Guidance Notes on Propulsion Shafting Alignment GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT APRIL 2006 (Updated February 2014 – see next page) American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 Copyright  2006 American Bureau of Shipping ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Updates February 2014 consolidation includes: • April 2006 version plus Corrigenda/Editorials Foreword Foreword The mission of the American Bureau of Shipping (ABS) is to serve the public interest, as well as the needs of its clients, by promoting the security of life, property and the natural environment primarily through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities. The Rules and Guides on which classification is predicated are established from theoretical and empirical principles of naval architecture, marine engineering and other engineering principles that have proven satisfactory by service experience and systematic analysis. The classification Rules are not intended to address every single aspect of the vessel design, but rather to indicate the minimum set of criteria which will ensure safety and functionality of all vital components of the vessel, and at the same time provide sufficient space to the industry to accommodate their practices and technologies with minimum constraints from regulatory bodies. However, in situations where the complexity of the problem results in conflicting interpretation of regulations and when the consequence of this disparity results in damage to the equipment and affects vessel’s safety, additional regulation clarification and guidance may be necessary. The case of shaft alignment is an example of where ABS has noticed the need to provide a more detailed explanation on alignment design and practices, which has resulted in the development of the subject Guidance Notes. These Guidance Notes have been developed primarily to clarify the subject matter for ABS field inspectors and design review engineers to ensure consistency of the survey and plan approval process. Moreover, the subject guidelines may help the industry to improve its approach towards shaft alignment analyses and procedures. Additionally, ABS has developed state of the art analytical tools primarily for the purpose of engineering analysis and design. The ABS shaft alignment program, combined with alignment optimization software, is capable of analyzing complex propulsion installations and, when used as design tool, may provide an optimal solution to the alignment problem. We welcome your feedback. Comments or suggestions can be sent electronically to [email protected]. . ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 iii Table of Contents GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT CONTENTS SECTION 1 Introduction ............................................................................................ 1 1 Propulsion Shaft Alignment ................................................................. 1 2 Objective ............................................................................................. 2 3 The Alignment Problem ...................................................................... 3 3.1 Solution to Alignment Problem ........................................................ 4 3.2 Analytical Support ............................................................................ 4 4 Modern Vessel Design ........................................................................ 5 5 Rule Requirements ............................................................................. 5 SECTION 2 Shaft Alignment Design and Review .................................................... 7 1 General ............................................................................................... 7 2 Review vs. Design .............................................................................. 7 3 Review ................................................................................................ 8 3.1 Plans and Particulars Required ....................................................... 8 3.2 Shaft Alignment Model ..................................................................... 9 3.3 Scope of Calculation ........................................................................ 9 3.4 Results Verification ........................................................................ 10 3.5 Documenting the Review ............................................................... 17 4 Design ............................................................................................... 18 4.1 General .......................................................................................... 18 4.2 Stern Tube Bearing ........................................................................ 18 4.3 Stern Tube Bearing Contact Modeling ........................................... 22 4.4 Crankshaft Modeling ...................................................................... 27 4.5 Applying a Partial Equivalent Model of the Crankshaft .................. 31 4.6 Engine Bearing Misalignment ........................................................ 33 4.7 Bearing Clearance ......................................................................... 33 4.8 Bearing Elasticity ........................................................................... 34 4.9 Bearing Wear Down ....................................................................... 35 4.10 Gear Meshes ................................................................................. 