RISER-RELIEF VALVE DYNAMIC INTERACTIONS

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