Magnetic Flowmeters Used in Industry

Magnetic Flow Meter
Magnetic flow meter.
Magnetic flow meters are effective for monitoring the flow rate of fluids that present difficult handling problems, such as corrosive acids, sewage, rock and acid slurries, sand and water slurries, paper pulp stock, rosin size, detergents, bleaches, dyes, emulsions, tomato pulp, milk, soda, and beer. Magnetic flow meters mainly are applicable to liquids that have a conductivity of 0.1 microsiemens per centimeter or greater. They are not applicable to petroleum products or gases.

Measurement Principal

The basis of the magnetic flow meter is Faraday's Law of Electromagnetic Induction. In summary, a voltage induced in a conductor (i.e., the fluid flowing in the conduit) moving in a magnetic field is proportional to the velocity of the conductor. This relationship can be expressed mathematically as follows:
internal view magmeter
Internal view of flow tube.


E = induced voltage
C = constant
B = magnetic flux density
D = diameter of conduit
v = velocity of fluid

In principle, the fluid flowing through the pipe passes through the magnetic field. This action generates a voltage that is linearly proportional to the average velocity in the plane of the electrodes. If the velocity profile changes due to swirl or helical flow patterns, the total measured velocity is unaffected as long as the velocity profile across the pipe is symmetrical. Non-symmetrical flow profiles may cause flow rate measurement errors of several percent.

In operation, the magnetic coils create a magnetic field that passes through the flow tube and into the process fluid. When the conductive fluid flows through the flow meter, a voltage is induced between the electrodes, which are in contact with the process fluid and isolated electrically from the pipe walls by a nonconductive liner to prevent a short circuit in the electrode signal voltage. Grounding is required for magnetic flow meters to shield the relatively low voltage signal that is measured at the electrodes from the relatively high common-mode potentials that may be present in the fluid. If the pipe is conductive and comes in contact with the flow meter, the flow meter should be grounded to the pipe both upstream and downstream of the flow meter. If the pipe is constructed of a nonconductive material, such as plastic, or a conductive material that is insulated from the process fluid, such as plastic-lined steel pipe, grounding rings should be installed in contact with the liquid.

Magnetic flow meters can be used in pipes that range in diameter from 0.25 to 240 cm (0.1 to 96 in.). Magnetic flow meters are available for flow rates in the range of 0.008 liters per minute (L/min) (0.002 gallons per minute [gal/min]) to 570,000 L/min (150,000 gal/min). Since magnetic flow meters do not place an obstruction in the pipe, the devices do not cause a loss in fluid pressure. Also, straight pipe requirements do not apply to this flow monitor device. Magnetic flow meters are insensitive to density and viscosity and can measure flow in both directions. In addition, because they cause no obstructions, magnetic flow meters often are used to measure the flow rate of slurries.


If all components of a magnetic flow metering system are calibrated as a unit, system accuracies of ±0.5 percent of flow rate are possible. However, normal accuracy specifications are ±1.0 percent of flow rate. Higher accuracy systems match the primary flow meter with a transmitter in the factory.

For more information on magnetic flow meters, contact TECO by calling 800-528-8997 or visit their web site at

Hydraulic Fracturing Terms and Definitions

Hydraulic Fracturing Terms and DefinitionsHydraulic fracturing is the process of using fluid, sand, chemicals, and gels to create or exploit small fractures in a sub-surface rock layer formations in order to stimulate production from oil and gas wells. This fracturing creates paths and reservoirs which increase the rate at which fluids can be taken from the wells. In some cases, this process can increase production by many hundreds of percent.

Below are common terms and definitions* used in the hydraulic fracturing process:
  • Additive Pumps – used to inject liquid additives; different types based on the additive type and additive rate.
  • Annulus – Area between two concentric casing strings or tubular strings.
  • Bottom Hole Treating Pressure (psi) – pressure being applied to the formation including net pressure.
  • Centrifugal Pumps – used on the low pressure equipment to mix and move fluid.
  • Clean Volume (gal or bbl) – volume of fluid pumped without proppant.
  • Dirty Volume (gal or bbl) – volume of fluid pumped with proppant.
  • Flowmeter – used to measure and transmit fluid flow rates; different types depending on application.
  • Frac Gradient (psi/ft) – pressure at which fluid will cause the formation rock to part.
  • High Pressure Pumps – Positive displacement pumps used for pumping downhole.
  • Hydraulic Horsepower (hhp) – horsepower being applied to the formation while pumping .
  • Hydrostatic Pressure (psi) – pressure the fluid column exerts on the formation.
  • Instantaneous Shut-in Pressure (psi) – a pressure used to calibrate the frac gradient.
  • Kick-outs – mechanical or electrical devices that activate at a preset pressure to disengage high pressure pumps.
  • Liquid Additive (gal/Mgal) – any liquid chemical added to the fluid system for a specific purpose
  • Max Pressure (psi) – the maximum WHTP that will be allowed.
  • Net Pressure (psi) – excess pressure over frac pressure required to extend the fracture .
  • Perf Friction Pressure (psi) – pressure drop across the perforations.
  • Pipe Friction Pressure (psi) – friction pressure of the fluid being pumped down the wellbore.
  • Pop-off – a mechanical device activates at a preset pressure to prevent damage to surface and downhole tubular.
  • Pressure Transducer – device used to measure and transmit pressure data.
  • Proppant – small diameter material used to keep the fracture open.
  • Proppant Concentration (lb/gal) – the amount of proppant added to one gal of fluid.
  • Shut-in Pressure (psi) – a pressure used to calibrate the frac gradient.
  • Solid Additive (lb/Mgal) – a solid chemical added to the fluid system for a specific purpose.
  • Treatment Rate (bpm) – the downhole rate that fluid is entering the formation pumping.
  • Wellhead Treating Pressure (psi) – the surface pressure at the wellhead during.
Thompson Equipment (TECO) manufactures highly engineered flowmeters designed for optimum performance in fracing applications. Contact TECO to discuss any severe flow measurement application.


