GB2270009A

GB2270009A - Liquid discharge device

Info

Publication number: GB2270009A
Application number: GB9218214A
Authority: GB
Inventors: Roger Julian Cook; Garry William Fagan; Harry Matthew Pelaez
Original assignee: Hydro International Ltd
Current assignee: Hydro International Ltd
Priority date: 1992-08-27
Filing date: 1992-08-27
Publication date: 1994-03-02
Also published as: CA2143284A1; WO1994005867A1; GB9218214D0; EP0664846A1; AU4971193A

Abstract

Liquid is discharged from a level which is a fixed distance H below the surface 5a by a vortex valve 7 which is suspended from or integral with the lower part of a float 15. Valve 7 has a tangential inlet 9, an axial outlet 11 connected to flexible hose 17 and an axial air inlet 23. The vortex created within the valve ensures a restricted and constant discharge flow. <IMAGE>

Description

DISCHARGE DEVICE This invention relates to a discharge device for discharging liquid from a reservoir under a substantially constant pressure head. More particularly, the present invention relates to a discharge device comprising a vortex valve flow control supported in a body of liquid a fixed distance below the liquid surface.

There is a need for a simple, effective constant discharge device. Existing methods of providing constant discharge are less than satisfactory, being either old-fashioned, for instance relying on constant volume floating arm, or highly complex, for instance in the form of motorised valves controlled by a sophisticated electronic system, usually, but not always, utilising a computer. The former of these techniques requires frequent maintenance and is not considered totally reliable as operating heads are negligible and performance fluctuates as a result. In addition where the liquid being dealt with is liable to have floating impurities or scum present, then a scum box is required. The latter is the source of the biggest problems in waste water treatment. The highly sophisticated systems mentioned can be notoriously unreliable and faults are liable to have serious consequences.

A vortex valve is a device for controlling fluid flow by a hydraulic effect without requiring moving parts. Such devices have a vortex chamber provided with an outlet at one axial end and an inlet arranged to cause swirl in the chamber when a certain critical flow has been attained. In use, the inlet communicates with a body of water which exerts a pressure head on the liquid entering the vortex chamber. US Patent No.

4206783 discloses a vortex valve having a conical vortex chamber with a tangential inlet and an outlet disposed at the narrower end of the chamber. Also known are short vortex valves of which the crosssectional configuration of the vortex chamber is a logarithmic spiral extending the full length of its longitudinal axis to the outlet. At low flow rates, water entering through the inlet of a vortex valve passes through the vortex chamber to the outlet with substantially no pressure drop and the valve can be considered to be open. However, at high flow rates, water enters through the inlet with enough energy to create a vortex in the vortex chamber which results in a considerable pressure drop between the inlet and the outlet and may greatly restrict flow through the outlet, or even substantially cut it off altogether.

Thus the valve serves to limit the rate of flow through it automatically. Vortex valves can be used, for example, to control the flow of storm water in sewers, to ensure that equipment downstream of the valve is not overloaded during periods of heavy rainfall.

Thus, according to a first aspect of the present invention, there is provided liquid discharge apparatus comprising a body of liquid of variable depth and a discharge device having a liquid outlet, the said discharge device being supported in the body of liquid at a fixed distance below the surface of the liquid and the said liquid outlet discharging to a position located outside the said body of liquid.

The discharge device is preferably a vortex valve flow control supported in the body of liquid. The vortex valve may comprise a housing defining a vortex chamber, the housing having an inlet through which liquid may enter the vortex chamber in a manner to promote swirl within the vortex chamber and an outlet at one axial end of the vortex chamber. When the discharge device is a vortex valve, the said fixed distance at which it is located below the liquid surface should be sufficient that a vortex is created in the vortex chamber.

The vortex valve may be, for instance, one having a conical vortex chamber, or it may be one in which the cross-sectional configuration of the vortex chamber is a logarithmic spiral. The inlet is preferably tangential to the vortex chamber.

The discharge device may be supported in the body of liquid by a float to which the discharge device is rigidly connected by, for instance, a rigid member.

Alternatively, the vortex valve and the float can be formed integrally or secured directly to each other.

The discharge device may be arranged so that the axis of the outlet is vertical, and the device therefore discharges downwardly.

