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The linear chemical doser design requires that the alum flow be laminar. The linear flow design Linear Chemical Doser uses the relationship between laminar flow and major losses in the doser tube. This creates a linear relationship between height of water in the grit chamber and the flow of alum,(Linear Chemical Doser). For high plant flow rates, the flow rate of alum will be turbulent. When the flow in the tube is turbulent the linear relationship no longer exists and a nonlinear dose controller is necessary to maintain a constant chemical dose with variations in flowrates.
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