1009level0-deg.IAP2P2HP1OFB - PDF document

10385 Drummond RoadPhiladelphia, PA 19154 Telephone: +1 215-824-4000Fax: +1 215-824-4999www.kingsbury.comRepair & Service Division Road , PA 19West Coast219 Burns DriveYuba City, CA 95993Telephone: K References commitment to the customer. In addition,Kingsbury Field Service Technicians andEngineers are available to assist either in person or by phone and other means of communication. Please visit our websitewww.kingsbury.com for further details.1.Sohre, J.S., and Nippes, P.I.,"Electromagnetic Shaft Currents andDemagnetization on Rotors of Turbines andCompressors", Proceedings of the SeventhTurbomachinery Symposium (1978)"Practical Machinery Management for ProcessPlants", Bloch & Geitner, Volume 2, GulfPublishing Company"Thermal Aspects of Fluid Film Tribology",Oscar Pinkus, ASME Press"Theory and Practice of Lubrication forEngineers", by Dudley D. Fuller, Wiley &Sons, Inc.EPRI GS-7352 Project 1648-10 Final Report"Manual of Bearing Failures and Repair inPower Plant Rotating Equipment", MTI 27 26 Section IIIf the collar is not within tolerance, the resul-tant "wobble" (Fig. 36) will force the shoesand leveling plates to constantly equalize, caus-ing rapid leveling plate wear. filter may be all that is required to determinethat a problem exists and that further investi-gation is necessary. Cloudy or discolored oilindicates that a problem exists.A thorough oil analysis can provide very usefuldistress. Be aware that the usefulness of theanalysis is directly related to the informationyou request. As a minimum, the followingParticulate densityParticulate breakdownViscosityWater contaminationChemical breakdownThe amount of particulate, as well as its content, can identify potential trouble spots.Oil viscosity will decrease in time, andwhether or not distress is suspected, it shouldbe periodically evaluated. Water contaminationis extremely unwanted, since it can cause rustfilm, bearing failure. A chemical breakdown ofadditive packages and the presence of unwantedOPERATIONAL DATAPerhaps the most important source of data. Identifying periods of load or speedchanges, recent maintenance, pad temperatureand vibration level trends, or the performanceof related machinery may also help determinethe root cause of distress.Vibration data or an analysis may help discoverexisting problems, as well as examining theremaining bearings in a troubled unit.Kingsbury operates aftermarket support facili-ties capable of inspecting and evaluating allmakes, models, and types of fluid-film thrustand journal bearing designs. In most cases,Kingsbury is able to provide an evaluation and recommended repair, replacement, or performance upgrade at no charge and no Figure 36 Leveling Plate Wear Due ToCollar Wobble CorrosionCorrosion damage (Fig. 34) is characterized by the widespread removal of the bearing lining bychemical attack. This attack produces a latticeworkappearance. The damage may be uniform with theaffected elements being "washed away," leaving thecorrosion resistant elements behind. Corrosion may also affect the rotating collar, run-ner or journal, appearing as random, widespreadrust or pitting. The pits are easily distinguishedfrom electrical pitting, since they are not as Corrosive materials may appear in the lubricatingoil through:Decomposition of oil additivesAcidic oxidation products formed in serviceWater or coolant in lube oilDirect corrosive contaminationBearing housing seals, oil additive packages, andoil reservoir operating temperatures should be evaluated as an initial step in eliminating corrosion. The integrity of cooling coils shouldThe cause of corrosion is best detected by knowledge of the babbitt composition and an oilanalysis. Corrosion can be eliminated by replacingthe lubricating oil. In addition, the entire bearingassembly, oil reservoir and piping should beflushed and cleaned. If the original bearing finishcannot be restored, the bearing must be replaced.The rotating collar, runner or journal surface must also be evaluated and restored to originalcondition, either by lapping or hand stoning.COLLAR/RUNNER/JOURNAL SURFACEThe most commonly overlooked bearing component is the collar. It is the single mostimportant part of the bearing. Collar rotation draws oil into the region betweenthe collar and shoe surfaces. Oil adheres to the collar and is pulled into pressurized oil wedges.This occurs due to the collar surface finish. If theit will not move an adequate supply of oil; toorough, and the bearing shoes will be damaged.Ideally the finish should be between 12 - 16 RMS.be inspected and worked