bearing power point

LONG PRODUCT GROUP PRESENTS

A KNOWLEDGE PAPER ON ANTIFRICTION BEARINGS

WHY A BEARING ?

It bears load during transmission of power through

shaft and housing.

It locates different parts accurately in position with respect to each other during operation.

CLASSIFICATION OF BEARINGS

THRUSTRADIAL

ROLLING TYPESLIDING TYPE

ROLLER BEARINGBALL BEARING

Rolling contact bearings

The rolling bearings operate on the basis of rolling friction.

Rolling bearings consist of the following main components

--- Inner ring--- Outer ring--- cage--- Rolling element

If rolling element is ball then the bearing is called---BALL BEARING and if it is roller then it is called ROLLER BEARING.

LET’S HAVE A LOOK ON FEW

ANTIFRICTION BEARINGS

Basic Designation of Antifriction BearingsBasic Designation of Antifriction Bearings

Normally standard bearings are Normally standard bearings are designated by five figuresdesignated by five figures

TYPE WIDTH O.D.

Last two digits x 5 = I.D.

I. D. CALCULATIONI. D. CALCULATION

Some exceptional cases

1. If last two digits are then I.D. (m m)

0 0 1 0

0 1 1 2

0 2 1 5

0 3 1 7

From 04 to 99 if multiplied by 5 gives I.D.

I. D. CALCULATIONI. D. CALCULATION 2. If I. D. < 10 mm or > 500 mm then it is directly given as follows : 618/8 I. D.= 8 mm 511/530 I. D. = 530 mm 3. Suppose : Bearing bore is like 22, 28, or 32mm then it is also mentioned in designation as under: 322/28 here d = 28mm 4. A nonstandard bore diameter is always expressed in millimetres to a maximum of three decimal places. e.g. 6202/15.875 (d = 15.875 mm) 5. Some special Bearings are designated by their drawing numbers. e.g. R315642 L315642

ISO NUMBERING SYSTEMISO NUMBERING SYSTEM

Bearing Type WIDTH SERIES

1st Digit Bearing 3 2 1 0

0Double row Angular

contact ball bearing , 32- -(032- -)

33 - -(033- -)

1Double Row Self aligned

ball bearing22 - (122 - -)

23 - (123 - -)

12- -(102- -)

13- -(103--)

2Spherical roller / roller

thrust brg.

230 - -

231 - -

232 - -

222 - -

223 - -213- -

202- -

203- -

3 Taper roller bearing

330 - -

331 - -

332 - -

320 - -

321 - -

322 - -

313--

302- -

303- -

4Deep groove ball

bearing, double row42 - (422 - -)

43 - (423 - -)

ISO NUMBERING SYSTEMISO NUMBERING SYSTEMBearing Type WIDTH SERIES

1st Digit Bearing 3 2 1 0

5 Thrust ball bearing522 - -

523 - -

511 - -

512 - -

6Deep groove ball brg., single

row622 - -

623 - -

60 - -(610 - -)

618 - -

619 - -

60 - -(600 - -)

62 - -(602 - -)

63 - -(603 - -)

7Angular contact ball bearing,

single row

70 - -(710 - -)

718 - -

719 - -

72 - -(702 - -)

73 - -(703 - -)

8 Cylindrical roller thrust brg.811 - -

812 - -

N Cylindrical / Needle roller brg.N22 - -

N23 - -N10 - -

N2 - -(N02 - -)

N3 - -(N03 - -)

NNCylindrical roller brg. Double

rowNN39

- -NN10 - - NN30 - -

QJFour point contact ball

bearingQJ QJ2 -(QJ02 - )

SUPPLEMENTARY DESIGNATIONSUPPLEMENTARY DESIGNATION

FREEDOM FIGHTERFREEDOM FIGHTER PANDITPANDIT JAWAHARLALJAWAHARLAL NEHRUNEHRU FIRST P.M. OF INDIAFIRST P.M. OF INDIA

22318E1 CC/ P63 W33

RING & ROLLERS OFCASE HARDENED STEEL

SPHERICALROLLER BEARING

DOUBLE ROW

B = 64 MM

OD = 190 MM

ID = 90

IMPROVED INTERNALDESIGN

P6 +C3

PERIPHERALGROOVE INOUTER RING WITH

THREE HOLES

PREFIX SUFFIX


PREFIXES : A prefix designates bearing components AR - Ball and cage assembly or roller and cage assembly

