Benefits of Positive Displacement Oval Gear Flow Meters

Positive Displacement Oval Gear Flow Meters


Oval Gear Flow Meters are an increasingly popular choice for anyone looking for above average water or liquid flow measurement… and they’re truly deserving of the attention they’re getting. The advantages of Oval Gear Flow meters include:


– Cost Effectiveness
– Accuracy
– Ease of Installation, and
– Versatility


At DG Instruments, we have a range of quality Oval Gear Positive Displacement flow sensors and transmitters in stock from Australian-Made experts on fluid flow systems, MacNaught. Our knowledgeable flow engineers can also help answer questions, or help you track down any specific Positive Displacement flow instrument product.


Cost Effectiveness

Positive Displacement flow meters are generally regarded as one of the more cost effective options for liquid flow measurement – delivering the most accurate results for your dollar, and challenging the industry standards for cost of accuracy using modern technology, advanced plastics and metals and solid-state circuitry.



Positive Displacement Oval Gear sensors are individually bench tested using computer-enabled testing facilities, and proven to be accurate within 0.5% of the full-scale range readings. Factory Calibration Certificates are issued for all Flowmeters sold.


Ease of Installation

This is the area where Oval Gear flow instruments have a distinct advantage over many other kinds of flowmeters.

Firstly, Oval Gear flow meters can be installed horizontally or vertically and with flow in either direction, without compromising overall performance.

Oval Gear Flowmeters can also be purchased with a sensor, digital display and in-line meter body (pipe fitting), which can be installed into a pipe systems using threaded connections or various Flanged Connections.

Finally, Oval Gear style Positive Displacement flowmeters have the installation ability for remote readouts – that is, the actual sensor can be installed in the proper location, and the digital display remotely located in a more desirable location, such as on a central control panel.



Though most commonly used for the measurement of water flow, Oval Gear meters also work extremely will with viscous fluids right up to 600 centistokes. For fluids with a Reynolds number greater than 4000, there will be a fully developed turbulent flow regardless of viscosity changes.


7741.92 x ID x V
ID = the pipe inside diameter in inches
V = the flow velocity in feet per second
Cst = the fluid viscosity in centistokes


* To maintain accuracy, the Reynolds number must be above 4000 over the entire flow range. Unlike variable area meters, Oval Gear Flow Meters are not affected by changes in the fluid’s specific gravity – that is, the ratio of the density of a fluid, at it’s temperature, to the density of water at a specified reference temperature.


Many Oval Gear flow meters also use advanced solid-state circuitry, which can operate on batteries without an electrical connection. The batteries can easily be changed upon expiry without damaging settings, and can last up to 3 years!
This option, as well as batch process control, analog output signals and remote readouts offers users a unique level of flexibility.



Because the meter’s gears and axle come in direct contact with the fluid and spin at a velocity proportional to the rate of flow, they will wear over varying times. Meters operating within a high flow range will tend to wear more than units operating within low range, and the resistance and abrasiveness of components in the fluid being measured should also be considered. A neglected Oval Gear will in time have degraded accuracy.


Having said that, Oval Gears are easily replaceable, and turbine or rotameter alternatives also require maintenance for optimal results.


For optimal Oval Gear flow meter performance, avoid using on regularly low flow ranges, for measuring very dirty fluid, or liquids with rocks or debris that might damage the paddles or axle. Always follow manufacturers installation recommendations, and don’t hesitate to contact DG Instruments with any further questions or queries about paddlewheel flowmeter application, installation or maintenance.

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