Learn More About Water Flow Meters – What are They and How do ...

Article | May 25, .
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From agriculture, to manufacturing, to the oil and gas sector, and beyond, flow meter(th,tr,uz)s play a vital role in ensuring safe, reliable operations of critical liquid and gas infrastructure. You must be able to measure what’s flowing where on a continuous basis. That’s why flow meters are an essential tool across a variety of industries today.

By delivering accurate, continuous visibility into flow rates - flow meters ensure that agencies and businesses have the information they need to maintain smooth operations and meet regulatory requirements.

Below, we explain how flow meters work, what types of flow meters are available, and how to select the best flow meter for your needs.

What is a Flow Meter?

A flow meter is a device that measures how much liquid or gas moves through a pipeline in a given period of time.

By measuring flow rates, flow meters provide crucial visibility into what’s flowing where, within pipes, drainage systems, and other types of infrastructure. In turn, they help operators determine whether systems are properly balanced, ensure that each endpoint receives adequate supply, identify excessive flow rates that could damage pipes, and so on.

What is a Water Flow Meter?

A water flow meter is a flow meter designed to measure the flow of water specifically, as opposed to other types of liquids (like oil or gasoline) or gases.

Water flow meters can be used to track the flow of water within a variety of applications. They can:

• Measure usageby individual households or communities within municipal drinking water systems.
• Track sewage flowto help municipalities ensure that their wastewater systems adequately meet demand.
• Help factory operatorsassess the amount of water being used to cool an industrial plant.

5 Types of Flow Meters and How They Work

All flow meters perform the same basic job: They measure flow by tracking how much liquid or gas moves through a fixture in a given period of time. However, several different types of flow meters exist, each of which uses a different approach for tracking flow.

Electromagnetic Flow Meters

Electromagnetic flow meters, sometimes called magnetic meters or mag meters, use electrodes to measure water flow. The electrodes, which are embedded on opposite sides of the surface through which liquid flows, create a magnetic field. By sensing the voltage generated by water as it passes through the magnetic field, electromagnetic flow meters can track flow rates with a high degree of accuracy.

Electromagnetic flow meters are generally low maintenance, because they have no mechanical parts that can break down. In addition, because there are no components directly in the path of the water, electromagnetic meters don’t impede water as it passes through. That means there is no degradation in flow during the measurement process.

Differential Pressure Flow Meters

A differential pressure flow meter forces water through a constriction of some type, such as an orifice or nozzle, and measures the water pressure on both sides of the constriction. A high pressure drop indicates high water flow.

The obvious downside of this type of flow meter is that it reduces pressure and can slow down water flow, causing permanent pressure loss. These kinds of flow meters are undesirable in applications that require maximum pressure throughout the system.

Mechanical (Turbine) or Propeller Flow Meters

Mechanical flow meters force liquid through a physical component that moves when the water pushes on it. The most common type of mechanical flow meter uses a propeller for this purpose. By measuring how fast the propeller or other mechanical component turns, this type of flow meter can record flow rates with a high degree of accuracy.

Because this type of meter contains mechanical parts that can wear down over time, however, mechanical flow meters require a relatively high degree of maintenance. Operators have to replace bearings and ensure that the propeller remains properly aligned in order to achieve accurate readings.

Ultrasonic Flow Meters

An ultrasonic flow meter uses ultrasonic waves to measure how fast liquid is traveling. By injecting waves into the liquid and listening for a response, this type of meter can assess flow rates almost instantaneously.

Because ultrasonic meters have few mechanical parts, they are a low-maintenance flow meter solution. However, because sound travels at very different velocities between different materials, even small amounts of contaminants (like dirt or air bubbles) can cause ultrasonic flow meters to produce readings that are less accurate than those of electromagnetic readers.

Vortex Flow Meters

Using a principle called the von Kármán effect, vortex flow meters measure water flow by tracking the differential pressure created by an obstacle in the path of the liquid. Changes in differential pressure create a vortex, hence the name of this type of meter.

