This document API MPMSCH 5.8:2025 outlines the use, performance, and functioning of ultrasonic flow meters (UFMs) specifically within liquid hydrocarbon applications. It aims to detail the methods necessary to meet custody transfer measurement standards, including accuracy, when utilizing an ultrasonic meter for measuring liquid hydrocarbons. Ultrasonic flow meters operate by inferring flow rates through the measurement of transit times of high-frequency sound waves. Multipath ultrasonic meters are equipped with at least two independent pairs of measuring transducers, enabling multiple acoustic paths.

The primary focus of this standard is the dynamic measurement of single-phase liquid hydrocarbons. Although it is tailored for custody transfer measurements, it also accommodates other applications, such as allocation measurements, check meter measurements, and leak detection assessments. This document specifically addresses spool-type, multipath ultrasonic flow meters that feature permanently mounted acoustic transducer assemblies.

While it acknowledges that other types of meters are used for liquid hydrocarbon measurement, this publication does not promote or suggest a preference for ultrasonic meters nor does it aim to limit the advancement of alternative meter technologies. Users of different meter types may still find relevant sections of this document beneficial.