Moreover, when the discharge device is a vortex valve, there may be provided a further inlet to the vortex chamber, preferably at an axial position in the end wall opposite the end wall in which the discharge outlet is situated, which communicates with a source of gas, for example air, to admit the said gas into the vortex chamber and facilitate the establishment of the vortex in the vortex chamber. For instance, the further inlet may communicate through a communication means such as a pipe to a point in the atmosphere outside the body of liquid.The communication means may for instance be the rigid member connecting the vortex valve and the float, suitably modified to have a hollow bore which opens directly into the vortex chamber at one end and being provided with a continuation at the other end which passes through or around the float to a point above the liquid surface to permit air to be admitted to the vortex chamber.

Alternatively, the said further inlet may communicate by a flexible hose with the necessary source of gas, for example the atmosphere.

The outlet may be provided with a spigot to which a flexible conduit or hose may be connected to discharge liquid from the device to a location outside the body of liquid. Thus, for instance, the flexible hose may pass through an opening in a wall of the body of liquid.

When the discharge device is a vortex valve, it is preferably oriented so that the intake is horizontal.

A valve may be provided outside the chamber in the flow line from the discharge device to isolate the system for maintenance.

The apparatus of the invention may be used widely in the waste water treatment industry, particularly at sewage treatment works, for regulating flows to treatment processes. Equally it may be used in any type of process industry where a need exists to balance or regulate flows in any manner. It will be a superior performance, low cost installation, accurate to within known tolerances, largely obviating maintenance requirements, requiring no energy input or manual attendance other than to open or close the isolating valve, if present. There may additionally be applications for regulating discharges of trade waste to sewers and drains.

The reservoir containing the body of liquid in which the discharge device of the present invention is situated may be a separator of the type described in British Patent No. 2082941 which discloses a separator which is particularly suitable for separating, for example, sewage and other solid matter from water in storm water overflows. The separator is in the form of a cylindrical vessel having an inlet which is disposed tangentially so as to promote a circulating flow within the vessel. This circulating -flow comprises an outer, relatively fast, flow and an inner, relatively slow, flow. The shear zone between these two regions is stabilised by an annular dip plate which projects downwardly from the top of the vessel. A flow modifying member is provided in the vessel to enhance the removal of solid particles accumulating at the bottom of the vessel to a central outlet.Clean water is removed from the top of the vessel. In the vessel shown in our British Patent No. 2082941, a floatables trap is provided directly above the inlet and opposite the outlet in order to reduce the possibility of floatable solids being discharged through the clean water outlet. It is specifically stated that the trap should be disposed anywhere around the circumference of the vortex chamber.

It has been found that, under storm conditions, the floatables trap of the separator disclosed in our British Patent No. 2082941, whilst performing satisfactorily for the majority of the time, may permit floatable material to reach the outlet, by passing under the annular dip plate. It is believed that this may occur as the separator is filling during the onset of a storm or, in the alternative, in a lull during a storm when the level of the water in the separator may drop below the level of the dip plate. It is proposed to provide a discharge device in accordance with the present invention at an upper region of the vessel, outward of the annular dip plate.

Thus, according to another aspect of the present invention, there is provided a low energy separator for separating solid components out of a liquid mixture, comprising (a) a vessel having a cylindrical outer wall and a base at one end, (b) a body which is provided within the vessel and which defines with the base an annular opening spaced from the outer wall, (c) an inlet for introducing the liquid mixture into the vessel, (d) an outlet in the upper region of the vessel for removing from the vessel liquid from which solid components have been separated, (e) a primary annular dip plate in an upper region of the vessel and spaced from the outer wall of the vessel and (f) means for promoting a rotational movement of liquid and suspended solids within the vessel, said rotational movement being sufficient to cause or enhance an inward sweeping effect towards the annular opening on solids accumulated at the base of the vessel, whilst being of sufficiently low energy that separation of the solids components of the liquid in the vessel is brought about primarily by gravity; wherein the separator also includes a discharge device having a liquid outlet, the said discharge device being supported in the vessel a fixed distance below the surface of the liquid in the vessel and the said liquid outlet of the discharge device discharging to a position outside the vessel.

Preferably, situated below the annular aperture, and axially of the vessel is a generally circular baffle which overlaps, in the vertical direction, the floatables trap in order to prevent floatable material floating directly upwards out of the annular aperture to the outlet by-passing the trap The means for promoting a rotational movement of liquid and suspended solids within the vessel may be the inlet to the vessel by which the liquid mixture is introduced into the vessel. In such a case, the inlet is preferably tangential and the energy of the liquid mixture being introduced into the vessel is sufficient to initiate and sustain the rotational movement in the vessel. Alternatively, or in addition, a further inlet may be provided by which an energizing liquid is introduced into the vessel to promote swirl (see our British Patent No. 2158741).