While vortex flow meters don’t have mechanical parts and therefore require little maintenance, their readings are not highly accurate, especially at low flow rates.

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Why Accurate Flow Meters Are Important

The degree of accuracy that an organization requires from a flow meter may vary. In general, however, the more accurate the flow meter, the more valuable it is to the business or agency.

That’s true across a variety of industries, all of which require accurate flow readings to ensure smooth business operations:

• Agriculture: In applications like agricultural irrigation, too much flow can flood a crop, leading to rot and a wasted harvest. Too little, which starves plants of water, is just as dangerous. Accurate flow meters remove the guesswork to ensure healthy, productive fields.
• Wastewater: Accurately measuring the flow of sewage and other types of wastewater is essential for preventing clogs, especially in systems where wastewater includes sludge as well as liquid effluent.
• Drinking water: Potable water systems require accurate flow measurements to ensure that the right amount of water reaches each branch and building on the system, even as water consumption rates vary across the systems.
• Cooling water: In settings like factories and data centers, cooling water plays a vital role in preventing equipment from overheating—but it only does so if cooling systems deliver just the right volume of water, which requires accurate flow meter readings.
• Industry: Industrial processes often require a variety of liquids, such as water, steam, and gas. Accurate flow meters ensure that businesses have the right volume and pressure of these materials to keep the plant floor humming smoothly.
• Oil and gas: To manage production and ensure adequate energy supply across large networks, the oil and gas industry must accurately measure flows, even when materials aren’t pure or when liquids travel very long distances.

How to Choose the Best Flow Meter

Given the varying levels of accuracy and degrees of maintenance required from different types of flow meters, choosing the best flow meter for your application can be challenging.

Here’s what to consider when evaluating your options:

1. Understand the Process
2. Consider the Media Being Measured
3. Determine Accuracy, Range, and Certification Requirements
4. Inspect the Meter Location and Installation Needs
5. Decide What Type of Output is Needed
6. Consult with a Technical Partner

• Read our full article and details of the Top 6 Factors to Consider When Selecting a Flow Meter

Flow meters are instruments that monitor, measure or record the flow rate, volume or mass of a gas or liquid. You may also know them as flow gauges, flow indicators, liquid meters or flow rate sensors. Flow meters provide accurate monitoring and/or control of what moves through a pipe or pipeline, including water, air, steam, oil, gases and other liquids.

Application-specific flow meters allow facility managers, control contractors, consulting engineers and other stakeholders to:

• Understand and monitor flow operations
• Identify and improve efficiencies
• Address equipment issues and wasteful behavior

Having access to this accurate, timely and dependable flow data and control is essential for product quality, safer operations, cost control and regulatory compliance.

Different Types of Flow Meters

Flow measurement technologies are used across a variety of sectors—from building design and construction to oil and gas, water and wastewater and chemical and petrochemical processing. These industries rely on flow meters to help maintain smooth operations, meet regulatory standards, support energy and resource conservation and gain deeper insight into system performance. A wide range of flow meter types are available to suit different applications and environments including:

How Do Flow Meters Work?

From measuring velocity to detecting pressure changes, flow meters use a variety of methods to calculate the movement of liquids and gases. Here’s a look at how each meter type functions and what makes it best suited for certain applications.

Ultrasonic Meters

Ultrasonic meters measure the velocity of a fluid flowing through a pipe. The two types of ultrasonic flow technologies include Doppler and transit time. Doppler technology measures the difference in sound wave frequency reflected off gas bubbles or particles in the flow stream. It’s suitable for aerated or dirty liquids. Transit time technology measures the time differential between signals sent upstream and downstream. The differential is directly proportional to the velocity of the water.

Ultrasonic meters are often selected for their exceptional accuracy, minimal maintenance and low cost of ownership. Ultrasonic meters are available in inline, open-channel and clamp-on models, with clamp-on solutions offering a non-intrusive option when contact with the measured fluid is not possible.

