Where it is fitted ?
Between flywheel & engine end rest on tank top & is connected solidly with the engine bedplate.
Purpose
To prevent axial movement of the crankshaft which would result from the thrusting effort of the screw propeller.
It is designed that the total thrust is conveyed to the hull of the ship by the lower half casting.
Components of Thrust Bearing?
Thrust shaft
Collar
Bearing pad (forward & aft)
Pad carriers
Adjusting liner (or) distance piece
Why pivot line on pads provided ?
For to tilt & to form wedge shaped film between the faces of collar and the pad.
How will you check clearance ?
1) Remove top covered
2) Insert a feeler gauge between face of collar and the pad (both ahead & astern) take the reading
3) Force the shaft aft by means of a screw jack placed between casing and the back of the coupling until the collar is hard up on the pads.
4) Check position of the shaft is truly central in the journal bearings.
5) Test also that both liners are bearing equally on the casing.
6) Take a micrometer (a dial gauge) reading of the shaft position.
7) Repeat this operation, moving the shaft forward, and take a second micrometer reading.
8) The difference in the two readings is the total clearance. (about 1 mm being typical)
9) If clearance is excessive or less, it can be adjusted by subtracting or adding shims to the distance pieces on the back of the pad carriers.
Feelers can be used as an alternative between thrust ring and casing. Use of feelers in the thrust pad/collar gap is likely to cause damage and may give a false reading.
The radial clearance of the journal bearing can be measured by taking lead reading or roughly by means of a feeler gauge after removing oil seal on the end cover.
Axial clearance = 1 to 2 mm
Radial clearance = 0.5 to 0.8 mm for 440 mm diameter
Advantages of Tilting Pad Bearing
Have ability to absorb, change in direction of load, more readily
Have greater flexibility to absorb shaft deflection or misalignment
Tilting of pads, allow oil to form wedge shaped film, between faces of collar and pads.
Wedge shaped oil film prevents metallic friction and enables the thrust pads to carry loads.
Disadvantages
Each pad in a set must be exactly the same thickness and even a ‘thou’ difference might result in a single pad carrying the entire load, thus increasing the risks of failure.