Factors of Safety

Factors of Safety - FOS - are important in engineering design

Factors of Safety - FOS - are a part of engineering design. Typical overall Factors of Safety are indicated below:

Equipment

Factor of Safety
- FOS

Aircraft components 1.5 - 2.5
Boilers 3.5 - 6
Bolts 8.5
Cast-iron wheels 20
Engine components 6 - 8
Heavy duty shafting 10 - 12
Lifting equipment - hooks .. 8 - 9
Pressure vessels 3.5 - 6
Turbine components - static 6 - 8
Turbine components - rotating 2 - 3
Spring, large heavy-duty 4.5
Structural steelwork in buildings 4 - 6
Structural steelwork in bridges 5 - 7
Wire ropes 8 - 9

Design Factors of Safety are often published in technical standards but there is no dedicated standard to the subject.

Note that for statutory items such as cranes and pressure vessels FOS are specified in the design codes.

General recommendations

Applications

Factor of Safety
- FOS

For use with highly reliable materials where loading and environmental conditions are not severe and where weight is an important consideration 1.3 - 1.5
For use with reliable materials where loading and environmental conditions are not severe 1.5 - 2
For use with ordinary materials where loading and environmental conditions are not severe 2 - 2.5
For use with less tried and for brittle materials where loading and environmental conditions are not severe 2.5 - 3
For use with materials where properties are not reliable and where loading and environmental conditions are not severe, or where reliable materials are used under difficult and environmental conditions 3 - 4

Related Topics

  • Miscellaneous - Miscellaneous engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more

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