Premature failure is a common fate for large-diameter bearings in heavy-duty applications where rotations are frequent. In big rotating equipment, such as cranes, excavators and tunnel boring machines, a slewing ring bearing must simultaneously handle a complex load spectrum that covers diverse combinations of thrust, radial and tilting moment loading.
Fortunately, there’s an easy way to protect your investment in these custom-engineered bearings. It’s called regular maintenance, and it can prevent 96% of slewing ring bearing failures. To maximize bearing life, simply follow these four tips – raceway and gear lubrication, torque checks on bolts, and seal inspection – and be alert for four warning signs of potential bearing problems.
Bearing Lubrication
A bearing should be lubricated at regular intervals with heavy-duty, extreme-pressure grease. Apply a liberal shot to the fittings around the bearing’s circumference at the interval recommended in the operator’s manual.
Slowly-rotating equipment or oscillating applications (e.g., backhoes, excavators, cranes) should be re-lubricated about every 100 hours of operation. More frequent lubrication – every day or even every eight hours – may be needed on equipment that moves rapidly or rotates continuously, such as trenchers and boring machines.
While adding grease, the bearings should be rotated to spread the grease throughout. Pump it in until you see the old grease squeeze past the seal; this is called purging. Purged grease carries contaminants out of the bearing. Rub some between your thumb and forefinger… if you feel grit or metal chips, you may have a bearing problem.
Grease tends to dry out over long periods of time, allowing condensation to form within a bearing. You can avoid this by introducing grease at least every six months, even when the equipment is sitting idle.
