Page 139 - Improving Machinery Reliability

Machinery Reliability Audits and Reviews 111

Table 3-5
Torsional Stress Calculations at the Second Torsional Natural Frequency
for 1 % Excitation at the Bull Gear
Dynamic torques (lob zero-peak) applied at the bull gear
Maximum resultant torsional stresses at the 2nd torsional resonance 6,869.44 cpm

Stress Stress
Shaft psi P-P scf psi P-P
I 3.92 2.00 7.83
2 34.47 I .50 51.71
3 117.23 3.00 35 I .68
pi* Dynamic torque variation 468.82 ft-lbs
5 21.76 3.00 65.27
6* Gear mesh
7 I.334.81 3.00 4,004.43
8* Dynamic torque variation 2,626.80 ft-lbs
9 1,393.16 3.00 4,179.49
10 859.02 1.50 1,288.52
11 723.70 1.50 1,085.55
12 582.18 I .50 873.27
13 564.75 I .50 847.12
14 434.23 1.50 65 1.35
15 422.73 1.50 634.09
16 41 1.05 1.50 6 16.57
17 3 14.94 1.50 472.41
18 215.28 1.50 322.93
19 98.88 I .50 148.32
~~ ___
Note: xValires cire clyircriiiic torque vnriatiori across coupling or gear, fi-lbs

880

L
"
r
w
0
a
L
r
5 4e8
5:
a
2
z
- 200
B
::
288 IEB 600 I008
WERAIING SPEED. RPH
Figure 3-25. Interference diagram for induction motor with variable speed drive.