crankshaft,main bearings & shaft alignment lesson two
TRANSCRIPT
CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT
LESSON TWO
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. 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. 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 )
1.4 MANUFACTURING
Solid forged built in a single piece ( small-slow speed engines )
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
1.4 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
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
1.4 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
2. MAIN BEARINGS / CRANKSHAFT BEARINGS
2.1 LOCATION
In the transverse saddles of the bedplate.
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. 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 )
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 );
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 );
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 );
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 )
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 )
2.4 PARTS
Upper & lower shells (fitted in bedplate seating / saddle )
2.4 PARTS
Upper & lower shells (fitted in bedplate seating / saddle )
Thrust bolts
Covers
Shims ( for adjusting vertical bearing play )
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 )
2.4 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
2.6.2 Adjustment
This can be taken up by reducing the thickness of shims between the bearing butts and the housing.
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
2.7.1 Indications
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
2.7.1 Indications
increased temperature
slight oil pressure drop ( sometimes followed by noise )
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
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 )
3. CRANKSHAFT ALIGNMENT
Crankshafts are aligned to determine load reactions on each bearing. This is done by laser tehnicques and computer calculations.
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
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
3.1.1 Frequency
Once a year
After replacing the main bearing
If the ship has grounded
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
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 betwee the webs.
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
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 betwee the webs.
Measurements are taken at TDC, BDC and two horizontal web positions.
3.1.3 Misalignment
Wear of main bearings;
Distortion of engine bedplate transverse members;
Damage to supporting ship’s structure.
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.
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.
3.1.3 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 engine crankshaft deflection report;
Main / auxiliary engine crankshaft deflection record;
Crankshaft and engine bearing data sheet.