Flow Measurement in Liquid Lines Affected by Gas Content Issues

In many industrial applications, entrained or trapped gas content in pipelines carrying liquid flows creates significant challenges from a measurement technology perspective. For effective process management to be achieved, measurement data from the field must be stable and reliable. Unstable gas content in liquid flow lines creates major problems for many measurement methods, substantially preventing accurate and precise measurement. Such and similar issues can have significant and adverse consequences on production efficiency and total cost. As in many sectors, the oil and gas industry faces significant challenges from continuously falling energy prices. However, companies operating in the sector are expected to continuously increase their efficiency while meeting their obligations to maintain current standards.

Many forward-thinking companies;

To overcome these challenges and remain competitive under difficult conditions, they are turning to solutions brought by continuously evolving technologies. At this point, one of the proven ways to increase process efficiency is to perform flow measurements—which are extremely important—with high precision and accuracy. As in other industrial fields, entrained gas in liquid lines (two-phase flow) has very significant effects on measurement accuracy and performance in oil and gas applications. Although many measures have been developed to prevent entrained gas content or at least to discharge it from the line, to date it cannot be said that definitive and significant results have been achieved in this matter. Under two-phase flow conditions, some measurement technologies cannot measure at all, while some measurement technologies detect gas as liquid and perform measurements together with the liquid. In such cases, flow meters; perform incorrect measurements proportional to the gas volume entrained in the liquid and may even completely cease measurements after the gas volume reaches a certain level. This entrained gas content in the mentioned liquid medium creates a unique and significant challenge even for the Coriolis mass flow meter, which operates by calculating fluid density through the oscillation frequency of the measurement tubes.

In measurements, the Coriolis flow meter tubes';

the lower the oscillation frequency, the greater the density value will be proportionally. On the other hand, the gas and liquid contents of the two-phase fluid move at different speeds along the flow tubes oscillating at a specific frequency. At this point, entrained gas content can cause rapid and unstable changes in the flow regime and the measurement tube oscillation frequencies. These rapid frequency changes can lead to signal loss in the sensors located on the measurement tubes of Coriolis mass flow meters; however, such a condition will cause the flow meters to provide extremely irregular and non-repeatable measurements. Furthermore, frequency differences between sensors that may occasionally occur can even cause the flow meter to return to zero mode and prevent the flow from being measured. Facing such an important problem, many Coriolis mass flow meter manufacturers made efforts to develop different technologies to enable flow meters to operate in two-phase flows, but approached the problem from very different angles. In 2012, Krohne developed a definitive and permanent solution to measurement problems in two-phase flows with EGM (Entrained Gas Management) technology, developed as a standard feature for MFC400 transmitters, the electronic unit of its OPTIMASS model Coriolis mass flow meters. Krohne EGM technology, using high-speed digital signal processing and software-based algorithms, performs constant and precise corrections at the measurement tube driver level based on real-time frequency information obtained from the feedback of sensors and drivers. These corrections enable the Coriolis mass flow meter to perform continuous and repeatable mass flow and density measurements across a wide variety of gas entrainment and complex flow conditions. Thanks to this technology developed by Krohne, Krohne Coriolis mass flow meters; can perform trouble-free, stable, and repeatable measurement even in continuously changing flow regimes of liquid lines with entrained or trapped gas content. This measurement capability has demonstrated the uniqueness of EGM technology through its measurements even under the most difficult conditions since the day it was first applied in the field.