Filtration Services Ltd, a supplier of rotary drum vacuum filters for the bulk separation of solids from liquids has developed a unique precoat automatic knife advance system [AKAS™] used for cutting precoat.  Precoated rotary drum vacuum filters [RDVFs] are used in many industries for a wide variety of applications.  They are used to ensure that the filtered liquid is clear, bright and, above all, solids-free.  Precoat, being diatomaceous earth, perlite or cellulose based, is a sacrificial filter medium used on the precoated rotary drum vacuum filter and a constant, yet necessary, expense to the operation of the filter.  Using precoat more efficiently has a number of benefits which include reduced operating costs, longer filtration cycle times, increased productivity and improved yields.


Argent Energy Filter


Dr Andrew Walker, Managing Director of Filtration Services Ltd, says “We developed the first AKAS™ version back in 1996 for a major pharmaceutical company to improve the reliability and operation of their precoat knife discharge system.  The first AKAS™ was limited to a mere 25 microns per drum revolution but this was still a significant improvement on the existing electro-mechanical knife advance systems.  We’re now onto the third generation ‘G3’ control system and are constantly looking for ways to make further improvements and enhancements.  All of our new precoat rotary drum vacuum filters use this technology and we have retrofitted AKAS™ controls onto many other rotary drum vacuum filter marques including Dorr-Oliver, Paxman, Eimco, Stockdale, Alfa-Laval and Lundin.

The AKAS™ uses synchronous digital technology to control the operation of a precoat discharge assembly in increments of 5 micron; about 1/20th the thickness of an average human hair.  This level of control allows the knife advance rate to be finely adjusted and optimised for each application.

Set up and operation of the AKAS™ is quick and easy via the touchscreen interface, with four built-in ‘recipe’ selections for switching between preset values.  The control unit has the capability for local or remote recipe selection depending upon the site specific requirements.

A recently added feature to the AKAS™ is the cut-delay facility.  For applications where the solids content is very low it may not be necessary to cut the precoat on each drum rotation.  For these applications, the knife advance can be paused for several drum revolutions before cutting.  This function, combined with the low incremental knife advance rate, means that nett cut rates of 0.5 micron per drum revolution are possible.

Contact Filtration Services Ltd for more information on cutting precoat, or to find out more.