Plain Bearing Failure - Loss of clearance in tilting-pad journal bearing at start-up

PLAIN BEARING FAILURE

Plain bearing failure index

1.0 Lubrication breakdown

Lubrication breakdown index

1.3 Loss of clearance in tilting-pad journal bearing at start-up

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	Loss of clearance in five pad, tilting-pad journal bearing at high-speed start-up causing wiping at the centres of all the pads
Main Characteristics	Small patch of wiping in centre of all of the pads.
Cause	Establishment of thermal equilibrium in a tilting-pad journal bearing takes some time because of the restricted thermal path through the pad pivots. With rapid start-up, sufficient radial thermal expansion can occur in the pads to take up the radial clearance, preventing the formation of a hydrodynamic lubricating film and causing wiping at the centres of the pads. For more information on causes of lubrication breakdown and possible actions to take, see Lubrication breakdown - Summary
Note	All or most pads are wiped, but those in the direction of loading may be more heavily wiped than others.
Possible Confusion with Other Types of Damage	Wiping during "normal" operation (e.g. due to vibration) would tend to wipe more of the pad area than just the centre at the position of the pad supports.
Comment	This type of failure can be avoided by extending the run up time to full speed or by increasing the radial clearance in the bearing if this is acceptable for the performance of the bearing for the normal operating conditions.