Showing posts with label magnetic flow meter. Show all posts
Showing posts with label magnetic flow meter. Show all posts

Understanding How Magnetic Flowmeters Work and the Difference between AC and DC Excitation


The electromagnetic flowmeter, commonly known as the "magmeter", gets its name from the magnetic field generated within the float tube that produces a signal proportional to flow. This principle employs Faraday's Law of Electromagnetic Induction. Magnetic flowmeters are built so the direction of the magnetic field is perpendicular to the flow and the line between the electrodes is also perpendicular to the flow. As a conductive liquid flows through the flowtube, an electro-motive force is generated. The electrodes detect the electro-motive force. The electro-motive force is proportional to the flow velocity, flux density, and the meter inner diameter. The flux density of the magnetic field and the meters inner diameter are constant values, therefore the magnetic flow meter can calculate the flow velocity and volumetric flow from the electro-motive force.

The basic components of the magnetic flow meter body are:

  1. A lined flowtube (typically Teflon)
  2. Excitation coils
  3. Two electrodes mounted opposite of each other within the flowtube.

Current is applied to the coils in the magmeter to generate a magnetic field within the flow tube. As a conductive fluid flows through the meter, an electro-motive force is generated. This force is detected by the electrodes and the resulting value is converted to flowrate.

For more information on magnetic flowmeters, contact Miller Energy, Inc. by calling 800-631-5454 or by visiting https://millerenergy.com.

Magnetic Flow Meters

magnetic flowmeter flow meter on large flanged lined pipe section
Magnetic flow meters can be easily applied in lined
pipe sections and those of substantial diameter.
Image courtesy Yokogawa
The measurement of fluid flow is a common process control function. Flow measurement can have a range of differing output requirements, depending upon the needs of the process operators. With many technologies and instruments from which to choose, knowledge of the principals behind each measurement technology and basic operation requirements can help in the selection of the best instrument for each application. 

Anywhere there are pipes, somebody wants to know how much fluid is passing through them. Industrial flow meters rely on their ability to measure the change in some physical characteristic of fluid moving within a pipe that can be related to fluid velocity or mass flow. Depending upon the nature of the raw measurement, additional information and processing may be necessary to convert the base measurement into a useful measurement of flow rate.

In the processing industries, differing technologies are used to measure fluid motion. Some common technologies include magnetic, ultrasonic, vortex shedding, Coriolis and differential pressure. This list is not exhaustive, and several other technologies will certainly be found in use. Each methodology survives within a competitive marketplace due to its unique combination of performance and value attributes. Let's look at magnetic flow meters, also referred to as magmeters.

The operational principle of a magnetic flow meter is based upon Faraday’s Law. This fundamental scientific principle states that a voltage will be induced across a conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure aspect of a conductive fluid to be expressed via the magmeter. In a magmeter application, the instrument produces the magnetic field referred to in Faraday’s Law. The conductor, moving at a right angle to the magnetic field, is the fluid. The actual measurement of a magnetic flow meter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with values of other fluid properties and the pipe cross sectional area. Magnetic flow meters enjoy some positive application attributes.
  • Magnetic flow meters have no moving parts.
  • The instrument, which often resembles a pipe section, can be lined with corrosion resistant material for use with aggressive media.
  • With no sensor insertions or obstructions in the fluid path, the impact of the instrument on the flow is minimal.
  • Accuracy, when compared to other technologies, is high.
  • Application to laminar, turbulent, and transitional flow profiles is permissible.
  • Generally, measurement is not adversely impacted by fluid viscosity, specific gravity, temperature and pressure.
  • Magnetic flow meter technology can be applied to a very wide range of pipe sizes.
  • Device responds rapidly to changes in fluid flow.
  • Can be successfully applied to liquids containing heavy particulates.
  • Generally long service life with little maintenance.
Though the roster of positive attributes is strong, magmeters are not universally applied. Consider some of these points with respect to your potential application.
  • The fluid acts as the "conductor", as stated in Faraday's Law. Magnetic flow meters only work on liquids with conductivity above a certain threshold. They may be unsuitable for use with hydrocarbons and high purity water for this reason.
  • Cannot be used to measure gas flow because gases are not sufficiently conductive.
  • Piping must be grounded.
  • Generally, rated accuracy requires the pipe cross section to be filled by the liquid being measured.
This listing of attributes is very general in nature. Some magnetic flow meter variants have adaptations that minimize or accommodate the impact of special process conditions. Share your flow measurement requirements and challenges with a process measurement specialist. Your own knowledge and experience will be leveraged into an effective solution by their product application expertise.

Industrial Fluid Flow Measurement

Coriolis flow meter
Coriolis flow meters deliver a mass flow measurement
Image courtesy Yokogawa
Fluid flow measurement is commonly employed in many industrial process control operations. Accurate and useful flow measurement can be obtained with the proper application and installation of a flow meter as part of the fluid transfer system.

