A collection of electromagnetic flowmeters from KROHNE

Electromagnetic flowmeters

For all applications with conductive liquids

  • From basic to demanding flow measurements, incl. custody transfer and safety-related applications (up to SIL 2/3)

  • Designs and liner materials for virtually any application – from potable water to extremely adhesive, abrasive and aggressive liquids

  • Large choice of nominal sizes up to DN3000 / 120"

When is an electromagnetic flowmeter used?

An electromagnetic flowmeter (EMF), also known as a magnetic flowmeter, magmeter or electromagnetic flow meter, is used for the highly accurate measurement of the volumetric flow rate of electrically conductive liquids. Typical applications include water, wastewater, slurries, sludge, pastes, chemicals, acids, alkalis, food and beverage products, and many other industrial process fluids with a minimum electrical conductivity.

Electromagnetic flowmeters are widely used wherever reliable, maintenance-free flow measurement is required. Because they have no moving parts and no flow obstructions in the measuring tube, EMFs are particularly suitable for abrasive, corrosive or solids-containing media. In addition, their pressure loss is negligible, making them an energy-efficient solution for many process applications.

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What are typical applications for magmeters?

With available nominal diameters ranging from DN2.5 to DN3000 / ¹⁄₁₀…120”, electromagnetic flowmeters cover one of the widest size ranges of any industrial flowmeter technology. They are therefore suitable for applications ranging from precise dosing and batching to high-volume water distribution and large pipeline installations.

Typical areas of application are:

  • Water & wastewater industry: potable water, abstraction and irrigation water, sea water, municipal and industrial wastewater, etc.

  • Oil & gas: Produced water, chemicals

  • Chemicals: highly aggressive, corrosive, toxic liquids

  • Food & beverage: hygienic applications, e.g. dosing of milk and cream, filling of soft drinks, beer, etc.

  • Pharma: single-use biopharmaceutical applications

  • Minerals & mining: Mine water, brine or abrasive tailings and concentrate slurries with a very high solid content

  • Marine industry: dredging, ballast water

  • Pulp & paper industry: paper pulp, black liquor and bleach

  • Data Centers: Cooling applications

  • OEM: Batching and filling systems for liquids from beverages to cement

  • Special applications:

    • 0D/0D installations without inlet/outlet runs

    • Liquids with very low conductivity and sticky media

    • Safety Integrated Systems

    • Master metering

    • Custody transfer and fiscal metering

Electromagnetic flowmeters applications KROHNE

How does an electromagnetic flowmeter work?

An electromagnetic flowmeter (EMF), also known as a magmeter or magnetic flowmeter, measures the volumetric flow rate of electrically conductive liquids using Faraday's Law of Electromagnetic Induction. This law states that an electrical voltage is induced when a conductor moves through a magnetic field.

In an electromagnetic flowmeter, the process liquid itself acts as the conductor. As it flows through the insulated measuring tube, coils generate a magnetic field perpendicular to the direction of flow. When the conductive liquid passes through this magnetic field, a voltage is induced between two measuring electrodes mounted opposite each other in the flow tube.

The induced voltage (U) is directly proportional to the average flow velocity (v̄) of the liquid. The flowmeter therefore first determines the flow velocity and then calculates the volumetric flow rate from the pipe's internal cross-sectional area. Because the measuring principle depends only on the movement and electrical conductivity of the liquid, the measurement is largely independent of pressure, temperature, density and viscosity.

What are the advantages of an electromagnetic flowmeter (EMF)?

Electromagnetic flowmeters offer several advantages over other flow measurement technologies when measuring electrically conductive liquids. Their robust measuring principle and obstruction-free design make them a preferred choice for a wide range of industrial applications.

Key advantages include:

  • High measurement accuracy andexcellent repeatability for reliable process control

  • Wide measuring range (turndown ratio up to 1000:1), enabling accurate measurement from low to high flow rates

  • Full-bore measuring tube with no moving or protruding parts, eliminating mechanical wear

  • Virtually no additional pressure loss, helping to reduce pumping energy and operating costs

  • Low maintenance requirements due to the wear-free measuring principle

  • Suitable for clean, contaminated, abrasive and corrosive conductive liquids, including slurries and wastewater

  • Measurement largely independent of viscosity, density, pressure, temperature and Reynolds number, ensuring stable performance under changing process conditions

  • Wide choice of liner and electrode materials, allowing the flowmeter to be tailored to demanding chemical, hygienic or abrasive applications

  • Available in nominal diameters from DN2.5 to DN3000 / ¹⁄₁₀…120", covering applications from dosing lines to large transmission pipelines

  • Reliable long-term performance with high operational availability and long service life

What are the most widely used magmeter designs?

