Screening method and apparatus

1. An apparatus for use in screening a liquid and solids mixture feed, the apparatus comprising:

a conduit, including a screening portion and formed and arranged to divide a liquid and solids mixture feed flowing through the conduit into a first, cleaned stream comprising liquid and solid particles of below a selected size limit, and a second, concentrated, stream comprising liquid, and solid particles above the selected size limit;

wherein an outlet for the second concentrated stream from the screening portion is in the form of a weir assembly;

the weir assembly comprising:

a trough in fluid communication with said screening portion and having a bottom wall disposed at a lower height than the bottom wall of the screening portion; and

an outlet over which the second concentrated stream flows in use.

2. An apparatus according to claim 1 wherein the conduit is a pipe or channel and the screening portion is a screen mesh or other filter material that replaces part of a conduit wall.

3. An apparatus according to claim 2 wherein the screen mesh or other filter material replaces an upper or a lower portion of a wall of a substantially horizontally disposed conduit.

4. An apparatus according to claim 1 wherein a baffle is provided above the trough of the weir assembly and disposed across the horizontal direction of flow of the second concentrated stream in the screening portion.

5. An apparatus according to claim 4 wherein the baffle comprises or is a plate directed downwards towards the trough and disposed across the horizontal direction of flow of the second concentrated stream.

6. An apparatus according to claim 4 wherein the baffle extends downwards at least to the height of the bottom wall of the screening portion.

7. An apparatus according to claim 4 wherein the baffle extends into the trough of the weir assembly.

8. An apparatus according to claim 1 wherein the weir outlet is defined by a wall over which the second concentrated stream flows.

9. An apparatus according to claim 8 wherein the height of the weir outlet is adjustable.

10. An apparatus according to claim 1 wherein the weir outlet is in the form of an orifice that is adjustable in cross section area.

11. An apparatus according to claim 1 wherein the pressure in the conduit is variable by adjusting the fluid head at an inlet to the conduit or by providing a feed to the conduit by means of a pump that can provide variable pressure to the system.

12. An apparatus according to claim 1 wherein the weir assembly is formed as a closed to atmosphere fluid path with a portion of conduit to provide a siphon effect in use.

13. An apparatus according to claim 1 further comprising vibratory means.

14. An apparatus according to claim 13 wherein the apparatus is mounted in a vibrating basket or is itself mounted on resilient members and is directly vibrated.

15. An apparatus according to claim 1 including a downwards directed inlet end for the conduit followed by a generally horizontally disposed screening portion that has a screen mesh replacing a portion, for example an upper or a lower portion of conduit wall.

16. An apparatus for use in screening a liquid and solids mixture feed, the apparatus comprising:

a conduit, including a screening portion having a screen disposed on a horizontally disposed bottom wall and formed and arranged to divide a liquid and solids mixture feed flowing through the conduit into a first, cleaned stream comprising liquid and solid particles of below a selected size limit, and a second, concentrated, stream comprising liquid, and solid particles above the selected size limit;

wherein an outlet for the second concentrated stream from the screening portion is in the form of a weir assembly;

the weir assembly comprising:

an outlet over which the second concentrated stream flows in use; and

wherein the bottom wall of the screening portion in advance of the weir is in the form of a solid plate.