The selection of conveyor drive

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SPECIFICATION DEVELOPMENT GET THE RIGHT CONVEYOR DRIVE SYSTEM FOR THE JOB By Ronld Fedder, Mrketing Mnger, Rexnord Industries, LLC The selection of conveyor drive components is comprehensive,

1 SPECIFICATION DEVELOPMENT GET THE RIGHT CONVEYOR DRIVE SYSTEM FOR THE JOB By Ronld Fedder, Mrketing Mnger, Rexnord Industries, LLC The selection of conveyor drive components is comprehensive, investigtive process involving input from multiple prties: fcility mngement, corporte personnel, consultnts nd equipment suppliers, to nme few. Culling the knowledge nd expertise of ll individuls involved should result in the proper selection of conveyor drive components tht prove durble, efficient nd cost-effective to help chieve fcility s long-term production gols. (Figure 1) But, during this involved selection process, re detils overlooked? Do elements conflict? Are ll prties on the sme pge? How cn it be ensured tht the pproprite conveyor drive equipment is selected nd instlled? Specifictions. It is the consistent communiction document between the fcility owner, consultnts nd suppliers (Figure 2) for proper equipment selection. Therefore, its development is prmount. Specifictions define wht is required of the complete conveyor system to provide n expected performnce level. Consultnt Owner Project Gols Figure 2 A tem pproch. Suppliers Figure 1 A durble, efficient nd cost-effective conveyor drive system will help fcility chieve its long-term production gols. The specifiction must be crfted to the project s unique needs, including site conditions, production expecttions, compny culture, service support nd the equipment s long-term vlue. If components re lower in cost nd of proven technology (Figure 3 Point A), simpler specifiction process, utilizing reputble brnds nd ctlog stndrd products, should result in the pproprite components, nd provide the lowest operting cost. But if components re of high Detil SPECIFICATION TYPE Brnd Low A $ VALUE Figure 3 Specifiction Type versus Equipment Vlue B High cost nd criticl importnce (Figure 3 Point B), more extensive specifiction is necessry. SPECIFICATION DEVELOPMENT Specifictions re drwn upon the cumultive experience of compny s stff or consulting engineering firm. Reviewing existing specifictions, benchmrking similr instlltions nd investigting component options with suppliers will result in the best possible specifiction for the ppliction t hnd. A specifiction s objective is to define the expected level of drive system performnce. This expecttion should be clerly identified in order to provide equipment suppliers with the proper direction for component recommendtions. To obtin equivlent proposls from potentil suppliers, the specifiction should be

Service Fctors Nture of Appliction Stndrd Criticl Conveyor Loding Less thn 10 hrs/dy Greter thn 10 hrs/dy Uniform 1.25 1.25 Hevy Duty 1.25 1.50 Severe 1.75 2.00 Uniform 1.50 1.50 Hevy Duty 1.50 1.75 Severe 2.

