Exploring Different Types of Flow Meters
by Team Kritsnam

Flow measurement is a fundamental and crucial control parameter in many industries. Some critical processes require an accurate quantity of water to ensure the quality of output, hence such industries need to monitor flows and keep them within safe limits. Further, with depleting water resources, it is also essential to keep a track of water consumption. To ensure the above conditions, industries need to install flow meters to accurately measure the water flow.  Flowmeters can also assist in other applications such as storage management, plant-wide process management, leak detection, and estimation, pump and pump-efficiency management, etc. Precise measurements in the industry are vital in conserving water that fulfills the goals of sustainable development. Sustainable development is a path that can be continued indefinitely due to its social, economic, and environmental benefits. Economically feasible is the summit of the pyramid since it is vital in an industrial setting. Sustainable development in an industry works only if the company can still make a profit.

Having different types of flowmeters available in the market, before installing a water flow meter into a pipe, it is essential to understand the differences between these flowmeters and the benefits they provide. Based on the physical quantities of volume and mass, flow meters used in closed conduit flow are classified as volumetric flow meters and mass flowmeters. Volumetric flow meters are used to determine the volume of fluid flowing through a conduit at a specific point in time. Some examples include Electromagnetic flowmeters, Ultrasonic flowmeters, Turbine flow meters, vortex flow meters, and Positive displacement meters. Mass flow meters, on the other hand, calculate the rate of fluid mass flow through a conduit per unit of time. A Coriolis mass flowmeter and a Thermal mass flowmeter are two examples. The mentioned flowmeters, performance efficiency, and maintenance cost depend on the adoption of invasive and intrusive technology.

Electromagnetic flowmeter:

how a magnetic flow meter works

Electromagnetic flowmeters are sometimes known as magnetic flowmeters. It is based on Faraday's Law of Electromagnetic Induction. According to Faraday's Law, when a liquid flows through a magnetic field, it generates voltage. As the fluid flows faster, more voltage is generated. The voltage generated is proportional to the movement of the water, and electronics transform the voltage signal into the volumetric flow rate. Magnetic flowmeters use a magnetic field to measure the speed of a fluid passing through a conduit to determine the volumetric flow.

Electromagnetic flow meters are nonintrusive because they do not obstruct the flow path and have no moving parts. Bidirectional flow can be measured using electromagnetics. Because of the wide range of lining materials available, the meter can be used for virtually any liquid, including corrosive fluids. The liner provides insulation as well as corrosion and abrasion protection. Electromagnetic flow meters are used in slurry applications due to the abrasion resistance of the liner. Density and viscosity do not affect the electromagnetic flow meter.

Electromagnetic flow meters are relatively heavy, particularly in larger sizes. Electromagnetic flow meters are a little pricey. To avoid the problem of entrapped air in horizontal installations, the electrodes should be located on the horizontal diameter at the point of greatest induction. It is not suitable for very low fluid velocity because accuracy suffers as a result. Electromagnetic flow meters have limitations in their use for fluids with magnetic properties (liquid with suspended metal).

Electromagnetic flow meters are ideal for practically any liquid with low conductivity. Except for gases and petroleum chemicals with limited electrical conductivity, they are acceptable for practically all industrial fluids. They're widely utilized in pulp and paper mills, wastewater treatment plants, and non-Newtonian fluid flow measurements. Electromagnetic flow meters cannot work on pure water because there are no ions to measure.

Vortex flowmeter:

Vortex flowmeters work on the vortex shedding concept, which states that when a fluid, such as water, flows through a bluff (rather than a streamlined) body, oscillating vortexes form. The frequency at which vortexes are shed is determined by the body's size and shape.

Vortex Flow Meter

Vortex flow meters have several characteristics that set them apart from other fluid flow measurement meters. Flow measurement of liquids, steam, and gases with high accuracy; Flow measurement of conductive and nonconductive fluids is possible. There are no moving parts, so there is less wear.

High-viscosity fluids are incompatible with vortex and swirl meters. Vortex/swirl meters cannot measure zero flow. Not suitable for batch processing or many other types of control applications; Not suitable for low-density fluid at low velocity. Only in a Reynolds number band is operation possible (for swirl meters this band is wider on the lower side).

These meters are used in almost every major industry. Utility/power plants, chemical plants, oil and gas, and pharmaceuticals are just a few examples.

