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Selection

The selection of the right Babbitt metal for a given bearing is part science and part art. In the repair and rebuilding of an existing bearing, it is often most important to duplicate the original bearing Babbitt and properly prepare the bearing surface for this new Babbitt coating. Many repair facilities receive bearings with little or no technical documentation. If you need help identifying the original Babbitt, Kapp Alloy can analyze a sample of the Babbitt material for a nominal charge. Simply melt out a small plug, or send us turnings from the old Babbitt lining. We will analyze them to determine the original formulation of the Babbitt lining.

 

Typical engineering data for several common Babbitt formulations is shown in the table below. It is important to note that changing the Babbitt formula for an existing bearing changes the forces and wear on the entire bearing – shell, lining, lubricant, etc. The discussion on the science of Babbitt selection is meant to educate, but also to emphasize that such changes should not be undertaken lightly. Changing the Babbitt formula in an existing bearing can lead to precisely the bearing failure you are working to avoid.

 

ASTM Alloy Number

Yield Point, psi D (MPa)

Johnson's Apparent Elastic Limit psi (MPa) E

Melting Point

Proper Pouring Temp

68°F (20°C)

212°F (100°C)

68°F (20°C)

212°F (100°C)

1

4,400 (30.3)

2,650 (18.3)

2,450 (16.9)

1,050 (7.2)

433°F (223°C)

825°F (441°C)

2

6,100 (42.0)

3,000 (20.6)

3,350 (23.1)

1,100 (7.6)

466°F (241°C)

795°F (424°C)

3

6,600 (45.5)

3,150 (21.7)

5,350 (36.9)

1,300 (9.0)

464°F (240°C)

915°F (491°C)

7

3,550 (24.5)

1,600 (11.0)

2,500 (17.2)

1,350 (9.3)

464°F (240°C)

640°F (338°C)

8

3,400 (23.4)

1,750 (12.1)

2,650 (18.3)

1,200 (8.3)

459°F (237°C)

645°F (341°C)

15

No data

No data

No data

No data

479°F (248°C)

662°F (350°C)

D The values of yield point were taken from stress-strain curves at deformation  of 0.125% of gage length

E Johnson's apparent elastic limit is taken as the unit stress at the point where the slope of the tangent to the curve is 2/3 times its slope in origin

 

The engineering of a bearing’s Babbitt lining is usually completed during the design of the machine. Thus, much of what appears below is relevant to the OEM and design engineers. In selecting the proper type of Babbitt for a particular job there are a number of factors to take into consideration. The most important are:

1. Surface speed of the SHAFT
2. Load the bearing is required to carry

Secondly, but no less important, the following points must also be taken into account:

A. Continuity of service

D. Lubrication

B. Bonding possibilities

E. Cleanliness

C. Cooling facilities

F. Attention given to the bearings in question

 
For example, a bearing in continuous use in a harsh environment without regular maintenance will require different Babbitt and lubrication than a bearing in intermittent use in a clean light duty environment. This so-called art is really the combination of the technician’s experience and the prior performance of the bearing being rebuilt.

 

If the bearing has performed well in use over many years, the bearing needs simply to be rebuilt to its original specification and formulation. In this case the technician’s greatest concerns are:

 

1. Bearing shell surface preparation;

2. Bonding characteristics of the tinning compound and the Babbitt layer; and,

3. Load bearing surface preparation and finish.

There is no doubt that if a bearing be highly loaded in relation to its size, a high tin alloy is desirable; whereas for much slower speed work and less heavily loaded bearings, a lead-base one may be employed, and is far more economical.

1. Surface speed of the shaft: (The number of feet traveled per minute by the shaft circumferentially.)

 

 

 

 

 

 

 

Pi = 3.1416

Formula:

Pi x D x RPM

= S

D = Diameter of Shaft

 

12

RPM = Revolutions Per Minute

 

 

 

S = Surface speed of the Shaft

 

 

 

Example:

Determine the surface of a 2 inch diameter shaft going 1,400 RPM

 

Pi x D x RPM

= 3.1416 x 2 x 1,400 = 733.04 Ft/min 

 

12

12

 

 

 

2. Load Bearing is required to carry:  (The weight which is being exerted through the combined weights of the shaft and any other direct weights on the shaft and measured in pounds per square inch.)

