Setting the clearances on segmented shoe bearings can be a challenge. Most designs
allow the segments to pivot around the adjustment bolt. Since the segments pivot,
obtaining accurate clearance readings with a feeler gauge can be very difficult.
When taking readings with a feeler gauge, it is essential that the segment be held
level and tight against the adjusting bolt. When inserted, the feeler gauge should
extend all the way through the bearing to prevent obtaining a false high reading at
the top of the segment when the bottom is tight against the shaft. It is also helpful
to measure the clearance on either side of the pivot point at the same time to prevent
the shoe from pivoting to one side or the other.
Another method of setting the clearance is with a dial indicator on the adjusting bolt.
The bolt is turned in to make the bearing tight against the shaft, and the dial
indicator is set up on the head of the bolt and zeroed. The bolt is then backed out
the amount of the desired clearance and the lock nut tightened. The lock nut must
be tightened with care; if it is overtightened, it can actually stretch the adjusting bolt
to the point that the clearance is significantly reduced. As the bolt is stretched
between the locknut and the shoe, there will be no indication on the dial indicator.
If the dial indicator method is used, the clearance still should be verified with feeler
6.3 Wicket gate
The heel-to-toe clearance between wicket gates must be minimal to prevent
excessive leakage once the unit is watered up. Turnbuckles or eccentric adjustments
are provided in the wicket gate linkage to adjust the position of the gates and the
clearances between them. Procedures for adjusting the gates are found in
The squeeze on the gates should also be adjusted. The squeeze is the amount the
servomotors travel after the gates contact each other. The squeeze takes up the
slack in the gate operating mechanism and holds the gates shut when the spiral case
is watered up. The squeeze must be adjusted so that each servomotor moves the
same amount to prevent distorting the operating ring. Part III, Section B, of
has a procedure for
adjusting the squeeze on the wicket gates.
6.4 Gaskets and packing
The gaskets should be cut prior to reassembly using the old gaskets as a pattern if possible.
The mating surfaces of the gasketed joint should be thoroughly cleaned and checked for any
large nicks, dents or gouges, or any other surface imperfections that would prevent the
gasket from sealing. The gasket material used must be compatible with the fluid being
sealed and should be as thin as possible while being thick enough to seal. The
manufacturer's recommendation should be used if available or the old gasket can be used as
a guide, keeping in mind that the old gasket is probably somewhat deformed by