36 TABLE 1 Influence Coefficient Matrix ..................................................... 13 FIGURE 1 Directly Coupled Propulsion Shafting – Example ..................... 8 FIGURE 2 Bearing Reactions ................................................................... 14 FIGURE 3 Nodal Slope and Deflection Curve .......................................... 15 . iv ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 FIGURE 4 Diesel Engine Output Flange Allowable Shear Force and Bending Moment ..................................................................... 16 FIGURE 5 Tail Shaft Bearing Evaluation Program ................................... 17 FIGURE 6 Ideal Contact Area on the Bearing Exerted by Shaft (Misalignment Angle Zero) ...................................................... 19 FIGURE 7 Tail Shaft Bearing Contact as a Function of Alignment Design ..................................................................................... 21 FIGURE 8 Crankshaft Outline .................................................................. 27 FIGURE 9 Crankshaft – Equivalent Model for Shaft Alignment ............... 28 FIGURE 10 FE Model of Half of the Crank ................................................. 29 FIGURE 11 Defining Equivalent Model ...................................................... 30 FIGURE 12 Reduced Crankshaft Model – 2 M/E Bearings Only ............... 32 FIGURE 13 Reduced Crankshaft Model – 4 M/E Bearings ........................ 32 FIGURE 14 ABS Bearing Evaluation Interface........................................... 35 FIGURE 15 Gear Driven Propulsion – Equal Gear Shaft Bearing Reactions 0.21 mrad Gear Misalignment Angle ..................... 36 FIGURE 16 Gear Driven Propulsion – Uneven Gear Shaft Bearing Reactions Zero Misalignment Angle at Gear Wheel ............... 37 SECTION 3 Shaft Alignment Procedure ................................................................. 38 1 General ............................................................................................. 38 2 Shaft Alignment Procedure ............................................................... 38 3 Sighting Through (Boresighting) ....................................................... 39 3.1 Piano Wire Application .................................................................. 41 4 Slope Boring – Bearing Inclination .................................................... 42 5 Engine Bedplate Pre-sagging ........................................................... 45 6 Sag and Gap ..................................................................................... 46 6.1 Theoretical Background................................................................. 46 7 Reactions Measurement ................................................................... 48 8 Bearing-Shaft Misalignment Measurement ....................................... 48 9 Shaft Eccentricity .............................................................................. 49 10 Intermediate Bearing Offset Adjustment ........................................... 50 10.1 System with Forward S/T Bearing ................................................. 51 10.2 System with No Forward S/T Bearing ........................................... 53 10.3 Which Solution to Adopt ................................................................ 55 11 Diesel Engine Alignment ................................................................... 55 11.1 Crankshaft Deflections .................................................................. 56 12 FAQ – Problems and Solution .......................................................... 58 TABLE 1 Influence Coefficient Matrix – System with Forward Stern Tube Bearing ................................................................. 52 TABLE 2 Influence Coefficient Matrix – System without Forward Stern Tube Bearing ................................................................. 54 FIGURE 1 Example of Optical/Laser Sighting Through ........................... 40 FIGURE 2 Piano Wire Application ............................................................ 41 . ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 v FIGURE 3 Slope Boring Arrangement ...................................................... 43 FIGURE 4 Slope Boring Machine ............................................................. 43 FIGURE 5 Bearing Inclination ................................................................... 44 FIGURE 6 Bedplate Sagging Measurement Using Piano Wire ................ 45 FIGURE 7 Flange Arrangement in Sag and Gap Analysis ....................... 47 FIGURE 8 Stern Tube Bearing Contact Condition Evaluation – Sample Analysis ................................................................................... 49 FIGURE 9 System Sensitivity to Intermediate Shaft Bearing Offset Change – with Forward Stern Tube Bearing ......................... 52 FIGURE 10 Bearing Reactions for Design Offset – with Forward Stern Tube Bearing ........................................................................... 53 FIGURE 11 System Sensitivity to Intermediate Shaft Bearing Offset Change – without Forward Stern Tube Bearing .................... 54 FIGURE 12 Bearing Reactions for Design Offset – without Forward Stern Tube Bearing ................................................................. 55 FIGURE 13 Crankshaft Installation in the Engine ...................................... 57 FIGURE 14 Diesel Engine Bearing Damage due to Edge Loading ........... 