Dynamic behavior of a pilot-operated hung-type diaphragm valve in dependence on the pressure difference and excitation duration

To quickly and accurately control high gas flow rates, pilot-operated hung-type diaphragm valves are a viable option. These valves utilize the differential pressure across the valve ports to aid the electrically triggered opening and closing actions. The speed of these actions is a result of a complex interplay of the gas properties, fluid flow, inertia and flexibility of the moving parts. In this study, we used a phenomenological approach to investigate the dynamic behavior of such a valve. A combination of experimental and mathematical modeling was used to evaluate pressure variations within a pressure vessel over a range of pressure differences (28 to 516 kPa) and four durations of the coil excitation (33 ms, 72.5 ms, 107 ms, and 137 ms), resulting in 112 cases. Evaluated key parameters include opening and closing velocities, effective flow area, opening and closing times, and associated delays. These parameters were determined by solving numerically the non-stationary mass and energy balance equations and using the Nelder-Mead optimization algorithm to minimize the normalized root-mean-square error between modeled and measured pressure time courses, ensuring that the model accurately reflects the dynamics of the valve. Depending on the pressure difference across the valve, the results reveal two distinct regimes—proportional and plateau—characterized by pressure thresholds. In the proportional regime, valve opening time and response deteriorate with pressure differences, whereas in the plateau regime they stabilize despite increasing pressures. We also found a threshold marking a transition to inertia-controlled operation at the shortest excitation duration of 33 ms. The studied valve exhibited opening and closing responses of about 27 ms and 19 ms respectively, and an effective flow area up to 307 mm 2 . The coil was energized with alternating current, which is most efficient from the point of needed power, but causes some irregularities that could be mitigated with the help of a microcontroller. • Behavior of a pilot-operated diaphragm valve as a complex dynamic system studied. • Significant effects of excitation duration and pressure on valve dynamics observed. • A simple mathematical model reproduces experimental results within their uncertainty. • A broad range of differential pressures from 28 to 516 kPa considered.