A sewer water brake for a water drainage system and a water drainage system.

Technical Field

The present invention relates to a sewer water brake for controlling a flow of water in a water drainage system for surface water or storm water, such as flow from a storm water retention basin; a storm water tank; a manhole or chamber in a sewer system or storm water drainage system; or the like, comprising a housing forming a vortex chamber, especialy a volute, having a curved side wall; a peripheral inlet; and a central outlet, said central outlet being central relative to a vortex formed in use around an axis in the vortex chamber, wherein the sewer water brake comprises a movable element movable relative to a main part of the sewer water brake to adjust a geometric parameter of the sewer water brake thereby adjusting a braking characteristic or discharge characteristic of the sewer water brake.

It should in general be noted that the above mentioned axis is defined by the vortex, which is formed by liquid, especially water such as sewer water or sewage water flowing through the vortex chamber, when a pressure head of the liquid entering the vortex chamber is sufficiently large. Thus the position and direction of the axis is subject to minor fluctuations during operation, as it will be known to the person skilled in the art.

Background Art

Sewer water brakes of the above art, also known as vortex brakes or vortex flow controllers, are commonly used in sewer or drainage systems to protect the system parts downstream from the brake against hydraulic overload caused by too large flows.

The sewer or drainage systems may e.g. be storm water drainage systems or combined waste water and storm water drainage systems.

In case of a downstream sewage water treatment plant, as may e.g. be found in a combined waste water and storm water drainage system, hydraulic overload may result in active sludge being washed out of the plant which would be detrimental to the function thereof. In case of a downstream drainage system, e.g. a storm water drainage system, hydraulic overload may result in flooding of an area being drained of storm water through the downstream drainage system.

A sewer water brake of the above art has a discharge characteristic defined as the relation between the flow through the brake and the pressure head upstream of the brake. Often for sewer water brakes known in the art, it is endeavoured to obtain a discharge characteristic for the brake whereby outlet flow from the brake equals influx up to a certain limit after which increased influx to and resulting impounding at the brake substantially does not give rise to increased outlet flow from the brake, i.e. water is held back upstream of the brake resulting in a rising pressure head.

Vortex brakes are commonly used hydraulic brakes for waste water and/or storm water drainage systems and have the advantage of generally not having movable parts, thus requiring only little maintenance. In relation to the braking effect obtainable by a vortex brake the cross sectional area of the flow path is relatively large thus minimizing a risk of clogging by debris in the water being drained through the brake.

However, the risk of clogging by solid elements or debris in the drainage liquid does exist and for this reason it is known to provide a possibility of bypassing e.g. the inlet by opening a closure in the wall of the vortex chamber by manually pulling a cord, as it is e.g. known from EP 0 312 271 A1.

The brake effect in a vortex brake primarily arises in two aspects. First, an eddy in the vortex chamber will create a back pressure in the inlet as a result of centrifugal force. Second, there will be a pressure loss in the inlet itself. In addition, the way in which liquid is led through the inlet into the vortex chamber influences the formation of the eddy or vortex in the vortex chamber and its intensity.

An example of a sewer water brake or vortex brake of the kind mentioned by way of introduction is e.g. disclosed in WO 2008/064683 A1 , where a vortex brake for a drainage system having a vortex chamber with a curved wall, a central outlet, and a peripheral inlet having a relatively great resistance is disclosed. A second inlet wall portion extending from a first inlet wall portion has a free edge remote from a first inlet wall portion, allowing liquid to flow over the free edge, causing a contraction of the inlet flow without reducing the cross sectional area of the inlet. At the inlet of this known brake a movable element in the form of a manually shiftable cover plate is provided for adjustment of the size of the inlet opening. Further this known brake is provided with an exchangeable cover member with a hole at the outlet thus providing for manually changing the size of the outlet opening. Thus, it is possible manually to adjust the discharge characteristic of the brake by adjusting or changing geometric parameters relative to the inlet and the outlet.

Other examples of such vortex brakes offering possibilities of changing or adjusting manually geometric parameters relative to the inlet can be found in US 4834142; US 4679595; US 5303782; and US 5052442.

