New Techniques for Aligning andMaintaining Large'Ring Gears

Abstract

This paper presents two new techniques foraligning and maintaining large ring gears. Onetechnique uses the UOperating-T emperaures"in th mesh ,of a ring gear set 10 evaluate therelative distribution of load across tbe face of'the gearing. The other uses "Stop-Action"photography to record the surface conditionand lubricant film on the pinion teeth. Thesetechniques are recommended for use inconjunction with conventional maintenanceprocedures, Combined they optimize the gearset performance at the time of initial insralla-tion and then for the Lifeof the gearing if 'theyare used during subsequent maintenanceprocedures ..

INTRODUCTIONThe "Operating- Temperatures" align-

ment and the "Stop-Action" photographytechniques have been under developmentat Falk for the last 5 to 6 years. Both havebeen rigorously tested on well over 100different ring gear sets from various in-dustrial applications. The gearing rang-ed up to 35 feet in diameter, 31 inchesof face, and had pitches as course as %DP. The techniques and the instrumen-tation required to' use them are describedin this paper. Also presented is some re-cent work which utilizes these proceduresand interprets the results ..

ALIGNMENTConventional Alignment MethodsThere are basically three conventional

methods whi.ch are used for aligning ringgear sets. These ale presented here Itoprovide a reference for comparison withthe MOperating- Temperatures" method.The first uses feeler gages to measure theclearance at each end of the face, be-tween the load flanks of the gear teethwhen they are clean and contacting.With the second method, prussian blue.lamp black, 'or an equivalent is applied

36 Gear feehnol'ogy

M. AntosiewkzThe Fall< CorporatienMilwaukee, Wisconsin

to several, cleaned pinion teeth. That areaof the pinion is then manually rotatedinto mesh with the gear and the teeth arebumped. together transferring a contactpattern to the gear and the teeth arebumped togethertr-ansferring a contactpattern to the gear where i'I can be in-spected. The third method involvescleaning and dyeing the load flanks ofseveral pinion and/or gear teeth withlayout dye. The gearing is then operatedunder load for several hours, stoppedand manually rotated toa convenientlocation to enable inspection of the dyedteeth. Areas on the teeth where dye isremoved indicate the presence of contact.

These conventional techniques havecertain disadvantages. The reeler gageand bump check methods indicate onlystatic contact conditions. Since underload, the pinion, the gear, and associatedequipment can deflect, twist and / ormove through the internal clearance ofthe bearings, operating alignment maydiffer from static. The layout dye methodoffers a means of adjusting operatingalignment to produce ful.l face contact.Therefore, it can indicate when the en-t:ire face width of a tooth is carrying someload. However, it does not indicatewhether the load intensity at one side ofthe face is greater than the load intensityon the opposite side.

Operating Te.mperatures MethodThe "Operating-Temperatures" tech-

nique is a procedure, whereby, a uniformload intensity can be obtained across Itheentire face. This procedure is recom-mended for optimizing alignment aftergood initial a.l.ignment has been estab-lished using conventional methods. Thebasic premise behind the use of "Op-crating-Temperatures" is that misalignedgear sets experience non-uniform load in-tensity across the face of the gearing (Fig.1). This variance in load intensity results

Fig. 1

in higher operating temperatures at thepoints of higher load. Therefore, mis-alignment will cause the operating tem-perature on one side of the face to behigher than on the other. As a result,equal temperatures at both ends of theface indicate a uniform. load distributionand optimum alignment. Unequal. tern-peratures indicate that the gear set maybe misaligned with greater load int'ensityon the side of the face with the higheroperating temperature ..

Operating temperatures can be mea-sured with either an infrared radiationthermometer, while the gearing is op-erating, or witha. surface contact pyro-meter immediately after stoppin.g. (For

AUIHOR:

rvm. M. ANfOSIEWICZ is .the MQruzger ofResearch I:ItId Technology a! The Falk Corpo-ration in Milwaukee, Wisconsin. He graduatedfrom the University of VY:isCOns1n with a B.S.in Engineering, ,and later he received' a Mastersin Business Admini.stratJ~on. His activities at.Falk include many aspects of gear design,mcmufaclure and service.

