18 ULTRASONIC PATHS FOR LIQUID FLOW MEASUREMENT

摘要

Turbine and Positive Displacement meters have been successfully used in the oil industry for many years. Both technologies provide accurate flow measurement for custody transfer applications in compliance with international standards and recommendations such as OIML and API.rnOver the last ten years, significant improvements in electronics and acoustics gave access to high accuracy liquid flow measurements based on ultrasonic technology.rnThe ultrasonic technology has been first efficiently used in the natural gas industry for several years. The development of the technology for the gas custody transfer applications has quickly shown that a multi-path geometry was the only way to cover a large range of flow velocity profiles.rnSeveral suppliers have developed ultrasonic flowmeters for liquid applications based on the multipath technology. During the last years, acknowledging the actual potential of the ultrasonic technology, API decided to create a working group to release a new API draft standard related to the ultrasonic technology for liquid flow measurement. Based on field test results performed under the API responsibility on crude oil and refined products, a draft standard has been issued end of the year 2002.rnToday everyone agrees that ultrasonic technology creates values for end-users by simplifying metering installations and reducing their ownership cost. Indeed, the very low pressure drop through the metering system decreases the power consumption drastically and the lack of moving parts reduces the maintenance cost of the flowmeter.rnAmong all the advantages of the ultrasonic technology, the main end-users concern remains the flow measurement accuracy. To cover all applications and installation conditions, an ultrasonic flowmeter must be able to perform accurate measurement with uncontrolled flow conditions such as swirls, asymmetric, laminar, and turbulent flows.