Ultrasonic flowmeter:

An ultrasonic flow meter is a meter that uses ultrasound to assess liquid velocity to calculate the amount of liquid flow. An ultrasonic flow meter can be built by combining upstream and downstream transducers, a sensor pipe, and a reflector. The ultrasonic flow meter works by using sound waves to determine the velocity of a liquid within a pipe. Radar, Doppler velocity, ultrasonic clamp-on, and ultrasonic level ultrasonic flow meters are all available on the market.

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Doppler velocity type meters use reproduced ultrasonic noise to calculate the liquid’s velocity. Radar meters use microwave technology to broadcast tiny pulses that reflect off a moving surface and back to the sensor to determine velocity. A clamp-on ultrasonic meter is suited for applications where access to the pipe is difficult or impossible. An ultrasonic level meter is suited for measuring fluid levels in both open and closed channels.

Because of its non-invasive nature and lack of moving parts, this type of flow meter has some unique characteristics, such as being relatively inexpensive for large pipe applications, having no pressure loss, and being simple to retrofit.  Appropriate for large-diameter pipes. Large size is an advantage for USFMs because it takes longer to traverse the beam, resulting in better measurements. Furthermore, because of its non-invasive nature, it is less expensive as line sizes increase. Many other meters, such as mass flow meters, cannot do this; Clamped types are completely non-invasive and nonintrusive.

It, like a magnetic flow meter, can be used for almost any fluid, including corrosive fluids, because it is non-invasive. USFM can measure liquids in the absence of conductivity. USFM can measure steam, gas, and liquids in addition to transit time. Slurry flow can be measured using Doppler effect meters, which typically cover a wide range of velocities. Meters are generally highly repeatable and reliable, with good accuracy; unlike a vortex meter, the USFM has no lower limit for Reynolds number. As a result, low flow can be measured more accurately than with vortex meters. Furthermore, with a sufficient number of transducer pairs, the issue of transitioning from a laminar to a turbulent profile can be resolved. Ultrasonic gas flow meters are not affected by pressure, flow strokes or vibration dirt in gas. As a result, they find use in situations where other methods fail to measure.

The fluid in transit type meters must be clean and free of foreign matter. If other materials are present and their densities differ, measurement errors may occur. Lower limits for solid concentration and size, as well as fluid velocity, are set in Doppler effect flow meters. The fluid must be acoustically transparent. The presence of dirt or gas in the fluid may impair measurement accuracy. Acoustic noise, even above the level of human perception, can have an impact on measurement accuracy.

Because USFMs require less maintenance, they will continue to provide a constant reading for as long as the transducers are operational. Even if they fail, they may be simply changed with new ones without interrupting the process.

Turbine flow meters:

A turbine Flow Meter is a form of volumetric measuring turbine. The flowing fluid engages the rotor, forcing it to revolve at an angular velocity proportionate to the rate of fluid flow. The angular motion of the rotor causes an electrical signal (AC sine wave type) to be generated in the pickup. The sum of the pulsating electrical signal is closely connected to total flow. The frequency of the signal is proportional to the flow rate. The flow meter's only moving component is the vaned rotor.

Turbine flow meters are less accurate at low flow rates due to rotor/bearing drag, which causes the rotor to slow down. Turbine flow meters should not be operated at high speeds because they can cause premature bearing wear and/or damage. Application in unclean fluids should be avoided in general to limit the risk of flowmeter wear and bearing damage. Turbine flow meters have moving parts that degrade through time and use.

Turbine flow meters have a high level of precision at a cheap cost. These are easy to install and have less maintenance. Turbine meters may function across a wide temperature and pressure range. In Turbine flow meters, constant back pressure is required to prevent cavitation. The presence of bubbles in liquids harms accuracy.

Turbine meters may only be used with clean liquids and gases, not suitable for measuring corrosive fluids. It requires a turbulent flow profile (constant fluid velocity across the pipe diameter) for accuracy. Require a straight pipe run before and after the turbine meter to allow swirl patterns in the flow stream to disperse. It may not function effectively with high viscosity fluids where the flow profile is laminar

Positive displacement meters:

Positive displacement meters are also called mechanical flow meters. They take the fluid amount, transport it quickly, and then refill it. The amount of fluid that has been transported has been computed. Various flow meters measure other factors and convert them to a flow rate, whereas positive displacement flow meters monitor the actual flow of fluid. The output of these flow meters is proportional to the volume of fluid passing through the flow meter. A Positive displacement flow meter can be compared to a stopwatch and a bucket. When the flow starts, the stopwatch starts. It comes to a halt when the buckets are full. Divide the volume by the time to get the flow rate. To acquire a continuous PD measurement, a system must fill and empty buckets regularly, then divide the flow without allowing it to depart the pipe. Pistons responding in cylinders or gear teeth coupling against the interior wall of the meter reflect these constantly forming and subsiding volumetric displacements.

