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Mechanical water meters have been used to measure water flow for over 100 years. They are standard equipment in drinking water networks, well connecting chambers and sprinkler irrigation systems. Their advantages and disadvantages are well known, and operators and authorities have adapted accordingly.

However, flow metering technology has advanced considerably. The new WATERFLUX electromagnetic water meter offered by KROHNE Messtechnik in Duisburg is an impressive example of this progress. The new water meter has all the advantages of mechanical water meters, but also features an elegant solution for traditionally problematic applications, such as water with suspended particles, bi-directional metering, as well as measuring flow in pipes with sizes of DN 50 – 300 and larger.

The WATERFLUX electromagnetic flowmeter was developed by KROHNE Messtechnik, which has been manufacturing electromagnetic flowmeters since 1962. Today the company builds 60,000 meters annually, with diameters ranging from 2.5 to 3000 mm. They are applied in the water and wastewater, chemicals and pharmaceuticals and food & beverage industries, as well as for measuring everything from the flow of coal and ore sludge in mines right through to cooling water measurements in nuclear power stations. An electromagnetic flowmeter operates simply and reliably. It has no moving parts and nothing that protrudes into the 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 flange-to-flange dimensions conform to ISO 13359. The wetted parts liner is made of KTW-compliant PPE, which is approved by DVGW's Code of Practice W 270*. The smooth conical shape of the measuring path enables the flow profile to be optimized, which results in the following advantages:

1. reduced mineral deposits
2. improved flow readability, particularly when consumption is low
3. a straight supply and return path, only 5/2 D
4. ability to measure without filters and rectifiers
5. bi-directional flow measurement capability
6. no restrictions on installation (vertical / horizontal / diagonal).

The WATERFLUX electromagnetic water meter is available as a compact device, where the sensor and electronic converter are combined as a single unit, or the converter can be supplied separately, in which case it connects to the sensor via a cable. The latter configuration is useful in special applications such as underground or submersed installations. Both versions are available to comply with either IP67 (intermittent submersion), or IP68 (continuous submersion). In the latter configuration, the cable connections have additional sealing to prevent water entering the meter if a cable is damaged. Added security features include electronic password protection and provision for sealing to prevent unauthorized manipulation.

Batteries

Since the device is an electromagnetic instead of mechanical water meter, it requires electric power. In most applications, the geographic location of the site makes connecting to the power grid too expensive and complex. The WATERFLUX meter, a specially engineered flowmeter in the electromagnetic flowmeter category, enables accurate measurements to be taken even though the electrical energy it consumes is a factor of 5000 less than that of conventional electromagnetic flowmeters. The WATERFLUX meter sets new standards with its high sampling rate and battery life of at least ten years.

Diagnosis

WATERFLUX features not only accurate flow measurement, but also continuous diagnostics in accordance with applicable standards such as OIML R 49, EN 14154, ISO 4064 and MI-001. This self-diagnosis monitors and automatically reports improper functioning of the electronics, or faulty sensor electrodes.

Battery charge status is also indicated, and even open circuit conditions are reported. This is useful if the sensor is wired to a remote converter and an excavator damages the cable.

Directives

WATERFLUX is primarily designed for "business dealings" applications as specified by European Directive MI-001, which will be ratified and come into force in 2006. The measuring accuracy is in accordance with the most recent ISO / EN and MI-001 standards. The ratio is 400 between Q1 and Q3, based on quasi-continuous flow measurement (1/5Hz). The resulting theoretical increase in measuring uncertainty is only + 0.138 %. Although battery life could be extended by reducing the flow sampling rate to 1/15 Hertz, corresponding to one measurement every 15 seconds, this option is not provided since it would result in increasing measuring uncertainty by + 0.41 % in applications where the flow rate is subject to rapid increases or decreases or where there are large fluctuations in flow. There would also be a risk of hydraulic manipulation.

Important also is that electromagnetic meters feature far superior long-term stability and are less sensitive to pressure drops than conventional mechanical water meters, thanks mainly to their unencumbered measuring path.

Telemetry

A standard feature is the local display that indicates flow in m3 and m3/h. However, it will soon be outdated, because these water meters are installed in very remote shafts or well connecting chambers. A state-of-the-art telemetry system is available for such applications, consisting of a data logger and GSM transmitter. It can be supplied as a compact module installed directly in the WATERFLUX, or in a separate wall-mount housing. The data logger stores all flow data, including peak values and low flow rates during nighttime operation. The data is transmitted via SMS or GPRS to the nearest public transmission tower, for example, once per day. From there it goes to an internet or cellular phone network server. WATERFLUX + TELEMETRY can thus be used anywhere in the world and it can also be accessed using the internet or a cell phone anywhere in the world. The telemetry system is fed from a separate battery.

Cost-of-Ownership

Of course, a final important attribute of these electromagnetic WATERFLUX water meters with a size of DN 50 to DN 600 is price. The situation here is the same as for clocks. Nowadays, mechanical clocks are technically inferior to electronic clocks and are also more expensive. They will soon only have value for collectors. The same applies when comparing WATERFLUX with mechanical water meters. The EMF meter has decisive advantages, particularly with increasing size. Elimination of filters, rectifiers and cleaning intervals required in some applications and elimination of duplicate systems for measuring bi-directional flow are added cost benefits.

As you can see, the new electromagnetic WATERFLUX water meter offers a number of technical and commercial advantages. Food for thought.

SOURCE: KROHNE, Inc.

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