Page 72 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Installation, Maintenance, and Repair of Horizontal Pumps 57

Plugged Connections

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Figure 1-24. A single % in. hole will safeguard the life of mechanical seals.

Stationary seals can accommodate greater shaft deflections and higher
peripheral speeds than conventional mechanical seals. Many of the most
dependable and reliable high MTBF installations use stationary seals in
steep-tapered seal housings.

Lubrication: Common But Misunderstood
A rather large number of factors influence lubricating oil degradation and,
consequently, pump bearing life. If your centrifugal pumps are equipped
with rolling element bearings, there is little doubt that medium viscosity tur-
bine oils (IS0 Grade 68) will perform better than lighter oils originally
specified by many pump manufacturers. However, by far the most frequent
cause of lube oil related failures is due to water and dirt contamination. With
only 20 ppm water in pure mineral oil, bearing race and rolling element
fatigue life is reduced by an incredible 48 percent. Although the fatigue life
reduction is less pronounced with inhibited lubricants, there are always
compelling reasons to exclude water and dirt from pump bearing housings. l1
Lip seals are a poor choice for centrifugal pumps requiring high reliabili-
ty. Face seals offer superior “hermetic” sealing and should be given serious
consideration.l29 l3
On a related subject, have you explained to your operators and mainte-
nance personnel that a full bottle oiler is no guarantee of adequate lubrica-
tion? The height of the beveled tube determines the level of oil in the bear-
ing housing, and all too often there will be costly misunderstandings.