GB2115304A - Launder channel member for a sewage treatment tank - Google Patents

Abstract

A launder channel member (7) is provided for a sewage treatment tank, which member has a generally right angle U-shaped cross-section provided with at least one transverse reinforcing wall internally connecting the base (7a) and limbs (7b, 7c) of the section. The member is bolted to the wall 3 of a sewage treatment tank with the base (7a) uppermost, and a weir plate (4) is attached to the outer surface of the downwardly depending inner limb (7b) so that the launder channel is defined between the weir plate (4), the member base (7a) and the tank wall (3). Leakage through the holes for bolts 9, which might occur in conventional launders wherein the channel member is arranged the other way up, is thus eliminated. A scum board may be mounted on the launder at a distance inwards of the tank from weir (4) (Fig. 6). The channel member may be of galvanised steel or polymer, possibly glass-reinforced. <IMAGE>

Description

SPECIFICATION Launder channel member for a sewage treatment tank This invention relates to a launder channel member for a sewage treatment tank, which launder channel member is suitable for use in conjunction with a plurality of like members to form a peripheral launder channel locatable around the inner or outer vertical wall of a sewage treatment tank adjacent the top thereof.

Conventionally sewage treatment tanks are cast in concrete on site or made from pre-fabricated metal sections bolted together on site. In the past launder channels for concrete sewage treatment tanks have been cast in concrete integral with the tank, and launder channels for metal sewage treatment tanks have been made from pre-fabricated galvanised metal launder channel members bolted to the tank sides. As a result of weight andlor corrosion problems arising with launder channels it has recently become the practice to use pre-fabricated launder channel members made from glass reinforced plastics (GRP).

For concrete sewage treatment tanks these known GRP launder channel members generally are substantially right angle U-shaped in cross-section of any desired curvature compatible with that of the tank wall and bolted through their bases to the top of the horizontal limb of right angle metal bracket members whose vertical limbs are in turn bolted to the tank wall. It is not feasible to secure the GRP launder channel members directly to the concrete tank wall due to wide dimensional variations in the tank wall.

For metal sewage treatment tanks these known GRP launder channel members generally are right angle Z-shaped in cross-section bolted to the tank wall via a downwardly directed limb so that the base of the section extends horizontally with the launder channel being defined between the tank wall, the section base and the upwardly directed limb of the section.

However the GRP launder channel member is constructed it is usually necessary for it to carry vertically extending adjustable height weir plates to find and control the true water level and flow in the tank after installation of the channel. The amount of vertical movement necessary for each weir plate usually is between 30 to 100 millimeters and is provided by slots in the weir plate through which the plates are bolted to the or upwardly directed limb of the GRP launder channel member.

This bolting of the weir plates to the upwardly directed limb of the GRP launder channel member produces two major disadvantages. The first of these disadvantages is that it is very difficult to provide an adequate sealing between the weir plate and the channel member limb which can lead to undesirable leakage between the tank and launder channel through the weir plate mounting holes with attendant contamination problems. Indeed in some installations total sealing between the weir plate and launder channel is required. The second disadvantage is that the weight of the weir plate and of the water acting thereon exerts a considerable force on the upwardly directed limb of the GRP launder channel member leading to atendancyforthe member to fail by breakage at the root of the limb with the base of the member section.

There is thus a need for a generally improved launder channel member which minimizes the foregoing disadvantages.

Accordingly the present invention provides a launder channel member for a sewage treatment tank, which member has a generally right angle U-shaped cross-section provided with at least one transverse reinforcing wall internally connecting the base and limbs of the section, the arrangement being such that the member may be secured to a sewage treatment tank with the base of the member uppermost and the weir plate attached to the outer surface of the downwardly depending inner limb of the member at a location below the base of the member so that the launder channel is defined between the weir plate, the member base and the tank wall.In this way the vertically extending limb of conventional launder channel members, to which the conventional weir plate is attached above the member base, is done away with and the weir plate extends down to and below the base of the channel and is attached to the channel member below the base of the channel. This eliminates any sealing problem at the attachment points.

The launder channel member may be linear or curved in plan and can be made from metal, a polymer based material or GRP.

Conveniently the weir plates are secured to the downwardly depending inner limb of the launder channel member by means of co-operating bolts and slots provided in the member limb and weir plate.

Conveniently the launder channel member is secured to the tank wall, or to spaced which are in turn secured to the tank wall, by means of cooperating bolts and holes provided in the downwardly depending outer limb of the launder channel member.

Advantageously means are provided for sealing between the weir plate and the downwardly depending inner limb of the launder channel member and for sealing between the downwardly depending outer limb of the launder channel member and the tank wall spacer.

Advantageously the launder channel member has a plurality of transverse reinforcing walls internally connecting the base and limbs of the section at spaced intervals there along. Preferably two such transverse reinforcing walls form the end walls of the launder channel member and are provided with means whereby two such adjacent end transverse reinforcing walls may be attached together to secure two members in adjacent end to end abutting relationship.

