EP2766527A1

EP2766527A1 - Inlet grid cleaner

Info

Publication number: EP2766527A1
Application number: EP12839499.6A
Authority: EP
Inventors: Odd Jørgen BERGLAND
Original assignee: Rui Grindrensk As
Current assignee: Rui As
Priority date: 2011-10-14
Filing date: 2012-10-15
Publication date: 2014-08-20
Anticipated expiration: 2032-10-15
Also published as: EP2766527A4; WO2013055232A1; NO335943B1; NO20111392A1; EP2766527B8; EP2766527B1

Abstract

The present invention relates to a suction nozzle for a thrash rack of a power plant. The suction nozzle comprises an outlet with a pipe stub connectable to a flexible outlet hose, and a wedge-shaped distribution chamber (3) comprising an upper section, a lower section, and two sides extending between the upper section and the lower section. The distribution chamber is connected at a first end to the pipe stub and at a second end to a pressure beak (2). The pressure beak has a first side forming an inlet and a second side connected to a second end of the wedge-shaped distribution chamber. A connector cone (4) connects to the outlet and the wedge-shaped distribution chamber (3). The invention also includes a system for cleaning an inlet grid of a power plant having a suction nozzle as indicated above.

Description

Inlet grid cleaner

The present invention relates to an inlet grid cleaner, in particular for hydropower plants.

In hydropower plants, an inlet grid/thrash rack or grating is provided in the water intake of the power plant to prevent foreign matter from entering into the power plant. The screened intake is typically positioned in a dam to serve as a safety means to make sure that people and animals etc. are not sucked into the penstock, and also that debris is not able to get into the power plant. Such debris typically includes leaves, cones, rush, branches, moss, garbage, common bulbous rush, as well as other vegetation elements. The debris clogs the grating, thereby reducing the water flow rate into the penstock and power plant. In extreme cases, debris may completely block the grating.

To solve this problem, there has been suggested, in GB 324,630, for example, a cleaning arrangement for curved screens for water channels of water turbines, for example, in which one or more suction nozzles are pivotally mounted for rotation about a centre of curvature of the screen. The mouths of the suction nozzles are located upstream of and adjacent to the screen. A negative pressure for the suction nozzles may be provided via the outflow of an outlet pipe, which negative pressure causes a water flow through the nozzles which may thus carry debris with it. The solution uses a plurality of juxtaposed pipes and bends resulting in a pressure loss and uneven suction capacity over the area to be cleaned. Moreover, the solution provides a suction unit which cannot be used with grids not having a curved shape and which is fixedly mounted below the water surface. Hence, it is more difficult to have the suction unit cleaned or maintained because the arrangement cannot be easily brought above the water surface. In addition, any increased pressure loss would have to be compensated for by increasing the flow area, resulting in a less compact structure.

US 2001/054591 A1 discloses a waste water screen using a solids pump for extracting solids captured from the contaminated fluid flow from the screening means of the system and for carrying them in a concentrated form through a closed conduit leading to a cleaning/draining means.

US 2006/037897 A1 discloses a rotatable sieve or screen for a water intake designed as a loop formed by a consecutive series of flexible and articulated filter panels.

FR 2375395 A1 discloses an arrangement and method for the continuous removal of deposits in a reservoir pond.

Accordingly, the present invention relates to a suction nozzle for an inlet grid of a hydropower plant configured for connecting to an outlet channel extending to a level below a water surface of a pond. Such a grid is commonly referred to as a thrash rack or intake grating, and is available in various configurations.

Rectangular and circular inlet grids are the most common. In some cases, circular inlet grids are rotatable.

The suction nozzle includes an outlet having a pipe stub for connecting to at least one flexible outlet hose. A wedge-shaped distribution chamber is formed by an upper section, a lower section, and two sides extending between the upper and lower sections. The sides of the distribution chamber may be double-curved to minimize the water flow resistance, increase the water flow velocity, and optimize the throughput of water and debris. In this manner, the flow conditions along a path to a circular pipe are sought optimized.

The distribution chamber connects to the pipe stub at a first end. The second end of the distribution chamber connects to a pressure beak. The pressure beak has an inlet at its other end, opposite to the distribution chamber.

The inlet may be given an "extruded drop-shape" to ensure favourable

hydrodynamic conditions, adequate strength properties, as well as a proper separation of foreign matter, so that foreign matter above a certain size is excluded from entering in order to prevent clogging. The shape is important also to prevent branches and the like from getting stuck at the inlet.

