When the Burkert electromagnetic flowmeter is operated on-site and the instrument indication is minimum and the regulating valve opening is normal, the cause of the failure is likely to be insufficient system pressure.
When the Burkert electromagnetic flowmeter is operated on-site and the instrument indication is minimum and the regulating valve opening is normal, the cause of the failure is likely to be insufficient system pressure, system pipeline blockage, pump failure to increase volume, medium crystallization, improper operation, etc. cause. If the indicated value of the flow control instrument system fluctuates frequently, the control can be changed to manual. If the fluctuation decreases, it is caused by the instrument or the instrument control parameter PID is inappropriate. If the fluctuation is still frequent, it is caused by the process operation. If it is an instrument failure, the reasons include: the orifice plate differential pressure flowmeter may have a blocked positive pressure pilot conduit; the positive pressure chamber of the differential pressure transmitter may be leaking; the mechanical flowmeter may have a stuck gear or blocked filter, etc. When the indicated value of the flow control instrument system reaches the minimum hour, first check the on-site detection instrument. If it is normal, the fault lies in the display instrument. When the on-site detection instrument indication is also the smallest, check the opening of the regulating valve. If the opening of the regulating valve is zero, it is often a fault between the regulating valve and the regulator.
When the flow control instrument system indicates the maximum value, the detection instrument will often indicate the maximum value. At this time, the regulating valve can be opened or closed manually via remote control. If the flow rate can be reduced, it is generally caused by process operation. If the flow value does not drop, it is caused by the instrument system. Check whether the regulating valve of the flow control instrument system operates; check whether the instrument measurement and pressure-inducing system is normal; check whether the instrument signal transmission system is normal. The flow meter sensor contains two sensing elements, a speed sensor and a temperature sensor. They automatically compensate and correct for gas temperature changes. The electric heating part of the instrument heats the speed sensor to a certain value higher than the working temperature, so that a constant temperature difference is formed between the speed sensor and the sensor that measures the working temperature. When the temperature difference is kept constant, the energy consumed by electric heating, which can also be said to be the heat dissipation value, is proportional to the mass flow rate of the gas flowing through it. Mass flow meter is Mass Flow Meter (abbreviated as MFM). It is a new type of instrument in gas flow measurement. It is different from other gas flow meters that do not require pressure and temperature correction and directly measure the mass flow of gas. One sensor can cover the range. From very low to high range. It is suitable for the measurement of single gases and fixed proportion multi-component gases. Flowmeter is a new instrument used to measure and control gas mass flow. It can be used to monitor air, hydrocarbon gases, flammable gases, and flue gases in industrial sectors such as petroleum, chemical industry, steel, metallurgy, electric power, light industry, medicine, and environmental protection.
It can be considered from five aspects, which are flowmeter instrument performance, fluid characteristics, installation conditions, environmental conditions and economic factors. The detailed factors in the five aspects are as follows. In terms of instrument performance: accuracy, repeatability, linearity, range, flow range, signal output characteristics, response time, pressure loss, etc.; in terms of fluid characteristics: temperature, pressure, density, viscosity, Chemical corrosion, abrasiveness, scaling, miscibility, phase change, electrical conductivity, sound speed, thermal conductivity, specific heat capacity, isentropic index; pipeline layout direction, flow direction, length of straight pipe section upstream and downstream of the test piece, pipe diameter, maintenanceSpace, power supply, grounding, auxiliary equipment (filter, air eliminator), installation, etc.; environmental conditions: ambient temperature, humidity, electromagnetic interference, safety, explosion-proof, pipeline vibration, etc.; economic factors: instrument purchase fee, installation Fees, operation fees, calibration fees, maintenance fees, instrument service life, spare parts, etc. The steps for flowmeter instrument selection are as follows: Select the available instrument types based on the fluid type and five considerations (there must be several types for selection); collect data and price information for the preliminary types to prepare for in-depth analysis Compare the preparation conditions; use the elimination method to gradually focus on 1 to 2 types, and repeatedly compare and analyze the five factors to finally determine the pre-selection target. Fluid characteristics mainly refer to the pressure, temperature, density, viscosity, compressibility, etc. of gas. Since the volume of gas changes with temperature and pressure, you should consider whether