选型规则(1)涡街流量计变送器的选择我公司在饱和蒸汽测量中采用明通仪表有限公司生产的VA型压电式涡街流量变送器，由于涡街流量计量程范围宽，因此，在实际应用中，一般主要考虑测量饱和蒸汽的流量不得低于涡街流量计的下限，也就是说必须满足流体流速不得低于5m/s。 Vortex flowmeter selection rules (1) Selection of vortex flowmeter transmitters Our company uses VA type piezoelectric vortex flow transmitters produced by Mingtong Instrument Co., Ltd. for saturated steam measurement. The measuring range is wide. Therefore, in practical applications, it is generally considered that the measured flow of saturated steam should not be lower than the lower limit of the vortex flowmeter, that is, the fluid flow rate must be not less than 5m / s. Vortex flow transmitters with different calibers are selected according to the amount of steam used, and the caliber of the transmitter cannot be selected based on the existing process pipeline caliber.
(2) Selection of pressure-compensated pressure transmitters Due to the long saturated steam pipeline and large pressure fluctuations, pressure compensation must be used. Considering the correspondence between pressure, temperature and density, only pressure compensation can be used in the measurement. The saturated steam pressure of Tongtong pipeline is in the range of 0.3-0.7MPa, and the range of the pressure transmitter can be selected as 1MPa.
(3) Display meter selection Display meter Intelligent flow rate displayer with functions of voltage stabilization compensation, instantaneous flow rate display and cumulative flow rate accumulation. Most settings for vortex flowmeters
(1) For the setting of the instrument system, the instrument coefficient K to be set by Tiankang Instrument General Factory can be expressed by the following formula: K = 1000 / K0 where: K0 is the instrument constant calibrated by the Vortex generator at the factory, L / Pulse; the unit of k is the number of pulses / m3.
(2) Range setting of pressure compensated pressure transmitter.
(3) Upper limit setting of pressure and flow alarm.
3.Installation of vortex flowmeter
(1) The vortex flowmeter should be installed as far as possible away from the source of vibration and strong electromagnetic interference. Vibration reduction devices must be used where vibration exists to reduce the impact of vibration on the pipeline.
(2) For the configuration of straight pipe sections, the front and rear straight pipe sections must meet the requirements of the vortex flowmeter, and the inner diameter of the pipe must be the same as the inner diameter of the vortex flow transmitter.
4. Use precautions of vortex flowmeter to minimize the impact of the steam hammer on the vortex street generator in the pipeline.
流量计本身质量问题后，大多数都是现场安装的问题，对常见的速度式流量计来说，可能情况有： Generally speaking, after eliminating the quality problems of the vortex flowmeter itself, most of them are field installation problems. For common speed flowmeters, the possible situations are:
1. Is the straight pipe section in front of the flowmeter long enough (generally 10 times the inner diameter of the pipe), and must not contain elbows, bypass pipes or other impurities, flow blocking parts, etc.
2. Is the flowmeter installed upstream of the regulating valve?
3. Is there any vibration on site?
4. Is the flow rate too small to reach the lower limit of the flowmeter's measured value?
The following flowmeter manufacturers give a specific example of a vortex flowmeter:
When the coke oven gas is unstable, the output signal of the vortex flowmeter is unstable for the following reasons:
1. Vortex flowmeters are not suitable for installation in places with strong vibrations, which are widely known by users. However, in situations where the magnetic field changes frequently, the vortex flowmeter will measure a signal output higher than normal. Practice has proved that in a scene where no gas flows, when the vortex flow sensor is in a changing magnetic field, the vortex flow sensor will sense an error signal and output it when the magnetic field changes. When the change is over, the meter is in a stable magnetic field. The meter will output a normal signal. 2. Due to the high temperature and high humidity of the coke oven gas when it leaves the factory, there will be moisture in the gas transportation process. The gas flow drives the water back and forth to form a pulsating flow. When the vortex flow sensor is in this fluid state, the output data is suddenly large or small, and it cannot reflect the production status at all. 3. The crimping wire is not solid during the instrument wiring process, which causes the signal to be intermittent during transmission. 4. The ground wire of the instrument does not meet the requirements of the specification, so that 50Hz interference in strong electricity enters. When the normal signal is higher than 50Hz, a normal signal is output, otherwise an error signal is output. 5. Because the coke oven gas has many impurities, it is easy to crystallize, and the impurities are condensed on the sensor head, which causes measurement inaccuracy. When the temperature increases, the impurities evaporate, the sensitivity increases, and the signal increases; on the contrary, it decreases. As a result, data is unstable.
测焦炉煤气不稳定解决办法： Vortex flowmeter for unstable measurement of coke oven gas:
1. During the installation and connection of the instrument, ensure that each link is accurate, including field inspections before installation, instrument wiring, and system grounding lines during installation, so as to ensure that real data is detected and can be accurately output. . 2. For the measurement system in operation, the method of “dual-track measurement, comparison and confirmation”, and the “replacement method” can be used to confirm and eliminate the measurement instrument failure in operation. 3. Regularly drain the pipeline, especially the water before the straight pipe section, and set a special person to discharge it regularly according to the specific conditions, reduce the water in the metering pipe section as much as possible, and eliminate the pulsation in the fluid to the maximum extent. 4. Strengthen the management of the measurement system data, set the timing printing function, and analyze the operation of the instrument based on the printed data combined with the production status. 5. Regularly clean the instrument as a whole. If necessary, purge the sensor head to avoid condensation of impurities at the sensor head. In the cold season, adding a heat tracing device to the metering straight pipe section and the meter part is also beneficial to alleviate the condensation of impurities at the metering meter.