Failure Modes and Effects Analysis (FMEA) is a step-by-step approach for identifying all possible failures in a design, a manufacturing or assembly process, or a product or service. It is a common process analysis tool, and can be performed on entire systems, individual process steps or singular pieces of equipment.
In short, process failures are prioritized according to how serious their consequences are, how frequently they occur, and how easily they can be detected. The purpose of the FMEA is to take actions to eliminate or reduce the impact of failures—starting with the highest-priority ones. Let’s piece apart the components of FMEAs, and explore how they can be used to enhance your processes…
FMEA Components
FMEA is used during design to prevent failures. Later it is used for control, before and during ongoing operation of the process. Ideally, FMEA begins during the earliest conceptual stages of design and continues throughout the life of the product or service.
There are many critical components of FMEA. Let’s look at a few definitions:
Failure mode – this is the way (or ways) that a process can break down.
Cause of failure – this is the tangible reason for the failure
Potential effect – this is the consequence of the failure on the rest of process or product
Risk Priority Number (RPN) – this is determined by multiplying Severity, Occurrence and Detection rankings (see example below)
Probability of harm – likelihood harm to equipment or personnel will occur based on Detection and Occurrence rankings
Severity of risk – risk determined by probability of harm and Severity ranking
Action – task assigned to reduce risk associated with failure mode by decreasing severity or occurrence or increasing detectability
After-action review – an assessment of risk after actions are put into place Failure modes and effects analysis also documents current knowledge and actions about the risks of failures, for use in continuous improvement.
The Process
An FMEA can have different foci, depending on when the analysis is performed in the process lifecycle. Design FMEAs are centered on determining causes of failures during the design phase of process implementation so the design can mitigate potential failures from startup. When a process is already running, an FMEA can be used to determine the cause for ongoing and recurring failures on the associated equipment and improve risk management by identifying gaps in preventative maintenance programs or failure detection measures.
Regardless of when an FMEA is completed, it should be a collaborative effort between every function that touches the manufacturing process (e.g., engineering, maintenance, operations).
Once the initial analysis is completed and appropriate actions are completed, the group should reconvene to reevaluate the severity, occurrence and/or detectability of each failure mode. Each FMEA is intended to be a living document that is reviewed or revised on a periodic basis or at least following any major project on a component of the system. This ensures that the potential risk associated with each failure mode is accurately portrayed and new risks are identified as the system changes throughout its lifecycle.
Example FMEA for a Water Storage Tank
As shown below, the overall performance of a water storage tank can be investigated using FMEA. Listed in the first column are components of the tank, such as water hold tank, valves, centrifugal pumps, and nozzles. The next column outlines the potential failure modes, and their potential effects, and probability of harm.
Severity, Occurrence and Detection numbers are entered by the analyst, as well as descriptors for causes of failures, and current controls in place. The criteria for determining these rankings is below:
Severity | | |
Ranking | Term | Qualitative Definition |
1 | Negligible | Failure, even assuming a worst case credible scenario, is highly unlikely to threaten exceedance of daily mass limit even if multiple "like severity" failures occur at other steps. |
2 | Minor | Failure, assuming common scenario (i.e. not worst case), is unlikely to threaten exceedance of the daily mass limit even if multiple "like severity" failures occur at other steps. |
3 | Moderate | Failure, assuming a worst case credible scenario, if combined with multiple "like severity" failures at other steps could approach, but is not expected to exceed, the daily mass limit. |
4 | Major | Failure, assuming common scenario (i.e. not worst case), may lead to exceedance of the daily mass limit but only if "like severity" failures occur at other steps. |
5 | Severe | Failure, assuming common scenario (i.e. not worst case) will lead to exceedance of the daily mass limit without "like severity" failures of other steps. |
Occurrence | | |
Ranking | Term | Qualitative Definition |
1 | Remote | Failure not expected to occur. Team members unaware of any example of the failure in their area/experience. |
2 | Improbable | Failure unlikely but can reasonably be expected to occur at some point. Team members aware of rare examples of the failure across area/site. |
3 | Occasional | Failure expected to occur at irregular or infrequent intervals. Team members aware of occasional examples of failure across the area/site. |
4 | Probable | Failure expected to occur intermittently. Team members are aware of intermittent examples of the failure across area/site. |
5 | Frequent | Failure expected to occur often. Team members are aware of a chronic example of the failure in area/site. |
Detection | | |
Ranking | Term | Qualitative Definition |
1 | Certain | The ability of current controls have been demonstrated to detect a potential failure mode. |
2 | High | Current controls are likely to detect a potential failure mode. |
3 | Moderate | Possible but not certain that current controls will detect a potential failure mode. |
4 | Low | Small likelihood that the current controls will detect a potential failure mode. |
5 | Remote | No known controls available or highly unlikely that the current controls will detect a potential failure mode. |
These rankings can then be used to calculate the RPN so that recommended actions can be prioritized. Additionally, the probability of harm can be determined by assessing values according to the matrix below:
Actions, responsibilities, and timing for completion are all critical components of a well-structured FMEA. It is from these actions that a thorough after-action review can take place. It should be noted that not all failure modes require actions, and all proposed actions need not be completed, if the level of assumed risk is accepted by all stakeholders.
The Benefits of FMEA
Our engineering consultants have worked with pharmaceutical manufacturing clients to introduce and apply FMEA to their processes. Here’s what one client had to say:
We partnered with Process Alliance to work on FMEAs for equipment that was not reaching our desired level of uptime which, at times, caused negative impacts to our production schedules. This partnership has identified multiple maintenance, engineering, and automation gaps on nearly every piece of critical production equipment and plant utility equipment that we have assessed. With the help of Process Alliance’s FMEA process, we have been able to update our preventative maintenance routines as well as launch engineering and automation projects to fix both legacy problems and to prevent potential failure modes before they occur. The partnership with Process Alliance has been a successful endeavor to increase the reliability of assets throughout our facility.
PA is a leader in the GxP space for providing high quality results like these for our clients that are expanding or are looking to optimize their processes by integrating FMEA. To learn more about how our experts can introduce or enhance FMEAs at your organization, email us at pa.info@pa-engineering.com, or visit our website.