A Simple and Reliable Measurement Solution
Electromagnetic water counters widen the municipal water market.
Over the past decades, a wide variety of mechanical bulk water flowmeters have been developed, using turbine rotors and positive displacement designs. Until recently, the technology used to meter the distribution of municipal water has been mature and relatively slow to change. In fact, the most prevalent method of measurement, the turbine flowmeter, is based on the 18th century design of Reinhard Woltman and has been commercially available for more than 100 years.
However, all such mechanical devices have inherent shortcomings because they contain moving parts that require periodic testing, recalibration, and repair, and because they contain components that protrude into the measuring path, drawing kinetic energy from the fluid and impeding flow. To mitigate these problems, ancillary piping and equipment is often required, such as filters/strainers and firefighting hydrant bypasses, adding significantly to installation and maintenance costs.
Manufacturers of mechanical flowmeters have used their expertise in brass casting, mechanical design, fluid dynamics, and precision machining to incrementally improve mechanical meters, but they have not been able to overcome the fundamental shortcomings. Unfortunately, no technically and financially viable alternative to mechanical meters has been available, until the recent introduction of battery-powered electromagnetic water counters that are specifically designed for drinking water networks, well-connecting chambers, and sprinkler irrigation systems.
Electromagnetic Water Counters These new “magmeters” are designed to have all the advantages of mechanical flowmeters—namely, simplicity of operation—without the disadvantages of a mechanical device. The fundamental benefit of electromagnetic water counters is that they are extremely simple and reliable. They have no moving parts and nothing protrudes into the smooth, measuring tube. Water simply flows through a magnetic field, thereby generating a voltage proportional to flow that is sensed by two side-mounted stainless steel electrodes. This signal is then fed to an electronic converter and finally displayed as volume and flow rate.
The electromagnetic water “counters” are streamlined versions of the more sophisticated electromagnetic flowmeters that have been widely used for nearly 50 years in some of the most demanding industrial processing and custody-transfer applications. The chemical, paper, and mining industries use magmeters because of their ability to provide highly accurate flow measurement of difficult fluids despite turbulent flow and the presence of bubbles, suspended solids, and abrasive material.
Water distribution applications require a much simpler, and lower-cost, meter. Service workers in the field need to be able to read and maintain meters and repair them when necessary. The importance of simple construction and operation is evident at the annual Meter Madness competition at the American Water Works Association, where water utility employees from across the country compete to assemble a mechanical water meter from a bucket of parts. The winning time is usually less than 30 seconds, and the contestants can seemingly do the job with their eyes closed!
Newly designed electromagnetic water counters are even simpler than their mechanical counterparts. No maintenance is required, except to replace the batteries every 10 years or so, a process as easy as replacing the batteries of a flashlight. The display has the same look and feel as a conventional water meter register, with an LCD readout replicating the appearance of the classic mechanical odometer. Unlike traditional magmeters used for industrial applications, there is nothing to program and no user interface to learn.
 |
Photo: Krohne |
| Magmeters provide higher performance and reliability at a lower price. |
10-Year Battery Life Previously, the most important factor inhibiting the deployment of electromagnetic bulk water meters was the electrical power requirements. Unlike mechanical meters, which are powered by the water flow, magmeters require an electrical power source. For most applications, the geographic location of the site makes connecting the meter to the power grid too expensive and complex. DC-powered devices have been available, but until recently, battery life was limited to three to five years, an unacceptably short interval.
Two developments have occurred that have resolved concerns about battery power. First of all, automated meter reading, already widespread in the electricity sector, has grown among water utilities and irrigation systems, as water is increasingly being viewed as a scarce and costly resource that needs to be tracked more carefully. In contrast to the longstanding resistance to mixing water and electricity, today battery-powered automatic meter reading (AMR) transmitters are commonly connected to mechanical water meter registers.
