A PRESENTATION BY WG CDR ARVIND KUMAR. BEARINGS, FAILURES CAUSES & REMEDIES

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<ul><li>Slide 1</li></ul> <p>A PRESENTATION BY WG CDR ARVIND KUMAR Slide 2 BEARINGS, FAILURES CAUSES &amp; REMEDIES Slide 3 CONCEPT CONSTRUCTION BEARING MATERIALS TYPES OF LOADS &amp; BEARINGS BEARING CLEARANCES WHY BEARING FAILS! FAILURES, CAUSES &amp; REMEDIES :FEW EXAMPLES PATH PATTERN INTERPRETATION OTHER IMPORTANT POINTS TV-2 STATISTICS PRACTICAL DEMONSTRATION Slide 4 CONCEPT OF ROLLING BEARING Slide 5 Things roll better than they slide. Hence the invention of WHEEL. Rolling friction is far lesser (&gt;100 times less) than sliding friction. Microscopic contacts get peeled off and not sheared off in rolling. Slide 6 Slide 7 Cage/ Retainer Inner ring / race Rolling element Outer ring / race Side faces Outer ring raceway Shoulder Inner ring raceway Shoulder 7 ROLLING BEARING CONSTRUCTION Slide 8 7 BEARING DIA Outside Diameter Bore Slide 9 BEARING CONSTRUCTION-2 SealRolling ElementsInner Ring Outer RingCageSeal Slide 10 BEARING CONSTRUCTION-3 Outer Ring Cage Inner Ring Side faces W33 Lubrication Groove and Hole Rolling Element Guide Ring Inner Ring Raceway Slide 11 VARIOUS ROLLING ELEMENTS Spherical roller (asymmetrical) Taper roller Spherical roller (symmetrical) Needle roller Cylindrical roller Ball Slide 12 POINT / LINE CONTACT Slide 13 Slide 14 PROPERTIES : BEARING MATERIALS High wear resistance High rolling fatigue strength Non-metallic inclusions like O, S etc. increase fatigue cracking High dimensional stability Heat treatable to high hardness in depth High corrosion resistance High wettability with oil Low coefficient of semi-dry friction Good heat conductivity Good antiseize properties Slide 15 MATERIALS-SKF BEARINGS BEARING RINGS AND ROLLING ELEMENTS THROUGH-HARDENING STEELS CARBON CHROMIUM STEEL CONTAINING APPROXIMATELY 1 % CARBON AND 1,5 % CHROMIUM CASE-HARDENING STEELS CHROMIUM-NICKEL ALLOYED STEEL AND MANGANESE-CHROMIUM ALLOYED STEEL CONTAINING APPROXIMATELY 0,15 % CARBON Slide 16 SKF BEARING MATERIALS -2 ~SAE 52100 C-Cr Bearing steel ( ISO 683 -17:1999) Ceramics like Si 3 N 4 for ultra high speed applications Stainless steels like X65Cr14 (ISO 683-17:1999) Slide 17 BEARING MATERIALS -3 Highly alloyed steels like 80MoCrV42-16 for temperature &gt; 250C (SKF) Case Hardening Steel for shock loads DMRL analysis for Russian bearing (6-7000108B, Central Drive B.B on Ist support assy of TV-2 engine of Mi-8 heptr) C~1.0% Cr~1.8% Si~0.23% Mn~0.33% steel nearly equivalent to AISI-52100 Original Russian material is Sh Kh 15 Slide 18 SPECIAL FEATURES Hard Surfaces HRC 58-65 for C-Cr bearing steel (SKF) DMRL analysis of Russian Bearing - HV/5Kg : 930 (HRC : 68) Perfectly round and incredibly smooth Very high surface finish : CLA ~ 0.5 microns Addition of Si to improve heat resistance dimensional stability) at 150-200C Slide 19 Radial loads Axial Loads Combined loads Slide 20 AXIAL / THRUST LOADS BAR STOOL BEARINGS (Mans wt. causes thrust load) Thrust load Bearings Slide 21 RADIAL LOADS Motors &amp; Pulley Shaft Support Bearings Radial load MotorTension Slide 22 COMBINED LOADS Car Wheel Bearing Slide 23 CYLINDRICAL ROLLER BRG : Radial load only (Heavy) BALL BRG : Both axial &amp; radial TAPERED ROLLER BRG : Radial load &amp; Axial load in one direction also Axial load is also called as Thrust load Slide 24 RADIAL LOAD Cylindrical Roller Bearing Slide 25 Deep groove B.B Angular contact B.B Self-aligning B.B Ball Bearings Radial loadAxial load SpeedAccommodates carrying capacity carrying capacity capabilitymisalignment Slide 26 Radial Load Axial Load (one direction) Tapered Roller Bearing Slide 27 Radial Load Thrust Thrust Double Tapered Roller Bearing Radial Load Thrust Thrust Double Tapered Roller Bearing Slide 28 Slide 29 360 ~150 LOAD ZONE Slide 30 Radial clearance / play Axial clearance / play BEARING CLEARANCES Slide 