ZA200208447B

ZA200208447B - System and method cleaning a screen.

Info

Publication number: ZA200208447B
Application number: ZA200208447A
Authority: ZA
Inventors: Oliver Francois Dominiqu Jason; Vivian Andrew Rocher
Original assignee: Multotec Mfg Pty Ltd
Priority date: 2000-04-20
Filing date: 2002-10-18
Publication date: 2005-05-13

Description

SYSTEM AND METHOD FOR CLEANING A SCREEN

Technical Field

This invention relates to a system and a method for cleaning a screen.

Background Art

The use of screens, having apertures of a fixed size for sorting/separating particles by size and/or de-watering slurries and/or screening out trash or oversize particles, is widely known.

Considerable problems are experienced with blinding of apertures of these screens, as a result of the lodging of particles in the apertures, and consequently reducing their effectiveness.

It is accordingly an object of this invention to provide a system and a method for de-blinding a screen.

Disclosure of the Invention . According to a first aspect of the invention, there is provided a system for cleaning a screen, having multiple apertures, the system characterised by including at least one high pressure nozzle unit,

having a nozzle, capable of generating an ultrasonically stimulated, high velocity fluid jet, the nozzle unit being positioned operatively relative to a screen to direct the fluid at the apertures to dislodge the particles blinding the apertures during a screening process.

The nozzle may be a rotating nozzle, capable of rotating about an axis at an angle to the screen.

The nozzle unit may be movable relative to the surface of the screen.

Preferably, the nozzle unit is movable in an oscillatory manner substantially across the screen.

The nozzle may have a diameter of between 0.3 mm and 1.5 mm and preferably between 0.889 mm and 1.143 mm.

The nozzle unit may be of the type made available to the South

African market under the names “Kranzel Dirt Killer”, “Kranzel

Turbo Killer”, or a nozzle unit similar thereto.

The fluid supplied to the nozzle may at a pressure between 0.1 and 12

MPa. The pressure may be constant, alternatively pulsating.

The fluid may be supplied to the nozzle at a flow rate of between 8 litres/min and 15 litres/min and preferably 12 litres/min.

The nozzle unit may be mounted on a spray bar. The spray bar may be in the form of a pipe, having an opening communicating fluidly with the nozzle unit. The spray bar may be suspended operatively above the screen and movable in a plane, extending substantially parallel to the screen, so as to render the nozzle capable of directing the jet at adjacent apertures across the screen.

The spray bar may be spaced above the screen such that the nozzle is at least one complete ultrasonic wavelength, alternatively, multiples of complete wavelengths from the screen. Preferably, the spray bar may be spaced above the screen such that the nozzle is between 200mm and 500 mm, and more preferably 340 mm, from the screen.

The spray bar may be suspendable between tensioned cables, fixed rails, chains, or some other suitable mechanical suspending device and moved by manipulation of this device. The spray bar may be provided with a number of nozzle units, the spray bar serving as a manifold.

The rotation of the nozzle may result in a circular sprayed zone, having a diameter at the screen of approximately 160 mm.

The screen may include a number of screening panels.

According to a second aspect of the invention, there is provided a method for cleaning a screen for particulate material, the method including the steps of spraying an ultrasonically stimulated fluid jet at a screen; rotating the jet about an axis at an angle to the screen; and moving the jet substantially across the surface of the screen to dislodge particles blinding apertures during a screening process.

Brief Description of the Drawings

The invention will now be described by way of non-limiting example 5 only, with reference to the accompanying drawing illustrating a perspective view of a system for cleaning a screening panel in accordance with the invention.

Best_Mode of Carrying Out the Invention

A system (1) for cleaning a screen (2), in accordance with the invention, is illustrated in the accompanying drawing. The system (1) includes two nozzle units (3), the nozzle units (3) being supplied with high-pressured fluid by means of a supply pipe (4). The nozzle units (3) are capable of generating an ultrasonically stimulated, high velocity fluid jet (5).The nozzle units (3) are positioned so as in operation to direct the jet (5) at the apertures of the screen (2), so as to dislodge particles blinding the apertures during a screening operation.

The nozzle units (3) each include a rotating nozzle (not shown), which rotates about an axis (7) at an angle to the screen.

The nozzle units (3) are of the type available to the South African market under the name “Kranzel Turbo Killer” or “Kranzel Dirt

Killer”.

The nozzle (not shown) has a diameter of between 0.889 mm and 1.143 mm.

The fluid is supplied to the nozzle at a pressure between 0.1 and 12

MPa. The pressure is constant.

It is however envisaged that the pressure could be pulsating, typically generated as a result of pressure fluctuations associated with the use of certain types of pumps.

The fluid is supplied to the nozzle at a flow rate of about 12litres/min.

0

The nozzle units (3) are mounted on a spray bar (8) in the form of a pipe, having corresponding openings communicating fluidly with the nozzle units. The spray bar (8) serves as a manifold to the nozzle units (3).