Electromagnetic flowmeters are available in several designs to suit different installation requirements, pipe sizes and applications. The choice of magmeter depends on factors such as the process medium, available installation space, power supply and required measurement performance.

The most common electromagnetic flowmeter designs include:

  • Full-bore inline electromagnetic flowmeters – the industry standard for accurate and reliable flow measurement of conductive liquids. With a full-diameter measuring tube and typically two measuring electrodes, they are suitable for a wide range of process and utility applications.

  • Reduced-bore electromagnetic flowmeters – primarily used in water distribution networks. The reduced measuring tube increases the flow velocity through the sensor, providing a significantly higher measurement accuracy over a wide flow range without the need for straight inlet or outlet runs.

  • Battery-powered electromagnetic flowmeters – designed for remote installations without access to mains power, such as district metering areas (DMAs), irrigation systems and water distribution networks.

  • Electromagnetic flowmeters for partially filled pipes – developed for gravity lines in wastewater, sewer and drainage applications where pipelines are not completely full.

  • Insertion electromagnetic flowmeters – a cost-effective solution for large-diameter pipelines where installing a full-bore meter would be impractical or uneconomical. They are commonly used for retrofit projects and large water transmission lines.

Large diameter EMF
WATERFLUX 3050 without straight inlet and outlet runs
WATERFLUX with GPRS module KGA 42 in aboveground part of the pipeline
TIDALFLUX application picture
OPTIPROBE 1100 installed in a DN1200 river water line

Which materials are electromagnetic flowmeters available in?

Electromagnetic flowmeters are available with a wide range of liner and electrode materials to ensure optimum performance, chemical resistance and long service life across different applications.

The liner material is selected according to the process medium and operating conditions:

  • Drinking water: Approved polymer, polypropylene or rubber liners that comply with national and international drinking water regulations.

  • Food and beverage: Stainless steel measuring tubes and food-grade liners that meet requirements such as EC1935/2004 andFDA regulations.

  • Chemical processing: High-performance liner materials, including ceramic measuring tubes for highly aggressive or toxic media requiring maximum chemical resistance and leak integrity.

  • Wastewater, mining and slurries: Hard or soft rubber liners for abrasive media. For extremely demanding applications such as dredging and mining, KROHNE also offers ceramic tile liners with exceptional wear resistance.

Options for electronics range from Hastelloy® for many standard industrial applications to tantalum, platinum and cermet for highlycorrosive media. Forabrasive slurries, wear-resistant electrodes made from conductive rubber or tungsten carbide provide enhanced durability and signal stability.

For particularly challenging applications, KROHNE also offers non-wetted capacitive electrodes, as used in the OPTIFLUX 7300, enabling reliable flow measurement of very low-conductivity, highly adhesive media, including fats and similar products.

How can flow disturbances be minimised for accurate electromagnetic flow measurement?

Magmeter installation recommendation 5DN-2DN

To achieve the specified measurement accuracy, conventional full-bore electromagnetic flowmeters should be installed in accordance with the manufacturer's recommendations. The common industry standard is to provide straight inlet runs of 5 × DN upstream and straight outlet runs of 2 × DN downstream, measured from the centre of the flowmeter. This allows flow disturbances caused by pipe bends, valves or pumps to dissipate, resulting in a stable, fully developed flow profile at the measuring point. These installation recommendations help achieve optimum measurement performance and support compliance with applicable industry standards and guidelines, such as ISO 4064 for water meters.

Flow straightener

Where sufficient straight pipe runs are not available, flow conditioners (flow straighteners) or suitable pipe reducers can help improve the flow profile before the liquid enters the flowmeter. Alternatively, specialised electromagnetic flowmeter designs are available that are less sensitive to disturbed flow profiles and can operate accurately with little or no straight inlet and outlet runs.

Can electromagnetic flowmeters be used without straight inlet and outlet runs?

