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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