Fig. 2 - COl\tact Pyrometer

PilCHLINE

MEASUREMENTPOSITION-~-"rI~I

INFRARED AXIS OFINSTRUMENT INFRARED il-

PINIONAXIS

Fig. 3

F\I. ,- Measurement Positions

typical instrument specifications. see Ap-pendix A).

When using the surface contact pyro-meter procedure. 'the probe is placed onthe load flank at the pitch line of at leastone tooth (Fig. 2). The m a urements aretaken directly through the lubricant filmand im_mediately after stopping the gear~ing, since temperatures begin 'to changewithin minutes.

The infrared measurements are takenwhile the gearing is operating by point-ing the inJrared radiation m asuring in-strument perpendicular to the axis of thepinion and then aiming at the measure-ment position on the load flank along thepitch line (Fig. 3).

Examples ofE valua'l:ingOperating Temperatures

Five measurement positions were se-lected along the face of the min pinionin Fig. 4. One measurement was takenat each end of the face . . . ane at thecenter ... and two, additional midwaybetween these points. It is very impor-tant that infrared measurern nts be takenalonga straight horizontal line (as il-lustrated) in order to obtain the pitch lineposition .. Deviations from this horizon-tal will produce erroneous data.

Temperature measurements can alsobe taken on the gear, however. themagnitudes of the temperatures and thetempera'ture diHerentials across the gearface have been found to be smaller thanthose or the pinion and ] ss sensitive tochanges in alignment. Therefore, thepinion temperatures are considered moresuitable for use in "Operaeing-Tempera-tures" alignment evaluations.

Fig. 5 illustrates the pinion temperaturedistribution of a gear set having optimumalignment. The temperature gradient.which is the temperature at Position 1minus the temperature at Position 5, iszero indicating that the load int,ensity isthe same on both ends of th pinion.Position 1 is taken toward the mill endof the pinion face.

Fig. 6 illustrates the temperaturedistribution of agear set having pooralignment. The temperature gradient of'the pinion is +40 if indi.ca'ling thatmisalignment is producing higher loadintensity on the mill side of the pinion.A negative gradient would indicatehlgher lead toward the opposite side ofthe pinion fa.ce.

September/October~985 3,7

Poor Ahgnme.nl: of Ciear Sal

.2~O --- -

fig. 6 - Temperature Distributionfig. 5 - Temperature Distribution

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38 Gear Technol'ogy

Align.ment TechniquesIn addition to establishing a more

uniform load distribution, the "Operat-ing- Temperatures" technique offers twcconveniences. First. when using thepyrometer, it is not necessary to connectan inching drive and rotate the gearingto view the contact patterns. Second, in-frared techniques are able to sense thetemperatures without stopping the mill.

The major limitation to using 'tempera-tures is that the surface condition of theteeth might influence the temperatureand cause a false indication of alignrnent.Therefore, the presence of severe surfacedistress, recent scoring, wear pads, highpoints on the teeth, or other profiledisturbances, should be considered wheninterpreting the temperatures ..

.InstrumentationBoth the surface contact pyrometer

and the infrared instrument have advan-tages and limitations. The pyrometer hasthe advantage of accurate temperaturemeasurement and simplicity of use. It hasthe disadvantage that the gearing mustbe stopped and, since temperatures beginto shift rapidly alter stopping, only oneor possibly two teeth can be measured.

Infrared has the advantage that thetemperatures are measured during actualoperating conditions. The temperaturesrecorded are, therefore, not changingwith time as for the pyrometer, Also, theinfrared averages these operating tern-peraturesover many teeth at a givenmeasurement position and, therefore,represents an overall alignment ratherthan the alignment of one or two par-ticular teeth.

The primary limitation of the infraredis that it must be calibrated for the in-frared energy emittance or emissivity ofthe pinion. This emissivity is essentiallythe relationship between the actual tern-perature of the pinion teeth and theamoent of infrared energy tht is emittedfor that temperature, It can be influencedby the type of lubricant. the lubricantfilm, and the tooth loads. Its value isdetermined by obtaining pyrometer mea-surements and then adjusting the infraredinstrument to produce Ithe same values.Experience has indicated that for varioustypes of gear applications and lubricantsthe emissivity values may differ. How-ever, the typical values appear to. be inthe order of 0..7 to.0.8. Since only relative

and not absolute Itemperatures across thepinion face are desired toevaluate align-ment, a value of 0.7 or O.B may be usedand the measured temperatures consid-ered nominal.

During the last five to six years, Falkhas studied the gearing of over 100 dif-ferent ring gear sets. The study was basedprimarily on mil] gearing and has notbeen tested as thoroughly on kilns,because it is believed that the heat fromthe kiln along with the slow speed of thegearing mi,ght be misleading to infraredmeasurements. For mill gearing, detail-ed formulas have been developed topredict the align~ent corrections re-quired based on the measuredtemperature gradients. A study coveringthis Is presented in Reference 1.However, Ior most mills, with only onpinion rotating out of mesh and locatedapproximately 20 to 30 below the millhorizontal, equation 1 gives the approx-imate size of shim required to correct thealignment. This shim would be remov-ed from or added under the appropriatepinion bearing to reduce the temperatureand load intensity on the 'end of the facewhere it is the highest.

Equation 1

BearingShim _ Gradi nt Span

Designload

lO,OCIO Face Operatin-&load

Example:Consider a 3000 horsepower mill with

a singl pinion having a 39°F tempera-ture gradient. The bearing span is twicethe face width and the mill is operatingat 2600 horsepower. The computed shimvalue would be:

3910,000

3,0002,600

=.009" ..2

Therefore,a .000"sh.im would beadded. or removed from under the ap-propriate bearing to reduce 'the load in-tensity on the high temperature end ofthe pinion.

Once an alignment correction is made,the mill should be allowed to operate forat least. twenty hours in order to. reachits steady state operating temperatures.The alignment should then. be recheckedto determine whether further adiustmentsare necessary, GeneraUy. when a gradientof lSOF or less is obtained.a. satifactoryalignment has been reached.

Fig. 7 series. Fig. 7A is a. "Stop-Action"photo taken of a mill pinion duringoperation just seconds before tn gear-ing was stopped. Fig, 7B was taken a fewseconds afler the gearing had stopped.Some lubricant had dropped on th pin-ion from the gear above. Fig..7C presentsthe dean d teeth of the pini.on. Thesephotos indicate that the "Stop-Action"photo gives a good representation of theappearance of the lubricant film andtooth surface conditions a thy wouldappear had the gearing been stopped fora visual inspection.

Fig ..8 illustrates the history document-ing capability of "Step-Action" photos.This series records the tooth surfaces ofa particular pinion over a one yea1period. InjtialIy the gearing was found 10

be scuffed and some pitting had occurred(Fig. SA). Two months later (Fig..861. thecondition was found to be improving ..This improvement continued through theremainder of the year (Fig ..8e and 80).Had the pitting become worse, correctivea tion could have been planned. and non-scheduled downtime avoid d. Thesignificance of this series is that thephotographs provide a. far better historythan memory. notes or sketch fromwhich to make maintenance decisions,

P.hotographic TeehniqueThe photographic equipment required

to obtain "Stop-Action" photos is read-ily avail.able. relatively inexpensive andsimple to 'Use. The camera is 3, .3S mmsingle lens reflex type having a 50 mmfocallength lens. Stopping the motion of

sepTember/OCtober 1985 3'9

Stop, Action Photos

The illustration above describes thesurface condition and lubricant film anthe pinion teeth of 3 ring gear set. It isa "Step-Action" photo taken while thegearing was operating and provides 3.

permanent detailed description of thetooth surface conditionand the lubricantfilm existing on the pinion at the time thephoto was taken. Surface distress suchas scuffing, pitting and wear can readilybe detected, By observation af the lubri-cant film, misalignment and lubricantcontamination can at times be found.When "Stop-Action" photographs areused in conjunction with "Operating-Temperatures," misleading temperaturerises and its cause can be identified. Anexample would be high temperatures dueto. localized scuffing when a lube spraynozzle fails ..

The advantage of the "Stop-Action"photo is that it can be obtained withminimal eHort. simple camera equip-ment, and most importantly, w.ithoutstopping the gearing and interruptingproduction. It contains informationuseful to maintenance and engineeringpersonnel for evaluatingthe performancehistory of the gearing and for detectingthe need for corrective actions ..]t is alsoa. means for recording and com-munlcatingteoth conditions and lubri-cant films 'to mill builders and gearmanufactur rs for review and appraisal.

The ability of "Stop-Action" photos tocapture the tooth surface condition andlubricant film is further illustrated itn the

Pig,.7-0peratin~ Teeth V5, Static

7B Static

7C Cleaned Teeth

the puuon is accomplished with anautomatic electronic flash having a guidenumber of about 100 (ASAloo) orhigher. and also a remote sensor whichcan be mounted on the camera. hot shoe.Color slide film (ASAl60 or ASA2oo)has worked well andis recommended.Print type film is nor recommended sincethe colors of the prints can be influenc-ed during processing.

Fig. 9 illustrates the positioning of thecamera and flash. The camera should becentered and focused on the load Hankof the pinion teeth until the cameraviewer is filled by the pinion teeth. Theflash should be set to automatic opera-tion Ior an aperture of approximately£5.6, The camera lens should be set to thesame aperture, The remote sensor should

40 Gecr Technology

7A Operating

be positioned on the camera hot shoe andthe flash oriented at approximately 300

to the helix in order to minimize reflectedglare from the tooth surface.

Once the proper camera and flashposition is attained. the shutter button isdepressed. This opens the camera lens.The flash will then fire in approximately1/5.000 to 1130,000 of a second stopp-ing the action of the gearing like astroboscope and exposing the film. Thecamera shutter then closes and the "Stop-Action" picture is obtained ..

Both "Operating- Temperatures" align-ment and "Stop-Action" photographyprovide useful infor .•ration regarding theoperation of large ring gearing. Presentedhere are some ways that these twotechniques have been used, both in-dividually and in combination. to gammore insight into ring gear alignment andlubricant films. Presented first. is adiscussion of transient shifts in the align-mentof a mill gear set :from start-up tosteady-state conditions. This is followedby an investigation into the influences oflubricant rype. viscosity and operatingtemperature on the appearance of thelubricant as captured in "Stop-Action"photos.

Aljgnment Transient ShiftsAs previously indicated. static align-

ment and operating alignment may bedifferent. One possibl source of this dif-ference •. (discovered through the use ofinfrared) is that the alignment of a millgear set can shift over a period of timeas the mill progresses from a stoppedcondition to. its steady-state operatingconditions, This transient type shift wasencountered in hot air type dry processmill's.

An example of the temperature gra-dients of such a mill is given in Fig, 101,Here the gradient of the mil] pinionshifted from -21°F to +18°F over aperiod of approximately twenty hours.This represents a 30°F shift in gradientwhich, for that particular mill, corres-ponded to a .009" change in .alignmentover the pinion bearing span. ]t is sus-pected that this shift was the result ofthermal growth of the mill as it came upto normal operating temperatures,

A wet process taconite grinding millis also included in. Fig. 10 for com-parison. For that mill the steady stateoperating gradient was reached withinapproximately one-hall hour with no.evidence of any alignment shift.

At ally rate, to be 'certain steady-stateoperating temperatures have beenreached, it is recommended that the millbe operated for approximately twentyhours prior to raking "Operating-Tern-peratures",

Lubricant films"Stop-Action" photography, besides

recording pinion tooth surface condi-tions, describes the operating lubricantfilms on the pinion tooth. falk experienceindicates that these films can vary signifi-cantly depending upon 'the type of milland the operating conditions. Thesevisual differences inlube film promptedexploratory tests regarding the possibleinfluences of lubricant type. viscosity andoperating temperature on the appearanceof the film ..

Lub.ricant TypeThe lubricants. investigated were

asphatic base •.residual type compoundstypically used for ring gearing, Theirviscosities ranged from 4,750 SSU to17..200 SSU at 2100P undiluted. Theywere produced by various manufac-turers. None of the lubricants had a largepercentage of solid lubricant additives.

Fig. B - Geu Performance History

SA Initial Photo

8B 2. Months Later

8C B Months Later

80 1 Year Later

Fig. 9-Camera and Fld£h Positions

+20It.0

FZUJ +10a~..,UJ 0a:::l

iUJ -10IL.:EUJt-ow -20.0:«.a:...~ -30

5 5 10

liME AFlIER STARliNG-HOURS

fig. 10- Transient Shift in Alignment

Septemtler IOctober 1985 41

Since differences in the lubricant filmson photos appeared as changes in dark-ness and color, it was important to deter-mine whether the color of the lubricantvaried with film thickness or differed be-tween lubricants of different manufac-turers, A laboratory test was performed.It involved placing a piece of Vz' plateglass over a ground steel bar, which hadbeen coated with lubricant and had a.002' step in the bar (Fig. 11). This stepproduced a space between the bar andthe plate glass that increased from O· to

.002' over the 3· length of the step andwhich was filled with lubricant. The rela-tion between lubricant film thickness andits color could then be observed throughthe glass and photographed.

Inspections of the glass and the plateindicated that both were Hat to withinless than ..OOC}}• over the area of contact.Before applying the lubricant to the steelplate. the glass, the lubricant and theplate were heated to approximately190°F to drive any diluent from the lubri-cant and achieve a uniform temperature.

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42 Gear Technology

The photography lighting was iden-tical for each lubricant photo. It wasalso very similar to the lighting usedfor photographing operating millpinions.

The results of this testing showthat the color distribution with filmthickness is very similar for each lubri-cant. Additional tests in wh.ich thelubricants were allowed to cool toroom temperature (70°f) indicatedthat the color of the lubricant did notchange with temperature.

These exploratory tests suggest thatresidual type lubricants are basicallythe same color and that lubricant filmcolor might be used to estimate orcompare lube film thicknesses.

Lubrican.t ViscosityThe glass plate test also indicated

that changing viscosity within the4,750-17,200 SSU range did notsignificantly influence the relationshipbetween color and film thickness ofthe lubricants tested, This observationwas used in the evaluation of a fieldtest where these same lubricants hadbeen individually applied to the samemill pinion. Adequate time had beenallowed for each lubricant to establishits own film, The resultant films werevery similar. The pinion operatingtemperatures, which were mon:itoredwith infrared and surfacecontadtemperature instruments, remainedessentially constant (l84!°F to 190oF)for all lubricants tested. The indica-tion of this test was that the changein non-diluated viscosity within the4,750 to 17,200 SSU range, which istypical for residual compounds, didnot significantly influence the lubri-cant film appearance.

Operating TemperatureFrom the previous testing, the

variance in lubricant film, betweendifferent pinions, does not appear tobe significantly related to the specifiedviscosity or manufacturer of the lubri-cant for the viscosities and lubricanttypes tested, The third parameter in-vestigated,temperature, was found tohave significant influence. This wasobserved in a field test where thelubricant film was monitored from thetime the mill started, at ambienttemperature (80oF), until it reached its

E~~I h- ,---I

Fig. ll-ll.lbe film Test Setup

Fig. 12 -lubricant Film Color Change· After Start-Up (Start 70°F Final 179°F)

128 2 Hr. After SUrt

12C 6 Hr. Aftfr Start

normal, operating temperature of 179°F.Fig. 12 describes the change in. film. atvarious 'times after startup and showsthat the lubricant film becomes lighter incolor as the temperature increases. Fromthe glass plate Itest, this would indicatethat the film thickness is also decreasing.

The relationship between lubricantfilm and operating temperature is furtherillustrated in Fig. 13. Here, four mill pin-ions from different applications, usingdifferent lubricants, are shown aJongwith their corresponding operating tem-peratures, Again, the color of the lubri-cant film becomes lighter, indicating ill

thinner film as the operating temperarareincreases. This agrees with the results inFig. 12. In genera], similar results werefound on other gearing where bothphotos and temperatures were obtained.

when taking necessary corrective actiondu_ring ,the life of the gearing.

Reference1. ANTOSIEWICZ, M.. "The Use of MilJ

Gear Operating Temperatures for Align-ment Evaluation: IEEECem nllndustry21s1 Technical Conferenc, TarponSprin,gs. Horida M_y 19"79.

FIB. 13 - Lub.ricanl Fil'm '1'5. blbrkant andTem.pvalure·

13A Whitmore Moo. 147 F.

CONCLUSIONThis paper has presented two new

techniques for aligning and maintaininglarge ring gears. The techniques are par-'titularly beneficial because they can beutilized while the gearing is operatingand, therefore, do. not interfere with pro-duction. The unique advantage of theNOperating- Temperatures" technique isthat it indicates relative load Lntensityacross the faoe of the gearing and not justcontact. The "Stop-Action" photo cap-tures the 'tooth surface conditionandlubricant mm on the teeth of an oper-ating gear set. This is accomplished withreadily available, simple to use andrelatively inexpensive photographyequipment. The photos provide a far bet-ter history 'than memory, notes orsketches from which to make mainten-ance decisions.

Both these techniques are recommend-ed for use by engineering and mainten-ance personnel for evaluating gearingcondition and performance, They arealso recommended for consideration

lID 24 Hr. After Start

(Appendix continued on pag.e '1~8)

138 Texaco Crater SX 165 F.

September/October 1985 43

HOB LENGTH EFFECTS .(continued from p.age 19)

F(Y) = 4: X KA X yJ + 3 X K8 X y2 + 2 XKC X Y + KDFor first approximation Y can be set equal to PD 12

so Y = PD/2

This method allowsfast and precise calcuJIation with a smallnumber of iterations.

Having Y, one can obtain X and Xo, by substitution.

Consulting Fig. 7, since QP=Xo, distance OP=Xo X tantq)and roughing zone: Lr=OP - 19/2

3. ENGAGEMENT ZONEAs mentioned above, the engagement zone is the sum of

roughing and generating zones.

Le = Lg + Lr

The author gratefully Ilcknowledges the t:lS5istance of Claude Lutz. AmeriCQllPflluter Ltd., for technical consulting; Eduard P. Driscoll. Driscoll SoftwareCo .. for computer analysis; and Frank C. llherek, Dresser lnd., fOT articledevelopment.Editors; Note; Special thanks to Dennis Gimperl. American Pfauter Ltd .. forhis technical editing assistance.

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TECHNIQUES FOR ALIGNING & MAINT AINlNG(continued from page 43)

APPENDIX AINSTRUMENTATION SPECIFICATIONS

Surface Contact PyrometerA digital type pyrometer having an accuracy of ±3°F and

a. response time of approximately Iive seconds or less was

Fig. A-l- Test Set-UpLens Type Infrared Radiation Thermometer

48 Gear Technology

used. The contact probe was surrounded by ceramic type sub-stance to shield it from the influence of ambient temperatures,

INFRARED

InstrumentationThere are basically two styles of infrared instruments. One

focuses the infrared through a lens and the other reflects itfrom a mirror. The lens type can be aimed more preciselymaking it superior from an accuracy viewpoint. Unfortun-ately, lens type instruments are the least portable.

The specifications of each of these types of infrared in-struments can valy widely, The following key specificationsare recommended for this application:

TemperatureSpectral ResponseField of ViewSpot Size (max.)

soap to 300°F8-14 microns2° or less}l/z· at 40'distance

Emissivity Range .6-1.0 (min. range)

A digital readout ora. meter readout with a meter holdfeature (not peak) is recommended. Some mirror type in-strurnentsare available with laser optics to aid in aiming theinstrument. This option makes them equivalent to the lens'type.

SetupFig. A-I illustrates the setup of the lens type infrared radia-

tion thermometer. A fluorescent light is an aid for aimingthe detector at selected measurement points. It has been deter-mined that the heat emitted from this light does not influencethe measurements. It is very important that the light be heldhorizontally to obtain a horizontal reflection from the pitchline of the mesh. The tripod is recommended.

Fig. A-2 illustrates the setup for a mirror type instrument.In this case, the Huorescent light and tripod are also recom-mended for instruments without laser sighting optics.

.Fig.. A-2 - Test Set-UpMirror Type Infrared Instrument

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