as necessary. Glossy areason the collar can easily be removed by hand scrubbing with a soft 600 grit oilstone. Collarswith significant operating time may have lost theiroriginal surface flatness. This flatness, as well as the surface finish, should be restored. If a split runner is used, it should be separated intohalves and evaluated. Relative motion between thehalves will result in fretting damage to the runner,as well as potential cavitation-like damage to thebearing surfaces.It is very important that the collar faces be parallel, Figure 34 Example of Bearing Corrosion K Section II 25 24 Section IIareas of rapid pressure change. Damage oftenoccurs at the outside diameter of thrust bear-ings due to the existence of higher velocities.This type of damage can also affect stationarymachine components in close proximity tothe rotor.Based on its source, cavitation can be Radius/chamfer sharp stepsModify bearing groovesReduce bearing clearanceReduce bearing arcEliminate flow restrictions (downstream)Increase lubricant flowIncrease oil viscosityLower the bearing temperatureChange oil feed pressureUse harder bearing materialsThe lubricating oil must be filtered orreplaced. In addition to filtering/replacing theoil, the entire bearing assembly, oil reservoirDepending on the extent of damage, voids inthe babbitt can be puddle-repaired. The original bearing finish must be restored.Journal shoes may also be puddle-repaired and refinished. If this cannot be done, theshoes must be replaced. Although the babbitted surface is usually dam-aged more severely, the rotating collar, runneror journal surface must also be evaluated. Thissurface must also be restored to original condition, either by lapping or hand stoning.ErosionErosion damage may appear as localized bab-bitt voids with smooth edges, particularly inthe direction of rotation. Damage is more likely to occur in stationary members.As a rule of thumb, if the babbitt has beenerosion. Since erosion is caused by suddenobstructions in oil flow, it is more likely tooccur in other areas, since the babbitt is underhigh pressure. Once damaged, however, babbitt erosion may occur.Corrective action is similar to that employedemphasis on streamlining oil flow through the Figure 33 Cavitation Damage on OutsideDiameter of Collar Towards Outside Diameter K Section II shaft. The frequency of motion is usually abouthalf that of the rotating speed of the journal. This self-excited motion is frequentlydetrimental to the pad, causing a cyclical loadon the leading edge that erodes away the bab-bitt (Fig. 29 and 30). Pads with a smaller arc-length have been found to be much less prone4-pad bearing. When a bearing must have lessthan five pads and there is a relatively light load,the axial length of the bearing can be reducedto exert more force on the pads. In addition,when there is limited preload on the originalpads, the bearing manufacturer should considerintroducing a relief into the leading edge of thepads in order to eliminate self-excited vibration.CavitationCavitation damage appears as discreet irregularly-shaped babbitt voids which may ormay not extend to the bond line. It may alsoappear as localized babbitt erosion. The location of the damage is important in determining the trouble source.Often called cavitation erosion, cavitationdamage (Fig. 32 and 33) is caused by the formation and implosion of vapor bubbles in 23 Figure 28 Fretting Corrosion of Shell And Housing Figure 30 Spragging Effects On Pad Figure 29 Eroded Babbitt From Spragging 22 Section IIBent shaftThermal cyclingVibrationPerformance data should be reviewed to determineif a vibration increase occurred. The leveling platewings should be examined for signs of excessivewear, indicating the rotating collar or runner is notHigh bearing temperature may also be consideredtemperatures increase, the fatigue strength of bearing materials decrease. The lubricating oil must be filtered or replaced. In addition to filtering/replacing the oil, the entirebearing assembly, oil reservoir and piping shouldDepending on the extent of damage, voids in thebabbitt can be puddle-repaired. The original bearing finish must be restored. Journal shoes mayalso be puddle-repaired and refinished. If this cannot be done, the shoes must be replaced.Although the babbitted surface is usually damagedmore severely, the rotating collar or journal surfacemust also be evaluated. This surface must also berestored to original condition, either by lapping orFretting CorrosionFretting, like fatigue, is due to a cyclical oscillations between two non-rotating surfaces.Prime examples