GB2207366A

GB2207366A - Filter screens

Info

Publication number: GB2207366A
Application number: GB08818124A
Authority: GB
Inventors: Kenneth James Gutteridge
Original assignee: N Greening Ltd
Current assignee: N Greening Ltd
Priority date: 1987-07-31
Filing date: 1988-07-29
Publication date: 1989-02-01
Also published as: GB8818124D0; GB8718157D0

Abstract

A screen (10) particularly for a vibratory screening apparatus for filtering mud during drilling comprises a frame (11) to which are attached a plurality of wedge wires (20) in generally parallel relationship, the wires being connected by cross-members (26) through loops of the wires. The frame also comprises cross members (14,16) and L-shaped end members 30. The frame is mounted on a sub-frame composed of box section and L-section members. <IMAGE>

Description

Title: Screens DESCRIPTION The present invention relates to screens particularly but not exclusively for use in vibratory screening apparatus.

Mud is used in drilling operations, as a lubricant, a sealant to maintain hole pressure, a coolant for the drill and a carrier of cuttings from the bottom of the hole to the surface. The mud usually contains valuable additives so that reclaiming, reconditioning and recirculation of the mud is desirable.

Reclamation is achieved by removing the large cuttings say through a coarse mesh screen and then removing the fine cuttings through a vibrated fine mesh screen and it is with latter that the present invention is particularly concerned.

The fine mesh screens so far used have not been entirely satisfactory as to their capacity and strength and the object of the present invention is to provide a screen to replace existing fine mesh screens.

According to the present invention a screen particularly for a vibratory screening apparatus comprises a frame to which are attached a plurality of wedge wires in generally parallel relationship, the wires being connected by cross-members preferably through loops of the wires.

The wedge wires desirably have a profile width of less than 0.170cm and desirably have a profile depth of less than 0.274cm. Preferred wedge wires are those of profile width of about 0.102cm and 0.137cm and profile depths respectively of 0.164cm and 0.220cm. Typical aperture sizes, i.e. distance between adjacent wires, are from 0.010 cm to 0.100 cm.

The use of wedge wire for making the screens of the invention has the advantage that a greater open area, upto 40%, may be provided compared with a similar size wire mesh screen. Furthermore, wedge wire screens tend to be stronger and so can withstand greater vibratory forces than wire mesh screens, which means that wedge wire screens can be used at higher speeds of operation. The combination of these advantages can, therefore, provide for a more efficient and faster screening operation as well as for longer screen life.

The frame for the screens of the invention preferably comprises spaced longitudinal members, say flat bars or L-section members, possibly also supported on a sub-frame, such as of box section members, located generally parallel to the wedge wires and inwards of the side edges of the screen. The sub-frame preferably comprises spaced parallel elongate members linked by spaced cross-members and having further members extending outwards. The longitudinal members of the frame may be linked by spaced cross pieces and also have extending outwards arms, preferably offset relative to the linking crosspieces. The arms extend towards the side edges of the screen but are preferably short thereof, so that the edges of the screen can be gripped in a vibratory screening apparatus.

Alternatively the screen may be provided with grippable edge members. The wedge wires preferably sit between or alongside the longitudinal members but, if present, on top of the cross pieces and arms to which adjacent loops of the wedge wire are welded. Further longitudinal strengthening bars may be added at or near the side edges of the screen.

The frame members are preferably of steel, especially stainless steel, and connections between members are preferably welds.

At each end of the screens of the invention further stengthening may be provided. Typically L-section members of say mild or stainless steel are welded to each end of the screen. Preferably the L-section member at one end faces inwards and at the other faces outwards.

As well as using the screen in vibratory screening apparatus, they may also be used in static situations.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a screen; Figure 2 is a section on line AA of Figure 1; Figure 3 is an end view in the direction of arrow C of Figure 1; Figure 4 is a section on line BB of Figure 1; Figure 5 is an enlarged view of one end of Figure 4; Figure 6 is an enlarged view of a mid-part of Figure 4; Figure 7 is an enlarged view of the other end of Figure 4; Figure 8 is a plan view of an alternative screen; Figure 9 is a section on line AA of Figure 8; Figure 10 is a section on line BB of Figure 8; Figure 11 is a section on line CC of Figure 8; and Figures 12, 13 and 14 are enlarged views of the ends and mid part of Figure 8 respectively.

Referring to Figures 1 to 7 of the accompanying drawings a mud screen 10 has a frame 11 comprising a pair of spaced parallel longitudinal flat stainless steel bars 12. The bars 12 are linked by a pair of spaced parallel cross pieces 14 also of flat stainless steel welded thereto. Offset relative to the cross pieces 14 and extending outwards from each of the bars 12 are spaced parallel arms 16 also welded thereto.

The outer ends 18 of the arms 16 are sloped upwards. The cross pieces 14 and arms 16 are below the height of the bars 12.

