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Failure Rates..

Basic Information on Failure Rates

The following tables includes a number of mechanical items and representative failure rate information.   The tables also include qualifying factors.   The information included is of limited value and is not current and is in no way representive a specific products.  The failure rate of one company's product could be an order less than another companies.  

The only real value of this table is in providing realistic relative reliabilities of different components. For most of the components in the table below more accurate reliability information is provided in the suppliers literature.

Note: 106 hours = 114 years continuous operation....

Failure Rate Fo = Fr. C1 .C2 .C3


Mechanical item Modifier Failure Rate = Fr
    / 106 hours
Ball Bearing Heavy Duty 20
Ball Bearing Light Duty 10
Roller bearing   5
Journal Bearing   5
Shafts Highly Stressed 0.2
Shaft Lightly Stressed 0.02
Pins   15
Pivots   1
Couplings   5
Belt Drives   40
Spur Gears   10
Helical Gears   1
Friction Clutches   3
Magnetic Clutches   6
Springs Highly Stressed 1
Springs Lightly Stressed 0.2
Hair Springs   1
Calibration Springs Creep 2
Calibration Springs Breaking 0.2
Vibrations Mounts   9
Mechanical Joints   0,2
Grub Screws   0,5
Nuts   0,02
Bolts   0,02
Rack and Pinion Assemblies   2,0
Knife Edge fulcrums   10
Bellows   5
Diaphragms Metal 5
Diaphragms Rubber 8
Gaskets   0,5
Rotating Seals   7
Sliding Seals   3
O Ring Seals   0,2
Filters Blockage 1
Filters Leakage 1
Fixed Orifices   1
Variable Orifices   5
Restriction   5
Pipes   0,2
Pipe Joints   0,5
Unions and Junctions   0,4
Hoses Heavily stressed 40
Hoses Lightly stressed 4
Ducts   1
Pressure Vessels General 3
Pressure Vessels High Standard 0,3
Relief Valves Leakage 2
Relief Valves Blockage 0,5
Hand Operated Valves   15
Ball Valves   0,5
Solenoid Valves   30
Control Valves   30
Pistons   1
Cylinders   0,1
Jacks   0,5
Pressure Gauges   10
Pressure Switches   15
Bourdan Tubes Creep 0,2
Bourdan Tubes Leakage 0,05
Nozzle/Flapper assembles Blockage 6
Nozzle/Flapper assembles Breaking 0,2


Environment Factor C1
Ideal Static 0,1
Vibrations Free 0,5
Ground based 1,0
Ship 2,0
Road 3,0
Rail 4,0
Aircraft 10,0
Rating % of Normal C2
140 4
120 2
100 1
80 0,5
60 0,3
40 0,2
20 0,1
Temperature (Degrees C) C3
0 1,0
20 1,0
40 1,3
60 2,0
80 4,0
100 10,0
120 30,0


Links providing relevant information

  1. Weibull Databases...A table of failure rates. Probably more reliable than above

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Last Updated 10/01/2013