These known possibilities of adjusting the discharge characteristic of a brake are used generally once to adjust a brake during installation to fit given conditions. US 5303782 also discloses an embodiment in which a displaceable plate defining the size of the inlet opening is adjusted automatically by a pressure inside the vortex chamber.

EP 0 312 271 A1 , mentioned above, discloses another example of a sewer water brake or vortex brake or vortex valve of the kind mentioned by way of introduction. The vortex valve disclosed in EP 0 312 271 A1 is, as mentioned above, provided with a closure in the wall of the vortex chamber, said closure being openable, e.g. by manually pulling a cord, to provide a by-pass in case the inlet of the vortex valve should be blocked. Thus, according to EP 0 312 271 A1 : “When a blockage occurs at the inlet of the vortex valve, and water builds up in the gully in which the vortex valve is situated, the closure is moved (either manually or automatically) to the open position, permiting the flooded gully to empty, the liquid in the gully by-passing the inlet.” Further: “Preferably, the closure is operable between the closed position and the open position by means remote from the vortex valve. Thus, for instance, a cord may be attached to the closure, the cord leading out of the gully in which the valve is situated, for remote opening of the closure.” A lack of provisions for remote operation of the closure, i.e. operation from above the gully, would entail a necessity of entering the flooded gully to open the closure. EP 0 312 271 A1 further suggests that “Alternatively, a waterproof electrical actuator may be provided, responsive to a signal generated remotely, to open the closure.”. Since the closure of EP 0 312 271 A1 is intended for being closed, i.e. during normal operation, or completely open, in case of blockage of the inlet and necessity of emptying the gully, a need for an electronic control unit to provide for adjusting the position of the closure, in case an electrical actuator is used, does not exist and is not suggested. All that would be needed is a switch to actuate the electrical actuator to move the closure from the closed position to the open position.

Due to the fact that sewer water brakes are often mounted in places not easily accessible, especially when mounted in so-called submerged conditions i.e. in a reservoir, basin, tank, chamber, manhole, well, etc. at an outlet therefrom whereby the brake is flooded when the water rises in said reservoir, basin, tank, chamber, manhole, well, etc., the brakes are generally not adjusted after installation except perhaps in connection with maintenance if it has turned out that the initial adjustment of a brake does not fit with the needs.

Due to heavy storms, flooding occasionally occurs in spite of the provision of retention basins with sewer water brakes at the outlet, etc. possibly because such basins are overloaded due to failing or too little emptying between storms.

Storms may occur locally, and it is envisaged that within an area the capacity of one retention basin may be exhausted while a neighbouring retention basin has residual capacity. Thereby flooding may occur due to the exhausted capacity of one retention basin though residual basin capacity is in fact available within a neighbouring area.

It is an object to provide a sewer water brake and a water drainage system that may be used for solving or reducing the above problem. Summary of Invention

With this background, the invention provides a sewer water brake of the art mentioned by way of introduction which is characterized by an electronic control unit and an actuator controlled by the electronic control unit for moving said movable element. Hereby is obtained that the sewer water brake is provided as an active vortex flow controller and that the braking characteristic or discharge characteristic of the sewer water brake may be conveniently and frequently adjusted to provide for faster or slower drainage of e.g. a storm water or rain water retention basin in comparison with the speed of drainage provided by the braking characteristic or discharge characteristic provided by a default position of the movable element.

In an embodiment the vortex chamber comprises an front wall opposite the central outlet said front wall having a thickness which is less than 25%, preferably less than 15%, of the distance across the vortex chamber from the front wall to the central outlet, thus, the sewer water brake is in an embodiment made from sheet material such as steel sheet material, especially stainless steel sheet material. Other materials allowing a thin walled construction with sufficient strength and durability relative to the intended environment is envisaged, such as a plastic material, especially a fibre reinforced plastic material; ferrocement; ect. Hereby is obtained that the sewer water brake has sufficient strength and a weight that provides for convenient manufacture and handling during transport and installation, etc.

