Customer: ABB

Product/Service Supplied: Consultancy - physical modelling. Model studies of the Cooling Water Pumphouse and the Syphon Seal Weir were undertaken.

Problem/Background: Hydraulic performance assessment was required for two of the hydraulic structures being designed as part of this plant.

Objectives/Approach: The objectives of the pumphouse model study were to investigate flows through the two cleaning streets (bar screens and band screens) and to the three pumps over the full operating range, paying particular attention to:

• Turbulence and air entrainment
• Potential forformation of vortices at pump inlets
• Swirl in pump inlets
• Likelihood of solids accumulation in the pumphouse

The objective of the syphon seal weir model was to assess the hydraulic performance of the structure (head vs discharge etc) to compare with design predictions. Physical models (1:12 scale) of both structures were constructed and tested.

Solution: The test programme on the pumphouse model demonstrated that vortex formation was a potential problem but this could be resolved by addition of benching on the rear wall of each pump cell. The client accepted the level of swirl recorded in the pump inlets. Tests on the seal weir model indicated performance very close to that predicted, and no modifications to the design were recommended. Observations made during the test programme highlighted that part of the structure would be exposed to significant forces from a high velocity jet. Recommendations were made to check its capability to withstand such forces.

Benefits:

• Demonstration of performance of the structures over full operating range
• Confirmation of adequacy of designs
• Development and testing of modification to ensure adverse flow conditions avoided
• Indication of possible structural problem under hydraulic conditions

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