The flow measurement in water treatment is one of the most important aspects of industrial water technology. In times of increasing quality requirements and stricter environmental regulations, there is a precise Flow and flow measurement Easy for efficient processes and sustainable resource use. This guide shows you how to do the right one Flow technology Select and successfully use for your water treatment plant.
Why is the flow measurement so important?
The Flow measurement in water treatment Forms the backbone of modern water technology. Without reliable flow data, neither doses of preparation chemicals can be controlled precisely, nor processes can be optimally monitored. It is of central importance in various areas of water treatment, for example with the:
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surveillance of the water cycle in processing plants
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Precise regulation From chemical additions
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steering of sewage basin and ventilation systems
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Compliance Legal requirements for wastewater disposal
The continuous flow monitoring enables it Leak, Consumption or hydraulic irregularities to recognize early. This is particularly crucial for one in extensive care networks Sustainable and economic water supply.
The most important measurement principles for water pipes
In practice, several measurement methods are used. Depending on the application, different principles are suitable:
Magnetic-inductive flow measurement
The Magnetic-inductive measurement principle is particularly suitable for flow measurement in water treatment. It is based on the Faraday's induction law: If a conductive liquid flows through a magnetic field, an electrical voltage is induced in the liquid - proportionally to the flow speed. This voltage is recorded by electrodes and converted into a flow value.
Advantages of magnetic-inductive measuring devices:
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Very high measurement accuracy (typical ≤ 0.5 % of the measured value)
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Negligible pressure loss (no installations that brake the river)
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Bidirectional measurement possible (including direction recognition)
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Works reliably from a minimum conductivity of the medium (approx. 20 μs/cm for water)
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Long -term stable measurements through digital signal processing and no moving parts
Ultrasonic flow measurement
The Ultrasonic flow measurement It is also ideal for the flow measurement in water pipes because they Regardless of conductivity, pressure, temperature or viscosity of the medium works. Ultrasonic impulses are either runtime -based or by means of Doppler procedure used to determine the flow speed.
There are two main variants of ultrasonic flowers:
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Inline measurement recipients: Fixed installation in the tube with guaranteed accuracy (usually backed up by factory calibration).
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Clamp-on sensors: Sensors for attaching outside on the pipe, without to separate the pipe or to interrupt the process.
Special advantages of ultrasound measurement:
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Is ideal for subsequent assembly On existing lines (especially Clamp-on systems)
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Also recorded aggressive or especially pure liquids without problems (no touch with medium required)
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Suitable for pipe materials of different types (metal, plastic etc.)
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Can be used on very large pipe diameters (with clamp-on, sizes up to about DN 4000 are possible)
Different pressure flow measurement
The Different pressure measuring method Use throttle elements like Glare, Jet or Venturi pipesto indicate the flow from the resulting pressure drop. This proven principle (described in the standard DIN EN ISO 5167) is used especially for large pipes in water treatment. The advantage is the robust technology; However, the installations cause permanent loss of pressure and require a sufficiently long input and outlet route for precise results.
(In addition to these methods presented, there are other measurement principles, such as mechanical flap meters, coriolis mass flow meters or vertebral meters. However, the above-mentioned have proven themselves in the context of the water treatment.)
Selection criteria for flow meters
The choice of the appropriate flow meter depends on several factors that should be taken into account:
Consider medium properties
When choosing the right measuring device for the Flow measurement in water treatment At first the properties of the medium are decisive. Important parameters of the water to be measured (or medium) include:
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Phase: Is it a liquid (water), a gas or steam?
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Conductivity: Is the water sufficiently conductive (important for magnetic-inductive procedures)?
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Temperature and pressure: Are there temperature and pressure in the area of the device specification?
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Viscosity and density: Does the medium deviate significantly from the properties of water?
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Impurities: Does the water contain solids or gas bubbles that could affect the measuring principle?
These factors limit the appropriate measurement principles. For example are Magnetic-inductive counter ideal for conductive liquids, while at very pure or deionized water often Ultrasound counter are preferable.
Define technical requirements
The technical framework of the measuring point also plays a major role:
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Required measuring range and accuracy: Select the measuring device so that the normal operating flow is in the upper third of the measuring range. Most industrial applications require an accuracy of around 0.5–2 % of the current measured value.
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Minimize pressure loss: Pay particular attention to the pressure loss behavior of the measuring device in large systems. A high permanent drop in pressure means increased energy costs (pump output). Magnetic-inductive or ultrasound flow meters have an advantage here because they are practical no additional pressure loss cause.
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Output and control: Think about which outputs and communication interfaces are required (e.g. 4–20 mA, pulse, hard, modbus) and make sure that the device supports this.