In an embodiment the sewer water brake comprises a battery for energizing said control unit, and preferably also for energizing the actuator. Hereby is obtained that the sewer water brake does not need to be connected to an electric grid such as public infrastructure grid. By energizing the actuator electrically the movable element may be adjusted regardless a possible presense of an unstable source of energy, e.g. a hydraulic pressure for driving the actuator.

In an embodiment the sewer water brake comprises communication means for remote communication with said control unit. Hereby is obtained that one or more sewer water brakes at different locations may be controlled from a central unit.

In a further embodiment said communication means are wireless communication means. Hereby communication wires are avoided.

By providing the sewer water brake without a need for wiring from a public infrastructure grid, whether for power or for communication, it is obtained that the sewer water brake may be installed where needed, also in areas remote from such public grids.

In an embodiment the sewer water brake comprises at least one sensor communicating with the electronic control unit. Such sensor may comprise at least one of a position sensor and a fluid pressure sensor. Hereby is provided for surveilance of the function of the sewer water brake by surveil ling e.g. the position of the movable element, or a pressure upstream of; inside; or downstream of the sewer water brake.

In an embodiment the control unit is adapted to control the actuator to return the movable element to a default position in case of one of the following: an alarm signal, and a low power supply. Hereby a predictable function of the sewer water brake is provided for in case of abnormal conditions.

In an embodiment the control unit is adapted to issue an alarm signal or information signal in case of at least one of the following: a discrepance between a calculated position of the movable element and a position of the movable element registered by a position sensor, said discrepance exceeding a threshold value; a low power supply; manual adjustment of the movable element; etc. Such information signal may be sent to a central unit to provide for warning a service staff that attention is needed for the sewer water brake.

In an embodiment the movable element comprises a wall portion in the vortex chamber. In a further embodiment said wall portion is positioned opposite the outlet, and is movable towards and away from the outlet. Hereby is provided for adjusting the dimensions of the vortex chamber, such as a width of the vortex chamber, to adjust the braking characteristic or discharge characteristic of the sewer water brake. In an embodiment the movable element comprises an outlet element defining an outlet aperture of the central outlet. Hereby is provided for adjusting the discharge characteristic of the sewer water brake by adjusting the size of the outlet aperture.

In an embodiment the movable element comprises an inlet element defining an inlet aperture of the inlet. Hereby is provided for adjusting the discharge characteristic of the sewer water brake by adjusing the size and/or shape of the inlet and/or the inlet aperture.

In an embodiment the movable element comprises a valve member for opening and closing a third opening in the vortex chamber, said third opening preferably being positioned opposite the outlet. Hereby is provided for an adjustable bypassing of the inlet thus providing for a controlled rapid discharge through the sewer water brake.

The object is further obtained by a sewer water brake system comprising a sewer water brake according to the invention and a local energy harvester, preferably comprising at least one of solar cells; a wind turbine; and a water turbine. Hereby is further obtained that the sewer water brake does not need to be connected to an electric grid such as public infrastructure grid. This applies especially when the sewer water brake comprises a battery for energizing the control unit. In such case the local energy harvester may charge the battery to avoid, or at least reduce, a need for regular change of battery due to battery voltage running low.

Further presently preferred embodiments and advantages will appear from the following description and subsequent claims.

Brief Description of Drawings

In the following description embodiments of the invention will be described with reference to the schematic drawings, in which

Fig. 1 is a front view of an embodiment of a sewer water brake;

Fig. 2 is a side view of the sewer water brake of Fig. 1 ;

Fig. 3 is a perspective view of a sewer water brake similar to the sewer water brake of Fig. 1 ; Fig. 4 is a perspective view of a second embodiment of a sewer water brake;

Fig. 5 is a perspective view of a third embodiment of a sewer water brake;

Fig. 6 is a perspective view of a fourth embodiment of a sewer water brake;

Fig. 7 is a perspective view of a fifth embodiment of a sewer water brake;

Fig. 8 is a perspective view of a sixth embodiment of a sewer water brake;

Fig. 9 is a perspective view of a seventh embodiment of a sewer water brake, and

Fig. 10 is a block diagram illustrating the control and components of the water drainage system including the sewer water brake.

