A Bergant

Developments in pipeline column separation experimentation

SummaryThis paper summarises developments in column separation experimentation in pipes at the University of Adelaide, South Australia. An experimental apparatus with a 37.2 m copper pipe of 22 mm diameter has been constructed. A very fast closure ball valve has been developed which provides a closure time of 5 to 10 milliseconds. Two problems in the development of the experimental apparatus are discussed in detail. First, a problem was encountered with the placement of two 150 mm long How visualisation polycarbonate sections in the pipeline. The discrete vapour cavity numerical model is used to simulate the effect of the presence of the polycarbonate sections in the experimental apparatus. Second, problems in obtaining accurate pressure readings from strain-gage type pressure transducers have also occurred. Analysis of the experimental results has led to the development of solutions to overcome these problems when investigating column separation in pipelines.

Developments in multiple-valve pipeline column separation control

This paper investigates novel multiple-valve pipeline column separation control. Experimental investigations have been performed in a laboratory pipeline apparatus. The apparatus consists of an upstream end high-pressure tank, a horizontal steel pipeline (total length 55.37 m, inner diameter 18 mm), four valve units positioned along the pipeline including the end points, and a downstream end tank. The transient event is induced by downstream-end or/and upstream-end valve closures (single- or multiple-valve action). A multiple-valve induced closure event may significantly attenuate the severity of pressure oscillations in the pipeline system. Discrete gas cavity model (DGCM) predictions and measured results for two typical cases including single- and multiple-valve closures are compared and discussed.

Dynamic water behaviour due to one trapped air pocket in a laboratory pipeline apparatus

Trapped air pockets may cause severe operational problems in hydropower and water supply systems. A locally isolated air pocket creates distinct amplitude, shape and timing of pressure pulses. This paper investigates dynamic behaviour of a single trapped air pocket. The air pocket is incorporated as a boundary condition into the discrete gas cavity model (DGCM). DGCM allows small gas cavities to form at computational sections in the method of characteristics (MOC). The growth of the pocket and gas cavities is described by the water hammer compatibility equation(s), the continuity equation for the cavity volume, and the equation of state of an ideal gas. Isentropic behaviour is assumed for the trapped gas pocket and an isothermal bath for small gas cavities. Experimental investigations have been performed in a laboratory pipeline apparatus. The apparatus consists of an upstream end high-pressure tank, a horizontal steel pipeline (total length 55.37 m, inner diameter 18 mm), four valve units positioned along the pipeline including the end points, and a downstream end tank. A trapped air pocket is captured between two ball valves at the downstream end of the pipeline. The transient event is initiated by rapid opening of the upstream end valve; the downstream end valve stays closed during the event. Predicted and measured results for a few typical cases are compared and discussed.