Ultrasonic Flow Measurement: Basics and Components

Understanding Ultrasonic Flow meter Techniques and Key Elements

Ultrasonic Flow Meter is one of the flow measurement devices used for fluids’ velocity in industrial and domestic applications. In previous article, we discussed the devices used to measure the flow, quantity, and velocity of liquid, gaseous and bulk materials and their types. general.

We mentioned that there are three categories of flow meters types used based on the material that will be measured such water, natural gas, and sand. We also talked about the advantages of these devices and provided examples of each type.

In this article, we will cover one of the important and widely used types for measuring and calculating flow rate by Ultrasonic Flow Meters. It relies uses the ultrasonic waves to measure flow inside pipes such as water flow in water treatment and desalination plants.

Ultrasonic flow meter device

The importance of flow measurement using ultrasonic waves lies in the advantages of these devices (highlighted in this article) such as accuracy, reliability, and ease of installation and use. They do not require regular maintenance beyond routine inspection. Moreover, these devices are environmentally friendly.

When Ultrasonic Flow Meters are integrated with Artificial Intelligence (AI) and Internet of Things (IoT) technologies, they offer significant advantages in monitoring, follow-up, and conducting analytical assessments of measured values.

Through these integrated systems, it becomes possible to create preventive maintenance plans and periodic strategies for the devices operating in a particular location. This ultimately enhances product quality, increases productivity, and reduces costs.

What Are Ultrasonic Flow Meters?

Ultrasonic Flow Meters are devices used in industrial processes to measure materials’ flow through pipes by calculating the velocity of the fluid. They are type of volumetric flow meter where the measurement units can be gallons, cubic meters, or other units, and time can be measured in minutes, hours, or seconds.

When using them, it is important to select a device that matches the fluid’s physical, electrical, and mechanical specifications. For example, regarding the physical properties, we consider the fluid temperature, flow velocity, pressure difference at the orifice, viscosity, and the pipe size.

All these parameters directly affect the fluid's flow speed. For instance, the pressure difference between the upstream and downstream (when using an orifice) influences the flow rate, and increasing temperature results in increased fluid speed within the pipe.

What are the Advantages of Ultrasonic Flow Meters

• Non-intrusive measurement. These devices do not come into direct contact with the fluid being measured, thus reducing risks of injury.

• External installation. They are mounted on the external surface of the pipes without the need to cut into the pipe or stop the fluid flow.

• No moving parts. Internally, these devices lack moving components like gears, which reduces wear from friction, leading to lower maintenance needs and extending device lifespan.

• High accuracy. They are highly accurate, especially in critical industrial applications.

• No alteration of fluid properties. These meters do not change the physical properties of the passing fluid and do not interfere with its speed or quantity, as there is no interaction with the liquid.

• Ideal for large pipes. They are especially suitable for measuring flow in large-diameter pipes, commonly found in major industries like petroleum refining, cement, or iron.

• Integration with modern technologies. Their integration with smart systems like AI and IoT enhances their functionality.

• Environmentally friendly. They do not cause any fluid leakage or expose the measured liquid to the surrounding environment, making them safe and eco-friendly.

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  Ultrasonic flow meter component

  
  

What is the Principle of Ultrasonic Flow Meters?

Ultrasonic Flow Meters use ultrasonic waves to measure the flow rate of liquids or gases inside pipes by one pair or more ultrasonic transmitters and receivers. The ultrasonic waves are generated and transmitted by transmitters, which are typically ultrasonic wave generators, and received again by the receivers after passing through the fluid flowing in the pipe.

There are two main methods for measuring flow velocity:

1- Transit-Time Method:

This method calculates the time it takes for ultrasonic waves to travel from the transmitters to the receivers in the direction of fluid flow or against it. The time is shorter when the waves move with the flow, and longer when they move against it. By calculating the difference in time between the two directions, the fluid velocity can be determined. The greater the difference between the forward and reverse travel times, the greater the fluid velocity, since the relationship is directly proportional.

2- Doppler Effect Method:

This method is used to measure the change in frequency of ultrasonic waves that are reflected by the surface of particles or bubbles present in the fluid. The wavelength and frequency of the reflected waves vary depending on the velocity of these particles, which allows the flow rate to be determined. This method is commonly used for fluids containing solid particles or gas bubbles that can reflect ultrasonic waves when struck.

Main Components of Ultrasonic Flow Meters

• Power Supply Units. These units supply the device with the necessary electrical power, either from a permanent electrical source or a battery. Some versions are portable, operating on batteries to facilitate temporary inspections.

• Ultrasonic Transducers. These are the devices that generate and transmit ultrasonic waves and also receive them. As mentioned, there may be a pair or more of each type, installed either on the external surface of the pipe or inside it, depending on the type of device used. Some models function as both transmitter and receiver simultaneously, with wave reflections occurring either from the inner pipe surface or from particles within the fluid, which act as reflectors.

• Transit-Time or Frequency Measurement Units. These units are responsible for measuring and calculating the time difference between the waves sent and received in Transit-Time systems, or the frequency difference in Doppler systems. These units are the core components responsible for collecting data from the transducers.

• Electronic Signal Processing Units. These units analyze incoming data from the transducers and apply the necessary flow calculation formulas to determine fluid velocity and flow rate. They also process incoming signals to filter out noise, improving measurement accuracy.

• Calibration and Programming Units. These units are used to set device parameters according to pipe size and fluid type. They are also used to program the devices in case of special working conditions.

• Display and Interface Units. These components display the readings and parameters measured and calculated by the signal processing units, such as flow rate, total volume of fluid, and velocity. The display can be in the form of digital screens, control interfaces, or connected to SCADA systems, Programable Logic ControlPLCs, or IoT systems.

• Mounting Structures and Flow Pipes. These are mechanical structures used to mount the transducers on both sides of the pipe, especially in non-intrusive systems (clamp-on types) or on internally mounted transducers in in-line integrated systems.

Summary.

This article explains how ultrasonic flow meters work using sound waves to measure the flow of liquids or gases in pipes. It covers the two main measurement methods: transit-time and Doppler effect. You'll also learn about the key components involved in these systems, from transducers to signal processors. Ideal for industrial applications, these devices offer accurate, non-intrusive, and eco-friendly flow measurement solutions.