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Crankshaft, Main Bearings and Shaft Alignment.

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1 Crankshaft, Main Bearings and Shaft Alignment

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4 The crankshaft, which converts the reciprocating motion of the piston to rotating motion, must resist the bending stresses caused by the connecting rod thrust when the piston is at top centre. Then the maximum gas pressure acts straight down on the crankpin and tends to bend the shaft between the adjacent bearings. The crankshaft must also withstand the torsional forces produced by the change of speed.

5  The crankshaft converts to  It must resist the bending stresses caused by the connecting rod thrust when  Then the maximum gas pressure acts straight down on the crankpin and tends to  The crankshaft must also withstand the

6 Crankshaft, Main Bearings and Shaf Alignment (text)

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8 Medium speed engines have crankshaft usually solid forged, i.e. made from a single piece, while slow speed engine crankshafts are mostly of semi-built design with crankpins and webs forged or cast in one piece and shrunk on to the journals. The type of steel used, which is carbon or alloy steel containing nickel, chromium and molybdenum, is chosen for its strength, resistance to fatigue and hardness of bearing surface.

9  Medium speed engines have crankshaft usually solid forged, i.e. made......,  Slow speed engine crankshafts are mostly of semi-built design with  They are... or... in one piece and... on to the journals.  The type of steel used for crakshafts is  It contains nickel,... and must be resistant to

10 The cranks of a multi-throw shaft are set at appropriate angles giving a “firing order” for the engine. The firing order is chosen primarily to obtain a smooth torque and the best mechanical balance. However, main bearings loads, exhaust arrangements suitable for turbocharging and torsional vibration may also be taken into account. Although the crankshaft appears to be robust, they rely on the main bearings to develop their full strength.

11  cranks of a multi-throw shaft are set at appropriate angles giving  The firing order is chosen primarily to obtain and  However, we must also take ito account: ◦... loads, ◦ exhaust arrangements suitable for... and ◦  Crankshaft rely on the to develop their full strength.

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13 When a crankshaft has to be handled outside the engine, it should be carefully supported to avoid high bending moments on it by its own weight. In the engine it is essential to ensure that the bearings carrying it are in good alignment, as bearing misalignment will cause the crankshaft to bend and eventually break it.

14 When a crankshaft has to be handled outside the engine, it should be carefully supported to _____ high bending moments on it by its own weight. In the engine it is essential to ensure that the bearings carrying it are in ______ alignment, as bearing misalignment will ______ the crankshaft to bend and eventually break it.

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16 The main bearing shells are made of steel with a lining of bearing metal which can be white metal, copper-lead or aluminium-tin alloy. A thin flash of lead or indium is often added to provide a layer giving protection against corrosion. The shells are held in position and shape by seatings of the bedplate or frame.To ensure efficient and reliable operation the crankshaft should be checked periodically for alignment by measuring the deflection of the webs.

17 The main bearing shells are made... steel with a lining... bearing metal which can be white metal, copper-lead... aluminium-tin alloy. A thin flash of lead or indium is often added... provide a layer giving protection... corrosion. The shells are held... position and shape by seatings of the bedplate or frame.... ensure efficient and reliable operation the crankshaft should be checked periodically... alignment by measuring the deflection... the webs.

18 1. State the function of the crankshaft. 2. What forces is a crankshaft subjected to? 3. What kind of crankshafts arer used in: a) Medium speed diesel 4. Slow speed diesel What does the choice of steel type for crankshaft depend on? 6. What is the “firing order”? 7. What else is taken into consideration in designing a crankshaft? 8. Why should special care be taken when handling crankshafts outside the engine? 9. How are the main bearing shells protected from corrosion? 10. How are crankshafts positioned in the engine with respect to their connection to the shaft? 11. What is a journal bearing? What other types of bearings do you know? 12. What is the function of the webs? 13. How are the main bearings examined for possible wear?

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20 CRANKSHAFT, MAIN BEARINGS AND SHAFT ALINGNMENT

21  The crankshaft, which converts the _________ motion of the piston to rotating motion, must resist the _________ stresses caused by the connecting rod _________ when the piston is at top centre.  Then the maximum gas pressure acts straight down on the _________ and tends to bend the shaft between the adjacent _________. The crankshaft must also _________ the torsional forces produced by the change of speed.  Medium speed engines have crankshaft usually solid _________, i.e. made from a single piece, while slow speed engine crankshafts are mostly of semi-built design with crankpins and _________ forged or cast in one piece and shrunk on to the _________. The type of steel used, which is carbon or alloy steel containing nickel, chromium and molybdenum, is chosen for its strength, resistance to _________ and hardness of bearing surface.

22 LESSON TWO Crankshaft, Main Bearings and Shaf Alignment

23 1.CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT

24 1.1 DEFINITION OF A CRANKSHAFT

25 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.

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27 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. 1.2 PARTS

28 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. 1.2 PARTS The crankshaft is made up of throws and jurnals. A throw consists a pin ( secured or attached to big / bottom end bearings ) and two webs or crancks. Jurnals rest or lie in the main bearings.

