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Raining Bucket Contactors/Graesser Rotors

rotor close up on drive end Rotor buckets202 rotor close up on non drive end02 rotor two units side by side rotor bearing close up02 7764-21
7765-3 7765-10 rotor14 stubshaft3 7765-60 7765-8

In Association with: Biotechna Inc. USA - W. H. Capper (UK)  Ltd are the only approved manufacturers of Contactors, worldwide. This is  achieved by the provision of all process technology by BIOTECHNA Inc., USA for  any application of the "Graesser" Contactor or “rotors”. The Complete mechanical design thereon is provided by WIDNES ENGINEERING (BUSCHING) Ltd, who have been involved  with these units since their inception by Mr John Coleby of R. Graesser Ltd over  50 years ago, and have been actively involved in progressive development thereon  to meet customer's requirements.

 The success of this principle lies in the  gentle and repeated dispersion and simultaneous coalescence of the two phases in  each, and that this happens at right angles to the main con- or counter-current flow along the length of the machine.This avoids the violent mixing or pumping  action associated with most other mixer/settlers and mechanical columns.

It also  provides excellent compartment segregation with the minimum of back mixing:-  unlike that found in static, mechanical or pulsating type columns.

With low maintenance becoming an ever increasing demand on the modern plant, Contactors excel in this area with up to 95% availability (5% down time) during its lifetime. With some processes up to 97% efficiency has been known. This is a proven technology developed over years with many units still in operation worldwide, for a number of decades. With an impressive track record for reliability & maintainability, the Contactor is more than a match for conventional methods of separation such packed towers.

Key Benefits

  • Suitable for many liquid/liquid/suspension, or solid applications, where slurries of up to 60%  solids have been accommodated by solvent extraction & similar mass transfer  operations.
  • With its multi-stage performance in one single unit of equipment,  it is both economical in operation and offers a considerable saving in  valuable plant space.
  • Very low power consumption makes for extremely low operating low operating costs.
  • Maintenance & supervision costs are minimal when in  operation.
  • High flexibility gives little cause for concern  should spasms of solute feed occur.
  • Easy modernisation of existing old technology plants are readily achievable.
  • Initial competitive cost compared to other methods ensures lower capital outlay with a rapid recovery of investment.
  • Being environmentally protective, spent process  liquors may be re-cycled in many cases into re-usable states, giving economy, reduced emissions and elimination/disposal of difficult materials, having a positive impact on the environment


BS EN ISO 9001 Approved. ASME Authorized Manufacturer. Welding to BS EN ISO 15614 & ASME IX. Radiography in Accordance with BS EN ISO 1435 & ASME V.