Industrial flow meters employ differing technologies to directly or indirectly measure gas and liquid flow rates. The selection of an appropriate measurement technology and instrument will be influenced by a number of factors related to the installation and application demands.

Among the many available technologies for fluid flow measurement, vortex flow meters, magnetic flow meters, Coriolis flow meters, and rotameters are among some of the most common found in industry.

Each of the separate technologies have attributes which can make them more suitable to certain applications. Selecting the most appropriate flow measurement technology for an application is one of the initial and crucial steps to designing a well functioning flow measurement system.
Selection criteria, such as fluid temperature, pressure, and velocity will be part of the selection process. Additional considerations include whether the fluid may be abrasive, corrosive, clean or dirty. The state of the fluid, liquid or gas, must also be considered. The desired output, whether volumetric or mass flow, will certainly be an integral part of the criteria.

Selecting the right measurement technology and instrument is not always an easy task, especially since it may be something that you do infrequently. Share your flow measurement challenges and requirements with process instrumentation specialists, leveraging your own knowledge and experience with their product application expertise to save time and develop an effective solution.

Smart Output™ Module For Water System Monitoring

magnetic flowmeter variants
Full bore flanged and insertion style magnetic flowmeters,
with Smart Output™ technology to enhance their functionality.
Image courtesy McCrometer 
Water distribution systems, though mostly invisible to the general public, are highly complex infrastructure arrangements that extend to a very large number of locations throughout a service area. Monitoring the activity and operational health of the distribution system, key to maintaining high levels of efficiency and service, requires measurement instrumentation installed throughout the system.

Magnetic flowmeters are an integral part of water system instrumentation. Their advantages for use in water systems were outlined in a previous article on how magnetic flowmeters work. McCrometer is an innovator in the design and manufacture of magnetic flowmeters for water system flow measurement. Their Smart Output™ technology is available for use with full bore flanged and insertion style flowmeters to provide the information needed for modern water system operation.

  • AC or DC powered versions
  • Compatible with Sensus and Itron smart water networks
  • Enables networking of water meters throughout distribution system
  • Queries, diagnostics, and data transfer can be scheduled or on demand
  • Enables AMR (Automatic Meter Reading) and AMI (Advanced Metering Infrastructure)
The Smart Output™ function is an additional module included as part of the instrument transmitter. 

More information is available from product application specialists, with whom you should share your flow measurement challenges of all types. Leverage your own process knowledge and experience with their product application expertise to develop effective solutions.

Maintenance Procedures - Yokogawa ADMAG TI Series AXW Magnetic Flowmeter

magnetic flow meter with corrosion resistant lining
The AXW series of magnetic flow meters is available in
a range of sizes with corrosion resistant lining.
Image courtesy Yokogawa
The ADMAG AXW™ series of magnetic flow meters has been developed based on Yokogawa's decades of experience in the design and manufacture of magnetic flowmeters. The AXW series continues the tradition of high quality and reliability that has become synonymous with the Yokogawa name.

The AXW series is ideal for industrial process lines, and water supply and sewage applications. With outstanding reliability and ease of operation, developed on decades of field-proven experience, the AXW will increase user benefits while reducing total cost of ownership.

Magnetic flow meters, also called electromagnetic flow meters or "magmeters", operate on a very simple principal. An electrically conductive liquid moving through a magnetic field will generate a voltage that is related to the velocity of the liquid. Magnetic flow meters have no moving parts and present little to no pressure drop to the piping system into which they are installed.

Sizes are available from 500 to 1800 mm (20 to 72 inch.) with a wide liner selection such as PTFE, natural hard rubber, natural soft rubber, and polyurethane rubber. The line accommodates industry standard process connections such as ASME, AWWA, EN, JIS, and AS flange standards. A submersible version is also available.

Care and maintenance for magnetic flow measurement devices is simple and minimal. The manual included below provides basic guidelines for maintenance procedures of ADMAG TI (Total Insight) Series AXW magnetic flowmeters. Share your flow measurement challenges with process instrument specialists, leveraging your own knowledge and experience with their product application expertise.


Magnetic Flowmeters: Principles and Applications

industrial process measurement instrument magnetic flow meter magmeter volumetric flow transmitter
Magnetic flowmeters are well suited for flow measurement
with conductive fluids.
Image courtesy Yokogawa
Fluid process control operations rely on the operator's ability to accurately determine qualities and quantities of liquid or gaseous materials. In terms of appraising and working with fluids (such as liquids, steam, and gases) the flowmeter is a staple tool, with the simple goal of expressing the delivery of a subject fluid in a quantified manner. Measurement of media flow velocity can be used, along with other inputs, to determine volumetric or mass flow. The magnetic flowmeter, also called a magmeter, is one of several technologies used to measure fluid flow.

