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Our machines are supplied as stand-alone plant, or as a intregrated "turn-key" system for a new or existing recycling or waste processing facility. For large systems we are typically commissioned to carry design studies.

Sink Float Tanks

The HKS series of float sink tanks are manufactured by Rotajet Systems Limited in the United Kingdom, the machines are modular so can be used as stand alone or part of a Rotajet plastic recycling line. The float / sink concept relies on the specific gravities of the materials processed relative to the specific gravity of the base solution in the tank. The materials with a specific gravity higher than that of the base solution will sink and those with a lower specific gravity will float. The specific gravity of the base solution can adjusted with the addition of chemicals, this allows users to separate a number of different polymer types using a series of tanks.

The HKS series are manufactured from 304 stainless steel, and fitted with infeed screws, bottom screws, rotating drums, spray bars and off take dewatering screws.



Key Benefits 

Infeed Screws:

Shredded infeed material is force fed into the tanks using three screws, the product is forced under the surface of the solution, this ensures the material is fully “wetted out” to ensure maximum separation of polymer streams.


Bottom Screw augers:

The sinking fraction is removed from the bottom of the tank using screw augers, for the larger machines we fit three and the smaller units one. The material is fed along the base of the tank and transferred into a elevated transfer screw, the material can then be fed into dryers further float sinks etc…or waste skip.


Rotating drums:

Six rotating drums are fitted at the top of the tanks; the drums are used to resubmerge the floating fraction and also transfer the product along the surface of the tank to the outfeed.



Spray bars:

Spray bars are fitted along the surface of the tank between the rotating drums; filtered solution is pumped from the spray bars onto the surface of tank / floating fraction. The agitation of the spray breaks floating fractions contaminated with trapped sinking fractions, dirt, dust etc….


Take off dewatering screw:

The floating fraction is transferred from the surface of the tank into the off take dewatering screw, the drained water in fed back to the tank, and material discharged for further processing.


Additional extras:

  • Automatic chemical analysis 
  • Automatic chemical dosing 
  • Additional filtration
  • Frost protection
  • Automatic infills
  • Integrated feeding systems for difficult products



Model Length Width Height Volume KW kgs/hr
HK540 5500 2500 3300 7500 10 500-800
HK550 7000 3500 4250 20000 15 1500
HK570 10500 4500 5500 40000 20 3000

Additional Information:

Rotajet also manufacture and supply washing plant, trommels, conveyors, shredders, bagging equipment etc….