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1 Introduction With the rapid development of industrial technology, there are an increasing number of flow measurement instruments, each with its own working principle and characteristics. The process requirements placed on flow measurement instruments are becoming increasingly stringent, and the operating conditions are becoming more complex. Most of the flow meters in use today have measurement values that change as process parameters such as pressure, temperature, and density vary; therefore, when the actual operating conditions differ from those designed, additional errors occur in the measurement instruments. The Micromotion mass flow meter measures mass flow directly during the measurement process, unaffected by changes in the properties of the medium, which is why it is widely used. Eight Micromotion mass flow meters are used in the second set of polyoxymethylene units, with their tag numbers being FT-3102, FT-3107, FT-5101, FT-5102, FT-5206, FT-5501, FT-5513, and FT-6201. Seven Micromotion mass flow meters are used for pentaerythritol, with their tag numbers being FT-1026, FT-6575, FT-1004, FT-1003, FT-1002, FT-1001, and FT-3029. 2 Working principle of the Micromotion mass flow meter: http://nfs.gongkong.com/Upload/editor/201610/20161024100040761_w.png. Depending on the application, the sensors of the Micromotion mass flow meter can be classified into E series, D series, T series, F series, and R series flow tubes. When used in combination with various transmitters such as 1700, 2700, and RFT9739, these sensors can meet the various requirements of users. The 1700 model is a single-variable transmitter, while the 2700 model is a multi-variable transmitter. The main difference lies in the output: the 1700 can only output the mass flow rate for display on secondary instruments. The 2700 can output the mass flow rate, density, and frequency to a secondary instrument for display. Users can make a choice based on their own process requirements. The Micromotion mass flow meter consists of a sensor, a transmitter, and a display. The measuring tube is vibrated by an excitation coil; when the flowing fluid passes through the measuring tube of the mass flow meter, a Coriolis force is generated. Under the action of this force, the measuring tube deforms. The distortion signal is converted into an electrical signal by the left and right detection coils located on the measuring tube, and this signal is sent to the transmitter for further processing. http://nfs.gongkong.com/Upload/editor/201610/20161024100019370_w.png Figure (1): Schematic diagram of the Micromotion mass flow meter. The function of the transmitter is to process the low-level signals or binary signals received from the sensor, amplify them, and output standard signals such as 4–20 MA signals proportional to flow rate and density, or frequency/pulse signals, or digital signals. If the transmitter and sensor are separate, they need to be connected using a dedicated cable, with the distance between them not exceeding 300 M, in order to prevent signal attenuation and interference during long-distance transmission. Monitors or other terminal devices receive signals from transmitters, and typically display in digital form information such as the instantaneous flow rate, cumulative flow rate, mass flow rate, density, temperature, and other parameters of the fluid being measured. Advantages of the 3 Micromotion mass flow meter: (1) It can directly measure mass flow rate, unaffected by factors such as temperature, pressure, viscosity, and density; its measurement accuracy can reach 0.1%–0.2%. (2) There are no moving mechanical parts; although the detection tube vibrates, the amplitude is very small, so friction does not affect the measurement results. (3) It has a wide range of applications; in addition to measuring ordinary media, it can also measure highly viscous fluids and slurries, as well as gases. (4) It features a wide adjustable range ratio, which can reach up to 1:100. (5) It is not sensitive to the flow velocity distribution of the fluid; it is unaffected by laminar or turbulent flow conditions, and no straight pipe sections are required before or after installing the instrument. (6) While measuring flow rate, it is also possible to obtain a signal of the medium’s density; there is no need for periodic sampling using other techniques to measure the density of the fluid online. (7) It can measure bidirectional flow. Disadvantages of Micromotion mass flow meters: (1) The instability of the sensor’s zero point leads to zero-point drift, which hinders further improvement in accuracy; as a result, many models of such instruments have to divide the total error into two components: the basic error and the zero-point instability. (2) Sensors cannot be used to measure low-density media and low-pressure gases ； A gas content in the liquid that exceeds a certain limit (varies by model) will significantly affect the measurement values. (3) Sensors are relatively sensitive to external vibration disturbances; to prevent the impact of pipeline vibrations, most models of flow sensors require high standards for installation and fixation. (4) It cannot be used for larger pipe diameters; it is currently limited to below 150 (200) mm. (5) Wear, corrosion, or deposition of scale on the inner wall of the measuring tube can affect measurement accuracy, especially for sensors used in thin-walled measuring tubes. 4 Precautions for installing the Micromotion mass flow meter: (1) The mass flow meter performs measurements by utilizing the vibration of sensors; to avoid external interference, the installation location should not have any significant sources of vibration, and reinforcement measures should be taken to stabilize the pipes in the vicinity of the instrument. (2) A mass flow meter requires an excitation magnetic field to function; therefore, it cannot be installed near devices that generate strong magnetic fields such as large transformers, motors, or pumps. It must be kept at a distance of at least 0.6–1.0 meters from them to avoid interference. (3) No stress (mainly torque) should be present when connecting the sensor of the mass flow meter to the pipeline; it is crucial to install the sensor to the process components and process pipelines without any stress. Pay special attention to reducing stress on the process connections; properly aligning the process pipes with the flanges and maintaining coaxiality can help