In general, magnetic flowmeters are sturdy, reliable devices able to withstand hazardous environments while returning accurate measurements to operators of a wide variety of processes. The magnetic flowmeter has no moving parts. The operational principle of the device is powered by Faraday’s Law, a fundamental scientific principle stating that a voltage will be induced across any conductor moving at a right angle through a magnetic field, with the voltage being proportional to the velocity of the conductor. The principle allows for an inherently hard-to-measure quality of a substance to be expressed via the magmeter. In a magmeter application, the meter produces the magnetic field referred to in Faraday’s Law. The conductor is the fluid. The actual measurement of a magnetic flowmeter is the induced voltage corresponding to fluid velocity. This can be used to determine volumetric flow and mass flow when combined with other measurements.

The magnetic flowmeter technology is not impacted by temperature, pressure, or density of the subject fluid. It is however, necessary to fill the entire cross section of the pipe in order to derive useful volumetric flow measurements. Faraday’s Law relies on conductivity, so the fluid being measured has to be electrically conductive. Many hydrocarbons are not sufficiently conductive for a flow measurement using this method, nor are gases. On the other hand, water and aqueous solutions tend to exhibit sufficient conductivity to apply magmeter technology.

Magmeters apply Faraday’s law by using two charged magnetic coils; fluid passes through the magnetic field produced by the coils. A precise measurement of the voltage generated in the fluid will be proportional to fluid velocity. The relationship between voltage and flow is theoretically a linear expression, yet some outside factors may present barriers and complications in the interaction of the instrument with the subject fluid. These complications include a higher amount of voltage in the liquid being processed, and coupling issues between the signal circuit, power source, and/or connective leads of both an inductive and capacitive nature.

In addition to salient factors such as price, accuracy, ease of use, and the size-scale of the flowmeter in relation to the fluid system, there are multiple reasons why magmeters are the unit of choice for certain applications. They are resistant to corrosion, and can provide accurate measurement of dirty fluids – making them suitable for wastewater measurement. As mentioned, there are no moving parts in a magmeter, keeping maintenance to a minimum. Power requirements are also low. Instruments are available in a wide range of configurations, sizes, and construction materials to accommodate various process installation requirements.

As with all process measurement instruments, proper selection, configuration, and installation are the real keys to a successful project. Share your flow measurement challenges of all types with a process measurement specialist, combining your own process knowledge and experience with their product application expertise to develop an effective solution.

Magnetic Flow Meter – When Is It the Right Selection for Your Project?

Industrial Magnetic Flow Meter - Yokogawa
Industrial Magnetic Flow Meter
Courtesy Yokogawa Corp.
Flow measurement is a ubiquitous function in the industrial process control field. Anywhere there are pipes, somebody wants to know what, and how much, is passing through them. Fortunately for us engineers, there is a wide array of industrial flow meters capable of measuring some physical characteristic of fluid moving within a pipe that can be translated into a useful measurement of flow rate.

In industry, there are a number of different technologies used to measure a physical property related to fluid motion, referred to as magnetic, ultrasonic, vortex, Coriolis, differential pressure, and several others. Each methodology exists in the market because it may perform better or cost less when meeting certain performance requirements. This article is focused on magnetic flow meters and when they may be a good candidate for your project.

Here is a list of some of the positive attributes of magnetic flow meters.

  • Magnetic flow meters have no moving parts, always a plus.
  • General construction arrangement allows for use of an interior liner for corrosion resistance.
  • With no sensor insertions into the fluid flow, the impact of the instrument on the flow is minimized.
  • Accuracy, when compared to other technologies, is high.
  • Application to laminar, turbulent, and transitional flow profiles is permissible.
  • General insensitivity to fluid viscosity, specific gravity, temperature and pressure.
  • Magnetic flow meter technology can be applied to a very wide range of pipe sizes.
  • Device responds rapidly to changes in fluid flow.
  • Can be successfully applied to liquids containing heavy particulates.
  • Generally long service life with little maintenance.

There are, though, some points about magnetic flow meters which may make them unsuitable for your application.

  • Magnetic flow meters only work on liquids with conductivity above a certain threshold. They may be unsuitable for use with hydrocarbons and high purity water for this reason.
  • Cannot be used to measure gas flow.
  • Pipe must be grounded.
  • Typically, the pipe cross section must be filled by the fluid being measured.

This listing of positives and negatives is intended to be very general in nature. Some manufacturers may have product application solutions that overcome some of the negatives, while others may not be able to deliver all of the positives.

Your best course of action:

Use this general overview to start shaping you understanding of where magnetic flow meters may be a good option, and contact a product application specialist to discuss what you want to accomplish. Combining your process knowledge with their product knowledge should move you toward a good solution.