Abstract:

ESDU 86015 gives a graphical method for estimating the time-dependent pressure changes and piping forces that follow from a rapid valve closure in a one-pipe system of constant cross-section carrying superheated steam. The method also assumes a frictionless flow and ignores wave steepening effects.

A computer program is provided which applies to any gas that obeys the perfect gas law, and takes into account the effects of both wall friction and wave steepening. In that case sections of the pipeline can have different cross-sectional areas and that can be used to treat a pipeline with branched ends. Worked examples are included for both methods and in the case of the computer program show specimen print-out of the input data, and of the output which includes the time variation of pressure, velocity and density at three points in the pipeline chosen by the user together with values of maximum and minimum pressure at 25 points (a value that is also open to choice by the user). The example is run for a valve with a linear variation of area with time, and for one with a non-linear characteristic.