How to measure natural gas with precession vortex flowmeter to ensure accuracy
2021-05-13
The precession vortex flowmeter is a kind of instrument device for measuring gas medium, because it has no mechanical moving parts, corrosion resistance, stability and reliability, long life, long-term operation without special maintenance; The mechanical and electrical integration is realized, and the daily measurement process does not need manual duty; The process installation conditions are not harsh, and the upper and downstream straight pipe section of the instrument can be greatly shortened compared with the orifice plate and vortex flowmeter. The measurement accuracy of the system can meet the current requirements of trade measurement and internal assessment.
The main cause of deviation of precession vortex flowmeter
1. The performance of the meter itself
(1) Straight pipe section
Whether the length of the straight pipe section is qualified affects the performance of the meter itself, because the measurement results are limited to the flow state of the fluid medium, so in the front and back parts of the flow meter, there should be a long enough qualified straight pipe section to ensure the stable flow of the medium. Generally, the front straight pipe segment is not less than 5D, and the back straight pipe segment is not less than 1D.
(2) Flow range
Due to different specifications, the flow range of the flowmeter is also different, at the same time, the flowmeter can not detect the flow below the lower limit, it is difficult to ensure its accuracy; At the same time, when the gas volume is high and exceeds the standard, it will cause loss of pressure, pulse loss, missing measurement, etc., in this case, it is simply more difficult to ensure its accuracy.
(3) Stress
Pressure detection plays a decisive role in the accurate measurement of gas, the pressure of the detection point is inversely proportional to the relative error, the higher the pressure, the relative error will be smaller and smaller, therefore, in the selection of flow timing, to fully take into account the high pressure of the working condition, in turn to select the appropriate sensor range.
How to ensure the precision of the precession vortex gas flowmeter:
To this end, it is necessary to implement three selection parameters, namely, the recent and long-term and common flow rate (mainly used to select the nominal diameter of the flow meter), the design pressure of the measured medium (mainly used to select the nominal pressure level of the instrument), and the actual working pressure (mainly used to select the pressure level of the pressure sensor of the flow meter).
(1) When the measured flow rate is known to be the working volume flow rate, the appropriate nominal diameter can be directly selected according to the flow range in the table;
(2) When the measured flow rate is known as the volume flow rate under standard conditions, the volume flow rate under standard conditions should be converted to the volume flow rate under working conditions, and then the corresponding nominal diameter should be selected according to the flow range in the technical parameter table;
(3) When the two caliber flowmeters can cover low and high volume flow, under the pressure loss allowed, small caliber should be selected as far as possible;
(4) Do not make the actual small flow Qmin lower than the flow limit of the selected nominal runoff meter;
(5) When the flow range and nominal pressure have special requirements, the agreement can be ordered.
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