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• Figure 14-10 North Decline Mine Discharge System Flow Calculation Determine the pipe size for the North Decline Mine discharge pipe assuming a steel pipe and 350 gpm. Reference Figure 14-8 Tor piping arrangement. • • Flow through a pipe is determined by the amount of head causing flow and the head loss in the pipe resisting flow. Flow rates are calculated by trial and error by varying the pipe size so the head causing flow equals or exceeds the head loss in the pipe system. Experience is used to assure the flow rate is reasonable for the pipe size. Available Head Elevation Maximum Pool Elevation Flow line Available Head Causing Flow Design Flow Pipe Diameter -Steel Pipe Inside Diameter Area Velocity Pipe Length Mine to Elbow Elbow -Equivalent Length Total Loss in pipe Steel Pipe C= Entrance loss k(v^2)/2g Friction loss in pipe = f f = 0.2083(100/C)^1.85' q^1.85/d^4.8655 Total Loss in pipe Pipe Length Elbow to Free Surface under access road Loss in pipe Steel Pipe C= Friction loss in pipe = f t = 0.2083(100/C)^1.85' q^1.85/d^4.8655 Total Loss in pipe 4760 Maximum desirable level in NW Intake Pool 4758 ND Discharge Pipe 2 Feet 350 gpm 8 inches 7.9 inches 0.340 SF 2.29fUsec 170 20 190 100 0.06 Feet 0.45 Feet per 100 Feet 0.93 Feet 190 Feet 200 100 0.43 Feet per 100 Feet 0.86 Feet 200 Feet Conclusion: Head loss in pipe from mine to elbow is much less than the available head. Therefore an 8-inch diameter steel pipe will handle the 350 gpm design flow. Elbow to free surtace drops 4 feet so there is no effective head loss. Therefore a 8-inch diameter steel pipe will handle the 350 gpm design flow. PVC pipe may be utilized. PVC pipe has less friction loss than steel pipe so its capacity would be greater. 01 /01