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 Pi{~}VenaContractaOrifice~ is the head loss through the valve.
A function to determine the valve diameter iterates from the smallest possible diameter to the largest diameter, calculating the respective drain times using the time function. The valve diameter function returns the smallest diameter that allows the sedimentation tank to drain within the time defined by the user. The iteration stops once a time no greater than the desired time.
h3. Couplings
The nominal valve diameter is the inner diameter of the slip side of the adapter, and is used to calculate the outer diameter of the slip side. The nominal diameter is also the outer diameter on the threaded side which will be used as the inner diameter for the valve that fits it.
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.
h3. Gate Valves
Gate valves are placed in every bay of every sedimentation tank at-grade to allow for draining. | 