and west positions used for the shaft alignment readings do not necessarily have to
correspond exactly with the actual directions, but the position the bearing, seal ring,
and air gap readings are taken must correspond within a few degrees, with each
other, and the alignment readings. Referring to the readings as downstream,
upstream, right, and left may help with consistency. Preshutdown readings should
include all pertinent information such as reservoir and tailrace elevations, wicket gate
opening, and unit load.
The preshutdown readings should include, but not be
limited to the following:
Shaft runout readings-While shaft runout readings can be measured
with dial indicators, the preferred method would be to install at least
one pro3dmity probe at each guide bearing elevation and record the
data to a strip chart recorder, tape recorder, or some other type of data
logging device. Readings should be taken at various loads from speed-
no-load to full load including readings at any rough zone and with and
without the field voltage at speed-no-load.
Bearing temperatures.-Bearing and oil temperatures should be
recorded at various loads. If a temperature recorder is part of the unit
instrumentation, a recording of a normal startup showing the rate of
temperature rise should be included. The unit load and wicket gate
position should be noted on the recording.
Pressures.-The normal operating pressure of the turbine bearing oil
pumps, packing water supply, and cooling water supply should be
recorded. The pressure of the thrust bearing, high-pressure lubrication
system should be recorded during startup and shutdown.
Permanent magnet generator (PMG) voltage.-The PMG voltage
should be checked and compared to rated voltage. If the measured
voltage is more than 20 percent lower than the rated voltage, the field
should be remagnetized during the overhaul.
has a procedure for remagnetizing
the rotor of a PMG in section II.
The preteardown readings should be taken after the
unit is shut down and the clearance has been issued and should include, but not
be limited to, the following: