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In the petrochemical industry, for flare systems, measuring gas emissions is a very important aspect. The complex and variable process environment in this system results in poor performance of various types of flow measurement instruments in actual use. The main difficulties lie in the following aspects: 1. The diameter of the gas main pipelines is large, usually over 500 millimeters; using non-insertion type measuring instruments makes installation and measurement very difficult. 2. The operating pressure of torch systems is low, often only a few kilopascals; those designed based on the principle of differential pressure measurement cannot be used in practice. 3. The flare system is filled with gas impurities, including oil and dirt, which can easily cause blockages in the sensing elements of measuring instruments; therefore, it must be cleaned regularly, which in turn limits the use of some sensitive and movable sensing elements. 4. The gas flow rate in the refinery’s flare system varies widely; at low flow rates, the velocity is usually between 0.01 and 1.5 meters per second. However, during accidents or when certain units are adjusted, the maximum velocity in the system can exceed 60 meters per second. Therefore, the measuring instruments used must have a very wide range. 5. The composition of gas is often very complex, containing various gas components such as hydrocarbons, hydrogen, nitrogen, hydrogen sulfide, etc. Moreover, the relative percentage content of each component is constantly changing, and these changes make measurements more difficult. Due to the constraints of these conditions, most measuring instruments cannot be used for gas flow measurement; currently, ultrasonic gas flow meters and thermal mass flow meters are those that are employed for this purpose. Due to their high cost and the fact that they cannot be used for measuring high-temperature gases, gas ultrasonic flowmeters are not a good choice; therefore, thermal gas mass flowmeters represent the better option. The SIERRA thermal gas mass flow meter uses unique inorganic fillers with nanoscale insulating properties in its core components; through high-pressure molding, it creates a patented \"dry sensor\" with zero drift, thereby ensuring that SIERRA’s thermal products exhibit excellent repeatability, long-term stability, and no drift. Regarding the concern of users about the multiple components in gas streams, SlERRA’s thermal products utilize a closed-loop gas flow calibration system. The calibration constants of the flow meters vary depending on the specific heat capacity and thermal conductivity of the fluid medium. In the petrochemical industry, the components of gas streams are mainly hydrocarbons, and these hydrocarbons have very similar specific heat capacities and thermal conductivities (as can be found in relevant literature); therefore, this has little impact on the measurement values. This has been proven through numerous application cases. Moreover, the measurement of flare gas flow is intended to determine the trend in flow rates, so accuracy is not the primary concern. What matters most is the long-term stability of the flow meter and the repeatability of the measurement data.