The application of mass flow meters in oil product measurement

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Background: In industrial production, due to material balance, heat balance, storage and transportation, as well as economic accounting, it is mass rather than volume that needs to be measured. Therefore, in measurements, it is often necessary to multiply the measured volumetric flow rate by the density in order to convert it into a mass flow rate. While measuring the volumetric flow rate, it is necessary to determine the temperature and pressure of the fluid in order to convert the volumetric flow rate into a value under standard conditions, thereby allowing the mass flow rate to be calculated. In this way, when the temperature and pressure of the medium under test change frequently, not only is the conversion process cumbersome, but it is also difficult to ensure measurement accuracy. With the development of modern science and technology, a number of measurement methods and instruments for directly measuring mass flow rate have emerged. The Coriolis mass flow meter truly enables high-precision direct mass measurement, which is exactly what many industrial applications are eager to have. Working principle of mass flow meters: A mass flow meter has a structure consisting of a double-bent U-shaped tube. Its measurement principle involves detecting the phase difference resulting from the Coriolis force acting on this double-bent tube, thereby determining the mass flow rate in the pipeline. Features of mass flow meters: Mass flow meters are capable of directly measuring the mass flow rate of the fluid in a pipeline. They offer high measurement accuracy and good repeatability, and enable direct measurement of the fluid’s mass flow rate over a wide range of ratios. It has a wide range of applicable media, including fluids with uniform viscosity, various high-viscosity, non-Newtonian fluids, slurries containing solid components, and media with trace amounts of gaseous components. 1) Accuracy as high as ±0.1%. 2) Meets the requirements set by the CFDA. 3) Service life of over 10 years. 4) Uses high-temperature vacuum brazing technology for greater stability in performance. 5) IP66 rating for dust and water resistance; it can remain functional after being submerged at 1 meter depth for 72 hours. 6) Ultra-low power consumption, with the total power usage not exceeding 10W. 7) Operated via photoelectric buttons, with real-time display of flow rate. Explosion-proof security interface operation, applicable in Zone 1 or Zone 2 explosive areas; 8) Alarm priority. Exceptionally fast response, enabling immediate access to alarm information. 9) Multi-parameter output: it is possible to display both cumulative values over time and instantaneous values for flow rate, density, and temperature; RS485 and analog signals are supported. 10) Historical data retrieval: in the event of an issue with the host computer, the historical data can be retrieved and viewed at any time. I. Application of mass flow meters in oil measurement 1.1 Application of mass flow meters in the measurement of gasoline and diesel The measurement of finished oil in trade has always been a matter of concern; disputes over measurements can lead parties involved to seek resolution from regulatory authorities. With the widespread use of mass flow meters, this contradiction has been effectively resolved. North Company requires that gasoline and diesel used for loading onto ships at sea be measured using mass flow meters. Through nearly two years of operation, this approach has proven to be very effective, with measurement errors remaining within acceptable limits of accuracy. The use of mass flow meters in trade transfers eliminates human factors in measurement, reduces the errors associated with traditional methods such as using a ruler to measure liquid levels, a glass rod to measure temperature, and a densitometer to measure density, thereby improving measurement accuracy. 1.2 Application of mass flow meters in gas metering High-purity gases (such as hydrogen with a purity of up to 99.99%) or gases with constant composition can be measured using mass flow meters for these high-value-added gases. Enter the density of the gas at standard conditions; by performing a conversion, its volume at standard conditions can be determined. Sinopec’s petrochemical branch purchases hydrogen (with a purity of up to 99.99%) in accordance with the specifications provided by the supplier; the supplier uses orifice flow meters equipped with temperature and pressure compensation, yet no changes are observed in the actual measurements. The midstream petrochemical branch installed a mass flow meter to monitor the volume of hydrogen supplied by the supplier. Measurements showed that the volume of hydrogen delivered was sometimes 30,000 NM3 less per day than what was supplied. After repeated comparisons between the two parties to identify the cause, it was determined that there was a problem with the design of the supplier’s orifice plate. 1.3 Application of mass flow meters in heavy oil measurement: Mass flow meters are widely used in the measurement of light oils, but their use in heavy oil measurement is still limited. Heavy oil measurement includes crude oil measurement and asphalt measurement. When using a mass flow meter to measure heavy oil, it is essential to address the issue of high viscosity, which can cause deposits to form on the inner surface of the measurement tube. Due to the wall-attachment phenomenon, which reduces the flow capacity of the measuring tube, the market value of the transmitter is on the high side. If the two measurement tubes are not hung evenly on the wall, it may cause abnormal vibration of the measurement tubes, preventing the sensor from functioning properly. Eliminating the wall-adhesion phenomenon mainly involves raising the temperature of the medium and keeping it in a flowing state. The transportation of oil products, especially asphalt, is often intermittent, making it quite important to implement proper heat tracing and insulation measures. The mass flow meter requires steam heating, with even heating on both sides, along with insulation using salt-wool and iron sheet. Keep the temperature of the medium inside the measuring tube above 80 degrees. To eliminate the effect of sticking to the wall and ensure the mass flow meter operates properly. Measuring crude oil with a mass flow meter eliminates the influence of trace, easily vaporizable components such as C1, C2, and C3. Improve measurement accuracy. II. Some issues to note in the application of mass flow meters 2.1 Zero drift issue The accuracy of a mass flow meter is given by: Accuracy = Basic accuracy ± Zero stability / Operating flow rate. Although preventive measures have been taken regarding zero drift in the manufacturing and calibration processes of Coriolis mass flowmeters to minimize it as much as possible, zero drift still occurs. At the lower flow rate, zero drift becomes significant. Zero drift mainly originates from the primary device, namely the sensor, and can be reduced through regular zero adjustment. 2.2 Effect of external stresses: When installing a Coriolis mass flow meter, especially the sensor, it is crucial to ensure a \"stress-free\" environment. This is \"stress-free,\" which means striving to avoid or minimize the stress caused by installation factors in order to ensure the proper functioning of the sensor. During installation, if there is a significant difference between the diameter of the mass flow meter tube and that of the main pipeline, it is recommended to install a U-bend in the main pipeline with the mass flow meter placed on this U-bend, in order to eliminate the effects of external stresses. 2.3 Effect of vibration: The principle and structure of the Coriolis mass flow meter mean that external vibrations can affect its measurements. In areas where pipeline vibration is severe, small-diameter flow meters can be installed; the inlet and outlet ends of the flow meter can be connected using hoses, while the flow meter itself is fixed to a solid and stable base or vibration-damping plate. When large-diameter flow meters are installed on such pipelines, expansion joints are sometimes used to reduce vibration, but a firmly supported short circuit must be installed between the expansion joint and the sensor; otherwise, the additional stresses caused by the expansion and contraction of the pipeline will lead to inaccurate measurement data. When installing two sensors in parallel on adjacent pipelines, it is also necessary to pay attention to maintaining a distance between them to prevent mutual interference. 2.4 Principle of optimal flow field distribution. Generally, the performance of Coriolis mass flow meters is not affected by vortex flows and non-uniform flow velocity distributions caused by the piping upstream and downstream; therefore, it is usually not necessary to provide straight pipe sections. Nevertheless, this principle of optimal flow field distribution is still followed in actual piping arrangements. Coriolis mass flow meters are widely used in oil field metering due to their distinct features and high accuracy. It is also receiving increasing attention from people. It is gradually becoming one of the important methods for measuring oil transfer.