Mass flowmeter in liquid gas flow measurement in the successful application of: Yang Xinan Wang Yunhui: Henan Pele Petrochemical Group Co., Ltd. Abstract: This paper introduces the principle of mass flow meter and problems in the liquefied gas flow measurement and The solution, the typical problem, the method is practical and reliable, for design and maintenance, operator reference. Keywords: mass flowmeter; principle; liquefied gas; gas; pressure 1 mass flow meter Introduction Fluid flow in the rotating tube will produce a wall force, it is Coriolis discovered in 1832 when the turbine, Known as Coriolis force. The mass flowmeter is based on Coriolis force. There are two parallel T-type vibrators in the sensor. The middle part is equipped with driving coil. The two ends of the mass flow meter are equipped with a pick-up coil. When the excitation voltage provided by the transmitter is added to the driving coil , The vibration tube reciprocating cycle vibration, the industrial process of the fluid medium flow through the sensor tube vibration, will produce Coriolis force on the tube effect, so that the two vibration tube torsion vibration, mounted on both ends of the pick-up coil coil Two sets of signals of different phases are generated, the two signal differences being proportional to the mass flow of the fluid passing through the sensor. The computer calculates the mass flow through the tube. Different media flow through the sensor, the vibration frequency of the main vibration tube, thus calculating the medium density. The platinum resistance mounted on the transducer tube indirectly measures the temperature of the medium. The mass flowmeter directly measures the mass flow through the media of the flowmeter, as well as the density of the media and the temperature of the indirect measurement media. As the transmitter is a single-chip smart meter as the core, it can be derived according to the above three basic parameters for a dozen parameters for users to use. Mass flowmeter configuration flexibility, powerful, cost-effective, is a new generation of flow meters. The main technical indicators of mass flowmeter (1) The main parameters: Mass flow accuracy: ± 0.002 × flow ± zero drift Density measurement accuracy: ± 0.003g / cm3 Density measurement range: 0.5 ~ 1.5g / cm3 Temperature measurement range: ± 1 ° C (2) Sensor related data: Ambient temperature: -40 ~ 60 ° C Medium temperature: -50 ~ 200 ° C Explosion-proof type: iBⅡBT3 Associated equipment: Supporting transmitter (3) Transmitter related data: Operating temperature: 0 ~ 60 ° C Relative Humidity: 95% or less Power: 220 ± 10% VAC, 50Hz or 24 ± 5% VDC, 40W2 Mass Flow Meter Installation Example 1 In order to meet the expansion of our gas fractionation plant, The design and construction of the propylene loading system were carried out. Propylene flowmeter used the mass flow meter produced by Taihang Instrument Factory Flowmeter. After the installation started, the flowmeter work has been normal, but the cumulative amount is larger than that of the electronic scale deviation. Analysis of the reasons: (1) Through discussions with process personnel, the possibility of inaccurate instrumentation could be ruled out due to excessive dry gas (5%) in liquefied gas. (2) Remove a set of instruments of the same specification from the gas fractionation unit and observe the same, the phenomenon is the same, ruled out the possibility of flowmeter damage. (3) To this end, we sent someone to Zhongyuan Oilfield Refining & Chemical Company to inspect the factory liquefied gas loading system flow meters are used mass flow meter, cast more than two years, the work has been normal, indicating the accuracy. The process and instrument installation and I plant approximation, the flow chart is as follows: The factory special emphasis on steps: After the start of loading, the first car line valve d, until the pressure gauge c, f show the same value, and then Open the gas phase to return to the hand valve g, and we originally loaded the car is the beginning of the hand valve d, g all open, then the loading line pressure is much higher than the pressure inside the tank, it is very easy to tank The remaining part of the propylene flush into the propylene tank, resulting in measurement error. After improving the operation method, the system is working normally, achieving accurate quantitative loading and improving work efficiency. Example 2 In order to meet the transformation of our gas fractionation plant, our company conducted the design and construction of liquefied gas desulfurization unit in early 1998, in which the flow meter of liquefied gas out of thiol device adopted the mass flow produced by the flowmeter branch factory of Taihang Meter Factory Meter device started, the flowmeter has been abnormal work, the specific performance of instantaneous flow frequently back to zero, but also shows the entrained gas alarm code. Analysis: (1) Through the joint discussion between the instrument manufacturer and the craft staff, the possibility of meter inaccuracy caused by exceeding the dry gas level (5%) in liquefied gas is excluded. (2) The gas fractionation device demounted to a set of the same specifications of the instrument put on the observation, the same phenomenon, ruled out the possibility of flowmeter damage. (3) It is also observed that the instrument zero return and medium pressure. To this end, we sent to Luoyang Petrochemical Engineering Company experimental plant inspection, the plant two sets of catalytic devices liquefied gas devices are used mass flow meter, cast more than two years, the work has been normal, indicating the accuracy. One set of instruments measured medium pressure 1.0MPa, another set of measured medium pressure 2.0MPa. Other areas similar to our factory. Liquefied petroleum gas desulfurization plant liquefied gas plant pressure of 0.6 ~ 0.9MPa, the observation, the media pressure is lower than 0.75MPa, the instrument instantaneous value back to zero. According to this judgment, the saturated vapor pressure of liquefied gas produced by our company at 0.75MPa (due to incomplete data, which is difficult to calculate based on the chromatographic test results), the amount of liquefied gas evaporated by this pressure exceeds 5% (M / M ), Resulting in mass flow meter shows the instantaneous flow back to zero. After consultation with the process and the operator, the sensor of the mass flowmeter is installed at the outlet of the liquefied gas feed pump of the sweetening unit, where the medium pressure is not lower than 1.3MPa and the pressure is stable. After transformation, the quality of the flowmeter is stable, accurate measurement, to achieve the desired results.
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