Yes. While conventional full-bore electromagnetic flowmeters (EMF) typically require straight inlet and outlet runs to achieve their specified accuracy, some designs are engineered to deliver accurate measurement even under disturbed flow conditions.

For applications with limited installation space, KROHNE offers certified full-bore EMFs that have been tested and calibrated for operation under various flow profile conditions, including custody transfer applications. Their measurement performance has been verified by independent notified bodies in accordance with applicable industry standards.

For applications where no straight inlet or outlet runs (0D/0D) are available, KROHNE'sWATERFLUX flowmeters use a different measuring concept. Their rectangular reduced-bore measuring tube accelerates the flow and produces a stable, nearly symmetrical flow profile before the measuring electrodes. This design eliminates the influence of upstream flow disturbances, enabling highly accurate and repeatable measurement even in confined installation conditions and at very low flow rates.

An alternative approach is the use of multi-electrode electromagnetic flowmeters, which compensate for asymmetric flow profiles by evaluating signals from several electrodes. While effective in certain applications, these designs are generally more complex and costly. The higher number of electrodes also increases the number of potential leak paths. Compared with flow-profile-optimised electromagnetic flowmeters, they achieve lower measurement accuracy under disturbed flow conditions.

OPTIFLUX 0D-0D test installation

The benefits of the WATERFLUX design

Compared with conventional electromagnetic flowmeters featuring a full-bore measuring design, the WATERFLUX comes particularly close to the physical ideal of Faraday’s law of induction thanks to its unique measuring tube geometry. For optimum measurement performance, the streamlines should intersect the magnetic field lines as close to perpendicular as possible, i.e. at an angle of 90°. The deliberate reduction and rectangular design of the measuring tube cross-section specifically supports this condition.

The flow is not merely guided by the geometry of the measuring tube; it is deliberately conditioned by physical means. The resulting flow profile is stabilised so that, in the area of the measuring electrodes, the flow lines run largely perpendicular to the magnetic field lines. This favourable flow condition is maintained across a large part of the measuring cross-section, including the areas close to the tube walls. With conventional measuring tubes with a circular cross-section, achieving this optimum geometric alignment between the flow profile and the magnetic field is considerably more difficult due to the different geometry.

Another key advantage of the reduced measuring tube geometry is its energy efficiency. The smaller effective measuring cross-section allows the magnetic coils to be positioned closer together. As a result, the magnetic field required for measurement can be generated with significantly less energy than in a conventional measuring tube with the same nominal diameter and a circular cross-section.

As a result, the WATERFLUX requires significantly less energy to generate the magnetic field and therefore operates with particularly high energy efficiency. This advantage is especially relevant for battery-powered flowmeters: the reduced energy consumption enables significantly longer battery life and, consequently, longer maintenance and service intervals.

Does WATERFLUX cause pressure loss?

A common question about flow-optimised electromagnetic flowmeters such as WATERFLUX is whether the reduced measuring section causes significant pressure loss and increases pumping energy requirements.

In practice, the permanent pressure loss is very low. At typical flow velocities of around 3 m/s in drinking water and cooling water applications, the pressure loss at maximum flow typically remains below 50 mbar, even for larger meter sizes. Its impact on the overall efficiency of a water distribution system and the required pumping energy is therefore negligible.

The reason is the hydraulic design of the measuring tube. The reduced cross-section temporarily increases the flow velocity through the measuring section, while part of the resulting kinetic energy is recovered downstream as static pressure. This minimises the permanent pressure loss of the flowmeter.

As a result, WATERFLUX combines the advantages of a flow-profile-optimised measurement with low energy consumption, making it particularly suitable for water distribution applications where reliable measurement and energy efficiency are important.

Can electromagnetic flowmeters be used in SIL applications?

Icon/Logo Security Integrity Level 2/3 (SIL 2/3)

Yes. Electromagnetic flowmeters can be used in Safety Instrumented Systems (SIS) when they are designed, assessed and certified according to IEC 61508, the international standard for functional safety.

The OPTIFLUX 4400 electromagnetic flowmeter, for example, is certified for use in safety-related applications up to Safety Integrity Level (SIL) 2/3, depending on the system architecture. It supports reliable process monitoring in applications where flow measurement is part of a safety function.

