Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

552 Centrifugal Pumps: Design and Application
Figure 20-19. Magnetic face seals find extensive application in aerospace
pumping services (courtesy of Magnetic Seal Corporation, West Barrington
R.I.).
rates an elastomeric diaphragm and constitutes a completely enclosed
system, is screwed into the housing vent opening. It accommodates the
expansion and contraction of vapors in the bearing housing without permitting
moisture and other contaminants to enter. Carefully selected from
a variety of plain and fabric-supported elastomers, the diaphragm will
not fail prematurely in harsh chemical environments [14].
The upgraded medium-duty bearing housing shown in Figure 20-21 incorporates
the various bearing life improvement features that have been
discussed: (1) a deep-groove Conrad-type bearing with loose internal
clearance (C3); (2) a duplex angular contact (40°), lightly preloaded
back-to-back-mounted thrust bearing; (3) a vent port that remains
plugged for dry-sump oil-mist lubricated bearings and that can be fitted
with an expansion chamber if conventionally lubricated; (4) a magnetic
seal; and (5) a bearing housing end cover made to serve as a directed oilmist
fitting [6].
If oil mist is not available at a given location, the conventional lubrication
method shown earlier in Figure 20-16 would be the second choice
for engineers experienced with pump operation and maintenance. Third
choice would be as indicated in Figure 20-22, with the oil level at "A" or
reaching to the center of the lowermost ball. The oil ring, Item 1, serves
only to keep the oil in motion. If the oil level is allowed to drop to point
"B," the oil ring is expected to either feed oil into the bearings or generate
enough spray to somehow get adequate amounts of lubricant to the
various bearings. Unfortunately, there is no real assurance of this happening.
An oil ring with a given geometry will be fully effective only if it