Water-Hammer Charts for Centrifugal Pump Systems

Water-hammer analysis of centrifugal pumping systems following power stoppage can be greatly simplified and expedited with the use of generalized charts. Charts are presented for determining the time of flow reversal at the pump, the minimum and maximum heads at the pump and at the mid-length of the discharge line, and the maximum head at the pump if reverse rotation is prevented. The graphs are applicable to pumps with specific speeds less than approximately 2,700 (rpm-gpm-ft). Pump efficiency and line friction are included in the charts. An examination of the complete characteristics of centrifugal pumps is presented and a set of complete pump characteristics for use in water-hammer analysis is developed. The effects of pump specific speed on the transient following power stoppage are examined.