2 Service Fctors Nture of Appliction Stndrd Criticl Conveyor Loding Less thn 10 hrs/dy Greter thn 10 hrs/dy Uniform Hevy Duty Severe Uniform Hevy Duty Severe Figure 4 This chrt identifies typicl service fctors bsed on the nture of the ppliction, conveyor loding prmeters nd the conveyor s duty cycle. detiled, llowing miniml interprettion. Specifictions, though, should invite lterntives, providing mnufcturers the ltitude to offer designs tht re superior nd more totl cost-effective thn those specified. The generl specifiction defines the overll project requirements. Elements to detil include: project scope nd schedule; site loction/conditions; terminology definitions; system description; design stndrds; electricl/mechnicl interfces; pricing; brnd preferences; terms nd conditions; non-inclusions or items supplied by the buyer; qulity ssurnce/testing requirements; references; nd project nd bid submittl processes. GEAR DRIVE SPECIFICATIONS The ger drive is precision component tht relies on solid design, qulity components nd precise ssembly to chieve relible operting system. Proper ger drive ppliction requires selection bsed on mny operting prmeters, including input power, lod demnd, externl lods, duty cycle, environment, system ccessories nd fcility needs. Ger drive selection is then mde bsed on service fctor tht ccounts for the non-uniformity of torque by the driving nd driven mchines. For detiled specifictions, ger bending strength rting, ger pitting resistnce rting, bering L10/L50 life nd specific feture considertions must be considered. Typicl service fctors for most conveyors re 1.25 uniformly loded, 1.5 hevy-duty, nd 2.0 severe duty, ll with reduction of 0.25 for service less thn 10 hours per dy. (Figure 4) Specifictions tht need to be ger drive loction input (motor)/output (hed shft) rpm nd speed rnge (if vrible) motor, lod nd lift power, ccelertion/speed control method duty cycle, hours per dy, dys per yer service fctor rting stndrd for complete ger drive AGMA 6010E88 or ISO TR13593 (DIN 3990 pplies to gering only) uni-directionl or bi-directionl lods multiple drive lodshring, strting sequence sound levels (if pplicble) ccessories nd options The best determinnt of equipment supply is successful reltionship with supplier who fully understnds the needs of your compny, project nd fcilities. However, in order to compre equipment options on n equl bsis, common design nd selection criteri need to be estblished. A simple specifiction, quoting to specific AGMA (Americn Ger Mnufcturers Assocition) or ISO (Interntionl Stndrds Assocition) stndrd nd service fctor, will provide comprble bids, provided the suppliers re honest in their proposls. Simply stting rted to AGMA or ISO stndrds will not do! A specific stndrd number must be referenced to ensure n equl comprison. In some situtions, more comprehensive specifiction criteri will be necessry to ssure tht the equipment will meet the technicl requirements of the project. Specific specifiction criteri, s outlined in this rticle, will produce more rigorous comprison of conveyor drive components, ensuring ger drive is selected tht proves dependble in chieving plnned production gols. CONFIGURATION The configurtion (Figure 5) detils the required mounting nd generl physicl lyout for the conveyor drive instlltion. Spce limittions, structurl costs or mintennce needs my dictte the need for prticulr drive configurtion. Figure 5 Exmples of different drive configurtions Specifictions tht need to be prllel, right-ngle or concentric shfts foot or shft mounted ssembly hnd or ssembly, consider drive commonlity gols direct connected or belt/chin connected motor type (NEMA/IEC, foot or flnge mounted), frme size nd weight 2

3 HOUSING The ger drive s housing mteril nd rigidity re criticl to obtining high mesh ccurcy or full pitch line contct. The housing supports the gering nd, depending upon its specifiction, provides dditionl ppliction benefits. For exmple, fbricted/cst steel housing provides superior impct resistnce, while cst iron provides better noise reduction nd vibrtion dmpening. Specifictions tht need to be fbricted/cst steel or cst iron housing mteril sufficient housing rigidity tht is commensurte with ger qulity numbers to ssure proper contct under full lod housing split orienttion (horizontl/verticl) or esily serviceble construction blind drilled nd tpped fstener holes to eliminte the potentil for oil lekge ger/internl component inspection cpbilities drive/motor bses, mde from stress relieved fbricted steel with mchined mounting surfces, to ccept ll system components; bse should be designed to withstnd strting/stopping lods nd lod moments, nd feture motor nd ccessory djustment screws with shft mounted drives, specify torque rm tht properly nchors the drive nd permits free movement without binding stinless steel identifiction tgs mechniclly ttched to the housing GEARING Gering is the hert of the ger drive. It must be designed to work s system with the shfting, berings nd housing to provide high mesh ccurcy under dynmic loding conditions. Mny of tody s drive trins re computer-modeled to ensure ccurcy nd efficiency. For more comprehensive specifictions, service fctor on bending strength nd pitting resistnce should be included. A service fctor ccounts for the non-uniformity of torque by the driving nd driven mchines. Bending strength indictes the lod tooth cn crry without bending ftigue filure. (Figure 6) Pitting Bending Strength/Motor Power Rtio Nture of Appliction Less thn 10 hrs/dy Greter thn 10 hrs/dy Stndrd Figure 6 Bending strength is the lod tooth cn crry without bending ftigue filure. resistnce is the lod tooth cn crry without dmging the profile from surfce pitting. (Figure 7) Pitting Resistnce/Motor Power Rtio Nture of Appliction Less thn 10 hrs/dy Greter thn 10 hrs/dy Stndrd Criticl Figure 7 Pitting resistnce indictes the lod tooth cn crry without dmging the profile from surfce pitting. Ger qulity numbers should lso be provided in the bid for reference. A qulity number of AGMA is stndrd for modern cse crburized nd finished ground gers. To compre AGMA qulity numbers to DIN qulity numbers, subtrct the AGMA number from 17 to obtin n equivlent DIN qulity number. Specifictions tht need to be single helicl or spirl bevel ger types cse crburized nd finish ground ger design minimum ger clss of 10 AGMA (7 DIN) efficiency minimum of 99 percent per mesh helicl, 98.5 percent per mesh spirl bevel 200 percent momentry overlod cpcity bending strength nd pitting resistnce service fctors on detiled specifictions For criticl systems, typiclly 1,000 HP (750 kw) nd lrger, full detils for ech reduction stge nd component rting summries should be outlined. (Figure 8) SHAFTING Shfting is rted on its bility to ccommodte bending nd torsionl lods. Shft lods result from externl forces due to mislignment, belt drives, chin drives, flywheels, brkes or other ccessories. Depending upon customer preference, inch nd metric shft extensions re vilble from most mnufcturers. Specifictions tht need to be inch or metric design stndrd unit ssembly rrngement required extensions (solid shft, hollow bore dimeter, tpered bushing or shrink disk connection) specil requirements BEARINGS Anti-friction berings re typiclly chosen for most conveyor drive pplictions. Tpered, sphericl or stright roller berings re the common types used. To specify bering performnce, bering life expectncy mesurement, clled bering L10, is utilized. Bering L10 life represents the point t which 10 percent of group of identicl berings will experience spll of 0.01 squre inches. It is the life expectncy ssocited with 90 percent relibility. Most bering mnufcturers employ more detiled bering rting method tht considers ctul operting conditions, such s operting temperture, lubricnt type, nture of filtrtion or contmintion, bering mteril, 3

