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Manual for Life Cost Based FMEA

6) Establish periodic maintenance or check-ups to enhance availability and safety.

3. Concept of Life Cost Based FMEA

Lifecycle cost is the total monetary cost of ownership of a product during the lifetime of its use. This includes acquisition cost, marketing, cost of ownership

(repair, scheduled maintenance, and usage costs), and

of

the

product.

Acquisition

cost

is

relatively

well

sometimes retirement cost perceived and defined in

industry. However, cost design stage. Repair and

of ownership is overlooked most scheduled maintenance costs are

of the time during the hard to predict and no

formal set of tools exist to make developed to predict unexpected cost between different designs.

predictions. failure costs

Life and

Cost Based FMEA ultimately compare

is a tool lifecycle

From Equation 1, expected failure cost is the sum of all possible failures with respect to their probability and cost of failure. Probability of failure can be determined from field data, test data, or empirical data. Cost of failure can be measured in terms of time as will be discussed in the following and hardware cost.

3.1. Cost

Failures may occur at any stage of the life cycle and can be detected either during the same stage or during subsequent stages. The failure cost is smallest when the origin and detection occur during the same stage. The failure cost increases as the origin and detection stages become further apart.

The example shown in Figure 2 is where a failure is detected during the operations stage and the initial origin of the failure is a design error. Due to design error, the part has to be redesigned, remanufactured, and reinstalled. There may be some delay between each of these activities also. Recovery time is the whole time the system is inoperable due to the failure. Recovery time is associated with lost opportunity.

Figure 2 shows the four possible failure initiating stages and the failure detection stages.

  • Failure origin indicates when the failure has been initially introduced. The four possible stages are: Design, Manufacture, Installation, and Operation.

  • Detection phase indicates the stage at which the failure has been realized. The four possible stages are: Design Review, Inspection, Testing, and Operation.

Time is the basic unit used to convert failure consequence into cost. Detection time, fixing time, delay time and loss time are the four fundamental time penalties in this analysis.

FMEA MANUAL By S. Rhee and C.M. Spencer

9/26

January 2009

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