Arkon flow system

Parshall flume is a primary flow element with a wide range of application for measuring open channel flow. It can be used for flow measurement in creeks, irrigation and/or drainage channels, sewer outfalls, Waste Water and Effluent Treatment Plants, etc. The flow rate measurement is based on the assumption that the critical flow is produced by constricting the width in the throat of the flume and then raising the bottom. The flow changes from subcritical to supercritical and then the measurement of a single depth is sufficient to determine the discharge. The water level is measured and recorded either in the center line of the approach channel using an ultrasonic level sensor or inside a stilling manhole (which can be a part of Parshall flume) by means of a float with a mechanical transfer to a flow rate, or using a sensor with an electronic unit. The electronic unit transforms the measured flow depth to a flowrate. Main advantages can be summarised as follows: a) A relatively low energy loss( 3-4 times lower than in sharp-crested weirs). b) A small sensitivity to a velocity distribution in an approach channel. c) Velocities inside Parshall flumes are high enough to prevent them from the deposition of sediments or accumulation of debris. d) Minimum maintenance requirements. e) A wide range of flow rates. f) A long lifetime.