Coupling Alignment
- 2. COUPLING is the device used to join two shafts say, the Driver and the Driven to transmit power. Functions of Shaft Couplings To provide connection and Dis connection between the driver & follower. To provide Alignment facilities. To allow flexibility between shafts. To reduce transmission of SHOCK loads. To introduce protection against overloads. To alter vibration characteristics of rotating units.
- 3. Requirements of a good Shaft Couplings 1. It should be easy to connect and dis- connect. 2. Should be able to transmit full power. 3. Should hold shaft in alignment. 4. Should be able to reduce the shock loads. 5. Should have no projecting parts. 6. Should have smooth surfaces.
- 8. Pin & bush Flexible coupling.
- 9. Pin & bush Flexible coupling.
- 10. Pin & bush Flexible coupling.
- 11. Steel Grid or BB coupling.
- 12. TYRE COUPLING.
- 13. GEAR COUPLING.
- 14. Material for Flexible elements. • STEEL. • PLAIN RUBBER. • SYNTHETIC RUBBER. • LEATHER. • TEFLON. • PLASTIC.
- 15. a) REMOVAL. a) Never remove by hammer blow. b) Use conventional pullers. c) Hydraulic jack can be used. d) If needed, removal by heating can be done, but with great care not to damage the shaft.
- 16. b) REFITTING. a) Clean Shaft surface & Coupling bore. b) Measure the bore & shaft OD to check tolerance. c) Do not use a coupling if it has any cracks. d) Always change coupling in pairs. e) Check coupling OD for trueness & out of roundness. f) If high interference fit is needed, couplings can be heated in an oil bath up to 120°C. g) Check Key & Keyway for proper fit. h) Use pushers for fitting. DO NOT HAMMER. i) Fit coupling face perpendicular to the shaft axis.
- 17. PROBLEMS IN COUPLINGS • Crack on couplings. • Couplings loose on shaft. • Holes becoming oval. • Coupling edge damage. • Key & Keyway damage. • Both coupling halves not equal in OD.
- 18. HYDRAULIC COUPLING • A hydraulic coupling consists of two identical halves, one fixed to the driving shaft A and the other to the driven shaft.B Both these halves are housed in a common casing, filled with oil.which is used as a working medium. A is in the form of pump impeller and B is in the form of a turbine runner. • When A rotates, oil is forced out through the periphery of the pump impeller. The oil enters the turbine runner and makes it to rotate. In actual practice, the speed of B is less than that of A by 2 to 4 % • Efficiency ή = Pb/Pa = Nb/Na • Slip s = 1 – ή = 1 – Nb/Na
- 20. Hydraulic Torque Converter • A hydraulic torque converter is an improved form of hydraulic coupling. In this, the Torque ( or Speed) of the driven shaft may be increased o0r decreased. It is achieved by providing a third member in between the pump impeller and the turbinr runner, known as guide ring. It consists of a series of fixed guide vanes, whose function is to change the direction of oil, which multiplies the speed of the runner.
- 21. ALIGNMENT. Alignment is the adjustment of relative position of 2 coupled machines, so that the centre line of the axis will be concentric when the machines are running during NORMAL WORKING CONDITIONS. Misalignment may be :- • PARALLEL. • ANGULAR. • COMBINED PARALLEL & ANGULAR.
- 23. Consequences of misalignment. • A) Reduction in bearing life. • B) Coupling degradation. • C) Shaft fracture. • D) Vibration. • E) Other rotating part failures.
- 24. CHECKS BEFORE STARTING ALIGNMENT. • Coupling gap. • Soft foot. • Indicator sag. • Dial indicator rigidity. • Alignment readings. (0°, 90°, 180°& 270°) • Thermal growth. (Steel-0.01mm/M for 1°C rise in temperature.) • Sleeve bearing offset.
- 25. ALIGNMENT : SOFT FOOT SOFT FOOT is the condition, when all feet of the Pump or Motor are not in one plane.
- 26. ALIGNMENT : How to Detect SOFT FOOT ? • Put Machine on base. • Do not tighten bolts. • Attempt to pass thin Feeler Gauge Blade under a Foot. • If the blade passes, that foot has Soft Foot. • Check other feet.
- 27. ALIGNMENT : How to Rectify SOFT FOOT ? • Measure Soft foot gap. • Tighten all hold nuts • Put Dial Gauge on each foot & loosen the Bolt. • If foot rises, put Shims. • Repeat process for each foot. • Always tighten bolts in one sequence.
- 28. ALIGNMENT : SOFT FOOT. • SOFT FOOT is the condition, when all feet of the Pump or Motor are not in one plane or Poor surface contact between the underside of the Machine or Motor and the base plate or frame.