LNU 207 L= inner ring of cylindrical roller bearing NU 207

RNU 207 R= Outer ring and roller cage assembly of cylindrical roller bearing NU 207

SUFFIXES : Tell us about:-- 1) Internal design 4) Bearing accuracy 2) External design 5) Internal clearance 3) Cage 6) lubrication features

Some commonly used Suffixes 1)A, B, C, D and E -Tell us about Internal design of

the brg. e. g. 7025 B B= Single row Angular contact ball bearing with contact angle of 400

2) External Design X - Boundary dimensions altered to conform ISO standards RS - Synthetic rubber seal fitted at one side of or LS the bearing 2RS - Rubber Seal on both sides or 2LS

Z – Shield fitted at one side of the bearing

2Z – Shield fitted at both the sides

K – Tapered bore , taper 1:12 on diameter

K30 – Taper bore , taper 1:30 on diameter

N – Snap ring groove in outer ring

Cage : J – Pressed steel cage

Y - Pressed brass cage

P - Polyamide cage, reinforced with 25% glass fiber

M – Machined brass cage

V - Cage less ball and roller bearing

Some commonly used Suffixes


ACCURACY: P6 - Accuracy to ISO class 6

P5 - Accuracy to ISO class 5 (Greater than 6)

P4 - Accuracy to ISO class 4 (Greater than 5)

NOTE: Lesser the number higher the accuracy

C1 - Clearance less than C2

C2 - Clearance less than Normal

Normal

C3 – Clearance greater than Normal

C4 -- Clearance greater than C3

C5 -- Clearance greater than C4

INTERNAL CLEARANCE

BEARING DESIGNATION

SOME EXAMPLES

Brg. No. 1315 EKTN9 / C2

Here width series 0 is missing Brg. Becomes 10315

1 - Self Aligning Ball Bearing Double Row I.D. - 75mm O.D.– 16mm B – 37mm

E - Modified Internal Design (Better Ball Quality , Increased No. of balls )

K - Taper Bore Taper 1 : 12

TN9 - Reinforced plastic cage

C2 - Clearance less than normal ( Min . 23 microns , Max. 39 microns)

BEARING DESIGNATION

SOME EXAMPLES

Bearing No. 22318 CCK / P63 W33 2 – Type – Double row spherical roller bearing 2 – Width – 64mm 3 – OD – 190mm18 – ID – 18 X 5 = 90mmCC – Spherical roller bearing of C design with improved roller guidance (Improved internal design to reduce friction) K – Taper bore, Taper 1:12P63 – P6+C3 – Accuracy to ISO class 6 + C3 internal Clearance ( 0.1 to 0.135 mm)W33 – Peripheral groove in outer ring with 3 holes at 120 0 for lubrication

ALIGNMENT ANGLES OF DIFFERENT BEARINGS

Self Aligning Ball Bearings – 4 degree

Spherical Roller Bearings – a) Under low load – 2 degree b) Under high load- 0.5 degree.

Deep Groove Ball Bearing _ a) Series 62,63 & 64- 5 to 10 minutes. b) Series 160 & 60 – 2 to 6 minutes

Cylindrical Roller bearings – 1 to 3 minutes.

Taper Roller bearings – 1 to 1.5 minutes.

NOMINAL CONATCT ANGLES OF BEARINGS

Deep groove ball bearing radially displaced- 0 degree

Deep groove ball bearing axially displaced- 5 to 15 degrees.

Single Row Angular Contact Ball Bearing- 15 to 40 degrees.

Double Row Angular Contact Ball Bearing- 35 to 40 degrees.

Self Aligning Ball Bearing – 5 to 20 degrees.

Cylindrical Roller bearing – 0 degree.

Needle Roller Bearing – 0 degree.

Taper Roller Bearing – 10 to 30 degrees.

Spherical Roller Bearing – 4 to 18 degrees.

