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Water lubricates screw bearing
by Roy OConnor, European Bureau Chief, Global Design News -- Design News, January 20, 2002
Hammelburg, Germany — Environmentally friendly ways of generating power have captivated the interest of many engineers and technologists. This is certainly the case with Otto Huppmann, who operates a water mill on the River Saale near Hammelburg. Following a line of development pioneered by the ancient Egyptians, he decided to install a hydrodynamic screw to supplement his existing water wheels, which are of conventional design. Ritz-Atro of Nuremberg, specialists in pumps and screw-conveyors, could supply a suitable screw, but one bearing would need to be continually immersed in water. Furthermore, it would have to be capable of continuous running, 24 hours per day all the year round.
Ritz-Atro worked with FAG Kugelfischer to produce a bearing based on FAG's X-Life range. The design used in this application incorporates high-nitride special steel in a high-precision bearing resistant to wear and corrosion. It also satisfies one of Huppmann's primary environmental considerations—the bearing needs no lubricating grease that might pollute the river. In fact, Noriko Horn, X-Life marketing manager at FAG, points out, "The flowing water itself provides sufficient lubrication for the bearing." She expects the X-Life bearing, which also withstands extreme temperatures and high levels of contamination, to give a service life in excess of 30 years.
According to Jürgen Franz, managing director of Ritz-Atro, the efficiency of the screw is very high, approaching that of a turbine. Also, an advantage of a screw design compared to a water wheel is that the parts subject to friction are always more uniformly stressed, prolonging the service life. The screw, which weighs 1.8 tons and is more than 6m long, has a maximum power rating of 10 kW. With an estimated annual energy output of 50 megawatt-hours, sufficient for about 12 average German households, the savings from this "free" source of energy can be appreciated.
For more information about X-Life bearings from FAG: Enter 542
