AWMA have custom designed and manufactured over 100m2 of Self-cleaning Flat Panel Screens for New Zealand’s Rangitata Diversion Race (RDR) Fish Screen Replacement Project.
The hydraulic design of the facility meant the downstream end of the RDR screen bay lacks the area required for cylinder intake screens. No alternative solution was available in the market.
AWMA’s R&D team worked closely with project partners to develop a suitable option. CFD modelling was conducted to refine a Flat Panel Screen design with prototypes manufactured and Factory Accepted Testing procedures developed. It is standard AWMA practice to conduct numerous in-house testing protocols on all new designs, to ensure products will perform on site, as intended during design. All AWMA Screens have self-cleaning capability, the Flat Screen was to be no exception. The self-cleaning arm utilises one of AWMA’s latest technologies to drive the mechanism.
Custom-engineered to 3.5m high x 30m long, the screen is fabricated from sections of stainless steel wedge wire medium with a 2mm slot size (aperture). The flat panel screen incorporates an innovative, adjustable baffle system, designed to ensure water drawn through the intake panels has a low and evenly distributed approach velocity across the entire screen surface.
The self-cleaning system is a horizontal travelling, vertical, dual brush arrangement. The automated screen cleaning process is programmed to operate one cycle per week, travelling the full length and then returning, taking approximately 26mins. The frequency of the cleaning cycles can easily be adjusted in line with expected debris levels. The baffle system, combined with suitable aperture sizing and self-cleaning functionality, all contribute to reducing impingement and entrainment on the screen surface. This results in a fish-friendly irrigation diversion that can extract large volumes of water, whilst returning fish safely back to the river.
The AWMA screen solution is site specific, engineered for New Zealand conditions and is consistent with the NIWA fish passage guidelines.
AWMA’s capabilities lie in specialised design and construct projects to develop water control solutions where no suitable options currently exist.
AWMA’s entire fish exclusion screen solution will provide RDR with a total 374m² of screened surface area, over a length of 86m, weighing in excess of 100 tonne.