Description of Embodiments

Referring initially to Figs. 1 and 2, a sewer water brake 1 for controlling a flow of water in a water drainage system 23 (see Fig. 2) is shown. The water brake 1 is mounted, in this embodiment, on a side wall at an outlet 24 in the water drainage system 23, such as an outlet from a rain water retention basin 23a or the like. The sewer water brake 1 comprises a housing 2, which forms a vortex chamber 3. The vortex chamber 3 has a front wall 30, a back wall 25, a curved side wall 4, a peripheral inlet 5, and a central outlet 6. The curved side wall 4, the front wall 30, and the back wall 25 collectively surrounds the vortex chamber 3. The central outlet 6 is provided at an outlet opening in the back wall 25. The central outlet 6 is located centrally relative to a vortex (not shown) that is formed in use around an axis A in the vortex chamber 3. The sewer water brake 1 further comprises a movable element 7, which is movable relative to a main part 8 of the sewer water brake 1 to adjust a geometric parameter of the sewer water brake 1. In the embodiment shown in Figs. 1 and 2 the movable element 7 is constituted by an inlet element in the form of a slidable cover plate 28 defining an inlet aperture 20, especially a side of the inlet aperture, of the inlet 5, whereby adjustment of the position of the cover plate 28 results in an adjustment of the size of the inlet 5 which is one of several geometric parameters of the brake. By adjustment of the geometric parameter of the brake 1 , a braking characteristic or discharge characteristic of the sewer water brake is adjusted. The sewer water brake 1 further comprises an actuator 9 with a rod 10 controlled by a electronic control unit for moving the movable element 7, as will be explained later with reference to Fig. 10.

Figs. 1 and 2 show an embodiment of the sewer water brake, where the housing has a substantially cylindrical shape.

The peripheral inlet 5 of the water brake 1 comprises the inlet aperture 20, which is defined between a first wall portion 26 of the curved side wall 4 and a second wall portion 27 of the curved wall 4. The second wall portion 27 is provided by the cover plate 28. The cover plate 28 may be a plane cover plate 28, as shown in solid line, or it may be a curved cover plate 28', as shown in broken line. The inlet aperture 20 is further defined by two opposite, free edges 29 of the front wall and the back wall, respectively.

For production reasons, the water brake 1 is constructed with a plane front wall 30 and a plane back wall 25, shown in Fig. 2. The curved side wall 4 is designed with sectional constant radius of curvature. From the first wall portion 26, the curved side wall 4 extends straight (infinitely large radius of curvature) to a point 26a vertically below the outlet 6. From there, the curved side wall 4 extends through 180° with a radius of curvature r1 to a point 35 vertically above the outlet 6, where the radius of curvature is reduced to a second radius of curvature r2 as the centre of the radius of curvature is shifted vertically over a distance d. The wall 4 extends through 90° with the radius of curvature r2 after which the curved wall 4 has a small straight section 27’ for connection to cover plate 28, 28' that continues the curved wall 4. Between the front 30 and back wall 25 opposite the small straight section 27’ is mounted in this embodiment a bar 31 . The cover plate 28 is received and guided between the small straight section 27’ of the curved wall 4 and the bar 31 . The rod 10 of the actuator 9 is connected to the cover plate to cause the cover plate 28 to move up and down, as seen in Figs. 1 and 2, so that the size of the inlet aperture 20 is adjusted accordingly based on a signal from the electronic control unit (see Fig. 10). Screws 32 in the bar 31 may be used for adjusting a play between the bar 31 and the small straight section where the cover plate 28 is received.

Apart from the actuator 9 and the rod 10, the water brake 1 shown in Figs. 1 and 2 and described so far is similar to the water brake shown in WO 2008/064683 A1 and the water brake 1 may be provided with a coupling for attachment of the water brake 1 to the outlet 24 similar to the coupling disclosed in WO 2008/064683 A1 .

Further, like in WO 2008/064683 A1 the water brake 1 is provided with a vent pipe 34 at the top for venting the vortex chamber 3. The vent pipe 34 may in a similarly known way be provided with a handle (not shown) by means of which the water brake can be lifted for detachment or attachment, for instance for cleaning.

