1. CRANKSHAFT, MAIN BEARINGS & SHAFT ALIGNMENT

2. 1.CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT 1.1 DEFINITION OF A CRANKSHAFT The crankshaft converts reciprocating motion in the cylinder into rotary motion of the propeller shaft.

4. 1.CRANKSHAFT, MAIN BEARINGS & SHAFT ALIGNMENT 1.2 PARTS The crankshaft is made up of throws and journals. A throw consists of a pin ( secured or attached to big / bottom end bearings ) and two webs or cranks. Journals rest or lie in the main bearings.

6. 1.CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT 1.3 STRESSES  Bending ( when the piston is at TDC );  Shear stress ( in operation );  Torsion ( due to speed change, i.e. acceleration & deceleration )

7. 1.4 MANUFACTURING  Solid forged built in a single piece ( small engines )

10. 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.

12. 1.5 MATERIALS  Carbon steel  Alloy of nickel, chromium & molybdenum  Specially alloyed grey cast steel 1.6 ARRANGEMENT OF CRANKS Multi-throw shaft to provide for the engine firing order

13. 2. MAIN BEARINGS / CRANKSHAFT BEARINGS 2.1 LOCATION In the transverse saddles of the bedplate.

15. 2. MAIN BEARINGS / CRANKSHAFT BEARINGS 2.1 LOCATION In the transverse saddles of the bedplate. 2.2 PURPOSE To provide support for the crankshaft 2.3 MATERIAL ( multilayer bearings ) Used for crankshaft bearings and connecting rod big end bearings

20. 2. MAIN BEARINGS / CRANKSHAFT BEARINGS 2.1 LOCATION In the transverse saddles of the bedplate. 2.2 PURPOSE To provide support for the crankshaft 2.3 MATERIAL ( multilayer bearings )  Steel support shell ( basic element );  Bearing metal ( white metal, copper-lead or aluminium-tin alloy, leaded bronze );  Nickel barrier ( separating the two layers );  Galvanized layer ( good running-in and dry running properties )  Anti-corrosion layer ( lead or indium )

22. 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )

28. 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )  Thrust bolts  Covers  Shims ( for adjusting vertical bearing play ) 2.5 LUBRICATION Pressure lubricated ( low pressure ) 2.6 CLEARANCE 2.6.1 Measurement  lead wire  wear gauge / bridge gauge  feeler gauge  “ kjaer “ feeler

29. 2.7 BEARING DAMAGES 2.7.1 Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise ) 2.7.2 Kinds  Squeezing of the overlay / white metal ( problems with oil film formation );  Fatigue cracking ( due to poor quality, shaft misaligment or local overload );  Dislodgement of overlay or white metal ( due to cracking );  Scoring ( striation due to presence of hard particles );  Wiping ( misshaped overlay or white metal due to high temperature )

31. 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser techniques and computer calculations. 3.1 CHECKS 3.1.1 Frequency  Once a year  After replacing the main bearing  If the ship has grounded 3.1.2 Techniques The deflections are measured through one revolution of the crankshaft by inserting a dial gauge / dial indicator gauge between the webs. Measurements are taken at TDC, BDC and two horizontal web positions.

36. 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure. 3.1.4 Consequences Hogging is closing of the crank throw at TDC.

38. 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure. 3.1.4 Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC.

40. 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure. 3.1.4 Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC. 3.1.5 Reports  Main / auxiliary engine crankshaft deflection record;  Crankshaft and engine bearing data sheet.