Pressure surge in pipelines

Pipeline with check valve and flow control valve 

If the valve is closed more quickly, the pressure rise will be correspondingly greater. It might be thought that if the valve were closed instantly the pressure rise would be infinite. This is not the case. When a valve is closed suddenly, a pressure wave propagates upstream at approximately the speed of sound in the fluid and only the fluid through which the pressure wave has passed is decelerated thus the pressure rise is finite because the speed of sound is finite. 

Equation 10.35 is the form of equation 6.65 for the particular case of isentropic conditions, denoted by the subscript s. Being less compressible 

It is convenient to introduce the bulk modulus K of the fluid, defined by 

the speed of sound is related to the bulk modulus by 

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Four aspects of unsteady fluid flow will be considered in this chapter quasi-steady flow as in the filling or emptying of vessels, incremental calculations, start-up of shearing flow, and pressure surge in pipelines. 

In some cases, it will be necessary to terminate the transfer in a more gradual fashion, eg by limiting the closure rate of the isolation valve, to avoid damaging pressure surges in upstream pipelines. Due allowance should be made for the delay in stopping the transfer when establishing the tank rated capacity. For some fluids, the tank rated capacity may also serve to provide... 

Pressure surge can be controlled by the use of surge vessels connected to the pipeline with a gas space above the liquid. If a pressure surge passes along the pipeline, liquid flows into the vessel through a check valve and the gas is compressed. Another valve then lets out the liquid at a controlled rate. This type of arrangement is used in large hydraulic lines. 

For smaller hydro power systems, such a solution is considered to be complex and additionally a danger exists of rapid control valve movement introducing damaging surge pressure waves in the pipelines or instability in the overall control system (Roberts, 2002). A preferable solution to maintain frequency close to its nominal value is the utilisation of load control. For the implementation of this scheme, secondary or even dump controllable loads are switched on and off, according to frequency-deviation measurements. 

The swings in the vapor flowrate are typically quite significant to achieve tight pressure control. In an isolated column environment or when this vapor stream simply flows into a large vapor surge vessel or into a large pipeline (header), the variations in the flow cause no problem. But, if this vapor stream is the feed to a downstream unit, the flow variability can significantly disturb this unit and can result in poor plantwide control performance. 

When corrosion is caused by mechanical factors, say, vibration, all the noticeable points at which vibration would affect the facility have to be supported by the use of dampers in order for the facility not to have scratches, which would be the major source of corrosion. On joints and at points where pressure surges would occur, the use of expansion bellows should be encouraged in order to allow for high enough pressure that could burst a pipeline, and also to reduce the effects of the pressure that would have in turn caused much of the vibration. 

Surging Pressure rise in a pipeline caused by a sudden change in the rate of flow or stoppage of fiow in the line. These changes of pressure cause elastic deformation of the pipe walls and changes in the density of fluid column. 

Foster, R. S. (1998). Analysis of surge pressures in the inland feeder and eastside pipeline. Proc. Pipelines in the Constructed Environment, Proc. 1998 Pipeline Div. Conf., Aug. 23-27, San Diego, CA, 88-96, ASCE, Reston, VA. 

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