Riser-Relief Valve Dynamic Interactions

Abstract

The dynamic stability behavior of a typical pilot-operated relief valve has been investigated both numerically and experimentally. The valve piston equation of motion has been solved in connection with the conservation equations of the oscillating flow in the attached riser. The boundary condition at the riser tip is of a choked flow type and had to be given special attention in oscillatory flows. Pertinent quasi-steady flow equations have been formulated to describe the different phases of relief along the piston lift. A model describing the process of pressure relief is described briefly, followed by a parametric study of the effects of various factors on the oscillation levels and characters. Field measurements were taken on an NFS 8 pilot-operated dual-outlet relief valve mounted on a riser assembly of L/D = 15 in a natural gas compressor station.