Water-Column Separation at Two Pumping Plants

Results of field measurement of transients in two pump discharge lines show that the pressures were greater than had been predicted during design, and a theory and method of analysis are developed which explains the time-history of the transients measured. The field measurements were undertaken because of the complexity of the phenomena and because very little measured data were available. Results are presented graphically along with analytical solutions. Conclusions drawn were: (a) The inherent difficulty of prediction of water-column separation effects is further complicated by the uncertainty about complete pump operating characteristics and actual moment of inertia of pumps and motors; (b) the effects of air and gases entrained in solution in the water must be considered in the analytical solution; and (c) entrained air can have a detrimental effect on the water-hammer transient, i.e., larger pressure surges in the discharge line and higher reverse speeds of the pumps can be caused by its presence.