Fluid film bearings 05 2006

Outline n Pioneer Introduction VIBRATION INSTITUTE FLUIDFLUID-FILM BEARINGS Pioneer Motor Bearing May 2006 Motor Bearing Company Journal / Sleeve Bearings n Fundamentals n Operations impacts n Installation / handling n Friday: Thrust Bearings n Extension of previous discussion n Thursday: (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Pioneer Motor Bearing Co n n n n n n Established in 1920; familyfamily-owned Offers triad of engineering, new manufacture, and repair services related to fluidfluid-film bearings Alliance partner with Michell Bearings Exclusive repair licensee of Siemens (Westinghouse) and Alstom Power in North America for largelarge-steam, babbitted products Proprietary Fluid Pivot® Pivot® tiltingtilting-pad journal bearing Customized training courses available (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Locations Philadelphia: Technical Services California: Administration & Regional Sales North Carolina: Engineering Manufacturing Service & Repair (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing (c) Pioneer Motor Bearing Company, 2006 Pioneer Motor Bearing Engineering Manufacturing Service & Repair (c) Pioneer Motor Bearing Company, 2006 n Engineering (c) Pioneer Motor Bearing Company, 2006 & Technical n Manufacturing Pioneer’ Pioneer’s Custom Designs (Including Fluid Pivot® Pivot® Journal Bearings) Services n Manufacturing to Customers’ Customers’ Designs n Repair, Modifications & Upgrades (c) Pioneer Motor Bearing Company, 2006 Engineering Lyle A Branagan Dr Lyle A Branagan n Engineering Engineering Manager BSME, MS, Ph.D Manager n BSME – 10 years with PG&E – Has substantial knowledge of rotor dynamics of turbomachinery – Extensive experience in the field – An expertise in fluid film bearings and seals (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing (c) Pioneer Motor Bearing Company, 2006 / MSME – Machinery dynamics n PhD – FluidFluid-film bearing analysis n University of Virginia – ROMAC Lab n IndustriallyIndustrially-accepted n Pacific design codes Gas & Electric – 10 years n Specialist in bearings and rotordynamics n Knolls Atomic Power Lab n Pioneer Motor Bearing – 10 years (c) Pioneer Motor Bearing Company, 2006 Fred C Wiesinger Technical Services Manager •Expertise in high speed gearboxes •Expertise in thrust bearings •Expertise in bearing repair services Frederick (Fred) C Wiesinger Technical Services Manager n Drexel University n BSME With Honors n Philadelphia n Manager Gear – Years High Speed Gear Boxes n Kingsbury, Inc – 14 Years n Chief Office in Lansdale, PA 1-(215) 362362-4074 Engineer n Manager, Repair & Service Division n Vice President, Manufacturing n Turbo Research, Inc – ½ Years (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Topics Presentation Goals n Abbreviated class •Understand operation of fluidfluid-film bearings •Relate vibration changes to potential bearing changes from 88-12 hour training n Introduction n Journal bearing overview overview n Lubricant overview n Wear overview n Babbitted bearing damage n Rotordynamics / journal bearings n Predictive maintenance interface n Installation and handling n Questions and discussion n Lining (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Topics – Friday Demonstrations Focus on Thrust (Axial) Bearings n Viscosity n Thrust bearing overview n Babbitted bearing damage n Rotordynamics / thrust bearings n Predictive maintenance interface n Installation and handling n Questions and discussion (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing n Hydrodynamic film n Cavitation n Slinger ring operation (c) Pioneer Motor Bearing Company, 2006 Perspectives on Bearings A “small” piece in the plant n Pioneer Motor Bearing Company n Power Plant or Manufacturing Plant n Maintenance n Machine Designer n Lubricant Vendor n Vibration Specialist (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Machine Design Perspective n Allow With the potential to cause: rotating equipment to operate n Separate rotating and stationary components n Support the rotating load n Control rotordynamics n Requires n Support n Adequate GOAL: n Lubricant cooling flow Avoid Frustration, Extra Work, Late Nights, Lost Production (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Lubricant Perspective Vibration Specialist Perspective n Lubricant n Common to satisfy requirements n Proper point of measurement for vibration n Viscosity additives n Adequate operational life n Understand impact on oil analysis n