How to Choose the Right Oval Gear Flow Meter: A Simple Guide

For your operations to be accurate, efficient, and safe, selecting the appropriate flow meter is essential. Because of their great accuracy and dependability, oval gear flow meters are a popular option for many industries, particularly when measuring viscous fluids like oils, fuels, and chemicals.

As a type of positive displacement (PD) meter, they work by trapping a precise amount of liquid between two rotating oval-shaped gears and counting each parcel as it passes through. This direct volume measurement makes them incredibly accurate and less affected by changes in fluid properties. However, with so many options available, selecting the perfect one can seem complex. This straightforward guide breaks down the selection process into four simple steps to help you choose the right oval gear flow meter for your specific needs.

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Step 1: Understand Your Fluid

The first and most important step is to know the properties of the liquid you need to measure. Oval gear meters are designed for clean liquids, as solids can jam the gears and cause damage. Always plan to install a strainer or filter upstream of the meter to protect it. Three key fluid properties will guide your choice:

1. Viscosity (How thick is your liquid?)

Viscosity is a fluid's resistance to flow. Oval gear meters excel at handling a wide range of viscosities, but it's a critical factor in your selection. Low Viscosity (less than 3 cP - e.g., water, solvents): For thin, water-like liquids, some fluid can "slip" between the gears and the chamber wall, which can affect accuracy at very low flow rates. To get the best results, you may need to operate at a slightly higher flow rate to maintain the meter's stated precision. Medium Viscosity (3 to 1,000 cP - e.g., diesel fuel, lubricating oils): This is the ideal range for oval gear meters. They provide excellent accuracy with these fluids because there is minimal slippage. High Viscosity (above 1,000 cP - e.g., honey, grease, thick resins): Very thick fluids create more resistance, leading to a higher pressure drop across the meter. For these applications, look for meters with special "high viscosity" rotors. These are designed to reduce the pressure drop by up to 50% without sacrificing accuracy.

2. Chemical Compatibility

The flow sensor's materials must be able to withstand the liquid without corroding or degrading. This applies to every part that touches the fluid, known as "wetted parts." Body Material: Cast iron or cast steel is a common and cost-effective choice for fuels, oils, and greases. For chemicals, solvents, or applications in the food and beverage industry, Stainless Steel (316 or 304) is typically required. Rotor (Gear) Material: Rotors are often made from materials like cast iron, aluminum, or stainless steel. Cast iron or aluminum rotors are generally used for measuring non-corrosive liquids, such as fuel oil, heavy oil, and diesel .Stainless steel offer superior resistance for more aggressive chemicals or food industry, such as edible oil, emulsion, and molasses, milk and so on.

Below table list detailed material for oval gear flow meter

Shell and cover	cover plate	oval gear	shaft	Sheath of shaft
LC-A	Cast steel	Cast iron		Stainless steel	Bronze or rolling bearing
LC-E	Cast steel	Cast iron, Stainless steel
LC-B.C	Stainless steel	Stainless steel	Stainless steel		Graphite

LC-A:Cast-iron Oval Gear Flow meter, applied widely for high viscosity fluids or other medium which is not corrosive to cast iron material; Cast iron oval gear flow meter is suitable for liquid flow measurement of naphtha, kerosene, diesel, heavy oil, lubricating oil, paraffin, asphalt, fuel oil, hydraulic oil
LC-E:Cast-steel Oval Gear Flow meter, applied in the low-corrosive fluids with high pressure. Cast steel material oval gear flow meter is suitable for crude oil, aniline, kerosene, crude oil, fuel oil, diesel, lubricating oil, hydraulic oil, asphalt flow measurement
LC-B, C:Stainless steel Oval Gear meter, applied to strong corrosive fluids such as acid, alkali, salty or organic chemicals. Stainless steel oval gear flow meter is suitable for water, ammonia, caustic soda, acetic acid, acrylic acid, ethanol, sulfuric acid, phosphoric acid, ammonium nitrate, fruit juice,vegetable oil, peanut oil, olive oil, edible oil, milk beer, butadiene, toluene, xylene, LPG flow measurement.

3. Temperature and Pressure

Ensure the meter you choose is rated to handle your system's normal operating temperature and pressure, as well as any potential maximums. Normal operation temperature for LC series oval gear flow meter is -20 ~+60°C,we max make 200 °high temperature oval gear flow meter LC series oval gear flow meter has limit pressure rating;

below we list the normal and max pressure we can produce for oval gear flow meter

	Normal Pressure	Max Pressure
LC-A	16 bar	16 bar
LC-E,B,C	16 bar	Max 63 bar for size below 4” Max 25 bar for 6” and 8”

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Step 2: Define Your System's Requirements

Next, look at the physical and operational needs of your system.

1. Flow Rate (Minimum, Normal, and Maximum)

This is the primary factor that determines the size of the meter. You need to know the full range of flow your system will experience. Below table we list LC-series oval gear flow meter flow range for different viscosity liquid. A helpful industry rule of thumb is to select a meter size where your normal operating flow rate is around 60% of the meter's maximum capacity. This practice ensures the meter operates in its most accurate range, reduces wear, and extends its service life. For example, if your normal flow is 25 GPM, a meter with a maximum capacity of around 40 GPM would be a good fit.