Advanced diagnostic functions help increase plant availability and simplify proof testing. They enable automated partial proof testing of the OPTIFLUX 4400, allowing for extended intervals between full proof tests to increase plant uptime in safety instrumented systems (SIS). The magmeter also features a best-in-class diagnostic test interval and a fault response time of only 2 minutes. If operating outside its specified limits, the flowmeter can issue an alarm to the control room significantly faster than comparable electromagnetic flowmeters on the market.

By combining SIL certification with comprehensive diagnostics, electromagnetic flowmeters can support both functional safety and efficient plant operation in demanding process applications.

Can water flowmeters also be used for sewage?

Wastewater flow measurement

The suitability of an electromagnetic flowmeter (EMF) depends on its design, the materials selected for the liner and electrodes, as well as industry- and country-specific approvals and certifications. However, conditions in sewage applications are often significantly more demanding.

Depending on its composition, sewage can be chemically aggressive and may also have abrasive properties due to the presence of suspended solids and other solid particles. Not every electromagnetic flowmeter designed for water applications is therefore suitable for these conditions in terms of its liner and wetted materials.

As flammable gases such as H₂S can form in sewage applications, the relevant explosion protection requirements must be considered when the flowmeter is used in hazardous areas. Sewage flowmeters are therefore generally designed and configurable so that the electronics and sensor can meet the applicable regional explosion protection requirements.

For a flowmeter specifically designed for potable water applications, such as the WATERFLUX, the sensor's flow cross-section is optimised for drinking water applications. Its design offers significant advantages over conventional electromagnetic flowmeters in this respect. Such a flowmeter can also be used for treated wastewater, for example at the outlet of a wastewater treatment plant. However, it is not suitable for wastewater containing significant amounts of solids or for raw sewage, as the flow-optimised pipe cross-section may limit cleaning by pigging.

In addition, it should be noted that flow in a partially filled, gravity-fed wastewater pipeline cannot be reliably measured even with a conventional EMF designed for wastewater applications. This is the case, for example, in a sewer or when controlling the discharge from a storm overflow basin. Specialised sewage flowmeters such as the TIDALFLUX 2300 are required for this purpose. The TIDALFLUX 2300 was developed for flow measurement in partially filled wastewater pipelines and sewers.

Can electromagnetic flowmeters measure in partially filled pipes?

Conventional electromagnetic flowmeters require the measuring tube to be completely filled with liquid. This can be a challenge in gravity pipelines, sewage channels and wastewater systems, where the flow is often not under pressure and pipes may only be partially filled.

A common solution is to install a sluice underpass to create full-pipe conditions. However, these installations increase construction costs, require regular cleaning to prevent blockages and add maintenance effort.

For these applications, KROHNE developed the TIDALFLUX 2300, a specialised electromagnetic flowmeter for partially filled pipes and free-flowing wastewater applications. Its integratedcapacitive level measurement determines the filling level of the pipe, enabling accurate flow measurement even when the measuring tube is not completely full.

The TIDALFLUX 2300 is therefore ideally suited for applications such as sewage channels, wastewater treatment plant inlets and outlets, and other gravity-fed drainage systems where conventional electromagnetic flowmeters cannot be used.

TIDALFLUX - Capacitive level measurement and other benefits

The particular advantage of capacitive level measurement is that the level measuring elements are installed behind the measuring tube liner and therefore do not come into contact with the medium. This reliably protects them from the corrosive effects of the medium. This is particularly important for wastewater measurement in sewers: in partially filled sewers, biological processes can generate hydrogen sulphide (H₂S), which can attack and corrode exposed metallic electrodes and other wetted components. Since the TIDALFLUX performs capacitive level measurement entirely behind the liner, there is no direct contact with the medium.

Another advantage is the TIDALFLUX’s extensive factory calibration. The measuring system is calibrated at the factory for different conductivities, filling levels and flow conditions. This ensures precise flow measurement across the entire relevant filling range, starting at a filling level of 10%.

With alternative measuring systems, extensive on-site calibration is often required to adapt the measuring system to the specific local flow and installation conditions. Depending on the system, regular inspections, maintenance or readjustments may also be necessary. With the TIDALFLUX, these time-consuming adjustments are largely eliminated. This makes the system particularly straightforward to install and operate, while also keeping maintenance requirements low.

