Page 219 - Improving Machinery Reliability

190 Improving Machinery Reliability

Example Problem

Step I:
Vendor A Proposes: Vendor B Prouoses:
P,, = 13,200 hp P,, = 13,200 hp
np = 8,088 rpm np = 8,087 rpm
d = 9.48 in. d = 8.77 in.
F= 18in. F = 18.25 in.
Ha = 338 Bhn minimum HG = 362 Bhn minimum
8,088 m,=--
8,087
mG=-= 4.513 - 4.512
1,792 1,792
'P = 30.02" 'P = 27.2"
N = 41 pinion teeth N = 39 pinion teeth
A = 14.5". ground teeth A = 20", shaved teeth
L = 19 in. L = 19.5 in.
Step 2: (From Figure 3-75)
246 280
K,, = - 175.7 K, = - 200
=
=
1.4 1.4
Lld = 1919.48 = 2 Lld = 19.518.77 = 2.22
Step 3:
126,000 x 13,200 x 5.513 126,000 x 13,200 x 5.512
K' = K'=
8,088 x 89.87 x 18 x 4.513 8,087 x 76.91 x 18.25 x 4.512
= 15.5.3 = 179
Ratio: 175.7115.5.3 = 1.13 Ratio: 2001179 = 1.12
Step 4:
P, = Nl(d1cos'P) P, = N(d/cos'P)
= 4119.48 x 0.8658) = 5 = 391(8.77 x 0.8894) = 5
13,200 x 126,000 x 5 13,200~ 126,000~ 5 1.4
s, = x 1.4 st =
8,088 x 9.48 x 18 8,087 x 8.77~ 18.25

1.8 x 0.8658 1.8 x 0.8894
X X
0.50 0.56
= 26,293 psi = 25,714 psi
Step 5: (From Figure 3-76)
For Ho = 338 Bhn For HG = 362 Bhn
S,= 29,000 psi S,= 3 1,500 psi
3 1,500
29,000
Ratio = - Ratio = -
-
-
1.103
=
1.225
26,293 25.714