The second development is the significant extension of battery life. A breakthrough came in 2005, when Krohne developed the Waterflux electromagnetic bulk water meter with a battery life of 10 years, at a high sampling rate. Krohne is a worldwide technological leader in the development, manufacture, and distribution of accurate, reliable, and cost-effective measurement instruments for the process industries.
Now an electromagnetic water meter is finally available that has a longer battery life than most, if not all, AMR devices. (For the Waterflux, an optional integrated AMR transmitter uses a separate battery.) The new magmeter technology reduces electricity consumption by 99.98% compared to conventional electromagnetic flowmeters. Krohne accomplished this feat with a patented technology that sends electrical current through coils in opposite directions.
Lower Cost of Ownership The paradox of the electronic age is that solid-state technological innovations that replace mechanical approaches can often provide better performance and higher reliability, and they can do so at a better price. The simplicity and elegance of the electromagnetic water counter gives this new technology a price advantage, which rises with increasing nominal diameter.
The purchase price of the meter is only one factor in evaluating the total cost of ownership. Maintenance costs are reduced and installation is simplified. There is no need to purchase, install, and maintain filters and strainers. Because magmeters do not cause any pressure drop, it is no longer necessary for commercial installations to install expensive bypass systems for firefighting hydrants.
Moreover, magmeters are easier to install in pits and tight locations, because they require much shorter straight runs upstream from the meter, at only three diameters, compared to 10 to 25 diameters of straight runs required by turbine meters. Magmeters obviate the need for any radial vane elements or other external flow straighteners.
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Magmeters also have a number of additional advantages, including the ability to measure bi-directional flow and the ability to continually perform self-diagnosis and automatically report improper functioning, as well as to send alarms when high flow might indicate leakage in the distribution system.
Future Outlook
Mechanical water meters are not going away. Water utilities will continue to rely on mechanical meters, especially for 1-inch- and smaller-diameter installations. But electromagnetic flowmeters now provide a good option for medium- and high-volume water customers, irrigation systems, and problematic applications, such as water with suspended particles.
Author's Bio: Hans Windgassen is the senior product manager for the EMF instrument range of Krohne and has experience in the flow and level measurement applications worldwide.
March-April 2007
A Simple and Reliable Measurement Solution
Electromagnetic water counters widen the municipal water market.
Over the past decades, a wide variety of mechanical bulk water flowmeters have been developed, using turbine rotors and positive displacement designs. Until recently, the technology used to meter the distribution of municipal water has been mature and relatively slow to change. In fact, the most prevalent method of measurement, the turbine flowmeter, is based on the 18th century design of Reinhard Woltman and has been commercially available for more than 100 years.
However, all such mechanical devices have inherent shortcomings because they contain moving parts that require periodic testing, recalibration, and repair, and because they contain components that protrude into the measuring path, drawing kinetic energy from the fluid and impeding flow. To mitigate these problems, ancillary piping and equipment is often required, such as filters/strainers and firefighting hydrant bypasses, adding significantly to installation and maintenance costs.
Manufacturers of mechanical flowmeters have used their expertise in brass casting, mechanical design, fluid dynamics, and precision machining to incrementally improve mechanical meters, but they have not been able to overcome the fundamental shortcomings. Unfortunately, no technically and financially viable alternative to mechanical meters has been available, until the recent introduction of battery-powered electromagnetic water counters that are specifically designed for drinking water networks, well-connecting chambers, and sprinkler irrigation systems.
Electromagnetic Water Counters These new “magmeters” are designed to have all the advantages of mechanical flowmeters—namely, simplicity of operation—without the disadvantages of a mechanical device. The fundamental benefit of electromagnetic water counters is that they are extremely simple and reliable. They have no moving parts and nothing protrudes into the smooth, measuring tube. Water simply flows through a magnetic field, thereby generating a voltage proportional to flow that is sensed by two side-mounted stainless steel electrodes. This signal is then fed to an electronic converter and finally displayed as volume and flow rate.
