MXPA06007758A - Improvements in and relating to sifting screens - Google Patents

Abstract

A frame over which woven wire mesh is to be stretched and secured to form a sieving screen and which can be used to screen solids possibly from drilling mud recovered from down-hole when drilling for oil or gas. The frame comprises a rectilinear moulded plastics frame having edge regions by which it is secured in place in a shaker. Within the frame is a plurality of rectilinear windows formed by an orthogonal array of intersecting ribs (75,77,fig 7) also of moulded plastics material. Some of the ribs are internally reinforced by a structure comprising two spaced apart layers of orthogonal intersecting spaced apart wires, running parallel to the length and breadth of the rectilinear shape of the frame within the ribs to increase their rigidity. The edge regions of the frame are reinforced internally by metal box-section members 78,80(82,84) joined at their four corners and defining perimeter reinforcement, and the ends of the wires are secured to the box-section members 78,80(82,84). The latter are encapsulated in the same plastics material from which the orthogonal array of intersecting ribs are moulded. Alternate ribs are not reinforced with wires, and the non-reinforced ribs only extend partway between the upper and lower faces of the frame. Lengths of wire bent to form spacers and adapted to fit between upper and lower wires of the rib reinforcing structure, are joined to the upper and lower wires so as to extend therebetween and maintain the desired separation of the two layers of wires 86,88 during the plastics encapsulation/moulding process.

Description

IMPROVEMENTS IN AND WITH REGARD TO SCREENING SCREENS Field of the Invention This invention relates to sieves or screen sieves that are placed in vibrators, which are used to separate the solids from the liquids, and in particular, they are used to separate solids from liquid drilling muds raised from the bottom. of drilling when drilling for oil or gas. BACKGROUND OF THE INVENTION Historically, the screens have been constructed from sheets of woven wire mesh that is stretched and secured in metal frames using a polymer adhesive. Normally, the frames are of a generally rectangular shape and define one or more rectangular openings on which the mesh or wire mesh is stretched. Normally, two or more layers of wire cloth, which have different fabric sizes, have been secured in each metal frame. The tensions in the warp and weft wires of a fabric are usually larger than the corresponding warp and weft wire tensions in the other fabric. Shapes of the frame This type of construction had the tendency to REF. 173846 originate relatively heavy screens and because they are normally handled by man in position, a new frame design was introduced some years ago by the Applicant Company. This was built largely from the GRP polymer molding in which the wire frame is included during the molding process in order to reinforce the final structure and introduce sufficient rigidity not only to contain and preserve the stresses in the wire fabrics, but also to ensure that the frames are not deformed under the weight of the relatively dense suspension that constitutes the drilling mud and due to the increase of solids on the screen in use. This screen design was ideally suited for vibrators such as for the VMS range of vibrators supplied by Rig Technology Ltd., of Aberdeen, Scotland, UK. The performance of the shaker or vibrator screen is imposed at least in part by the area of the screen cloth on which the drilling mud is deposited. Because the area of each rectangular frame was imposed in part by the maximum allowed weight of the final screen, filtering areas larger than the areas of a single screen were created by placing two or four screens on an edge-to-edge support in a rigid rectilinear basket that has edge supports on which the edges of the screens are supported. The screens were held in place by clamps and, preferably, an inflatable clamping mechanism was used in order to fix the edge of the screens on the edge supports of the rigid basket. The inflatable fixture also ensured a good watertight seal to the passage of the liquid around the edges of the screens. Other vibrators have been developed, which accommodate larger but smaller well-supported screens, and it has been proposed to build these screens using GRP reinforced wire cloth racks, although after testing prototypes it was found that they do not have enough stiffness to meet in the countryside. In particular, GRP wire-mesh screen screens of larger area were observed in shaking or violent vibration around the center of the unsupported extension. This caused the screen to separate from the edge supports in which it must remain sealed at all times of use. This allowed the suspension to deviate from the screen and fall into the sludge trap reserved for filtered liquids. In addition to the shaking of the edge regions of the screen on the edge supports, damage occurred in the bottom of the screen frame. In addition, the excessive shaking caused a considerable splash of the suspension on the walls of the basket and on the floor on which the vibrator was mounted. Apart from the loss of relatively expensive drilling muds, the chemicals that make up the sludge do not have to be discharged into the sea.

Therefore, any type of splash could cause environmental contamination and serious punishments for the operators of the drilling equipment if any of these spills were not collected and discarded correctly, all of which increases the cost of processing and recovery of the spills. sludge at the bottom of the hole. Therefore, an object of the present invention is to provide an improved form of a frame construction of a relatively light weight that is of sufficient stiffness so that it does not shake or vibrate excessively in use and that may extend into more Large screening screens than GRP frame screens reinforced with wire produced previously. SUMMARY OF THE INVENTION According to one aspect of the present invention, a frame on which the woven mesh or fabric will be stretched and secured to form a screening screen that can be used to separate or screen the solids from the drilling mud recovered from the bottom of the perforation when drilling for oil or gas, comprises a molded plastic rectilinear frame having edge regions in which the frame is secured in place in a vibrator and which 'defines a plurality of rectilinear windows formed by an orthogonal series of intersecting projections also of molded plastic material, wherein the projections are internally reinforced by a structure comprising two separate layers of spaced apart wires of orthogonal intersection, running parallel to the length and width of the rectilinear shape of the frame within the projections in order to increase its rigidity, the edge regions are internally reinforced by metal box section members joined at their four corners, and the ends of the wires are secured in the box section members. Preferably, the box section members are encapsulated in the same plastic material as the cast orthogonal series of intersecting bosses is formed. In a preferred arrangement, the alternate ridges are not reinforced with wires and could only extend a short distance between the upper face and the lower side of the frame, usually a medium distance, and are referred to as half-height projections. The wire lengths, which are folded to form spacers and are adapted to be placed between the upper and lower wires of the shoulder reinforcement structure, could be welded or otherwise bonded with the upper and lower wires, so that they extend between them and that maintains the desired separation of the two layers of wires during the plastic encapsulation / molding process. The separators are completely contained within the plastic material that forms the projections during the encapsulation / molding process. Therefore, the rectangular perimeter of the screen frame is a substantially rigid structure that will not be shaken when oscillated in use in a vibrator and is strong enough to resist bending or forming due to the wire tension of the fabric In addition, it can be extended in larger areas than GRP reinforced screens previously developed by the VSM series of vibrators from Rig Technologies. In use, the perimeter of the screen is sealed against the rectilinear seat inside the vibrator to prevent the infiltration of liquid around it. The reinforcement of the box section provides a sufficient strength to eliminate the separation that may occur between the frame and the seat due to the shaking and in this way, the derivation of the fluid and the damage problems of the seal will be solved. The rigid perimeter also acts as an additional support for the upper and lower wires of the internal wire mesh structure, and this reduces the relative deformation of the grid of the intersecting bosses to a range such that excessive splash will also be reduced. if not that it be eliminated. The cutting members or box section of the perimeter reinforcing frame could have a square or rectangular cross section. Preferably, the ends of the two layers of wires are secured on the upper and lower faces of the perimeter reinforcement of cross-square or rectangular cross-section. The invention is also located in a structure that reinforces the basin of plastic material on which the mesh or woven metal fabric will be tensioned and joined to form a screen sieve, comprising two separate layers of wires of interest. orthogonal ection running parallel to the length and width of the rectilinear form of the frame, and a subframe of recti line union of the metal box section pieces united in their four corners in which the ends of the wires. In this structure, the ends of the wires in one layer are secured in the upper face of the sub-frame members and the ends of the wires in the other layer are secured in the lower part of the sub-frame members. The invention is also located in a screen constructed from a frame as indicated, having at least one layer of woven wire fabric stretched over and secured to the upper surface of the frame, so that the tension in the frame is maintained. Wire cloth at the end of the manufacturing process. Normally, this screen is fixed in position in a vibration basket using a pneumatic seal or by wedges dragged in position between the projections protruding internally from the vibration basket and the upper face of the edge