According to another aspect the invention also contemplates the combination of a launder channel member as aforesaid and a weir plate attached to the outer surface of the downwardly depending inner limb of the member.

According to yet another aspect of the invention there is provided a sewage treatment tank provided with a launder channel member of the invention For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:: Figure 1 is a cross-sectional view through a conventional launder channel member attached to a concrete tank, Figure 2 is a cross-sectional view through an alternative form of conventional launder channel member secured to a tank wall, Figure 3 is a perspective view from above of a launder channel member according to a first embodiment of the invention, Figure 4 is a cross-sectional view of the member of figure 3 shows attached to a sewage treatment tank wall and carrying a weir plate, taken on the line Ill-Ill of figure 3, Figure 5 is a perspective view from above of a second embodiment of a launder channel member according to the present invention, adapted to mount a scum board, and Figure 6 is a cross-sectional view through the launder channel member of figure 5 shown attached to a tank wall and carrying a weir plate and scum board, taken on the line V-V of figure 5.

Figure 1 of the accompanying drawings shows a conventional launder channel member 1 of substantially right angle U-shaped cross-section bolted through its base to the top of a horizontal limb of a right angle metal bracket member 2 which is in turn bolted by its vertical limb to a tank wall 3 made of concrete. A weir plate 4 is bolted to the inside of the upwardly extending inner limb of the member 1 in any convenient manner and preferably by means of bolts engaging in slotted apertures in the weir plate 4 to permit vertical adjustment of the weir plate to find and control the true water level in the sewage treatment tank.This form of construction suffers from the two disadvantages hereinbefore described in that it is difficult to provide an effective seal between the launder channel, defined by the launder channel member, and the inner area of the tank so as to avoid leakage through the weir plate fixing holes in the upwardly extending inner limb of the channel member 1. Of course if the launder channel member 1 is made of glass reinforced plastics (GRP) it also suffers from the disadvantage of being broken at the root of the upwardly extending limb and the base thereof due to pressure exerted on the limb by water on the weir plate 4 and the weight of the weir plate itself. Additionally shown in figure 1 is a conventional scum board 5 bolted to an extension of the bracket member 2 at a position spaced radially inwardly of the launder member 1 with respect to the wall 3 of the sewage treatment tank.

As shown in figure 2 of the accompanying draw ings conventional launder channel member 6 for use with a metal sewage treatment tank has a generally right angle Z-shaped cross-section bolted to the tank wall 3 via a downwardly directed limb so that the base of the section extends horizontally with the launder channel being defined between the tank wall 3, the section base and the upwardly directed limb. A conventional weir plate 4 is bolted to the inner surface of the upwardly extending limb of the member 6 as shown. Once again this form of conventional construction suffers from the two disadvantages described in respect of the conventional construction of figure 1.

On the contrary the launder channel member of the invention as shown in the embodiment of figures 3 and 4 and the further embodiment of figures 5 and 6 does not suffer from these disadvantages. As can be seen from figures 3 and 4 a launder channel member 7 according to a first embodiment of the invention has a generally right angle U-shaped cross-section provided with at least one transverse reinforcing wall 8 internally connecting the base 7a and the two limbs 7b and 7c of the member 7. As shown in figures 3 and 4 there are a plurality of transverse reinforcing walls 8 provided at spaced locations along the length of the member for reinforcing purposes.The end-most of these walls provide ends for the member whereby it may be attached to the corresponding adjacent end wall of adjoining members, preferably by bolts, to secure the members together in aligned end to end relationship around the inner surface of the tank wall 3.

Conveniently the members 8 are secured to the inner surface of the tank wall 3 by means of the outermost downwardly depending limb 7c. This may be by means of bolts through the limbs 7c into the wall 3 or by means of bolts through the downwardly depending limbs 7c into spacers (not shown) which in turn are secured to the wall 3 of the tank.

Conveniently shown in figure 4 a seal is located between the downwardly depending limb 7c and the tank wall 3. As also can be seen in figure 4 a weir plate 4 is secured to the outer surface of the downwardly depending inner limb 7b of the member 7 at a location below the base 7a so that the launder channel is defined between the weir plate 4, the base 7a and the tank wall 3. In this way the weir plate 4 takes the place of the upwardly extending limb of the conventional launder channel members 1 and 6, shown in figures 1 and 2 and is attached to the member 7 at a position below the base 7 a thereof by means of bolts 9 and interposed sealing means 10.

There is thus no bolt hole opening directly through the weir plate 4 into the launder channel itself and thus considerably reduced chance of any leakage occurring in to or out of the launder channel via the weir plate 4 bolt holes. Conveniently these bolt holes are in the form of slots extending in the vertical direction of the tank wall 3 in orderto permit vertical adjustment of the height of the weir plate 4.