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30 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. 1.2 PARTS The crankshaft is made up of throws and jurnals. A throw consists a pin ( secured or attached to big / bottom end bearings ) and two webs or crancks. Jurnals rest or lie in the main bearings. 1.3 STRESSES ( fluctuating )

31 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. 1.2 PARTS The crankshaft is made up of throws and jurnals. A throw consists a pin ( secured or attached to big / bottom end bearings ) and two webs or crancks. Jurnals rest or lie in the main bearings. 1.3 STRESSES ( fluctuating )  Bending ( when the piston is at TDC );

32 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. 1.2 PARTS The crankshaft is made up of throws and jurnals. A throw consists a pin ( secured or attached to big / bottom end bearings ) and two webs or crancks. Jurnals rest or lie in the main bearings. 1.3 STRESSES ( fluctuating )  Bending ( when the piston is at TDC );  Sheer stress ( in operation );

33 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. 1.2 PARTS The crankshaft is made up of throws and jurnals. A throw consists a pin ( secured or attached to big / bottom end bearings ) and two webs or crancks. Jurnals rest or lie in the main bearings. 1.3 STRESSES ( fluctuating )  Bending ( when the piston is at TDC );  Sheer stress ( in operation );  Torsion ( due to speed change, i.e. acceleration & deceleration )

34 1.4 MANUFACTURING

35  Solid forged built in a single piece ( small-slow speed engines )

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38 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.

39 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals

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42 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS

43 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS  Carbon steel

44 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS  Carbon steel  Alloy of nickel, chromium & molibdenum

45 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS  Carbon steel  Alloy of nickel, chromium & molibdenum  Specialy alloyed grey cast steel

46 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS  Carbon steel  Alloy of nickel, chromium & molibdenum  Specialy alloyed grey cast steel 1.6 ARRANGEMENT OF CRANKS

47 1.4 MANUFACTURING  Solid forged built in a single piece ( small-slow speed engines )  Semi-built design ( large medium-speed engines ). Crankpins & webs are forged or cast in one piece and shrunk on to the journals.  Fully-built ( cast in single piece – webs are shrunk on to the crankpins and journals 1.5 MATERIALS  Carbon steel  Alloy of nickel, chromium & molibdenum  Specialy alloyed grey cast steel 1.6 ARRANGEMENT OF CRANKS Multi-throw shaft to provide for the engine firing order

48 2. MAIN BEARINGS / CRANKSHAFT BEARINGS

49 2.1 LOCATION

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

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52 2. MAIN BEARINGS / CRANKSHAFT BEARINGS 2.1 LOCATION In the transverse saddles of the bedplate. 2.2 PURPOSE

53 2. MAIN BEARINGS / CRANKSHAFT BEARINGS 2.1 LOCATION In the transverse saddles of the bedplate. 2.2 PURPOSE To provide support for the crankshaft

54 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 )

55 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 ( 4 stroke engines )

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60 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 ( 4 stroke engines )  Steel support shell ( basic element );

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62 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 ( 4 stroke engines )  Steel support shell ( basic element );  Bearing metal ( white metal, copper-lead or aluminium-tin alloy, leaded bronze );

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64 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 ( 4 stroke engines )  Steel support shell ( basic element );  Bearing metal ( white metal, copper-lead or aluminium-tin alloy, leaded bronze );  Nickel barrier ( separating the two layers );

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66 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 ( 4 stroke engines )  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 )

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68 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 ( 4 stroke engines )  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 )

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72 2.4 PARTS

73  Upper & lower shells (fitted in bedplate seating / saddle )

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79 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )  Thrust bolts

80 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )  Thrust bolts  Covers

81 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )  Thrust bolts  Covers  Shims ( for adjusting vertical bearing play )

82 2.4 PARTS  Upper & lower shells (fitted in bedplate seating / saddle )  Thrust bolts  Covers  Shims ( for adjusting vertical bearing play ) 2.5 LUBRICATION

83 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 )

84 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

85 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 Measurement

86 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 Measurement  lead wire

87 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 Measurement  lead wire  wear gauge / bridge gauge

88 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 Measurement  lead wire  wear gauge / bridge gauge  feeler gauge

89 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 Measurement  lead wire  wear gauge / bridge gauge  feeler gauge  “ kjaer “ feeler

90 2.6.2 Adjustment

91 This can be taken up by reducing the thickness of shims between the bearing butts and the housing.

92 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES

93 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications

94 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature

95 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise )

96 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise ) Kinds

97 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise ) Kinds  Squeezing of the overlay / white metal ( problems with oil film formation );

98 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise ) Kinds  Squeezing of the overlay / white metal ( problems with oil film formation );  Fatigue cracking ( due to poor quality, shaft misaligment or local overload );

99 2.6.2 Adjustment This can be taken up by reducing the thickness of shims between the bearing butts and the housing. 2.7 BEARING DAMAGES Indications  increased temperature  slight oil pressure drop ( sometimes followed by noise ) 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 );

100  Scoring ( striation due to presence of hard particles );

101  Wiping ( misshaped overlay or white metal due to high temperature )

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103 3. CRANKSHAFT ALIGNMENT

104 Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations.

105 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS

106 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency

107 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency  Once a year

108 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency  Once a year  After replacing the main bearing

109 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency  Once a year  After replacing the main bearing  If the ship has grounded

110 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency  Once a year  After replacing the main bearing  If the ship has grounded Techniques

111 3. CRANKSHAFT ALIGNMENT Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations. 3.1 CHECKS Frequency  Once a year  After replacing the main bearing  If the ship has grounded Techniques The deflections are measured through one revolution of the crankshaft by inserting a dial gauge / dial indicator gauge betwee the webs.

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

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117 3.1.3 Misalignment

118  Wear of main bearings;

119 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;

120 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure.

121 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences

122 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC.

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124 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC.

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126 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC Reports

127 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC Reports  Main engine crankshaft deflection report;

128 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC Reports  Main engine crankshaft deflection report;  Main / auxiliary engine crankshaft deflection record;

129 3.1.3 Misalignment  Wear of main bearings;  Distortion of engine bedplate transverse members;  Damage to supporting ship’s structure Consequences Hogging is closing of the crank throw at TDC. Sagging is opening of the crank throw at TDC Reports  Main engine crankshaft deflection report;  Main / auxiliary engine crankshaft deflection record;  Crankshaft and engine bearing data sheet.


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