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GPI Oval Gear Flow Meter Working Theory: High-Viscosity Liquid Monitoring Without Pressure Losses
Quick Answer: A GPI oval gear flow meter is a positive displacement meter. Two oval gears rotate as liquid moves through the metering chamber. Each rotation traps a fixed volume, so the meter reads high-viscosity liquids with minimal pressure loss and no straight pipe runs.
Silver Automation Instruments is an industrial flow meter manufacturer and supplier. We supply oval gear flow meters for high-viscosity liquid monitoring in fuel oil, resins, molasses, paint, adhesives, and other fluids. This page explains the GPI oval gear flow meter working theory, the pressure loss question, and the sizing data you need before requesting a quote.
How a GPI Oval Gear Flow Meter Works
Inside the meter body, two oval gears sit at 90 degrees to each other. Liquid enters the chamber and pushes the gears around. The gears seal off a fixed pocket of liquid between the gear tooth and the chamber wall. Each full rotation passes four of these pockets from inlet to outlet. A sensor counts the rotations. The meter output is directly proportional to volume.
No flow conditioning is needed. The oval gear design does not rely on flow profile, Reynolds number, or straight inlet runs. A DN15 meter can sit right after a pump or a filter and still hold its accuracy.
Why High-Viscosity Liquids Need Positive Displacement
Most flow meters lose accuracy when viscosity rises above 100 cP. Orifice plates, turbines, and vortex meters depend on flow velocity. A GPI oval gear meter reads volume directly from gear displacement. Viscosity changes from 50 cP to 50,000 cP have only a small effect on the reading.
Common liquids on our customer sites include heavy fuel oil at 380 cSt, glucose syrup at 80,000 cP, and offset printing ink at 20,000 cP. In practice, engineers choose an oval gear meter when the fluid does not flow like water.
Pressure Loss Facts for GPI Oval Gear Meters
The term without pressure losses can be misleading. The meter adds a small pressure drop because the gears need torque to rotate. But this drop is low compared to orifice plates or turbine meters. A typical DN25 oval gear meter shows a pressure drop of 0.1 to 0.5 bar depending on viscosity and flow rate. For high-viscosity liquids, the pressure drop increases slightly because the fluid resists shear.
What the user gains is no added pressure loss from flow straighteners or long straight pipe runs. That is the practical difference. We have seen a food plant in Thailand install a DN20 oval gear meter for palm oil after a 90 degree elbow with no accuracy problem.
Recommended Silver Instruments Oval Gear Flow Meters
Silver Automation Instruments offers the SIOG series oval gear flow meter in DN10, DN15, DN20, DN25, DN40, DN50, and DN80 sizes. The standard body material is 316L stainless steel or aluminum. Gear
Application Example from Southeast Asia
A paint manufacturer in Vietnam needed to measure resin with viscosity of 45,000 cP at 40 degrees Celsius. The pipe size was DN25 and the normal flow range was 30 to 180 L/h. We supplied a DN25 oval gear meter with 316L body, PTFE gears, and a 4-20 mA HART output. The meter has run for 14 months without recalibration. The pressure drop across the meter is stable at 0.2 bar.
This kind of case is common for us. A customer in Indonesia uses the same meter for molasses batching. A customer in Chile uses a DN15 version for glycerin filling.
Ordering Data for a Quote
Send us your pressure in bar, temperature in degrees Celsius, pipe size in DN, and flow range in L/h or kg/h. Also tell us the fluid name and viscosity in cP. This is not a generic request for information. These four values let us check meter size, gear material, bearing type, and output signal in one pass.
Contact Silver Automation Instruments by tel at +86-25-68650347, by WhatsApp at +86-25-52155837, or by WeChat at +86 15365082610. You can also visit our site flow-meter.com.au for the full oval gear flow meter product page.
FAQ
What is the working principle of a GPI oval gear flow meter?
Two oval gears rotate inside a closed chamber. Every rotation moves a fixed volume of liquid from the inlet to the outlet. The meter counts rotations and converts them to flow volume.
Can a GPI oval gear flow meter measure high-viscosity liquids?
Yes. The design is positive displacement. It works with heavy fuel oil, paint, resin, molasses, glycerin, and adhesives. Viscosity can be higher than 100,000 cP if the gears and bearings are selected correctly.
Does an oval gear flow meter cause pressure loss?
It adds a small pressure drop. The pressure drop is usually lower than a flow conditioner or an orifice plate. A DN25 meter often drops 0.1 to 0.5 bar depending on viscosity and flow rate.
What size should we choose for a high-viscosity liquid?
Do not size by pipe diameter alone. Use the actual flow rate and viscosity. A DN15 meter can handle 0.5 to 120 L/h in many viscous fluids. Send us your flow range and we will confirm the right size.
What output options are available for the Silver Instruments oval gear flow meter?
Pulse, 4-20 mA, and 4-20 mA HART are the standard outputs. A PT100 temperature probe can be added for hot liquid service. Digital displays and batch controllers are available as separate accessories.