Shaft Alignment. Powertrain Vibration

Transcription

1 Shaft Alignment and Powertrain Vibration Chris Leontopoulos C1

2 Shaft Alignment Definition Most shipboard configurations of shafts and bearings are likely to be aligned when some or all of the centrelines of the bearings are offset from the theoretical straight line condition, so as to achieve an acceptable bearing load distribution and shaft slope. Design Process The classic alignment technique would involve the calculation of the bearing reactions following a quasi-static analysis and varying of the bearing offsets until an acceptable set of bearing reaction loads and shaft slope is achieved. C2

3 Influence Parameters on Shaft Alignment 1. Bearing offsets 2. Thermal Effects 3. Loads (propeller, gear) 4. Crankshaft model 5. Hull Flexibility C3

4 Case Studies C4

5 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 hence slope boring C5

6 Alignment Related Failure Statistics z Bulk Carrier Chemical Carrier Container Carrier General Cargo Carrier High Speed Craf t Of f shore Supply Vessel Oil Carrier Passenger Vessel Special Purpose Vessel Tug Yacht C6

7 Stern Tube Bearing Stern tube bearing damage White Metal Bearing Damage C7

8 Stern Tube Bearing Teflon Bearing Damage C8

9 Alignment Related Failures C9

10 Shaft Alignment The alignment process is critical as it involves high risk consequences, which usually immobilise the vessel. ABS possesses extensive practical and design experience on shaft alignment. C10

11 Shaft Alignment Fundamental Principles The simply supported beam g C11

12 Shaft Alignment Fundamental Principles The simply supported beam g C12

13 Introduction Demonstrate AVI C13

14 Dry Dock In Service -Waterborne C14

15 Positioning the Bearings to Actual Design Values C15

16 Alignment Procedure Optical/Laser/Telescope C16

17 Alignment Procedure C17

18 Critical Areas C18

19 Stern Tube Bearing Alignment Desired: Even load distribution throughout the bearing length. Ideal contact between the shaft and the bearing Edge contact. C19

20 C20

21 Shaft Alignment Analysis Modelling of the bearing reaction C21

22 Propeller Loads Propeller operation in wake field behind the ship C22

23 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 not required b) >0.3 mrad then slope boring is required 3. Engine Flange bending moments in accordance with manufacturers limits C23

24 Alignment Analysis ABS Capabilities ABS Capabilities Shipyard Capabilities Shaft Alignment Analysis Shaft Alignment Analysis Hull Deflection Shaft Alignment Interaction Expertise in Installation and Build Process Optimization for Shaft Alignment Shaft Alignment Procedure Alignment Investigation C24

25 Alignment Procedure Sterntube Frame Boring Vertical / Horizontal boring of Stern tube frame C25

26 Alignment Procedure Reactions Measurements Bearing reactions are measured directly or indirectly or both. The most commonly applied methods that measure the alignment condition are: Gap and Sag Jack-up Strain gauge method The Sag and Gap and the strain gauge procedures are indirect methods to measure the deflections and correlate shaft strain to the bearing reactions, in a reverse engineering way. C26

27 Alignment Procedure Jack up method Lowering curve Hysterisis: difference in jack load between lifting and lowering Lifting curve Resultant line - average between lifting and lowering curve. Bearing reaction is then: mm C27

28 Shaft Alignment Correlation Correlation between measurements and design calculation is top priority C28

29 Alignment Procedure Strain Gauges C29

30 Alignment Procedure Strain Gauge Installation Procedure C30

31 Alignment Procedure Strain Gauge Installation Procedure C31

32 Alignment Procedure Strain Gauge Installation Procedure C32

33 Shafting Alignment Measurements Problems with alignment verification are often related to our 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 preset alignment parameters (stern tube bearing slope angle, bearing offset, etc.) accuracy of the applied alignment verification method alignment condition monitoring skills of the engineers conducting alignment procedure and measurement ability to validate measurement method and obtained results C33

34 Indirect Indications of Misalignment Crankshaft deflection measurements C34

35 Indirect Indications of Misalignment Shaft Eccentricity diagnosed through vibration monitoring Axial Radial Tangential C35

36 Dynamic Measurements C36

37 Dynamic Measurements C37

38 Dynamic Measurements C38

39 Dynamic Measurements C39

40 Dynamic Measurements C40

41 Hull Deflection ABS have established correlation among hull deflections and use the same data to predict the hull deflections of the newly designed vessel of the same type. Collected data is to be applied in the ABS Shaft Alignment Optimization software to provide a basis for more robust shaft alignment design, which will be less susceptible to the alignment condition change during the operation of the vessel. C41

42 Hull Deflection C42

43 Shaft Alignment Analysis Refined FE model of the stern structures C43

44 Shaft Alignment Analysis Alignment optimisation Optimised shaft line C44

45 Shaft Alignment Analysis Alignment optimisation C45

46 Shaft Alignment Analysis Alignment optimisation C46

47 Powertrain Vibration ABS possesses extensive practical and design experience on vibration of marine powertrains. C47

48 Vibration Acceptance Criteria 1. Torsional Stress limits (IACS) 2. Lateral and Axial Vibration 3. Torsio-axial Vibration (direct drives) C48

49 Introduction Demonstrate AVI C49

50 Torsional Vibration C50

51 Torsional Vibration Barred Speed Range C51

52 Torsional Vibration Powertrain components affected by torsional vibration C52

53 Torsional Vibration VIBRATION FAILURE C53

54 Lateral Vibration VIBRATION FAILURE C54

55 Lateral Vibration C55

56 Coupling bolts C56

57 Vibration Training using the Rotor-kit C57

58 Practical Vibration Problems Within the Classification Rules and beyond we have tackled a variety of powertrain vibration problems and issues, such as: 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 C58

59 Shaft Alignment and Powertrain Vibration & ANSWERS C59

60 Thank you for your attention C60