Some people may know little about open channel flow meters. They are actually a monitoring device to detect or measure the flow of the fluid in a conduit with a free surface, known as open channels and can be divided into non-contact type and contact type in terms of their working principle. As you may know that though there are different kinds of flow meters used for open channels, the non-contact type, for example, ultrasonic open channel flow meters may be the most suitable choice to measure the flow rate of liquids with viscosity for outdoor projects.
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Advantages of Ultrasonic Open Channel Flow Meters
The reason for such open channel flow meters lies in that generally there are thick liquids running in the open channels, like sewage, wastewater, so the first thing to consider when selecting such a device to measure flow rate is whether it can measure medium without clogging or corrosion problem concerned. Non-contact flow meters have three obvious advantages that firstly no matter which medium is to be measured, it has no worry about device corrosion, blocking and cleaning difficulty resulted from the measured medium, thus the maintenance cost is reduced.
Secondly, unlike electromagnetic flowmeters that require full capacity of liquid inside pipes, they have no much requirement on the capacity of medium to be measured but note that there must be consistent flow, and besides they are applicable for most flumes and weirs, like rectangular or triangular flumes, Parshall flume and etc. Last but not least, considering these open channel flow meters are used in outdoor applications, their enclosure is made of weatherproof injection molded plastic so it is suitable for use in a wide variety of environments, though in harsh conditions.
With increasing demand in recent few years, open channel flow meters have a wide range of applications in wastewater treatment plant, sewage outfalls, city sewers or farmland irrigation. But note that they must be installed correctly, if not, then the overall accuracy will be diminished.
Features & Benefits
Features & Benefits
The Alsonic SAVM-Sewer Transit Time is perfect for wastewater treatment plants, municipalities, and industrial facilities that need to monitor and manage sewer flow rates accurately.
Features & Benefits
The Alsonic DAVM-Sewer Doppler is ideal for economic open channel monitoring, mainly used for sewers and surveying applications where cost-effectiveness and portability are essential.
Features & Benefits
The Alsonic RAVM-Microwave Radar is perfect for applications that require accurate, non-contact flow measurement in open channels with particles or waves, offering easy installation, low maintenance, and suitability for remote, solar-powered sites.
At Smart Measurement, we specialize in providing innovative and reliable open channel flow measurement solutions for a wide range of industries. Our extensive product line includes state-of-the-art ultrasonic transit-time, radar combined with microwave Doppler, partially filled magnetic as well as traditional Doppler open channel flow meters, each designed to deliver accurate and dependable performance in challenging environments. Our expert team is dedicated to helping customers find the perfect open channel flow meter for their unique needs, offering personalized support and customized solutions.
Open channel and partially filled pipes require the measurement of both area and velocity known as Area-Velocity Measurement (AVM) measurement. Fluid velocities are measured by either ultrasonic or magnetic transducers coupled with a level measurement device and a flow computer for complete flow profiling of the partially filled pipes or channels.
Traditionally, flow in channels and partially filled pipes are measured by using primary elements such as flumes or weirs in conjunction with a liquid level transducer and a flow computer. Flumes and weirs have been around for over a century, flow velocities are inferred by their shapes with only a level measurement device to estimate their flow rates. These systems are highly inaccurate because their shape will erode over time as well sedimentation will accumulate at their bottom.
Open channel flow meters are devices used to accurately measure the flow of water or other liquids in open channels such as rivers, streams, canals, or partially filled pipes. These meters play a crucial role in various applications, including:
Open channel flow meters utilize different technologies to determine the flow rate based on the water level and velocity in the channel. They all have two separate sensors, one velocity and another level.
Selecting the appropriate open channel flow meter depends on factors such as the application requirements, channel characteristics, desired accuracy, and budget. Some key considerations include:
Consulting with experienced flow measurement professionals can help ensure the optimal selection and implementation of open channel flow meters for your specific application.
SmartMeasurement offers the ALSONIC-SAVM, a variant of the ALSONIC-AVM, specifically designed for cylindrical conduits like those in sewer systems. This model excels in profiling velocities in small channels, even with limited straight runs, making it ideal for sewer applications.
The ALSONIC-SAVM is tailored for open channel pipes or conduits ranging from 6-60 inches (150-mm). It features the same display module as the ALSONIC-AVM but is equipped with a pre-configured cylindrical 4-path transducer array, ensuring easy installation. This array calculates flow velocity with the same high accuracy as the standard ALSONIC-AVM.
