GB2360001A

GB2360001A - Filter screen for storm water system

Info

Publication number: GB2360001A
Application number: GB0005331A
Authority: GB
Inventors: Philip John Badger; Stephen David Rivers
Original assignee: HYDROK UK Ltd
Current assignee: HYDROK UK Ltd
Priority date: 2000-03-07
Filing date: 2000-03-07
Publication date: 2001-09-12
Anticipated expiration: 2020-03-07
Also published as: GB2360001B; GB0005331D0

Abstract

A filter screen 55 for a storm water overflow system, comprises an array of elements having a triangular cross-section 2, with the bases of the triangles facing upstream. The filter screen may have a second array of elements of pear shaped cross-section 21. The filter screen is preferably presented to the water at an angle in the range 30-60{. Preferably a rake bar 56 and means 57 for moving said bar are provided for removing particulate matter from the surface of the filter screen. The filter screen may have a cylindrical profile (55, Fig 5), with the rake bar pivotably mounted co-axial with the screen. The filter screen may be corrugated (31, Fig 3). The elements may be wire. The storm water overflow system may comprise a baffle plate (34, Fig 4) so that in the event of a surge of water, the water is directed through the filter screen (31, Fig 3). The storm water overflow system may also comprise a vertical filter screen (33, Fig 3) so that if the water flow rate is greater than that which can be handled by the filter screen, water flows over the top of the vertical filter screen, across the filter screen, and over the upstream end (45, Fig 4), which acts as a weir to a storm drain (not shown).

Description

1 STORM WATER SCREEN 2360001 The present invention relates to screen

devices for removing solid matter from water flowing in conduits, and more specifically, to a device for removing solid matter from storm water drainage systems.

Sewerage water courses are designed to accept at least the normally anticipated maximum flow through them. Storm water entering the sewerage system can overload the pipes and/or channels constituting the io sewerage system and it is necessary to provide overflow facilities. Legislation now requires that such overflow systems include screens adapted to remove from storm water flows particulate matter having a transverse dimension greater than 6 mm.

It is an object of the present invention to provide an improved particulate matter filter screen particularly for use in storm water overflow drainage systems.

According to the present invention, there is provided a filter screen for 2o removing particulate matter from a stream of flowing water, comprising a plurality of regularly spaced elements having a pear shape crosssection orientated with the bases of the triangular cross-sectioned elements presented to water flowing through the screen.

0 The surface area of the screen may be increased by forming it into corrugations, preferably of triangular form.

2 There may be provided also a cleaner adapted to be moved over the upstream face of the screen thereby to dislodge particulate matter lodged in the interstices between the elements forming the screen.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: - Figure 1 is a cross-section of a portion of a water particulate matter filter screen embodying the invention.

Figure 2 is a perspective view of a portion of a second water particulate filter screen embodying the invention.

Figure 3 is perspective view of a storm water overflow filter screen 15 embodying the invention, and Figure 4 is a schematic cross-section of the storm water overflow screen of Figure 3, and Figure 5 is a perspective view of another embodiment of the invention.

Referring to Figure 1 of the drawings, a water particulate filter screen 1 consists of an array of parallel wires 2 of triangular cross-section. The wires 2 are mounted in a frame 3 with one set of faces 4 co-planar. The separation 'A between the wires 2 is equal to the size of the particulate material the filter screen 1 is intended to remove from water flow. In use, the frame 3 is so positioned with respect to the direction of flow of water from which particulate matter is to be removed that the co-planar surfaces 4 of the wires 2 of the screen 1 are presented to the flowing water. By this 3 means, the tendency of particulate matter to become wedged between the wires 2 of the filter screen 1 is reduced. As shown, the cross-sections of the wires 2 are equilateral triangles, but this is not a necessary condition for the invention to perform its function. If, in use, the filter screen 1 is positioned at an angle to the direction of water flow, then the projected gaps between the wires 2 of the filter screen 1 decreases, as shown at U in the figure, so increasing the effectiveness of the filter screen 1. On the other hand, the flow resistance of the filter screen/also increases; a practical compromise for a filter screen/with wires 2 of equilateral triangular cross- io section is an angle of incidence of sixty degrees.

