Failure Mode and Effect Analysis

FMEA is a procedure in operations management for analysis of potential failure modes within a system for classification by severity or determination of the effect of failures on the system.

Benefits

• Captures the collective knowledge of a team
• Logical, structured process for identifying process areas of concern
• Documents and tracks risk reduction activities
• Provides historical records; establishes baseline
• Helps increase customer satisfaction and safety

Limitations

• Prioritizes but doesn’t’ correct
• Only as good as your team
• Time-consuming
• Scopes can become too large
• Operators can provide excessive issues
• Not updating the existing FMEA charts

Applications

FMEA is most commonly applied but not limited to design (Design FMEA) and manufacturing processes
(Process FMEA).

Design Failure Modes and Effects Analysis (DFMEA) identifies potential failures of a design before they occur. DFMEA then goes on to establish the potential effects of the failures, their cause, how often and when they might occur, and their potential seriousness. Process Failure Modes and Effects Analysis (PFMEA) is a systemized group of activities intended to:

• Recognize and evaluate the potential failure of a product/process and its effect,
• Identify actions that could eliminate or reduce the occurrence, or improve detectability,
• Document the process, and Track changes to the process incorporated to avoid potential failures.

Read also: Fault tree analysis

FMEA Procedure

Describe the product/process and its function. An understanding of the product or process under consideration is important to have clearly articulated. This understanding simplifies the process of analysis by helping the engineer identify those product/process uses that fall within the intended function and which ones fall outside. It is important to consider both intentional and unintentional uses since product failure often ends in litigation, which can be costly and time-consuming.

Create a Block Diagram of the product or process. A block diagram of the product/process should be developed. This diagram shows major components or process steps as blocks connected together by lines that indicate how the components or steps are related. The block diagram should always be included with the FMEA form.

Complete the header on the FMEA Form worksheet: Product/System, Subsys./Assy., Component, Design Lead, Prepared By, Date, Revision (letter or number), and Revision Date. Modify these headings as needed.

Identify Failure Modes

A failure mode is defined as the manner in which a component, subsystem, system, process, etc. could potentially fail to meet the design intent. Examples of potential failure modes include:

• Corrosion
• Hydrogen embrittlement
• Electrical Short or Open
• Deformation
• Cracking

A failure mode in one component can serve as the cause of a failure mode in another component. Each failure should be listed in technical terms. Failure modes should be listed for the function of each component or process step. At this point, the failure mode should be identified whether or not the failure is likely to occur.

Describe the effects of those failure modes

For each failure mode identified the engineer should determine what the ultimate effect will be. Examples of failure effects include:

• Injury to the user
• Inoperability of the product or process
• The improper appearance of the product or process
• Odors
• Degraded performance
• Noise

Establish a numerical ranking for the severity of the effect. A common industry standard scale uses 1 to represent no effect and 10 to indicate very severe with failure affecting system operation and safety without warning. The intent of the ranking is to help the analyst determine whether a failure would be a minor nuisance or a catastrophic occurrence to the customer. This enables the engineer to prioritize the failures and address the real big issues first.

Identify Current Controls

Current Controls (design or process) are the mechanisms that prevent the cause of the failure mode from occurring or which detect the failure before it reaches the Customer. Each of these controls should be assessed to determine how well it is expected to identify or detect failure modes. After a new product or process has been in use previously undetected or unidentified failure modes may appear.

Determine the likelihood of Detection. Detection is an assessment of the likelihood that the Current Controls (design and process) will detect the Cause of the Failure Mode or the Failure Mode itself, thus preventing it from reaching the Customer. Based on the Current Controls, consider the likelihood of Detection using the following table for guidance.