31 C1 - less than C2 clearance C2 - less than normal clearance CN - normal clearance C3 - greater than normal clearance C4 - greater than C3 clearance C5 - greater than C4 clearance Russian System ? Example: A 6210 /C3 ball bearing has 18 - 36 m (microns) or 0.0007 - 0.0014 radial internal clearance CLEARANCE DESIGNATIONS Slide 32 AXIAL INTERNAL CLEARANCE Example: A 5210 / C3 ball bearing has 33 - 54 m or 0.0013 0.0021 axial internal clearance 25-126114P ball bearing used in TV-3 aeroengine 2nd Support should have 140-220 m axial internal clearance Slide 33 EFFECT OF TEMPERATURE ON CLEARANCE COLD (by 5-10C) WARM Reduced radial clearance Expansion Compression Slide 34 EFFECT OF FIT ON CLEARANCE INTERFERENCE FIT between shaft and bearing (inner race) reduces radial clearance by approx 80% of the fit. Because the inner ring expands and the outer ring contracts. Slide 35 EFFECT OF LOOSE FIT N = 3 000 10 hours/day 30 days = 18 000 min Sliding motion =0,013 x x 3 000 x 18 000 = 2,2 x 10 6 mm = 2,2 km (1.4 miles) creep Slide 36 LOAD DISTRIBUTION &amp; CLEARANCE Less Clearance More Clearance Pressure between rolling element and races can reach 4 lakhs PSI Slide 37 EXCESSIVE CLEARANCE Loading area reduces &amp; stress increases Bearing rigidity reduces Alignment of rolling elements decreases Vibration increases at high speeds Noise increases Running and locating accuracy reduces Slide 38 PRELOAD Small amount of loading before running of brg Causes negative clearance Elastic deformation &amp; compressive stress at contact area Bearing rigidity improves Vibration at high speeds reduces Noise reduces Alignment of rolling elements improves (Thrust brgs) Running and locating accuracy improves Slide 39 EFFECT OF CLEARANCE ON BEARING LIFE Excessive preload causes high stress and heat generation Life PreloadClearance Slide 40 BEARING LIFE Repeated compressive stresses (rolling fatigue) cause flaking of material of raceways and rolling elements and hence failure. Basic Rating Life L 10 (90% reliability) of the bearing is the total number of revolutions in millions which 90% of the bearings out of the lot reach before or at which the first signs of flaking occur under identical operating conditions. Slide 41 BEARING LIFE-2 L 10 = (C / P) n C = Design Load {Basic dynamic rating load (constant radial or axial load when brg is rotating) in N that will give bearing life of 10 6 revs in accordance with ISO 281:1990} P = Actual equivalent dynamic load in N n = 3 for ball bearings 3.33 for roller bearings Slide 42420 mm) 3B. MEDIUM SIZE BEARINGS 3C. SMALL BEARINGS * OLDEST B"&gt; 1. FIRST IN, FIRST OUT 2. DO NOT PILE UP TOO HIGH 3A. STOCK LARGE BEARINGS FLAT (O.D. &gt; 420 mm) 3B. MEDIUM SIZE BEARINGS 3C. SMALL BEARINGS * OLDEST BEARINGS ALWAYS IN FRONT AND ON THE TOP OF THE PILE * IT DOES DAMAGE THE PACKING * AT THE BOTTOM OF THE RACKS * STOCK FLAT (not vertical) * STOCK UNOPENED (individually packed in box) * NUMBER READABLE (up front) * NUMBER (designation) UP FRONT) * IN DRAWERS OR BOXES (keep away from dust) * DESIGNATION ON DRAWER (box) STORAGE IN RACKS STORAGE AND REPACKING Slide 85 REMARK : * BEARINGS ARE CLEAN AND ARE PROTECTED WITH A RUST INHIBITIVE OIL. * BEARINGS ARE WRAPPED IN A SPECIAL PAPER OR PLASTIC SHEETING FOR PROTECTION. * BEARINGS ARE PACKED IN CARDBOARD BOXES FOR PROTECTION * LARGE SIZE BEARINGS ARE INDIVIDUALLY PACKED IN WOODEN BOXES FOR PROTECTION. 3 GOOD REASONS TO KEEP BEARINGS IN THE ORIGINAL PACKING : STOCKING RECOMMENDATIONS STORAGE AND REPACKING Slide 86 * WHITE SPIRIT * CLEAN AREA * LET DRY 1. WASH 2. INHIBITING OIL PROTECTION * 40 % QUAKER 5815 BASE AND 60 % WHITE SPIRIT * DIP AND ROTATE * DRY 7 HOURS * CLEAN AREA 3. PACK * WRAP IN POLYETHYLENE COATED "VPI" PAPER * PACK IN (CARTON) BOXES 4. IDENTITY * INDICATE FULL BEARING NUMBER * INDICATE BRAND !! RENEWING ANTI-RUST (AND PACKING) STORAGE AND REPACKING Slide 87 Slide 88 Slide 89 Slide 90 </p>