are the contact areas betweenshoe supports and leveling plates, journal bearing shells and the housing (see Fig. 28), andparts with an interference fit, such as the collarfretting corrosion is characterized by a red-orangeiron oxide, which forms on the freshly “machined”steel surfaces. To reduce the risk of recurrence, thereplacement parts should be adjusted to obtain abetween its outer diameter and the housing,which resulted in the typical orange-brown oxidation of the exterior surface of the bearing.SpraggingIn a tilting-pad journal bearing, the upper padstypically receive no load. These pads back and forth between the pivot point andthe Figure 26 Edge Load Journal Shell With Babbitt Mechanical Fatigue Figure 27 Fatigue K Section II sourcesresult in pitting damage, they differ inorigin and destructive capabilities. Electrostatic shaft current (direct current) is themilder of the two. Damage progresses slowly,lowest resistance to ground. It can be attributedto charged lubricant, charged drive belts, orimpinging particles.This type of shaft current can be eliminatedwith a grounding brushes or straps. Bearing isolation is also recommended.Electromagnetic shaft current (alternating current) is stronger and more severe than electrostatic current. It is produced by the magnetization of rotating and/or stationarycomponents. This type of current will notalways occur at the location of lowest resistance.Because the current is stronger, bearing damageis often accompanied by journal, collar or runner damage.Electromagnetic currents are best eliminated byGrounding brushes or straps may or may not be helpful. The bearings should be isolated.The lubricating oil must be filtered or replaced.Pitting damage often blackens the oil and fills itwith debris. In addition to filtering/replacingthe oil, the entire bearing assembly, oil reservoirrestored. Journal shoes typically must bereplaced,but if the correction leaves the bearingreused. The condition of the rotating journal,collar or runner surfaces must also be evaluated.It must be restored to original condition, eitherby lapping, hand stoning or replacement.FatigueFatigue damage (Fig. 25, 26, 27) may representbabbitt. The cracks may appear to open in thedirection of rotation. Pieces of babbitt may spallout or appear to be pulled away in the direction ofrotation. The cracks extend toward the babbittbond line, and may reveal the shoe backing. damage, but concentrated cyclic loading is usuallyinvolved. The fatigue mechanism involves repeatedoccurs more rapidly with poor bonding. It is important to note that fatigue damage willoccur without poor bonding. Fatigue can occurwhen conditions produce concentrated cyclicMisalignmentJournal eccentricityImbalance 21 Figure 24 Stray Shaft Currents/Electrical Pitting (Frosting) Figure 25 Edge Load Showing Babbitt Mechanical Fatigue 20 Section IIHydrogen BlistersIn certain occasions, hydrogen gas becomestrapped during the casting or forging of partsmade of steel. If the steel base is babbitted andthe gas eventually migrates to the surface, blisters can form in the area, significantly weakening the babbitt bond (see Fig. 22).Thermal annealing has been proven to preventblisters from forming by diffusing out hydro-gen before the part is babbitted. In Figure 23,the annealing process was accidentally missedand large hydrogen blisters emerged during themachining process.Electrical Pitting Electrical pitting (Fig. 24)appears as roundedpits in the bearing lining. The pits may appearfrosted, or they may be blackened due to oildeposits. It is not unusual for them to be verysmall and difficult to observe with the unaidedeye. A clearly defined boundary exists betweenthe pitted and unpitted regions, with the pit-ting usually occurring where the oil film isthinnest. As pitting progresses, the individualbegin to overlap. Pits located near the bound-ary should still be intact. The debris that entersthe oil begins abrasion damage. Once the bear-ing surface becomes incapable of supportingan oil film, the bearing will wipe. The bearingmay recover an oil film and continue to oper-ate, and pitting will begin again. This processmay occur several times before the inevitablecatastrophic bearing failure.Electrical pitting damage is caused by intermit-tent arcing between the stationary and rotatingmachine components. Because of the smallfilm thicknesses relative to other machineclearances, the arcing commonly occursthrough the bearings. Although the rotatingand other stationary members can also beaffected, the most severe pitting occurs in theElectrical pitting can be electrostatic