WHY USE BEARINGS? Bearings are mechanical components that support, locate, or guide a moving part in equipment. The moving part may be a rotor in the case of rotary equipment or a cross head-piston rod piston assembly in the case of reciprocating equipment. The primary function is to act as intermediate component between the moving and stationary parts and reduce friction.

All bearings serve the primary function of keeping a rotating part from contacting another part which may be either rotating at a different speed or stationary. A bearing must provide stiffness to keep the rotor in position, and it must do so while minimizing friction. Fluid-film bearings do this by providing a thin layer of lubricating fluid between the rotor and journal. Rolling element bearings do this by using a set of balls or rollers that keep rotor and stator separated.

CLASSIFICATION OF BEARING {A} BASED ON THE LOAD THE BEARING SUPPORTS :RADIAL BEARING: Load acts perpendicular to the centerline of the shaft.THRUST BEARING: Load acts along the centerline of the shaft.LINEAR BEARING: To support the loads in a reciprocating part{B} BASED ON LUBRICATION PRINCIPLES:ANTIFRICTION BEARINGPLAIN BEARING

ANTIFRICTION BEARINGS CLASSIFICATIONRADIAL TYPE BALL Deep grooveDouble row deep grooveSelf aligningAngular contactCYLINDRICAL ROLLERSPHERICAL ROLLERTAPER ROLLERTHRUST BallCylindrical RollerSpherical Roller

BASIC COMPONENTS OF ROLLING BEARINGS

PARTS OF AN ANTIFRICTION BEARINGINNER RACEOUTER RACEROLLING ELEMENT (SPHERICAL BALL, CYLINDRICAL ROLLER, ETC)CAGE OR SEPARATORSHIELD

THE MAIN FUNCTIONS OF THE CAGE ARE:Keeps the rolling elements apart to prevent mutual contact.Keeps the rolling elements evenly spaced to ensure a more even load distribution.Guides the rolling elements in the unload bearing zone.Prevents the rolling elements from falling out of separable and slew able bearings, thereby facilitating bearing mounting.

THE MAIN FUNCTIONS OF SHIELD:It is fixed in the outer race and has close running clearance with the inner race. It protects the bearing from contaminating particles by preventing its entry into the bearing. The shield may be provided in one or both sides of the bearing.

DEEP GROOVE BALL BEARING Can take large radial loads and because of deep groove can take some thrust load also. Suitable for high speeds applicationThere are two rows of balls and hence the radial and thrust load capacities are almost doubled.DOUBLE ROW DEEP GROOVE BALL BEARING

SELF-ALIGNING BALL BEARING The inner side of the outer race has a spherical face. Because of this bearing can take misalignment with the shaft up to 2o ANGULAR CONTACT BEARING They can take radial loads and large thrust loads in one direction

CYLINDRICAL ROLLER BEARING Since the contact between cylindrical rollers and races is line contact , they have greater radial load capacity SPHERICAL ROLLER BEARING These are generally made as double row. The inside surface of the outer race is spherical and also the roller are spherical. Can take misalignment of the bearing with the shaft. Have greater radial load capacity as compared with a self-aligning ball bearing

NEEDLE BEARING The cylindrical rollers are large in length and smaller in diameter. Advantage of greatest load carrying capacity with the additional advantage of less radial space.TAPERED ROLLER The rolling elements have the shape of truncated cones or tapered rollers. The outer the inner race tapered rollers, cage assembly are separate. They can take large thrust loads and radial loads.

THRUST BALL BEARING Thrust bearing can take thrust load only. The races are top and bottom races instead of inner and outer race. The top race, bottom race and rolling elements held in cage are separate

BEARING DESIGNATION The first digit (or letter) designates the bearing type,The second digit represents the width (or height) series. The third digit the diameter series The two last digits indicate the bore diameter (obtained by multiplying the two last digits by five)

BEARING TYPE DESIGNATION0Angular contact bearing, double row1Self-aligning ball bearing2Spherical roller bearing and spherical roller thrust bearings3Taper roller bearing4Deep groove ball bearing, double row5Thrust ball bearing6Deep groove ball bearing, single row7Angular contact ball bearing, single row8Cylindrical roller thrust bearing