Oval gear meters, piston meters, rotary vane meters, spinning disc meters, and other positive displacement meters are examples.

Positive displacement flow meters have a high level of precision. Viscous liquids are also measured with positive displacement flow meters. They're commonly utilized to transfer fluids or oils such as hydraulic fluids, gasoline, water, and a variety of gas applications.

Coriolis mass flowmeter:

Coriolis Principle

Coriolis meters, more generally referred to as mass meters, are distinguished from other meter types by their ability to measure mass flow rather than volume flow. Additionally, these meters have a novel method of measuring flow rate based on the Coriolis principle. A Coriolis meter is called after the Coriolis Effect. When a mass passes through a vibrating pipe, bending or twisting the pipe, Coriolis forces exist. These minute deviations in the meter tube are monitored and assessed electrically using strategically placed sensors. The mass flow rate through the Coriolis mass flowmeter may be directly calculated since the phase shift between the sensor signals detected is proportional to the mass flow rate.

Density, temperature, viscosity, pressure, and conductivity do not affect this method of measuring. The meter tubes vibrate at the same frequency indefinitely. These flowmeters affect the resonance frequency. These provide exact information about the density of the medium under investigation. To summarise, the Coriolis mass flowmeter can be used to simultaneously measure the mass flow rate, density, and temperature of a measuring medium.

Coriolis mass flowmeter is extremely precise. It gives accurate density measurements. It is insensitive to pressure, temperature, and viscosity. It can be operated over a broad variety of flow rates. It is compatible with a wide variety of fluids. Calibration is simple in the field. Its initial investment is quite high.

Thermal mass flowmeter:

Thermal mass flow meters are precision instruments that measure gas mass flow directly for industrial gases, compressed gases, and other gases. This necessitates extra pressure and temperature observations to calculate the mass flow rate. These remedial actions increase the cost and complexity of the measurements, as well as the accuracy of the measuring equipment. In contrast, the thermal mass flow measurement for gases directly delivers the mass flow rate in kg/h without any extra observations or calculations.

Hot film anemometers and calorimetric or capillary meters are the two industrial technologies for measuring thermal gas mass flow rate.

The pressure drop is very low in this flow meter. Measurement accuracy is high. No moving parts in this flowmeter.

Choosing the Best Water Flow Meter for You:

When attempting to choose the best water flow meter, there are numerous aspects to consider, which include: The meter's accuracy; How long the meter is expected to survive; The operational and maintenance requirements; The flow rate range that the meter can handle.

If accuracy in a flow meter is critical for your application, you'll almost certainly need to invest in a more expensive water flow meter. The device's lifespan is likewise proportional to its entire cost. Regardless of which water flow meter you select, being able to identify the flow rate of your water could prevent significant problems with the plumbing in your facility.

References:

  1. F. Frenzel, H. Grothey, C. Habersetzer, M. Hiatt, W. Hogrefe, M. Kirchner, G. Lütkepohl, W. Marchewka, U. Mecke, M. Ohm, F. Otto, K.-H. Rackebrandt, D. Sievert, A. Thöne, H.-J. Wegener, F. Buhl, C. Koch, L. Deppe, E. Horlebein, A. Schüssler, U. Pohl, B. Jung, H. Lawrence, F. Lohrengel, G. Rasche, S. Pagano, A. Kaiser, T. Mutongo, Industrial Flow Measurement Basics and Practice, ABB Automation Products GmbH, 2011. http://nfogm.no/wpcontent/uploads/2015/04/Industrial-Flow-Measurement_Basics-and-Practice.pdf.
  2. General Specifications; Model DY Vortex Flowmeter Model DYA Vortex Flow Converter; YEL; GS 01F06A00e01EN; Digital YEWFLO. http://web-material3.yokogawa.com/ GS01F06A00-01EN.pdf.
  3. Process Master FEP300, Electromagnetic Flow Meter, ABB limited, Data sheet DS/FEP300-EN Rev. F. http://www.navitrend.com.tw/images/FEP%20300%20Data%20Sheet.pdf.
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