or electromagnetic in origin. Although both Figure 22 Hydrogen Blisters In The BabbittFigure 23 Large Hydrogen Blisters Figure 21 Oil Circulator Fused To Collar K Section II Verify that the quantity and quality of oil flowing to the bearing is sufficient. These values should be available from the bearing manufacturer. If thermal ratcheting has occurred, examine theRemove the cracks and restore the original shoesurface. If this cannot be done, replace theshoes. Journal shoes typically must be replaced,but if the correction leaves the bearing withindesign tolerance, the bearing may be reused.The condition of the rotating journal, collar orrunner surfaces must also be evaluated. It mustbe restored to original condition, either by lapping, hand stoning or replacement.Oil StarvationIt is often possible to distinguish oil starvation(i.e. the total absence of lubricant) from a lessthan adequate oil flow by closely examining thebabbitted surface of the bearing.In Fig. 19, the babbitt has been completelyremoved from the shoe surface. If there hadbeen any oil flow to the bearing, it would havesufficiently cooled the region to allow the moltenbetween the shoes. With no oil coming in atthe leading edge of the shoe, this area typically shuts down, resulting in the babbittdiameter in Fig. 20.In combination assemblies, such as Kingsbury’sto destruction of the journal shell, where themolten babbitt can pool in the lower half. Theextreme temperatures in such cases can lead tothe fusion of the oil circulator to the collar (see Fig. 21), which has no quench marks inever reached the parts. 19 Figure 19 Complete Babbitt Removal Figure 20 Outer Edge Babbitt Erosion 18 Section IIhardness will prevent foreign particles fromembedding in the bearing lining. This allowsabrasion damage to occur. Pieces of tin oxidemay break off during operation and score thejournal, collar, or runner. The formation of tinoxide will also eliminate bearing clearance. This damage may be stopped by eliminatingsome or all of the contributing elements. Thelubricating oil must be replaced. A reduction in oil temperature may also discourage theformation of tin oxide. In addition to replacing the oil, the entire bearing assembly, oil reservoir and pipingspirits. The bearing shoes should be replaced.The condition of the rotating journal, collar orrunner surfaces must also be evaluated. Theymust be restored to original condition, either by lapping, hand stoning or replacement.OverheatingOverheating damage may represent itself in(Fig., cracking, wiping or deformation. Repeatedcycles of heating may produce thermal ratcheting(Fig. 17), a type of surface deformation thatoccurs in anisotropic materials. These materials possess different thermal expansion coefficientsin each crystal axis.Overheating may be caused by numeroussources, many of which concern the quantityand quality of the lubricant supply. Among thepossible causes are:Improper lubricant selectionInadequate lubricant supplyInterrupted fluid filmBoundary lubricationThe following conditions may also cause overheating:Improper bearing selectionHP lift system failurePoor collar, runner or journal surface finishInsufficient bearing clearanceExcessive loadOverspeedHarsh operating environment Figure 17 Thermal Ratcheting Figure 18 Overheating, Oil Additives Plated Out K Section II the oil film. The debris may embed itself in thesoft babbitt, exhibiting a short arc on the shoesurface, ending at the point where the debrisbecomes embedded. Depending on the debrissize, the scratch may continue across the entireshoe surface. Abrasion damage becomes worse with time.Surface scratches allow an escape for lubricatingoil in the oil wedge, decreasing the film thick-ness. This will eventually lead to bearing wipe.Another source of abrasion damage is a roughjournal, collar or runner surface. Roughnessmay be due to previous abrasion damage. Itmay also be from rust formed after extendedperiods of down time. New bearings should notbe installed when the rotating component isRandom scratches, which may run a staggeredpath both circumferentially and radially, aremore likely to appear in the unloaded bearingor unloaded portion of the bearing. In a thrustbearing, it may indicate excessive end playindicate careless handling at installation or disassembly.In order to eliminate abrasion damage, thelubricating oil must be filtered. If the oil cannot be filtered or has degraded, it should bereplaced. It is important to evaluate the filteringsystem, since the problem may be an incorrectlysized filter. The filter should only pass debrissmaller in size