regions of the screen . The invention is also situated in a screen as mentioned, that when it is placed in a vibrator where the screen is held in position in the vibration basket, a pneumatic seal is used or wedges dragged in position between the projections protruding in Internal shape from the vibration basket and the upper face of the edge regions of the screen. Brief Description of the Figures In the following, the invention will be described by way of example with reference to the accompanying figures, in which: Figure 1 is an exploded perspective view of part of a known screen, Figure 2 is a fragmentary section of the upper end of one of the series of intersecting ridges in the known frame showing a reinforcing wire embedded in the molded GRP material, Figure 3 is a "perspective view of the welded wire reinforcing grid that is employed in the manufacturing of the known screen, Figure 4 is a cross section through one of the projections of Figure 1 showing the upper and lower wires, Figure 5 is a cross section through the outer perimeter of a frame constructed in accordance with the first aspect of the present invention, in which the box section is square, Figure 6 shows a securing technique of a large area screen on a vibrator, Figure 7 is a perspective view of the metal reinforcement structure including the invention in which the frame of refue The perimeter rim is of a rectangular box section, and the wires extend between the opposite sides of the frame, Figure 8 is a similar view of the complete screen after being encapsulated in a GRP material in which the proximal side corner is in cutting to reveal the reinforcing wires and the perimeter reinforcement of the box section, Figure 9 is a view similar to that of Figure 7 showing how the ends of the wires can be folded to include the box section, for welding therewith, Figure 10 is an enlarged view of a corner of the reinforcing structure of Figure 7, Figure 11 illustrates how the box section is supported within a mold tool by clamps-C, the Figure 12 shows how the open ends of the box section can be closed before molding, Figure 13 is a plan view of the reinforcing structure of Figure 9, 'Figure 14 is a cross-sectional view of line AA of Figure 13, showing the wire spacers in place, Figure 15 is a detail of a spacer, Figure 16 is a cross section of line BB of Figure 13, Figure 17 is a top plan view of part of a frame after the GRP molding although before the mesh or fabric has been applied thereto, Figure 18 is a partial cross section of Figure 17, Figure 19 is an enlarged view of the left hand end C of FIG. 18, FIG. 20 is an enlarged view of region D of FIG. 18, FIG. 21 is a partial cross section of line BB of FIG. 17, and FIG. Figure 22 is an enlarged view of the region F of Figure 21. Detailed Description of the Invention In Figure 1, a known support frame is shown comprising a welded grid of reinforcing wires, which is generally designated 10 ( and it is best observed in the Fig ura 3) which is embedded in a molded rectilinear structure defining an outer rectilinear flange 12 and a grid of orthogonal intersecting bosses, two of which are denoted in the Figure 1 by numbers 14, 16. Mesh or woven fabric layers such as 19, 21, 23 are located, tensioned and secured on the frame in a manner known per se. The upper edges of the projections 14, 16 have a triangular cross section as best seen in Figure 2, which shows the inner core of the plastic material 18 embedding one of the upper layers of the wires 20 and the hard smooth outer film of wear of plastic material 22. As best seen in Figure 1, two wires extend through each projection, an upper wire 20 and a parallel lower wire 24. The lower wires 24 are bent upward and welded with the wires higher at opposite ends of each wire laid, and (although not shown in Figure 3) also along each of the two longer sides of the reinforcing structure shown in 26. The double thickness of the wire extending to the end and the lateral flanges of the eventual frame have been found to provide a sufficient rigidity to the tabs for smaller area screens as used in the range of VSM vibrators from Rig Technology Ltd. Figure 4 is a cross section through the shoulder 16 of Figure 1. Figure 5 shows how the tab 12 is replaced by a reinforced cutting frame or box section according to the invention. The box section 32, it could be square as shown although other cross-sectional shapes such as rectangular or triangular are also possible. The box section reinforcement of the outer frame members creates a rigid non-flexible perimeter in the screen. A method of securing the screen in a vibration basket 46 is shown, schematically, in Figure 6. Here, the opposite side edges 48, 50 of the screen 52 are shown fastened between the lower support structure shown in FIG. dotted outline at 54, 56 and 58 forming a seat for the screen edges, and two blocks 64, 66 projecting laterally inward from the inner faces of the side walls 68, 70 of the vibration basket. Two wedges 60, 62 are entrained in position and wedged below the blocks 64, 66 to secure the screen in place. The rear wall of the basket is shown at 72 