Hydraulic rams : a comparative investigation

A mathematical model describing the essential features of hydraulic ram operation is developed in order to clarify the possibilities and limitations of the ram relative to its site and its adjustments. The model distinguishes three different periods in the pumping cycle of the hydraulic ram: acceleration - retardation - recoil. Making use of the theory of unsteady flow in pipelines, for each period the relation between velocity and time is derived for the water in the drive pipe of the hydraulic ram installation. Ultimately, from these relationships mathematical expressions are obtained for the time rate of pumping of the ram and for the supply flow required to operate the ram. It is shown that the model is sufficiently accurate to yield at the least a qualitative explanation of the effect of the various parameters governing the performance of the hydraulic ram. For calculation purposes the mathematical model is modified to some extent in order to improve the description of the phenomenon governing the motion of the water during the period of retardation. Laboratory tests were taken on twelve commercially-available hydraulic rams in order to determine their specific performance characteristics. To enable mutual comparison the results are partly presented in a non-dimensional form.