The spray bar (8) is suspended above and movable in a plane, extending substantially parallel to the screen (2), so as to render the nozzles capable of directing the jets at adjacent apertures across the screen.

The spray bar (8) is suspended between a support-and-movement mechanism (9), and is moved by manipulation of this mechanism. It 1s envisaged that this mechanism (9) could be tensioned cables or chains.

The spray bar (8) is spaced from the screen (2) such that the distance between the nozzle and the screen is one complete ultrasonic ) wavelength, or about 340 mm from the screen or alternatively, * multiples of complete wavelengths from the screen.

With the nozzles (not shown) mounted at the desired distance of one wavelength or about 340 mm from the screen (2), the rotation of the nozzles results in sprayed zones having diameters (10) at the screen (2) of approximately 160 mm. It is envisaged that, to cover the full width of some screens with the spray bar moving in a linear fashion along the length the screen, it would be necessary to have multiple nozzle units (3) mounted to the spray bar.

It is envisaged that the movement created by the mechanical suspension device could also be from side to side.

Many screens in use consist of a number of screening panels.

In use, the force of the jets (5), combined with the pulsating effect produced by the pump (not shown), and depending on the nozzles used, the ultrasonic velocity of the jets, dislodges particles blinding the apertures of the screen (2).

It is envisaged that in an alternative embodiment, the screen could move in an oscillatory manner relative to a substantially stationary nozzle unit.

It will be appreciated that numerous embodiments of the invention could be performed without departing from the scope of the invention as defined in the claims below. *

Claims

1. A system for cleaning a screen for particulate material, the system characterised by including at least one high pressure nozzle unit, capable of generating an ultrasonically stimulated, high velocity fluid jet and directing the jet at a screen so as to dislodge particles blinding apertures during a screening operation.

2. A system for cleaning a screen as claimed in claim 1, characterised by the nozzle being capable of rotating about an axis at an angle to the screen.

3. A system for cleaning a screen as claimed in claim 1, characterised by the nozzle unit being movable relative to the surface of the screen.

4. A system for cleaning a screen as claimed in claim 3, characterised by the nozzle unit being movable relative to the screen in an oscillatory manner substantially across the screen.

5. A system for cleaning a screen as claimed in claim 1, characterised by the nozzle having a diameter of between 0.3 mm and 1.5 mm.

6. A system for cleaning a screen as claimed in claim 5, characterised by the nozzle having a diameter of between 0.889 mm and 1.143 mm.

7. A system for cleaning a screen as claimed in claim 1, characterised by being operable with a fluid supplied to the nozzle unit at a pressure of between 0.1 and 12 MPa.

8. A system for cleaning a screen as claimed in claim 7, characterised by being operable with the fluid pressure being supplied to the nozzle unit in a constant manner.

9. A system for cleaning a screen as claimed in claim 7, characterised a by being operable with the fluid pressure being supplied to the nozzle unit in a pulsating manner.

10.A system for cleaning a screen as claimed in claim 1, characterised by being operable with the fluid being supplied to the nozzle at a flow rate of between 8 litres/min and 15 litres/min.

11.A system for cleaning a screen as claimed in claim 1, characterised by being operable with the fluid being supplied to the nozzle at a flow rate of 12 litres/min.

12.A system for cleaning a screen as claimed in claim 1, characterised by the nozzle unit being securable to a spray bar.

13.A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being in the form of a pipe, having an opening for communicating fluidly with the nozzle unit.

14. A system for cleaning a screen as claimed in claim 12, a characterised by the spray bar being suspendable operatively above the screen and movable in a plane, extending substantially parallel to the screen, so as to render the nozzle unit capable of directing the jet at adjacent apertures in the screen.

15. A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being locatable above the screen such that the nozzle is one complete ultrasonic wavelength from the screen.

16.A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being locatable above the screen such that the nozzle is a multiple of a complete ultrasonic wavelength from the screen.

17.A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being supportable in position above the screen by a mechanical device, and movable across the screen by manipulation of the device. )

18.A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being supportable in position above the screen between two tensioned cables, and moved by manipulation of the cables.

19.A system for cleaning a screen as claimed in claim 12, characterised by the spray bar being provided with a number of nozzle units, the spray bar serving as a manifold.

20.A system for cleaning a screen as claimed in claim 2, characterised by the rotation of the nozzle resulting in a circular sprayed zone, having a diameter at the screen of approximately 160 mm.

21.A method for cleaning a screen for particulate material, the method characterised by including the step of spraying an ultrasonically stimulating fluid jet at a screen so as to dislodge particles blinding apertures during a screening operation.

22. A method for cleaning a screen as claimed in claim 21, characterised by including the step of rotating the jet to cover a circular spray zone on the surface of the screen.

23.A method for cleaning a screen as claimed in claim 21, characterised by including the step of moving the jet substantially across the surface of the screen. : )