and a front wall of reduced height is shown at 74. The latter provides support for the longer edge of the screen, while the seat portion 56 provides support for the other longer edge of the screen. The wedges 60, 62 ensure that the side edges of the screen are sealed in the seat portions 54, 58, but unless the screen structure is rigid enough to prevent bending and swaying, the seal between the edges more lengths of the screen and the front and rear seating 74, 56 may be broken in use. This allows the fluid to seep through or filter around the longer edges of the screen. The joint between two of the edges in question is shown at 76 in Figure 6. A screen incorporating the reinforcing frame constructed in accordance with the present invention is shown in Figure 10. In this frame the upper and lower parallel layers of the orthogonal intersecting wires 75, 77 extend between the four sides of a rectangular metal box section joining member consisting of four parts 78, 80, 82, 84. The ends of the wires are welded with the upper and lower surfaces of the members of the loading section parts 78-84. After molding in a suitable tooling, the wires and the joining member are encapsulated in plastic material, preferably a glass-reinforced plastic material to form the finished frame as shown in Figure 11. As the frame is shown, this is partially cut to reveal the wires and the parts 78 and 80 of the box section joining member. Figures 9 and 10 illustrate how the ends of the wires can be bent so as to be superimposed on the top surface, and placed below the bottom surface of the box section. Two of these wires are denoted by the numbers 86, 88 in Figure 10, with the ends bent which are denoted by the numbers 90, 92.

The ends are welded with the box section as shown at 94. The corners of the box section member are splice joints that are welded as shown in 96 in Figure 10 and 98 in Figure 9. Because the cut or box section will be encapsulated by plastic material, it is necessary that it be flooded from the outside of the molding tool, and for this purpose, the C-clamps 100 are placed in points around the box section parts 78, 80, etc., as shown in Figures 11 and 12. In addition the opposite ends of the box section are sealed before molding by means of the plugs 102 as shown in Figure 12. The latter could be made of plastic material. or metal. Figure 13 is a top plan view of the reinforcing structure of Figure 9 on a reduced scale, and Figure 14 is a cross section of line AA of Figure 9 and shows two wire spacers 104, 106 located between the upper and lower wires 108, 110 and welded therewith. The spacers prevent the inserts 108, 110 from deforming and collapsing under the molding pressures, and could be provided along all the pairs of parallel wires at 108, 110 or simply along the selected pairs of wires. Figure 16 shows an arrangement in which the spacers are located only between the third, sixth, ninth, etc., pairs of wires. Figure 17 shows the upper part of the part of the eventual frame once the wires and parts of the box section have been encapsulated in GRP by molding. The flanges 112, 114, 116, 118 are formed along the upper surfaces of each of the reinforced box-section edges of the frame into which the fabric is embedded during the next stage of manufacture to convert the frame into a frame. screen. The flanges can also be observed in Figures 18 and 19 as well as the flanges 120 along the upper edges of the ridges, such as 122, in which the fabric will also be embedded at the same time as it is embedded in the flanges 112. , 114, et cetera. Figure 19 also shows how the material and the weight can be saved by providing non-reinforced half-height rims such as 124 between the full-height reinforced ledges 122, 126. Figure 20 shows how the foot of the intermediate ledges 120 can be formed with inclined profusions 130, 132 on opposite sides thereof. In addition, similar profusions may be provided on the inner face of each of the ends of the frame, one of which is shown at 134 in Figure 19 with its protrusion denoted by 136. FIG. 21 is another cross section through the molded and finished frame of Figure 17 although at a right angle to that of Figure "18 and showing how all the molded bosses 138, 140, etc., (which are orthogonal to projections 122) .- are protrusions of full height and fully reinforced Figure 22 simply shows the end region on the left, denoted by the letter F, in greater detail The encapsulation material surrounding the box section parts can be seen at 142 and 144 in the Figures 19 and 22. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (14)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A frame on which a woven fabric will be stretched and secured to form a screening screen that can be used to separate the solids from the drilling mud. recovered from the bottom of the perforation when drilling for oil or gas, characterized in that it comprises a rectilinear molded plastic frame having edge regions in which it is secured in place in a vibrator and defines a plurality of rectilinear windows formed by an orthogonal series of intersecting projections also of a molded plastic material, wherein at least some of the projections are internally reinforced by a structure comprising two separate layers of separated wires of orthogonal intersection moving in parallel to the length and width of the rectilinear shape of the frame within the projections to increase its stiffness, wherein: 1) the edge regions of the frame are internally reinforced by members of metal box section joined at their four corners and which define a perimeter reinforcement, and 2) the ends of the wires are secured in the members of box section. The frame according to claim 1, characterized in that the box section members are encapsulated in the same plastic material from which the orthogonal series of intersecting bosses are molded. 3. The frame according to claim 1, characterized in that the alternating projections are not reinforced with wires. 4. The frame in accordance with the claim 3, characterized in that the non-reinforced projections extend only partly between the upper and lower faces of the frame. The frame according to claim 1, characterized in that the lengths of the bent wire form the spacers and are adapted to be placed between the upper and lower wires of the boss reinforcement structure, are joined with the upper and lower wires in a manner that extend between them and maintain the desired separation of the two layers of wires during the plastic encapsulation / molding process. The frame according to claim 5, characterized in that the spacers are welded with the wires. The frame according to claim 5, characterized in that the spacers are completely contained within the plastic material forming the projections. The frame according to claim 1, characterized in that the perimeter reinforcement box section members have a square cross section. The frame according to claim 1, characterized in that the box section members of the perimeter reinforcement have a rectangular cross section. 10. The frame in accordance with the claim 1, characterized in that the ends of the two layers of wires are secured on the upper and lower faces of the perimeter reinforcement. A structure for the reinforcement of a plastic frame on which a woven fabric will be tensioned and joined to form a screening screen, characterized in that it comprises two separate layers of wires separated from orthogonal intersection running in parallel with the length and the width of the rectilinear form of the frame, and a sub-frame of rectilinear connection of the metal box section members joined at their four corners, in which the ends of the wires are secured. The structure according to claim 11, characterized in that the ends of the wires in one layer are secured in the upper face of the sub-frame members and the ends of the wires in the other layer are secured in the lower part of the sub-frame members. 13. The screen constructed from a frame in accordance with -the claim 1, characterized in that at least one layer of woven wire is stretched and secured on the upper surface of the frame, so that tension is maintained on the wire cloth at the end of the manufacturing process. The screen according to claim 13, characterized in that it is placed on a vibrator where the screen is held in position in a vibration basket using a pneumatic seal or by means of which in position between the supports protruding internally from of the vibration basket and the upper face of the edge regions of the screen. SUMMARY OF THE INVENTION A frame on which the woven mesh or fabric will be stretched and secured to form a screening screen and which can be used to separate -or screen the solids from the drilling mud recovered from the bottom of the borehole when drilling in look for oil or gas. The frame comprises a rectilinear molded plastic frame having edge regions in which the frame is secured in place in a vibrator. Within the frame there is a plurality of rectilinear windows formed by an orthogonal series of intersecting projections also of molded plastic material. Some of the projections are internally reinforced by a structure comprising two separate layers of spaced apart wires of orthogonal intersection, running parallel to the length and width of the rectilinear form of the frame within the ridges in order to increase their rigidity . The edge regions of the frame are internally reinforced by metal box section members joined at their four corners and define a perimeter reinforcement, and the ends of the wires are secured in the box section members. The box section members are encapsulated in the same plastic material from which the cast orthogonal series of the intersecting bosses are molded. The alternate ridges are not reinforced with wires and could only be partially extended between the upper and lower face of the frame The wire lengths, which are folded to form spacers and are adapted to be placed between the upper and lower wires of the reinforcing structure of protrusion, they could be welded or otherwise bonded with the upper and lower wires, so as to extend between them and maintain the desired separation of the two layers of wires during the plastic encapsulation / molding process.