b'GENERAL INFORMATION Flow measurement is typically Flow measuring techniques will vary depending on the application flow type.performed by inserting a There are two basic types of flow systems; closed channel, and open channel.mechanical meter, venture meter, A Closed Channel can be described as water flow through a completely filledmagnetic meter within the pipe. pressurized pipe. Flow measurement is typically performed by inserting aA typical example of a closed mechanical meter, venture meter, magnetic meter within the pipe. A typicalchannel flow is a city potable example of a closed channel flow is a city potable water line that is metered water line that is metered with a with a turbine meter.turbine meter. The second type of flow type, Open Channel, is best described as, water that flowsFEATURESwith a free surface typically in a non-pressurized (atmospheric) pipe or channel.High-Strength Precast BasinExamples are rivers, irrigation/drainage ditches, canals, and for sanitary sewer.Heavy-Duty Aluminum FramesThe most practical method for Open channel flow measurement is accomplished by the use of a hydraulic structure; flumes and weirs. These hydraulic structuresGalvanized Steel Bar Gratingenable flow calculation by measuring the water depth at a single point. And byHeavy-Duty Cast-Iron Cover and using the structures associated equation or table, the flow rate can be calculated. Frame RingOpen channels are used to conduct liquids in most sewer systems, sewage treatment plants, industrial waste applications, and irrigation systems.There are three methods for automatically measuring open channel flow:Hydraulic StructuresArea VelocitySlope-Hydraulic Radius MODELSWeirs Flumes Sample wellMODELS WeirsThe most common method of measuring open channel flow is the hydraulic structures method. A calibrated restriction inserted into the channel controlsthe shape and velocity of the flow. The flow rate is then determined by measuring the liquid level in or near the restriction. The restricting structures are called primary measuring devices. They may be divided into two broad categoriesweirs and flumes. A weir is an obstruction or dam built across an open channel over which the liquid flows, often through a specially shaped opening. Weirs are classified according to the shape of this opening. The most common types of weirs are the triangular(or V-notch) weir, the rectangular weir, and the trapezoidal (or Cipolletti) weir. The flow rate over a weir is determined by measuring the liquid depth in the pool upstream from the weir. Weirs can be simple and inexpensive to build and install. Common materials of construction include metal, fiberglass and wood. However, they represent a 362'