Failure Mode Definition

The benefits of an FMEA are reliability enhancement and cost avoidance, not a measurable saving in the bottom line. Therefore, to be carried through in an effective way, the FMEA activities require the unconditional commitment of the management and a dedicated leadership. When managerial approval of the recommended actions is obtained, the actions are given deadlines. The control of the completion is assured by entries on the FMEA form, usually on a separate, shorter form, which lists the approved actions only.

Although the intention is the same, there is a slight difference in using risk level and RPN in the determination of risk acceptability. Risk level works by placing the assigned severity and probability level in a matrix as shown below (Table 5.4). FMEA is well known as one of the systems that helped to originate the HACCP approach to food safety management. Its method of considering the causes and potential effects of failure is useful in looking at prevention of problems, but it can also be employed when investigating all the potential causes of an issue in an incident. Table 1 shows an example of FMEA being used to explore the causes of metal complaints due to metal detection failure.

Pitfalls of FMEA

For example, the failure mode might be stress-corrosion cracking (SCC). Failure cause, however, might be chloride ions that were introduced into the system or residual stress in the component, which in turn made it susceptible to SCC. Assembling the right cross functional team with good knowledge and experience of conducting FMEA’s is key. We can achieve the greatest value by starting the FMEA before a product or process failure mode has been incorporated into the product or process. We should evaluate the use of an FMEA whenever we have a process, product or service that is being designed or redesigned or, for example, has a significant change of use. FMEA is highly subjective and requires considerable guesswork on what may and could happen and the means to prevent this.

It is seen that the results obtained by fuzzy logic are better than the ones obtained using the traditional FMEA method [22]. This chapter will analyze the failure modes of the starting air system by applying the fuzzy failure mode and effects analysis (FFMEA) fail mode method. The results might vary depending on the knowledge and experience of the expert. To even out and minimize the unpredictable epistemic uncertainty from subjective judgments, one needs to improve the reliability of measures used to collect the data.

Critical item/failure mode list

Sometimes FMEA is extended to FMECA (failure mode, effects, and criticality analysis) to indicate that criticality analysis is performed too. Having a formal process and record of your risk and defect reduction actions is hugely helpful as you design and develop your product or service. It’s also great for sharing knowledge across teams and designing out failure. Rather, it enhances good engineering by applying the knowledge and experience of a Cross Functional Team (CFT) to review the design progress of a product or process by assessing its risk of failure. Its focus is on addressing factors that can influence the reliability of a machine or a system. FMEA can be valuable as part of a DHA if there is mechanical complexity in the processing equipment and equipment failure can lead to process safety problems.

In addition to the FMEAs done on systems to evaluate the impact lower level failures have on system operation, several other FMEAs are done. Special attention is paid to interfaces between systems and in fact at all functional interfaces. The purpose of these FMEAs is to assure that irreversible physical and/or functional damage is not propagated across the interface as a result of failures in one of the interfacing units. These analyses are done to the piece part level for the circuits that directly interface with the other units. The FMEA can be accomplished without a CA, but a CA requires that the FMEA has previously identified system level critical failures.

As a diary, FMEA is started during the design/process/service conception and continued throughout the saleable life of the product. It is important to document and assess all changes that occur, which affect quality or reliability. When FMEA is done by a team, the payback is realized by identifying potential failures and reducing failure cost because of the collective expertise of the team who should understand the design/process. FMMEA combines life-cycle environmental and operating conditions and the duration of the intended application with knowledge of the active stresses and potential failure mechanisms. Potential failure mechanisms for a product are determined based on known failure mechanisms, functional sites, and materials in the product, as well as the anticipated stresses arising in the product. In addition, each part failure postulated is considered to be the only failure in the system (i.e., it is a single failure analysis).

The RPNs suggest that, as a result, failure mode A is the failure mode to work on first. Deciding when to take an action on the FMEA has historically been determined by RPN thresholds. Quality-One does not recommend the use of RPN thresholds for setting action targets.

Further, it increases the awareness of the product features by all involved parties and it provides a basis for an assessment of reliability, maintainability, and safety of similar or newly designed products. Teams use FMEA to evaluate processes for possible failures and to prevent them by correcting the processes proactively rather than reacting to adverse events after failures have occurred. This emphasis on prevention may reduce risk of harm to both patients and staff. FMEA is particularly useful in evaluating a new process prior to implementation and in assessing the impact of a proposed change to an existing process.

• It is also more rigorous and accurate in determining the root causes of failures and their consequences with respect to product safety.
• It can also be helpful in evaluating the reliability of protective systems, such as the analyzers, flow controllers, and gas supply of a system providing nitrogen inerting to a piece of equipment.
• An additional column is added to the FMEDA and probability of detection for each component failure mode is estimated.
• Functional descriptions are created for the systems and allocated to the subsystems,
  covering all operational modes and mission phases.

Failure B has minor impact each time it occurs, but it happens often, although it is almost always discovered before affecting the customer. Failure C has by far the highest severity, but occurs only rarely and is invariably discovered before affecting the customer. The FMEA in the following example is from a project looking at a commercial loan process. In this process a customer fills out a loan application, the data from the application form is entered into a database, and the customer is sent checks. The RPN is used to place a priority on which items need additional quality planning. This e-learning course is designed to establish the use of FMEAs and to help you learn the skills needed to practice risk reduction and defect prevention.