Figure 2 is a perspective view of a second embodiment of the invention in which a second array of pear shape cross-section wires 21 is superimposed on the fixst array with the wires 2 and 21 orthogonal. The second array of wires 21 acts to trap elongated particles which pass through the array of wires 2. As shown, the area presented to water flowing through the space bounded by the intersection of a pair of adjacent wires 2 and 21 first increases and then decreases, causing corresponding changes in the velocity of the flowing water. These changes in the velocity of the flowing water agitate the particuJate matter and reduce the tendency for it to be sucked through the filter screen 1.

Referring to Figure 3, a particulate filter screen assembly 30 for a storm water overflow system consists of a number of individual filter screens 1 of the types described with reference to figure 1 or figure 2, but preferably the latter, which are arranged to form a series of parallel ridges 31. The filter screens 1 are attached to a frame 32 and to a vertical filter screen 33, also constructed as described with reference to Figures 1 & 2. The filter screen 4 33 forms one side of a rectangular conduit 34. Positioned under the filter screens 1 is a flow-directing baffle 35.

Figure 4 is a schematic cross-section of a storm water overflow system of which the filter screen assembly 30 described with reference to Figure 3 forms part. Referring to Figure 4, the particulate filter screen 30 is positioned in an enclosure 41 which has an inlet pipe 42 and an outlet 43. The downstream end 44 of the enclosure 41 is higher than the top of the vertical screen 33 which in turn is higher than the upstream end 45 of the io enclosure 41. In normal circumstances, water flows straight through the enclosure 41 via the pipes 42 and 43. In the event of a surge of water, the water is directed by the baffle plate 34 through the filter screen ridges 31, through the vertical filter screen 33 and thence out of the enclosure 41 via the pipe 43. Should a position be reached where the water flow rate is greater than that which can be accommodated by the filter screen assembly, the water flows under the baffle plate 34, over the top of the vertical filter screen 33, across the tops of the ridges 31 of the filter screen assembly 30 and over the upstream end 45 of the enclosure 41, which acts as a weir, to a storm drain, not shown in the figure. When the surge subsides, the water trapped by the upstream end 45 of the enclosure 41 will back flow through the filter screen assembly, which tends to clear it of trapped debris.

Figure 5 shows another embodiment of the invention. Referring to Figure 5, a storm water overflow system 51 includes a channel 52 of rectangular cross-section at the upstream end 53 of which there is a weir 54 which includes a particulate matter filter screen 55 constructed of an array of wires - of triangular cross-section as described with reference to Figures 1 and 2. The filter screen 55 has a cylindrical form with the bases of the triangular wires forming it facing upstream. A rake bar 56 is arranged to be moved over the upstream face of the filter screen 55 by a mechanism 57 so as to enable accumulated debris to be removed from the surface of the filter screen 55.

As before, the entire assembly can be made of any suitable, non-corrosive material, or materials.

Claims

1. A filter screen for removing particulate matter from a stream of flowing water, comprising a laminar array of regularly spaced elements having a triangular cross-section orientated with the bases of the said elements presented to water flowing through the filter screen.

2. A filter screen according to Claim 1 wherein there is included a second laminar array of regularly spaced elements having apear shape crosssection parallel to the first array. The elements of the second array being orthogonal to those of the first array and orientated inversely with respect to those of the first array.

3. A filter screen according to Claim 1 or Claim 2 wherein the filter screen Is presented to the water at an acute angle.

4. A filter screen according to Claim 3 wherein the said angle is in the range thirty to sixty degrees.

5. A filter screen according to Claim 4 wherein the said angle is forty five degrees.

6. A filter screen according to any preceding claim wherein there is provided means for removing particulate matter from the surface of the filter screen presented to the water.

8.

A filter screen according to Claim 6 wherein the means for removing particulate matter from the surface of the filter screen presented to the water comprises a rake bar and means for causing the rake bar to traverse the said surface of the filter screen.

A filter screen according to Claim 7 wherein the filter screen has a cylindrical profile and the rake bar is pivotally mounted co-axial with the filter screen.

9. A filter screen according to any of Claims 1 to 6 in which the laminar array or arrays of elements are formed into a series of corrugations thereby effectively to increase the surface area of the filter screen.

10. A filter screen according to any preceding claim incorporated into a storm water overflow system.

A filter screen for removing particulate matter from a stream of flowing water substantially as hereinbefore described and with reference to Figures 1 and 2, Figure 3, Figure 4 or Figure 5 of the accompanying drawings.