Vortex flow meters measure volumetric flow rate within a pipeline. They're relatively inexpensive and require minimal maintenance since they have no moving parts. As a result, they're useful in many industrial, production, and commercial capacities.

However, there are nuances to their function and some limitations to what they can do. As such, it's important to understand how they work as well as vortex flow meter pros and cons in different capacities.

ifm specializes in vortex flow meters for water-based media. This general article provides a comprehensive guide to a wider variety vortex flow meter functions. It also touches on the  various types of vortex flowmeters and their applications in various industries.

Founded in 1985, ifm efector is an industry-leading provider of sensor and control technologies in the U.S. A subsidiary of the worldwide ifm electronic gmbh, we support over 23,000 U.S. clients across automotive, material handling, food processing, and many other industries, generating upwards of $260 million yearly. ifm USA production exceeds 800,000 temperature sensors and connectors for the U.S. and international markets.

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What is the purpose of a vortex flow meter?

A vortex flow meter uses physics to measure the volumetric flow rate of fluid, gas, or steam within a pipeline. They exhibit high accuracy, reliability, and durability along with low maintenance costs, pressure loss, and installation cost.

They work well with clean fluids with low viscosity, but reveal limitations when there's debris within the flow. 

Why use a vortex flow meter?

A vortex meter is one of the possible options used to measure flow rate. It offers relatively high accuracy and low pressure loss. And, it's one of the less expensive options for flow rate measurement.

Common applications of vortex flow meters

Flow meters are used in a wide variety of applications and industries. These include:

Industrial process control: Regulating liquid and gas flow in chemical manufacturing, petrochemical processing, pharmaceutical production, and other applications.

Steam measurement: Measuring the flow of steam in power plants and refineries to support energy management and efficiency.

Oil and gas industries: Measuring flow range of natural gas or oil for custody transfer, allocation measurement. They also regulate flow through distribution and transmission pipelines.

Wastewater management: Measuring the flow of water and other fluid for accurate billing and efficient water resource management.

Food and beverage: Regulating the flow of water, dairy products, beverages, sauces, and more during production processes.

How does a vortex flow meter work?

The vortex flow meter operating principle is the Von Kármán effect. When a fluid flows around an obstacle, it creates a series of alternating vortices, or swirling eddies. The phenomenon is also called the Von Kármán vortex street.

The meter uses this principle to predict the pattern of these vortices using the the Von Kármán. From there, it can calculate the flow rate from the vortex frequency.

The output signal of the meter is a low voltage signal proportional to the vortex frequency. It then converts to volumetric flow rate. That's the volume of fluid that flows through the system over time.

This method can also calculate the mass flow rate if the density of the fluid is a known constant. The vortex frequency across the meter can be measured by a variety of sensors, which will be discussed below.

Vortex flow meter shedder bar

A shedder bar, also known as a bluff body, is the obstruction placed within the flow to produce the vortices in the meter. Various shedder bar shapes has advantages and disadvantages.

More aerodynamic shapes like cylinders or ovals create less of a blockage, limiting the pressure drop within the meter. However, sharp corners on the sides of a bluff body generate more pronounced vortices within the meter. Diamond or arrow shaped shedder bars provide low pressure loss and high vortex production.

A vortex shedding flow meter is unidirectional. The bluff body must be upstream of the sensor to generate the vortices that will be measured. So, the meter is installed with the flow of the process fluid in mind.

Vortex flow meter accuracy

Typical accuracy of a vortex meter is provided by the manufacturer. A typical uncertainty range for vortex meters is within 2% of the measured value. A meter's true accuracy depends on external factors such as vibrations, process media, installation methods, etc.

You can determine accuracy during calibration. Introduce multiple flow rates into the system and measure those against the installed meter and a reference meter. Then, plot those to have a graph to observe the operational accuracy.

Vortex flow meter repeatability

Repeatability is another measurement of error. The repeatability of a flow meter is the meter’s ability to produce the same measurement reading given the same operating conditions. Repeatability for vortex flow meters is usually within 0.5%.

Calibration addressed a meter that is repeatable but not accurate. But, calibration won't fix a meter that is not highly repeatable.

Vortex flow meter rangeability

The rangeability of a flow meter is the range of flow rate measurements that the meter can accurately measure. Manufacturers provide this as the "turndown ratio."

Typical ratios for vortex meters are 20:1 for gasses and 10:1 for fluids. This ratio is the difference between the maximum flow rate and minimum flow rate a meter can measure.

This is a particularly important metric to consider if your process fluid is more viscous.

Common vortex flow meters sensor types

There are many types of vortex flow meters. Below, we will discuss some of the common options.

Piezoelectric sensor

Piezoelectric materials naturally produce a small electrical charge when they experience mechanical pressure. These materials are often used in sensors that measure a measurable mechanical stress. If the vortices created within the meter are strong enough, they produce a mechanical stress that the sensor can measure. The piezo element used in sensors is usually a ceramic component.

Capacitance sensor

This sensor uses two probes on opposite walls of the pipe. They calculate flow rate based on the positive and negative pressure the vortices generate across the probes.

Ultrasonic sensor

This type of sensor emits a signal from a transducer in one wall of the pipe that bounces across the pipe and is measured by a second transducer. The number of vortices will slow the signal and that time variation can be measured to calculate the flow.

Integrated temperature sensor

In addition to measuring the flow rate, some flow meters can also provide temperature readings. These sensors are usually built into the shedder bar to avoid any disruption to the vortices.

Choosing the right flow meter

Finding the right kind of flow meter for your application or industry depends on many factors. These include pipe diameters, line size, flow velocity, various temperatures and pressures. ifm's line of vortex flow meters suit any industrial or commercial application.

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