REV02485 - Laserfiche WebLink

Home Browse Search

- :: ~~~.r.. . . ~.:r ..:.~, 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 for 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 4760 Maximum desirable level in NW Intake Pool Elevation Flaw line 4758 ND Discharge Pipe - R~r, ~,,~.~Q~ ¢~,S a7'fai ,,,. Available Head Causing Flow 2 Feet '~ besion Flow 350 gpm Pipe Diameter -Steel Pipe . ~ 8 inches Inside Diameter 7.9 inches Area 0.340 SF Velocity 2.29 fUsec / y~j Pioe Lenoth Mine to Elbow 170 ~' e Elbow -Equivalent Length 20 " ~ Total 190 / Loss in Pioe 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 100 ~ 0.06 Feet r/ 0.45 Feet`per 100 Feet A.33~Feet, q I ~ 90 Feet 200 Steel Pipe C= 100 Friction loss in pipe = f f = 0.2083(100/C)^1.85' q^1.85/d^4.8655 0.43 Feet per 100 Feet Total Loss in pipe 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 sudace 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 ifs capacity would be greater. 01/01