A connector cone is provided at the transition between the outlet and the wedge- shaped distribution chamber.

A purpose of the suction nozzle disclosed is to provide a substantially uniform suction and cleaning performance across the entire inlet area of the suction nozzle.

The inlet may be a continuous opening defined by the pressure beak edges, and typically forms a rectangular, continuous aperture opening.

By creating a single, continuous opening, the risk of the opening being clogged by the debris to be extracted is reduced.

The distribution chamber is rounded with a radius of curvature determined by the internal diameter of the flexible outlet hose, as seen in a plane extending through a centred cross-section. Seen from above, the distribution chamber is to form an arc making a smooth transition from the distribution chamber.

The other end of the wedge-shaped distribution chamber may be rounded in a circular arc having a radius of curvature r, with the radius of curvature r defining an angle having a vertex substantially coinciding with a vertex of an angle defined by the two sides of the distribution chamber. The distribution chamber distributes the velocity profile of the water flowing from the pressure beak into the connector cone. In the distribution chamber, the pressure is higher and the water flow velocity is lower than in the pressure beak.

Preferably, the transition and connector cone are streamlined so that the water is able to flow in its natural pattern with only a small flow resistance in order to minimize the loss of pressure or velocity from the distribution chamber into an outlet hose. The connector cone has an outlet area which matches the internal area of the outlet hose. The area depends on several factors, such as the height difference between the water surface and outlet and the width of the pressure beak, for example.

The inlet of the pressure beak may form a rectangular aperture opening with rounded sides. The aperture opening is shaped so that only a relatively low water flow-through rate is required to remove the debris. At the same time, the pressure beak is shaped so as, in combination with the distribution chamber, to apply a substantially uniform suction over the entire working area. The pressure beak may have a substantially rectangular cross-section, determined by the aperture opening and working area. The inlet may include a single-curved, rounded inlet funnel extending into the pressure beak. The inlet funnel may have a drop-shaped cross-section. The pressure beak may also be considered as a funnel able to form a transition into the distribution chamber as a circular arc, so that the shape forms a straight line or surface extending to a double-curved surface of the distribution chamber.

The inlet of the pressure beak is formed as an aperture and defines an operating width. The operating width is the horizontal width working against the grid face of the intake. The area of the inlet or aperture and the pressure in the distribution chamber take part in determining the suction capacity along the operating width. The width of the gap opening must be adapted to the expected foreign matter to be removed to prevent clogging of the pressure beak. The width of the gap opening is the same across the entire inlet side of the pressure beak cross- section. Alternatively, the width of the gap opening may be adjusted to adjust the inlet flow velocity of the water if it turns out that the water flowing through the inlet grid flows with different velocity in the different parts of the grid. For example, it will be expected that the water flow velocity is somewhat lower towards the edges. Also, the width of the aperture opening should be larger than the mesh width of the thrash rack so that elements stopped by the thrash rack may still be extracted.

The suction effect is provided using no moveable parts, ensuring good reliability and reducing operating costs. The invention further includes a system for cleaning an inlet grid of a power plant. The system comprises a suction nozzle having an outlet with a pipe stub for connecting to a flexible outlet hose. The suction nozzle has a wedge-shaped distribution chamber including an upper section, a lower section, and two sides extending between the upper and lower sections. The distribution chamber is connected, at a first end, to the pipe stub, and at a second end to a pressure beak. The pressure beak has a first side forming an inlet and a second side connected to a second end of the wedge-shaped distribution chamber. The connector cone is connected to the outlet and to the wedge-shaped distribution chamber. A flexible hose is connected to the pipe stub of the suction nozzle. The hose may be of a type which not easily buckles or forms steep transitions, so that the transitions are smooth and follow the natural path of the water.

In the case of clogging, the pipe is made so as to allow for easy removal of foreign matter that has become stuck.

A guiding system including at least two guiding rails and at least one linear actuator is configured for guiding the suction nozzle in a linear motion along the inlet grid. The outlet hose includes a dirt outlet at a level below the water surface.

The outlet hose may include a valve for controlling the water flow through the suction nozzle.

The linear actuator may be a pneumatic cylinder or another suitable actuator.

Common linear actuators that can be used include hydraulic cylinders, screw mechanisms, pitch racks, chains, etc.

The suction nozzle may also be used in a system in which the inlet grid is itself rotatable, and in which the suction nozzle is mounted in a fixed position below the water surface.

