4 Warning Signs of slewing Bearing Problems
Regular maintenance goes a long way toward preventing premature failure, but even the most faithfully maintained bearings will eventually show signs of wear. To extend
their life, look for these common signs and take corrective action as indicated.
(1)Play or clearance in the bearing often signifies that a raceway is worn. A new bearing is assembled with a specific amount of clearance to compensate for slight out-offlatness
in a mounting structure. Wear can increase this clearance dramatically. In machinery with a boom, free play magnified over the length of the boom allows it to
rock back and forth under load, reducing the ‘stiffness’ in the extended boom. Check bearing clearance with a dial indicator that measures how much the structure tilts
when the boom is loaded.
(2)Grinding, popping, or clicking noises from the bearing typically mean there could be inadequate lubrication and/or excessive wear in the raceway , or loose bolts. As noted
previously, greasing the bearing and purging lubricant is a good way to check for metal particles.
(3)An increase in torque or binding can mean uneven wear in the raceway. If the turning torque of the bearing increases substantially or the bearing has tight spots, the
load is probably unevenly distributed. With excavators, for example, the operator may sense a resistance to swing and find that the upper boom swings an inch or two past
the point where it should stop. In advanced stages of wear, the bearing will pop and crack as the machine digs and swings.
(4)Dimpled raceways are typically the result of overloading the bearing or repetitive, heavy loads. Even slight overloads can dimple a bearing race, and a dimple that starts
at 1/1000th of an inch will almost always get bigger. The same goes for uneven loads. Lifting with a boom and undercarriage in the same position every time (such as
curbside digging with an excavator) can dimple the bearing race near the uneven load. If possible, change the angle of approach from job to job.