When designing a pipeline for the transport of a liquid one of the problems to be considered is the provision of a device to guard against low pressures. These low pressures can be caused, for example, by a sudden pump failure. The failure creates a negative pressure wave which travels in the downstream direction. Vapor pressure may be reached at a particular point, after which cavitation may occur up a long part of the pipeline. After a certain time the cavitation vanishes causing a very high pressure which may damage the pipeline. In order to prevent the development of cavities and consequently the development of high pressures, a device like an air vessel or surge tank is built. The presence of these devices decreases the pressure waves considerably and increases the time scale af the system. This general procedure for designing a pipeline is greatly influenced by the fact that the phenomenon of cavitation in a long pipeline is badly understood and experiments in this field are rare.
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