5.5.1
Methods to determine impeller nose clearance
During Installation Or Repair
With a feeler gauge, measure the gap between the nose of the impeller and the casing liner on the suc-
tion side.
During Normal Service
Move impeller toward suction side of casing liner until parallel surfaces slightly rub. Measure “X” dimen-
sion and add the recommended impeller nose clearance. Adjust dimension “X” per “Impeller Clearance
Adjustment
Procedure.”
Impeller Clearance Adjustment Procedure
1.
Turn stud jam nuts at the bearing frame lugs to drive the shaft assembly in the desired direction.
Moving shaft (122) toward suction side casing liner will decrease the clearance
2.
To decrease impeller clearance, loosen outboard jam nut and drive the shaft assembly by turning
the inboard jam nut.
3.
When desired clearance is reached, tighten outboard jam nut securely. Check clearance after
tightening.
4.
To increase impeller clearance, loosen inboard jam nut and drive the shaft assembly by turning
the outboard jam nut.
CAUTION:
Jam nuts on both sides of bearing frame lugs must be secure. Normal impeller thrust will tend
to decrease the impeller clearance. Impeller rubbing will result from insufficient jam nut tighten-
ing.
Conditions Requiring Adjustments
1.
Overheated thrust bearings may develop from uneven adjustment of jam nuts. Check lubrication.
2.
Noise, vibration and wear may result from the impeller rubbing on the suction or hub side casing
liners. Adjust impeller clearance.
3.
Poor performance and wear may result from excessive impeller clearance at the suction side
casing liner.
NOTICE:
Lubricate adjusting studs (356A) for easy maintenance.
5.6 Maintenance of Bearings
5.6.1 Bearing lubrication and care
Bearings must be lubricated properly in order to prevent excess heat generation, sparks, and
premature failure.
5.6 Maintenance of Bearings
30
Model JC Installation, Operation and Maintenance Instructions
