What are the factors that affect the accuracy of natural gas flowmeters?
2021-05-17
Factors that affect the accuracy of natural gas flowmeters:
1. natural gas flow meter measuring elements aging, wear
Through investigation and analysis, it is found that most of the current natural gas measurement system equipment built in China has been running for more than 4 years, after careful observation, it will be found that the bearings, impellers and electrical components used are worn, aging and deformation, which eventually lead to inaccurate flow meter measurement. At this stage, the natural gas transported in the natural gas pipeline is not a very pure natural gas, which contains some small particles, such impurities have no effect on the use of natural gas, but will affect the components of the meter measuring instrument, resulting in aging, deformation, wear and other problems. In addition, the flow meter is exposed to the external space for a long time, and is extremely susceptible to the influence of external temperature and humidity, which also causes problems such as aging, deformation, and wear of the component, so it affects the accuracy of the meter.
2. Failed to correct natural gas flow measurement parameters in time
Flow meter coefficient mainly refers to the corresponding relationship between the volume of the measuring medium and the signal generated by the measuring component. On this basis, turbine flow measurement can be conducted, and it can be known that the rotating speed of the impeller is in a positive proportion to the passing speed of the gas in a certain flow range. The corresponding coefficient between the gas volume and the impeller pulse generated by the above analysis is the flow meter coefficient. The specific value of the meter is determined by verifying the meter through the gear rotation and the function of the integrator, and then the meter coefficient is set into the flow meter. Through experienced analysis, it is not difficult to see that the close relationship between the instrument coefficient and the bearing and the impeller is because there is generally a small error in the machining accuracy, and the coefficient of each flow meter is different under the influence of this error. And the long-term trial of the impeller and bearing will appear aging, deformation, wear and other problems, will promote the instrument coefficient deviation. If the relevant staff does not carry out regular verification work according to the needs, the instrument coefficient error will always exist under the long-term use, and the accuracy of the natural gas metering instrument will gradually decrease.
3. The equipment is not installed and maintained as required
There are instructions to guide the installation personnel during the installation and commissioning phase of natural gas metering meters, but in actual operation, it is found that some installation personnel use their own way to install and debug work in order to improve the work progress during the installation and maintenance phase, so that the natural gas metering function will be damaged, and the accuracy of natural gas metering meters will be affected in serious cases. The current common problems in the installation of natural gas metering meters are: first, the meter parts will melt due to high temperature after welding and cause deformation, thus losing the rectification effect. Second, the flatness of the pipes at both ends is not enough, and the forced installation of the metering instrument will cause the enhancement of the stress effect of the flow meter, and the problem of deformation will occur in the long run. Third, the pipeline is not cleaned according to the demand in the commissioning stage, which will lead to impurities colliding with the instrument components in the use of the pipeline, reducing the accuracy of the measuring instrument.
4. Input media
The measuring instrument will carry out the calibration of the general medium and the working medium in the factory, and the reflected value is also different. If the air is used as the medium in the factory calibration, and the air is not used as the medium in the specific use, the error will occur because of the difference in the medium, which is because the viscosity presented in different media is different. Based on this, it should be ensured that the indicating medium of the calibration flowmeter is consistent with the working medium in the metering instrument. In addition, in the field working environment, the environmental medium must be different from the medium used, so the accuracy of the meter is affected. In practical use, it is necessary to ensure that the medium is pure and clean.
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