Saturday, December 21, 2019

PITTING EROSION OF MAIN BEARINGS:

1.ONE POSSIBLE CAUSE IS "SPARK EROSION"

2.IN THE EARLY STAGES SPARK EROSSION APPEARS AS
 SMALL PITTING EROSION.
 LATER, AS ROUGHNESS INCREASES, THE SMALL CRATERS WILL
 SCRAPE OFF AND PICK UP WHITE METAL (THE LATTER
 GIVES A SILVERY WHITE APPEARANCE TO THE BEARING).

3.SPARK EROSION IS CAUSED BY A VOLTAGE DISCHARGE
 BETWEEN JOURNAL & BEARING.

4.THE CRANKSHAFT IS ELECTROSTATICALLY CHARGED WHEN
 THE ENGINE IS RUNNING. TO ENSURE PROTECTION AGAINST
 SPARK EROSION AN EARTHING DEVICE IS USUALLY FITTED
 ON THE INTERMEDIATE SHAFT.

5.THE EARTHING DEVICE CONSISTS OF THE FOLLG:
 -A CLAMP WITH A COPPER LINING.
 -CARBON BUSHES WHICH ARE PRESSED ON THE COPPER
 LINING WITH SPRINGS.
 -CABLE CONNECTING CARBON BUSH TO SHIP'S HULL

6.IF SUCH AN EARTHING DEVISE IS ALREADY FITTED
 CHECK ALL THE COMPONENTS AND THEIR CONNECTIONS AS
 MENTIONED IN PARAGR. 5.

7.IF THE SHAFT IS NOT FITTED WITH EARTHING DEVICE  
 THEN PLS ADVISE INTERMEDIATE SHAFT DIAMETER.

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