Page 131 - Improving Machinery Reliability

Mnchinery Reliuhility Audits and Reviews 103

100% load. Calculations made on a recent audit of a gear are given in Table 3-3. The
gear shafts used four lobed bearings and the bearings stiffnesses and damping changed
considerably as the load changed (Table 3-4). To evaluate the changes in fixed-ele-
ment bearing properties, rotor response to unbalance calculations must be made.

Table 3-3
Bearing Loads as a Function of Transmitted Horsepower
Horsepower = 31,046 bhp
Driver Speed = 5,670 rpm
Driven Speed = 10,742 rpm
PD Driver = 23.190 in.
PD Driven = 12.240 in.
Press. Ang. = 20"
Helix Ang. = 14"
Wt Loads: A = -778.0 Ib Mesh disk A = 14.17 in.
B = -1,349.0 Ib B = 14.17 in.
C = -527.0 Ib C = 14.17 in.
b = -396.0 Ib D = 14.17 in.
Right handed helix on driver
Upmesh-speed increaser

Bull Gear (Driver) Bearing Forces-lb
%Load BRQ IFsepl IFtanl Fwt Fxnet Fynet Mag Deg Fax
100.00 A 5,568. 14,875. - 178. -2,646. -I 5,653. 15,875. 260. 7,142.
100.00 B 5,568. 14,875. -1,349. -8,490. -16,224. 18,311. 242.
75.00 A 4,176. 11,156. - 778. -1,984. -I 1,934. 12,098. 261. 5,357.
75.00 B 4,176. 11,156. -1,349. -6,368. -12,505. 14,033. 243.
50.00 A 2,784. 7,438. - 778. -1,323. - 8,216. 8,32 1. 261. 3,571.
50.00 B 2,784. 7,438. -1,349. -4,245. - 8,787. 9,758. 244.
25.00 A 1,392. 3,7 19. - 778. - 661. - 4,497. 4,545. 262. 1,786.
25.00 B 1,392. 3,719. -1,349. -2,123. - 5,068. 5,494. 247.
10.00 A 557. 1,488. - 778. - 265. - 2,266. 2,28 I. 263. 714.
10.00 B 557. 1,488. -1,349. - 849. - 2,837. 2,961. 253.
Pinion (Driven) Bearing Forcedb
%Load BRG IFsepl IFtanl Fwt Fxnet Fynet Mag Deg Fax

100.00 C 5,568. 14,875. -527. 7,110. 14,348. 16,013. 64. -7,142.
100.00 D 5,568. 14,875. -396. 4,026. 14,479. 15,028. 74.
75.00 C 4,176. 11,156. -527. 5,333. 10,629. 1 1,892. 63. -5,357.
75.00 D 4,176. 11,156. -396. 3,019. 10,760. 11,176. 74.
50.00 C 2,784. 7,438. -527. 3,555. 6,911. 7,771. 63. -3,571.
50.00 D 2,784. 7,438. -396. 2,013. 7,042. 7,324. 14.
25.00 c 1,392. 3,719 - 527. 1,778. 3,192. 3,653. 61. -1,786.
25.00 D 1,392. 3,719. - 396. 1,006. 3,323. 3,472. 73.
10.00 C 557. 1,488. - 527. 711. 961. 1,195. 53. - 714.
D
557.
10.00 - 1,488. -396. 403. 1,092. 1,163. 70.