than the predicted bearing In addition to filtering/replacing the oil, theentire bearing assembly, oil reservoir and pipingshould be flushed and cleaned. The originalbearing finish should also be restored. Journalshoes typically must be replaced, but if the correction leaves the bearing within design tolerance, the bearing may be reused.Although the babbitted surface is usually damaged more severely, the rotating collar orjournal surface must also be evaluated. Debrispartially lodged in the babbitt may score thesteel surfaces.These surfaces must be restored by lapping or hand stoning.Tin Oxide Damage This is one of several electrochemical reactionswhich eliminate the embedability properties of a fluid-film bearing. Tin oxide damage (Fig.is recognizable by the hard, dark brownTin oxide forms in the presence of tin-basedbabbitt, oil and salt water, beginning in areasof high temperature and pressure. Once it has formed, it cannot be dissolved, and its 17 Figure 16 Tin Oxide Damage 16 Section IIThe shoe pivot is the hardened spherical plugin the rear face of each thrust shoe. Based onthe magnitude and nature of the thrust loads,the spherical surface will flatten where it con-tacts the upper leveling plate. The contact areawill appear as bright spot on the plug. If evi-dence of hard contact exists (a large contactspot), rest the shoes (pivot down) on a flat surface. If the shoes do not rock freely in alldirections they should be replaced.The pivot can also appear to have randomcontact areas, indicating excessive end play, or it may be discolored, indicating lack ofIndentations routinely occur where the shoedirection of rotation. Displaced metal exhibit-ing a coarse grain may indicate erosion unwanted contact. Depending upon the shapecorrosion or undesirable stray shaft currents.SHOE SURFACEWhen evaluating the shoe surface, the firststep is to determine the direction of rotation.This may be accomplished by evaluating:Abrasion scratchesDiscoloration (75-75 location)Babbitt flowBabbitt overlayThrust shoe/base ring contactUse caution when evaluating babbitt overlay(babbitt "rolled over" the edges of the shoes),with no babbitt voids or overlays. The dullgrey finish of a brand new shoe may remainit may appear glossy in spots or in its entirety.Routine thermal cycling of the bearing maymottled pattern in the babbitt. This is harmless, providing the shoe is flat and SCRATCHESAbrasionA bearing surface exhibiting circumferentialscratches is the result of abrasion damage (Fig.15). Abrasion is caused by hard debris, which islarger than the film thickness, passing through Figure 15 Thrust Shoe Surface Abrasion K Section II This section of the paper presents an overviewof a structured bearing troubleshootingThe approach is developed based onpotential effects of related parameters. Ofticular interest are the rotating journal, collar,or runner, the babbitted shoe surface, alltional and performance data must also be considered.The following appris centered on equalizing thrust bearings.These bearings contain the most moving parand are widely used. The remarks made hereinvaluating bearing distress, the babbittedshoe surface is commonly the only area thatexamined. Although a great deal of informa-tion can be extracted from theance, additional information exists elsewherThese "secondary sourmation often prove to be verthe babbitted surfaces arusually destroyed ina catastrophic bearing failure. Even a bearingof distress, hides valuable information.e modes areoccurs when a bearing can no longer supportan oil film. Through the prudent use of tem-perature and vibration monitoring equipmenroutine oil analyses, lubrication system evtions and machine operational performanceeviews, bearing distress may be identified andaluated before catastrophic failureBearing health is commonlymonitored throughthe use of temperature measurements. Beaware that temperature sensors are mounted inof locations, with a correspond-ing variation in significance. The specific in order for the measured temperature data toe any real value. To begin an evaluation, the bearing assemblyshould be completely disassembled. In this manner, all of the bearing components may be evaluated. Do not clean the bearing, since valuable information may be lost.Examine the base ring. During routine opera-tion, the lower leveling plates (LLP) will formthe dowels that locate them. The indentationsshould be identical and barely noticeable. Deep,wide indentations are an indication of a highload. The rocking strip on the bottom of thepresents another indication of bearing load.be determined, since deposits