.
Disc or pan pelletizers are continuous-process machines which add raw materials to a large process vessel (the pan) and then spray the particles with water. As the pan rotates, the moistened materials form intermediate-sized particles and then larger agglomerations which exit the equipment. Drum pelletizers produce dense, large-diameter pellets for disposal, recycling or transportation. They have a rear-mounted, auger feeder and a drum-shaped process chamber. Strand pelletizers have bolt-on knives and quick-change gears for processing materials such as engineering plastics. They feed extruded strands of material into a rotary, cross-cutting head which reduces the stock into pellets of uniform size. Pelletizing systems use wet or dry processes. Pelletizers with water jets and a water-slide design are designed to contact and cool the process material. After water jets spray the material, the excess water drains through a trough. The feed roll then moves the process material to a cutting area with bolt-on knives. With water-slide pelletizers, the pellets are bathed with water and then dried with a centrifugal water separator. In dry-cut systems, the water is removed before the strands enter the cutting chamber.
Although water-slide designs are popular in marine salvage operations, dry-process pelletizers are used to cut and cool pellets of temperature-sensitive materials such as engineering plastics. Examples include acrylonitrile butadiene styrene (ABS), high density polyethylene (HDPE), low density polyethylene (LDPE), nylon, polyolefin, polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Some pelletizers are hydraulic. Others are electric-powered machines with two motors. One motor powers the feed roll and the other moves the rotor. Typically, capacity or production rate is measured in pounds per hour (lbs / hr). Other specifications may vary by pelletizer type. For example, disc pelletizers and rum pelletizers carry specifications for diameter, depth, length, width, height and shipping weight. Parameters for strand pelletizers include working width, strand rating, standard strand velocity, standard rate per strand, optional strand velocity, optical rate per strand, motor size, maximum rotor speed, voltage, type of drives, and number of cutting edges.