Potential interaction of sensors and sensor mounting n Defines the measured quantity n May define allowable vibration n Bearing clearance bearing loads, esp dynamic n Allowable n Faults may affect vibration signature n Excessive vibration may affect bearings (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing (c) Pioneer Motor Bearing Company, 2006 End Introduction (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Fluid-Film Bearings Babbitted Bearing Overview PIONEER FLUIDFLUID-FILM BEARING WORKSHOP Pioneer Motor Bearing Company August 2006 (c) Pioneer Motor Bearing Company, 2006 All rights reserved Outline n Radial n Bore APPLICATIONS: n Radial turbine, generator, fan, pump, and motor bearings n Turbine, generator, fan, pump, and motor thrust bearings n Generator hydrogen and other high pressure seals (c) Pioneer Motor Bearing Company, 2006 All rights reserved Opening Up the Machine Bearing bolted to machine or mounted in end bell bearings design n Thrust bearings n Profile designs n FluidFluid-film bearing analysis n Reynolds equation Bearing integral with shell (c) Pioneer Motor Bearing Company, 2006 All rights reserved Opening Up the Bearing (c) Pioneer Motor Bearing Company, 2006 All rights reserved Load Orientations: radial/thrust End bell and housing top removed Upper half and lower half showing ID (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing (c) Pioneer Motor Bearing Company, 2006 All rights reserved Load Orientations: radial/thrust n Horizontal n Radial n n (axial) bearing Axial process loads n Vertical n Radial n machine bearing Gravity load Radial process / misalignment loads n Thrust n Radial Bearings machine bearing Radial process / misalignment loads n Thrust bearing Gravity load n Axial process loads n (c) Pioneer Motor Bearing Company, 2006 All rights reserved Thrust Bearings (c) Pioneer Motor Bearing Company, 2006 All rights reserved Elements n Function n Purpose of a fluidfluid-film bearing n Geometry n Key features n Hydrodynamic theory n Materials n Liner and support n Lubricant (c) Pioneer Motor Bearing Company, 2006 All rights reserved Function Separate rotating from nonnon-rotating components n n (c) Pioneer Motor Bearing Company, 2006 All rights reserved Separation n Maintain close clearances n Motors / Generators windings n Fan seals and blades n Turbine blades Force transmission Prevent undesirable vibrations n Clearance Transfer loads (static and dynamics) from the rotating to the stationary structure supply Primary source of damping Provide cooling (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing (c) Pioneer Motor Bearing Company, 2006 All rights reserved Hydrodynamic versus Hydrostatic Hydrodynamic versus Hydrostatic n Hydrodynamic – pressure induced by relative motion n Hydrostatic – pressure supplied by external source Ref: Intelligent Mechanics Lab, Pukyong University, website (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing Company, 2006 All rights reserved Shell Babbitt General Clearance Rotating Journal BABBITT CLEARANCE 36 40 CLEARANCE 35 E NV CO 30 25 20 G ER GIN 15 CLEARANCE EXAGGERATED X DIV END VIEW hd( θ ) mil IN RG Clearance SHELL G Sleeve Bearing Geometry 10 BABBITT ROTATING JOURNAL CLEARANCE 0 SHELL CONVERGING CLEARANCE DIVERGING CLEARANCE ROTATING JOURNAL Housin g 90 180 270 θ deg Circumferential Position Clearance space is filled by a lubricant CLEARANCE GREATLY EXAGGERATED (c) Pioneer Motor Bearing Company, 2006 All rights reserved Clearance (c) Pioneer Motor Bearing Company, 2006 All rights reserved Clearance n Assume 0.009” 0.009” radial clearance on a centered 12” 12” diameter bearing JOURNAL 230 µm (0.009” (0.009”) radial clearance on a centered 300 mm (12” (12”) diameter bearing n Assume JOURNAL BEARING Human hair about 0.003” 0.003” diameter BEARING By comparison, the minimum operating clearance is only about 0.002” 0.002” (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing Human hair about 75 µm (0.003” (0.003”) diameter By comparison, the minimum operating clearance is only about 50 µm (0.002” (0.002”) (c) Pioneer Motor Bearing Company, 2006 All rights reserved 360 360 FluidFluid-Film Bearing Critical Geometry: space between the rotating and stationary components n Clearance n CONVERGING SPACES develop pressure n Circumferential grooves carry flow n Axial grooves spread flow n Tilting pads reduce crosscross-coupled forces n Size on the order of 0.001” 0.001”-0.050” 0.050” (40(402000 µm) (c) Pioneer Motor Bearing Company, 2006 All rights reserved