Coriolis Meters

Coriolis meters measure mass flow and density through inertia. This unobstructed, open-flow meter identifies flow rate by directly measuring fluid mass over a wide range of temperatures with a high degree of accuracy. As fluid flows through the sensor tubes, forces induced by the mass flow cause the tubes to twist, which is proportional to the mass. Coriolis meters are recognized for their impressive accuracy, ease of installation and ability to measure both mass flow and density.

Electromagnetic Meters

Electromagnetic meters, also known as magnetic flow meters or mag meters, operate under Faraday’s Law of Electromagnetic Induction to measure liquid velocity. The law states that a conductor moving through a magnetic field produces an electrical signal within the conductor, which is directly proportional to the velocity of the water moving through the field. As fluid flows through the magnetic field, conductive particles in the fluid create changes in voltage across the magnetic field. This measures and calculates the velocity of water flow through the pipe.

Because electromagnetic meters have no moving parts, they are an ideal option for wastewater applications or any dirty liquid that is conductive or water-based. Benefits of electromagnetic meters include minimal maintenance, wide turndowns and compatibility with corrosive chemicals as well as an ability to meet sanitary requirements for food applications.

Differential Pressure (DP) Meters

Differential pressure meters measure the flow of liquid within a pipe by introducing a constriction that creates a pressure drop. Pressure sensors measure the pressure before and after the constriction. The resulting pressure drop that occurs across the constriction is relative to the square of the flow rate; a higher pressure drop equals a higher flow rate.

Differential pressure meters are suitable for applications including across filters, heat exchangers, backflow preventers, pipelines, ducts and more. One key reason why facility managers choose DP meters is because there are no moving parts, which means minimal maintenance.

Positive Displacement (PD) Meters

Positive displacement meters measure the volumetric flow rate of a liquid or gas passing through the meter by repeatedly entrapping it with rotating parts, which measure the volume. Specific types of positive displacement meters include oscillating pistons (OP), nutating discs, industrial gear and others. These meters are often selected for their high accuracy, excellent repeatability and wide turndown ratios.

Vortex Meters

Vortex meters use a principle called the von Kármán effect to measure liquids, gases and vapors. Vortex meters measure by placing an obstruction (called a shredder bar) in the flow path, which creates vortices of alternating differential pressure. These vortices cause a small sensor device to oscillate with a frequency directly proportional to the velocity of the moving fluid. The sensing element then converts the oscillation rate into an electrical signal, which is converted into a quantifiable velocity reading. Vortex meters are a common choice for their wide rangeability, repeatability and accuracy in measuring liquids, gases and saturated steam.

Turbine Meters

Turbine meters use the mechanical energy of a liquid to rotate a rotor in the flow stream. The rotational speed of the rotor is directly proportional to the velocity of the fluid traveling through the meter. Turbine meters reliably measure the velocity of liquids, gases and vapors, and are often selected for these key benefits: durable meter structure, high accuracy range at a low cost and notable repeatability under a wide range of temperatures and pressures.

Variable Area Meters

Variable area meters measure the volumetric flow of liquids and gases. An orifice is positioned within the piston assembly and forms an annular opening with the contoured metering cone. The piston assembly carries a cylindrical ceramic magnet that is coupled to an external flow indicator that moves precisely in direct response to the piston movement. A calibrated spring opposes flow in the forward direction, decreasing viscosity sensitivity. Key benefits of variable area meters include that they are low cost, simple to operate and maintain and require no electronics to obtain a reading.

Finding the Right Flow Meter Solutions

With the wide array of flow meter solutions available, we understand it can be tricky to determine which is best for your unique application. Our flow measurement solutions serve many industries. If you’re searching for a flow instrumentation solution that improves sustainability and inefficiencies, reduces maintenance or replaces an aging system, reach out to our experts. We understand that cost, downtime and maintenance are all of concern when it comes to finding a new flow meter solution. We’ll listen to your unique application requirements and goals and make a recommendation that best fits, so you can keep your operations running and focus on other priorities.