# Bearing Life Bearing Life Bearing life is defined

• Slides: 59

Bearing Life

Bearing Life Bearing life is defined as the Number of revolutions that a bearing undergoes under a constant load ( Equivalent Dynamic Bearing Load ) before the first sign of fatigue failure occurs.

Bearing Life Fatigue - Spalling

Bearing Life Equivalent Dynamic Bearing Load

Bearing Life Equivalent Dynamic Bearing Load Fv FH

General Catalogue – Page 49 Bearing Life Equivalent Dynamic Bearing Load Values of Bearing Reaction Forces Can be calculated by using : S H = 0 ( Total of all horizontal forces = 0) S V = 0 ( Total of all vertical forces = 0) S M = 0 ( Total of all moments = 0)

General Catalogue – Page 49 Bearing Life Equivalent Dynamic Bearing Load P = X F r + Y Fa Where : X = Radial Load Factor Y = Axial Load Factor

Bearing Life Radial & Axial Load Factors DGBB : General Catalogue Pages 184 - 185 P = Fr if Fa/Fr </= e P = X F r + Y Fa if Fa/Fr > C 0 is given in Pages 186 – 253 e is given in Page 185 e

Bearing Life Radial & Axial Load Factors SABB : General Catalogue Page 261 P = F r + Y 1 Fa if Fa/Fr </= e P = 0. 65 Fr + Y 2 Fa if Fa/Fr > Y 1, Y 2 & e are given in Pages 264 – 283 e

Bearing Life Radial & Axial Load Factors ACBB : General Catalogue Page 292 Single Bearing / Tandem : P = Fr if Fa/Fr </= 1. 14 P = 0. 35 Fr + 0. 57 Fa if Fa/Fr > 1. 14 Paired X or O : P = Fr + 0. 55 Fa P = 0. 57 Fr + 0. 93 Fa if if Fa/Fr </= 1. 14 Fa/Fr > 1. 14

Bearing Life Radial & Axial Load Factors DRACBB : General Catalogue Page 311 P = Fr + 0. 73 Fa P = 0. 62 Fr + 1. 17 Fa if if Fa/Fr </= 0. 86 Fa/Fr > 0. 86

Bearing Life Radial & Axial Load Factors CRB : General Catalogue Page 336 P = Fr For Flanged CRB, P = Fr P = 0. 92 Fr + Y Fa if Fa/Fr </= e if Fa/Fr > e Y & e are given in Page 336

Bearing Life Radial & Axial Load Factors SRB : General Catalogue Page 467 P = F r + Y 1 Fa if Fa/Fr </= e P = 0. 67 Fr + Y 2 Fa if Fa/Fr > Y 1, Y 2 & e are given in Pages 470 – 511 e

Bearing Life Radial & Axial Load Factors SRTRB : General Catalogue Page 520 - 521 P = Fr P = 0. 4 Fr + Y Fa if Fa/Fr </= e if Fa/Fr > Y & e are given in Pages 526 – 585 e

Bearing Life Radial & Axial Load Factors Paired TRB : General Catalogue Page 589 P = F r + Y 1 Fa if Fa/Fr </= e P = 0. 67 Fr + Y 2 Fa if Fa/Fr > Y 1, Y 2 & e are given in Pages 590 – 593 e

Bearing Life Radial & Axial Load Factors Th. BB / CRTh. B : General Catalogue Page 597/622 P = Fa

Bearing Life Radial & Axial Load Factors SRTh. B : General Catalogue Page 646 P = Fa + 1. 2 Fr if Fr </= 0. 55 Fa P = 0. 88(Fa + 1. 2 Fr ) if adjustable assembly & Fr </= 0. 55 Fa

Bearing Life Fluctuating Bearing Load Constant Mean Load Fm = 3 ( F 13 U 1 + F 23 U 2 + F 33 U 3 + ……. ) U Where F 1, F 2 etc = Constant Loads during U 1, U 2 revolutions U = Total number of revolutions ( U = U 1 + U 2 + U 3……)

General Catalogue – Page 35 Bearing Life L 10 = C p P ( ) Lundberg Palmgren Equation 1947

General Catalogue – Page 35 Bearing Life C p P ( ) C p a a = (P) L 10 = Lna 1 23 Lundberg Palmgren Equation 1947 Adjusted Rating Life Equation 1977

General Catalogue – Page 40 Bearing Life C p P ( ) C p a a = (P) C p =aa (P) L 10 = Lna L naa Lundberg Palmgren Equation 1947 1 23 Adjusted Rating Life Equation 1977 1 SKF New SKF Life Equation 1989

Bearings are selected based on: Ø Load Ø Speed Ø Temperature Ø Environment Ø Life expectancy

General Catalogue – Page 27 Basic Terminologies : 1. Static Load 1. Dynamic Load 1. Life Requirement

