Check condition of coating on draft tube liner' Look for any
cavitation damage, especially directly under the turbine runner on the throat
ring. Tap draft tube liner with a hammer to find any voids that will require
Spiral case and penstock.
Check condition of interior coating and exterior
coating of exposed portions of penstock. Pay special attention to the exterior
of the penstock where it emerges from concrete.
With gates open, inspect each gate, checking the condition of
the seal area, the surface coating, and for any cavitation damage. If sealing
surfaces are uneven or damaged, they should be repaired by welding and
machining back to drawing dimensions. With the gates closed, check the top
and bottom clearances between - the gates and the facing plates and the
clearances between the gates. The heel and toe sides of the gate should both
be measured when checking the top and bottom clearances. In checking the
clearances between gates, check the clearance at the top, middle, and bottom.
Check condition of facing plates looking for any galling or wear from contact
with the wicket gates. If the facing plates are severely damaged, they will
require replacement or resurfacing.
Wicket gate operating linkage.
Move gates through their full range of
movement in both directions several times. Watch for any lateral movement of
the shift ring or backlash in the wicket gate linkage. Remove the gate arm
from one wicket gate and inspect thrust washer. Check wicket gate bushing
clearance by jacking wicket gate shaft and measuring movement with dial
indicators. This may not give a true indication of clearance due to hardened
grease or other debris in the bushings. Check servomotor shaft for scoring. If
possible, remove servomotor cylinder head and check cylinder bore for
Check condition and dimensions of all spare guide and thrust
bearings. Have bearings rebabbitted if necessary.
Thoroughly inspect all stress carrying parts of rotor for
cracks. Pay particular attention to welds on the rotor spider.
Generator air coolers.
Check for any leaks. If possible, inspect interior of
tubes for scale buildup or corrosion. If spare coolers are available, make sure
they are ready for installation.
Several sets of manufacturer's "as-built" drawings should be obtained for both the
generator and turbine. Prior to the overhaul, the overhaul supervisors should study
the drawings and become familiar with the