Installation and commissioning
One Correct installation is crucial for precise measurement results. Even small assembly errors can significantly affect measuring accuracy. So note the following points:
Correct positioning in the pipe system
Installation location and inlet routes: Choose a straight tube section for the measuring device, as far as possible from interference. Are usually at least 10 pipe diameter Route in front of the measuring device (inlet route). Optimal are even about 25 pipe diameter undisturbed inlet route. According to the measuring device, as a discontinued route at least 5 pipe diameter be free of disorders - better still 10 pipe diameter. If there are interference sources such as pumps, valves, arches or narrowing immediately beforehand, they extend the inlet route accordingly so that the flow profile can calm down.
Avoid unfavorable installation sites: Do not install the flow sensor at unfavorable points in the system. For example, avoid:
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High points of the pipelinewhere air bubbles could collect.
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Areas with strong vibrations Or in the vicinity of electrical/magnetic interference fields (can influence measuring signal).
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Very inaccessible areasthat would be difficult to reach in the event of a maintenance.
Avoid frequent installation errors
Improper assembly can lead to considerable measurement errors or tool damage. Typical problems are:
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Different pipe diameter: The measuring device does not match the actual pipe diameter (leads to turbulence or dead zones).
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The above seals: Sealing rings that protrude into the tube disturb the flow profile.
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Inadequate enema/run-off routes: The above -mentioned recommendations were not observed, which causes restless flow at the measuring point.
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Deposits in the measuring pipe: Especially with magnetic-inductive devices, coverings on the electrodes can falsify the measurement. Regular cleaning is important (see maintenance).
Calibration and maintenance
Even after installation, flow meters must be maintained and checked in order to provide precise values in the long term.
Calibration: The regular Calibration of flowers is essentialto ensure measurement accuracy and process reliability. Even low measurement deviations can lead to incorrect doses or inefficient process processes. In practice, the following rule of thumb has established itself: At least once a year If a flow meter is calibrated or checked. In critical or officially monitored applications (e.g. in the case of measurements subject to the calibration) are also Half -year intervals recommended. In addition, the following applies: after major maintenance work, changes to the system or if noticeable measured value deviations occur, one is one Expert -planned calibration to carry out. Also note relevant standards and legal requirements that can prescribe calibration intervals.
Maintenance: In addition to the calibration preventive maintenance to ensure reliable operation. Important measures are, for example: regular Visual exams the measuring point (on leaks, corrosion, mechanical damage), which cleaning of sensors and electrodes (to remove deposits or vegetation), as well as the Review of electrical connections And the control of Seals and other mechanical components. A preventive maintenance plan can significantly reduce failures and measurement errors. Note that Mechanical flow meter (with movable parts) usually have a higher maintenance effort than contactless Measurement systems such as ultrasound or magnetic-inductive devices.
Note norms and standards
For the Flow measurement in water technology There are national and international norms that define methods and requirements. These standards ensure that measurement results from different systems are comparable and certain quality requirements are met. Important norms in this area include:
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DIN EN ISO 5167: Describes the flow measurement with throttle devices (e.g. blinds, venturir tubes) in full pipes.
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DIN EN ISO 748: Standard for flow measurement in open channels (e.g. for flow channels, weirs - rather relevant for wastewater/above -ground waters).
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ISO 3354: Regulates the flow measurement of Pure water in closed lines by means of special measuring routes.
When using flow measurement technology, it should always be checked whether one of these standards (or other specific industry standards) must be observed - especially at official acceptance or Calibration. Compliance with the standards ensures comprehensible and recognized measurement results.
Product recommendation: FlowGuard® FT410 by Seikom Electronic
For particularly demanding applications in water treatment, we would like to highlight a specific device: this Magnetic-inductive Flow meter FlowGuard® FT410 the company Seikom Electronic. This device is a real one All-round talent for the precise flow measurement And combines robustness with high measurement accuracy.
Technical highlights of the FlowGuard® FT410:
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Measurement area: 0.06 to 12 m/s flow speed (covers a large spectrum)
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Measurement accuracy: ≤ 0.5 % of the measured value (very precise)
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Measuring direction: Bidirectional, with automatic Recognition and Empty (recognize if there is no medium in the tube)
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Output signals: Diversity of interfaces - pulse output, 4–20 mA analog signal and digital connection via HARD or Modbus
Special suitability for water treatment:
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Drinking water approval: On request, the device is available with drinking water certification, important for use in the drinking water network.
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High level of protection: Until Protection class IP68 Available, i.e. protected against the penetration of water even during diving operation - ideal for difficult environments.
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Flexible versions: Various process connections (flange, threads etc.) and linings (e.g. PVDF, PTFE) available to adapt to a wide variety of water qualities and pipe materials.
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ATEX versions: For use in Explosion -prone areas (e.g. in certain industrial water processes) the FlowGuard® FT410 is also available in ATEX-certified execution.
The FlowGuard® FT410 is configured in a customer -specific way and still delivered quickly - typically, the delivery time is only about 3 weeks. With its robust construction, precise measurement technology and the diverse adaptation options, this device is ideal for the Continuous flow monitoring in water treatment plants and supply networks.