SUPPLEMENTARY DESIGNATION Prefixes serve to identify designs (variants) which differ in some way from the original design or which differ from the design, which is the current production standard.PREFIXES:GSHousing washer of a cylindrical roller thrust bearingK Roller and cage assembly of a cylindrical roller thrust bearingK-Inner ring with roller and cage assembly (cone) or outer ring(cup) of a taper roller bearing belonging to an AFBMA standard series and generally having inch dimensionLRemovable inner or outer ring of a separable bearing e.g. L 30207-outer ring of taper roller bearing 30207RSeparable bearing without removable inner or outer ringWSShaft washer of a cylindrical roller thrust bearing

SUPPLEMENTARY DESIGNATION SUFFIXES :-Z Shield fitted at one side of bearing.-2Z Shield fitted at both side of bearing.-ZN Z shield at one side of bearing and snap ring groove at the other-RS Rubber seal of synthetic rubber at one side of bearing-LS Land riding seal (rubber seal) at one side of the bearing-N Snap ring groove in outside cylindrical surface of outer ringCAGE:JPressed cage of sheet metalYPressed cage of sheet brassFMachined cage of steel or special cast ironMMachined cage of brassPMoulded cage of glass fiber reinforced polyamide 6.6TNMolded cage of plastic

FACTORS INFLUENCE THE OPERATING PERFORMANCE OF THE BEARING LOAD - MAGNITUDE AND DIRECTION.SHAFT SPEED.BEARING SIZE.OPERATING ENVIRONMENT: TEMPERATURE AND CONTAMINATION.LUBRICATION: TYPE AND METHOD.SEALS: TYPE AND CONDITION.SHAFT ALIGNMENT.MOUNTING AND DISMOUNTING TECHNIQUE.SHAFT AND HOUSING FITS

CAUSES OF VIBRATION /NOISE IN THE BEARING DAMAGED ROLLING ELEMENT / RACEWAY.BROKEN CAGE.PRELOADING.LUBRICATION STARVATION/ FAILURE.EXCESSIVE CLEARANCE.OUT OF ROUNDNESS OF SHAFT /HOUSING.EXCESSIVE DRIVE UP/ INTERFERENCE FIT.LOOSE FIT ON THE SHAFT.LACK OF SQUARENESS OF THE SHOULDER.PRESENCE OF ABRASIVE PARTICLES.UNBALANCE.MISALIGNMENT.EXTERNAL VIBRATION.SOFT FOOTGEAR MESH PROBLEM

CAUSES OF TEMPERATURE RISE IN THE BEARING DAMAGED ROLLING ELEMENT /RACEWAY.BROKEN CAGE.PRELOADING.LUBRICATION STARVATION/FAILURE.EXCESSIVE LUBRICANT.EXCESSIVE DRIVE UP/ INTERFERANCE FIT. LUBRICANT CONTAMINATED WITH WATER. LOOSE FIT ON THE SHAFT. OUT OF TOLERANCE OF SHAFT / HOUSING.PRESENCE OF ABRASIVE PARTICLES.UNBALANCE.MISALIGNMENT.BEARING DOESNT HAVE MINIMUM LOAD.SPEED TOO HIGH.LOAD TOO HIGH.

STEPS TO BE TAKEN TO INCREASE THE BEARING LIFE DON'TS:Use emery paper on bearing seating on the shafts.Damage the shaft while dismounting a bearing.Use mechanical force on rolling elements( balls, rollers) while mounting/dismounting a bearing.Use lubricant for replenishment without knowing the grade of lube already in use.Over lubricate.Lubricate frequently.Use dry felt strips for sealing.Use old seal when the bearing is being replaced.Deviate from O.E.M. specification without assessment of effect.Use dirty oil for heating bearings.Keep bearings at the bottom of the bath while heating.Use induction heaters which doesn't have demagnetization cycle..

STEPS TO BE TAKEN TO INCREASE THE BEARING LIFE DO'SIntroduce condition monitoring and built up asset history.Carry out seal audit and rectify faulty sealing arrangements.Carry out lubrication audit and rectify faulty lubrication practices.Introduce alignment and balancing program.Introduce root cause failure analysis and corrective action practice.Introduce proper mounting and dismounting tools and practices.Train maintenance staff.Store and handle bearing properly.Keep lubricant containers closed and protected from contamination. Bearing maintenance room should be clean and protected from easy ingress of dirt.