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Positive Displacement Flowmeters

About Circular and Oval Gears vs Non-direct Measurements

A circular gear flow meter (also called cylindrical gear) belongs to the family of positive displacement meters just like the oval gear meter.
One of the well-known attributes of a positive displacement meter (also known as a PD meter) is its ability to measure volumetric flow directly as opposed to non-direct methods (inferential) which take a velocity measurement and using mathematical equations calculate volume flow from the velocity. Inferential type meters work very differently but since the velocity is known – it is possible to compute the volumetric flow rate in this way. An example is shown in the video of how a velocity in meters/second (or m/s) can be converted into a volumetric flow in litres per minute for a known pipe size.
The following example shows how a 1 m/s velocity in a pipe with an internal diameter of 1 inch is calculated at 30.39 L/M.
The equation used here is Q = VA where Q is the volumetric flow rate, V = velocity and A = surface area.

Flow Velocity to Volumetric in Pipe – A Website for Engineers and Technicians (processassociates.com)

However, this calculator calculated the volumetric flow rate with assumption that the flow velocity is uniform across all sections of the pipe. In reality, this is not happening because the flow velocities nearer the pipe wall will tend to be less than the velocity in the middle of the pipe.
In order to correct for these errors, a Reynolds Number compensation must be configured.

Why are positive displacement flowmeters considered easy to understand?

If you take a look at the working principle of this Oval Gear meter as an example, you will see that the gears do not turn unless a void (volume) is filled.
Oftentimes, engineers have likened this principle of measurement akin to filling cups to the full. Imagine each void is a cup and the rotation of the internals will not move until one cup is filled. These meters can be installed in a liquid line, measure accurate flow and continue to keep reporting accurate flow.

Where Are Circular Gear Flow Meters Being Used?

Circular gear flow meters are widely utilized across various industries that require accurate and continuous measurement of fluid flow. They are particularly effective in applications involving oil, chemicals, and solvents, where precise flow control is essential. Here are some key industries and applications for circular gear flow meters:

  • Oil and Gas Industry: These flow meters are commonly used for measuring the flow of crude oil, refined petroleum products, and natural gas. Their reliability in handling viscous fluids makes them ideal for various processes in this sector.

  • Chemical Processing: Circular gear flow meters are essential in the chemical industry for monitoring the flow of various chemicals, including acids, bases, and solvents. Their ability to handle a wide range of viscosities ensures accurate measurements in complex chemical processes.

  • Food and Beverage: In the food and beverage industry, circular gear flow meters are used to measure the flow of liquids such as oils, syrups, and juices. Their hygienic design and accuracy are crucial for maintaining product quality and consistency.

  • Pharmaceuticals: These flow meters are vital in pharmaceutical manufacturing, where precise measurements of active ingredients and solvents are necessary for drug formulation and production.

  • Water and Wastewater Treatment: Circular gear flow meters are employed in water treatment plants for monitoring the flow of chemicals used in treatment processes, as well as in the management of wastewater.

  • Pulp and Paper: In the pulp and paper industry, these flow meters help manage the flow of chemicals used in various stages of paper production, ensuring efficiency and quality control.

  • HVAC Systems: Circular gear flow meters are used in heating, ventilation, and air conditioning systems to monitor the flow of water and refrigerants, contributing to system efficiency and performance.

Other Notable Applications of Circular Gear Flow Meters

Circular gear flow meters are versatile tools used in many applications due to their ability to measure a variety of fluids accurately. They handle liquids with high or low pH levels, making them suitable for chemical processing where precise measurement of acidic or alkaline solutions is needed. These flow meters also effectively measure saline solutions, commonly used in medical and pharmaceutical settings, as well as in water treatment. Their robust design allows for the safe measurement of toxic chemicals, reducing risks in hazardous environments.

Low Flow – Yes!

This product (because of its inherent design) is able to accurately pick up low flow rates. Additionally, circular gear flow meters excel at detecting low flow rates, which is especially useful in laboratories or small-scale production where accuracy is crucial. They are also used in fuel measurement applications to monitor the flow of diesel, gasoline, and biodiesel, ensuring accurate dispensing. In the paint and coatings industry, these meters help ensure consistent application and quality control. They are similarly effective in measuring adhesives and sealants for precise application rates in manufacturing. Overall, circular gear flow meters are adaptable for various liquid types, making them essential for accurate measurement and operational efficiency.

Electronics

The rotations are measured by using non-contact methods. A popular design is the Hall Effect (but not limited to) which creates a pulse signal proportional to the flow rate.
One of the advantages of pulse outputs is that it is easy to totalise i.e. to measure total flow in volumes or batches (Batch Flow SG Flow Meters supplies circular gear flow meters manufactured by automated precision machining which improves overall accuracy and repeatability in both low and higher flow scenarios, even at high temperatures.

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