Designed for adaptability and precision, the ALSONIC-SAVM is an optimal solution for measuring flow in cylindrical channels, offering the reliability and accuracy synonymous with SmartMeasurement&#;s ultrasonic technology.
Discover more about our Ultrasonic Water Technology and its applications here.
To compensate for overflow due to rain and surges municipalities of times required swage piping in which the pipe is never full so to compensate for overflow flows. These are called partially filled pipes where standard flow metering requiring continuous filled pipes will not work. These partially filled applications require a flowmeter that measures fluid velocity as well as the liquid level in the pipe.
SmartMeasurement&#;s ALMAG PF is an electromagnetic Partially Filled Pipe Flow Meter featuring an electromagnetic flow velocity sensor combined with a ultrasonic liquid level sensor for a complete and continuous Area Velocity flow measurement. Users only need to input the inner diameter of a circular pipe or the width of a square pipe, and the Almag PF will automatically calculate the flow rate in the pipe. The Almag PF transmitter automatically displays the instantaneous flow, flow velocity, cumulative flow and other measure- ment parameters in the pipeline. Compared with flowmeters measuring the flow rate by means of flow level, the obstruction-less ALMAG PF flow-meter is not affected by mud, sands and other solid sediment because the sensors are on the opposite sides of the flow body. It is also unaffected by waves or floating solids on the fluid surface.
ALMAG PF is an electromagnetic Partially Filled Pipe Flow Meter featuring an electromagnetic flow velocity sensor combined with a ultrasonic liquid level sensor for a complete and continuous Area Velocity flow measurement.
Specifications
Open channel flow meters offer several advantages over traditional methods like flumes or weirs:
Smart Measurement&#;s open channel flow meters offer accurate flow measurement in open channels and partially filled pipes. Our meters are suitable for a wide range of applications, including water resource management, irrigation, wastewater treatment, stormwater monitoring, and industrial discharge measurement. With low maintenance requirements, our meters provide reliable, long-term performance. Some unique benefits of Smart Measurement&#;s open channel flow meters include:
Open channel flow meters are used in a variety of applications, including:
Area velocity flow meters differ from other types by combining a submerged velocity sensor with an ultrasonic level sensor to calculate the flow rate. This technology offers several advantages for certain applications, such as:
Open channel flow meters rely on two key measurements to determine the flow rate:
By multiplying the cross-sectional area of the flow (calculated using the liquid level and channel dimensions) with the average velocity, the flow meter can accurately compute the volumetric flow rate using the following equation: Flow Rate (Q) = Cross-sectional Area (A) × Average Velocity (V)
Several technologies are employed in open channel flow meters to measure liquid level and velocity:
Theory of Open Channel Flow
Velocity Measurement Transit-Time Ultrasonic
Velocity Measurement Doppler Ultrasonic
Level Measurement Radar
Theory of Open Channel Flow
Robert Manning (22 October &#; 9 December ) was an Irish hydraulic engineer best known for creation of the Manning formula. The Mannings equation is an empirical equation that applies to uniform flow in open channels and is a function of the channel velocity, flow area and channel slope. Under the assumption of uniform flow conditions the bottom slope is the same as the slope of the energy grade line and the water surface slope.
Q = a x 1.486/n x R2/3 x S1/2
Input Data: Area = ft² Mannings &#;n&#; = Wetted Perimeter = ft Slope = ft/ft
Results: Hydraulic Radius = ft Flow Rate = cfs Velocity = ft/s
Velocity Measurement Transit-Time Ultrasonic
Fluid velocity is measured by sending an ultrasonic pulse from an upstream transducer to a downstream transducer and back again. These signals are emitted alternately in the flow direction and against it. As the fluid in which the signals propagate is flowing, the transit time of the ultrasonic signals in the flow direction is shorter than against the flow direction. The resulting difference in transit time, &#;t, is measured and allows the flowmeter to determine the average fluid velocity along the propagation path of the ultrasonic signals. A flow profile correction is then performed in order to obtain the area averaged flow velocity, which is proportional to the volumetric flow rate based on user-entered information about the process application.
Velocity Measurement Doppler Ultrasonic
Level Measurement Radar
Level measurement using radar technology is based on the reflection of microwaves on surface media. All media have a dielectric constant. The higher it is, the stronger the reflection of the microwaves will be. Vacuum gives no reflection at all and has a dielectric constant of 1. Radar level transmitters use top-down waveguides to generate and direct microwave pulses downwards into a containment vessel. These signals propagate through the headspace due to the low dielectric constant, or relative permittivity (Er), of gas and vapor.