Shaft Sleeves. Inspect shaft sleeves each year. They are subject
to wear and may require replacement, depending on the severity of service. When the
sleeve has become appreciably worn, the packing cannot be adjusted to prevent
leakage and the sleeve should be replaced. Otherwise, excessively grooved or scored
sleeves will pare and score new packing as soon as it is inserted into the stuffing box.
Bearings. Inspect the bearings and add lubricant according to the
procedures described in Table 17.
Wearing or Sealing Rings. Each year, inspect the wearing or sealing
rings that seal the discharge water from suction water in rotating pumps. These are not
perfect seals and do allow some leakage. Do not allow this leakage to become
excessive because of worn rings, or the pump efficiency will be impaired. Three types
of wearing rings are shown in Figure 5.
Proper wearing ring clearance is very important. In the straight-
type wearing ring, the most common type, the diametrical clearance need not be less
than 0.025 inch (0.64 mm) and should not be greater than 0.050 inch (1.25 mm).
In the L-shaped type, clearance in the space parallel to the shaft
should be the same as for the straight-type. The clearance of the space at the right
angle to the shaft is governed by the end-play tolerances in the bearing.
For specification information on the L-shape and labyrinth-type
rings, consult the manufacturer's manual.
Impeller. Each year, remove the rotating element and inspect it
thoroughly for wear (see par. 188.8.131.52 for dismantling procedures).
Remove any deposits or scaling.
Check for erosion and cavitation effects. Cavitation causes severe
pitting and a spongy appearance in the metal.
If cavitation effects are severe, some changes in pump design or
use may be necessary. Report the matter to the supervisor.