【2025 Flow Meters】Selection of Flow Meters for Non-full-pipe Conditions
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This post was last edited by The one on 2025-11-7 09:13. The vast majority of traditional flowmeters (such as electromagnetic, vortex, turbine, etc.) require the pipeline to be filled with fluid. In the case of non-full pipes (or open channels/partially filled pipes), there is gas – usually air – above the fluid, which can significantly affect the accuracy of measurements and even damage the instruments. 1. Ultrasonic Level/Flow Meter: This is currently the most widely used and mainstream solution for measuring flow rate in systems where there is no full pipe volume.
2. Electromagnetic Flow Meter – equipped with a function for measuring when the pipe is not completely filled. Note: Ordinary electromagnetic flow meters must not be used when the pipe is not fully filled, as this can lead to inaccurate measurements and may damage the electrodes. However, there are electromagnetic flowmeters specifically designed for measurement in partially filled pipes.
This post was last edited by The one on 2025-11-7 09:14. 3. Flume/Venturi Flume + Level Meter: This is a classic measurement method, particularly suitable for open channels and large-diameter pipes.
➡ Measurement principle: A throttling device of a specific shape (Bashel groove or triangular weir) is installed in the channel or pipe. When fluid passes through this device, throttling occurs, and the liquid level rises at a specific position in the tank (upstream of the throat). There is a fixed mathematical relationship between this increased liquid level and the flow rate. By measuring this liquid level height, the flow rate can be calculated accurately. Level gauges usually use ultrasonic level gauges or pressure-type level gauges.
➡ Advantages: ① Simple structure, durable, and requires minimal maintenance. ②Fluids containing a large amount of suspended solids (such as mud) are less likely to get clogged. ③Wide measurement range. ➡ Disadvantages: ① Requires significant installation space, with strict requirements for the straight sections ahead and behind it. ②There will be a certain head loss. ③The accuracy depends on the machining precision of the groove and the precision of the liquid level measurement.