A Method for the Economic Design of Penstocks

Abstract

The author presents an original, simple graphic method for the economic design of penstocks. Given a certain flow of water, length of piping, and profile of penstock, curves can be rapidly drawn for pipes of varying diameter which indicate the frictional loss and its value in dollars. Other curves indicate the cost of a certain diameter of piping, which includes such items as the cost of pipe in place, interest, and depreciation. The costs being plotted as ordinates, and the lengths of pipe as abscissas, the total area under a curve representing the summation of these curves indicates the total cost for any diameter of piping selected. It is therefore possible to determine by inspection the most economical system. In view of the large number of variables entering into the problem, it is believed that the method presented should be of considerable help to the designer, and should eliminate guesswork in the selection of suitable pipe diameters.