Further, like in WO 2008/064683 A1 , at its outlet 6, the water brake 1 is provided with a cover member 36 having a smaller hole than hole 38 in a coupling part, said cover member defining an outlet opening of the central outlet 6.

When in operation a vortex is formed in the vortex chamber 3 by water entering the vortex chamber 3 through the peripheral inlet 5, the water will follow the curved side wall 4 and the water will eventually follow a spiral path around the axis A to the central outlet 6. Accordingly, the axis A extends through the central outlet 6 and, in the embodiment shown in Figs. 1 and 2, substantially perpendicular to the front wall 30 and back wall 25.

The water brake 1 may be constructed from a plate or sheet material such a stainless steel plate material, as it is generally known in the art of sewer water brakes. Other materials suited for a shell-like construction, whereby i.a. the front wall 30 may be provided with a thickness which is less than 25%, preferably less than 15% and preferably even less, of a distance across the vortex chamber along the axis A from the front wall 30 to the central outlet 6, may be used. Such shell-like construction provides for a relatively low weight compared to the general size of the water brake thus facilitating handling during production, transport, installation, maintenance, etc.

Fig. 3 shows a schematic, perspective view of a water brake 1 similar to the water brake 1 shown in Figs. 1 and 2, wherein similar elements are given similar refence numerals. The rod 10 of the actuator 9 is attached to a bent section 28a of the cover plate for the actuator 9, through the rod 10 to shift the cover plate 28 back and forth in the direction of the rod 10 to adjust the size of the inlet aperture 20 of the inlet 5.

Figs. 4 to 9 show schematically different embodiments of the sewer water brake 1 , which mainly serve to illustrate different embodiments of the design relating to the movable element and thus the possibility of adjusting the discharge characteristic of the sewer water brake. Accordingly, elements similar to elements of Figs. 1 and 2 are given similar reference numerals.

Fig. 4 shows another embodiment of the water brake 1 , where the movable element 7 comprises a wall portion 16 in the vortex chamber 3. The wall portion 16 is positioned opposite the outlet 6 and extends across a direction of the axis A. The wall portion 16 thus defines an effective vortex chamber portion 3a, which is adjacent to the central outlet 6, and a passive chamber portion 3b. When the actuator 9 via the rod 10, that passes through the front wall 30, moves the wall portion 16, the volume of the effective vortex chamber portion 3a is adjusted, thus adjusting the discharge characteristic of the sewer water brake 1 , while the overall volume of the housing 2 is not affected. The wall portion 16 can be moved towards the central outlet 6 and back wall 25 and/or towards the front wall 30 along the axis A.

Fig. 5 illustrates another possibility of adjusting the discharge characteristic of the sewer water brake by adjusting the size of the (effective) vortex chamber. Accordingly, in the embodiment of Fig. 5, the volume of the vortex chamber 3 is adjusted telescopically in that the side wall 4 is divided into two or more co-axial pieces 42a, 42b, which can be moved upwards and/or downwards (when the sewer water brake is positioned as seen in Fig. 5) relative to each other. In a preferred embodiment, the water brake comprises two pieces 42a, 42b. The pieces 42a, 42b can have the same height or different heights from piece to piece. In the embodiment shown in Fig. 5, when the top piece 42a together with the front wall 30 is moved downwards towards the back wall 25, the volume of the vortex chamber 3 is reduced thus adjusting the discharge characteristic of the sewer water brake 1 since the smaller vortex chamber 3 will allow less water to pass through the water brake at a given, substantial pressure head upstream of the water brake 1 . The front wall 30 together with the upper piece 42a of the side wall constitutes the movable element 7 in this embodiment and the movable element 7 may be moved by means of an actuator not shown in a direction of the axis A. Correspondingly, the main part of the brake 8 is in this embodiment constituted by the lower piece 42b of the side wall 4 and the back wall 25 that like in the embodiment of Figs. 1 and 2 may be adapted for mounting at an outlet in a rain water retention basin or the like.