2. Pipe Size and Connection Type

The flow sensor must physically fit into your existing pipe work. Oval gear meters are available with various connection types, including: Flanged (ANSI or DIN or JIS or table E flange) Sanitary (Tri-Clover) for hygiene-critical applications. One of the biggest advantages of oval gear meters is that they do not require straight pipe runs before or after the meter, unlike many other technologies,such as vortex flow meter or turbine flow meters. This gives you great flexibility to install them in tight spaces, right after a pump or elbow, without affecting accuracy.

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Step 3: Choose Your Output and Display

How do you need to access the flow data?

There are several options to suit different needs.

a. Mechanical Display: This is a simple, non-powered counter on the meter itself. It's a robust and reliable option for local readings where you don't need to connect to a control system. A s above picture a type flow meter shows.

b. Mechanical Display & resettable total: A mechanical display offers a simple, power-free readout directly on the meter. It includes a resettable batch totalizer that can be manually turned back to zero for individual measurements.   As above picture b type flow meter shows.

c. Pulse Output or 4-20mA analog output: This type has a mechanical display, also generates an electronic pulse signal or 4-20mA that can be sent to a PLC, batch controller, or remote digital display. This is ideal for automated systems.   As above picture c type flow meter shows.

d. Integral Digital Display: A battery-powered or loop-powered electronic display mounted directly on the meter. It can show the flow rate and total volume, offering a modern alternative to a mechanical register.   For loop powered electronic display, it offer 4-20mA,pulse, RS485 or Hart output or communications. As above picture d shows.

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Step 4: Consider Special Certifications

Finally, determine if your application requires any special approvals for safety or legal compliance.

1. Heating Jackets flow meter

For liquids that are easy solidifying or extremely viscous at ambient temperatures, such as asphalt, bitumen, or heavy resins, a standard meter is not sufficient.In these cases, you need a meter with a heating jacket. This is an external casing around the meter body where a heating medium like steam or hot oil can be circulated.The jacket maintains the fluid's temperature, keeping it liquid and preventing it from solidifying inside the meter, which is essential for accurate measurement. Want to know more about jacket oval gear flow meter , click here [ Oval gear flow meter with external heat jacket ]

2. High-Temperature flow meter

For processes involving fluids consistently above 60°C, the high temperature can potentially damage the meter's electronic components (such as the transmitter and sensor) and shorten their service life. In that case, a flow sensor equipped with a cooling fin or heat sink attachment is recommended. These fins increase the surface area of the meter body, effectively dissipating heat into the ambient air and lowering the internal temperature to a safe operating range for the electronics. This design is crucial for reliable operation in applications like high-temperature oils, bitumen or other heated process liquids

3. Sanitary flow meter

For food, beverage, or pharmaceutical production, the meter must meet strict hygienic design standards to ensure it can be thoroughly cleaned and sanitized. For more santiary oval gear flow meter ,click here: [ Sanitary Oval gear flow meter

4. Sensor Size and Pipe Adaptation (Reducers/Expanders):

When selecting a meter, the oval gear flow sensor's nominal diameter is chosen based on your flow rate range rather than the pipe size alone. The ideal scenario is for the sensor's flange rating and size to match your existing pipeline exactly, as this minimizes installation complexity and cost.

However, if the optimal flow rate requires a sensor size different from your pipe size, adaptation is possible using reducing flanges (to install a smaller meter into a larger pipe) or expanding flanges (to install a larger meter into a smaller pipe).

Important Product Limitation:

The LC-A type (likely a specific model of flowmeter) cannot be fitted with reducing or expanding flanges. Its installation requires the pipeline size to match its flange size exactly.

This adaptation capability is currently available only on certain robust meter constructions, such as our LC-E series cast steel and LC-B & C series stainless steel elliptical gear meters. Please confirm model compatibility during the selection process.

5. Hazardous Areas:

If you are measuring flammable liquids or the meter is in an environment with explosive gases or dust, it must be certified for safety.

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Your Selection Checklist

By answering these simple questions, you can confidently choose the right oval gear meter:

Fluid: What is my liquid, and what is its viscosity, temperature, and pressure?
Compatibility: What materials (body, rotors, seals) are compatible with my fluid?
Cleanliness: Is my fluid clean? (If not, I need a filter).
Flow Rate: What are my minimum, normal, and maximum flow rates?
Installation: What is my pipe size and preferred connection type?
Output: How do I need to read the data (mechanical, digital display, pulse)?
Certifications: Do I need approvals for hazardous areas, custody transfer, or sanitary use?

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Conclusion

Choosing the right oval gear flow meter doesn't have to be complicated. By systematically considering your fluid, system requirements, data needs, and any special certifications, you can select a meter that will provide accurate, reliable measurements for years to come. This careful selection process is a small investment that pays off with improved process control, reduced waste, and a lower total cost of ownership.