Seawater intake systems and outfalls

                  The Offshore System including the InvisiHead Seawater Intake Head System 
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  Seawater Intake Systems, the InvisiHead  offshore type 

The Elmosa offshore seawater intake system is made up of the InvisiHead-the backbone of the system, the Pipeline whether it is made of steel, steel lined with polyethylene, GRP, concrete, or high density polyethylene (HDPE) pipe, and the NatSep. The omni directional InvisiHead intake head system adds to the performance of the offshore system. It is fitted to the upstream end of the intake system pipeline located some distance into the sea from the shoreline. Entrance velocity is lower than  0.09 m/s (0.3 fps). The approach velocity is extremely slow <<0.002 m/s (0.0065 fps) - the InvisiHead intake head by design and nature of operation becomes hydraulically invisible to marine life and debris. In other words, the intake head does not act as a sink point and therefore does not suck in sediments, marine life, or debris. No impingement or ingress of fish. 

The InvisiHead


Super slow entrance velocities also lead to lower head losses and lower level draw downs at the pump intake basin. The InvisiHead entrance section is hydraulically fine-tuned in lab tests. The entrance dimensions are not arbitrarily selected but hydraulically calculated in multi-dimensional approach and through model setup and testing. Each dimension is a function of the flow velocity. Eddies through this approach are totally eliminated thus head loss at the InvisiHead is reduced to a negligible level of < 0.2 millimeters.

Should the dimensions become out of phase as the case in standard intake head inlets and with the streamlines leaving the approach stage and reaching the entrance (which is usually the case when one of the dimensions like the height or the width is arbitrarily chosen and the other is calculated by dividing the area by the chosen dimension), eddies will form and multiply causing turbulence and flow disturbance at the head entrance. That causes a higher pressure drop that will result in higher suction and thus results in higher sediment entrainment and head loss that causes level reduction at the intake basin, resulting in higher pumping energy. That is why we tune the flow with the height and the circumference of the InvisiHead. Once the three are in phase, the InvisiHead is kept to minimum in size, head loss is kept to minimum and the level drop of water is also kept to the absolute minimum at the the downstream end at NatSep intake basin onshore. When that is done, drastic reduction of sediment and marine life inflow takes place and smaller intake pipelines will satisfy the flow capacity required, smaller and shallower NatSep basins will be needed. All these optimization factors translate into lower initial investment and lower operation and maintenance costs for the intake system and for the overall plant costs - both the initial and the running. The 'three-in-phase' tuning and fabrication made the InvisiHead to be operation and maintenance-free throughout its useful long life time of over 50 yrs.

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