* from workshop titled "Fracture Design and Stimulation – Monitoring" (DC01:570405.2)

The Role of the High and Low Pressure Ports on a Differential Pressure Transmitter

It's easy to misunderstand the role of the high and low pressure port on differential pressure transmitters. This video clearly explains their real meaning and role.

Thermo Scientific Ramsey

Thermo Scientific Ramsey manufactures industrial in-motion weighing, monitoring and inspection equipment used for process control and production control in a wide variety of industrial applications. Products include weighbelt feeders, belt scales, metal detectors, sampling systems, level indicators, conveyor safety switches. Below is an embedded copy of the Thermo Scientific / Ramsey Bulk Weighing and Monitoring Catalog. You can download a copy at the TECO website here.

Electromagnetic Flow Metering

Electromagnetic flow meters
Cutaways of electromagnetic flow meters - one
removed from service (right) and one
remanufactured (left).
Electromagnetic flow metering is widely used for conductive liquids, such as water acids and alkalis. It's also effective in many other process applications using clean, dirty, and process liquids and slurries. While electromagnetic flow metering is primarily used in full pipes, they can also be applied to partially full pipes and channels often found in effluent applications.

Electromagnetic flow metering is based on the principles of Michael Faraday's 1832 discovery. When a conductive liquid, such as water, is moved through a magnetic field a voltage is induced in the liquid at right angles to the magnetic field. The size of the voltage is directly proportional to the volume flow rate. This induced voltage is detected by sensors known as electrodes. These electrodes transfer the voltage signal to the processing electronics where it can be converted into a usable industrial standard signal.

It's important that the flow meter tube is non-magnetic, and austenitic stainless steel is the most commonly used material. It's also essential that the flow meter tube has a lining that electrically insulates it from the liquid inside, and provides a non-reactive barrier with any corrosive liquids being measured. Distinguishing between flow induced voltage changes, electrochemical noise, and plant induced noise, is a barrier to accurate electromagnetic flow metering. This can be particularly difficult in dirty and industrial applications. The choice of electromagnetic flowmeters with advanced noise suppression can mitigate unwanted noise and provide extremely high orders of accuracy as a result.

To ensure that your electromagnetic flow meters will be optimized for safety, longevity, and performance, the advice of a qualified flow instrumentation expert should be sought out. That expert will be able to help you with the best selection of the appropriate flow device for your specific application, be it electromagnetic flow meters or another flow technology.

Differential Pressure Flow Metering for the Chemical Processing Industry White Paper

Differential Pressure Flow MeteringFlow measurement is a critical aspect of plant operation in the Chemical Processing Industry (CPI). Users choosing equipment to meter the flow of liquid or gas processes must consider a wide range of factors to arrive at an optimal solution Experience has shown there are significant differences between meter technologies, with each type of device having its own advantages and disadvantages for processing facilities

Common Differential Flow Metering Methods:
  • Venturi
  • Cone Meter
  • Wedge Meter
  • Averaging Pitot Tube
In modern chemical plants, personnel need to make faster and better decisions by capturing, managing and analyzing the right data at the right time These facilities rely heavily on flow processes, and thus accurate and reliable measurement techniques are vital to the efficiency and safety of their operations.

Badger Meter, a premier manufacturer of industrial flow meters, has authored an excellent white paper explaining the use of differential pressure flow metering in the chemical processing industry. You can get the white paper at this link.

For more information, visit Thompson Equipment Company (TECO) at or call 800-528-8997 for immediate service.

Remanufactured Flowmeters, Instrumentation & Valves

TECO has the experience, trained technicians, and facilities to remanufacture your equipment to meet or exceed all OEM specifications and performance standards. Send us your old flowmeter, process instrument, or valve and we'll send it back to you as good as new.

Thompson Equipment Company