Question

Reliability is a concept that should be understood in the development of systems. Discuss the difference between series and parallel (redundant) networks and how such networks can increase or decrease total reliability of the system.

Discuss the FMECA process its components, purpose and how it relates to system reliability.

Maintainability and maintenance are important and related to each other. Describe each and the relationship to each other.

Answer 1

Reliability

system in series:

1) If the components are in series, system performs satisfactorily if all components are fully functional

2) If the components are in series, reliability increases if the number of components decreases

system in parallel:

1) If the components are in parallel, system performs if any one component remains operational

2) If the components are in parallel, the reliability decreases if the number of components decreases.

FMECA

The Failure Mode, Effects and Criticality Analysis (FMECA) is a reliability evaluation/design technique which examines the potential failure modes within a system and its equipment, in order to determine the effects on equipment and system performance.Each potential failure mode is classified according to its impact on mission success and personnel/equipment safety.

1)Determines the effects of each failure mode on system performance

2) Provides data for developing fault tree analysis and reliability block diagram models

3)Facilitates investigation of design alternatives to consider high reliability at the conceptual stages of the design

4) Provides a foundation for qualitative reliability, maintainability,safety and logistics analyses

The results of the FMECA:
1) Highlight single point failures requiring corrective action
2)Rank each failure according to the severity classification of the failure effect on mission success and personnel/equipment safety
3) Provide estimates of system critical failure rates
4) Provide a quantitative ranking of system and/or subsystem failure modes
5) Identify reliability/safety critical components

Since the FMLCA is used to support maintainability, safety and logistics analyses, it is important to coordinate the analysis to prevent duplication of effort within the same program. FMECA is an iterative process. As the design becomes mature, the IMIECA must reflect the additional detail. When changes are made to the design,FMECA must be performed on the redesigned sections. This ensures that the potential failure modes of the revised hardware will be addressed. If the FMECA is performed correctly, it becomes an important tool for making program decisions regarding trade-offs affecting design integrity.