When excessive leakage does occur, it normally is an indication that new seals are required.
Not Scheduled. Disassemble seal and thoroughly clean seal components and shaft sleeve. Check
shaft sleeve for excessive wear and repair as required. Replace segments or other components as
6. Wicket Gates and Facing Plates
Annual. Measure clearance between gates at the top, middle, and bottom with feeler gauges with
gates closed and the servomotor pressure released. Check clearance between wicket gates and
upper and lower facing plates. Check gates and facing plates for cavitation damage, corrosion, or
other damage. Repair or repaint as required. Check leakage past packing and tighten as required.
Not Scheduled. Disassemble and check wicket gate bushings; thrust washers, stems, and packing
sleeve for wear or corrosion. If bushings are out of tolerance, replace and line bore, making sure
the bushings are bored concentric and plumb. Check upper and lower facing plates for scoring,
corrosion, or other damage and repair as required. Take measurements to verify that facing plates
are level and parallel to one another. If necessary, replace facing plates or machine existing plates
level and parallel to one another. Measure height of wicket gate and compare it to the distance
between the upper and lower facing plates. If out of tolerance, build up wicket gates ends and
machine back to specified dimensions. Check gate to gate sealing surfaces and build up and
remachine as required. Replace shaft packing.
7. Servomotors, Shift Ring, and Wicket Gate Linkage
Annual. Observe servomotor, shift ring, and wicket gate linkage as it is moved through its full
range of motion in both directions. Look for any lateral movement of shift ring indicating worn
bearing pads and for any backlash in the wicket gate linkage. Check for leakage past servomotor
packing glands and tighten as required. Check servomotor shaft for scoring and repair or
schedule repairs as required. Verify the existence of "cushioning" on the end of the closing
stroke. Adjust as necessary. Check amount of squeeze on the wicket gates by the procedure in
Section III, Part B, of FIST,
Volume 2-3, Mechanical Governors for
Remove at least 10 percent of the wicket gate shear pins and visually inspect for any signs of
fatigue cracking. If cracking is evident, inspect remaining shear pins and replace any that are
questionable. Keep records of when shear pins are replaced.
Not Scheduled. Disassemble and check condition of shift ring bearing pads and wicket gate linkage
bushings and pins. Replace if out of tolerance. Disassemble servomotors and check pistons and cylinder
for scoring or signs of misalignment and realign as required. Bore or polish scored cylinder and renew
piston by sleeving or other method. Replace piston rings. Check servomotor shaft for scoring and repair
by machining and hard chrome plating or other method if necessary. Replace packing as required.