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What are overlength separators used for?

During the production of plastic pellets, excess lengths (“longs”) occur in the production process during start-up and shut-down, which interfere with the further processing of the pellets. The overlength separator is part of our range of screening machines for the chemical, pharmaceutical and food industries and helps you to screen these overlengths from the desired pellet size. In the jargon of processing technology, this involves separating the bad granulate from the good granulate. The overlength separator is a special form of control and protective screening for the separation of overlong material parts. If further screening of the granulate is required in addition to pure overlength screening, the use of a granulate screening machine is recommended.

Problem with screening plastic granulate

Optimum processing technology for plastic pellets

When screening granulates, a different procedure must be used than when screening other products (e.g. recycled material or biomass). As the diameter of the granulate is often the same size, the excess lengths end up in the fine granulate. Either the wrong processing technology (screening technology) was used or the screening surface of the screening machines did not meet the requirements of the granulate. In addition, the use of strong vibrations from the vibration motors is counterproductive, as this causes the granulate to “bounce”. This increases the likelihood of it falling unintentionally through the perforation to the fine granulate during the screening process.

Functionality of overlength separators

How do overlength separators work?

An overlength separator is used to counteract the above-mentioned problems in the granulate production process. As the diameter of the pellets is the same, the separation into good and bad pellets must be carried out using the pellet length. To ensure that the excess lengths can be removed from the pellets with a sharp cut, it is necessary for the pellets to slide over the screen surface as flat as possible. We support you with machine dynamics that are precisely tailored to your product. For example, we ensure that your pellets are separated efficiently through the vibration parameters or the angle of inclination of the machine. The frequency of movement is also crucial: the faster the frequency, the more likely it is that the granules will bounce and find a way to the good granules. A low frequency of the vibration motors is therefore necessary to avoid this “bouncing effect” and the erection of long granules.

Advantages of using overlength separators

  • Efficient and economical processing technology for plastic pellets
  • High selectivity for optimum pellet quality
  • Gentle screening process and minimal abrasion of the plastic granulate
  • Easy cleaning of the overlength separator
  • Optimum adaptability to your (changing) products
  • Avoidance of setting up excess lengths
  • Heavy “bouncing” of the granulate is avoided
  • High efficiency and quality in granulate production