Why PRVs Tends to Oscillate at Low Flows

A pressure reducing valve (PRV) consists of a main valve and a PRV controller which senses the output pressure and adjusts the opening of the main valve to maintain the outlet pressure at a given set-point [2]. Although it is well known that PRVs tend to oscillate at low flows the problem is not properly understood. This research was motivated by an industrial case-study to remediate instability in the large scale pressure control scheme. The precise cause for the instability has been identified and the measures to improve the robustness of the generic pressure control schemes are proposed.