Abstract

In this paper the stability of pressure relief valves and pressure reducers is analysed. MacCloy and Merritt have previously proven that the stability analysis of these two components can be viewed with the same calculation. The purpose of this paper is to extend their results to other pressure control components and to add some other views of stability analysis using a simplification of the dynamics linked to the generally small volume of the counter reaction chamber. This simplification leads to a third order transfer function, which is easier to analyse. The static behaviour of both the pressure relief valve and the pressure-reducing valve is explained using this transfer function. A proof is given that the eigenvalues are heavily coupled using the roots calculation of a third order polynomial function. The analysis shows that the inner mechanical control loop of these two components can be viewed as a PD force controller. Root loci are used to understand the stability influences of certain design parameters. Other basic rules are also established.

Keywords: pressure relief valve, pressure reducing valve, stability problems, force control, pressure components