are often trappedin the base ring. Evidence of water contamina-tion, particularly in vertical machines, may goLEVELING PLATESThe spherical pivot in the rear of each thrustshoe rests in the center of a flat area on thehardened upper leveling plate (ULP). This flat-tened area is susceptible to indentation due tothe point contact of the pivot. The indentationis easily identified by a bright contact area. Thisarea indicates where the shoe operates on theULP, and its depth gives an indication of load.Close examination of the upper leveling platenear the contact area may also produce As noted previously in SECTION I, the upperleveling plates interact with the lower levelingplates on radiused "wings." The upper levelingplates are typically hardened; the lower levelingplates are sometimes not. When new, the leveling plates have line contact. There is littlefriction between the wings, and the bearing can react quickly to load changes. Depending on the nature and magnitude of thethrust load, the wing contact area will increasein time. The contact region of the wings, againnoted by bright areas, will normally appearlarger on the lower leveling plates. If the rotat-the leveling plates will continuously equalize,causing rapid wear. 15 Of these, bearing health are commonly monitored through the use of temperaturedetectors. The temperature of the bearing variesvaries across and through the shoe. Therefore,for the measurement to be meaningful, thelocation of the detector must be known.The recommended location for a detector istermed the “75/75 location” on a thrust shoeface, i.e. 75% of the arc length of the shoe inthe direction of rotation and 75% of the radialof the shoe measured from the ID to theOD. In a journal bearing, sensor location shouldbe 75% of the arc length on the center line ofthe shoes. This position represents the most critical area because it is the point where peakfilm pressures, minimum film thickness, and hottemperatures co-exist. 14 Section IFigure 14 Vertical Thrust Bearing Oil Sump and Cooling Coils A cooling system is required to remove the heatgenerated by friction in the oil. The housing maysimply be air cooled if heat is low. Vertical bear-(Fig. 14), but the oil can also be cooled by anexternal cooling system as typical in horizontalapplications. The heat is removed by a suitableheat exchanger.OPERATION AND Under operation, the capacity of hydrodynamicbearings is restricted by minimum oil film thick-ness and babbitt temperature. The critical limit for low-speed operation is minimum oil filmthickness. In high-speed operation, babbitt temperature is usually the limiting criteria.Temperature, load, axial position, and vibrationmonitoring equipment are used to evaluate theoperation of the machine so that problems may beidentified and corrected before catastrophic failure. 13K Section I Figure 12 Leading Edge Groove Lubricant Flow Path. Figure 13 Leading Edge Groove (LEG) Journal Bearing 1 –Oil enters annulus in base ring.2 –Oil passes through radial slots 3 –Oil flows through clearance of rotating thrust collar.6 –At the collar rim, oil is thrown off into space around the collar.7 –Oil exits tangentially through 12 Section I Directed lubrication directs a spray of oila hole or nozzle directly onto the collar (jour-nal) surface between the shoes. Rather thanto the moving surface allowing the bearingrun partially evacuated. Such a method oflubrication reduces parasitic churning lossesaround the collar and betwn 1984 Kingsbury introduced its Leadingdge GroovThrust Bearings (Fig. 11),another technology developed for high techmachines. In addition to reducing oil floss, LEG lubrication grreduces themetal temperature of the shoe surreduces oil florequirpowloss while improving the load safety and rthe bearing or wetting the surface,design introduces cool oil dirthe oil 12), insulating the shoe surfaceoil that adheres to thesame technology is applied to tintibearings (Fig. 13). Figure 10 Thrust Bearing Typical Oil Flow Path Figure 11 Leading Edge Groove through a filter and cooler. loose, the unloaded side shoes are too far fromthe shaft to develop a film pressure and canFiller plates and shim packs provide a meansthe rotating elements. Adjusting screws arePreload pertains mostly to journal bearingsand is a measure of the curvature of the shoeto the clearance in the bearing. The shoe cur-vature is another parameter which effects thehydrodynamic film, allowing design variationsin bearing stiffness and damping to control thedynamics of the machine. The geometry anddefinition are given in Figure 9.LUBRICATION For hydrodynamic