The suction nozzle is also applicable in a system that allows for lateral adjustment, so that the suction nozzle may be used with a grid being wider than the suction nozzle. Thus, the suction nozzle is applicable in systems moving the suction nozzle horizontally, vertically, or in a combination of horizontally and vertically. It is normally considered as advantageous if the suction nozzle can be lifted above water level.

The suction nozzle is also applicable in systems in which the inlet grid is itself rotatable, and in which the suction nozzle is mounted in a fixed position below the water surface.

Guides may extend from a location below or level with the inlet grid, to a location above the water surface at which the suction nozzle may be repaired or inspected. In this manner the suction nozzle can be easily maintained and inspected with no need for divers.

The outlet hose needs to be movable to be able to allow for the motion of the suction nozzle, and have a cross-sectional area adapted for the desired flow throughput. At the same time the outlet hose must have sufficient rigidity so as to not collapse under the pressure differential between the water within the reservoir and the water within the hose. The hose must also exhibit sufficient resistance against wear from the objects extracted from the grid, sufficient fatigue strength, resistance against sunlight, etc. The outlet hose may also be a suitable

combination of a hose and a pipe. The area of the hose will be adapted to the outlet area of the connector cone. A suitable tap or valve may be provided on the outlet hose to close the outlet when the cleaning arrangement is not operating. The valve could possibly also be used for controlling the flow rate through the suction nozzle.

The invention further comprises a system for cleaning an inlet grid to be positioned below a water surface of a pond, with the inlet grid being an inlet grid of a power plant. The system includes at least one suction nozzle for an inlet grid configured for connecting to an outlet channel as defined in claim 1 . An outlet channel includes an inlet from the suction nozzle and an outlet at a point outside the pond at a level below the water surface. The system further includes an assembly for mutual motion between the suction nozzle and the inlet grid.

The assembly for mutual motion between the suction nozzle and inlet grid may include a guiding system including at least two guide tracks and at least one linear actuator for carrying the suction nozzle in a linear motion along the inlet grid, and the outlet hose may include a dirt outlet at a level below the outlet grid.

The assembly for mutual motion between the suction nozzle and inlet grid may include a circular, rotatable inlet grid having an associated drive unit, with at least one suction nozzle being positioned substantially radially outward of a centre of the circular, rotatable inlet grid.

Brief description of the accompanying drawings:

Fig 1 is a schematic side view of a grid cleaner according to the invention;

Fig. 2 shows the grid cleaner of Fig. 1 , seen from a different angle;

Fig. 3 is a top view of a suction unit according to the invention;

Fig. 4 is a cross-sectional view of the suction unit shown in Fig. 3;

Fig. 5 is a front view of the suction unit of Fig. 3;

Fig. 6 is a perspective view of the suction unit of Figs. 3-5;

Fig. 7 is a front view of an embodiment including two fixedly mounted suction units and a circular, rotatable thrash rack;

Fig. 8 is similar to Fig. 7 but the arrangement is seen partly from above;

Fig. 9 is similar to Fig. 7 and Fig. 8 but the arrangement is seen partly from the side and partly through the centre.

Fig. 10 shows the same arrangement as Figs. 7, 8, 9 but the arrangement is shown downstream of the thrash rack; and

Fig. 1 1 shows the arrangement in a cross-section along line A-A in Fig. 9.

Detailed description of an embodiment of the invention with reference to the accompanying drawings: Fig. 1 shows a schematic side view of a grid cleaner according to the invention. The grid cleaner is positioned adjacent to an inlet grid 5 of a hydropower plant. The inlet grid is located in a dam of a pond 8 and is positioned in connection with a penstock 9 of a power plant. A suction unit / suction nozzle 4 is positioned in front / upstream of inlet grid 5. Suction unit 4 is connected to a flexible hose 7 leading to an outlet pipe. The outlet pipe discharges below the water surface of pond 8. The discharge is positioned so as to provide a sufficient pressure head so that the water flow velocity through suction unit 4 is sufficient to ensure a proper absorption of the debris to be removed. The water flow velocity through the suction unit must be significantly higher than the water flow velocity through the inlet grid. The suction unit 4 is mounted in guides 6 so that suction unit 4 is guided at a proper distance from inlet grid 5, and may be carried up and down over the entire height of inlet grid 5. A pneumatic cylinder 3 located above suction unit 4 is driven by an air compressor 2 and controlled by a programmable logic controller, PLC 1 .

Cylinder 3 is connected to suction unit 4, and is able to drive the unit up and down along the height of inlet grid 5. The speed of the pneumatic cylinder can be adapted to the amount of debris to be removed, etc.

