Sealing an oil-lubricated bearing in an electric converter station
Problem and challenge
In some countries such as Sweden and north-eastern Germany, distributed mobile converter units employ rotating converters to change three phase power drawn from the public network into single-phase AC for use as railway traction power. In these areas, there are no dedicated power lines to feed power to the railway network. The converters are mounted in a fixed position on a wagon, which allows a substitute converter to be used when they need repair or replacement.
The converter consists of a motor and a generator. The bearing at one end of the generator rotor can move axially. The bearing is lubricated by oil. The fan wheels needed for cooling at both ends of the rotor develop a vacuum that sucks the bearing oil into the stator and into the rotor contained within it. An easily fitted, short bearing seal with leakage removal is needed here to prevent the stator and rotor from getting oiled up.
EagleBurgmann Espey solution
The operator of the rail power converter unit, Euromaint Rail AB in Sweden, trusted the Espey WD 500 Special with leakage removal to prevent the stator and rotor becoming oiled up. The seal is designed for a temperature of 60 °C (140 °F), a pressure of 0.9 bar (13.05 PSI) and a rotation speed of 500 rpm. Thanks to the split casing it is easily mounted, and is only 50 mm (1.97 ”) long. The oil that seeps in as a result of the vacuum is trapped in a leakage collection vessel, and is removed from time to time. The seal solution has a long service life, is maintenance-free, and compensates for shaft movements.