Sleeve Bearing Geometry Reynolds Equation ∂  h3 ∂P  ∂  h3 ∂P  R h + x 12 ∂ x  z 12 ∂z  ∂ x Circumferential Flow Axial Flow Shear Flow ∂h ∂t Vthru Squeeze Cross Flow Flow hydrodynamic (ω (ω>0) or hydrostatic pressures (ω (ω=0) n Corrections for turbulence (G (Gθ and Gz) and crosscross-film viscosity variations (µ(y)) n Determine (c) Pioneer Motor Bearing Company, 2006 All rights reserved Bearing Pressures (Load Capacity) Theoretical negative pressures in the diverging region are cancelled by air flow from the axial ends Pressures developed in the lubricant due to the converging wedge provide the bearing load capacity Converging Film w/CCW rotation (c) Pioneer Motor Bearing Company, 2006 All rights reserved Reynolds Equation – 2-D Profile (c) Pioneer Motor Bearing Company, 2006 All rights reserved Sleeve Bearing Flows PRESSURE Strong rotation with shaft; average velocity about ½ shaft surface velocity (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing Lower, pressure driven axial velocity (c) Pioneer Motor Bearing Company, 2006 All rights reserved Reynolds Equation - Cavitation Cavitation Diverging Film å å> Converging Film å å> “Cavitation” Cavitation” region, present in the upper half, generally occurs by air penetration, less frequently by oil vaporization Axial distribution: Area at minimum film limits the flow available Downstream volume is only partially filled (c) Pioneer Motor Bearing Company, 2006 All rights reserved Bearing Cavitation (c) Pioneer Motor Bearing Company, 2006 All rights reserved Bearing Cavitation Air intrusion Axial distribution: Axial distribution Area at minimum film limits the flow available Downstream increased volume is only partially filled Minimum Film Radial distribution Air intrusion (c) Pioneer Motor Bearing Company, 2006 All rights reserved Cavitation - Experimental (c) Pioneer Motor Bearing Company, 2006 All rights reserved Cavitation Demonstration n Manual n Take Plexiglass bearing showing the formation of cavitation in the region of increasing film thickness (2) small plates n Spread thin layer of grease n Press plates together with grease in between n Open plates from one side pattern of grease n Observe n Demonstration rig Ref Cole and Hughes, Proc.Inst.Mech.Engr Proc.Inst.Mech.Engr., 170/17, 1956 (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing (c) Pioneer Motor Bearing Company, 2006 All rights reserved End Bearing Fundamentals II (c) Pioneer Motor Bearing Company, 2006 All rights reserved (c) Pioneer Motor Bearing CompanyBearing Outline n Vibration Interface with Predictive Maintenance Programs monitoring monitoring n Temperature monitoring n Thermography n Balancing n Lubricant PIONEER FLUIDFLUID-FILM BEARING WORKSHOP Pioneer Motor Bearing Company May 2006 (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Types of Alarms Monitoring Purposes n Protection n Avoid / Aging “absolute” absolute” levels at which damage is expected n Statistical n Goal n Example: Prevent high temperature at which bearing material can no longer support the applied load based n Detect changes in the machine based on trending n Example: Identify step increase in vibration level over time (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Machine Monitoring Vibration Monitoring Vibration is the product of the excitation (force) (force) with the machine system (transfer function) Must know two out of three Vibration monitoring at or near the bearings Ref Ehrich, Ehrich, Handbook of Rotordynamics, Rotordynamics, p.4.54 p.4.54 Ref: Mitchell, Machiner Monitoring (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance (c) Pioneer Motor Bearing Company, 2006 Vibration Monitoring Vibration Monitoring NonNon-linear vibration responses Common vibration frequency content with malfunctions Ref Ehrich, Ehrich, Handbook of Rotordynamics, Rotordynamics, p.4.55p.4.55-4.56 4.56 (c) Pioneer Motor Bearing Company, 2006 Shaft Relative to Casing Measurement Ref Ehrich, Ehrich, Handbook of Rotordynamics, Rotordynamics, p.4.60 p.4.60 (c) Pioneer Motor Bearing Company, 2006 Mounting Considerations Mounting external to the bearing Mounting internal to the bearing Useful for monitoring where the primary shaft motion is within the the bearing (consider the relative stiffness of the oil film and the bearing support) Also, can compare motion to the expected bearing clearance (c) Pioneer Motor Bearing Company, 2006 Flexibility Effect on Monitoring (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance Impact on vibration limits? Impact