Most manufacturing processes are extremely complex, and there are many ways in which things can go wrong. PFMEA is a structured process for identifying risks and defining and prioritizing preventive actions. Manufacturers use it proactively to avoid unplanned machine downtime, maintain consistent levels of quality and prevent accidents.
With downtime costing manufacturers thousands of dollars per hour, PFMEA has become a critical tool for reducing risk. When properly implemented, it supports data-driven maintenance strategies, improves overall equipment effectiveness (OEE) and strengthens overall product quality.
What is PFMEA in manufacturing?
Process Failure Mode and Effects Analysis (PFMEA) is a version of FMEA tailored for use with manufacturing processes, especially in regulated industries such as automotive, aerospace and medical devices. FMEA is a methodology for determining the likelihood and impact of a particular event. Based mainly on expert opinions, it provides a structured method of identifying priorities for improvement, remediation or preventive actions.
Process FMEA in manufacturing supports plant maintenance operations by identifying priorities for servicing and repair. This fits into ISO 9001 as well as quality management systems. To give an example, in many factories, the air compressor is a vital piece of equipment. While the risk of breakdown is probably low, the consequences can be severe. PFMEA could be used to determine the most probable causes of failure and, from there, to develop preventive actions.
How does PFMEA work?
The idea is to identify all potential failure modes for a process, line or piece of equipment. For each mode identified a “Risk Priority Number” (RPN) is calculated. This is the product of values for severity, probability of occurrence, and difficulty of detection before the event has an impact. Typically, these are estimated on a 1-10 scale, with larger numbers signifying greater risk. For example, a potential failure mode for a piece of equipment may receive scores of 9 for severity, 4 for occurrence and 7 for detection difficulty. Multiplying these together gives the mode an overall RPN of 252, which signals a high priority.
Management then tasks teams or functions with developing and executing corrective actions to prevent occurrence of events with the highest RPNs. Many manufacturers today use RPN calculations in conjunction with other metrics, due to the subjectivity of the scoring used for RPN.
PFMEA can be applied to existing, new, or proposed processes and equipment. Where equipment is already in place, data may be available to quantify probabilities of events, and their impact. More often though, the failure mode analysis process is performed before any history exists. In this case, numerical values are estimated by individuals or groups with detailed knowledge of the process.
When to perform PFMEA
Given that the goal of PFMEA is to prevent costly breakdowns or other failures, it should be performed:
- During process design: When determining or developing a new manufacturing process, a PFMA helps identify areas of risk, so appropriate controls and standard operating procedures (SOPs) can be implemented. Adhesive bonding and welding processes are examples where it’s important to establish control over quality-related variables.
- Prior to process startup: Performing a PFMEA at this point can support the maintenance team in developing appropriate preventive maintenance strategies. It may also be required by a customer looking for increased confidence in supply continuity.
- When planning extensive process modifications: Whenever equipment or materials are changed, there is a risk of unintended consequences. Performing a PFMEA ensures any new or changed equipment servicing needs are identified and incorporated into the maintenance schedules.
- During new product introduction: PFMEA can be important when introducing a new product to ensure all the processes will perform as smoothly as possible.
- Before implementing predictive maintenance programs: Using PFMEA, maintenance teams can determine which failure modes will be the highest priority for prevention. This enables them to make better informed decisions about prioritizing predictive maintenance tasks.
- After recurring micro-stoppages impact OEE: Unplanned stoppages, even brief ones, are often early indicators of larger reliability issues that can lead to significant downtime if left unaddressed. PFMEA can be important for rating how severe these issues may be and whether they warrant proactive interventions.
- During supply chain disruptions or material substitutions: Using PFMEA during a change in supply chain dependability helps teams understand what those changes could mean for downtime and find alternatives that can prevent it.
Other times, a PFMEA can be useful as part of an investigation into quality problems, when developing a preventive maintenance strategy, and in response to an accident. In these situations, it’s common to supplement PFMEA with the “Five Whys” technique to determine root causes.
How to conduct a PFMEA
Preliminary steps prior to initiating a PFMEA in manufacturing are to define the target area, the goals or objectives, and to form a team. The team should be made of people familiar with the product or products and the manufacturing process. It’s also useful to include a representative from maintenance who is familiar with the machinery or equipment in the target area.
Once the team has been formed and briefed, it’s time to execute the following failure mode and effects analysis steps:
1. Conduct a detailed process review: This is usually done in the form of a process flow diagram showing the process inputs (such as raw materials) and outputs (such as the finished product). It’s also a good idea to include elements such as an equipment hierarchy, maintenance histories, process capability data, and a SIPOC diagram reference. This gives all the team members a common understanding of the process under review.
2. Identify failure modes: This can take the form of a brainstorming exercise with team members asking questions and offering ideas.
An initial briefing at the outset is often helpful in reminding the team of failure modes to consider:
- Complete breakdown: Where the process fails or is not performed.