Fig. 2 shows the arrangement of Fig. 1 from another angle. Fig. 2 shows two flexible hoses 7 connected to suction unit 4. The guides 6 at each side of the inlet grid extend in parallel with the inlet grid. The pneumatic cylinder 3 is connected to suction unit 4 via a suitable frame 10 making sure suction unit 4 remains oriented at a correct angle relative to the inlet grid.

Fig. 3 is a top view of suction unit 4. From the figure it can be seen how the suction unit is configured as an angled mouthpiece, in which pressure beak 12 transitions into distribution chamber 13 and then into connector cone 14. The connector cone provides an outlet area for a connector piece 18. Connector piece 18 is configured for connecting to the flexible hose and defines an outlet area 17. The line A-A shows the location of the cross-section of Fig. 4. The transitional face between pressure beak 12 and distribution chamber 13 may form a slight break 19, as indicated by a line in Fig. 3. Fig. 4 shows a cross-section A-A as indicated in Fig. 3 of suction unit 4. Typically, the suction unit is made of stainless steel or glass-fibre armed plastic and includes inlet 1 1 and pressure beak 12. Pressure beak 12 defines an aperture having an aperture opening 16. The pressure beak transitions into the tapered distribution chamber 13 which, in turn, extends into connector cone 14 transitioning into the connector piece with outlet area 17 for connecting to a flexible hose. From the figure it is clearly seen how the rounded inlet 1 1 is formed with a rounding which serves the threefold purpose of leading the debris into the mouthpiece without the debris becoming stuck, accelerating the water flowing into the mouthpiece, and adding rigidity to pressure beak 12. From the figure it is also clearly seen how aperture opening 16 is made smaller than the outlet area 17 so as to make sure no objects are allowed to enter which are large enough to clog mouthpiece 4.

Fig. 5 is a front view of mouthpiece 4. Inlet 1 1 is shown with aperture opening 16 and outlet area 17.

Fig. 6 is a perspective view of the mouthpiece shown in Figs. 3-5. From the figure it is clearly seen how the mouthpiece is tapered and how the rounded inlet 1 1 is formed with a rounding which helps leading the debris into the mouthpiece without the debris becoming stuck, makes the water flowing into the mouthpiece accelerate, and adds rigidity to pressure beak 12. The figure also shows how pressure beak 12 transitions into distribution chamber 13 and then into connector piece 18 via connector cone 14 (Fig. 3).

Connector cone 14 (Fig. 3) in the transition between distribution chamber 13 and connector piece 18 may be shaped as a part of a torus to ensure small flow resistance and to reduce the chance that the matter sucked through the

mouthpiece becomes stuck or accumulates in the transition zone.

Figs. 7-12 show an arrangement designed to mount in a frame in pond 8 / the concrete of the dam. In this manner the entire arrangement may be supplied or lifted up and down in its entirety for maintenance and possibly replacement. Fig. 7 shows an embodiment including two fixedly mounted suction units 4 and a circular, rotatable thrash rack 20 as seen in a front view, upstream of the thrash rack. Thrash rack 20 is fixed in a shaft 21 supported downstream of thrash rack 20. Thrash rack 20 is rotationally driven by a low pressure turbine connected to shaft 21 . The low pressure turbine is driven by a low pressure provided via low pressure pipes 24 having outlets below the water surface, in the same manner as the low pressure to suction unit 4. Thrash rack 20 is positioned in front of an outlet of a pond 8. Suction unit 4 is mounted in a suitable fastening rail 22 extending in a radial direction from the fastening point of shaft 21 on thrash rack 20. The mouthpieces of suction unit 4 cover the entire radius of thrash rack 20. In operation, thrash rack 20 is rotationally driven about shaft 21 by the low pressure turbine, and debris will then pass through suction units 4, which will extract the debris. Hence, the radially oriented nozzles of suction units 4 will be able to extract debris from the entire area of the circular thrash rack 20.

Fig. 8 is similar to Fig. 7 but the arrangement is shown partly from above and partly in section A-A of Fig. 9. The circular thrash rack 20 is positioned in front of the outlet from pond 8. To suction units 4 are provided along the radius of thrash rack 20. Thrash rack 20 is attached to shaft 21 , which is rotationally driven by low pressure turbine 23. Low pressure turbine 23 is driven by a low pressure provided by the pressure differential / pressure head between the water surface and outlet of the two low pressure pipes 24.

