On the analysis of pressure transients in pipelines carrying compressible fluids

Abstract Pressure transients in pipelines are triggered by various events, some of which are accidental and others form a part of operational and safety procedures. Nevertheless it is important to determine beforehand the pressure increases, the velocity changes and the forces that these transients cause, so that the consequent vibrations and stresses can be calculated in order to ascertain the integrity of a pipeline. This paper is concerned with the analysis of transients in pipelines carrying compressible fluids. The procedure adopted is based on the method of characteristics (MOC). A tandem technique has been developed here, first to operate on the main nodes of any complex piping network and subsequently to analyse each individual pipeline to determine the state of the fluid at different sections in the circuit at the end of a preselected time step. A general purpose computer code based on this technique has been developed. The time-history of pressures, velocities and densities can be calculated with the help of this code for any complex piping network. The program is very versatile and can handle any number of pipes, nodes, branches, valves, etc. Sudden operations like opening or closing of valves, slamming of check valves or rupture of pipelines, etc., in a circuit have been simulated. A case study to predict pressure transients in the main steam pipeline of a 500 MW thermal power station, in the event that the load on the turbine is suddenly removed and the main stream stop valves are rapidly closed, has been undertaken and is illustrated in this paper.