4 Rting Summry Dt Sheets Ech Reduction Shft Pinion Ger Rdil lod, t drive side bering (lb) At non-drive side bering (lb) Thrust (lb) Bering number, drive side Non-drive side Thrust Gering Trnsverse dimetricl pitch Helix ngle Operting pressure ngle Number of teeth Pitch dimeter Hrdness BHN Fce width AGMA qulity number AGMA Strength Coefficients Kv Ko J Km Ks Kl Kt Kr St AGMA Durbility Coefficients Cv Co I Cm Cs Cf Cp Cl Ch Ct Cr Sc AGMA ger set qulity number Ger set bending strength rting Ger set bending strength service fctor Ger set pitting resistnce rting (AGMA) Ger set pitting resistnce service fctor Ger Rting ( hp) Service fctor = Motor ( kw) Figure 8 This worksheet detils the informtion to be outlined for criticl systems 1,000 HP (750 kw) nd lrger. 4

5 geometry nd lod zone. A proper specifiction defines unity (1.0) bering rting life djustment fctors or uniform criteri for detiled nlysis by ll suppliers. (Figure 9) Bering L10 Recommendtions Nture of Appliction Less thn 10 hrs/dy Greter thn 10 hrs/dy Stndrd 10,000 20,000 Criticl 25,000 50,000 Figure 9 Bering L10 life helps specify the most pproprite bering life for prticulr ppliction. Specifying n excessively high L10 cn hve n dverse effect on bering performnce, resulting in bering lods so light tht the rollers skid, rther thn roll s intended. Bering filures re ssocited with contmintion, poor lubriction, overlod, excessive vibrtion nd improper bering lod zone or settings. A high L10 vlue does little to prevent these filures. Using the correct oil nd operting t lower tempertures by instlling dditionl cooling nd filtrtion cn economiclly extend bering life nd performnce. Specifictions tht need to be redily vilble commercil roller berings; sphericl, cylindricl or tpered roller type bering L10 life bsed on unity (1.0) fctors for temperture nd oil clenliness, or uniform criteris for detiled nlysis. SEALING Properly seled ger drives void repir expenditures nd fcility downtime. Any interfces where oil could lek out or contminnts could permete the ger drive must be seled. The use of selnts nd gskets re proven methods for seling structurl components. Criticl interfces to sel include housing joints, retiner/sel cge joints, brethers, piping nd shft sels. Most industril ger drives re equipped with rdil lip, lbyrinth or fce sels. The integrity of rdil lip sel system depends on the successful opertion of ll components: plunge ground shft ABRASIVE CONTAMINATION GREASE BARRIER DUAL-LIP SEALS KEEP THE OIL IN Figure 10 Viton lip sels offer superior resistnce to high tempertures nd chemicl ttck. This illustrtes lip sel with grese purge feture. journl, lip sel, lubricnt, nd sel housing bore. (Figure 10) Lip sels re usully Nitrile mteril nd they re lso vilble in premium Viton, offering superior resistnce to high temperture nd chemicl ttck. For lrger drive systems provisions should be mde to replce the sels without moving the mjor drive components. Lbyrinth nd bush sels re premium non-contct seling systems tht lst indefinitely. (Figure 11) A grese purgeble GREASE FITTING GREASE GREASE EXCLUSION SEAL DRAIN BACK PASSAGE OIL TO BEARING RADIAL BUSH SEAL AXIAL BUSH SEAL cvity or contminnt exclusion system is recommended for severe environments. OIL BEARING INSIDE REDUCER Figure 11 Lbyrinth nd bush sels lst indefinitely. Specifictions tht need to be brether filtrtion to 20 microns contct sels (Nitrile or Viton) with grese purged brrier sels optionl lbyrinth sels with contminnt exclusion system for lrger drives LUBRICATION Lubriction is crucil to long life nd relibility. Viscosity is the single most importnt property of lubricting oils. For ger drive to function properly, oil viscosity must be kept within certin limits. An oil should be selected with pour point of 10º F (5º C) below the minimum system strting temperture, with mximum viscosity of 