on bearing load capacity? Ref: SKF web site, 04/06 (c) Pioneer Motor Bearing Company, 2006 Include Casing Measurement (c) Pioneer Motor Bearing Company, 2006 Frequency Content Allowable Vibration Levels Primary frequency content associated with fluidfluid-film bearings is synchronous (1X) Other frequencies may occur due to different causes n Absolute n Generally Ground Currents Subsynchronous whirl Looseness: limits Subsynchronous whip based on experience to a fraction of the bearing clearance (e.g 50%) n Bearing limits generally not controlling n Limit n Contact at seals loads n Excessive Misalignment (c) Pioneer Motor Bearing Company, 2006 Bearing Loads Affected n Conditions determined by vibration analysis which have an impact on bearing loads (c) Pioneer Motor Bearing Company, 2006 Bearing Loads Affected Imbalance – dynamic loads on bearings n Static n Dynamic Misalignment - static load variation Soft Foot – dynamic load variation (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Lubricant Monitoring Lubricant Monitoring n Viscosity n Requires Monitoring n Note that baseline oil will vary within the standard n Look for changes around +/+/- 10% from baseline n Oil Degradation Materials n Wear careful sampling n Representative n Sampling of the bulk oil point n Maintain cleanliness n Consistent handling n Auxiliary bearing oil reservoirs may be small n Sampling assumes reservoir is much larger than the sample (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance (c) Pioneer Motor Bearing Company, 2006 Lubricant Degradation Metals in Oil n Various Shows scatter of RBOT testing for a single oil and effect of operation of 18 years and 21 years on two particular oils metals included in additives n Boron (B) n Calcium (Ca) n Magnesium (Mg) n Barium (Ba (Ba)) n Molybdenum (Mo) n Phosphorus (P) n Concern w/catalytic converter (may change by 04/04) n Potassium (K) (Zn) n Antimony (Sb (Sb)) n Zinc (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Metals in Oil Metals from Bearing n Metals n Babbitt from bearing n Babbitt (tin based) n Tin n Antimony n Copper n Slinger rings (bronze) n Copper n Tin Wide range of possible babbitt wear particle sizes Many detection methods in oil analysis are size dependent / Zinc n Journal / Shell (steel) n Iron n Large n Babbitt n Large wiping platelets – may not be detected fatigue pieces – may not be detected n Electrolysis n Smaller n Slinger particles – more likely to be detected ring abrasive/adhesive wear n One plant takes action around 3030-100 ppm of copper (Cu) (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Particle Detection Lubricant Cleanliness n Detection n Measured by many spectroscopic techniques n Particles smaller than microns by particle counting n “Representative” Representative” sample n Reported based on particle size and concentration n Current n Older n Limits standard: R4/R6/R14 standard: R5/R15 set by critical component n Control n OEM (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance surface or valves, bearing limits: 16/12, 16/13, 15/12 (c) Pioneer Motor Bearing Company, 2006 Contamination from Oil System Grease Contamination n Contamination of oil from adjacent grease lubricated system n Increase in particle count n Without increase in wear particles n Reduction in viscosity is possible n Due to the gelling agent n Not the base oil which is typically more viscous Ref Noria presentation material (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Lubricant Degradation Temperature Monitoring n Base n Limits oil has finite life due to onon-going oxidation n Catalyzed in copper piping n Catalyzed by water in the oil n Additive depletion n Reduction Oil degradation rate doubles with every 18° 18°F rise in bulk oil temperature n Journal bearings n Thrust bearings of antianti-oxidant n Base oil burned at hot spots n Base oil changes n Increasing n Sludge viscosity and varnish (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Temperature Limits Absolute / Relative n ISSUES n Absolute n Measurement n How location close to the hottest metal location? knowledge of design details, loads, and speeds n Generally a predictive effort n n Load n Babbitt strength is dependent on temperature n Heavy load regions will move first n Thermal distortion n Changes in film thickness distribution that reduce load capacity (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance limits n Require Possibly relating a peak temperature to a measured point n Relative limits n Requires