"Zero Maintenence" Equals 100% Satisfaction at Xcel Energy

When a pipeline carrying cooling water from Xcel Energyâs Bay Front, MN Plant needed to be more accurately monitored, research on flowmeters appropriate for this application led them to Marsh-McBirney. Excel Energy, the fourth largest combination electricity and gas energy company in the United States was formed by the merger of New Century Energies and Northern States Power. They provide energy related products and services to 3.3 million electricity customers and 1.8 million natural gas customers.

The Bayfront Facility, located on Lake Superior in Ashland, Wisconsin is a three unit generating station that became a showcase for other plants due to their ingenious use of fuels over the last 20 years. Fuel sources include coal, waste wood, railroad ties, discarded tires, natural gas and petroleum coke. The uniqueness of utilizing these types of low cost materials to generate electricity eliminates the need for new landfill construction as well as the reduction of sulfur dioxide emissions from the plant. The Bayfront facility began operations in 1916 and has undergone several plant upgrades through the years. Since 1979 the plant has burned more than 3.1 million tons of alternative use fuels.

Clean water from Lake Superior is utilized to cool the plants condensers. Data from the facilities pumps was used to estimate the amount of cooling water needed to cool the turbines. In the Fall of 2001, the DNR requested that a flowmeter be installed to accurately monitor these same flows. According to Jeffrey Nourse, Instrument & Controls Engineer for Xcelâs Bayfront facility, 'We were ballparking the flow by how many boiler feed pumps we had going on or how many pumps were coming on and the capacity of each pump. One of our interns did research on available flowmeters. We then looked at price and performance and the Flo-Dar just seemed to make the best fit.ä

The Flo-Dar Family of flowmeters provide a revolutionary approach to open channel flow monitoring. Flo-Dar combines digital doppler radar velocity sensing technology with ultrasonic pulse echo level sensing to remotely measure open channel flows. Flo-Dar transmits a digital doppler radar beam that interacts with the fluid and reflects back signals at a different frequency than that which was transmitted. These reflected signals are compared with the transmitted frequency. The resulting frequency shift provides an accurate measure of the velocity and the direction of the flow. Level is detected by ultrasonic pulse echo. Flow is then calculated based on the Continuity Equation:

Flo-Dar provides the user with highly accurate flow measurements under a wide range of flows and site conditions. By measuring the velocity of the fluid from above, Flo-Dar eliminates accuracy problems inherent with submerged sensors including sensor disturbances, high solids content and distribution of reflectors.

In the Fall of 2001, Bayfront placed an order for one Flo-Dar Flowmeter for their permanent monitoring application. Flow data from the meters 4-20 mA outputs is fed directly in to their Bailey distribution control system.

Nourse states, 'We love the meter. We have had no problems whatsoever.ä Additionally he comments, 'The most attractive feature of the meter is the zero maintenance on the thing, unlike the bubbler type meters we have on outfall 1 and outfall 3.ä He adds, 'It takes an hour or two to do anything with the bubbler type meters. We have to use confined space and crawl down the manhole and get into it. There is seaweed and stuff all over the tube. With Flo-Dar we donât need confined space entry at all. The unit is down only 2.5 feet. You can lay on your belly on the surface and reach down and get it.ä

'We trend the flow for 16-18 weeks at a time and then we record it. Itâs always been right in there. I can see where we were doing about 10,600 gpm last night at about 6:45 and then we took a pump off. We went down to 6,000 gpm so we took off a 4,000 gpm pump last night when we took the boiler out, so it all coincides with the Flo-Dar data and makes sense.ä Nourse adds. We get some variance at the pipe weâre monitoring due to lake levels. You can actually see the moon phases as it goes up and down because it fills the pipe back up obviously as the lake level goes up and down.ä

Just as Xcelâs Bayfront facility is regarded as a model for which all other power generating plants can aspire to, it is fitting that they have also selected Flo-Dar, the worldâs most innovative flowmeter.