# Topic: Re: How do you calculate pipe diameter, mixer size and type, and other design parameters?

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Sizing a static mixer is often best handled by the simple approach.&nbsp; In most cases, the diameter of the mixer should be the same size (diameter) as the pipe leading to and from the mixer.&nbsp; The velocities needed for good mixing in a static mixer are similar to the linear design velocities through a pipe.&nbsp; The velocities should be high enough (2 to 3 m/s) to limit the cost of the piping and low enough to prevent excessive pressure losses.&nbsp; Pressure loss through the static mixer may be 5 to 20 times the pressure drop through an equivalent length of open pipe.&nbsp; However, the static mixer for turbulent mixing is short and the added pressure drop is usually not a problem for the pump.&nbsp;With the water flow rates and anticipated velocities, flow should be fully turbulent making rapid mixing quite efficient.&nbsp; Twisted-element or other high-flow, low-pressure drop mixers should be used.&nbsp; High-pressure drop, structured-element mixers are not needed for turbulent mixing.&nbsp; Some static mixers are designed specifically for turbulent mixing.&nbsp; As few as two or four elements may be needed for turbulent mixing.&nbsp;Ideal installation of the static mixer should be with 10 pipe diameters of straight pipe upstream of the mixer and 10 to 20 pipe diameters of straight pipe downstream.&nbsp; Some turbulent mixing is accomplished after the flow leaves the mixer.&nbsp;The injection point ahead of the mixer should be less than a pipe diameter upstream and have multiple (at least 2 or 4) injection points across the pipe diameter.&nbsp; Those points should be located in rough proportion to the cross-sectional area of the pipe.
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