 

 

 

 

 

 

 

W = Total weight carried by bearing

Formula:

___W___

= L

I.D = Inside diameter of bearing

 

I.D x L.O.B.

L = Load bearing required to carry

 

 

 

L.O.B = Length of Bearing

 

 

Example:

Determine the load on a bearing of a 2 inch I.D bearing, 5 inches long and carrying a weight of 3,100 lbs

 

_____W_____

3,100  =  310 Lbs/sq.in

 

I.D x L.O.B.

     2 x 5

 

 

 

Babbitt Classifications

There are many specific formulations for bearing Babbitt, each designed to meet the needs of specific bearings in use. However, Babbitt can be classified as either Tin-Based or Lead-Based according to the following table.

 

Babbitt Classification:

LIMITS

Surface Speeds
(ft./min.)

LOAD
(lbs./sq. in.)

MIN.

MAX.

MIN.

MAX.

Tin-Based Babbitts

1,000

2,400

100

2,000

Lead Based Babbitts

100

1,000

100

500

 

As most equipment and engine bearings today operate at high speeds, Tin-Based Babbitt bearings are far more common. The chart below list names and ASTM formulations of common Tin-Based Babbitt alloys.

 

Tin-Based Babbitt Alloys – High Speed and High Pressure Bearings

 

 

Industry Name

ASTM B23

QQ-T-390A

Sn (Tin)

Sb (Antimony)

Cu (Copper)

Pb (Lead)

Marine 11 D

-

-

90.0 - 92.0

4.5 - 5.5

3.5 - 4.5

0.35 (Max)

No. 1, DuraKapp1™

Grade 1

No. 1

90.0 - 92.0

4.0 - 5.0

4.0 - 5.0

0.35 (Max)

NF A 56-101 (Code 101)

-

-

89.0 - 91.0

5.75 – 7.25

2.75 – 4.25

0.35 (Max)

NF A 56-101 (Code 111)

-

-

89.0 - 91.0

5.75 – 7.25

2.75 – 4.25

0.10 (Max)

Marine 11R

-

-

89.0 - 89.5

7.5 - 8.5

2.5 - 3.0

0.35 (Max)

Nickel Genuine, DuraKapp2™

Grade 2

No. 2

88.0 - 90.0

7.0 - 8.0

3.0 - 4.0

0.35 (Max)

Marine 11

-

-

88.0 - 90.0

5.5 - 6.0

5.0 - 5.5

0.35 (Max)

4X Royal Nickel Genuine

-

-

87.5 - 89.5

7.25 - 7.75

3.25 - 3.75

0.35 (Max)

Diesel Special

-

-

87.5 - 88.0

6.5 - 7.0

5.0 - 6.0

0.35 (Max)

NF A 56-101 (Code 102)

-

-

87.0 - 89.0

6.75 – 8.25

2.75 – 4.25

0.35 (Max)

NF A 56-101 (Code 112)

-

-

87.0 - 89.0

6.75 – 8.25

2.75 – 4.25

0.10 (Max)

Grade 11, DuraKapp11

Grade 11

-

86.0 - 89.0

6.0 - 7.5

5.0 - 6.5

0.35 (Max)

SAE 11

-

-

85.0 - 87.0

7.0 - 8.0

6.0 - 7.0

0.35 (Max)

Imperial Genuine

-

-

85.0 - 87.0

6.5 - 7.5

6.5 - 7.5

0.35 (Max)

Turbine

-

-

84.0 - 86.0

6.5 - 7.5

7.5 - 8.5

0.35 (Max)

Royal Armature

-

-

83.5 - 84.0

8.0 - 8.5

7.5 - 8.5

0.35 (Max)

Super Tough, DuraKapp3™

Grade 3

No. 3

83.0 - 85.0

7.5 - 8.5

7.5 - 8.5

0.35 (Max)

NF A 56-101 (Code 103)

