Page 66 - Machinery Component Maintenance

Maintenance Organization and Control for Multi-Plant Corporations 51

ular intervals, and generally treated as a valuable spare part or essential
resource. Delaying an overhaul for several hours to fabricate a special
seal nut wrench is time and money wasted. Alignment brackets and cou-
pling “SO~O” plates fall into this category.

The Spare Rotor

By far the most critical single spare part is the spare rotor. Most com-
panies purchase the spare rotor at the time the machine is purchased and
require a four-hour mechanical test to ensure integrity prior to accep-
tance of the machine. It would be prudent to check the spare rotor after
every movement. This means a runout or rotor bow check upon receipt
from the manufacturer, as well as a check of the preservative used for
long-term storage. A runout check is also performed at the time the rotor
is check-balanced and prepared for installation. Be sure to obtain a rotor
runout diagram and balance report at that time.
Rotors of all sizes are often stored vertically in a remote temperature
controlled storage building as shown in Figure 2-13. If a user opts for
horizontal storage, the rotors must be placed on substantial stands and
should be turned 180” two to four times a year. These stands must em-
ploy rollers rather than lead or Teflon@ material at the support points. In
cases where sheet Teflon@ is placed between the storage cradle and the
rotor there is some risk of filling the microscopic pores of a shaft journal
which could prevent the formation of an adequate oil film on startup and
could cause bearing failure.
Rotors must, of course, be handled with great care. Nylon slings
should be used to prevent damage and all lifts should be made under the
watchful eye of a competent individual. Never hesitate to call a halt to a
lifting operation if the possibility of damage exists. You are being paid to
look out for the company’s interests and a rotor worth $lOO,OOO to
$l,OOO,OOO or more is well worth a lot of care and concern. The rotor
must be slung so that it is horizontal and its center of gravity is located
under the hook, and it must be moved very slowly. Consider your vibra-
tion monitoring probes when removing a rotor from storage in prepara-
tion for installation. Record the rotor’s serial number and verify that it is
not positioned in a way that will interfere with a thrust position eddy cur-
rent probe. Some users also report success with degaussing and/or mi-
cropeening techniques to minimize electrical runout in the areas viewed
by the radial eddy current probes. Others report some success rolling the
rotor on a balance stand with the areas under the probes directly on the
balance rollers.