Important things for tilting pad journal bearing

Update:20-03-2020
Summary:

Cleanliness and burr-free surfaces are vital to the pro […]

Cleanliness and burr-free surfaces are vital to the proper performance of the  bearing.  Remove any burrs  or raised edges on the pad faces with a scraper.  Remove any light burrs or fine rust on the collar with a fine oil stone.  Deep rust or bruising will require refinishing.

Prior to installation of the bearing assembly, insp ect the bearing cavity and cover for cleanliness. 

Remove any debris or dirt from the journal area, th e bearing fit and the oil sump areas of the bearing case. The rotor should be held in place by an overhead hand hoist.

Coat the journal and the bearing fit in the lower ha lf of the case with oil or STP. Place the lower half of the bearing shell on top of the journal.Check alignment of the oil supply hole in the case with the position of the oil supply in the bearing shell. Align the bearing fit in the case with the shell O.D. and roll the bearing into the lower half of the case. 

It may be necessary to lift the rotor slightly to allow the bearing shell to roll in easily.  Monitor the position of the temperature sensor lead wires when rolli ng in the bearing to insure that the wire is not crimped or twisted.

With the bearing in the lower half of the bearing case, use a rubber head mallet to align the bearing shell split with the housing split.  Both sides of th e bearing should align flat with the case.Once the bearing to case split lines are correct, lower the shaft onto the bearing.

Verify that the anti-rotation dowels in the bearing shell lower half are aligned with the dowel holes in the shell upper half. Gently lower the top half of th e bearing onto the lower half.  Check for any stand off between the two bearing halves.  Do not attempt to tighten the split line bolts if the two halves are not flush.Check for the cause of the standoff a nd correct. Install the bearing split line bolts and tighten securely.

It is recommended that a crush check be done to verify a proper bearing to case fit. Place shims

.005"/.010" thick along the case split line on either side  of each bolt location. Lay a strip of plastigage or lead wire parallel to the axis of the machine on  the top of the bearing shell.  The standard design specification for the bearing shell crush is metal-to-m etal to .002" interference.  The plastigage should be chosen such that the thickness of the shims at the case split line falls in the middle of the plastigage range.

Install the bearing cap or strap and tighten all split line bolts. After the bearing cup has been seated, remove the cap and inspect the plastigage.  The pl astigage should indicate a thickness equal to or less than the shim thickness used at  the split line. The amount of interference is equal to the difference between the indicated clearance and the shim thickness.

Once the proper crush is confirmed, the bearing clearance should be checked. Place the base of two dial indicators on a portion of the machine unaffected by rotor or bearing movement, such as the bearing case horizontal joint. Place one of the indicator's  styluses on top of the shaft near the bearing.It is important that this stylus be placed at th e top dead center of the shaft to obtain an accurate reading. Place the other indicator's stylus on top of the bearing shell. Slowly lift the rotor noting the shaft rise on the appropriate indicator. Be careful not to raise the rotor into an internal obstruction.Do not lift the rotor more than twice the set clearance.

Observe the indicator on the bearing as the shaft is slowly lifted.  Once the bearing lifts, as indicated by the dial indicator, stop lifting the shaft. The lift is the difference between the two indicator readings.Note that the lift with tilt pad bearings  will always be more than the actual bearing set clearance due to shaft movement between pads. Multiply the indicated lift clearance by the following values, depending on the configuration of the bearing:  

 

Bearing Configuration               Lift Check Correction Factor 

3 Pad                               .667

4 Pad                               .707

5 Pad                               .894

6 Pad                                 1

 

After the clearance has been check ed, install the bearing cap and tighten the split line bolts on the

bearing.

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