SURGE TANK SIZE AND COST CALCULATIONEnter data in blue cells only. Steel cost in cell E15

Virginia Falls5 Flood level at dam, meters 457.00 Low supply level at dam, meters 454.006 Turbine rated head, m 140 Elevation at surge tank tee, meters 432.007 Design full load flow, m3/s 20.24 Upstream conduit length, meters 2100.008 Upstream conduit diameter, meters 3 Average Manning friction coefficient 0.0119 Conduit velocity m/s 2.86 Tank diameter, meters 6.41

10 Elevation top of tank, meters 470.79 Elevation bottom of tank, meters 443.1211 Tank height, top to bottom, meters 27.67 Tank volume, cubic meters 89212 Steel weight in tank and legs, tonnes 58.917 Total height of tank, tee to roof, m 38.7913 Cost of steel tank, millions of US$ 0.339 If in rock, total tank/ris. volume, m3 97114 Rock excavation volume, allowing for a full concrete lining of tank and riser, m3 132315 Concrete lining volume, m3 351 Curved formwork area, m2 662

16 Conduit area, m2 7.07 Steel price $/kg. Erected 5.7517 Acceleration n 0.01265 Deceleration n 0.0104518 Accel. head loss, m 4.67 Decel. head loss, m 3.2619 Acceleration c 0.569 Deceleration c 0.39720 Tank area, F m2 25.19 Tank H/2 above tee. M 24.9621 Acceleration Deceleration22 N acc 29.74 N dec 20.7623 K acc 45.97 K dec 19.6924 y acc. = downsurge = m 5.71 Y dec. = upsurge = m 16.55

Ref: "Estimating weight of steel surge tank" HRW Vol.6, # 4, Sept. 1998, pages 26 - 29.Ref: Hydroelectric Handbook. 2nd. Ed. 1950. W. P. Creager & J. D. Justin, page 734 - 743.

Note - this is a preliminary program, suitable for sizing and costing a restricted orifice surge tank.For a simple tank, with no internal riser and no restricted orifice, increase the diameter by 25%and keep the same high and low water levels. In such a case, the mimimum thickness of steelplate in the tank wall, in millimeters = 21.0 Calculate steel weight manually. A simpletank will be more expensive than a restricted orifice tank due to the larger diameter.