Can EMFs also be installed underground?

OPTIFLUX 2300 W with special burial coating

Magmeters are ideally suited for buried installation, where they offer a cost-effective alternative to costly and time-consuming flowmeter chambers and manholes in water distribution networks. However, operators need to pay close attention to the appropriate flowmeter specification to protect the installation against corrosion and water ingress.

KROHNE can provide its flowmeters with a special factory-applied coating for buried installation. The coating is designed to protect the meter housing against corrosion for 20 years or more. In addition, flowmeters designed for buried installation feature fully potted electronics housed in a robust stainless steel connection box. Rated IP68 or NEMA 6P, the electronics housing provides additional protection against water ingress and potential damage to the flowmeter.

Does an EMF need grounding?

Yes. Correct grounding of an electromagnetic flowmeter is essential for both electrical safety and measurement accuracy. Like all electrical equipment, magmeters must be installed in accordance with applicable safety requirements to ensure protective earthing and potential equalisation.

Grounding is also critical for the measuring principle. Electromagnetic flowmeters detect very small induced voltages, typically in the millivolt range. To measure these signals reliably, the flow converter requires a stable electrical reference potential that corresponds to the potential of the process liquid.

The required grounding method depends on the pipe material and installation conditions. In conductive pipelines, grounding is usually achieved through the pipe itself. For non-conductive pipes, such as plastic pipelines, grounding rings or grounding electrodes are commonly used to provide the necessary reference potential.

KROHNE's Virtual Reference offers an alternative by eliminating the need for grounding rings or grounding electrodes in many applications. This simplifies installation, reduces costs and avoids additional wetted components, making it particularly suitable for water and industrial applications with large diameter pipes and challenging process conditions.

Diagram of classical and virtual grounding

Which process connections are available for electromagnetic flowmeters?

Electromagnetic flowmeters applications flange connection KROHNE

Electromagnetic flowmeters are available with a wide range of process connections to suit different industries, installation requirements and pressure ratings.

Common options include flanged connections in accordance with standards such as DIN, ASME and JIS, threaded connections, as well as hygienic connections such as clamp connections and ferrules for applications in the food, beverage and pharmaceutical industries. For demanding high-pressure applications, specialised connections such as hub and clamp systems are also available.

For space-constrained installations, flangeless electromagnetic flowmeters in wafer or sandwich design can be installed directly between existing pipe flanges, reducing installation space and weight.

What diagnostics are available for electromagnetic flowmeters?

Modern electromagnetic flowmeters are much more than flow measurement devices. They continuously monitor process and device conditions and provide diagnostic information to assess measurement reliability, meter health and process conditions.

KROHNE's OPTIFLUX and WATERFLUX flowmeters, for example, perform various device and application diagnostics, including tests of measurement accuracy and linearity. An out-of-specification test can be performed online at regular intervals to determine whether the flowmeter remains within its specified performance. The test uses an internal test signal to check the measurement accuracy, while the linearity of the measuring system and the accuracy of the magnetic field current are also monitored.

Typical electromagnetic flowmeter diagnostics include monitoring for:

  • Electrode corrosion or deposits

  • Short circuits

  • Low conductivity of the process medium

  • Partial filling of the measuring tube

  • Liner damage

  • External magnetic interference

  • Disturbed flow conditions

OPTICHECK technology built-in tech icon

OPTICHECK technology built-in

Latest-generation KROHNE electromagnetic flowmeters with integrated OPTICHECK technology (OPTICHECK technology built-in) provide approximately 80 device and application diagnostics, supporting reliable measurement and early detection of process or device-related problems. Diagnostic data can be accessed and configured via the flowmeter's communication and operating interfaces.

Tech icon MPO

Multi-Phase Operation (MPO)

KROHNE's MPO (Multi-Phase Operation) functionality combines advanced diagnostics with optimised signal processing. It enables electromagnetic flowmeters to maintain stable measurement even under severe process conditions, such as gas entrainment, high solids concentrations or electromagnetic disturbances, where conventional magmeters may experience measurement issues.

Diagnostic functions also support on-site verification of electromagnetic flowmeters. Depending on the device and configuration, verification can be performed without interrupting the process, including wirelessly via Bluetooth® or remotely using a DTM from the control room.

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