Page 70 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

installatioil, Mninteimice, and Repair- of Horizontal Pisnips 55

Table 1-7
Bearing Bore and Shaft Diameter Minimum and Maximum Values
Recommended for Centrifugal Pump Radial Bearings

Bearing bore diameter
in. Shaft dia.
mn Max. Min. Max. Min. Fit in 0.0000 in.
20 0.7874 0.7870 0.7879 0.7875 -
IT
25 0.9843 0.9839 0.9848 0.9844 9T

75 2.9528 2.9522 2.9534 2.9529
3.1496 3.1490 3.1502 3.1497

trifiigal pumps complying with API 610. Figure 1-23 shows that installing
two of these bearings back-to-back with a radial interference of 0.0003 in.
will produce an almost insignificant preload of approximately 22 lbs.;
whereas, an interference fit of 0.0007 in. would result in a mounted preload
of 200 lbs.
A much more significant preload would be created by bearing inner ring
temperatures higher than bearing outer ring temperatures. With these tem-
perature differences in centrifugal pumps and electric motors typically
approaching 5OoF, actual preload values could easily exceed 2,000 lbs.
Worse yet, if the operator should decide to "cool" the bearing housing, a
100°F temperature difference might result. At this time, the preload value
will increase exponentially and the bearing would be in danger of imminent
destruction.'O