Using ultrasound, an ultrasonic flow meter detects the flow of a fluid’s velocity. A wide variety of fluid-related applications may benefit from its utilization. When it comes to monitoring the flow of water and other liquids, ultrasonic flow meters are ideal. Clamp-on ultrasonic flow meter save time by removing the need for pipe cutting or process downtime, and they are not affected by external noise.
Ultrasonic flow meters are explained in the following paragraphs
Sound waves at a frequency beyond the range of human hearing are used in ultrasonic flow meters (typically 0.5, 1, or 4 MHz). With wetted (insertion) transducers or external (clamp-on) transducers, this ultrasonic signal may be delivered into a flowing liquid stream. Alternatively, this ultrasound signal can be transmitted via the pipe wall. When installing and maintaining a clamp on ultrasonic flow meter, it is feasible to measure the volumetric flow rate of a fluid in a pipeline without having to enter the pipe.
Ultrasonic flow meters typically employ two ultrasonic transducers, one for transmitting and one for receiving, to measure ultrasonic flow. As a way to accurately measure ultrasonic flow, an ultrasound burst must be sent and received between the two transducers and measured for how long it takes to travel in both directions. The difference in transit time (measured) is directly related to the velocity of the liquid in the pipe.
Ultrasonic waves are generated by equipment known as ultrasonic transducers
Clamp-on transducers are often used in the V (2-pass) mounting approach shown in the image below. In this particular application, ultrasound is sent from the first transducer and received by the second transducer after travelling through the pipe wall, the liquid, and reflecting off the pipe’s back wall.
Using the second transducer instead of the first, the method is repeated in reverse. The Time refers to the time difference between the periods of flying up and down. When there is no movement in the pipe, the elapsed time is equal to one.
A transducer is seen in this diagram
First, the raw time must be translated into a velocity that is specific to the pipe’s liquid. Knowing the speed at which sound travels through the pipe and the liquid allows you to determine the angle at which ultrasound travels. Trigonometry is used to convert an ultrasonic path into a straight line in a pipe by using this angle. This will decide the flow rate of the water in the pipe.
To calculate the flow rate, just multiply the velocity by the pipe’s cross-sectional area, as with any other velocity-based flow meter.
The benefits of employing ultrasonic technology are:
One of the most important advantages of any “clamp-on” transit time flow meter is the simplicity with which it may be fitted. It is still necessary to build sections of straight pipe upstream from the measurement location, but the installation technique does not need shutting down the system, making maintenance and upkeep of transit-time meters much more attractive.
There are no blades to wear out or bearings to repair in a turbine meter, unlike a magnetic flow meter’s electrodes, which foul with time in turbine meters.