compensation and correction are needed. Instrument performance refers to the accuracy, repeatability, linearity, range ratio, pressure loss, starting flow, output signal and response time of the instrument. When selecting a flowmeter, the above indicators should be carefully analyzed and compared to select an instrument that can meet the flow requirements of the measurement medium. . Installation conditions refer to the gas flow direction, pipeline direction, length of upstream and downstream straight pipes, pipe diameter, spatial location and pipe fittings, etc. These will affect the accurate operation, maintenance and service life of the gas flow meter. Economic factors refer to purchase fees, installation fees, maintenance fees, calibration fees and spare parts, etc., which are also affected by the performance, reliability, lifespan, etc. of the gas flow meter. Accuracy Level and Functions Select the instrument accuracy level according to the measurement requirements and usage occasions to achieve economical results. For example, when it is used for trade settlement, product handover and energy measurement, the accuracy level can be selected, such as level 1.0, level 0.5, or higher. When it is used for process control, different accuracy levels can be selected according to the control requirements. In some cases where it is just to detect the process flow without control and measurement, you can choose a slightly lower accuracy level, such as level 1.5, level 2.5, or even level 4.0. In this case, you can choose a low-cost plug-in electromagnetic flowmeter to measure the medium flow rate, When measuring general media with instrument range and caliber, the full-scale flow rate of the electromagnetic flowmeter can be selected within a wide range of the measurement medium flow rate of 0.5-12m/s. The instrument specification (diameter) selected is not necessarily the same as the process pipeline. It should be determined based on whether the measured flow range is within the flow rate range.
That is, when the pipeline flow rate is too low to meet the requirements of the flow meter or the measurement accuracy cannot be guaranteed at this flow rate, it is necessary to Reduce the diameter of the instrument to increase the flow rate in the pipe and obtain satisfactory measurement results. It can only measure the liquid flow of conductive media, but cannot measure the flow of non-conductive media, such as gas and heating water with better water treatment. In addition, its lining needs to be considered under high temperature conditions. The electromagnetic flowmeter determines the volume flow rate under working conditions by measuring the speed of conductive liquid. According to the measurement requirements, for liquid media, the mass flow rate should be measured, and measuring the medium flow rate should involve the density of the fluid. Different fluid media have different densities, and they change with temperature. If the electromagnetic flowmeter converter is not consideredFor fluid density, it is inappropriate to only give the volume flow rate at normal temperature. The installation and debugging of electromagnetic flowmeters are more complicated than other flowmeters, and the requirements are more stringent. The transmitter and converter must be used together, and two different types of instruments cannot be used together. When installing the transmitter, from the selection of the installation location to the specific installation and debugging, the product instructions must be strictly followed. There should be no vibration or strong magnetic field in the installation location. During installation, the transmitter and pipeline must have good contact and good grounding. The potential of the transmitter is the same as that of the fluid being measured. During use, the gas remaining in the measuring tube must be exhausted, otherwise it will cause large measurement errors. When the electromagnetic flowmeter is used to measure viscous liquids with dirt, the sticky matter or sediment adheres to the inner wall of the measuring tube or the electrode, causing the output potential of the transmitter to change, causing measurement errors. If the dirt on the electrode reaches a certain thickness, it may As a result, the meter cannot measure. Scale or wear of the water supply pipeline changes the inner diameter, which will affect the original flow value and cause measurement errors. For example, a 1mm change in the inner diameter of a 100mm diameter instrument will bring about an additional error of about 2%. The measurement signal of the transmitter is a very small millivolt level potential signal. In addition to the flow signal, it also contains some signals that have nothing to do with the flow, such as phase voltage, quadrature voltage and common mode voltage. In order to accurately measure flow, it is necessary to eliminate various interference signals and effectively amplify the flow signal. The performance of the flow converter should be improved, and a microprocessor-type converter should be used to control the excitation voltage. The excitation mode and frequency should be selected according to the properties of the fluid being measured, so that in-phase interference and orthogonal interference can be eliminated. However, the improved instrument structure is complex and the cost is high.
Hangzhou Economic Development Area，Hangzhou 310018，China
