Instability of Pressure Relief Valves in Water Pipes

Abstract

Pressure relief valves in water pipes are known to sometimes chatter when the inlet pressure slightly exceeds the set pressure. While these devices are responsible for numerous fatigue issues in process industries, there is a relatively low number of technical publications covering their performance, especially in heavy fluid applications. The present study is intended as a contribution to the understanding of pressure relief valve dynamics, taking into account fluid-structure interactions. A series of tests were performed with a water relief valve in a test rig. Adjusting the set pressure of the valve to about 30 bars, an upstream pressure varying from 20 bars to 35 bars was imposed, so that the valve opened and the water flow varied from a few m3/h to about 80 m3/h. During the tests, the pipe was equipped upstream and downstream of the valve with static pressure sensors and a flowmeter, the disk lift was measured with a laser displacement sensor, and the spring force was recorded simultaneously. Several fluctuating pressure sensors were also installed in the inlet pipe. Static instability is investigated by comparing the spring force to the hydraulic force. Dynamic instability is observed and it is shown that the resonant behavior of the disk generates an apparent negative pressure drop coefficient at some frequencies. This negative pressure drop coefficient can trigger a dynamic instability in a manner similar to the negative damping effect in leakage-flow vibrations.

An Experimental and Numerical Analysis on the Dynamical Behavior of a Safety Valve in the Case of Two-phase Non-flashing Flow

“…When the valve starts to open, the reaction force of the fluid on the valve disc can be defined by applying the momentum theory [37] with some assumptions which include the considering of a fixed and non-deformable control volume (Fig. 2) with neglecting the unsteady term (deformable volume) since it is has a small influence and these assumptions are supported by previous literature in [38,39], and hence we can write…”

Visual experimental investigation on the stability of pressure regulating poppet valve

“…Misra 17 and Moussou 18 calculated the self-excited vibration of the poppet based on the characteristics of pipeline and the compressibility of the fluid, which indicates that the self-excited vibration occurs due to the coincidence of water hammer, acoustic feedback in the downstream pipe, high acoustic resistance at the control valve and negative hydraulic stiffness at the control valve.…”

Laboratory Analysis of a Piston-Actuated Pressure-Reducing Valve under Low Flow Conditions

“…Other studies have instead highlighted some problems relating to the singular behaviours of these devices, an issue that also concerns different types of control valves [44]. More specifically, some recent studies have shown the occurrence of instability in electronically controlled diaphragm PRVs under low-flow regimes.…”