Acoustic Flow Measurement – Applications Overview

Water is the most precious resource on our planet and its disparate distribution makes managing water a real challenge. To tackle this challenge, investments in automation of wastewater, hydropower, irrigation, hydrology and water supply systems have increased significantly. Today, most predictions and actions are derived from collected data. This requires higher data quality and granularity. Hence, the precise measurement of flow rates and consumption as well as the communication of data are becoming increasingly important.

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Process control and surveillance.

The observation and control of wastewater is of highest importance. Today’s civilization is unthinkable without functioning wastewater treatment plants. Wastewater contains a multitude of organic substances which are treated or removed and then discharged again into the environment. Advanced collection systems are required to transport wastewater to the right place at the right time in order to protect ecosystems. These collection systems are highly complex and consist of channels for wastewater flow, clarification plants and overflow basins. GWF solves flow measurement challenges in all of these areas globally.

For further details, please refer to our wastewater products.


Ultrasonic Pulse-Doppler systems

For sewage-treatment plants, flow measurements are primarily installed for internal reasons, for example to operate specific plant components depending on flow rate or for controlling additives. International regulations, such as the EU directive for handling municipal wastewater, require a continuous surveillance of wastewater flow. Defective flow measurements in sewage-treatment plants can therefore not only influence their operation, but also cause legal or environmental consequences.

The Q-Eye PSC and the Q-Eye PSC Portable flow meters are designed for flow monitoring of slightly to heavily polluted media in full or partially full pipes or open channels. The Q-Eye PSC systems use advanced “Doppler profiling technology” to directly measure velocity profiles, making them the best choice for sites with non-uniform, rapidly changing, backwatered, near zero, negative or reverse flow conditions. This technology eliminates the need for on-site calibration, thereby significantly reducing the cost of installation.

Picture: Q-Eye PSC Portable Installation in manhole



Insertion type – only for stationary system

For stationary Q-Eye PSC with partially filled or full pipes


Mouse type – for both stationary and portable systems

For both stationary and portable Q-Eye PSC with partially filled pipes or open channels


Non-contact Radar Doppler systems

Q-Eye Radar is an exceptionally versatile flow measurement system designed for continuous operation and suitable for application not only in rivers and open channels, but also in municipal wastewater and storm water sewers. Compact construction combined with the non-contact measurement principle enables an easy installation and use. The Q-Eye Radar is designed to accept any depth sensor (ultrasonic, radar and submersible) with an analog input (4-20 mA). Our Q-Eye Radar transmitter offers the best in wastewater measurement.


Advantages of non-contact measurement

In some applications it is an advantage to have a non-contact measurement. By combining both a radar velocity and a water level sensor, we provide a revolutionary approach to open channel, river, and wastewater flow monitoring.

As the Q-Eye Radar system is installed outside of the liquid, your personnel will not get in contact with the polluted fluid during installation. Furthermore, the need for maintenance caused by sensor fouling or deposits is eliminated.


Make optimal use of potential energy.

Hydropower is an important source of energy which is able to cater to the increased need for power supply to the earth’s population. Today, hydropower plants deliver approximately 3.5 per cent of electric energy generated worldwide. Their share in power generation from renewable resources comes to 18 per cent. This share is continuing to grow as resources of fossil fuels are depleted and investments in alternative energy
sources grow.

Hydroelectric performance depends essentially on the usable altitude difference between upper reservoir and lower reservoir. In order to use the potential energy in an optimal way, flow should be accurately monitored over the long term.

For further details, please refer to our hydropower products.


Travel Time system with digital signal processing

Acoustic flow measurement systems have long established themselves as a reliable and convenient method of determining turbine efficiency. Measurements in several planes according to international standards are recommended for this task. With this method, there is no need for calibration and a deterioration of turbine or hydraulic efficiency can be detected at an early stage. A further area of application is the detection of leaks, where at least two systems are permanently installed. Because of the accuracy of the Ductus system, even small leakages can be detected instantaneously.


A variety of transducers is available – depending on your requirements

Internal mount sensors can be fixed directly to the wall. The transducers are aligned by rotating them in their mounting into a predefined position and then fixed in place by tightening. Feedthrough sensors are employed for installation through exposed penstock walls with access to the interior and/or exterior of the penstock flow meter section.

Picture: 4 planes crossed according to IEC 41 / ASME PTC 18


Advantages of Clamp-On systems

When combining the Ductus system with Clamp-On transducers, the flow measurement becomes non-intrusive. The transducers are installed with little technical effort and without process interruption on the pipeline. Clamp-On transducers require no modification of the conduit or plant shutdown.
Rotationally symmetric flow profiles can be determined with a single acoustic path; non-symmetric profiles require the use of several acoustic paths.

The multi-path clamp-on measurement is also available as a portable system for rent or for measurement services. Contact us, we will be happy to show you the possibilities of the Ductus M Portable System.

Picture: Clamp-On with 2 acoustic paths


Detect leakages as early as possible.

Channels are artificially created waterways used, among others, for transportation, irrigation, drainage, drinking water supply and water extraction for power. Especially for applications in the supply of drinking water, it is crucial to detect leakages at an early stage. Our instruments measure man-made channels, tunnels and aqueducts precisely in order to prevent long term water losses and support process stability.

For further details, please refer to our irrigation / channel products.


