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Oval Gear Flow Meter Working Principle: Rotating Volumetric Pocket Physics
Quick Answer
An oval gear flow meter measures liquid volume by counting fixed pockets of fluid. Two oval gears rotate inside a precision chamber. Each rotation delivers a known volume. This positive displacement principle suits diesel, fuel oil, lube oil, and high viscosity chemicals. You get 0.5 percent or 0.2 percent accuracy without long straight pipe runs.
How Rotating Volumetric Pocket Physics Works
Fluid enters the measuring chamber through the inlet port. The pressure difference across the meter pushes two oval gears. The gears rotate in opposite directions. A precise crescent shaped pocket forms between each gear and the chamber wall. Each pocket traps a fixed liquid volume.
One full rotation of the gear pair moves four pocket volumes from inlet to outlet. The number of rotations is directly proportional to the liquid volume. A sensor detects gear rotation with a magnet and reed switch or a Hall effect sensor. The transmitter converts this into a pulse or 4-20 mA signal.
That process is the core of rotating volumetric pocket physics. The pocket geometry is machined to tight tolerances. That feature allows the meter to measure high viscosity liquids like 380 cSt fuel oil without losing much accuracy.
Why the Volumetric Pocket Principle Matters in the Field
Most engineers skip this part. Turbine meters lose accuracy when viscosity changes. An oval gear meter does not. The fixed pocket volume gives true volumetric readings. That matters for batch dosing and custody transfer on industrial sites.
We have seen that problem on customer sites many times. A paint manufacturer in Vietnam had a turbine meter reading unstable values for resin at 25,000 cP. They switched to a Silver OG-40 oval gear meter. The reading stabilized within 0.5 percent.
Key Parameters and Recommended Models
Silver Automation Instruments offers the Silver OG series for this principle. The common sizes run from DN15 to DN200. Accuracy is 0.5 percent of rate as standard and 0.2 percent as an option. The standard flow range depends on size. A DN25 meter covers about 1 to 10 m3 per hour for diesel. A DN50 meter covers about 8 to 60 m3 per hour.
The body material can be cast steel, 316L stai
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For diesel generator set fuel monitoring, most customers choose a DN20 or DN25 meter with pulse output. For chemical batching, choose a stainless steel body with PTFE seals and 4-20 mA HART.
Installation and Common Applications
Oval gear flow meters do not require long straight pipe runs. Install a strainer upstream if the liquid has particles. For high flow start, install an air eliminator before the meter. Mounting can be horizontal or vertical but avoid air entrainment.
We sell these meters into Southeast Asia, Oceania, Latin America, Africa, and the Middle East. Typical applications include diesel fuel consumption on ships, lube oil blending, molasses batching in food plants, and chemical injection skids. Last year a customer in Australia asked us for a DN15 meter to measure diesel on mining trucks.
FAQ
What liquids can an oval gear flow meter measure? The meter works with clean liquids from 0.5 cP to over 100,000 cP. Good examples are diesel, biodiesel, fuel oil, lube oil, resin, molasses, and some solvents. Do not use it for water with sand or slurries.
What accuracy can I expect? Standard accuracy is 0.5 percent of reading above 10 percent of full scale. Optional 0.2 percent is available for custody transfer or batch dosing. Repeatability is better than 0.05 percent.
Does the meter need straight pipe runs? No. Positive displacement meters have fixed pockets. Flow profile does not affect the volume measurement. That design saves space on skids and ships.
What output signals are available? Pulse, 4-20 mA HART, and RS485 Modbus are common. You can add a local display and PT100 for temperature compensation. Tell us your control system requirements and we will match the output.
How do I get a price? Send us your flow range, pressure in bar, temperature in degrees Celsius, pipe size in DN, and liquid viscosity in cP. Our team will reply with a quote within 24 hours. Tel: +86-135-1213-1526. Whatsapp: 86-135-12131526. WeChat: +86 13512131526.
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