Specific Machine Faults
It is also instructive to look at the types of repair that were requested by the automated diagnostic system and then performed.
|
Ship |
No. of Machines |
Balance |
Alignment |
Bearings |
Other |
|
CV41,43
|
1755
|
22
|
10
|
25
|
43
|
|
CV59-67
|
4877
|
21
|
13
|
25
|
41
|
|
CVN68,69
|
527
|
28
|
15
|
22
|
35
|
|
AVT16
|
383
|
20
|
19
|
13
|
48
|
Here it can be seen that Balance, Alignment, and Bearing problems account for more than half of all machine repairs. Of course, these fault categories are interrelated, for most bearing problems are caused by imbalance and misalignment. It is said that only a few percent of rolling element bearings achieve their design lifetime.
Perhaps more interesting is the repair recommendation record for the USS America (CV66), shown below. This is the relation between vibration survey dates and percentage of machines recommended for overhaul. The Feb. 88, Aug. 90, and Aug. 93 surveys were made just after overhauls.
|
|
Feb. 88 |
Sep. 89 |
Aug. 90 |
Mar 91 |
Aug. 92 |
Aug. 93 |
|
Percent of all machines needing repair
|
12
|
8
|
10
|
7.5
|
7
|
13
|
The fact that the percentages of problems post overhaul were higher than at other times indicates that the overhauls created more problems than they fixed. This is in keeping with the earlier airline study that showed high numbers of startup failures after overhaul.
This pattern is not as apparent on most of the ships surveyed.
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