reduce stress. Valves or pumps located on the process pipelines near the sensor require their own supports; the sensor’s mounting base or the connectors used in the process cannot be used to support such pumps or valves. (4) When sensors are used in series within a pipeline, the two sensors installed in series should be secured using pipe clamps, thereby preventing vibrations from the inner tube of one sensor from being transmitted to the other sensor through the pipeline. (5) Straight-tube mass flow meters should be installed vertically, so that the measurement pipeline can be emptied when the instrument is not in use, thereby preventing scaling. If installed horizontally, the two measurement tubes need to be at the same level. (6) When a bent-tube flow meter is installed horizontally, if it is used to measure liquids, the housing should face downward to prevent gas from accumulating inside the measurement tube; if it is used to measure gases, the housing should also face downward to avoid the accumulation of condensate in the measurement tube. (7) To prevent any flow during zeroing, shut-off valves are installed upstream and downstream of the sensor to ensure no leakage. The control valve should be installed downstream of the sensor, so that the sensor can maintain as high a static pressure as possible to prevent cavitation and flashing. 5. Transmitter parameter configuration: Use HART275 or HART375 to configure the transmitter’s parameters. During this process, it is necessary to enter the flow calibration coefficient, density calibration coefficient, K1, K2, D1, D2, and other parameters specified on the sensor’s nameplate into the transmitter using the HART communicator. Set parameters such as the measurement range, parameter units, small-signal rejection amount, and instrument coefficients. The configuration menu is shown in the figure below. 6 Considering the company’s application scenarios, Micro Motion mass flowmeters offer advantages such as high measurement accuracy, strong reliability, and low maintenance requirements; however, some failures can still occur over time. The common methods used to identify faults that occur are as follows: 6.1 Check whether the wiring of sensors, the main processor, and flow transmitters is secure and reliable, and whether the grounding wires are in good condition. Check whether the power supply is functioning properly; there are two types: 24VDC power supply and 220VAC power supply. Most of our company’s equipment is powered by 24VDC, while pentaerythritol FT6575 is powered by 220VAC. 6.2 Checking the parameter settings of the flow transmitter Meter factors: These factors include the mass flow factor, volume flow factor, and density flow factor. The default values for these factors are all “1”; generally, there is no need to modify them during use. If pressure correction is required, it can be done by calculating based on the pressure in the actual application and the pressure used during factory calibration. Last time, the FT-1001 for pentaerythritol was unable to display the mass flow rate; the underlying cause was found to be a mass flow coefficient of “0”. Once the mass flow coefficient was changed to “1”, it started working properly. Flow calibration coefficient: The flow calibration coefficient must be identical to that indicated on the sensor’s nameplate or in the calibration certificate issued by a qualified metrological authority, in order to ensure accurate flow measurement. Note that the flow calibration coefficients vary significantly among different sensor models. Density coefficient: The density coefficient must be the same as that indicated on the sensor’s nameplate, in order to ensure that the flow transmitter displays an accurate density value. Range: Configure the flow range of the flow transmitter appropriately based on the actual usage in the process. Flow cut-off: Under normal circumstances, the flow cut-off parameter should be 0.05% of the sensor’s maximum flow rate. If a flow cut-off parameter equal to 0.05% of the sensor’s maximum flow rate proves to be impractical, a higher or lower flow cut-off parameter can be entered. Zero drift can be suppressed by setting the flow cut-off parameters of the mass flow meter and zeroing the flow meter. If the inspection reveals that the mass flow transmitter is damaged, no need to reset the parameters when replacing it with a new one, as all parameter configuration data is stored in the sensor’s core processor. 6.3 Zeroing the flow meter: Failing to zero the flow meter before putting it into normal use can result in unnecessary errors in the mass flow meter’s readings. Before proceeding with the steps to zero the flow meter, the sensor must be properly installed, the flow transmitter must be powered on, and it should be preheated for at least 30 minutes. The fluid to be measured should then be passed through the sensor until the temperature reading of the sensor is essentially the same as the temperature of the fluid. Ensure that the sensor’s measurement tube is completely filled with the fluid to be measured under normal operating conditions (such as temperature, density, and pressure). First, close the shut-off valve downstream of the sensor, and then close the shut-off valve upstream of it, so as to ensure that the fluid inside the sensor remains completely still. When zeroing a flow meter, the flow of fluid through the sensor can result in inaccurate zeroing, which in turn affects the measurement accuracy of the mass flow meter. If zeroing the mass flow meter fails, it is necessary to eliminate issues such as an unfilled sensor measurement tube or fluid that is not completely stationary, and then attempt zeroing again. Scaling or drift deposition on the inner wall structure of the measuring tube can also affect measurement accuracy; therefore, it needs to be cleaned regularly. 6 Conclusion The Emerson Micromotion mass flow meter features high precision, good stability, low maintenance requirements, and a long service life. By fully understanding its working principle and characteristics, and by summarizing maintenance experience from the faults encountered in daily operation, it is possible to remove dirt from within the flow sensor tube during major repairs, thereby ensuring normal operation during production processes. Proper installation and appropriate use and maintenance are necessary to ensure accurate flow measurement, thereby providing reliable flow data for industrial automation and trade transactions.