As shown in figures 3 and 4the launder channel member of the invention conveniently is curved in plan to conform to the curvature of the tank 3.

Additionally in the embodiments illustrated the launder channel member of the invention is made of glass reinforced plastics (GRP) but of course it could alternatively be made of any other suitable material, such as a polymer based material or galvanised mild steel.

Additionally in the embodiment of figures 3 and 4 the construction illustrated in which the base 7a of the launder channel member 7 is upwardly directly and the limbs 7b and 7c are downwardly directed and reinforced by the transverse reinforcing walls 8 with the bolts 9 engaging holes in the downwardly directed limbs 7b which are reinforced by the wall 8 obviates the other disadvantage hereinbefore discussed in respect of the conventional constructions of figures 1 and 2. Thus the construction of the embodiment of figures 3 and 4 considerably reduces thetendancyfortheweir plate to break the member 7 at the route between the limb 7b and the base 7a.

To a considerable extent this breakage tendancy is minimized by the presence of the transverse reinforcing walls 8 and the small depth of the limb 7b in comparison with the upwardly extending limb of the conventional construction of figures 1 and 2. This is of considerable importance when the channel member is constructed of GRP as glass reinforced plastics has relatively poor stiffness and resistance to compression.

In the second embodiment of the invention illustrated in figures 5 and 6 the launder channel member is basically similar to that of the first embodiment with the exception that at least a part 7b of the downwardly depending inner limb 7b of the member 7 is further extended downwardly in order to provide an extended surface to which a scum board 11 may be attached by means of a bracket 12. Conveniently, as shown in figure 6, the scum board 11 is bolted to the bracket 12 to extend substantially vertically parallel to the weir plate 4 at a spacing therefrom corresponding to the length of the bracket 12.The bracket 12 itself is secured to the downwardly depending extended limb part 7d of the launder channel member 7 by bolts such as the bolt 9 which secures the weir plate 4 to the limb 7b and a further bolt 13 which secured the bracket 12 to the extended limb part 7d with the inter-position of a spacer 14 conveniently made of glass reinforced plastics. As shown in figure 5 the launder channel member 7 is provided with a pair of extended transverse reinforcing walls 8 which reinforce the extended limb part 7d over its full depth. These extend transverse reinforcing walls 8 are necessary to counteract the increased forces produced on the inner limb 7b of the launder channel member 7 by the brackets 12 and attached scum board 11 which extends above the top edge of the weir plate 4. This scum board is necessary in some sewage tank installations to provide primary scum removal.Of course the location of the bolts 9 and 13 below the level of the base 7a of the launder channel member 7 has the further advantage of avoiding leakage through the bolt holes into the launder channel.

Apart from having the two main advantages of increased strength and lack of leakage problems, the launder channel members of the present invention also offer the further advantages of ease and speed of assembly on site due to their simplified construc tion and attachment means and can be cheaper to produce than conventional launder channel members.

CLAIMS (Filed on 812183) 1. A launder channel member for a sewage treatment tank, which member has a generally right angle U-shaped cross-section provided with at least one transverse reinforcing wall internally connecting the base and limbs of the section, the arrangement being such that the member may be secured to a sewage treatment tank with the base of the member uppermost and a weir plate attached to the outer surface of the downwardly depending inner limb of the member at a location below the base of the member so that the launder channel is defined between the wier plate, the member base and the tank wall.

2. A launder channel member according to claim 1,which is linear or curved in plan and made from metal, a polymer based material or GRP.

3. A launder channel member according to claim 1 or claim 2, wherein the weir plate is securable to the downwardly depending inner limb of the launder channel member by means of co-operating bolts and slots provided in the member limb and weir plate.

4. A launder channel member according to any one of claims 1 to 3, securable to the tank wall, orto spacers which are in turn secured to the tank wall, by means of co-operating bolts and holes provided in the downwardly depending outer limb of the launder channel member.

5. A launder channel member according to claim 4, including means for sealing between the weir plate and the downwardly depending inner limb of the launder channel member and for sealing between the downwardly depending outer limb of the launder channel member and the tank wall or spacer.

6. A launder channel member according to any one of claims 1 to 5, having a plurality of transverse reinforcing wall internally connecting the base and limbs of the section at spaced intervals therealong.

7. A launder channel member according to claim 6, wherein two such transverse reinforcing walls form the end walls of the launder channel member and are provided with means whereby two such adjacent end transverse reinforcing walls may be attached together to secure two members in adjacent end to end abutting relationship.

8. A launder channel member according to any one of claims 1 to 7, in combination with a weir plate attached to the outer surface of the downwardly depending inner limb of the member.

9. A sewage treatment tank provided with a launder channel member according to any one of

Claims (1)

1. claims 1 to 8.

   10. A launder channel member, substantially as hereinbefore described with reference to Figures 3 and 4 or Figures 5 and 6 of the accompanying drawings.