Page 95 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Pump Best Practices Best Practice 2 .13

Fig 2.13.3 Bearing application guidelines

separate, but should include as a minimum an oil pump, reser- Figures 2.13.4 and 2.13.5 present the relationships for these two
voir, filter, cooler, controls and instrumentation. important factors.
The D-N number is the product of bearing size (bore) in
millimeters and the rated speed in revolutions per minute. It is Anti-friction bearings
used as a measure of generated frictional heat, and to determine
the type of bearing to be used and type of lubrication required. Ball bearings
The anti-friction bearing most commonly used in centrifugal
pumps for carrying radial and thrust loads is the ball bearing. The
design of each type of bearing has its individual advantages for
Used for all anti-friction bearings
specific load carrying requirements (refer to Figure 2.13.6).
16700 C 3
L 10 =
N F Roller bearings
where: L-10 = hours of operation 90% of a group of identical Anti-friction roller bearings are capable of accepting pure radial
bearings will complete or exceed loads, pure thrust loads or various combinations. They have been
N = pump speed – RPM applied as crankshaft bearings in the power ends of some power
C = the total force (kg [lbs]) required to fail the bearing after pump designs. Refer to Figure 2.13.7. Choice of this type of
1,000,000 revolutions (failure defined as 100% increase in bearing resides with the manufacture and is not usually an
measured vibration) option for the user.
F = the total of all actual forces acting on the bearing (kg [lbs])
Lubrication
Fig 2.13.4 L-10 Life
The purpose of anti-friction bearing lubrication is to increase
bearing life, keep the balls or rollers separated, dissipate the heat
generated in and conducted into the bearing, and to prevent cor-
Is a measure of the rotational speed of the anti-friction bearing rosion. There are various methods of oil lubrication for ball and
elements
D-N number = bearing bore (millimeters) speed (RPM) Is
used to determine bearing type and lubrication requirements
D-N range bearing type lubrication type
Below 100,000 anti-friction sealed
100,000 – anti-friction regreasable
300,000
Below 300,000 anti-friction oil lube
(unpressurized)
Above 300,000 sleeve, multi-lobe or tilt oil lube (pressurized)
pad

Fig 2.13.5 D-N Number Fig 2.13.6 Typical ball bearing load capacity guidelines

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