15,000 cst (70,000 SUS). If drive is equipped with n oil pump, the mximum viscosity should not exceed 1,725 cst (8,000 SUS). Minimum viscosity should not be less thn 33 cst (155 SUS) t mximum operting temperture. The oil cnnot be so thick tht it will not flow nd yet not too thin tht the ger teeth re not protected by lubricnt film. The ger drive mnufcturer should specify lubriction method nd lubricnt pproprite for site conditions. Depending upon the drive size nd cooling requirements, lubriction cn either be dip/splsh nd grvity fed or pressure fed. Specifictions tht need to be drin vlve for oil chnges oil dipstick or sight guge to check oil level nd qulity dip lubriction with continuous flow or pressure lubriction for lrger systems dul micron filters for pressure lubed systems 5

6 COOLING Conveyor drive cooling methods include nturl cooling, shft fn(s), electric fn(s) nd het exchnger(s). (Figure 12) SUMP TEMPERATURE C F Nturl Shft Fn Electric Fn Cooling Tubes HP ,000 KW Figure 12 Drive system size nd mbient conditions influence the pproprite cooling method. With tody s compct drives, nturl cooling is prcticl only with the lower power rnge of conveyor drives. Not specifying uxiliry cooling results in substntilly oversized drive or the use of through hrdened gering. Shft nd electric fns offer simple nd effective mens of cooling for mny requirements. For very lrge ger drives, pump nd ir-to-oil het exchnger, combined with n oil filtrtion system, provides qulity cooling system. If motor or pump is employed, monitoring is strongly recommended to provide wrning nd shutdown prior to ctstrophic filure. Therml rting, the mximum power ger drive cn continuously trnsmit without exceeding specified mximum oil temperture, is n importnt considertion when selecting cooling method. An cceptble men oil temperture is 160º F (71º C). Operting tempertures bove 200º F (93º C) will significntly reduce lubricnt, contct sel nd drive life. Site conditions, such s ltitude nd mbient ir temperture, re lso importnt to the therml rting clcultion. Specifictions tht need to be site elevtion nd mbient conditions (high/low tempertures) minimum strt up temperture verge ger drive operting temperture of 160º F (71º C) CONNECTIONS Ger drive connections for conveyors re generlly shft couplings, v-belt drives nd/or hollow shft locking devices used for shft mounting. The four primry types of couplings re grid, ger, disc nd elstomer. (Figure 13) Grid or elstomer types re pproprite selections for Figure 13 The four primry types of couplings re (top left) disc, elstomer, grid nd ger. high-speed connections, while grid couplings re generlly the best ll-round selection for low-speed connections. V-belt nd synchronous belt drives re used extensively on prllel-shft mounted drives in powers up to 200 HP (150 kw) or for spce-restricted instlltions. Shft mounted connections (Figure 14) include flnged low-speed couplings, hollow low-speed shfts TORQUE ARM VIEW OF LOW SPEED SHAFT RIGID COUPLING PURCH SHAFT Figure 14 A shft mounted right ngle drive. with shrink discs or tpered bushings. For lrge shft mounted conveyor drives, flnged low-speed coupling is preferred, due to its ese of mounting nd bility to use stndrd ger drives. Specifictions tht need to be coupling type (grid, ger, elstomer, disc), lubricted or non-lubricted, torsionlly rigid or torsionlly soft shft dimeters/keys service fctor equl to ger drive clernce with set screw(s) or interference coupling hub fits shft coupling fce key required for high-speed bckstop-equipped pplictions hub puller holes or hydrulic removl required on lrger couplings gurding tht is complint with OSHA (Stndrd 29CFR) Mechnicl Power Trnsmission Apprtus nd in conformnce with ANSI nd ASME B Sfety Stndrds for Conveyors nd Relted Equipment nd B Sfety Stndrds for Mechnicl Power Trnsmission Apprtus 6

