Analysis of Hydraulic Transients in Pipelines Due to Sudden, Linear and Stepwise Valve Closure

Hydraulic transient is a flow condition in which the flow velocity and pressure change rapidly with time. Changing in status of a flow control component (for example, a valve closing or pump stop) cause to the occurrence of transient in the system. There are many methods to analyze transient, in this study, hydraulic transient in a simple pipeline was considered by using the method of characteristics. For this aim a model with two reservoirs, each connected to one end of the pipeline was assumed. The pipeline conveys water from the upstream reservoir to the downstream one. A butterfly valve was set at the downstream end of the pipe. As soon as the valve is closed, either suddenly, linearly or in a stepwise manner, the pressure at the upstream end of the hydraulic line is expected to be constant while the velocity of flow at the valve is expected to be zero. Two pipelines with different materials, namely; stainless steel pipe and ductile pipe were employed in the study. A MATLAB code was developed in order to do the analyses. It was detected that the stepwise valve closure can decrease transients significantly than the sudden and linear valve closure operations. There are two important factors which are the water velocity and the frictional coefficient that have significant effect on the hydraulic transient. The value of transient pressure in ductile pipe is less than it is in stainless steel pipe because of the higher frictional factor. Keywords: Hydraulic transient, pipeline, method of characteristics, sudden closure, linear closure, stepwise closure.