-

-

82.0 - 84.0

10.25 – 11.75

5.25 – 6.75

0.35 (Max)

NF A 56-101 (Code 113)

-

-

82.0 - 84.0

10.25 – 11.75

5.25 – 6.75

0.10 (Max)

No. 4

-

No. 4

80.5 - 82.5

12.0 - 14.0

5.0 - 6.0

0.35 (Max)

NF A 56-101 (Code 104)

-

-

79.0 - 81.0

9.25 – 10.75

9.25 – 10.75

0.35 (Max)

NF A 56-101 (Code 114)

-

-

79.0 - 81.0

9.25 – 10.75

9.25 – 10.75

0.10 (Max)

NF A 56-101 (Code 106)

-

-

79.0 - 81.0

11.25 – 12.75

5.00 – 7.00

1.5 – 2.5

NF A 56-101 (Code 105)

-

-

77.0 - 79.0

12.25 – 13.75

8.25 – 9.75

0.35 (Max)

NF A 56-101 (Code 115)

-

-

77.0 - 79.0

12.25 – 13.75

8.25 – 9.75

0.10 (Max)

Grade 4, DuraKapp4™

Grade 4

-

74.0 - 76.0

11.0 - 13.0

2.5 - 3.5

9.3 - 10.7

NF A 56-101 (Code 107)

-

-

73.0 - 75.0

6.00 – 8.00

3.00 – 5.00

3.00 – 5.00

No. 5

-

No. 5

61.0 - 63.0

9.5 - 10.5

2.5 - 3.5

24.0 - 26.0


Maximum Allowable Impurities:      Fe=0.08, As=0.10, Bi=0.08, Zn=0.005, Al=0.005, Cd=0.05

 

Lead-Based Babbitt bearings are encountered most often in the rebuild and restoration of antique engines, motors and compressors. The chart below lists the most common Lead-Based Babbitt formulations.

 

Lead-Based Babbitt Alloys – Low Speed and Low Pressure Bearings

 

 

INDUSTRY NAME

ASTM B23

QQ-T-390A

Sn
(Tin)

Sb
(Antimony)

Pb
(Lead)

As
(Arsenic)

Choker

-

-

-

6.5 - 7.5

92.0 - 94.0

0.20

Durite, DuraKapp15™

Grade 15

No. 10

0.8 - 1.2

14.5 - 17.5

Balance

0.8 - 1.4

Hardware No. 4

-

-

1.0 - 2.0

12.3 - 14.3

84.2 - 86.2

0.20

Silverstone

-

-

1.0 - 3.0

17.5 - 18.5

Balance

0.25 (Max)

No. 13

-

No. 13

4.0 - 6.0

8.0 - 10.0

83.0 - 88.0

0.20

Mill Anchor

-

-

4.0 - 6.0

11.5 - 12.5

Balance

0.25 (Max)

Royal, DuraKapp8™

Grade 8

No. 6

4.5 - 5.5

14.0 - 16.0

Balance

0.30 - 0.60

Star

-

-

5.0 - 5.5

13.5 - 14.5

Balance

0.30 - 0.60

NF A 56-101 (Code 201)

-

-

5.0 - 7.0

14.0 – 16.0

77.0 – 79.0

(0.5-1.0 Cu)

Grade 13, DuraKapp13™

Grade 13

-

5.5 - 6.5

9.5 - 10.5

Balance

0.25 (Max)

NF A 56-101 (Code 202)

-

-

9.0 - 11.0

14.0 – 16.0

74.0 – 76.0

(0.5-1.0 Cu)

No. 11

-

No. 11

9.0 - 11.0

11.5 - 13.5

74.0 - 79.0

0.20

Sawguide

-

-

9.0 - 11.0

18.5 - 19.5

Balance

0.25 (Max)

Heavy Pressure, DuraKapp7™

Grade 7

No. 7

9.3 - 10.7

14.0 - 16.0

Balance

0.30 - 0.60


Maximum Allowable Impurities:     Cu=0.50, Fe=0.10, Bi=0.10, Zn=0.005, Al=0.005, Cd=0.05

 

 

 

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