Novel Application of Coriolis Meters in Custody Transfer Applications

Abstract

Abstract This paper describes the novel application of Coriolis Meters in custody transfer applications related to ADNOC Gas Processing sales gas network. Though Ultrasonic meters are the preferred choice for custody transfer applications, Coriolis meters are widely used for similar applications in smaller pipelines due to its accuracy and turndown ratio as well as less Operational Expenditures. Coriolis flow meters operate based on the Coriolis principle invented by Gaspard Gustave de Coriolis over 180 years ago. The Coriolis meter directly measures mass flow. It consists of a tube that oscillates at its resonance frequency. If the tube is empty, it will oscillate uniformly but if it is not empty, twisting of the tube will be observed resulting in phase shift between the two ends of the tube which is directly proportional to the flow. Also, this technology can be utilized to simultaneously measure the density as the oscillation is inversely proportional to the density. Even though turbine and positive displacement meters are suitable for custody transfer applications, Coriolis flow meters are preferred as they do not have moving parts. Coriolis meters provide increased accuracy because of its ability to directly measure mass flow without the requirement for temperature and pressure compensation. It is not affected by the flow profile, thus does not require upstream and downstream straight length requirements. In addition, it is reliable, fast and has diagnostic features as well as dynamic responses which make it fully suitable for custody transfer metering. Although the associated Capital Expenditures are high, for lower line sizes (6" size and less), their Operational Expenditures are relatively low, resulting in lower total cost of ownership. Coriolis flow meters are conventionally used for liquid applications. For gas custody transfer applications, ultrasonic meters are predominantly recommended for larger pipe line sizes. However, for lower line sizes (6" size and less), ADNOC Gas Processing follows AGA (Report No. 11: Measurement of Gas by Coriolis Meter, approved by API for Custody Transfer Applications of Gas) standard to implement the technology in custody transfer metering applications for sales gas, and it has been found to be successful.