Fig. 9 is similar to Fig. 7 and Fig. 8 but the arrangement is shown partly from the side and partly through the centre. The positioning of the two suction assemblies 4 along the radius of thrash rack 20 is shown. Thrash rack 20 is attached to shaft 21 , which is rotationally driven by low pressure turbine 23. Low pressure turbine 23 is driven by a low pressure provided by the pressure differential / pressure head between the water surface and outlet of the two low pressure pipes 24.

Fig. 10 shows the same arrangement as Figs. 7, 8, 9 but the arrangement is shown downstream of thrash rack 20. The shaft attachment point of thrash rack 20 in low pressure turbine 23 can be seen together with two drive units 25 powering low pressure turbine 23. Low pressure for drive units 25 is provided through low pressure pipes 24 as explained above. Drive units 25 may be powered in such a manner that one unit provides a driving force and the other unit provides a braking force. The drive unit may include only one jaw sealing against the low pressure turbine and teeth so that the drive unit forms chambers between the low pressure turbine and jaw, being connected to the low pressure pipe. Hence, the drive unit or jaw does not have to comprise moveable parts. This configuration makes it simpler to control the velocity of the thrash rack by, for example, controlling the water flow rate through the pair of low pressure pipes 24. Water circulation through drive units 25 is provided by the pressure differential / pressure head between the water surface and outlets of said pair of low pressure pipes 24.

Fig. 1 1 shows the arrangement in cross-section A-A of Fig. 9. Shown in the figure are the rotational shaft 21 , thrash rack 20, and turbine 23.

Claims

154/JH C L A I M S

1 . A suction unit (4) for an inlet grid of a hydropower plant configured for connection to an outlet channel, and for being positioned upstream of the inlet grid (5, 20), said suction unit (4) being connected to an outlet channel (7) having an outlet below a water surface of a pond (8),

c h a r a c t e r i z e d i n that it comprises:

an outlet including a connector piece (18) connectable to a flexible outlet hose;

a wedge-shaped distribution chamber (13) having an upper section, a lower section, and two sides extending between the upper and lower sections, connected at the first end to said connector piece (18);

a pressure beak (12) having a first side forming an inlet and a second side connected to a second end of said wedge-shaped distribution chamber (13); and a connector cone (14) connected to said outlet and said wedge-shaped distribution chamber (3).

2. The suction unit (4) of claim 1 wherein the inlet (1 1 ) is a continuous opening defined by edges of said pressure beak (12).

3. The suction unit (4) of claim 1 wherein said inlet (1 1 ) comprises a single- curved, rounded inlet funnel extending into said pressure beak (12).

4. The suction unit (4) of claim 1 wherein the second end of said wedge- shaped distribution chamber (13) is rounded in an arc having a radius of curvature, the radius of curvature defining an angle having a vertex substantially coinciding with a vertex of an angle defined by said two sides of the distribution chamber (13).

5. The suction unit (4) of claim 1 wherein said inlet of the pressure beak (12) forms a rectangular aperture opening (16).

6. The suction unit (4) of claim 1 wherein the first side of the pressure beak (12) forms a rounded inlet having a drop-shaped cross-section.

7. An system for cleaning an inlet grid (5, 20) for being positioned below a water surface of a pond (8), the inlet grid (5, 20) being a power plant inlet grid, including an outlet channel (7) having an inlet from a suction unit (4) for being positioned upstream of the inlet grid (5, 20) and an outlet at a point outside the pond (8) at a level below the water surface;

c h a r a c t e r i z e d i n that it comprises:

at least one suction unit (4) according to claim 1 ; and

an assembly for mutual motion between the suction unit (4) and inlet grid.

8. The system of claim 7 wherein the assembly for mutual motion between the suction unit (4) and inlet grid (5) comprises a guiding system including at least two guides (6) and at least one linear actuator for leading the suction unit (4) in a linear motion along the inlet grid (5); and

wherein the outlet hose comprises a filth outlet at a level below the outlet grid.

9. The system of claim 8, wherein the linear actuator is a pneumatic cylinder (3).

10. The system of claim 8 wherein the guides (6) extends from a position below or level with the inlet grid (5) to a location above the water surface at which the suction unit (4) may be worked over or inspected.

1 1 . The system of claim 7 wherein the assembly for mutual motion between the suction unit (4) and inlet grid (20) comprises a circular, rotatable inlet grid (20) powered by a drive unit, and wherein at least one suction unit (4) is positioned substantially radially outward of a centre of the circular, rotatable inlet grid (20).

12. The system of any of claims 7-12, wherein the outlet hose comprises a valve for controlling the water flow through the suction unit (4).