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8/9/2019 Powertrain Alignment
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Chris LeontopoulosChris Leontopoulos
Shaft AlignmentShaft Alignmentandand
Powertrain VibrationPowertrain Vibration
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Shaft Alignment
Definition
Most shipboard configurations of shafts
and bearings are likely to be aligned whensome or all of the centrelines of the bearingsare offset from the theoretical straight linecondition, so as to achieve an acceptablebearing load distribution and shaft slope.
Design Process
The classic alignment technique wouldinvolve the calculation of the bearing
reactions following a quasi-static analysisand varying of the bearing offsets until anacceptable set of bearing reaction loads andshaft slope is achieved.
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Influence Parameters on Shaft Alignment
1. Bearing offsets
2. Thermal Effects
3. Loads (propeller, gear)
4. Crankshaft model
5. Hull Flexibility
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Case Studies
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Design Trends
1. Increased engine power and reduced rpm
2. Increased propeller weight and efficiency
3. Shorter shafts (except container vessels)
Hence, increased bending moments and stiffness and sensitivity on
bearing influence coefficients
1. Changes in propeller design
2. Changes in hull design
3. Increased propeller weights
Hence, increased propeller loads, which affect shaft slope and henceslope boring
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Bulk Carrier Chemical
Carrier
Container
Carrier
General
Cargo
Carrier
High Speed
Craft
Offshore
Supply
Vessel
Oil Carrier Passenger
Vessel
Special
Purpose
Vessel
Tug Yacht
z
Alignment Related Failure Statistics
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Stern Tube Bearing
Stern tubebearingdamage
White Metal Bearing Damage
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Stern Tube Bearing
Teflon Bearing Damage
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Alignment Related Failures
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The alignment process is critical as it involves highrisk consequences, which usually immobilise thevessel.
ABS possesses extensive practical and designexperience on shaft alignment.
Shaft Alignment
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The simply supported beam
g
Shaft Alignment Fundamental Principles
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The simply supported beam
g
Shaft Alignment Fundamental Principles
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IntroductionIntroduction
Demonstrate AVI
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Dry Dock
In Service -Waterborne
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Positioning the Bearings to Actual Design Values
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Optical/Laser/Telescope
Alignment Procedure
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Alignment Procedure
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Critical Areas
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Stern Tube Bearing Alignment
Ideal contact
between theshaft and thebearing
Edge contact.
Desired: Even load distributionthroughout the bearinglength.
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Shaft Alignment Analysis
Modelling of the bearingreaction
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Propeller operation in wake
field behind the ship
Propeller Loads
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Alignment Acceptance Criteria
1. Bearing loads (force, pressure)
a) 8 bar white metal
b) 6 bar synthetic material
c) 5.5 for water lubricated
2. Relative shaft slope inside stb bearing:
a) 0.3 mrad then slope boring is required
3. Engine Flange bending moments in accordance withmanufacturers limits
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Alignment Analysis ABS Capabilities
Shaft Alignment Analysis
Optimization for Shaft Alignment
Alignment Investigation
Hull Deflection Shaft Alignment
Interaction
Shaft Alignment Analysis
Shaft Alignment Procedure
Expertise in Installation and Build
Process
ABS Capabilities Shipyard Capabilities
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Sterntube Frame Boring
Vertical / Horizontal boring of
Stern tube frame
Alignment Procedure
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Reactions Measurements
Bearing reactions aremeasured directly or
indirectly or both. Themost commonly appliedmethods that measure thealignment condition are:
Gap and Sag
Jack-up
Strain gauge method
The Sag and Gap
and the strain
gauge procedures
are indirect methodsto measure the
deflections and
correlate shaft
strain to the
bearing reactions,in a reverse
en ineerin wa .
Alignment Procedure
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Jack up method
Lifting curve
Lowering curve
Hysterisis: difference in
jack load between lifting
and lowering
Resultant line - average
between lifting and
lowering curve.
Bearing reaction is then:
mm
Alignment Procedure
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Correlation between measurements anddesign calculation is top priority
Shaft Alignment Correlation
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Strain Gauges
Alignment Procedure
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Strain Gauge Installation Procedure
Alignment Procedure
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Strain Gauge Installation Procedure
Alignment Procedure
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Strain Gauge Installation Procedure
Alignment Procedure
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Shafting Alignment Measurements
Problems with alignment verification are often related toour ability to have control over the following:
accuracy and reliability of the applied alignment procedure
reliability of the alignment calculation (modeling, loads,..)
ability to control factors which may affect/change the presetalignment parameters (stern tube bearing slope angle,bearing offset, etc.)
accuracy of the applied alignment verification methodalignment condition monitoring
skills of the engineers conducting alignment procedure and
measurement ability to validate measurement method and obtained results
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Crankshaft deflection measurements
Indirect Indications of Misalignment
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ShaftEccentricitydiagnosedthroughvibrationmonitoring
Axial
Radial
Tangential
Indirect Indications of Misalignment
D i M
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Dynamic Measurements
D i M t
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Dynamic Measurements
D i M t
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Dynamic Measurements
D i M t
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Dynamic Measurements
D i M t
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Dynamic Measurements
Hull Deflection
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Hull Deflection
ABS have established correlation among hulldeflections and use the same data to predict
the hull deflections of the newly designedvessel of the same type.
Collected data is to be applied in the ABSShaft Alignment Optimization software to
provide a basis for more robust shaftalignment design, which will be lesssusceptible to the alignment condition changeduring the operation of the vessel.
Hull Deflection
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Hull Deflection
Shaft Alignment Analysis
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Shaft Alignment Analysis
Refined FE model of the stern structures
Shaft Alignment Analysis
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Shaft Alignment Analysis
Alignment optimisation
Optimised shaft line
Shaft Alignment Analysis
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Shaft Alignment Analysis
Alignment optimisation
Shaft Alignment Analysis
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Shaft Alignment Analysis
Alignment optimisation
Powertrain Vibration
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ABS possesses extensive practicaland design experience on vibrationof marine powertrains.
Powertrain Vibration
Vibration Acceptance Criteria
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Vibration Acceptance Criteria
1. Torsional Stress limits (IACS)
2. Lateral and Axial Vibration
3. Torsio-axial Vibration (direct drives)
IntroductionIntroduction
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IntroductionIntroduction
Demonstrate AVI
Torsional VibrationTorsional Vibration
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Torsional VibrationTorsional Vibration
Torsional Vibration Barred Speed Range
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Torsional Vibration Barred Speed Range
Torsional Vibration
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Powertrain componentsaffected by torsional
vibration
Torsional Vibration
Torsional Vibration
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VIBRATION FAILURE
Torsional Vibration
Lateral Vibration
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VIBRATION FAILURE
Lateral Vibration
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Coupling bolts
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Vibration Training using the Rotor-kit
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Practical Vibration Problems
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propeller induced vibration,
engine misfire,
barred speed range,
gear hammer,
coupling bolts failure,
crankshaft failure,
bearing failure,
tailshaft torsional fracture
vibration due to misalignment
propeller cavitation shaft whirling
and many more
Within the Classification Rules and beyond we havetackled a variety of powertrain vibration problems
and issues, such as:
Shaft Alignment and Powertrain Vibration
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ANSWERSANSWERS
&&
Thank you for your attention
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