58 FIGURE 15 Bearing Reactions for a Dry Dock Alignment with Intentionally Unloaded Second Main Engine Bearing ............. 59 FIGURE 16 Deflection Curve and Bearing Offset for Dry Dock Condition, which Resulted in Intentionally Unloaded Second Main Engine Bearing ................................................. 59 FIGURE 17 Bearing Reactions for a Waterborne Vessel – Rectified by Hull Deflections and Bedplate Sag..................................... 60 FIGURE 18 Total Vertical Offset at the Bearings Including Prescribed Displacements, Hull Deflection Estimate and Bedplate Sag .......................................................................................... 60 FIGURE 19 Vessel in Dry Dock .................................................................. 62 FIGURE 20 Vessel Waterborne – Hull Deflections Affect the Propulsion ............................................................................... 62 FIGURE 21 Vessel Waterborne – Engine Sag Applied .............................. 63 SECTION 4 Shaft Alignment Survey ....................................................................... 65 1 General ............................................................................................. 65 2 Alignment Acceptance Criteria.......................................................... 65 2.1 Attendance .................................................................................... 66 2.2 Required Information ..................................................................... 66 2.3 Measurement Procedure ............................................................... 66 2.4 S/T Bearing Wear Down ................................................................ 66 2.5 Dry Dock Alignment ....................................................................... 67 2.6 Noncompliance with Construction Completion Requirements ....... 67 2.7 Sag and Gap Acceptability ............................................................ 67 2.8 Number of Bearings to be Verified ................................................. 67 2.9 Reaction Measurement Acceptability ............................................. 67 2.10 Slope Boring .................................................................................. 68 2.11 Dry Dock Alignment ....................................................................... 68 2.12 Shaft Runout .................................................................................. 68 2.13 Construction Practices ................................................................... 68 . vi ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 SECTION 5 Alignment Measurements .................................................................... 69 1 General ............................................................................................. 69 2 Bearing Reaction Measurements ..................................................... 69 2.1 Jack-up Method ............................................................................. 69 2.2 Strain Gauge Method .................................................................... 75 3 Bearing Vertical Offset Measurements ............................................. 79 3.1 Reverse Shafting Alignment Calculation of the Bearing Offsets ........................................................................................... 80 4 Bearing Misalignment Measurements .............................................. 84 5 Crankshaft Deflection Measurement ................................................ 84 6 Gear Contact Misalignment Measurement ....................................... 85 7 Sag and Gap Measurement .............................................................. 86 8 Eccentricity (Runout) Measurement of the Shaft .............................. 89 8.1 Dial Gauge Runout Measurements ............................................... 89 8.2 Runout Measurement in Lathe ...................................................... 89 9 Stress Measurements ....................................................................... 90 9.1 Stress in the Shafting .................................................................... 90 9.2 Stress in the Bearing ..................................................................... 90 TABLE 1 Sample Influence Coefficient Matrix ....................................... 72 TABLE 2 Offset Vector Spectrum ........................................................... 83 FIGURE 1 Hydraulic Jack with Load Cell ................................................. 70 FIGURE 2 Digital Dial Gauge ................................................................... 71 FIGURE 3 Reaction Measurement at Intermediate Shaft Bearing ........... 71 FIGURE 4 Jack-up Measurement of the Bearing Reactions Inside Diesel Engine .......................................................................... 72 FIGURE 5 Jack-up Curve ......................................................................... 73 FIGURE 6 Jack-up Curve for Unloaded Bearing ...................................... 75 FIGURE 7 Strain Gauge Installation ......................................................... 76 FIGURE 8 Pair of Uniaxial Gauges .......................................................... 77 FIGURE 9 Wheatstone Bridge ................................................................. 77 FIGURE 10 Bending Moments Measured at Nine Different Locations Along the Shaft Line ................................................................ 78 FIGURE 11 Reverse Analysis I/O Interface ............................................... 