Concept of FMEA

FMEA primarily plays a role as prevention oriented technique to enhance the inherent reliability of a product or service. Each of items of a design is considered in relation to its likely mode of failure, the probability of occurrence, and the effects of the failures.

There are two forms of FMEA. These are following:

• Design FMEA which involves the analysis of the potential failure of a new manufactured goods or service, and
• Process FMEA that involves failure analysis of the process or processes in the manufacture or provision of the product or service.

A comprehensive FMEA for a total design is a sizable task. Though, this method is a very effective formal reliability design review technique. The method is specifically suited to analog system (whether electronic, electrical or mechanical), for purely digital electronic systems are extremely complex. Also, the designer has less control over individual elements of the system, as these are contained within the integrated circuit packages. FMEA provides a valuable spin-off, as the analysis is an outstanding starting point for producing block diagram, reliability analysis & diagnostic charts for repair purposes. A considerable amount of work in generating diagnostic routine & preparing user maintenance handbooks might be saved if FMEA worksheets are utilized as the basis for this work.

The detailed level to which FMEA is taken should be based upon the purpose for which it is performed. For instance, consideration of all of possible failure modes within a hydraulic sequence valve or an operational amplifier would not generally be included in the analysis of a system of which they were components. Rather, we would be concerned with the failure modes of their outputs. The designer of the valve or operational amplifier would, though, have to analyze the effects of all modes of failure in the item. The level of analysis might also be affected by the stage attained by the project. For big systems, feasibility studies might only generate functional subsystems, with much of the detailed design yet to be performed. The initial FMEA would then be associated to the failures of these subsystems or blocks. This forms the basis for updated versions as design proceeds, and this is useful in its own right for aiding the assessment of options & identification of critical features.