Pictures of the Future      Spring 2005

Fluid Information

Planning water and sewage networks is no easy task. If pipes and pumps don’t have the right dimensions, major problems can occur. But newly developed software is making it possible for engineers to precisely calcu­late and simulate these labyrinths before excavators even start their work.

Beneath every city there lies a hidden world—the storm sewage system. Movie directors have used this concealed realm as an uncanny backdrop. For example, the chase through Vienna’s sewers in The Third Man is a mythical image of the criminal underworld’s dark depths. But researchers at Siemens Corporate Technology (CT) and Industrial Solutions and Services (I&S) see the labyrinths from a more practical perspective. They deal with the material that disappears into sewage systems every day—including more than 10 million cubic meters of wastewater in Germany alone. Researchers at Siemens have developed a software system, SIWA PLAN, (SIWA stands for Siemens Water) that helps them calculate, simulate and efficiently control the flow of drinking water and wastewater in mains and sewer pipes.

Flood Control Reservoirs Under Pressure. Simulating flows is not easy because water’s dynamics—its flow characteristics—are constantly changing. Small waste pipes empty into larger ones, which branch off and converge. As a rule, channel networks are planned with large and expensive safety margins and reserve capacities. "But often, even that isn’t adequate to cope with extreme natural events such as heavy rainstorms," says Roland Rosen, who played a key role in developing SIWA PLAN at CT in Munich.

When a major storm breaks, the main sewers, which are as tall as a man, can fill to the brim within minutes and become rushing torrents. The channel net­work may become overloaded, meaning that instead of channeling flows into sewage treatment plants, it allows wastewater to escape into rivers without being cleaned. In many cases even large flood control reservoirs are unable to hold the volume of water released by some storms. But all of this can be avoided with computer-supported calculation of water volumes, according to Rosen.

To this end, the SIWA PLAN SEWER software system is outfitted with com­prehensive data from the channel network, such as pipe diameters, storage reservoir capacity and maximum outflow. Furthermore, if additional statistical data is available, such as rain volume or fill levels of individual pipe sections, the program can identify those sections of the network that are reaching their limit and those with capacity to spare. "By controlling the outflow from a storage reservoir in a targeted way, we can make the water flow much more evenly," Rosen explains. Electric slide controls are used to release the water in controlled doses, thus reducing scavenging effects. In other words, a major rainfall’s first surge can carry along (scavenge) large amounts of material accumulated in pipes during dry periods. It’s especially important to channel this wastewater so that it will find its way into treatment plants, even during heavy rains.

And the system has other uses in addition to controlling channel networks. Researchers at Siemens have developed simulator (SIM) and training function (TRAIN) components for SIWA PLAN. These components were put to their first practical test in 2003, in a training program for technicians at a new pipeline for potable water in Fujairah, United Arab Emirates. The components passed with flying colors.

The water system includes a gigantic underground pipeline across 180 km of desert. The pipeline connects a desalinization plant with a number of cities. Each of the double-walled pipes has a diameter of 1.6 m, so that each meter of pipe holds around two tons of water. For the first 20 km, the enormous pipeline climbs a 500-meter hill. Powerful pumps are needed to propel as much as 465,000 m&up3; of water a day up this incline. The system’s eight pumps provide around 50 MW of power—enough to cover the needs of a small town. Even though the system is extremely powerful, it’s also very sensitive. For example, standing water must initially be slowly set into motion by four backing pumps. Only then can the main units be switched on. If the machines were to run for even a few seconds without water, they would be destroyed. That’s because the water flowing over them also cools them. Hundreds of valves, several intermediate storage reservoirs, and all the branches of the pipeline have to be perfectly coordinated.

Complex Liquids. "In next to no time, faults can develop and lead to serious consequences," says Rosen, referring to possible problems such as pipeline leaks. "With SIWA PLAN TRAIN, we can simulate every possible fault scenario and practice the right reactions with the same user interface as in the real system," he adds. If a user makes an error, SIWA PLAN TRAIN promptly simulates the possible consequences. "Water is a complex substance," says Rosen. "Even modeling the flow of water in a garden hose that children are stepping on is a difficult task."

That’s why Dr. Andreas Pirsing, a project leader at Siemens I&S in Berlin, considers SIWA PLAN a valuable and unprecedented tool. "We’ve linked the process technology expertise we acquired in hydraulic engineering together with mathematical knowledge and computer science. The result is that we can now offer solutions for a whole range of problems," he says.

In the future, water network planning worldwide is likely to make greater use of this combined expertise. "Water is becoming an increasingly precious resource, so its efficient transport is becoming more important," Pirsing adds. He believes "SEWER" software will play a particularly vital role in central Europe in coming years. "Germany alone has 7,500 wastewater networks with a total length of 400,000 km, and many operators rely on individual solutions to run them." Hardly any simulations or training functions have been available to date. But that’s about to change, says Pirsing: "Simulations are going to be more significant, especially with stricter environmental regulations and consumer demand for improved wastewater management."
                                                                                                                   Tim Schröder