One of my customers asked me one day if he really had to replace the oil slinger when he replaced the bearing in his multistage, centrifugal air blower. That got me thinking about all of the other components in the "standard" bearing kit. Do you have to replace all of the gaskets, and locknuts, and seals? The short answer is Yes...and No!
The purpose for having all the "miscellaneous components" in a bearing kit is so you have everything you need, in case you need it. For most bearing failures, the only wear item is the bearing. And since you usually cannot "see" the wear, you replace the bearing anyway! In fact, any bearing manufacturer will tell you, the act of removing a bearing from the shaft damages it enough so it must be replaced.
Although oil slingers are found in many types of rotating equipment, my discussion will be limited to centrifugal air blowers. The oil slingers are always flat steel, or aluminum, discs, with a hole in the center so it fits over the shaft. It spins with the shaft while it "slings" oil around within the bearing housing. Oil is not going to wear the steel shaft, but any type of foreign material-bearing chips, dirt, etc... could cause wear.
Oil slingers are worn when they are not perfectly flat, and with any damage whatsoever. Any dimples, cracks, or waviness will cause the slinger to act more like a pump, and throw excess oil around the housing, leading to oil leakage. So if it doesn't look like new, replace it! Likewise with the grease slinger, if it is deformed in any way, replace it.
The grease slinger is most often damaged during disassembly. Because the bearing housing is removed with the bearing inside it, driving the bearing out of the housing can damage the grease slinger, unless you are very careful, and know what you are doing. Many times, the mechanic who replaced the bearing before you, could have damaged any of the components.
Locknuts and lockwashers are best replaced. The nut is usually damaged, at least partially, during assembly, and almost always during disassembly. The lockwasher has a tab that is bent to "lock in" the nut. Bending it back to remove the nut weakens, and sometimes breaks, the tab so it should not be used again. Best to replace the washer complete. Ditto for the gaskets. They are inexpensive enough that it is best to replace them. Believe me, finding an oil leak after re-assembly because you thought the gasket "looked" good, is not fun!
An important part of preventative maintenance is using quality parts. OEM's are always a safe bet for quality, as well as some aftermarket suppliers, but not all. If in doubt, use the OEM. Invest in PM, it will save you money!
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