crankshaft, main bearings and shaft alignment
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Crankshaft, Main Bearings and Shaft Alignment
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.
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 ... ....
Crankshaft, Main Bearings and Shaf Alignment
(text)
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.
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 ... ....
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.
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.
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.
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.
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.
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.
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 diesel4. Slow speed diesel5. 4. 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?
CRANKSHAFT, MAIN BEARINGS AND SHAFT ALINGNMENT
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.
LESSON TWO
Crankshaft, Main Bearings and Shaf Alignment
1. CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT
1. CRANKSHAFT,MAIN BEARINGS & SHAFT ALIGNMENT
1.1 DEFINITION OF A CRANKSHAFT
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
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 )
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 );
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 );
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
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.
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
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
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
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. MAIN BEARINGS / CRANKSHAFT BEARINGS
2.1 LOCATION
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
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 )
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
2.4 PARTS
Upper & lower shells (fitted in bedplate seating / saddle )
2.4 PARTS
Upper & lower shells (fitted in bedplate seating / saddle )
Thrust bolts
2.4 PARTS
Upper & lower shells (fitted in bedplate seating / saddle )
Thrust bolts
Covers
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
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
2.4 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
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
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
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
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
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
2.6.2 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
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
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 );
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 );
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 );
Scoring ( striation due to presence of hard particles );
Wiping ( misshaped overlay or white metal due to high temperature )
3. CRANKSHAFT ALIGNMENT
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
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
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
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
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
3.1.3 Misalignment
Wear of main bearings;
3.1.3 Misalignment
Wear of main bearings;
Distortion of engine bedplate transverse members;
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
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
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;
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;
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.
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