Thrust bearing fundamentals 05 2006

Outline Fluid Film Thrust Bearings: Fundamentals, Damage Evaluation, & Repair VIBRATION INSTITUTE MEETING CHARLOTTE, NC n Basic Design Criteria n Thrust Bearing Monitoring n Damage investigation n Damage mechanisms n Inspection n Repair Pioneer Motor Bearing May 2006 (c) 2006, Pioneer Motor Bearing Company (c) 2006, Pioneer Motor Bearing Company History History n Without n However, question the most significant mechanical invention in the world was: Slide almost immediately upon discovery of the wheel, the need for bearings was also discovered: The Wheel (c) 2006, Pioneer Motor Bearing Company Slide (c) 2006, Pioneer Motor Bearing Company History History n Which n As has led to one of the most elusive searches in human history Slide one can observe from this wooden wheel dating to 2700 BC, axels where used to allow support by radial and thrust bearings: (c) 2006, Pioneer Motor Bearing Company Slide (c) 2006, Pioneer Motor Bearing Company Slide Load Orientations: radial/thrust Thrust Bearing n Support n e.g axial load from the process Water or steam pressure n Thrust runner surface n Generally flat ( 1000 psi) psi) at the location of the highest loading n Hydrostatic film is developed through pressure, film thickness is controlled by flow n Quite often, many bearings are fed by a common high pressure header (c) 2006, Pioneer Motor Bearing Company Slide 34 Hydrostatic Lift System Hydrostatic Lift System n Introduce externallyexternally-pressurized oil into bearing cavity for operation at low surface speeds and high loads n Forms hydrostatic bearing on lower half Hydrostatic lift in tilting pad thrust shoes (c) 2006, Pioneer Motor Bearing Company Slide 35 (c) 2006, Pioneer Motor Bearing Company Slide 36 Sample Hydrostatic Lift Oil System Schematic of TurbineTurbineGenerator Hydrostatic Lift System Main oil pump is shaft driven AC & DC pumps Each radial bearing #3#3-8 has a separate pressurized hydrostatichydrostaticlift supply (1500 psig), separate supply pump with a gravity (or slight vacuum) drain back to the reservoir (c) 2006, Pioneer Motor Bearing Company upgrading specific design features of the assembly n Directed lubrication n Alternative materials n Offset pivots (c) 2006, Pioneer Motor Bearing Company Slide 39 n Temperature (c) 2006, Pioneer Motor Bearing Company Slide 40 Thrust Temperature Monitoring n Embedded n Load Sensors n Thermocouples Collar Position n RTD’ RTD’s n Oil (c) 2006, Pioneer Motor Bearing Company Slide 38 Effect of ChromeChrome-Copper Alloy Backing Material Thrust Bearing Monitoring n Thrust n Consider Slide 37 Effect of Pivot Offset (c) 2006, Pioneer Motor Bearing Company OK smart guy, I’ I’ve already got a tilting pad thrust bearing, Now what? Slide 41 Inlet and Exit Temperature (c) 2006, Pioneer Motor Bearing Company Slide 42 Tilt-Pad Thrust Profiles Embedded Sensors n Proper Temperature profiles show influence of pressure peak over the pivot (dashed circle), as well as radial and circumferential flow (c) 2006, Pioneer Motor Bearing Company Location Ref Kingsbury sales literature, EQHEQH-1 Slide 43 (c) 2006, Pioneer Motor Bearing Company Slide 44 Thrust Load Measurement Thrust Load Measurement n Basic n Leveling Bearing Design (c) 2006, Pioneer Motor Bearing Company Slide 45 Plates (c) 2006, Pioneer Motor Bearing Company Slide 46 Thrust Load Measurement Thrust Position Measurement n Strain n Eddy Current Probes n Dual Voting Gage Load Cell (c) 2006, Pioneer Motor Bearing Company Slide 47 (c) 2006, Pioneer Motor Bearing Company Slide 48 Thrust Position Measurement Damage Investigation n Generic Elements n Visual examination n Background information n Photographic records n Event reconstruction n Laboratory analysis Slide 49 (c) 2006, Pioneer Motor Bearing Company Damage Investigation (c) 2006, Pioneer Motor Bearing Company Slide 50 Damage Investigation n Visual Examination n Generic Elements n Visual “Say, is all that babbitt supposed to be on the bottom of the bearing housing like that?” that?” (c) 2006, Pioneer Motor Bearing Company examination n Background information n Photographic records n Event reconstruction n Laboratory analysis Slide 51 Visual Examination (c) 2006, Pioneer Motor Bearing Company Slide 52 Where is the damage? n Babbitt Surface n Centered over pivot n More toward trailing edge n More toward leading edge n Supporting n Leveling n Thrust (c) 2006, Pioneer Motor Bearing Company Slide 53 structure plates collar (c) 2006, Pioneer Motor Bearing Company Slide 54 Babbitt Surface Damage Damage located primarily along the trailing edge is indicative of of debris, electrolysis, or other trauma that occurred while the bearing was was otherwise operating in a normal condition (c) 2006, Pioneer Motor Bearing Company Babbitt Surface Damage Damage located primarily opposite the pivot is indicative the bearing bearing operating in an overloaded