A. Rieder, H. Zhu, P. Ceglia, H.-T. Ngo
Laboratory and Field Validation of a New Coriolis Metering Concept for Better Measurement Uncertainty, Reliability and Process Insight
Coriolis mass flowmeters are widely accepted in various industries for the great performance of density and mass flow rate measurements. Not only do they play a critical role in O&G custody transfer applications, but also an increasingly important role in addressing the new challenges and applications related to the energy transition where the highest accuracy and reliability is also required. Analogous to multi-beam Ultrasonic flowmeters, a new measuring concept based on Coriolis principle has been developed with a metering system that consists of two individual Coriolis meters arranged in parallel for the incoming flow in the system. There are numerous advantages of this arrangement, among which reducing measurement uncertainty, increasing reliability and gaining greater process insight are the most significant ones. The statistic theory has shown that for a total measurement equally divided by two sub-measurements of two independent measuring devices, the measurement uncertainty caused by random errors is reduced by a factor of square root of 2 for the combined total measurement. This rule applies to the Zero Point and repeatability performance of the metering system. Taking the advantage of independently measuring the same or similar fluid parameters twice, the measurement reliability is enhanced by cross-checking the two sets of measured parameters. For certain special cases, such as transient disturbance of entrained gas that often exists under real process conditions, the corresponding negative impact can even be mitigated or eliminated by utilizing the undisturbed measured parameter set from the two. The spacial arrangement of the two Coriolis meters makes it useful to monitor the measured fluid parameters such as two sets of densities, flows and temperatures for obtaining the knowledge of the special distribution of fluid parameters, gaining greater process insight.A critical step has been the validation of the theoretical advantages in third-party laboratories and in the field. A test was done for the Zero Point stability of the metering system under various temperatures, pressures and viscosities at NEL using the EPAT facility. The measurement results suggested that the Zero Point deviations of the two Coriolis meters followed a random probability and tended to cancel each other to certain degree, leading to a reduced Zero Point deviation for the complete metering system. Repeatability and reproducibility tests were done both at NEL EPAT and at Euroloop oil rigs with provers, showing good and consistent results. Recognizing most hydrocarbon markets trade on a volumetric basis rather than mass, the advantages the design brings towards density measurement are discussed and measurement data is presented across varying fluid densities and viscosities. In step with the growing importance of gaseous fluids to the evolving energy markets, the influence the novel design has on performance in gas applications is described and measurement data in gases is also presented. Furthermore, an interesting phenomenon has been captured during the flow stabilization phase before proving at Euroloop that transient disturbance of gas bubbles could be present, and very often disturbed only one meter at the same time, which enables the possibility to remediate the effect of transient disturbances. The same phenomenon took place in field tests of the metering system, indicating the high probability of the occurrence. In this paper, the laboratories data from the NEL EPAT rig, Euroloop rig, pigsar rig, and H&D Fitzgerald as well as the data from field applications are presented and analysed to validate the theoretical analysis.