n Looking historical temperature information for deviation from a norm n Can be complicated by normal operating variations n “Rules of thumb” thumb” n Guidelines to initiate relative monitoring in the absence of predictive information (c) Pioneer Motor Bearing Company, 2006 Temperature Limits Lubricant Temperature Limits n Considering n Loss Babbitt (not Lubricant) of Viscosity n Nominal n Due n Requires n Material bearing loading accurate measure of peak temperature n Alloy #2 APPLICATION ALARM Steam / gas turbine 225°F (107°C) Tilt pads 230°F KEPCO (95-100°C) No load Trident sub gear bearing 300°F TRIP 250°F (121°C) 250°F (121°C) (120°C) 300°F (149°C) Reference Glacier Nicholas to temperature or oxidation Degradation n Oxidation n Varnishing n Loss of additives by corrosion n Activated Glacier n Actual temperature also controlled by Support Material, Oil Flow Path, and Oil Volume (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Company, 2006 Temperature Profiles Journal Bearing Measurement n Thermocouple Case 2: Peak Temperatur e SAME Drain Temperature Case 1: Peak Temperature Angular Location from Start of Film (c) Pioneer Motor Bearing Company, 2006 Temperature Measurement or RTD (100° (100°F- 250° 250°F) n Location n Circumferential - 75% offset from leading edge n Axial - centered or symmetric pair n Radial - retain support for babbitt above sensor n Wiring n Avoid impeding pad tilt or oil flow (c) Pioneer Motor Bearing Company, 2006 Mounting Locations Options for thermocouples or RTD’ RTD’s (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance (c) Pioneer Motor Bearing Company, 2006 Tilting Pad Journal Bearings Flooded design: sump (drain) temperature is an average of the circulating oil temperature and can be directly lowered by increasing flow Thrust Bearing Temperatures Directed lubrication (Fluid Pivot® Pivot®) with direct measurement of bearing metal temperature (c) Pioneer Motor Bearing Company, 2006 Thrust Bearing Measurement n Thermocouple (c) Pioneer Motor Bearing Company, 2006 Thrust Bearing Measurement or RTD (100° (100°F- 250° 250°F) n Location n 75%/75% Tilt pad 70%/70% Circumferential/Radial n 50%/50% Circumferential/Radial n Axial - retain support for babbitt above sensor n * * Standard monitoring location for one OEM n Wiring n Avoid impeding pad tilt or oil flow Ref: Mitchell, Machinery (c) Pioneer Motor Bearing Company, 2006 Mounting Locations (c) Pioneer Motor Bearing Company, 2006 Thermography n Gives an overview of the temperature over accessible portions of the housing, shaft, and bearing n Need to understand the relationship between the measured locations and the hottest operating parts of the bearing (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance (c) Pioneer Motor Bearing Company, 2006 Thermography Balancing Consider the likely temperature gradient from the peak bearing babbitt temperature to the motor casing temperature Note circumferential and axial spreading of the “hot spot” spot” n Balancing calculation is generally determined by the n Current n Vibration level changes n Bearing changes or n Imbalance changes? n Influence n Based n (c) Pioneer Motor Bearing Company, 2006 vibration level at the bearings of a weight at each balance plane n Influence of balance weights on the dynamics of the rotor support Based on the bearing geometry and condition (c) Pioneer Motor Bearing Company, 2006 Outline n Consider effect of bearing design and operation on the tools in your Predictive Maintenance program n Vibration monitoring n Lubricant monitoring n Temperature monitoring Rotor change or n Thermography bearing change or …? n Balancing (c) Pioneer Motor Bearing Company, 2006 Interface with Predictive Maintenance End Preventative Maintenance Interface Section (c) Pioneer Motor Bearing Company, 2006 Outline n Installing and Handling of Babbitted Bearings (partial) Abbreviated presentation with emphasis on potential impact on machine vibrations: n n n n n n n Pioneer Motor Bearing Company May 2006 n n n n Visual Inspection Measurements Alignment Considerations Pedestal Measurements Scraping Shaft Roughness Cleanliness Requirements Material Handling Requirements NDE Requirements Insulation Final Assembly Tips Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Visual Inspection Journal Diameter n Visually inspect bearings and associated hardware for damage n Refer to the bearing damage section of this presentation for assistance with root cause analysis n It is never a great idea to rere-assemble