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 only, to the accompanying drawings in which: Figure 1 illustrates a liquid delivery arrangement in accordance with the present invention; Figure 2 illustrates a perspective view of part of the apparatus shown in Figure 1; and Figure 3 illustrates an alternative arrangement of part of perspective view of part of a liquid delivery arrangement in accordance with the present invention.

Figure 4 is a diagrammatic, vertical section through a separator incorporating a discharge device in accordance with the present invention; Figure 5 is a plan view of the separator shown in Figure 1.

With reference to both Figures 1 and 2, there is shown a liquid delivery apparatus 1 having an outer wall 3 and a base 4 comprising a reservoir 2 containing a body of liquid 5 having a surface 5a and a discharge device 6. In the embodiment shown in the figures, the discharge device 6 is a vortex valve flow control having a cross-section which is a logarithmic spiral.

The vortex valve 6 comprises a housing 7 defining a vortex chamber 7. The housing 7 has an inlet opening 9 and an axial outlet 10 in end wall 20. The outlet 10 is provided with a spigot 11 which projects downwardly from the vortex valve 6.

The vortex valve 6 is supported a fixed distance below the surface 5a of the body of liquid 5 by means of a float 15 to which the vortex valve 6 is attached by a rigid connecting member 16. In the embodiment illustrated, the vortex valve is supported a distance "H" below the surface of the liquid. This distance can be variable by using a connecting member 16 whose length can be varied.

The outlet spigot 11 is connected to a flexible hose which passes through the wall 3 of the reservoir 2 near the base 4. There is provided an isolating valve 18 to isolate the apparatus 1 for maintenance.

A further axial inlet 21 is provided in the other end wall 22 to admit air into the vortex chamber 8.

This further inlet 21 communicates with a position outside the body of liquid via the connecting member 16 which has a hollow core 23 which extends through the float 15 and opens to the atmosphere.

In use, the level of liquid in the reservoir can alter; however, as the level alters, the distance H will always remain constant, by virtue of the float 15 and rigid connecting member 16. This means that a constant head of liquid is exerted on the inlet opening 9 of the vortex valve and this ensures a constant discharge rate from the outlet 10 of the vortex valve 6. Obviously, as the vortex valve 6 and associated float 15 move vertically in the reservoir, the flexible hose 17 which is connected to the vortex valve 6 will move also and therefore there should be enough slack in the hose 17 to ensure that the float 15 and vortex valve 6 can move freely.

Figure 3 shows an alternative embodiment in which the vortex valve 6 is joined directly to the float 15.

The float has a passageway 30 in it corresponding to the hollow core of the connecting member 16 shown in the embodiment illustrated in Figures 1 and 2.

The separator depicted in Figures 4 and 5 comprises a vessel 101 having a cylindrical outer wall 102 and a sloping, conical base 103. The other end 104 of the vessel 101, opposite the base 103, is open, although it is to be appreciated that the separator may be closed by a lid. Within the vessel 101 there is provided a flow modifying member 105 in the shape of a cone which defines with the base 103 an annular opening 106 which is spaced from the outer wall 102 of the vessel The lower peripheral edge of the flow modifying member 105 terminates approximately half way between the central axis of the separator and the outer wall 102 thereof. A tangential inlet 107 to the vessel 101, through the outer wall 102, is provided by which a liquid containing solid components may be introduced into the vessel 101.There is also provided an outlet 108 in the form of a spillway leading to duct 108a and an annular dip plate 109 which is concentric with the outer wall 102 and spaced from the outer wall 102 defining an annular slot 110. The dip plate has an annular lower edge 109a. The dip plate 109 is supported by horizontal beams. Communicating with the annular opening 106 in the base 103 of the vessel 101 is an outlet pipe 111 by which solids accumulated at the base 103 may be removed.

A circular baffle 117 is supported from the beams 150 in an upper region of the vessel 101. Supported slightly below the surface of the liquid in the vessel outward of the dip plate is a discharge device 200 in the form of a vortex valve as described in more detail above (see Figures 1 and 2). The vortex valve 200 is support slightly below the surface of the liquid in the vessel; as the level varies, flow containing floatable material passes through the inlet 209 to the outlet of the valve 200 and from there to a flexible pipe 217 and away from the vessel where it may be combined with the underflow from pipe 111.

The operation of the separator will now be described, with particular reference to Figures 4 and 5.