bearings to operate safelyand efficiently, a suitable lubricant must alwaysbe present at the collar and journal surfaces.The lubricant needs to be cooled to remove the heat generated from oil shear,re-entering the bearing. It must also be warmenough to flow freel, and filtered so that theticle size is less than the minimumarious methods are applied to provide lubri-cavities can be flooded with oil such as vercan also be provided with pressurized oil fromtintipi rad For high speed bearings, the frictional lossesfrom oil shear and other parasitic losses beginto increase exponentially as the surenters a turbulent regime. lubricant required increases proportionatelIndustry ends for faster, larger machinesnecessitated the design of lower loss bearings.This has been incorporated by 11K Section I Figure 9 Journal Bearing Preload 10 Section I compensate for manufacturing tolerances bydistributing the load more evenly betweenthrust shoes. The leveling plates compensatebetween the collar and the housing’s support-ing wall. A description is given later under theThe lubricant is another important “element”of the bearing (See Fig 8-1). The loads aretransmitted from the shaft to the bearingthrough the lubricant which separates the partsand prevents metal-to-metal contact. Thelubricant also serves to carry heat caused byRELATED PARAMETERS EQUALIZATION In a machine, alignment and load distributionare not perfect because of manufacturing elements. There are three areas of concern:1.The squareness of the collar (and parallelism2.The alignment of shaft with the bearing andstack-up of the bearing parts and the housingbores and faces.3.The alignment of shafts between machineswhich are aligned and coupled together on site.Misalignment of the shaft to the bearing andhousing, and between machines is considered assembly if to operating changing conditions such as: tion, shaft deflection movement caused move-of foundations, leveling plates. The lower leveling platesand so on around the ring. This featureEND PLAY AND RADIAL CLEARANCE Figure 8-1 Pivoting Shoe Hydrodynamic Film Formation and Alignment Features K Section I 9 Figure 7 Thrust and Journal Bearing Part Schematic 8 Section I about the theoretical center of pressure, the oilpressures would automatically take the theoretical form, with a resulting small bearing ear of the metal parts.In this way a thrwith several such blocks set around in a circletintipi This section discusses the associated thrustbearing parts, with corresponding journalbearing information in parenthesis.ATING COLLAR (JOURNAL)The collar transmits the thrust load from therotating shaft to the thrust shoes through thet can be a separate partattached to the shaft by a key and nut orshrink fit, or it may be an integral partThe collar is called a runner in verticalthe radial direction, the shaftjournal shoes through the lubricant film.) Indrodynamic bearings, the fluid film is onWith thisand the information from HYDRODYNAMICrealized: 1.The stack-up of tolerances and misalign-ment in hydrodynamic bearings has to be less2.The collar surfaces must be flat and smooth(and journal surface cylindrical and smooth) inlubricant to the surface.THRUST SHOE (JOURNAL SHOE) ASSEMBLYis loosely constrained so it is free to pivot. The shoe has three basic features - the babbitt,body, and pivot, and so is usually referred to as an assembly.BABBITT metallurgically bonded to the body. As withthe collar, the babbitt surface must be smoothThe babbitt is a soft material (compared to theshaft) which serves two functions: It traps andimbeds contaminants so that these particles donot heavily score or damage the shaft. It alsoprotects the shaft from extensive damage shouldexternal conditions result in interruptionof thefilm and the parts come in contact.BODYThe shoe body is the supportingstructure which holds the babbitt and allowsfreedom to pivot. The material is typicallysteel. Bronze is sometimes used (with or Chrome copper is used to reduce babbitt tem-perature.PIVOTThe pivot allows the shoe to rotateand form a wedge. It may be integral with theshoe body, or be a separate insert. The pivotsurface is spherical to allow 360 rolling freedom. shoes against rotating so as to allow freedom topivot. It may have passages for the supply oflubricant, and contain features to adapt for misalignment and tolerance in the parts. Thebase ring (aligning ring) is keyed or doweled tothe housing to prevent rotation of the bearingassembly.LEVELING PLATES The leveling plates (not applicable to journalbearings) are a series of levers designed to Bearings transmit the rotating