BES Flowmeters supplies positive displacement (PD) flow meters for precise industrial liquid measurement — including the Flomec OM Series oval gear meters and Macnaught MX Series PD meters. Positive displacement flow meters are the preferred technology for viscous liquids, custody transfer and applications where high accuracy is required regardless of flow profile.
How Positive Displacement Flow Meters Work
A positive displacement flow meter measures flow by repeatedly trapping a fixed volume of liquid and passing it from inlet to outlet. The number of fill-and-empty cycles is counted and converted to a total volume and flow rate. Because measurement is based on volume displacement rather than flow velocity, PD meters are accurate across a wide viscosity range and are unaffected by turbulence or swirl — no straight pipe runs required.
Types of PD Flow Meters
Oval Gear Flow Meters
The most common PD meter type. Two oval gear rotors mesh and rotate as liquid flows through, trapping precise volumes with each rotation. Highly accurate (±0.5%), suitable for diesel, oil, chemicals, resins and food-grade fluids. See our oval gear flow meters.
Nutating Disc and Piston Meters
Alternative PD designs for specific applications including water custody transfer and domestic metering.
Applications
Positive displacement flow meters are used for fuel dispensing and monitoring, lubricating oil measurement, chemical dosing, hydraulic fluid monitoring, food-grade liquid measurement and custody transfer billing.
For liquid measurement using turbine technology, see our liquid flow meters. Request a quote or call (03) 5956 8685.
Frequently Asked Questions
A positive displacement (PD) flow meter measures flow by capturing and counting fixed volumes of fluid as it passes through the meter. Each rotation or cycle of the measuring element displaces a known volume, making PD meters highly accurate across a wide range of flow rates — particularly at low flows and with viscous liquids.
Positive displacement flow meters offer high accuracy at low flow rates, are unaffected by flow profile and pipeline installation conditions, and perform well with viscous fluids. They require no external power for basic pulse output versions and are well suited to batch and custody transfer applications.
Positive displacement flow meters are suited to oils, fuels, chemicals, solvents, resins and other viscous or non-conductive liquids. They are not recommended for water or fluids with suspended solids unless specifically designed for that purpose. The Flomec OM series from BES Flowmeters covers a wide range of industrial liquid applications.
An oval gear meter is a specific type of positive displacement meter that uses two oval-shaped gears to measure flow. The gears mesh and rotate as fluid passes through, displacing a precise volume with each rotation. All oval gear meters are positive displacement meters, but not all PD meters use the oval gear mechanism.
Positive displacement flow meters are available in sizes from small (DN6 / quarter inch) for laboratory and low-flow applications up to larger industrial sizes. BES Flowmeters can advise on available sizes across the Flomec OM range and confirm the correct size for your flow rate and pipe size.