INTRODUCTION TO THE HIGH FREQUENCY SCREEN
The HIGH FREQUENCY SCREENER is a very specialized unit, whereby the operator can have access to adjusting the following variables and advantages, directly related to the performance, namely:
- The downhill angle of the screen box, if fitted with that facility.
- The speed of the Vibro Motors can be altered through the Variable Speed Drive Supplied.
- The aperture of the screen decking. Steeper downhill angle of the screen box requires a larger aperture because of the velocity of the material over the deck. A shallower angle requires an aperture closer to the chosen cut point.
- A quick change system to replace the screen media.
- Can be fitted with a dust cover, if so required.
OPERATION AND MAINTAINANCE
- The Rocking Beams impact directly onto the screen cloth which is tensioned through a spring loaded mechanism, thus maintaining a constant tension onto the screen media. In the early stages the cloths expand and stretch and this adjuster takes care of that, however do check and tension if need be.
- The method of Tensioner adjustment is as follows, refer to the diagrammatic sketch attached 13-06-MC3/GA1.
- To change the screen cloth, slacken the tensioner, one person either side of the screen box, remove the old screen cloth. Replace with the new one and retension.
- The Variable speed motors work well between 1800 and 2300 rpm, and the operator can adjust them accordingly.
- The motors must all run in the same direction at the same speed. The speed of each is displayed on the VSD read out.
- See the electrical data section for more information on the VSD adjustment.
- It should be noted that the Bucker rubbers on the rocking beams are a wear item and literally do all the work. They do wear down and have to be replaced from time to time.
- It is important to make sure the in-feed material is spread over the width of the screen
- Keep the bed depth of the product to be screened as low as possible to the screen cloth. The velocity of the material over the deck varies from 800m/hour to 2000m/hour depending on the downhill slope angle of the screen box.
The screeners have rubber isolators fitted to the support frame stubs, and to be supplied by the client, are the ‘Bellows’ that are fitted around the inlet and outlet chutes. This can be from a Linatex type rubber, or similar soft rubber, that is wrapped around and strapped to inlet and outlet chute work, to create a dust seal, should this be required.
This then isolates the screener from the structure.
The High Frequency screener weighs ±1500kg, for the 1500 x 2500mm screen box.
Static vertical is 2 x Weight, or 7350N per point.
Dynamic Horizontal is 0.2 x Weight, or 735N per point.
- All motors should run at the same speed and same direction.
- The screen is fitted with a variable speed drive, one for each pair of motors.
- The motor speed of each rocking beam can be individually adjusted, and generally work best between 1800 and 2400rpm.
- The attached information from the instruction booklet shows adjustment and set up procedures.