Small-Diameter Flow Measurement: Parshall Flume Open Channel Flow Meter [Dayu Electronics]
Small-diameter flow measurement is often challenging because the small pipe size can result in lower flow velocities, which affects measurement accuracy and reliability.
Project site conditions:
The site involves a DN90 stainless steel pipe that is frequently in a partially filled state, with only brief periods of full flow. How should flow be selected and measured for a small-diameter partially filled pipe? After on-site inspection and discussion, the final choice was a Parshall flume with an open channel flow meter.
Small-diameter Parshall flume open channel flow meter is mainly used to measure flow at wastewater treatment plants, discharge outlets of enterprises and institutions, and urban sewer systems. It consists of two parts: the open channel flow meter and the measuring flume. The measuring flume converts the flow rate in the open channel into a liquid level height. The instrument measures the water level in the measuring flume and then calculates the flow rate based on the water level-flow relationship of the corresponding measuring flume.
The main advantages of the Parshall flume open channel flow meter include being almost unaffected by changes in pipe wall roughness, minimal long-term drift in measurements, and relatively low head loss among non-full-pipe flow instruments.
Installation considerations
When installing the Parshall flume, it is necessary to choose an appropriate installation location to ensure smooth water flow and minimize the impact of debris. The installation location should be on a straight channel section with stable flow. The upstream straight section should be at least 3-5 times the channel width, and the downstream straight section should be at least 2 times the channel width. Additionally, ensure that the Parshall flume is tightly sealed with the channel bottom and side walls to prevent leakage.