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Pipe Launder Slope Determination


Determination of slope required to pass a given fluid velocity through a pipe launder of a given geometry


Enter the mill diameter inside the pipe. Most large pipe sizes specified in inches denote the outside diameter. These pipes typically have half inch side walls, so the inside diameter is one inch less than the outside diameter.

Select a flow depth for the launder to run at. Generally use two-thirds full as the practical maximum. Also check the lowest flow conditions if you are laundering a slurry to ensure that the velocity is high enough to avoid solids settling.

This is the Manning 'n' factor. Click here for a list of water-only values , and add a safety factor for laundering slurries.

Select a velocity for this launder to run at. Slurry service typically requires flows between 3-6 m/s to avoid depositing coarse solids. Higher velocity results in higher pipe wear.

This geometry dictates a θ angle of 4.0 radians, 230.8°.
and a half-top (b) dimension of 0.40 metres, 15.81"
Hydraulic radius (Rh) of this geometry is 0.265 metres; 10.4"
Flow (Q) that will pass this launder is 6831.0 m3/h, 30076.9 usgpm
Slope of this launder to achieve desired velocity is 1.6%, 0.91°.
Calculation Backup:
Slope = ( n × V × Rh(-2/3) ) 2

where Slope is height/length, V is m/s and Rh is in metres.
The Manning Equation used here is a commonly civil engineering formula for culverts and canal design. More on Manning equation and its parameters here.
Disclaimer: USE AT YOUR OWN RISK.
Neither the author nor the web host will accept any responsibility for loss or damage caused by use of this program. The program has not been tested under stringent conditions that allow it to be considered robust enough for Engineering use. People using this program must themselves accept responsibility to confirm that results are correct and applicable to the application being calculated.