- Partial breakdown: Part of the equipment or process isn’t working as it should, but can be made to achieve the required result. For example, the heater in a drying oven may not be working at 100%, but an additional unit can be brought in on a temporary basis.
- Intermittent or microstoppages: Often self-correcting, such as a fuse that trips and resets, this type of failure is disruptive and can harm product quality.
- Reduced performance: Where a machine is run at a lower speed because full speed operation causes quality losses or other problems.
- Supply disruptions: Non-availability of raw material is the most obvious example, but this could also include what happens when a manufacturing or maintenance team member with unique skills doesn’t show up for work.
- Human error: Understanding the conditions that lead to operators making mistakes with the equipment can be important for preventing failures in the future.
- Software/automation failure: Glitches, bugs or unsuccessful updates can cause problems that lead to equipment breaking down or malfunctioning.
- Environmental factors: Exposure to excessive heat, cold, humidity, smoke and other environmental hazards also has a tendency to cause failure states.
3. Identify the effects of each failure: Will it bring production to a halt? Could it increase product variability? Might it require additional labor? It’s important to have these risk assessments performed by a cross-functional team to ensure there is no bias in the scoring.
4. Assign a ranking to the severity of each failure mode: Typically done on a 1-10 scale, with 1 the least impactful.
5. Assign a ranking for probability of occurrence: Again, use a 1–10 scale. Remember to use historical data as a guide, if any is available. Scoring criteria tables should be standardized to prevent confusion and inconsistencies.
6. Assign detection difficulty rankings: This refers to the probability of detecting, and therefore being able to act on, the failure. A complete stoppage of a production is probably easy to see whereas insufficient surface cleaning prior to bonding may not be detectable. Here, the former gets a detection ranking of 1 while the latter might be considered a 10. Overall, adding condition monitoring sensors may be able to improve the odds of catching certain failures.
7. Calculate the RPN: Multiply the severity, occurrence and detection scores, and rank failure modes accordingly. If a particular failure has an extremely high severity score, it should be automatically prioritized regardless of how it scores in the other areas.
8. Develop an action plan: The RPN ranking will show which faults pose the highest risk to production. Management should develop plans to mitigate these failure modes. These often include:
- Writing SOPs to reduce variability in how work is done
- Implementing measurement and alarm systems, for example, to measure concentrations and flows of cleaning agents
- Developing preventive maintenance schedules
- Implementing condition monitoring systems
- Root cause analysis for high RPN failures
- Installing predictive monitoring systems
- Redesigning workflow or ergonomics
- Supplier quality audits
- Redundancy planning for critical equipment
- Spare parts optimization strategies
Following a Plan-Do-Check-Act philosophy, the PFMEA should be repeated once the control plan has been fully implemented. Plans should spell out clearly who is accountable for each action, and follow-ups should be baked into the PFMEA process.
Benefits of PFMEA
While a thorough PFMEA takes time to plan and requires considerable resources to carry out and follow up on, it helps a business avoid unexpected costs and disruption. More specifically, the benefits of a PFMEA include:
- Prevents equipment and potential process failures: This avoids disruptions to delivery schedules, quality problems, and the associated additional labor and material costs.
- Provides a basis for process control planning: Only when risks are identified is it possible to develop procedures to guard against them.
- Reduced customer risk: Products with hidden defects, such as poor-quality welds or faulty adhesive application, can fail in service. PFMEA identifies these risks and helps define preventive measures.
- Increased safety: A thorough PFMEA will cover accident risks, with the action plan identifying process steps needed to improve worker safety.
- Lower costs: Reduced accidents and warranty claims, fewer breakdowns and higher yields all lead to lower costs and higher margins.
- Better asset lifecycle management: These efforts help prevent breakdowns that can impact the lifespan of assets, keeping them in service longer.
- More cross-functional collaboration: PFMEA helps build stronger connections between teams, making it easier for them to collaborate on maintenance and other functions.
- Digital transformation: Implementing PFMEA is important for supporting a facility’s digital transformation as more automation works its way into critical processes.
- Less insurance and liability exposure: A well-functioning facility with less downtime means a safer working environment for all, which leads to lower risk of liability.
- Greater consumer confidence: With more uptime, overall quality improves and helps build trust among consumers in a brand.
Industrial asset management with ATS
Manufacturers use PFMEA as a proactive process for identifying risks and defining and prioritizing preventive actions. It guides maintenance planners in reducing unplanned machine downtime, helps maintain consistent levels of quality, and prevents accidents. It helps support OEE improvements, capacity expansion and continuous improvement efforts.
As leaders in all aspects of industrial maintenance, ATS understands the value of a well-organized PFMEA. We help manufacturers increase maintenance effectiveness, driving waste out and costs down while increasing OEE and capacity. Contact us to learn more.
