Coanda Screen

The GUJARAT WEDGE WIRE SCREENS LIMITED intake screen removes rubbish, stones, leaves and aquatic life forms from the flow prior to entering the supply pipe (penstock). This is often a requirement of environmental protection agencies. A poor intake is normally the cause of most hydro turbine system problems. Poor intakes may allow small stones to enter the penstock that can cause serious damage to the Pelton rotor or cause the jets to suddenly block resulting in severe water hammer that can rupture pipe and fittings.

Our GWWSL intake screen is not limited to small hydro schemes; it can also be used for domestic, farm, village and small town water supplies.

Our GWWSL intake screens are designed to provide low maintenance screening solutions for water intakes without the need for any moving parts. The self-cleaning ability and high abstraction flow capacity is due to the shape of the screen and the arrangement of the wedge wires that make up the screen.

The GWWSL screen uses the Coanda effect, which is the phenomena in which a jet flow attaches itself to a solid surface and remains attached, even when the surface curves away from the initial jet direction. The screen is built from wedge-shaped wires that have suitably angled faces to which the flow attaches.

Water is directed over the screen in a fast moving sheet, and the bars deflect it into a tank below whilst debris continues straight on and is washed off by the surplus flow.

Water and some fine silt particles (<1.5mm) pass through the screen, whilst larger silt and debris is excluded and deposited downstream. During times of low river flow the screen capacity may be greater than the available water. Under these conditions debris can build up on the lower parts of the screen. This will be washed off the next time the river flow rises above the screen capacity.

You can order your intake so that the pipe can attach on the left hand side (LHS), right hand side (RHS) or in the central location as shown below. The central option is possible but not advised, unless there is no space for a LHS or RHS fitting.

If possible you should avoid a sharp elbow connection to the intake casing. Once the pipe is connected to the intake it can be concreted over to help protect from floods. It is very unlikely you will ever need to separate the intake tank from the pipe again.

Each complete intake comes with:

• Black roto-molded LDPE casing
• Coanda screen
• Outlet pipe fitting based on your selected size option
• Acceleration plate and securing tube
• Low entry-loss (bell-mouthed) internal fitting
• Vortex breaker plate (only on 1/2 screen version)
• Securing anchors so it can be concreted into position

Screen Specifications:

• Material: 304 stainless steel
• Screen gap: 1.5mm
• Wedge wire tilt angle: 5 degrees 10 degrees 12 degrees
• Wedge wire width: 2.3 mm , 3 mm
• Wedge wire depth: 3mm , 5mm
• Supporting bar: 3mm wide x 5mm deep at 24 mm spacing
• Width x length: 380 mm x 188 mm
• Effective width x length installed: 360 mm x 168 mm
• Screen angle relative to flow rate: 0 to 40 degrees (we recommend 25-35 degrees)
• Approved nominal flow: 8l/s
• Rated load: A person of 100kg can stand on the screen without damage.

Coanda Intake Screen, also called Coanda Hydro Screen, provide self-cleaning with the special geometry based on the Coanda Effect phenomenon. The Coanda screen is capable to enable liquid-solid separation with high filtration performance. The hydro screen prevents the sediment, sticks, rock, and dirt with the small-sized openings with no-moving parts and no power requirement.

How Does It Technically Work?
The curved screen of the Coanda Screen consists of V-shaped wedge wires that are placed in exact locations that will create a Coanda effect for the filtration. These wedge wires have a specific gap and tilt angle relative to each other.

Water flows through this gap between the V-shaped wedge wires by preventing other particles. Thus, this gap and the tilt angle defines both capacity and filtration performance. Also, the curved shape of the Coanda screen helps the filtration process complete accurately by the exerted forces of flow. Unwanted particles such as sediment, rock and stick follow the curved shape with this exerted force. As a consequence, it provides self-cleaning.

In the design of the Coanda Screen, important parameters such as tilt angle, open gap, acceleration plate and curved screen must be taken into account. Because more gaps and high tilt angle cause poor filtration performance but high capacity. Thus, an undesirable situation occurs with ineffective filtration performance.

To avoid this poor filtration performance, important parameters such as gap, tilt angle and curve of the Coanda Screen must be calculated, designed and manufactured accurately for the best utilization of the Coanda Intake Screen. ADENCO is capable to provide accurate and customized design and manufacturing for your applications and requirements with our Coanda Screen Engineers.

Advantages

• Coanda Hydro Screen is an effective solution to get clean water for a wide range of applications. In terms of filtration and usage Water Screen provides significant advantages listed below:
• No-power requirement
• Effective cleaning with outstanding capacity
• Long service life with negligible operational cost
• Self-Cleaning

Advantages

• Customized Coanda Screen design
• Project specific consultancy, retrofitting and troubleshooting
• Integration of Coanda Screen for heavy conditions
• Special surface treatment depending on application
• Protection for Aquatic creatures

Applications
With the high filtration performance and easy usage, Coanda Intake Screen provides clean water for a wide range of application where fluid-solid separation or clean water is required.

The most popular and effective usage of the Coanda Screen is an application in hydroelectric plants. Coanda Water Intake supplies clean water for the hydroelectric plants by preventing harmful materials and protecting turbine blades.

• Hydroelectric Plants
• Drinking Water
• Agricultural Applications
• Snowmaking Machines
• Sewage Treatment
• Dewatering