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Failure Mode and Effects Analysis (FMEA)

Introduction

The failure mode and effects analysis (FMEA) is a professional level hazard ID tool specifically designed to detect and evaluate the impact due to the failure of various system components. Most FMEAs have traditionally been directed at the failure of parts in mechanical system, but the tool is suitable for analyzing the failure of any component of any type of system. A brief example of FMEA illustrating this purpose is the analysis of the impact of the failure of the communications component (radio, landline, computer, etc.) of a system on the overall mission. The focus of the FMEA is on how such a failure could occur (failure mode) and the mission impact of such a failure (effects).

FMEA is a systematic method that identifies and prevents product and process problems before they occur. FMEA is a quality improvement tool that does not require complicated statistics for success. FMEAs do take time and people resources because by nature they are team based.

The first FMEAs were done in the aerospace industry in the mid-1960’s and only recently gained popularity in health care. Engineering has developed computerized tools that assist in assessing risk in various systems. The results in industry are reductions and elimination of the need for after-the-fact corrective action. FMEA also reduces costs.

Applicability

FMEA is generally regarded as a professional tool but with the assistance of the FMEA job aid, most operational personnel can use the tool effectively. The FMEA can be thought of as a more formal and detailed “What if” analysis. It is an especially useful tool in contingency planning where it is used to evaluate the impact of various possible failures (contingencies). The FMEA can be used in place of the what if analysis when greater detail is needed or it can be used to examine the impact of hazards developed using the what if tool in much greater detail.

All areas affected by the process being examined should be represented on the FMEA team. Generally, 4 – 6 representatives is best, however, the number of areas affected by the process should dictate the size of the team. Management should appoint a team leader. Team leaders are responsible for setting up and facilitating meetings, assuring the team has adequate resources to accomplish the goal and to make certain the team progresses. Team leaders are facilitators, not final decision makers. A secretary should be appointed to take minutes and maintain FMEA records.

The FMEA team needs clearly defined scope and boundaries within which to work. The following items should be considered and outlined for the team:

FMEA Steps

The objective of FMEA is to look for all the ways a process or product can fail. Ways in which a process can fail are called failure modes. Each failure mode has a potential effect and each potential effect has a relative risk associated with it. The relative risk of failure and its effects is determined by three factors:

Each factor is given a score of 1 – 10 (1 = low, 10 = high). A risk priority number (RPN) is determined by multiplying the rating for the three factors (severity x frequency x detection). The risk priority number is used to rank the need for corrective actions to eliminate or reduce potential failure modes. Failure modes with the highest RPNs should be attended to first. Once corrective actions have been taken, a new PRN is determined by reevaluating the severity, frequency and detection ratings. The new RPN is called the resulting RPN. Improvement and corrective actions must continue until the resulting PRN is at an acceptable level for all potential failure modes.

Step 1 – Flowchart the Process.

Flowcharting the process ensures that all members of the team have the same understanding of the process to be examined. It may be helpful for team members to watch the process in action.

Step 2 – Brainstorm Potential Failure Modes

Team members should brainstorm possible cases of failure and focus on the following elements: people, methods, equipment, materials and environment. All potential failure modes should be recorded on the FMEA worksheet.

Step 3 – Brainstorm Potential Effects of Each Failure Mode

The team should review each failure modes and identify potential effects of the failure, should it occur. There may be several effects for each failure mode.

Step 4 – Assign a Severity Rating for Each Effect

Using the 1 – 10 scale (1= low, 10=high), assign an estimation of the severity of effects if a failure did occur. A severity rating should be given for each effect.

Step 5 - Assign a Frequency Rating

The best way to determine the frequency rating is to use actual data, if available. Use incident reports or logs, etc. In the absence of data, the team must estimate the likelihood of failure. Use the 1 – 10 scale (1= low, 10=high).

Step 6 – Assign Severity, Occurrence and Detection Ratings

The detection rating looks at the likelihood of detection of a failure or its effects. Start by looking at current controls that may detect a failure the effect of a failure. If there are no current controls in place, then the detection rate will be low and the item will receive a high rating.

Step 7 – Calculate the Risk Priority Number (RPN) for Each Failure Mode

Multiply the severity rating times the occurrence rating times the detection rating for all items. The total risk priority number should be calculated by adding all of the RPNs.

Step 8 – Prioritize the Failure Modes for Action

Rank failure modes in order from the highest RPN number to the smallest. The team must now decide which items to work on.

Step 9 – Take Action to Eliminate or Reduce High-Risk Failure Modes

Identify and implement actions to eliminate or reduce the high-risk failure modes. Use an organized problem solving process such as Rapid Cycle Quality Improvement and the Plan, Do, Study, Act process.

Step 10 – Calculate the Resulting RPN as the Failure Modes are Reduced.

Once Action has been taken to improve a process, new severity, frequency and detection rating should be determined and the resulting PRN calculated. A significant reduction in the RPN should be noted. If not, the actions taken to improve the process were not sufficient to reduce the severity, frequency and detection rating and additional actions should be taken.

The FMEA Worksheet

The FMEA Process should be documented using a FMEA worksheet. The worksheet captures all the important information about the process and can serve as a communication tool. Each FMEA process should be assigned a number. The FMEA is normally accomplished using a worksheet similar to the one illustrated below. As noted on the sample worksheet, a specific component of the system to be analyzed is identified. Several components can be analyzed. For example, a rotating part might freeze up, explode, breakup, slow down, or even reverse direction. Each of these failure modes may have differing impacts on connected components and the overall system. The worksheet then calls for an assessment of probability.

Component Description List all potential Failure Modes Potential effect Frequency Severity Detection Criticality Index RPN