h1. Sedimentation Drain Design
h3. Drain Sizing
The time it takes to drain the sed tank can be approximated by:
\\
{latex}
\large
$$
desiredT = {{16W_{SedBay} \^{1.5} \tan (AN_{SedPlate} )^{0.5} L_{Sed} } \over {3\pi D_{Valve} \^2 \sqrt {2g} }} + {{\sqrt {HW_{Sed} } - \sqrt {{{W_{SedBay} } \over 2}\tan (AN_{SedPlate} )} } \over {{{\pi D_{Valve} \^2 } \over {8L_{Sed} W_{SedBay} }}\sqrt {{{2g} \over {Pi_{VenaContractaOrifice} }}} }}
$$
{latex}
\\
where W{~}SedBay~ is the width of a single sedimentation bay, AN{~}SedPlate~ is the angle of the bottom slopes from the horizontal, L{~}Sed~ is the length of the sedimentation tank, D{~}Valve~ is the diameter of the drain valve, HW{~}Sed~ is the water height in the sedimentation tank, and PiK{~}GateValve~ + K{~}VenaContractaOrifice~Exp~ is the total head loss through the valve.
AFor functionany togiven determinetime, the idealized valve diameter iteratesmay from the smallest possible diameter to the largest diameter, calculating the respective drain timesbe calculated using the timeabove functionequation. TheThis valveidealized diameter functionis returns the smallest diameter that allows the sedimentation tank to drain within the time defined by the user. The iteration stops once the calculated diameter drains the sedimentation tank at least as fast as the desired time.rounded up to the next possible nominal diameter.
h3. Couplings
The calculated nominal diameter is that of the slip side of the adapter and is used to calculate its corresponding inner and outer diameters. The outer diameter of the slip side is also the inner diameter of the threaded side. The outer diameter of the threaded side is used as the inner diameter of the valve which fits it.
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h3. Drain Slopes
Since the center of the valve is aligned with the floor of the sedimentation tank, slopes are required in the floor of the tank. The slopes have a width equal to the diameter of the valve and a depth equal to half the diameter (placing the center of the valve at-grade) with a slope of 30 degrees.
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h3. Gate Valves
Gate valves are placed in every bay of every sedimentation tank at-grade to allow for draining.
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