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 inter-meshing 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 and thus flow is measured electronically.

OVAL Gear Flow Meter Advantages

• Traditional proven flow technology
• Simple to install
• No straight pipe runs required so flow meters can be installed in restricted areas

OVAL Gear Flow Meter Limitations

• Not suitable for steam or multi-phase fluids
• Fluid slippage adversely affects accuracy; this varies with flow rate, differential pressure, temperature, viscosity and clearance
• Not recommended for low-viscosity fluids, including water or water-like fluids (because of an increase in fluid slippage)
• Accuracy adversely affected by bubbles present in fluids

The oval gear flow meter is designed primarily for use with higher-viscosity fluids, which has led to applications such as the flow metering of oils, syrups and fuels.