Angular Contact Thrust Ball Bearing – 60 degrees.

Spherical Roller Thrust Bearing – 50 degrees.

Thrust Ball / Needle Roller Bearing – 90 degrees.

Principles of Bearing CalculationsPrinciples of Bearing CalculationsStatic Stressing:- In rolling bearing Engineering the term static stressing refers to bearings , carrying a load when – Stationary 1) Subjected to small oscillating motion.

2) The load may be constant or variable.

Experience shows that rolling bearings under static loads can be stressed to such a degree that minor plastic deformation occur in the rolling surfaces. How much a bearing can be stressed statically can be calculated. Static Load Ratings :- An equivalent load under which the total permanent deformation of raceways and heavily loaded rolling elements which is to 1/10000 of the rolling element diameter. Index of static stressing , fs= Co / Po

Where Co = Static load rating fs

Po = Maximum permissible equivalent static load

fs = 1; when bearing is subjected to occasional rotation.

fs = 1.5 approx. ; where requirement of rotation is more

fs = 0.7 approx; when oscillating motion and no shock loads

fs> or = 0.8 ; when oscillation angle is very small. fs = 4 to 6 ; in case of spherical roller bearings because of it’s typical application .

Principles of Bearing CalculationsPrinciples of Bearing Calculations

1. The pure radial load on track and roller surfaces , generated by Fa &Fr , will be equal to Por which is known as EQUIVALENT STATIC LOAD.

2. Por will creat the same deformation on roller and track as will be created by Fa & Fr.

3. Por = X0 * Fr +Y0 * Fa Por = Equi. Static radial load F0 = Radial Load Factor Y0 = Axial Load Factor4. If Por creates deformation equal to -------- Ave. Roller Dia./ 10,000 Then Por = Cor = Basic Static Load Rating

5. a) Cor For Radial and Angular contact Ball Bearings:

Cor = 12.3 * i * Z* Dw2 *Cosα

Fr

Fa

Por

Principles of Bearing CalculationsPrinciples of Bearing CalculationsFr

Fa

Por

b) For Self aligning Ball Bearing Cor = 3.33 * I * Z * Dw2 * Cosαc) Thrust Ball Bearing Coa = 49 * Z * Dw2 * Sin αc) Radial Roller Bearing Cor = 21.6 * i * Z * Lwe * Dwe * Cos αd) Thrust Roller Bearing Coa = 98.1 * Z * Lwc * Dwe * Sin α

Where Cor = Basic static load rating Z = No. of rolling elements Dw = Rolling element diameter α = Contact angle Lwe = Effective length of rollers


Fa

Pr

DYNAMIC STRESSING

In rolling bearing engineering the term Dynamic Stressing refers to laoding Of a rotating bearing. After a longer time depending upon the load on running bearing fatigue Phenomenon occurs on the operating surfaces of rolling bearing. This Initiates micro cracks below the surface. With further operation, crack Enlarges and pitting develops. Finally flaking extends over large area of Operating surface.

1) The pure radial load on track and roller surfaces generated by forces Fa and Fr will be equal to Pr.2 So life obtained by applying Fa and Fr will be attained by the influence of Pr

Pr = X Fr + Y Fa for ball bearing if Fa / Fr > e


Fa

Pr

DYNAMIC STRESSING

Where Fr = Actual radial load Fa= Actual axial load X = Radial load factor Y = Axial load factor

Pr = 0.4 Fr + 0.4 Cos α Fa, When Fa / Fr > e

Pr = Fr when Fa / Fr ≤ e for cylindrical roller bearing

Pr = Fa for thrust bearing

E = 1.5 tan α for taper roller bearing.


Fa

Pr

DYNAMIC LOAD RATING

If a bearing runs for 106 revolutions without giving any sign of failure , then the equivalent load which is applied on it is called Dynamic Load Rating of the bearing and is denoted by C.

a) For Radial and angular contact ball bearings If Dw < or = 25.4mm then Cr = fc (I * Cos α )0.7 Z2/3 Dw1.8

If Dw > 25.4mm , then Cr = 3.647 fc (I * Cosα)0.7 Z2/3 Dw1.4

b) Radial roller bearing Cr = fc (I * Lwe * Cosα )7/9 Z3/4 Dw 29/27

c) Thrust roller bearing For α = 90 0 Ca = fc * Lwe7/9 * Z3/4 * Dwe29/27

For α ≠ 90 0 Ca = fc * ( Lwe * Cosα )7/9 Tanα Z3/4 Dwe 29/27

fc is a factor depends upon geometry of bearing and material.

