This British Standard identifies factors, including installation effects, pipe work and fluid effects, operational effects and supplier specific effects, which are likely to affect the performance of clamp-on (externally mounted) ultrasonic flow-meters This includes hybrid spool type clamp-on meters where the clamp-on transducers are permanently mounted to a spool piece of precisely known physical dimensions. In doing so it also identifies best operational practice for such meters and provides estimates of the overall uncertainty that can be achieved when employing best practice.

This standard provides a description of the non-invasive clamp-on meter, typical application areas, the measures which should be used in assessing the likely performance in terms of error, repeatability and reproducibility when used under ideal flow, pipe, fluid and operational conditions based upon available data.

There are currently three commonly used non-invasive ultrasonic flow measurement technologies. These are the transit time ultrasonic flow-meter (TTUF), Doppler ultrasonic flow-meter (DUF) and the cross-correlation ultrasonic flow-meter (CCUF). However, technological innovation has seen variants of these techniques developed to improve the operation of the meters. The scope of this British Standard is restricted to the use of base technology employed in the meters so as not to preclude further developments. Each technique has its advantages and disadvantages depending upon the application. In order to provide the reader with as much information as possible the different ultrasonic technologies hybrids and their applications are discussed in Annex B to provide a comparative overview of the additional capabilities they offer.