For all precoat knife discharge rotary drum vacuum filters (RDVFs) it is important that the knife advance system operates accurately and steadily so that the optimum usage of precoat material can be attained. A high advance rate causes the knife to remove too much of the precoat bed as well as the surface filter cake; this is wasteful of precoat material and reduces the overall filtration cycle time unnecessarily. Too slow an advance, and the surface filter cake layer does not get fully removed, the precoat surface is not refreshed and the overall filtration rate and, therefore, throughput decreases rapidly.
Filtration Services Ltd has developed a precoat knife system that regulates the rate of knife advance to the speed of rotation of the drum. This ensures that the knife advances synchronously with the rotation of the drum and removes an even thickness of filter cake at all times.
An electronic pulse is received by the control on each complete drum rotation. This initiates the 'advance' signal to the knife drive stepper motor. Any variation in drum speed, due to changes in material filterability or desired throughput, is monitored and the knife advance compensates accordingly. The interaction between the drum and knife assembly ensures that the minimum amount of precoat material is wasted and that filtration cycle times and throughput rates are maximised.
The knife advance control panel incorporates a touch-screen HMI with the following features:
- Easy commissioning
- Easy knife advance / retract operation
- Numerical and graphical display of the position of the precoat knife relative to the drum
- Easy setting of the knife advance rate (in increments of 5 microns per drum revloution)
- Knife advance delay option (of 2 to 10 drum revolutions)
- Forward and reverse limit alarms
- Motor frequency tuning facility
- PIN number 'lock' facility to prevent unauthorised changes to settings
The maximum knife travel is governed by 'forward stop' and 'reverse stop' limit switches which are interlinked though the control panel. The control panel can be located close to the RDVF if required, allowing the operator to regulate the position of the knife.
This latest design of knife discharge system has been developed following many years of practical experience with earlier mechanical, hydraulic and electro-mechanical assemblies. This knife advance system can be adapted to suit most existing precoat assemblies.
Here at Filtration Services Ltd, we utilise the latest design and engineering techniques to provide high quality solutions for all areas of the filtration industry, and would be happy to discuss all of your requirements in more detail.
Technical Data
- Control panel input voltage 110 or 240VAC (single phase)
- Control panel output voltage 24VDC
- Internal 24VDC power supply
- IP65 control panel enclosure
- IP65 forward and reverse limit switches
- IP65 drum limit switch
- IP65 stepper motor
- 'Sealed for life' gearboxes
The standard input voltage to the control panel is 110VAC. The panel can be supplied for use with 240VAC but this must be specified at the time of ordering. Cabling to the control panel, and between the control panel, limit switches and stepper motor are the responsibility of the client.
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