In Fig. 6, an embodiment is shown, in which the discharge characteristic of the sewer water brake 1 is adjusted by adjusting the size of the outlet aperture 18. Thus, the movable element 7 of the water brake 1 comprises an outlet element in the form of a motorized iris diaphragm 44, which is positioned at the outlet 6. The diaphragm 44 comprises blades 47. The diaphragm 44 is connected to and motorized by the actuator 10, which is also positioned on the back wall 25 of the water brake. The actuator 10 causes the blades 47 to move so that the diaphragm 44 is gradually enlarging or reducing the outlet aperture 18 in the vortex chamber 3. Alternatively, the actuator 10 can be integrally formed with the diaphragm 44 or being positioned at the periphery of the diaphragm 44.

In Fig. 7, another embodiment is schematically shown, in which the discharge characteristic of the sewer water brake 1 is adjusted by adjusting the size of the outlet aperture 18. Thus, the movable element 7 comprises a shiftable outlet element in the form of an orifice element 17 comprising a number of different apertures 43 for defining the outlet aperture 18 of the central outlet 6. The orifice element 17 is plate-shaped. The orifice element 17 comprises a number of apertures 43 of different sizes, in this embodiment circular apertures 43 with different diameters, which, as the orifice element 17 is moved upwards or downwards, cover the outlet aperture 18 of the outlet 6 to define the effective size of the outlet aperture. In this way, there is a stepwise change of the (effective) diameter of the outlet aperture 18 as the orifice element 17 is moved up or down (relative to the position of the sewer water brake 1 as seen in Fig. 7) by means of the actuator 9 through the rod 10. In this embodiment, the orifice element 17 is a plate comprising the apertures 43 which have their diameter increasing downwards, and adjustment by shifting the orifice element 17 to change the aperture 43 currently in front of and coaxial with the outlet aperture 18 provides for stepwise adjustment of the effective size of the outlet aperture and thereby of the discharge characteristic of the sewer water brake 1 . Alternatively, only one aperture may be included in the orifice element to provide for stepless adjustment of the size of the outlet aperture 18, though the effective outlet aperture thereby will not remain circular but assume the shape of an American football. In the latter embodiment the aperture 43 may be constituted or substituted by a semi-circular recess in the lowermost end of the orifice element 17. The thickness of the plate-shaped orifice element 17 is substantially equal or smaller than the thickness of the front or back wall.

In Fig. 8, another embodiment is schematically presented, where the movable element 7 comprises no aperture. Instead, the movable element 7 comprises a valve member 21 for opening and closing a third opening 22 into the vortex chamber inside housing 2. The third opening 22 is positioned in the front wall 30 opposite the outlet 6 (not shown) in the back wall 25, and preferably positioned for the axis A to extend through the third opening 22. The valve member 21 acts as an evacuator valve, where controlled discharge of upstream volume can be achieved when a vortex is present in the vortex chamber. An outlet tube 45 is connected to the central outlet for guiding water away and for attachment to an outlet pipe in a water drainage system like the outlet 24 shown in Fig. 2

Fig. 9 shows another embodiment similar to the embodiment of Fig. 8, where the water brake 1 comprises a fixed plate 46 mounted on the front wall 30 surrounding the third opening 22. The fixed plate 46 together with a base, preferably of a low-friction material, provides a vertical pocket-like slot for receiving the valve member 21 and guide it for vertical shifting or translation by means of the actuator (not shown) and the rod 10, thereby providing an opening or a track where the valve member 21 can be inserted into or slid into, so that the valve member 21 gradually covers or uncovers the third opening 22 as it is moved upwards or downwards to stepless open or close the third opening 22 in a controlled manner. Again, the valve member 21 acts as an evacuator valve, where a controlled discharge of a volume of water upstream of the sewer water brake 1 can be achieved when a vortex is present in the vortex chamber. The functionality of the valve member and third opening should not be confused with known, manual by-pass valves where a rapid discharge of the water is intended to take place in case of a blockage and while there is no vortex in the vortex chamber.