Travel Time system with digital signal processing

Kanalis is a velocity area open channel flow meter which uses the acoustic Travel Time method. This method assumes no relation between level and flow, like weirs or flumes. It will correctly determine flow throughout its designed range by measuring water velocity and depth.

For installation in open channels or closed conduits, Kanalis operates over the fully bi-directional flow range without causing obstruction or head loss. Onsite characteristics such as varying water levels, skew flow or complex channel shapes are taken into account via specific path configurations.


Single-path system

In its most basic form, the system operates with a single pair of transducers. This measurement relies upon a stable velocity profile unaffected by changes in the relation between water level and flow. The main flow must be parallel to the bank. The relationship between measured velocity and flow is established by hydrometric calibration.

Crossed-path system

Ideal for channels with cross-flow conditions. This depends mainly on the channel’s geometry and whether there is an upstream bend in the conduit. Although cross-flows do not influence the total flow volume, they may affect the measurement accuracy. A second pair of transducers is required to capture these variances in velocity profiles. By crosswise arrangement of four transducers, effects of changing flow direction can be eliminated.

Multi-path system

An even more accurate measurement can be obtained through systems using several planes. The measured result can be further improved by using a multi-path system layering each of the acoustic paths in parallel planes one above the other. This removes the need for an expensive hydrometric calibration. Such a system is suitable for applications with large water level fluctuations, reverse flow or a vertical velocity distribution outside the theoretical normal.


24/7 monitoring for rivers.

Numerous rivers intersect our landscape from small brooks up to huge river networks. Some of them form a natural border between two countries.

Since early times, man has preferred to live near rivers. Clean water, transportation, power generation and scenic beauty are amongst the reasons. However, our actions have more and more influence on water quantity and quality. In many regions, depletion of water for irrigation or human consumption are the reasons. More than half of all big rivers around the world have been polluted during the course of time and their stewardship is essential for the future survival of ecosystems.

Observations of water levels have been used since ancient times, systematic flow measurements go back to the middle of the 19th century. This historical data has been used as the basis for various applications, for example flood protection and flood forecasting. They also form the foundation for the design of hydro-engineering constructions.

In recent years, acoustic flow measurement has established itself as a standard method for measurement in many hydrological stations. With this technology, data can be recorded continuously, thus providing 24/7 monitoring.

For further details, please refer to our hydrology products.


Travel Time system with digital signal processing

The range of application for Fluvius runs from small waterways to huge river systems with high suspended solids concentration. A coded acoustic signal is sent through the water and the transit time is calculated, which provides the speed of flow. When an acoustic wave propagates in water, part of the energy is damped by friction and suspended solids. This procedure is frequency-related. The higher the frequency, the bigger the damping. Therefore, low frequencies allow for a considerably better receiver signal for wide distances.


Choice of transducer frequency

Commonly used transducer frequencies for various path lengths and sediment loads

For an overview of available transducers, please refer to our hydrology products.


Efficient operation of piping networks.

Although there is enough water on earth and it is not consumed but merely used, access to a reliable supply of clean, safe, potable water is becoming scarcer. Uneven distribution of water amongst regions and the planet’s rising population lead to a global shortage of fresh potable water. More and more aqueducts for drinking water are being built all over the world. In order to operate large and complex piping networks efficiently, flow measurement is necessary for long term reliability and control.

For further details, please refer to our water supply products.


Travel Time system with digital signal processing

The Ductus S flow meter is a fully integrated Transit Time metering solution with up to 10 acoustic paths for liquid fluids. It increases your profitability with exceptional repeatability and linearity throughout the flow range. Due to the patented velocity profile compensation, no flow straighteners or on-site calibration are required. Ductus S can be used with either insertion feedthrough sensors or external Clamp-On sensors.


Determine the full flow velocity profile

Space constraints and application configurations lead to complex flows in pipes which contain elbows, tees or other disturbing and non-uniform elements. This leads to difficulties in installing flow meters at an optimum location; which is defined by a minimum distance upstream or downstream of known disturbances at which a fully developed velocity profile is present. Even with multiple flow sensors, significant errors may be present.

The Ductus S acoustic system provides detailed information on the flow velocity profile. An accurate measurement of the flow rate can be achieved by rebuilding the flow velocity profile across the pipe using predetermined conduit configuration parameters and correction factors.

Flow meters are also sensitive to velocity profiles with a large rotational component (swirl). Swirl is generated by two or more out-of-plane changes in flow direction. It is present to some extent in almost every application and can generate significant transverse velocity components; and it takes a long distance to dissipate. If the swirl is not accounted for, it can cause significant errors. The Ductus S system keeps its measurement accuracy even when asymmetric profiles and swirls are present in the pipe.

Picture: flow meter after a 90° elbow


Easy installation and replacement

Ductus S is available with a variety of transducers. Please refer to our water supply products for further information.

In the unlikely event that a transducer should fail, the Ductus S can be programmed to automatically compensate for the loss in path information with little reduced accuracy in addition to advising the operator that an alarm is present. The transducer housings are separate from the transducers, and are designed to allow removal of the entire transducer for repair, replacement or cleaning without the need to dewater the pipe or shut down the process.

When combining the Ductus S with Clamp- On transducers, the flow measurement becomes non-intrusive. The transducers are installed with little technical effort and without process interruption on the pipeline. Clamp-On transducers require no modification of the conduit or plant shutdown.

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