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Sedimentation
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Drain Design
Drain Sizing
The time it takes to drain the sed tank can be approximated by:
| Wiki Markup |
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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
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W
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SedBay is
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the
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width
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of
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a
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single
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sedimentation
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bay,
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AN
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SedPlate is
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the
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angle
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of
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the
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bottom
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slopes
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from
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the
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horizontal,
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L
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Sed is
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the
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length
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of
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the
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sedimentation
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tank,
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D
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Valve is
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the
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diameter
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of
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the
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drain
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valve,
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HW
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Sed is
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the
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water
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height
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in
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the
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sedimentation
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tank,
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and
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K
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GateValve +
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K
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Exp is
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the
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total
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head
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loss
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through
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the
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valve.
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For
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any
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given
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time,
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the
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idealized
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valve
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diameter
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may
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be
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calculated
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using
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the
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above
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equation.
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This
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idealized
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diameter
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is
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rounded
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up
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to
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the
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next
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possible
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nominal
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diameter.
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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.
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.
Gate Valves
Gate valves are placed in every bay of every sedimentation tank at-grade to allow for draining.
