System Definition and Model
The reliability of any item is influenced by a wide variety of factors, and it is essential that as many of these as possible are taken into account when comparing proposed and existing designs. While not in any order, the factors that should be considered and defined for the proposed system include:
• The purpose and functions of the system or systems.
• The main performance, safety and physical characteristics.
• The worst case reliability requirements.
• The operational and environmental conditions of use.
• The complexity and ‘state of the art’ involved.
• The design and development time scale and cost constraints.
• The facilities and resources available for reliability development testing.
• Whether the proposed design is a natural development of an existing design or is new concept.
• Whether new manufacturing techniques are required.
This list is not intended to be exhaustive. Any additional factors that may assist in the comparison with similar designs should be noted during system definition. A reliability model should be developed to show the reliability relationships within the proposed system design. (See Reliability Modelling.)