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(May 18, 2011)
As pointed out in prior columns, the second leading cause of pump break downs is bearing failures. This is because fewer than 10% of all ball bearings run long enough to succumb to normal fatigue failure (20,000 hours for an ANSI Pump). Most bearings fail at an early age because of static overload, wear, corrosion, lubricant failure, contamination, or overheating.
Particle contamination and corrosion related failures account for 52% of all of these bearing failures. Bearing housing seals, and more specifically the seal type, play a crucial role in this centrifugal pump reliability component. They serve to both retain the lubricant within the bearing housing and to exclude both solid and liquid contaminants that can find openings to infiltrate both the lubricant and the bearings.
To further complicate this issue, bearing housings breath in and out as they cool down and heat up with shut down and start up. If a path or opening exists (through a housing vent or bearing housing shaft seal) to the external environment, ambient air will be induced to flow into the housing. Figure 2 shows just how sensitive bearing reliability is to even small amounts of water. This is of most concern in humid environments.
Traditional Bearing Housing Seals
Many pumps today are still equipped with large open vents and short-lived, wear-prone lip seals. These
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| CXM50M KOYO | 50 | 90 | 32 |
| CXM45M KOYO | 45 | 85 | 32 |