DESIGN CRITERIA FOR EXPOSED .PENSTOCKS

Abstract

Penstocks are pressure conduits for the conveyance of water from reservoirs or surge tanks to hydraulic turbines. They should be hydraulically efficient to conserve available head and structurally safe to prevent failure and loss of life or property. Exposed penstocks are Installed above the terrain surface and supported on anchors and saddles. Such penstocks are preferred keeping in view the possibility of continuous and adequate inspection, the lesser cost of installation and the ensured safety against sliding with properly designed anchorages. The penstock shell thickness is designed by the well known thin cylinder formula considering the maxi urm Internal water- pressure causing the. hoop stress. Assessment of maximum water pressure is complicated by the phenomenon of water hammer caused when the rate of flow In a conduit is rapidly changed. The effect- of water hammer in the design has been discussed. The variation of hoop stress due to large diameter of penstock is taken to account in the design, as per Mr. Herman Schoyer. Various design principles for supports and anchors,, Air Inlet valves, banded and mutt :l aver constructions, have been critl-cally reviewed. The design criteria for exposed penstock have been detailed out with tables, graphs and sketches. Numerical examples have been included to clarify the principles of design.