ABB BSM100, Инструкция по установке и эксплуатации

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2-5 MN1240
Life Determination
How Life is Determined
A life estimate is a calculated, statistical expectancy and is defined as the length
of time, or the number of revolutions, until fatigue develops. This life depends on
many different factors such as loading, speed, lubrication, operating temperature,
contamination, plus other environmental factors. It’s impossible to predict precisely.
Statistical calculation estimates are based upon L
10
life. This is the life that 90 percent
of a group, of apparently identical parts, will reach or exceed. Typical bearing radial
load capacity curves presented in the literature are based upon bearing L
10
life of
20,000 hours.
Using the Curves
First determine your load (or force), location (or distance) from the bearing the load will
be applied, and speed (or RPM). Second, plot these points on the curve. For example,
using the BSM80 (Figure 2-4) a force of 80 lbs (352 N), applied 1 inch (25mm) from the
bearing, with a motor speed of 2,000 RPM, would relate to a bearing L10 life estimate
of 20,000 hours.
Figure 2-4
(Radial Force)
Operating 24 hours / day, results in approximately 8500 hours per year. This would
provide a L
10
life estimate of: (20,000 hours) / (8500 hours/yr)=2.35yrs.
If Plotted Point Does Not Match your RPM
Many times the point plotted (force and distance), is not specifically on your
applications speed curve, so an estimate for life is calculated as follows:
L
10
16667
S
x C
F
3
Where: L
10
= 20,000 hours
S = RPM
C = capacity of system
F = Force or Load (lb)
Example : Provide an estimate L
10
life for a BSM90 motor with a radial load or force of
130 lbs (570 N) located 3” (76mm) from the bearing. Operating speed is 1000 RPM.
1. Determine the systems capacity − at the distance for our application. To
do this, refer to Figure 2-5 and read information from the curve:
a. Locate our distance (3”) on the X axis.
b. Pick a speed (8,000 RPM) and locate the intersect with the 3”.
c. Read the force (100 lbs) on the Y axis.