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Bearing Failure

Fleet QHSE Alert

ENGINE ROOM MAINTENANCE

No. 001 1st September 2001

Over the years, we have had a few instances of damage toauxiliary engine main bearings and connecting rod bottom

end bearings. This has almost always resulted in damage ofcrankshaft beyond repair, necessitating expensive renewals.

Your attention to the following would greatly help reduce

such break-downs:

Routine Operation of the Engine

1. Follow correct starting and stopping procedures.

2. Lube oil pressure of approximately 1.0 Bar must bemaintained continuously by means of hand pump or elec-

tric priming pump during starting, until the engine drivenpump builds up a pressure exceeding this. Similarly,

lube oil pressure must be maintained during the stoppingof the engine and for a few minutes thereafter.

3. Maintain the lube oil in good condition and carry out

weekly drop tests as a test of oil quality. Check andclean lube oil filters periodically and ensure that filters

and coolers are purged after any work is done on them.

4. When carrying out crankcase inspections, verify properlube oil flow. Remember to check for correct end float

of bottom end of the connecting rods.

Engine Overhauls

1. In view of a large number of cases of bottom end bearing

bolt failure due to incorrect tightening torque, Yanmar

and Daihatsu have revised their procedures for tighteningbottom end bolts from the torque method to the rotatedangle method which require preliminary tightening by

torque and further tightening through a specified angle.

Bearing white metal wiped out . Melted down bearings

due to lube oil failure

Confirm that you have the makers updated instruc-tions onboard, and a torque wrench of the appropriate

range.

2. Connecting rod bottom end bores should be accuratelycalibrated to ensure that the inner diameter is above the

minimum allowable figure and that the ovality is

within limits. The connecting rods should be calibratedwithout the bearing shells in place, only after tighten-ing the bottom end bearing bolts as specified by the

makers.

3. Carry out dye penetrant crack detection tests on the

serrations of bottom end bearing keeps and on thethreaded section of the bottom end bearing bolts.Check for burrs and distortion at the serrations of the

bearing keeps, and at the threaded sections and landing

faces or fitted sections of the bolts. Some makers rec-ommend checking the bolts for elongation.

4. Outer diameters of crankpins should be measuredalong two perpendicular axes, at three locations alongthe pin.

5. Maintain a proper record of the service hours of the

bottom end bearing bolts and should these be ap-proaching the makers recommended replacement inter-

vals, ensure that the bolts are renewed during the over-haul.

6. When using new bolts, it is important to break-in the

bolts by tightening and loosening them in the connect-

ing rods a couple of times.

7. When connecting rod bottom end bearing bolts are

being re-used, please ensure that they are fitted in thesame location from which they were removed.

8. Only use recommended lubricants/ anti-seize com-

pounds on the bolt threads before tightening.

9. Check for correct end float of bottom end of the con-

necting rods after these are fitted in the engine.

10. Ascertain the zero error of all calibration instru-ments used, and take this into account as appropriate.

IF IN DOUBT, ASK US!