- 29. ALIGNMENT TOLERANCES : 0.013 to 0.0254000 - 6000 0.025 to 0.052000 – 4000 0.05 to 0.101000 – 2000 0.08 to 0.11<1000 TOLERANCE (mm)MACHINE RPM
- 30. METHODS OF ALIGNMENT : • Straight Edge, Feeler Gauge & Level. • Mathematical Method. • Reverse Indicator Method (graphic) • Face & Rim Alignment. (graphic) • Across Flex element. (graphic) • Laser Beam Method.
- 31. PRELIMINARY ALIGNMENT : Straight Edge -
- 33. ACCURATE ALIGNMENT : Done with the help of DIAL GAUGES.
- 34. DIAL GAUGE READING 1 0 0 20 -80 10-90 -70 30 -60 40 -50 50 -30 7080 -20 90-10 -40 60 1 2 345 TOP Large Pointer = 0.00 Small Pointer = 3
- 35. DIAL GAUGE READING 1 0 0 20 -80 10-90 -70 30 -60 40 -50 50 -30 7080 -20 90-10 -40 60 1 2 345 FAR Large Pointer = 0.00 Small Pointer = 2-3 READING - -0.60
- 36. DIAL GAUGE READING 1 0 0 20 -80 10-90 -70 30 -60 40 -50 50 -30 7080 -20 90-10 -40 60 1 2 345 BOTTOM Large Pointer = 0.00 Small Pointer = 3 - 4 READING - +0.83
- 37. DIAL GAUGE READING 1 0 0 20 -80 10-90 -70 30 -60 40 -50 50 -30 7080 -20 90-10 -40 60 1 2 345 NEAR Large Pointer = 0.00 Small Pointer = 2-1 READING - -1.075
- 38. DIAL GAUGE READING 1 0 0 20 -80 10-90 -70 30 -60 40 -50 50 -30 7080 -20 90-10 -40 60 1 2 345 TOP Large Pointer = 0.00 Small Pointer = 3
- 39. ACCURATE ALIGNMENT : Dial Gauge -
- 40. 500 300 200 ACCURATE ALIGNMENT CALCULATION : 4.5 4.0 Coupling Gap Top= 4.5 mm. Coupling to Front Foot = 500 mm Coupling Gap Bottom=4.0 mm. Front to Back Foot = 300 mm Coupling Radius = 200/2= 100 mm. Total distance = 800 mm
- 41. Alignment calculations Gap difference = 4.5 – 4 = 0.5 / 2 = 0.25 (A) a) Distance corrections = 800 / 100 = 8 (B) So (A) x (B)=0.25 x 8 = 2 mm shim is to be given under each back foot. b) Corrections when front feet are to be raised :- Distance corrections = 500 / 100 = 5 (B) So (A) x(B) =0.25 x 5 = 1.25 mm shim is to be given under each front foot.
- 42. REVERSE INDICATOR ALIGNMENT METHOD. • Before starting the alignment, the MASTER must be decided. The other machine must be moved to align the shafts. First take the dial indicator readings on the pump coupling and then the readings on the motor coupling. On a sheet of graph paper, layout the equipment being aligned. The scale used is one small division equal to 1 inch.or to any suitable scale. Plot the distances.
- 44. TOP
- 45. FAR
- 46. BOTTOM
- 47. NEAR
- 48. Reading calculations : Pump Motor Horizontal. Near + 0.006 Far (-) +0.004 (-) +0.002 /2 = Horizontal. Near - 0.005 Far (-) - 0.015 (+) +0.010 /2 = Vertical. + 0.005 - 0.000 + 0.005 Sag (-)- 0.005 (+) + 0.010/2 = Vertical. - 0.025 - 0.000 - 0.025 Sag (-)-0.005 (+) - 0.020 / 2 = - 0.010 + 0.005 + 0.005 + 0.001
- 49. Pump to motor alignment guide. - Near side + Near side- on bottom + on bottom + Near side - Near side+ on bottom - on bottom - Near side - Near side- on bottom - on bottom + Near side + Near side+ on bottom + on bottom Reading on motorReading on pumpReading on motorReading on pump Horizontal (Top view)Vertical (Side view) Pump shaft Motor shaft
- 50. Reading calculations : BottomTopBottomBottomPosition on graph. + 0.001+ 0.005+ 0.005- 0.010Reading MotorPumpMotorPump Horizontal.Vertical
- 51. P FFM BF P FFM BF HORIZONTAL SOLUTION VERTICAL SOLUTION 0.010 0.019 0.007
- 52. Reading on pump. 0.00 + 0.04 + 0.03- 0.02 Reading on motor. 0.00 + 0.02 + 0.04+ 0.06 Example – 2 Reverse Indicator Method
- 53. Reading calculations : Pump Motor Horizontal. Near + 0.06 Far (-) + 0.04 (-) +0.02 /2 = Horizontal. Near - 0.02 Far (-) + 0.03 (-) - 0.05/2 = Vertical. + 0.02 - 0.00 + 0.02 Sag NIL + 0.02/2 = Vertical. +0.04 - 0.00 + 0.04 Sag NIL +0.04 / 2 = + 0.02 + 0.01 - 0.025 + 0.01
- 54. Reading calculations : BottomBottomBottomTopPosition on graph. + 0.01- 0.025+ 0.01+0.02Reading MotorPumpMotorPump Horizontal.Vertical
