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Analysis and Verification of Mass Flow Meter

Analysis and Verification of Mass Flow Meter


Anatomy of a mass flow meter

For the Coriolis force mass flowmeter, it mainly uses the principle of Coriolis force, which can be used to accurately and directly measure the mass flow of fluid in closed pipelines. Its coriolis meter working principle is also the principle of Coriolis force, that is, according to the flow characteristics of the fluid in the closed pipeline, that is, to maintain a linear motion and to be in a rotational motion, a Coriolis force proportional to the mass flow will be generated, and the corresponding metering appearance.

Advantages of thermal mass flowmeters mainly include the following aspects: First, it has a relatively high range, which can reach the range of 20:1 to 50:1 under normal conditions, and the range of some meters can be above 100:1; second, it can effectively carry out direct flow control. The measurement has high measurement accuracy and good stability; the third is that it can use a wide range of media, which is suitable for the measurement of dirty natural gas; the fourth is that it can effectively carry out corresponding maintenance and cleaning operations to ensure that Further increase in service life; Fifth, it is especially suitable for process control of custody transfer measurement.

For thermal mass flowmeters, the pipe is mainly heated by the fluid flowing through the external heat source. At this time, the measurement of the fluid mass flow is described by the change in the temperature field that occurs. Or, using the fluid heating process, In the process of reaching a certain temperature, there is a corresponding relationship between the energy required for temperature rise and the mass of the fluid to measure the mass flow of the fluid and develop a mass flow meter.

Coriolis flow meter working principle is as follows: The gas flow measurement process is measured by the corresponding cooling effect of the gas flowing through the heating element in the flow meter. Generally speaking, there are two thermal resistance elements in the measuring section where the gas passes, one mainly realizes the function of the heater, and the other performs effective temperature detection. In such a situation, the gas temperature is detected by the temperature sensing element, and it should be ensured that there is a constant temperature difference between the measured gas temperature and the heating space, which is accomplished by the heater with respect to the current change.

Verification of mass flow meters

Mass flow meters are generally only used for the measurement of liquid flow, and its verification is usually done in the laboratory (flow standard device) and its specific conditions. This is what we usually call off-line verification. We know that the verification purpose of the mass flowmeter is to determine the measurement performance of the meter in actual use. There are the following problems in laboratory verification: ①The verification medium is different from the actual measured medium, and its physical parameters are also different; ②The working conditions during the verification, such as temperature and pressure, are inconsistent with the application conditions of the flowmeter; ③The installation type of the flowmeter There are also big differences in the same field.

The above shows that the verification or performance evaluation of the mass flowmeter in the laboratory is different from the actual performance of the flowmeter, which is far from the goal of accurate measurement. For example, when coriolis type mass flow meter are used in custody transfer measurement, this difference is likely to be the source of disputes between buyers and sellers and must be reduced.

Under the current technical conditions, it is difficult to correct the verification conditions of the flowmeter to the application conditions. There is no way to correct the typical viscosity correction, let alone some unmeasurable factors (such as installation, flow state, etc.) etc.) amendments. Therefore, the best solution to this problem is to perform online verification of the mass flowmeter.

The on-line verification of mass flowmeter is a kind of real liquid verification. Compared with laboratory verification, it has many particularities or requirements. In summary, there are mainly the following points:

(1) There must be a fixed or movable flow standard device for calibrating the mass flowmeter. In addition to the accuracy of the device meeting the requirements, the operating temperature range, pressure rating and media compatibility of the device must also meet the online verification requirements. If it is a mobile flow standard, the device is also required to be light and flexible;

(2) During the verification process, the fluid needs to be in a closed state to ensure that the verification working conditions do not change, and also ensure the safety of the verification site;

(3) It is not allowed to interrupt the fluid during the verification process;

⑷. If the flow meter to be tested is verified by a mobile standard device, the site where the flowmeter is located must have corresponding interfaces, valves and supporting recovery and cleaning facilities, venues, power supplies, etc.

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