NUMERICAL AND EXPERIMENTAL INVESTIGATION OF HYDRAULIC TRANSIENT IN A PETROLEUM PIPELINE

Abstract

Hydraulic transient (HT) is an important phenomenon that leads to unfavourable consequences in pipeline network system because of changes in operational status of flow control components such as pumps or valves. HT leads to the development of pressure surge in the pipeline that also results in damaging the pipeline components or total network failure. The aim of this research is to carry out numerical and experimental investigation of HT in a petroleum pipeline. The pipeline under investigation transports refined petroleum products namely; Automotive Gas Oil (AGO), Dual Purpose Kerosene (DPK) and Premium Motor Spirit (PMS). WANDA simulation software was used to carry out the numerical investigation of the HT in the pipeline and an experimental rig was used to carry out the experimental investigation of the HT in the pipeline. The pressure head and the velocity head of the petroleum pipeline network were analysed. Pressure heads of 0.117034 m, 0.115151 m, and 0.107164 m were recorded at the node just immediately after the pump for AGO, DPK and PMS respectively. This showed that the node just immediately after the pump experiences more load due to weight of the fluids. The research also revealed that the velocity head is high at the node just after the upstream tank and before the pump. The research also revealed that velocity head reduces along the downstream side of the network. The fluid particles at the nodes upstream of the pump require more energy to move down the downstream during steady state flow condition. The pressure surges developed due to sudden valve closure and pump failure were simulated for various calculated valve closure times using the simulation software for AGO, DPK and PMS. The result of the simulation analysis showed that worst case scenarios due to the sudden valve closures are the development of excessively high positive pressure and negative pressure of 1419kPa, - 98kPa (AGO), 1461kPa, -99kPa (DPK) and 1321kPa, -52kPa (DPK) were experienced at the node just before the flow control valve (node F) and the node just before the pump (node B) respectively against an operating pressure of 1034kPa of the nodal sets .In addition, the worst-case scenario experienced for pump failure is drop in pressure below atmospheric and below the vapour pressure of the fluids being transported at nodes just before the pump and the nodes just before and after the non-return valve for all the fluids. Hence, the formation of cavitation and column separation at these nodes. At the end of the research, a safe marginal valve closure rate (MVCR) range of 0.0006m/s to 0.0025m/s was established for a standard pipe of 0.3556 m (14 inches) diameter. In addition, experimental analysis was carried out using a transient test rig to validate the simulated results.