Secured on top of the frame 11 are three sections of wedge wires 20. The wedge wires are looped at spaced intervals and the loops 24 of adjacent wires are connected by cross rods 26 therethrough and through the bars 12. The cross rod ends are peened over for security. The arms 16 are welded near their ends to adjacent loops 24. The spacing between adjacent wedge wires is chosen according to the size of particle separation required. The wedge wires are of relatively small size typically of profile width 0.102cm and profile depth 0.164cm or of profile width 0.137cm and profile depth 0.220cm. Typical aperture sizes range from 0.010 to 0.100 cm and open area % from 6 upto 40.

At one end of the screen 10 is an L-section member 28 facing inwards and at the other end of the screen is an L-section member 30 facing outwards.

The member 28 actually sits in recessed ends of the bars 12 and is welded to the ends of the wedge wire sections. The member 30 is welded to the other end of the wedge wire sections with a supporting strip 32 in the junction thereof.

The ends of both members 28 and 30 are sloped correspondingly to the ends of the arms 16. The arms 16 are actually short of the edges of the screen leaving the edges of the screen clear to be gripped in a vibratory screening apparatus.

The end face of the member 28 has adhered thereto a neoprene rubber or similar strip 36 to act as a buffer during use of. the screen.

Turning to Figures 8 to 14 of the accompanying drawings a mud screen 50 has a rectangular base frame 51 comprising spaced, parallel elongate box section members 52 connected by spaced box section members 54 therebetween and having further box section limbs 56 extending outwardly from each member 52, connections between members 52 and 54 and 52 and 56 being welds.

Welded to the ends of the limbs 56 are upturned L-section members 58 to provide grippable ledges on opposite sides of the screen for securement in a screening apparatus.

The base frame 51 carries elongate L-section members 60 welded thereto parallel to members 52. Two pairs of members 60 actually overlie the members 52, the members 60 being back to back to form an overturned T-section. The other memebrs 60 are secured agianst respective members 58.

The members 60 support three sections of spaced wedge wires 62 parallel to the members 52. The wedge wires are looped at spaced intervals and the loops of adjacent wires are connected by cross rods 64 therethrough. At their ends the cross rods 64 are rivetted over and welded to the appropriate L-section member 60. The spacing between adjacent wedge wires is again chosen according to the size of particle separation required.

At one end of the screen 50 is an L-section member 66 facing omwards and at the other end of the screen is an L-section member 68 facing outwards. One limb 69 of the member 66 provides a flat end face 70 that has adhered thereto a strip 72 of neoprene rubber to act as a buffer during use of the screen. On the inner face of limb 69 near its top is welded a support bar 74 for the wedge wires. The other limb 76 of the member 66 is welded to the ends of members 52 which are undercut for that purpose.

The other L-section member 68 has one limb 80 welded against the ends of box section member 52 and which has a support strip 82 welded thereto and to the ends of the wedge wires.

Tests on wedge wire screens have shown them to be particularly suitable for use in shale shakers such as used on oil rigs for reclaiming mud used for example as a lubricant. Indeed transportation of solids was found to be improved compared with a conventional wire mesh screen. Furthermore, as the screens are more rigid than conventional wire mesh screens stronger vibrations can be used resulting in improved screening.

Claims

1. A screen for a vibratory screening apparatus comprises a frame to which are attached a plurality of wedge wires in generally parallel relationship, the wires being connected by cross-members.

2. A screen as claimed in claim 1, wherein the cross members are through loops of the wedge wires.

3. A screen as claimed in claim 1 or 2, wherein the wedge wires have a profile width of less than 0.170cm.

4. A screen as claimed in claim 1, 2 or 3, wherein the wedge wires have a profile depth of less than 0.274cm.

5. A screen as claimed in any one of claims 1 to 4, wherein the distance between adjacent wires is from 0.010cm to 0.100cm.

6. A screen as claimed in any one of claims 1 to 5, having open area upto 40%.

7. A screen as claimed in any one of claims 1 to 6, wherein the frame comprises spaced longitudinal members located generally parallel to the wedge wires and inwards of side edges of the screen, the wedge wires being in panels sitting between or alongside the longitudinal members.

8. A screen as claimed in claim 7, wherein the frame is supported on a sub-frame.

9. A screen as claimed in claim 8, wherein the sub-frame comprises box section members.

10. A screen as claimed in claim 8 or 9, wherein the sub-frame comprises spaced parallel elongate members linked by spaced cross-members and having further members extending outwards.

11. A screen as claimed in claim 7, wherein the longitudinal members of the frame are linked by spaced cross pieces and also have extending outwards arms.

12. A screen as claimed in claim 11, wherein said outwards arms are offset relative to the linking crosspieces.

13. A screen as claimed in claim 12, wherein said arms extend towards the side edges of the screen but are short thereof, so that the edges of the screen can be gripped in a vibratory screening apparatlls.

14. A screen as claimed in any one of claims 1 to 12, wherein the screen is provided with grippable edge members.

15. A screen as claimed in any one of claims 1 to 14 having at each end thereof L-section members for further strengthening.

16. A screen as claimed in claim 15, wherein the L-section member at one end faces inwards and at the other end faces outwards.

17. A screen for a vibratory screening apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 7 or Figures 8 to 14 of the accompanying drawings.