Explain the procedures of stern tube alignment checks in dry dock

• Dial gauge for radial direction:

o This gauge is set up to measure the radial movement of the shaft. Radial direction reefers to a direction that radiating out from the center of the shaft

o It is important to measure this to ensure that the shaft is perfectly centered & there is no excessive play or wobble which would indicate misalignment

• Dial gauge for radial direction (On another point):

o This second dial gauge is measuring the radial displacement likely at different point along the shaft to measure consistency in shaft alignment throughout its length

• Dial gauge for axial direction:

o the axial direction is along the length of the shaft. This gauge measures the end play or axial movement of the shaft. It is crucial to measure that the shaft doesn’t move too much back and forward along its length, which could affect in the operation of the seal and further lead to leak or wear

In a stern tube seal alignment check gauges would be used as follows:

• The dial gauges are positioned at a specific point on the stern tube and propeller shaft

• The shaft then to be rotated and the reading to be observed at the dial gauge

• By reading the gauges we can determine if there is any misalignment in the shaft. This is determined by looking for variations in the variations of the reading which would indicate that the shaft is not perfectly round or is not seated centrally within the stern tube.

• Any misalignment can lead to excessive wear in the seal & bearing and potentially lead to seal failure

• Therefore, it is crucial to adjust the alignment until the reading on the dial gauges are within acceptable limits as specified by the manufacturer.

Note: In case adjusting liner eccentrically by turning shaft isn’t available, then even clearance between liner bore and shaft surface by using feeler gauge must be achieved.