de Leeuw, Gert Johannes Schreuder (2007) Analysis of hydraulic transients in pipeline networks. [USQ Project]
[Abstract]: For most piping systems the maximum and minimum operating pressure occur during transient operations. Transient operations may result in column separation which refers to the breaking of liquid columns in fully filled pipelines. This may occur in a water hammer event when the pressure in a pipeline drops to the vapour pressure at specific locations such as closed ends, high points or knees (changes in pipe slope). The liquid columns are separated by a vapour cavity that grows and diminishes according to the dynamics of the system. The collision of two liquid columns, or of one liquid column with a closed end, may cause a large and nearly instantaneous rise in pressure. This pressure rise travels through the entire pipeline and forms a severe load on hydraulic machinery, individual pipes and supporting structures. The situation is even worse due to the fact that one water hammer event may cause many repetitions of cavity formation and subsequent cavity collapse. The magnitude of this pressure amplitude may result in high fatigue loading on the pipe and cause the pipe to fail over time due to fatigue.
It is therefore essential for a good design to perform a transient analysis for normal start-up and shutdown and for unplanned events such as a pump trip associated with a power outage. The analysis of hyraulic transients has historically been a difficult and time consuming undertaking. It developed through various stages from the early 1900's from a graphical method to today's fully interactive computer based software that can model the transients in real time.
This paper reviews water hammer with column separation from the development of mathematical models of the phenomenon in the early 20th century to the current numerical solutions techniques used in modern software such as the Method of Characteristics and Wave Characteristic Methods. A list and discussion on a wide range of transient mitigation methods and strategices are presented and reviewed. This list ranges from direct actions and devices such as surge anticipating control valves to indirect and passive mitigating techniques such sequencing of pump start ups.
The paper aims to present a structured procedure whereby a pipeline can be analysed and married with an appropriate transient mitigating strategy.
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|Item Type:||USQ Project|
|Item Status:||Live Archive|
|Faculty / Department / School:||Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering|
|Date Deposited:||28 Feb 2008 00:40|
|Last Modified:||02 Jul 2013 22:59|
|Uncontrolled Keywords:||hydraulic; transient operations; pipeline; liquid columns; water hammer|
|Fields of Research :||09 Engineering > 0905 Civil Engineering > 090509 Water Resources Engineering|
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