Up Time Magazine- August/September 2008

lubrication upload Well Worth the Cost Bearing Housing Protector Seals and the Value of Reducing Lube Oil Contamination Risk by Heinz P. Bloch B y excluding moisture and solid contaminants from bearing housings and other machine shaft penetrations, you can gain significant economic benefits. Bearing housing seals are contaminant exclusion components that must be considered by reliability-focused users. They include lip seals that are inexpensive, but quite prone to wear (Figure 1). Figure 1 - Typical lip seal and shaft wear damage The shortcomings of lip seals led to the development of rotating labyrinth seals, generally called “bearing isolators”. These, too, can include makes and models that deserve closer scrutiny since they occasionally incorporate not only an air gap, but also a single O-ring to allow contact with the sharp edges of an O-ring groove (Figure 2). As the O-ring degrades, such protector seals may still allow airborne contaminants to reach both lube oil and bearings. Figure 2 - Vulnerability of dynamic O-ring components in contact with sharp O-ring groove(s) On the other hand, a well-designed rotating labyrinth seal (Figure 3) permits O-ring contact only with a considerably larger area, thus greatly decreasing both contact pressure and the resulting wear risk. There are also the well-known spring-loaded mechanical seals, but these are either too expensive or take up too much space. Fortunately, magnetically closed dual face bearing housing seals (Figure 4) bridge the gap. They are affordable and fit in tight places. We know from several decades of aerospace experience that magnetic seals similar to the dual-face industrial version shown in Fig. 4 have often been certified serviceable after well over 50,000 operating hours. Justifying the Cost of Modern Bearing Housing Protector Seals Assessing the true value and cost-justifying modern bearing housing protector seals is not difficult. Diligent research has made it possible to quantify the negative effect on bearing life of both moisture and solids contamination of lube oil. Researchers have published Life Extension Factors (LEF’s) that accompany changing from moist oils to drier lubricants (Table 1). Others have estimated the effects of solid contaminants on bearing life (Table 2) and published reasonable estimates as LEF’s. Using these tables, Figure 3 - Modern bearing housing protector seal designed to avoid risk of contacting a sharp edge (www.AESSEAL.com) 26 august/september 2008 http://www.AESSEAL.com

Table of Contents Feed for the Digital Edition of Up Time Magazine- August/September 2008

Up Time Magazine- August/September 2008 Contents Upfront Upclose Information Technology Lubrication Infrared Maintenance Management Motor Testing Precision Maintenance Reliability Ultrasound Vibration Upgrade

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