Fig. 10 shows a block diagram of the control of the water brake, according to which the components and sequence of the control are schematically illustrated. The water brake 1 , as already mentioned, comprises i.a. the housing 2 and the movable element 7 for adjusting the discharge characteristic of the water brake, and the actuator 9. Further the sewer water brake 1 comprises an electronic control unit 12 for controlling the actuator 9. In the embodiment shown the sewer water brake 1 also comprises a battery 14, i.e. an electric battery, for energizing the electronic control unit 12 and preferably also the actuator 9. Further, in the present embodiment communication means 13, which are preferably wireless communication means, for remote communication with the electronic control unit 12, are provided. In the embodiment shown the battery 14 is also used for energizing the communication means 13.

Although the battery 14 is herein mentioned as a unit it should be understood that the battery 14 may comprise more separate electric elements and different electric elements may energize different ones of the electronic control unit 12, the actuator 9, and the communication means 13.

By means of the communication means 13 data may be sent from a central unit, not shown, to the electronic control unit 12 which accordingly may be provided with or may calculate set values for the movable element 7 of the sewer water brake 1 in order to provide an intended (change of the) discharge characteristic of the sewer water brake 1 by adjusting the position of the movable element 7 and accordingly adjust the corresponding geometric parameter.

In the embodiment illustrated in Fig. 10 the sewer water brake 1 also comprises one or more sensors 15. The one or more sensors may comprise a position sensor sensing the position of the actuator 9 or the movable element 7, and the one or more sensor may comprise a fluid pressure sensor sensing a pressure upstream of, inside, or downstream of the housing 2 of the sewer water brake 1. Further sensors may also be included. The sensor(s) 15 may communicate sensed values to the control unit 12 for the control unit 12 to communicate the sensed values to the central unit through the communication means 13 and/or the control unit 12 may use the sensed values for calculating a set value for the actuator 9 or the movable element 7.

In order to save energy, the actuator 9 is preferably of a kind that retains its current position when not energized, e.g. the actuator may be a spindle motor. Further the control unit 12 may be adapted to hibernate and wake up according to a scheme for communicating with the central unit, obtaining values from any sensors 15, and transferring instructions to the actuator 9 to perform any adjustment necessary to the position of the movable element 7.

In an embodiment, the control unit 12 is adapted to control the actuator 9 to return the movable element 7 to a default position in case of a low power supply and/or in case of certain alarm signals. An alarm signal may be generated by the control unit 12 e.g. in case of a discrepancy between a calculated position or set value of the movable element 7 and a sensed position of the movable element 7 registered by a position sensor 15 such discrepancy exceeding a threshold value and/or in case of a low power supply and/or in case of a manual adjustment of the movable element. Such alarm signal may be communicated to the central unit by means of the communication means 13.

The communication means 13 may be any suitable communication means known in the art, preferably any suitable wireless communication means known in the art.

The sewer water brake may be included in a system further comprising a local energy harvester 50, such as solar cells, a wind turbine, and/or a water turbine, to provide for charging the battery 14 thereby diminishing the need for exchanging a flat battery 14 with a new or freshly charged battery

Providing the battery 14 for energizing at least the electronic control unit 12 entails that the sewer water brake 1 may be installed at a site remote from an electric power grid. The battery 14, or at least some of it in case the battery 14 comprises several elements, may be rechargeable and in such case the battery 14, or rechargeable elements thereof, may be charged by the local energy harvester 50 when such is provided. In the alternative the battery may be charged or substituted by new or freshly charged batteries by an operator visiting the site, where the sewer water brake 1 is installed, in accordance with the needs.

It should be noted that although the sewer water brake 1 in the above has been described as having a generally flat housing 2 comprising a flat front wall 30, a flat back wall 25 parallel thereto, and a generally cylindrical curved side wall 4, other constructions of the housing 2 are possible as the skilled person will appreciate and as are known in the art, including, but not limited to, a flat housing with a rounded rather than cylindrical side wall, and a generally conical housing with the peripheral inlet positioned at the base of the cone shape, e.g.in a base wall or in a conical side wall at the base, etc., and the central outlet positioned at the top of the cone shape.