Bearing Life considerations vary depending on : Type of Rolling Element 1. 2. Ball Roller a. Cylindrical b. Needle c. Tapered d. Spherical I Symmetrical II Asymmetrical

Different Applications require different Life: 1. Hand Tool 2. Elevator 3. Machine Tools 4. Industrial Fans 5. Pumps 6. Water Circulating Pumps

General Catalogue – Page 53 Load carrying capacity Basic dynamic load rating C P Basic static load rating C P 0 P 0 The ISO life equation C p The static safety factor L 10 = basic rating life, millions of s 0 revolutions C = basic dynamic load rating, N P = equivalent dynamic bearing load, N p = exponent of the life equation With the load P = C the L 10 life will be 1 million revolutions P 0 = equivalent static bearing load, N L 10 = (P) s 0 = C 0 P 0 = static safety factor C 0 = basic static load rating, N With the load P = C 0 the static safety factor s 0 will be 1

General Catalogue – Page 52 Equivalent Static Bearing Load P 0 = X 0 Fr + Y 0 Fa Where : X 0 = Static Radial Load Factor Y 0 = Static Axial Load Factor

Equivalent Static Bearing Load Radial & Axial Load Factors DGBB : General Catalogue Pages 184 P 0 = 0. 6 Fr + 0. 5 Fa If P 0 < Fr, then P 0 = Fr

Equivalent Static Bearing Load Radial & Axial Load Factors SABB : General Catalogue Pages 261 P 0 = F r + Y 0 Fa Y 0 given in bearing tables pages 264 - 283

Equivalent Static Bearing Load Radial & Axial Load Factors ACBB : General Catalogue Pages 292 P 0 = 0. 5 Fr + 0. 26 Fa If P 0 < Fr, then P 0 = Fr

Equivalent Static Bearing Load Radial & Axial Load Factors CRB : General Catalogue Pages 336 P 0 = F r

Equivalent Static Bearing Load Radial & Axial Load Factors SRB : General Catalogue Pages 467 P 0 = F r + Y 0 Fa Y 0 given in bearing tables pages 470 - 511

Equivalent Static Bearing Load Radial & Axial Load Factors SRTRB : General Catalogue Pages 520 P 0 = 0. 5 Fr + Y 0 Fa If P 0 < Fr, then P 0 = Fr Y 0 given in bearing tables pages 526 - 585

Equivalent Static Bearing Load Radial & Axial Load Factors Th BB & Th RB : General Catalogue Pages 597 , 622 & 637 P 0 = Fa

Equivalent Static Bearing Load Radial & Axial Load Factors SR Th B : General Catalogue Page 646 P 0 = Fa + 2. 7 Fr If Fr < 0. 55 Fa

Bearing Life L 10 = C p P ( ) Lundberg Palmgren Equation 1947 L 10 = Basic Rating Life, Millions of Revolutions C P p = Basic Dynamic Load Rating , N = Equivalent Dynamic Bearing Load, N = Exponent of the life equation = 3 for ball bearings = 10/3 for roller bearings

Bearing Life L = 10 h 1 000 60 n ( ) C P p Lundberg Palmgren Equation 1947 L 10 h = Basic Rating Life, Operating Hours C P p n = Basic Dynamic Load Rating , N = Equivalent Dynamic Bearing Load, N = Exponent of the life equation = 3 for ball bearings = 10/3 for roller bearings = Rotational Speed rpm

General Catalogue – Page 34

General Catalogue – Page 33

Adjusted Rating Life Equation L = a 1 a 23 na C p P ( ) Lna = Adjusted Rating Life, Millions of Revolutions a 1 = Life Adjustment Factor for Reliability a 23 = Life Adjustment Factor for Material and Lubrication

General Catalogue – Page 35 Reliability Factor a 1

General Catalogue – Page 39 Material & Lubrication Factor a 23

New SKF Life Equation 1989 L = a 1 a SKF naa C p (P) Lnaa = Adjusted Rating Life to new life theory, Millions of Revolutions a 1 = Life Adjustment Factor for Reliability a. SKF = Life Adjustment Factor for Material, Lubrication, Minimum load and Contamination

General Catalogue – Page 41

General Catalogue – Page 42

General Catalogue – Page 43

General Catalogue – Page 44

Oscillating Bearing Life L 10 osc = 180 / 2 g * L 10 Where L 10 osc = Basic rating life in Millions of revolutions g = Oscillation amplitude ( Angle of maximum deviation from centre position), degrees For determining the required viscosity of the lubricating oil, equivalent rotational speed is calculated using : n = ( 2 g / 180 ) nosc

General Catalogue : Page 65

P M (t h o us an ds ) Deep Grove Ball Bearing Speed Ratings 6217 Series