7 PAINT For most conveyor requirements, the mnufcturer s stndrd pint provides dequte protection ginst corrosion. If ger drive will be exposed to corrosive environment nd/or chemicl ttck, premium pint should be specified. brkes (holding, dynmic) flywheels (shft mounted, jck shft mounted) inching drives (mnul, utomtic) heters (immersion, recirculting) monitoring devices (temperture, vibrtion, speed, pressure/flow) qulifictions (ISO 9001, etc.) references After specifiction evlution, contrct is wrded. The chosen supplier must dhere to the negotited contrct. Once the equipment is instlled nd commissioned, ongoing monitoring of opertionl performnce should be mde to determine if the owners requirements were successfully met. CONCLUSION A specifiction is the process of ccumulting nd pplying ctul experience to develop guidelines nd requirements for new equipment procurement. The ger drive specifiction considertions for conveyors outlined bove will guide fcility personnel, consultnts nd equipment suppliers in the proper nd dependble compiltion of conveyor drive system components to meet project s productivity requirements nd gols. Figure 15 Drives exposed to direct sunlight will run cooler with white reflective pint.r (Figure 15) Specifictions tht need to be type of pint finish: one cot phenolic lkyd primer with finish cot lkyd enmel (stndrd pint ) or two cot epoxy pint with brsive blst for corrosive environments color, if required, to mtch uniform color or to reflect direct sunlight (white) if stndrd pint will be top-coted t the job site, check for comptibility ACCESSORIES AND OPTIONS In ddition to the ger drive ssembly, there re ccessories nd options tht cn be integrted to dd functionlity nd increse performnce. They include: soft strt/controls (fluid, electronic, vrible) bckstops (internl, externl, low speed) REVIEWING SPECIFICATION PROPOSALS After the equipment proposls hve been received, thorough review of costs, conformnce, lterntives nd suppliers must be completed. It is recommended tht the proposl be reviewed in detil with those suppliers under serious considertion. Informtion tht is necessry during this review process includes: pricing/initil costs dt sheets operting costs wrrnties mnufcturer s product specifictions testing (no lod, full lod), inspection (ssembly, test, commissioning) nd verifiction (documenttion) commonlity/spres costs service informtion nd support network vilbility (locl representtion, fctory support, regionl inventory, Internet) References Errichello, R. 1987, How to buy gerbox, Gertech, June. Mrtin, J. 1993, Conveyor system specifiction development for surfce mining, Mrtin Consultnts, Inc., Februry. Fluor Dniel, Project specifictions, vrious. Bechtel, Project specifictions, vrious. CEMA, 1994, Belt conveyors for bulk mterils, 3rd edition. Flk, 1997, Conveyor drive technology seminr, My. Form , August 2007

TECHNICAL INSIGHT INTERNAL CLEARANCE - TYPES AND NORMS

TECHNICAL INSIGHT INTERNAL CLEARANCE - TYPES AND NORMS TECHNICAL INSIGHT PRODUCT AND APPLICATION ENGINEERING INFORMATION A PUBLICATION OF NSK AMERICAS INTERNAL CLEARANCE - TYPES AND NORMS Internl clernce is the distnce which the two rings of non-instlled bering