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4.8
vibration is measured using a non-contacting probe, add one half (1/2) mil to the above
levels. If vibration levels exceed the above values shut the unit down and determine the
cause of vibration.
Impeller to diffuser clearance
Impeller to diffuser clearances are factory set on new compressors, but the clearance
should be checked prior to initial start-up after an overhaul or any start-up after a rotor
assembly or bearing has been removed from the unit. This procedure should be done
under the supervision of an Ingersoll-Rand service supervisor.
Procedure to set an impeller to diffuser clearance for units without shims.
1.
Remove the bearing cover and bearing locking bolts.
2.
Tighten the jacking screws until the bearing is free to move, then loosen the jacking
screws.
3.
Push the bearing in until it seats against the gear case.
4.
Push the rotor assembly in by the thrust collar until resistance is felt.
Never attempt to set the clearances without an impeller clearance setting tool. See
the Centac Clearance Setting Tool diagram on the next page.
5.
Install the clearance setting tool against the thrust bolt using one of the bearing cover
bolt holes to support the other end.
6.
Install (2) dial indicators on a post installed in one of the other thrust cover bolt holes.
7.
Set (1) dial indicator to contact the top of the clearance-setting tool above the thrust
bolt. The purpose of this is to show the movement of the rotor.
8.
Set (1) dial indicator to contact the thrust bearing flange. The purpose of this indicator
is to indicate the movement of the bearing.
9.
Zero both indicators.
10. Begin tightening the jacking bolts in sequence. Each turn of the jacking bolt should
cause no more than .001 inch (0.03mm) of bearing movement. Gently tap bearing
flange near jacking bolt using soft hammer.
11. Note that the bearing moves before the rotor assembly begins to move.
12. Continue to tighten the jacking bolts until the specified pressure tip clearance is
indicated on the rotor assembly dial indicator.
13. Install and tighten the bearing locking bolts.
14. For units with reverse thrust buttons, turn set screw in until resistance is felt, and back
out 1/3 turn.
For units with adjustable reverse thrust bearings, set clearance with dial indicator
to .0.008" to 0.010". For units with preset reverse thrust bearings, there is no adjustment
required.
Centac Instruction Manual
2000 Ingersoll-Rand Company
Date of Issue: 12 September, 2000
SECTION 4 – MAINTENANCE
NOTE
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