Function Testing of Passive Explosion Isolation Flap Valves
Abstract
Passive isolation flap valves are relatively simple devices that are widely used in the process industries. However, as an explosion mitigation technique, they function only within well-defined conditions and the physics at stake make their definition challenging. INERIS method and findings are presented in the current paper. They concern passive flap valves tested on 1 and 10 m3 vessels with pipes of diameters of 150, 300 and 800 mm. The relatively simple configuration of a flap valve connected to a vented vesselstraight duct arrangement is considered. The initially opened flap valve is triggered by the explosion in the vessel and must close within a delay, short enough to prevent the flame passing. Before valve closure, the flow is accelerated by the explosion and large velocities can be reached in the duct (typically on the order of 200 m/s with a vented vessel, but as much as 800 m/s is possible). Upon valve closing the kinematic energy of the flow is converted into heat and pressure in front (on the explosion side) of the valve while a depressurisation is observed behind it (on the isolated side). Typically, a factor of 4 between the pressure in the vessel and the pressure measured at the valve can be observed. Phenomenological modelling is used in extension to a parametric experimental study to investigate the limits of the valve, its possible installation distances and a practical method for dimensioning is proposed.
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