shaftto the foundation or machine support.Hydrodynamic bearings transmit (float) thea self-renewing film of lubricant.Thrust bearings support the axial loads. Radialloads are supported by journal bearings.zontal or vertical depending on the orientationassembly ovassembly around the shaft.Based on his theoretical investigation of OsborneReynolds showed that oil, because of its journal and its resistance toflow (viscosity), is dragged by the rotatithe journal so as to form a wedge-shaped filmbetween the journal and journal bearing(Fig.This action sets up the pressure in the oilfilm which thereby ts the load (Fig. 5). edge-shaped film was shown byReynolds to be the absolutely essential featureof effective journal lubrication. Reynolds showed that “if an extensivflat surface isrubbeovery inclined surface, oil beingesent, there would be a pressurwith a maximum somewhere 7K Section I ROTATION Figure 4 Hydrodynamic Principle 100910 20 30 40 50 60 70 80 Oillevel0-deg. Sin 0 Cos 0 JIAP2P2HP1OFB Figure 5 A figure from Reynold’s Paper “On Figure 6 Illustration from a page from AlbertKingsbury’s Paper “Development of 6 Preface Indeed, the invention made it Figure 3 Hydrodynamic Thrust and Journal Bearing INDUSTRIAL APPLICATIONSHydroelectric GeneratorsHydraulic TurbinesSteam TurbinesGas TurbinesDredge PumpsBoiler Feed PumpsHigh Speed BlowersCentrifugal CompressorsElectric MotorsDeep Well PumpsOil PumpsCooling PumpsPulp RefinersTurbochargersAir PreheatersRock CrushersExtrudersSHIPBOARD APPLICATIONSMain Propeller JournalsPropeller Line Shaft Turbine-Generator SetsMain Gear BoxPumpsBlowersAuxiliary Machinery K Preface tolerances and finishes required for the hydro-dynamic bearings to operate. After properlyfinishing the runner and fitting the bearing,This bearing, owing to its merit of running75 years with negligible wear under a load of220 tons, was designated by ASME as the23rd International Historic MechanicalEngineering Landmark on June 27, 1987.The cylindrical hydrodynamic journal bearingis the most basic hydrodynamic bearing. It hasa cylindrical bore, typically with two axialgrooves for lubrication. This bearing has a highload capacity, and the simple design is compact,bi-rotational, and easy to manufacture. However, as the design speeds of machineincreased, it was found that this bearing hadlimitations due to oil whirl. Oil whirl isveryamplitudes, forces, and cyclic stresses that arEfforts to suppress and eliminate oil whirl havresulted in a variety of fixed geometrywhich are modifications to the profile of thethe lemon bore,ncept (Fig.bearing to be 5 Figure 2 Hydrodynamic Journal Bearing 4 Preface HISTORYIn the late 1880s, experiments were conducted on the lubrication of bearing The idea of “floating” a load on aew from the experiments ofBeaucower and the theoretical work thtust dgatipi, ot bcaringtintipi rad tintipi rad In 1896, inspired by the workof OsborneDr. Kingsbury, the test bearings ran well.loads at the time). The loads wereIn 1912, Albert Kingsbury was contracted bythe Pennsylvaniater and Power Companyto apply his design in their hydroelectric plantat Holtwood, PA. The existing roller bearingswere causing extensive do Figure 1 Tintipi Pad K Preface 3 During every second of every day, machines all over the world are working to provide the products we demand.These machines rely on the successful support of bearings. If a machine goes off line, extreme pressure is placedon those involved to correct the problem(s). It is the intention of this presentation to assist the reader in problemsolving by providing background information on hydro-dynamic bearings and distress modes.Bearings which support rotating shafts can be classified into four basic categories:Rolling contact– load supported by balls or rollers.Hydrostatic– load supported by high pressure fluid.Hydrodynamic– load supported by a lubricant film.Magnetic– load supported by magnetic fields. c, tintipi rad (anso canngd rivotgd shog Holtwood Generating Station (See page 4) 2 Table Of Contents PrefaceHistoryTypical ApplicationsSection I Hydrodynamic BearingsHydrodynamic Principle Basic Thrust (& Journal) PartsRelated ParametersOperation And Monitoring Section IIShoe SupportShoe SurfaceCollar/Runner/Journal Surface 3 4677910151513151515161624242526 Sin 0 Cos 0 0 0-1 0-2 0-3 0-4 0-5 0-6 0-7 0-8 0-9 1100910 20 30 40 50 60 70 80 Oillevel0-deg.JIAP2P2HP1OFB LEVELING PLATELOWER LEVELING PLATEUPPER LEVELING PLATETHRUST SHOE ASSEMBLYRETAINING PLATE SCREWRETAINING PLATERETAINING PLATERETAINING PLATE SCREWRETAINING PLATERETAINING PLATEANTI-ROTATION PIN OPERATION AND TROUBLESHOOTING OF