Gas flowmeter is a core instrument used for precise measurement of gas flow in industrial production, energy measurement, and scientific research experiments. Its accuracy directly affects the process control effect and data reliability. From the perspective of the entire lifecycle of selection, installation, operation, and maintenance, the key usage points are summarized as follows:
1、 Scientific selection - adaptation to working conditions is the foundation
Clarify the properties of the medium: Select compatible materials based on the composition of the gas being tested (such as fluorine/stainless steel probes for corrosive gases), distinguish between clean gases and impurity containing gas streams (the latter requiring the installation of a pre filter).
Range matching principle: Under normal operating conditions, the flow rate should be within the range of 20% to 80% of the calibrated range of the flow meter to avoid accuracy degradation or mechanical damage caused by long-term low flow rate or over limit operation.
Output signal adaptation: Select 4-20mA analog signal, pulse signal or RS485 digital communication protocol according to the control system requirements. For complex working conditions, it is recommended to use an intelligent flowmeter with temperature and pressure compensation function.
2、 Standardized installation - eliminating interference sources
Requirements for front and rear straight pipe sections: follow the "front 10, back 5" rule (i.e. upstream ≥ 10 times the pipe diameter, downstream ≥ 5 times the pipe diameter), avoid disturbance sources such as elbows and valves, and ensure stable fluid flow; If the space is limited, a rectifier can be used to improve the flow field.
Pressure tapping position: When installing a horizontal pipeline, the pressure tapping hole should be located on the side or top of the pipeline to prevent liquid condensed water from entering the measuring pipeline; Vertical pipelines must ensure unidirectional flow of the medium from top to bottom.
Vibration protection: Use a hose to connect the flowmeter to the pipeline, install a bracket to fix the equipment body, and configure shockproof joints for high-frequency vibration scenarios.
3、 Fine operation - ensuring measurement stability
Progressive start stop: Slowly open the valve before activation to avoid damage to the sensor caused by instantaneous high pressure impact; Gradually close during shutdown to prevent reverse negative pressure suction of impurities from blocking the channel.
Real time monitoring parameters: Observe the instantaneous flow rate, cumulative amount, and status indicator lights on the display screen, and immediately investigate the cause of severe fluctuations or alarm codes (such as sudden gas source changes or pipeline leaks).
Prohibited disassembly and assembly under pressure: Before maintenance, the upstream and downstream valves must be cut off and the pressure must be released, especially for high-pressure gas systems. Violation of regulations may result in spray injuries.
4、 Regular calibration - maintaining measurement accuracy
Calibration cycle setting: Calibration is conducted every 6 months under normal working conditions, and in harsh environments (with high dust and humidity), it is shortened to 3 months; Statutory mandatory testing shall be carried out in accordance with national standards.
Standard device comparison: Use a bell shaped gas flow standard device or sonic nozzle for physical calibration, and enter the correction coefficient into the instrument memory to update the original parameters.
Zero migration verification: Turn off the flow input and check if the output signal returns to zero. If the non-zero drift exceeds ± 0.5% of the full range, recalibration is required.
5、 Daily maintenance - extending service life
Cleaning of filtration system: Check the pre filter cartridge weekly, and replace it immediately if the pressure difference exceeds twice the initial value; Severe dirt can lead to a reduction in the flow area and result in false low flow readings.
Maintenance of electrodes/sensing components: Electromagnetic flow meters require cleaning of electrode surface scaling, thermal mass flow meter probes require annual replacement of high-temperature lubricating grease, and Coriolis force sensors should avoid severe mechanical collisions.
Ledger record management: Establish a file containing installation dates, calibration records, and fault history to facilitate traceability of performance degradation trends.
The reliable application of gas flow meters relies on a four in one management strategy of "selection, installation, stability, and maintenance". In practical operation, it is necessary to combine the user manual of specific models, focus on the dynamic matching of medium characteristics and working conditions, reduce measurement risks through standardized operating procedures, and ensure the authenticity and effectiveness of data.