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Insulated bearings key to longer maintenance intervals


Today’s generation of trains can travel further, faster and with much longer maintenance intervals,
largely as a result of developments with AC traction motors.


However, bearings specialist NINE STAR makes the point that operators are now looking for
maintenance-free running further intervals. And the way to achieve that is to specify modern insulated
rolling bearings.


A major obstacle to achieving extended maintenance-free intervals is electrical erosion. This occurs
when stray electric currents flow through motor bearings to earth. The result is damage to the bearing.The
damage is usually in the form of craters on the bearing raceway and rolling element surfaces, resulting in
premature bearing failure.


NINE STAR has now developed a range of insulated bearings to combat the problem, using two
new processes – one using ceramic balls, the other is Aluminum Oxide coating, using a plasma spraying
method onto the bearing’s inner ring or outer ring, enabling the bearings to cope with direct voltages at
least 1000v DC.