any machinery with bearings that are visibly damaged n Measure for diameter, taper, and ellipticity n Measure within 0.0002” 0.0002” be round within 0.0005” 0.0005” n Taper less than 0.0005” 0.0005”/inch of length n Should n Uniform taper less critical with dynamically aligning radial bearing n Be aware that any eccentricity from the journal to the rest of the rotor can appear as higher dynamic forces Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Bore diameter Outer diameter C Measure diameters Circular bore C B A D B φ= D E A+ B +C + D + E Elliptical bore φVertical = C φHorizontal ≈ B=D A+ E E A A E D Repeat measurements near front and back axial faces to check for taper Copyright 2006, Pioneer Motor Bearing Company C B Copyright 2006, Pioneer Motor Bearing Company Repeat measuremeasurements near front and back axial faces to check for taper Pad thickness Tapered Thrust Plate Measure wall thickness near both axial faces (check taper) and on each pad (check consistency) E D C B A CCW rotation Measure drop with respect to flat land region at 15 “circled” circled” points, as indicated CROSSCROSS-SECTION Preloaded pad has thicker crown (C) than ends (A,E) Copyright 2006, Pioneer Motor Bearing Company Thrust Bearing Clearances n Axial range of motion of the shaft between “active” active” and “inactive” inactive” thrust surfaces n Field checked by bump test n Must overcome residual oil films n Clearance can increase due to component compression n Leveling n Shim links packs or supports n Clearance can decrease due to shaft Copyright 2006, Pioneer Motor Bearing Company Thrust Bearing Clearances n Usually Adjusted through the use of a shim or filler plate n Avoid the use of numerous stacked shims n Calculate the required shim thickness using measurements of available space n Thickness of tilting pad thrust bearings must be measured as an assembly n Confirm final clearance by bump checking rotor with upper housing half in place expansion Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Alignment Considerations Bearing Elevation n Review n Multiple historical operational data n Review OEM recommendations n Measure and document as found conditions bearings (>2) for a continuous shaft n Typical power generation shafts “even” even” loading by setting proper elevation and alignment of each bearing n Goal: n Typical elevation follows catenary curve n Avoids adding additional shaft moment n Installation may need to “preload” preload” bearing to set at the proper elevation Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Catenary Curve Catenary Curve Applies to hanging chain, power line, rope, etc cosh  t amp  y ( t ) = amp Bearing installation seeks to place all bearings on a caternary curve   Copyright 2006, Pioneer Motor Bearing Company Catenary Curve Catenary curve minimizes bearing loads and moments Catenary Curve: Designed vs As-Built 1.35 1.5 Copyright 2006, Pioneer Motor Bearing Company Gravity Sag (in) cat in >1.2” >1.2” catFound 0.5 in Catenary Curve n Raise bearing from shaft sag position to desired point on the catenary curve Setting elevation of end bearing (e.g exciter) Operating catenary curve “Preload” Preload” Sag − 0.121 0.5 20 40 60 80 100 120 axial ft Axial Position from #1 Bearing (in) 140 160 152 Ref “Bearing Misalignment… Misalignment…500MW TurboGenerator” TurboGenerator”, Ettles, et al, 1974 Main Bearing Overhung Bearing 500 MW turbine generator, 150 ft long, 14 bearings Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Elevation Preload Bearing Adjustment n Raise n Quite bearing from shaft sag position above desired point on the catenary curve to improve stability of sleeve bearing Setting elevation of end bearing (e.g exciter) Additional bearing elevation Operating catenary curve Preload Sag Main Bearing Overhung Bearing Copyright 2006, Pioneer Motor Bearing Company often, when installing new or rebuilt bearings will require alignment of the machinery n Many large turbine and generator bearings have alignment “Keys” Keys” installed n Many smaller machines require adjustment of the bearing housing or pedestal Copyright 2006, Pioneer Motor Bearing Company Bearing Adjustment Bearing Adjustment Typical Tilting Pad Journal Bearing with external “Keys” Keys” for adjusting the radial position of the bearing Lower Bearing half with adjustment keys centered Copyright 2006, Pioneer Motor Bearing Company Bearing Adjustment Copyright 2006, Pioneer Motor Bearing Company Misalignment n Radial: journal axial centerline is not parallel to