How to Use Ultrasonic Flow Meters
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Ultrasonic Flow Meters How to Use Ultrasonic Flow Meters Ultrasonic flow meters are commonly applied to measure the velocity of liquids that allow ultrasonic waves to pass, such as water, molten sulfur, cryogenic liquids, and chemicals. Transit time designs are also available to measure gas and vapor flow. Be careful because fluids that do not pass ultrasonic energy, such as many types of slurry, limit the penetration of ultrasonic waves into the fluid. In Doppler ultrasonic flow meters, opaque fluids can limit ultrasonic wave penetration to near the pipe wall, which can degrade accuracy and/or cause the flow meter to fail to measure. Transit time ultrasonic flow meters can fail to operate when an opaque fluid weakens the ultrasonic wave to such an extent that the wave does not reach the receiver. Ultrasonic flow meters do not obstruct flow so they can be applied to sanitary, corrosive and abrasive liquids. Some ultrasonic flow meters use clamp-on transducers that can be mounted external to the pipe and do not have any wetted parts. Temporary flow measurements can be made using portable ultrasonic flow meters with clamp-on transducers. Clamp-on transducers are especially useful when piping cannot be disturbed, such as in power and nuclear industry applications. In addition, clamp-on transducers can be used to measure flow without regard to materials of construction, corrosion, and abrasion issues. However attractive, the use of clamp-on transducers introduces additional ultrasonic interfaces that can affect the reliability and performance of these flow meters. In particular, if not properly applied and maintained, attenuation of the ultrasonic signal can occur at the interfaces between the clamp-on transducers and the outside pipe walls, and between the inside pipe walls and the fluid. Ultrasonic flow meters are available in sizes to 72 inches and larger. |