condition Slide 55 Babbitt Surface Damage (c) 2006, Pioneer Motor Bearing Company Slide 56 Support Structure Damage n Damage to the leveling plates, base ring, or other support structure is usually indicative of thrust collar runout problems n Collar may be installed improperly, or may have come loose in service Damage located primarily along the leading edge is indicative of a lack of lubrication, either during start up, or during operation (c) 2006, Pioneer Motor Bearing Company Slide 57 (c) 2006, Pioneer Motor Bearing Company Collar Damage Damage Mechanisms n Circumferential n Mechanisms scoring or scratching of the thrust collar is usually indicative of debris in the oil system (c) 2006, Pioneer Motor Bearing Company Slide 59 Slide 58 are the same as those covered earlier by Dr Branagan n Specific thrust bearing photographs may help (c) 2006, Pioneer Motor Bearing Company Slide 60 Minor Overload (c) 2006, Pioneer Motor Bearing Company Babbitt Fatigue Slide 61 Overheating (c) 2006, Pioneer Motor Bearing Company Slide 62 Gross Overheating Slide 63 Anisotropy (c) 2006, Pioneer Motor Bearing Company (c) 2006, Pioneer Motor Bearing Company (c) 2006, Pioneer Motor Bearing Company Slide 64 Tin / Copper Migration Slide 65 (c) 2006, Pioneer Motor Bearing Company Slide 66 Pivot Fretting (c) 2006, Pioneer Motor Bearing Company Leveling Plate Fretting Slide 67 Babbitt Erosion (c) 2006, Pioneer Motor Bearing Company Slide 68 Bearing Inspection n Bearing Surface Subsurface n Thrust Collar n Assembled End Play n Bearing (c) 2006, Pioneer Motor Bearing Company Slide 69 (c) 2006, Pioneer Motor Bearing Company Slide 70 Thrust Bearing Surface Thrust Bearing Subsurface n Portion n Ultrasonic of bearing designed to carry the load must be clean and flat n Inspect for embedded debris with a single edged razor blade n Inspect surface with straight edge n Inspect contact with Prussian bluing with a calibrated plate and finally with the mating thrust collar (c) 2006, Pioneer Motor Bearing Company Slide 71 Inspection n Dye Pen Inspection n Brass Dowel Ring Test (c) 2006, Pioneer Motor Bearing Company Slide 72 Thrust Collar Inspection Assembled Runout Check n Surface n Can finish 16 RMS or better n Surface flatness less than 001 inch n Assembled runout less than 001 TIR (c) 2006, Pioneer Motor Bearing Company not be measured with a single indicator as rotor float will impact measurement n Temporary blocking may be required to limit rotor float during inspection n Requires Mag base indicators with sufficient travel to stay in contact with collar face Slide 73 Indicator position (c) 2006, Pioneer Motor Bearing Company Slide 74 Typical Measurement record Rotation A B 0.0000 -0.0010 45 0.0015 -0.0005 A-B 90 0.0060 0.0050 0.0010 135 0.0030 0.0030 0.0000 180 0.0010 0.0020 -0.0010 0.0010 0.0020 225 0.0005 0.0025 -0.0020 270 -0.0020 -0.0010 -0.0010 315 -0.0010 -0.0010 0.0000 360 0.0030 0.0020 0.0010 Column of calculated AA-B values gives twice the TIR runout readings for the thrust collar In this example, the collar is running out 002 TIR (c) 2006, Pioneer Motor Bearing Company Slide 75 (c) 2006, Pioneer Motor Bearing Company Assembled End Play Repairs n Best n Many to first measure available space and stacked height of the bearing assemblies n Difference should be the assembled end play n After assembly, bump test the rotor to confirm measurement (c) 2006, Pioneer Motor Bearing Company Slide 77 Slide 76 minor thrust bearing repairs can be accomplished on site n The level of repair that should be attempted is directly proportional to the experience level of the technicians available (c) 2006, Pioneer Motor Bearing Company Slide 78 Babbitt Surface Repairs n n Babbitt Puddling Minor imperfections can be removed by lapping or scraping Larger scratches can be repaired by first locally puddling babbitt and followed by peening and then lapping or scraping (c) 2006, Pioneer Motor Bearing Company Slide 79 Hand Scraping (c) 2006, Pioneer Motor Bearing Company (c) 2006, Pioneer Motor Bearing Company Power Scraping Slide 81 (c) 2006, Pioneer Motor Bearing Company Thrust Collar Repair Conclusions n Minor n Remember damage and glazing can be repaired by hand stoning n Use a fine 600 grit oil stone n More serious repairs can be corrected by turning, lapping, or grinding n Many of these operations can be conducted in place (c) 2006, Pioneer Motor Bearing Company Slide 80 Slide 83 Slide 82 that that the babbitt surface is a SOFT, sacrificial layer n Look at your babbitt surface to better understand the likely cause of the bearing damage and reduce rere-occurrence n Remanufacture (repair) or redesign bearing depending on the nature, severity, and probability of future damage (c) 2006, Pioneer Motor Bearing Company Slide 84 ... radial /thrust Thrust Bearing n Support n e.g axial load from the process Water or steam pressure n Thrust runner surface n Generally flat (