the bearing centerline n Thrust: runner surface is not parallel to the bearing surface Adjustment of keys for horizontal offset showing improper contact contact with the housing bore Copyright 2006, Pioneer Motor Bearing Company Misalignment Accommodation n Goal: Misalignment Accommodation Prevent unun-even loading of bearing n Especially n Copyright 2006, Pioneer Motor Bearing Company edgeedge-loading Radial n Spherical, “ball fit” fit” on OD (outer diameter) (e.g “ball in socket” socket”) surface for pad OD in tilttilt-pad bearing n Other means of aligning: scraping, pins, shims n Spherical n Thrust n Leveling links fit on thrust plate back n Other means: pins, shims n Spherical Copyright 2006, Pioneer Motor Bearing Company Blue Check of Turbine Journal Bearing Copyright 2006, Pioneer Motor Bearing Company Alignment Issues Bearing Support Fits n Generally n Housings installed under cold conditions n Clearance n Alignment varies with temperature n Affected by casing distortions n Mechanical fits can “lock up” up” under operating bearing (radial or thrust) loads n Prevents further adjustment n Problem installations require nonnonmechanical accommodation fits / Tight fits n Depends on housing design and bearing wall thickness n Pedestal n Avoid n No “soft” soft” foot deflection > 0.001” 0.001” n Consequence of looseness n Reduced stiffness and damping n Increased vibration Copyright 2006, Pioneer Motor Bearing Company Thrust Collar Runout n Want the collar “square” square” to the axis of rotation n Can be difficult to measure if shaft is floating on the radial bearings Dial indicators 180° 180° apart n n n n Avoid collar “wobble” wobble” A and B indicators Record the measurements as the shaft is turned at both indicators n n n n Sign of the reading (+ or -) must be recorded Insure that both indicators return to “zero” zero” Subtract readings at “B” from “A” Gives twice the TIR of the collar Copyright 2006, Pioneer Motor Bearing Company Material Handling Requirements n Avoid excessive force secure jacking systems to support shaft during and after bearing removal n If using an overhead crane, roll the bearing using chainfalls, chainfalls, not the main or auxiliary hook n Use Copyright 2006, Pioneer Motor Bearing Company Material Handling Requirements Bearings will gall and pick up metal from the pedestal bore if excessive force is used for installation or removal Caution must be exercised while installing or removing bearings Fingers should never be inserted in barring holes or between lifting eyes and the pedestal joint It is quite a common occurrence that a bearing that seems tightly wedged in position will quickly roll to bottom dead center with great force Copyright 2006, Pioneer Motor Bearing Company Copyright 2006, Pioneer Motor Bearing Company Bearing Insulation n Insulation serves as a electrical boundary n n n n Humidity will degrade insulation Insulation resistance lowers with temperature Oily dirt and debris will degrade insulation Insulation serves as a mechanical boundary n n Prevent dirt from “bridging” bridging” the insulation Avoid damaging due to impact or peeling Copyright 2006, Pioneer Motor Bearing Company Bearing Installation n Thin n Keep wall shells n Precision halves conform to housing n Bearing geometry depends on housing geometry n Shell must conform to housing geometry n Thick wall shells n Bearing defines geometry supports bearing n Housing n Assembly Tips Distortion from housing is undesirable Copyright 2006, Pioneer Motor Bearing Company End Installing and Handling Bearings (partial) Copyright 2006, Pioneer Motor Bearing Company area clean, so as not to drop any foreign material into the bearing during reassembly n Clean joint faces n Joint faces should be tight within 0.001” 0.001” n Avoid striking or scratching babbitt surface n Avoid overuse of gasket cement around the pedestal cap joints Copyright 2006, Pioneer Motor Bearing Company ... stability – tilt pad n Thrust A bearings n Bore bearings n Profile designs load – tilt pad n Optimum n FluidFluid -film C n Reynolds Ref Neale, Neale, Bearings, Bearings, Butterworth Heineman,... Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing Fluid- Film Bearings Babbitted Bearing Overview PIONEER FLUIDFLUID -FILM BEARING WORKSHOP Pioneer Motor Bearing Company August 2006... expertise in fluid film bearings and seals (c) Pioneer Motor Bearing Company, 2006 (c) Pioneer Motor Bearing (c) Pioneer Motor Bearing Company, 2006 / MSME – Machinery dynamics n PhD – FluidFluid-film