The electromagnetic water “counters” are streamlined versions of the more sophisticated electromagnetic flowmeters that have been widely used for nearly 50 years in some of the most demanding industrial processing and custody-transfer applications. The chemical, paper, and mining industries use magmeters because of their ability to provide highly accurate flow measurement of difficult fluids despite turbulent flow and the presence of bubbles, suspended solids, and abrasive material.
Water distribution applications require a much simpler, and lower-cost, meter. Service workers in the field need to be able to read and maintain meters and repair them when necessary. The importance of simple construction and operation is evident at the annual Meter Madness competition at the American Water Works Association, where water utility employees from across the country compete to assemble a mechanical water meter from a bucket of parts. The winning time is usually less than 30 seconds, and the contestants can seemingly do the job with their eyes closed!
Newly designed electromagnetic water counters are even simpler than their mechanical counterparts. No maintenance is required, except to replace the batteries every 10 years or so, a process as easy as replacing the batteries of a flashlight. The display has the same look and feel as a conventional water meter register, with an LCD readout replicating the appearance of the classic mechanical odometer. Unlike traditional magmeters used for industrial applications, there is nothing to program and no user interface to learn.
|
Photo: Krohne |
| Magmeters provide higher performance and reliability at a lower price. |
10-Year Battery Life Previously, the most important factor inhibiting the deployment of electromagnetic bulk water meters was the electrical power requirements. Unlike mechanical meters, which are powered by the water flow, magmeters require an electrical power source. For most applications, the geographic location of the site makes connecting the meter to the power grid too expensive and complex. DC-powered devices have been available, but until recently, battery life was limited to three to five years, an unacceptably short interval.
Two developments have occurred that have resolved concerns about battery power. First of all, automated meter reading, already widespread in the electricity sector, has grown among water utilities and irrigation systems, as water is increasingly being viewed as a scarce and costly resource that needs to be tracked more carefully. In contrast to the longstanding resistance to mixing water and electricity, today battery-powered automatic meter reading (AMR) transmitters are commonly connected to mechanical water meter registers.
The second development is the significant extension of battery life. A breakthrough came in 2005, when Krohne developed the Waterflux electromagnetic bulk water meter with a battery life of 10 years, at a high sampling rate. Krohne is a worldwide technological leader in the development, manufacture, and distribution of accurate, reliable, and cost-effective measurement instruments for the process industries.
Now an electromagnetic water meter is finally available that has a longer battery life than most, if not all, AMR devices. (For the Waterflux, an optional integrated AMR transmitter uses a separate battery.) The new magmeter technology reduces electricity consumption by 99.98% compared to conventional electromagnetic flowmeters. Krohne accomplished this feat with a patented technology that sends electrical current through coils in opposite directions.
Lower Cost of Ownership The paradox of the electronic age is that solid-state technological innovations that replace mechanical approaches can often provide better performance and higher reliability, and they can do so at a better price. The simplicity and elegance of the electromagnetic water counter gives this new technology a price advantage, which rises with increasing nominal diameter.
The purchase price of the meter is only one factor in evaluating the total cost of ownership. Maintenance costs are reduced and installation is simplified. There is no need to purchase, install, and maintain filters and strainers. Because magmeters do not cause any pressure drop, it is no longer necessary for commercial installations to install expensive bypass systems for firefighting hydrants.
Moreover, magmeters are easier to install in pits and tight locations, because they require much shorter straight runs upstream from the meter, at only three diameters, compared to 10 to 25 diameters of straight runs required by turbine meters. Magmeters obviate the need for any radial vane elements or other external flow straighteners.
Magmeters also have a number of additional advantages, including the ability to measure bi-directional flow and the ability to continually perform self-diagnosis and automatically report improper functioning, as well as to send alarms when high flow might indicate leakage in the distribution system.
Future Outlook
Mechanical water meters are not going away. Water utilities will continue to rely on mechanical meters, especially for 1-inch- and smaller-diameter installations. But electromagnetic flowmeters now provide a good option for medium- and high-volume water customers, irrigation systems, and problematic applications, such as water with suspended particles.