- 55. P M FF BF 0.125 P M FF BF 0.01 0.0455 Vertical correction Horizontal correction 0.05 (Scale 1=0.005) Distance : P M=130 mm; M FF=180 mm; FF BF= 330 mm. Scale 1= 100 mm TOP BOTTOM FAR NEAR
- 56. Conclusion : Top – Bottom correction : • The motor shaft : 0.05 shim is to be given under each front foot and 0.125 shim under each back foot Far – Near correction : • The motor shaft has to be shifted towards near end. The front feet by 0.01 and the back feet by 0.0455
- 57. MULTIUNIT ALIGNMENT • Plot all three units in a single piece of graph paper using the reverse indicator method. Unit 1 is master, there will be two lines for unit 2 and unit 3. Draw an alternate reference line close to the actual position of the three units. Minimal movement is required to get all units aligned.
- 59. Across the Flex Element
- 60. Positive reading means the intermediate shaft axis is below the gearbox.
- 61. Negative reading means the intermediate shaft axis is above Motor or the motor is below the intermediate shaft.
- 63. LASER ALIGNMENT TOOL S M S-unit on the master machine. M-unit on movable machine.
- 64. Rough Laser Alignment 1. Turn shafts with measuring units to position 9 o’ clock. Aim the laser beams to the centre of the closed target. 2. Turn shafts with measuring units to position 3 o’ clock 3. Check where the laser hits.then adjust the beam half the travel in direction to centre of the target. 4. Adjust the movable machine so that the laser beam hits the centre.
- 66. Alignment and its effect on vibration. • Misalignment causes vibration. • There is no 1 to 1 relation with amount of misalignment and amount of vibration. • Misalignment can cause failure of not only the coupling but also Bearings and other moving parts. • Highest reaction is on the free or outboard bearing instead of inboard end. • Misalignment normally causes both Axial and Radial vibration.
- 67. OTHER SOURCES OF HIGH AXIAL VIBRATION. • Bent shafts. • Shaft in resonant whirl. • Resonance of some components in axial direction. • Worn thrust bearing. • Worn helical and bevel gears. • A sleeve bearing motor hunting for its magnetic centre. • Couple component of dynamic unbalance. (So high axial vibration should not be concluded as the problem of misalignment only)
- 68. CHARECTERISTICS OF MISALIGNMENT. 1. 2xRPM vibration. 2. Multiple harmonics. 3. Phase is the best indicator. Phase difference across the coupling approaches 180 O (+ / - 40 O to 50 O )
- 69. One Event 1 Revolution Axial Direction Rigid shaft. Flexible shaft. ANGULAR
- 70. ANGULAR MISALIGNMENT. 1. Primarily generates high axial vibration at 1X & 2X rpm.. 2. Best detected by 180O phase change across coupling in axial direction. 3. Amplitude of 2X or 3X RPM exceeds approximately 30% to 50% of that at # X RPM in the AXIAL direction
- 71. PARALLEL MISALIGNMENT. 1 st. Event 2 nd. Event 1 Revolution Radial Direction Rigid shaft. Flexible shaft.
- 72. PARALLEL MISALIGNMENT. 1. More Radial vibration. 2. It causes phase difference to approach 180O in Horizontal direction. 3. 2X RPM exceeds 50% of 1X RPM.
- 73. MISALIGNED BEARING COCKED IN SHAFT.. 1. A cocked bearing will normally generate considerable axial vibration which affects 1X RPM & 2X RPM. 2. If phase is measured in the axial direction at each of a 4 points 90O apart from each other a cocked bearing will be indicated by 180O phase shift from top to bottomj and side to side.
- 74. COUPLING PROBLEMS 1. 2X RPM will often respond to coupling problems. 2. In these cases both Radial and Axial direction will show a fairly noticeable 3X RPM component.
- 75. Thank you ! Any questions please ? Presented by : A. Jayprakash