The Speed of Sound in an Ultrasonic Flow Meter

Speed of sound is a term used to describe how quickly sound waves pass through a medium. Ultrasonic flow meters record and analyse the speed of sound to measure the flow of liquids or heat as they travel through open or closed pipes as part of a managed process. There are many benefits to measuring and monitoring flow across a wide variety of industrial processes, including improved efficiency, quick identification of problems in the process and increased accuracy.

The speed at which the sound waves travels will be variable, depending on the medium being measured, as well as the temperature of the medium. It is easier and therefore quicker for sound waves to pass through a solid than a liquid and more difficult through a gas. This is due to how close the molecules within the medium are; in a solid they are tightly packed together, enabling the sound waves to easily pass from one to another, so the sound is transmitted more quickly. Every solid, liquid or gas also has its own speed of sound properties, which are determined by its elasticity and density.

In order to understand normal flow, many ultrasonic flow meters can be pre-programmed with the exact speed of sound for the liquid or gas being monitored. If you are setting up an ultrasonic flow meter for use in your processes, you will find many of the standard speed of sound measurements are programmed into the device. This enables the meter to be tailored to the specific requirements of your particular application. If the medium you are working with is not included as standard, you can find the correct speed of sound (at 25 degrees Celsius) by following this link.

Once your flow meter has been fitted and programmed with the correct speed of sound for your application, it will emit Ultrasonic waves. Having passed through the liquid or gas being monitored, the returning signal is recorded and analysed against the ‘normal’ reading. This data is usually shown on a display screen attached to the flow meter. By knowing what the normal reading should be, it allows for optimum levels to be maintained as well as early detection of any flow issues.

Ultrasonic flow meters can be used in a variety of settings and to meet the needs of many different industries. They can be particularly valuable in accurately monitoring in closed pipe, large scale or difficult to access applications. In all situations, the use of non-invasive ultrasonic sound transmission to detect liquid flow velocity means that monitoring can take place without the need to interrupt the process. As downtime or interruptions can have significant cost implications, flow meters provide a cost effective flow measuring solution. They can be permanent fixtures at crucial parts in the process, or portable flow meters can be moved and used to assess different areas.

Portable meters can cost in the $600 to $900 range for a basic model, like this one on Amazon for $820 TDS-100H-HS+HM Transit-Time Handheld Digital Ultrasonic Flow Meter for DN15-700mm Pipe Size With Bracket Transducers; More elaborate ones can cost in the $15,000 to $20,000 range. Be sure to do your research on just what you need before purchasing.

The value and effectiveness of the flow meter is in part determined by the knowledge and training given to the operator. The operator needs to understand normal readings for the liquid or gas being monitored as well as being able to quickly interpret data that shows changes to the flow. There needs to be clear reporting processes in place, so the operator knows who to inform when issues are detected. By taking action quickly, issues such as leaks or blockages, which would create either lower or higher levels of flow can be rectified before they become a major issue.

If you are installing flow meters for the first time, or hiring flow meters for a specific purpose (such as pre-inspection checks) you may wish to employ the services of an experienced operator. The flow meter manufacturer may offer this service, or will be able to recommend a suitable operator or company. For more information visit Micronics.

Here is an example of a new construction in-line flow meter Sotera FR1118P10 Inline Flowmeter, Digital (Available from Amazon for about $80)

Source: GoArticles by Author Liam Johnson .

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(Image Credit – Micronics )

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