Ultrasonic Clamp on Flowmeter Measurement Issues

3rd February 2020

Understanding installation problems with Ultrasonic Clamp On Flowmeters Part 1 -The User

With the recent growth and reduced costs of transit time ultrasonic clamp on flow meters, many users, experienced and inexperienced have turned to the clamp on market thinking they will get a quick and easy solution for pipe velocity measurements. A recent study highlighted that even the simplest of installations and applications can provide erroneous results. The Young Calibration Fluid Flow Laboratory has conducted over 500 clamp-on flow meter calibrations in the last few years alone, and was enlisted undertake a correlation study, looking at the potential issues when using these meters for basic flow measurements. Initial findings are limited to looking at the user to user variance of the installation, setup and commissioning of several clamp on meters when installed under manufacturers' procedural guidelines. The study was conducted using two transit time type meters on a 100 mm steel pipe under steady state flow conditions using water as the test media. The flowmeters were (1) a low-cost single channel model and (2) a high-performance dual channel meter. The findings highlighted a large sensitivity to user installation on the lower cost model, with a flow rate error variance of 5 to 32% whilst the high-performance dual channel meter recorded error variance of -0.5 to 3%. In the first of our application notes for ultrasonic clamp on meters it is astoundingly clear that the user has an important role in the setup of the clamp on meter, but overridingly the manufacturer meter quality plays a significant part in attaining accurate flow measurement results. In later parts we will be discussing installation effects in more detail, with traverse type setup, coupling pastes, pipe sizes and pipe measurements, particulate/bubbles, pipe condition and how meter diagnostics can help you attain better and reliable results. For more information on flowmeter benchmarking or flow meter calibration, contact Young Calibration.