Active Spillway is a fully automatic spillway crest gate
Features include:
- Automatic opening and closing
- Free water surface to pass debris
- Controlled release of water
- Lowered transmittal of forces for greater stability
- Release of water by the gate is progressive
- Active Spillway only operates at levels above full storage level
- No operator intervention, power supply or control equipment is used
APPLICATIONS
Active Spillway is designed to use on dam spillways, reservoir walls, lake outlets and weirs in rivers and canals. It is self-opening and self-closing regulating releases of water. The higher the upstream water level the further the gate opens ensuring stable operation at all times.
CONFIGURATION
Active Spillway is an automatic flap gate located on the upstream edge of the crest of the spillway. The face of the gate is at 60 degrees to the horizontal in the closed position and rotates downstream to open. Counterweights located upstream and below the hinge of the gate are attached to arms extending from the framework of the gate. The counterweights are manufactured in reinforced concrete and are eight-sided in cross-section to provide a stable flow pattern. Watertight seals are located along the bottom edge and sides of the gate.
The gate is supported by the pivot which consists of a horizontal round bar fixed along the bottom edge of the gate. The round bar rests on a rubber seal supported in a stainless steel channel bolted and grouted into the top of the spillway wall.
The gate transmits the horizontal and vertical forces through the pivot to the reservoir wall.
Automatic opening and closing – Free water surface to pass debris – Controlled release of water – Lowered transmittal of forces for greater stability – Automatic gate and is always operational – No operator intervention – Release of water by the gate is progressive – No control equipment – Active Spillway only operates at levels above full storage level – No power supply – Active Spillway ensures there is never any loss of storage
OPERATION
Active Spillway operates on the principle of balancing the moments arising from hydro-static pressure acting on the face of the gate in the one direction, and the force of gravity on the counterweight in the opposite direction.
Active Spillway is designed to start opening when the water reaches 100mm to 200mm above full supply level. The gate opens in response to rising water levels in small incremental openings until the fully open position is reached, or the water stops rising. During this period the inflow into the reservoir exceeds the outflow. This allows for safe flood routing through the reservoir. As the level of the water recedes Active Spillway closes with an identical stage discharge relationship as during the opening phase.
Active Spillway is controlled and operated by the pressure of the water on the face of the gate, which is dependent only on the water level of the reservoir. Active Spillway is therefore an AUTOMATIC gate and is always operational. No operator intervention, power supply or control equipment is used. This makes the Active Spillway ideal and safe for installations in all locations. The release of water by the gate is progressive and sudden discharges cannot occur under any circumstances.
Active Spillway requires the downstream face of the gate to be vented. Ducts installed in the side walls or the piers ensure that the air behind the gate can communicate freely with the atmosphere at all times.
Active Spillway only operates at levels above Full Storage Level (FSL) and closes before the water level in the reservoir again reaches FSL. This ensures there is never any loss of storage and the yield of the reservoir is maintained.
DISCHARGE
Active Spillway can be used for reservoirs and weirs. It relies solely on the pressure exerted by the water on the face of the gate to operate, guaranteeing fail-safe operation.
Active Spillway is hydraulically stable.
SPILLWAY CAPACITY
Active Spillway can be configured for specific applications to achieve the most beneficial “Stage – Discharge” relationship.
When attenuation is desirable we can design the gate for a steeper curve, and where freeboard is critical a flatter curve can be achieved.
An example where freeboard is limited, is at the gate we installed at the forebay end of the canal feeding into the Merino Hydropower Station. The gate diverts the 28m3/sec flow in the canal into a bypass canal when the power station shuts down.
The criteria specified were:
- open within the 4 seconds closing time of the wicket gates
- limit the increase in water level in the canal to under the 300mm freeboard available
The Active Spillway gate installed is 10m wide x 1.5m high. It opens within 250mm and has successfully operated more than 2000 times since commissioning without any signs of wear and tear
Model studies determined the stage discharge curve (below) for a typical application. This graph reflects the spillway characteristics of Active Spillway as measured from the new full supply level.
Gate 10m wide x 1,5m high
MANUFACTURE
Active Spillway is of robust design with the face plate a minimum of 8mm thick. A professional structural engineer checks the design and carries out stress and deflection analysis. The gates are manufactured in accordance with our specifications:
| Gate and lever arms | Coated mild steel Grade EN 10025: 1993 S355JR |
| Counterweight | Reinforced concrete |
| Hinges and fasteners | Stainless steel |
| Side seal | EPDM music note seal |
| Horizontal seal | EPDM seal in stainless steel “U” channel |
| Sealing plates | Stainless steel |
CONCLUSION
Active Spillway is a unique gate that works automatically, always opening and closing through the same stage heights, guaranteeing fail-safe operation.
Active Spillway can be used on reservoir walls and weirs provided there is enough depth upstream of the wall to accommodate the counterweight.