Under normal operating conditions, collected water, for instance rain water from road run-off, enters the vessel 101 through the inlet 107. Normally, the rate at which liquid enters the vessel will be relatively slow and the separator will act almost as a clarifying vessel in which material heavier than the water entering sinks to the base 103 of the vessel 101, whilst clean water will slowly spill into the outlet duct 108 and will be carried away. The liquid in the vessel 101 will be circulating only very slowly, if at all.

Under storm conditions, however, in which large amounts of sediment and other such solid matter is carried into the water run-off, liquid entering the vessel 106 through the tangential inlet 107 will be travelling at a much higher velocity because of the high pressure head from liquid backed-up in the drainage system. Under these conditions, the vessel 101 will quickly fill and the liquid mixture being tangentially introduced in the vessel via the inlet 107 will circulate in the direction shown by the arrows in the vessel (Figure 4 and Figure 5). As described in our British Patent Specification No. 2082941, this circulating flow within the vessel is sufficient to cause an inward sweeping effect toward the annular opening 106 in the base 103 on solids accumulating at the base 103 of the vessel.However, the energy of the circulating fluid is not so large that centrifugal forces have any substantial effect on the particles of solid matter rotating in the vessel 101. The accumulated matter at the base may be removed via the outlet pipe 111. The flow modifying member 105 assists in creating a secondary, generally toroidal flow in the vessel whilst the annular dip plate 109 stabilizes a shear zone between an outer, relatively fast, flow and an inner, relatively slow, flow of liquid in the vessel 101.

Under storm conditions, the upper level of liquid in the vessel 101 will be close to the top of the annular dip plate 109, probably around the level shown in Figure 1 by the line 130.

Under normal storm conditions, the separator will be full and it is unlikely that any floatable material will escape into the main central part 115 of the vessel, but will rise and be trapped, floating, at the top of the annular slot 110. However, it is possible that even when the vessel 101 is full some floatable material may escape into the central region 115.

Moreover, as the vessel is filling and the level of liquid is below the level of the bottom edge 109a of the dip plate, or if the level of the water drops below the lower edge 109a of the dip plate 109 during a lull in a storm, it is likely that some of the floatable material may enter the central region 115 of the vessel, inward of the dip plate. According to the invention, the discharge device in the form of a vortex valve 200 is free to rise and fall within a vertical plane in the zone 110 outside the dip plate 109 and inward of the outer wall 102. The vortex valve 200 intercepts flow immediately below the surface of liquid, particularly floating material, independent of the absolute level of liquid in the vessel 101 and discharges it through pipeline 217.

The separator may be a separator in accordance with our British Patent No. 2158741 in which there is provided a further inlet by which an energising fluid may be introduced into the vessel in a manner to cause or enhance rotational movement of the liquid in the vessel.

The vessel shown in Figure 4 has a base region which is in accordance with our British Patent Publication No. 2189413. However, the base region of the separator may be as shown in the drawings of our British Patent Publication No. 2082941.

Claims

CLAIMS:

1. Liquid discharge apparatus comprising a body of liquid of variable depth and a discharge device having a liquid outlet, the said discharge device being supported in the body of liquid at a fixed distance below the surface of the liquid and the said liquid outlet discharging to a position located outside the said body of liquid.

2. Liquid discharge apparatus according to claim 1, wherein the discharge device is a vortex valve flow control supported in the body of liquid.

3. Liquid discharge apparatus according to claim 1 or 2, wherein the vortex valve comprises a housing defining a vortex chamber, the housing having an inlet through which liquid may enter the vortex chamber in a manner to promote swirl within the vortex chamber and an outlet at one axial end of the vortex chamber.

4. Liquid discharge apparatus according to claim 2 or 3, wherein the said fixed distance at which the vortex valve is located below the liquid surface is sufficient that a vortex is created in the vortex chamber.

5. Liquid discharge apparatus according to any preceding claim, wherein the discharge device is supported in the body of liquid by a float.

6. Liquid discharge apparatus according to claim 5, wherein the discharge device is rigidly connected to the float by a rigid member.

7. Liquid discharge apparatus according to claim 5, wherein the vortex valve and the float are formed integrally or secured directly to each other.

8. Liquid discharge apparatus according to claim 2 or any one of claims 3 to 7 when appendant to claim 2, wherein there is provided a further inlet to the vortex chamber at an axial position in the end wall opposite the end wall in which the discharge outlet is situated, which communicates with a source of gas to admit the said gas into the vortex chamber and facilitate the establishment of the vortex in the vortex chamber.