81 FIGURE 12 Dry Dock – Bearing Offset – Reverse Analysis vs. As-designed Offset Comparison ............................................. 82 FIGURE 13 Ballast – Bearing Offset – Reverse Analysis vs. As-designed Offset Comparison ............................................. 82 FIGURE 14 Full Load – Bearing Offset – Reverse Analysis vs. As-designed Offset Comparison ............................................. 83 FIGURE 15 Intermediate Shaft Bottom Clearance and Runout Measurement .......................................................................... 84 FIGURE 16 Crankshaft Deflection Measurements ..................................... 85 FIGURE 17 Gear Contact ........................................................................... 86 FIGURE 18 Sag and Gap Measurement .................................................... 87 . ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 vii FIGURE 19 Assembled Shafting – Condition Desired After Sag and Gap is Verified ......................................................................... 88 FIGURE 20 Preassembly Shafting Setup – for Sag and Gap Measurement .......................................................................... 88 SECTION 6 Hull Girder Deflections ......................................................................... 91 1 General ............................................................................................. 91 2 Analytical Approach .......................................................................... 92 3 Hull Girder Deflection Measurements ............................................... 92 3.1 Bending Moment Measurements ................................................... 93 3.2 Bearing Reaction Measurements................................................... 95 3.3 Crankshaft Deflection Measurements ............................................ 96 4 Example ............................................................................................ 96 4.1 Analytical Approach ....................................................................... 96 4.2 Example - Hull Girder Deflection Measurements ......................... 100 5 Hull Deflection Application .............................................................. 101 FIGURE 1 Hull Girder Deflections Influence on Propulsion System ........ 92 FIGURE 2 Strain Gauge Measurement .................................................... 94 FIGURE 3 Hydraulic Jack Locations for Reaction Measurements on the Shafting and M/E Bearings ............................................... 95 FIGURE 4 Bearing Reactions are Measurements Using Hydraulic Jacks ....................................................................................... 95 FIGURE 5 Vessel Deflections Change with Loading Condition ............... 97 FIGURE 6 Large Container Vessel Shafting for Shaft Alignment Analysis Purpose .................................................................... 97 FIGURE 7 Shaft Alignment Design with No Hull Deflections Considered .............................................................................. 98 FIGURE 8 Still-water Deflections of the Vessel ........................................ 98 FIGURE 9 Containership – Diesel Engine Bearing Reactions as a Function of Hull Deflections and Bedplate Sag ...................... 98 FIGURE 10 Still-water Hull Deflections – Ballast ....................................... 99 FIGURE 11 Still-water Hull Deflections – Laden ........................................ 99 SECTION 7 Alignment Optimization ..................................................................... 102 1 General ........................................................................................... 102 2 Optimization Example ..................................................................... 102 3 Optimization .................................................................................... 105 TABLE 1 Estimated Hull Girder Deflections ......................................... 104 TABLE 2 Optimal Solution .................................................................... 107 TABLE 3 Dry Dock – Bearing Reactions for Prescribed Offset ............ 108 TABLE 4 Ballast Vessel Hull Deflections – Bearing Reactions and Total Bearing Offset .............................................................. 108 TABLE 5 Laden Vessel Hull Deflections – Bearing Reactions and Total Bearing Offset .............................................................. 109 . viii ABS GUIDANCE NOTES ON PROPULSION SHAFTING ALIGNMENT 2006 FIGURE 1 Discrete Model of the Shafting .............................................. 103 FIGURE 2 Bearing Offset; Shaft Deflection Curve; Nodal Slopes ......... 103 FIGURE 3 Bearing Reactions; Bending Moment; Shear Forces............ 103 FIGURE 4 Laden – Bearing Offset Disturbed by Hull Deflections; Bearing Reactions – Unloaded M/E Bearing #2 ................... 104 FIGURE 5 Ballast – Bearing Offset Disturbed by Hull Deflections; Bearing Reactions – Unloaded M/E Bearing #2 ................... 104 FIGURE 6 GA Input Data and Output Showing Two of Ten Desired Solutions ............................................................................... 105 SECTION 8 Glossary .............................................................................................. 111 1 Abbreviations .................................................................................. 111 2 Definitions ....................................................................................... 111 . 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