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The other method for measuring static runout requires installing dial indicators at the turbine
bearing and at thrust bearing elevations. Two indicators are located at each elevation to indicate
movement in the north-south and east-west axes. The indicators are zeroed with the shaft in the
0 degree position, and plumb readings taken. These plumb readings will serve as a reference for
the other readings. The shaft is then rotated 90 degrees. If the shaft is not totally free after
bearing and at thrust bearing elevations. Two indicators are located at each elevation to indicate
movement in the north-south and east-west axes. The indicators are zeroed with the shaft in the
0 degree position, and plumb readings taken. These plumb readings will serve as a reference for
the other readings. The shaft is then rotated 90 degrees. If the shaft is not totally free after
r
otating, it must be moved laterally at the thrust bearing until it is free. The indicators are read
once the shaft is free. This is repeated for 180, 270, and 360 degree positions. The corrected
data for the 360 degree data should be zero. An example of a form for recording the data using
this method is shown in Figure 18. It is important that the dial indicators are not moved or
adjusted after they are zeroed at the 0-degree position. The top reading is subtracted from the
bottom reading to correct for any lateral movement at the thrust bearing and to provide the actual
runout at the turbine bearing. The plumb reading in the 0-degree position is used to determine
the position of the center of runout with respect to plumb. The dial indicator method of
measuring static runout is faster than the wire method and, if done correctly, will provide
accurate results.
data for the 360 degree data should be zero. An example of a form for recording the data using
this method is shown in Figure 18. It is important that the dial indicators are not moved or
adjusted after they are zeroed at the 0-degree position. The top reading is subtracted from the
bottom reading to correct for any lateral movement at the thrust bearing and to provide the actual
runout at the turbine bearing. The plumb reading in the 0-degree position is used to determine
the position of the center of runout with respect to plumb. The dial indicator method of
measuring static runout is faster than the wire method and, if done correctly, will provide
accurate results.
5.4 Clearance and Concentricity Readings
If the unit is completely disassembled, the concentricity of the stationary components can be
checked by temporarily installing the upper and lower bridges and the head cover and hanging a
single plumb wire through the unit. An electric micrometer is used to measure from the wire to
the stationary components. This procedure is particularly useful during major overhauls. If new
stationary seal rings are being installed, this procedure provides a reference to allow the seal
rings to be bored concentric to the stator. It also allows a more accurate profile of the stator to be
determined. With the rotor installed, only the top and bottom of the stator can be measured.
With the rotor removed and the single wire installed, readings can be taken at several elevations
to get a true profile of the stator bore. The turbine bearing housing can also be centered to the
seal rings at this time. Once the wicket gate linkage is installed, moving the turbine bearing is
difficult or impossible.
checked by temporarily installing the upper and lower bridges and the head cover and hanging a
single plumb wire through the unit. An electric micrometer is used to measure from the wire to
the stationary components. This procedure is particularly useful during major overhauls. If new
stationary seal rings are being installed, this procedure provides a reference to allow the seal
rings to be bored concentric to the stator. It also allows a more accurate profile of the stator to be
determined. With the rotor installed, only the top and bottom of the stator can be measured.
With the rotor removed and the single wire installed, readings can be taken at several elevations
to get a true profile of the stator bore. The turbine bearing housing can also be centered to the
seal rings at this time. Once the wicket gate linkage is installed, moving the turbine bearing is
difficult or impossible.
The single wire can also be used to center and redowel the upper and lower bridges. This is
especially important on units that have sleeve type generator guide bearings. If the unit has
sleeve type generator guide bearings, the bridges should be temporarily installed with the
bearings in place and the bridges centered using the center of the bearing bores as the reference
point. This ensures that the bearings will be centered even if they are not concentric to their fit in
the bridges.
especially important on units that have sleeve type generator guide bearings. If the unit has
sleeve type generator guide bearings, the bridges should be temporarily installed with the
bearings in place and the bridges centered using the center of the bearing bores as the reference
point. This ensures that the bearings will be centered even if they are not concentric to their fit in
the bridges.
When the unit is assembled, the concentricity of the stationary components can be determined by
taking clearance readings, (i.e., bearing clearance, seal ring clearance, generator air gap, etc.), and
plotting the centers against the plot of the shaft centerline. The concentricity should be verified
using this method regardless of whether the concentricity was checked with a single wire. Don't
assume that everything is still concentric. Even doweled components can shift slightly.
taking clearance readings, (i.e., bearing clearance, seal ring clearance, generator air gap, etc.), and
plotting the centers against the plot of the shaft centerline. The concentricity should be verified
using this method regardless of whether the concentricity was checked with a single wire. Don't
assume that everything is still concentric. Even doweled components can shift slightly.
The internal diameter of a sleeve type guide bearing should be concentric with the outside fit of
the bearing shell. Therefore, when the bearing is not installed, the bearing center can be
determined by measuring with an inside micrometer from the fit on the bearing bracket or bridge
the bearing shell. Therefore, when the bearing is not installed, the bearing center can be
determined by measuring with an inside micrometer from the fit on the bearing bracket or bridge