BEARING LIFE

The rating life of a sufficiently large number of dimensionally identical bearings Is expressed by the number of revolutions or number of hours at constant speed reached or exceeded by 90% of the bearing group before the first sign of material failure appears.

In other words, Rating Life is the maximum number of revolutions which 90% of the group of dimensionally identical bearings , running at identical operating conditions had attended before the first evidence of material fatigue appears. The life equation :

L10 = ( C/P)n or C/P = ( L10)1/n Where L10 = Basic rating life in millions of revolutions C = Basic dynamic load rating P = Equivalent dynamic load n = Exponent for the life equation n = 3 , For Ball Bearings n = 10/3 , For Roller bearing

Life of bearing in hours :

L10h = ( 10 6 / 60* N ) * (C/P) n

Where L10h = Basic rating life in operating hours N = Rotational speed in rev. per minute

Modified Rating Life;-- With the development in following fields: Improved production process and production means1) Refined measuring tools2) More uniform and inclusion free material structure3) Stable lubricants4) New findings on friction and wear A new term called Corrected Nominal Life (Lna) is generated.

Lna = a1 * a2 * a3 * L10

BEARING LIFE

BEARING LIFE CONTD.

Lna = a1*a2*a3* L1oWhere , a1 = Correction coefficient for reliability other than 90% a2 = Correction coefficient taking in to account the material used a3 = correction coefficient making based upon the method of

lubrication and generally taken as 1

CORRECTION COEFFICIENT a1

Reliability % a1

90 1

95 0.62

96 0.53

97 0.44

98 0.33

98 0.21

BEARING LIFE CONTD.

ExampleA bearing 22318 CC / W33 made of S.K.F. standard steel is to rotate ata speed N = 500 rpm ,under a constant load Fr = 50,000 N . Bearing is oil lubricated and at operating temperature the viscosity of oil 35mm2/s.What is adjusted life for 98% reliability?

Solution P = Fr = 50,000 N a1 = 0.33 for 98% Reliability ( from table) dm = 0.5 ( d+D ) = 0.5( 90+190) = 140 mm Satisfactory lubrication will be obtained if the oil viscosity is ν1= 21 mm2/s

K = v / v1 = 35/21 = 1.67 ( from lubrication table) Corresponding to this K value a23 = 1.9 Lna = 0.33x1.4x(477000/50,000)10.3

= 850 million revolutions = 28300 operating hours

BEARING LIFE CONTD.ExampleA bearing 22318 CC / W33 made of S.K.F. standard steel is to rotate at a speed N = 500 rpm ,under a constant load Fr = 50,000 N . Bearing is oil lubricated and at operating temperature the viscosity of oil 35mm2/s.What is adjusted life for 98% reliability?

Solution P = Fr = 50,000 N a1 = 0.33 for 98% Reliability ( from table) dm = 0.5 ( d+D = 0.5( 90+190) = 140 mm Satisfactory lubrication will be obtained if the oil viscosity is ν1= 21 mm2/s

K = v / v1 = 35/21 = 1.67 ( from lubrication table) Corresponding to this K value a23 = 1.9 Lna = 0.33x1.4x(477000/50,000)10.3

= 850 million revolutions = 28300 operating hours

CLEANING AND INSPECTION OF BEARINGS

BEARING LUBRICATION

WHY THE BEARINGS HAVE TO BE LUBRICATED ?

In order to achieve its maximum life in service , a

rolling bearing must be lubricated.

BEARING LUBRICATION

• Grease constituents:-

Grease Lubrication:-

Application in which the bearing operates under

normal speed and temperature conditions, grease is

used.

Grease = 90% mineral oil + a thickener ( metallic soap )

Metallic soap = Metal hydroxide + fatty acid

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