Flow Meters › Positive Displacement Flow Meters › Oval Gear Flow Meter
Oval Gear Flow Meter
A positive displacement flow meter for viscous liquid. Two oval gears mesh and turn as the fluid passes, and each turn moves a fixed volume, so the meter counts volume directly. It reads diesel, fuel and lube oil, resin, and other thick fluids accurately, with no straight pipe run.
- Principle: Positive displacement, two oval gears
- Size: DN10 to DN200
- Accuracy: 0.5% of reading (0.2% optional)
- Viscosity: up to 2000 mPa s, to 5000 on request
- Register: mechanical pointer or LCD; optional pulse
Overview
An oval gear flow meter is a positive displacement meter for viscous liquid. Two oval-shaped gears mesh inside the measuring chamber and turn as the fluid pushes through. Each turn sweeps a fixed pocket of liquid from inlet to outlet, so counting the turns counts the volume directly, with no inference from velocity. That makes the reading steady on thick fluids, where a velocity meter struggles, and accurate to 0.5 percent of reading or better.
It is the meter for diesel and fuel oil, lubricating and hydraulic oil, resin, edible oil, and other clean, viscous, non-abrasive liquids. Because it measures by displacement, it needs no straight pipe run before or after it. A filter upstream keeps grit out of the gears. For a clean, low-viscosity line, a turbine flow meter is the alternative; for mass and density together, see the Coriolis mass flow meter.
Features
Everything here follows from one idea: sweep a fixed volume with each gear turn.
Direct volume measurement
Each gear turn moves a fixed pocket of liquid, so the meter counts volume directly.
Strong on high viscosity
Thick fluid actually helps the seal, so accuracy holds where a velocity meter falls off.
No straight pipe run
Displacement measurement does not depend on flow profile, so it needs no upstream or downstream straight pipe.
0.5% accuracy, 0.2% option
Accuracy is 0.5 percent of reading as standard, with a 0.2 percent build on request.
Pointer or LCD register
A mechanical pointer totalizer reads with no power, or an LCD register adds a pulse output.
Cast iron, steel, or stainless
Cast iron for oils, cast steel for higher pressure, and stainless for corrosive liquid.
Working principle
Two oval gears sit in the measuring chamber and mesh with each other. As liquid enters, the pressure across the gears turns them, and at each part of the rotation one gear seals off a crescent-shaped pocket of fluid between itself and the chamber wall and carries it from inlet to outlet. Each full turn moves a known, fixed volume. The gear shaft drives a mechanical pointer totalizer directly, or a magnet on the gear drives a register and a pulse output, so the count of turns is the volume that passed. Because the chamber meters by displacement, viscosity and flow profile do not bias the reading, which is why it suits thick fluids and needs no straight pipe.
Technical specifications
| Parameter | Specification |
|---|---|
| Measurement principle | Positive displacement; two oval gears, fixed volume per turn |
| Medium | Clean, non-abrasive viscous liquid: diesel, fuel and lube oil, resin, edible oil |
| Size | Flange DN10 to DN200 (above DN200 custom); threaded DN10 to DN50 |
| Accuracy | 0.5% of reading (0.2% of reading on request) |
| Turndown | 5:1, or 10:1 |
| Medium viscosity | 0 to 200 mPa s (normal); 200 to 2000 (high-viscosity build); 2000 to 5000 on request |
| Medium temperature | -20 to +80 C (normal); high-temp build to 150 C (LCD) or 200 C (pointer) |
| Nominal pressure | 1.6 MPa (higher on request for cast steel or stainless) |
| Body material | Cast iron, cast steel, or stainless (304 / 316L); gears cast iron or stainless |
| Connection | Flange (default), thread, or clamp; jacket option for temperature hold |
| Register and output | Mechanical pointer totalizer or LCD; optional pulse output |
| Ambient temperature | -20 to +60 C; humidity 5% to 90% |
| Explosion protection | Intrinsically safe Ex ia IIC T6 (with electronic register) |
Representative specifications; confirm per datasheet for the fluid, viscosity, size, and pressure you need.
Ordering example. Oval gear flow meter, DN50, diesel fuel, 3 to 30 m3/h, cast iron body, mechanical pointer with pulse, flange connection.
Materials and viscosity
Two choices set most builds, the material and the viscosity rating:
- Cast iron. The standard body for oils and non-corrosive liquid: diesel, fuel oil, lubricating and hydraulic oil.
- Cast steel. For higher pressure and lightly corrosive media, where cast iron is not enough.
- Stainless steel. 304 or 316L for corrosive liquid, such as acids, alkalis, and salt solutions, and for hygienic-leaning service.
- Viscosity rating. A normal build covers 0 to 200 mPa s; a high-viscosity build covers 200 to 2000, and cut rotors reach 2000 to 5000 on request, for resin, grease, and heavy oil. Always fit a filter upstream to keep grit out of the gears.
Applications
Oval gear flow meters suit clean, viscous liquid:
- Diesel and fuel oil dispensing and custody
- Lubricating and hydraulic oil metering
- Resin, adhesive, and polymer batching
- Edible oil, syrup, and molasses
- Solvent, ink, and chemical dosing
Application example
Fuel oil transfer. A depot metering heavy fuel oil for transfer found a velocity meter drifted as the oil thickened with temperature. An oval gear flow meter read the oil by displacement, so the count held as viscosity changed, and it dropped into a tight skid with no straight pipe run. A strainer upstream kept scale off the gears, which was the one install detail to confirm.
Related products
Turbine Flow MeterFor clean, low-viscosity liquid at higher flow.
Coriolis Mass Flow MeterFor direct mass and density on the same viscous fluid.
Browse all positive displacement flow meters →
Related applications: Diesel, High viscosity.
FAQ
How does an oval gear flow meter work?
Two oval gears mesh in a measuring chamber and turn as the liquid passes. Each turn carries a fixed pocket of fluid from inlet to outlet, so counting the turns counts the volume directly. The gear shaft drives a pointer or a pulse register, which reads the total and the rate.
How accurate is an oval gear flow meter?
Accuracy is 0.5 percent of reading as standard, and 0.2 percent on request. Because it measures by displacement, the accuracy holds across viscosity and temperature, which is why it suits oils and other thick fluids.
What is a positive displacement flow meter?
A positive displacement meter traps a known volume of fluid and counts how many times that volume passes, rather than inferring flow from velocity. The oval gear type is one of the most common, alongside the rotary piston and the nutating disc.
Can it measure high-viscosity liquid?
Yes. A normal build covers up to 200 mPa s, a high-viscosity build to 2000, and cut rotors reach 5000 on request, for resin, grease, and heavy oil. Fit a filter upstream to keep grit out of the gears.
Does it need a straight pipe run?
No. Because it measures by displacement rather than velocity, it needs no upstream or downstream straight pipe, which makes it easy to fit in a tight skid. A strainer upstream is the one fitting to add.
Request a quote
Send us the fluid, the viscosity, the size, the flow range, and the pressure, and we set the body material, the rotor, and the register.