A SIMPLE PREDICTIVE METHOD OF STEAM PIPE FORCES FROM STOP VALVE CLOSURE

摘要

Piping systems that are subject to a fast closing valve are susceptible to large steamhammer forces. The steamhammer force is a result of high-speed pressure waves propagating through the pipe that create sizeable pressure gradients in the pipe. This paper introduces a simple predictive method of the pipe forces induced by the pressure gradients in a steam pipe resulting from stop valve closure. The case of instant valve closure is also examined for comparison. The assumptions in this analysis are that the stop valve closure is linear, the pressure losses from any bends in the pipe can be ignored, the downstream pressure is constant, the steam flow is at a constant pressure, and finally the pipe walls are rigid at a constant radius. The method introduces functions that are constant along diagonal lines on the time-space graph. The pressure and velocity along these lines can be computed from the initial conditions and boundary conditions. Finally, the pipe forces are calculated using the pressures in the targeted regions of the pipe.