Oval Gear Flow Meters - Principles of Operation

The oval gear flow meter comprises oval-shaped, geared rotors which rotate within a housing of specified geometry.  Fluid differential pressure causes the intermeshing gears to rotate, trapping a ‘pocket’ of fluid between the gear and the outer housing and subsequently emptying the fluid pocket into the downstream flow.  Capillary action of the metered fluid forms a liquid seal.  Each ‘pocket’ holds a precise and known volume of fluid so counting the pocket frequency gives a measurement of the volumetric flow rate.  This is typically achieved by embedding magnets in the rotors, which then actuate a reed switch or provide a pulse output as they rotate.