PFMEA | What is PFMEA (Process Failure Mode and Effects Analysis)?

PFMEA | Process FMEA | Process Failure Mode and Effects Analysis

What is PFMEA or Process FMEA?

→ PFMEA is a Process Failure Mode Effects Analysis.
→ It is a structured analytical tool used by an organization, business unit or cross-functional team to identify and evaluate the potential failures of a process.
Process Failure Mode Effects Analysis helps us to establish the impact of the failure.
→ PFMEA (Potential Failure Mode Effects Analysis) also provides a framework for identifying & prioritize the action for the items having a risk factor for minimizing the risk.
→ It is a live document that should be updated through the process of production and maintained it through the life cycle of the product.
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➤ PFMEA or Process FMEA Report:

→ The format of the PFMEA (Process Failure Mode and Effects Analysis) Report is mentioned below:
PFMEA Report

👉 Download: PFMEA Excel Template and Severity Occurrence & Detection Table

10 Easy Steps for making PFMEA:

→ There are 10 Simple steps for making Process Failure Mode and Effects Analysis Report is mentioned below:
  1. Review the process & It's Requirement
  2. Brainstorm potential failure modes
  3. List the potential effects of failure
  4. Assign Severity rankings
  5. Assign Occurrence rankings
  6. Assign Detection rankings
  7. Calculate the RPN
  8. Develop an action plan
  9. Take Action
  10. Calculate the resulting RPN

10 Steps for PFMEA

➤ Process FMEA Step 1 | Review the process & It's Requirement

PFMEA Step 1  Review the process & It's Requirement

→ Use a process flowchart to identify each process component in Process Failure Mode and Effects Analysis.
→ List each process component in the FMEA table.

➥ Review the process components and the intended function

→ Use of a detailed flowchart of the process
→ The detailed flowchart is a good starting point for reviewing the process.
→ With the process flowchart in hand, the PFMEA (Process Failure Mode and Effects Analysis) team members should familiarize themselves with the process by physically walking through the process.
→ This is the time to assure everyone on the team understands the basic process flow and the workings of the process components.

➥ There are several reasons for reviewing the process

→ The first reason is reviewing the process helps us to assure that all team members are familiar with the process.
→ A second reason for reviewing the process is to identify each of the main components of the process.
→ The third reason for reviewing the process is to assure that you are studying all components of the process with the Process FMEA.

➤ Process FMEA Step 2 | Brainstorm potential failure modes

PFMEA Step 2 | Brainstorm potential failure modes

→ Review existing documentation and data for hints about all the possible ways that the component can fail.
→ Consider the potential failure modes for each component and its corresponding function in this step of PFMEA.
→ A potential failure mode represents any manner in which the component or process step could fail to perform its intended function or functions.
→ Using the list of components and related functions generated in Step 1, as a team, brainstorm the potential failure modes for each function.
→ Don’t take shortcuts here; this is the time to be thorough.
→ Prepare for the brainstorming session.
→ Before you finish the brainstorming session, review the documentation for possible causes of potential failure modes.

➤ Process FMEA Step 3 | List potential effects of failure

PFMEA Step 3 | List potential effects of failure

→ There may be more than one effect of failure for each failure in the 3rd step of PFMEA.

➥ Determine the effects related to each failure mode.

→ Some failures will have an effect on the customers and others on the environment, the facility, and even the process itself.
→ The effect should be stated in meaningful terms.
→ If the effects are defined in general terms, it will be difficult to identify (and reduce) true potential risks.

➤ Process FMEA Step 4 | Assign Severity rankings

PFMEA Step 4 | Assign Severity rankings

→ Severity rankings are based on the severity of the consequences of failure in the 4th step of PFMEA (Process Failure Mode and Effects Analysis).

➥ Assign a severity ranking to each effect that has been identified.
→ The severity ranking is an estimate of how serious an effect would be should it occur.
→ To determine the severity, consider the impact the effect would have on the customer, on downstream operations, or on the employees operating the process.

➥The severity ranking is based on a relative scale ranging from 1 to 10.
→ A “10” means the effect has a dangerously high severity leading to a hazard without warning.
→ Conversely, a severity ranking of “1” means the severity is extremely low.

➤ Process FMEA Step 5 | Assign Occurrence rankings

PFMEA Step 5 | Assign Occurrence rankings

→ Occurrence rankings are based on how frequently the cause of the failure is likely to occur in the 5th step of PFMEA.
→ Next, consider the potential cause or failure mechanism for each failure mode; then assign an occurrence ranking to each of those causes or failure mechanisms.
➦ If we know the cause, we can better identify how frequently a specific mode of failure will occur. How do you find the root cause?
 One of the easiest to use is the 5-Whys technique.
 Once the cause is known, capture data on the frequency of causes. 
 Sources of data may be scrap and rework reports, customer complaints, and equipment maintenance records.
 There are many Problem-finding and Problem-solving methodologies.

➥ The occurrence ranking scale:

 Likes severity ranking, It is on a relative scale from 1 to 10.
 An occurrence ranking of “10” means the failure mode occurrence is very high and happens all of the time.
 “1” means the probability of occurrence is very low.

➤ Process FMEA Step 6 | Assign Detection rankings

PFMEA Step 6 | Assign Detection rankings

→ Based on the chances the failure will be detected prior to the customer finding it in the 6th step of Process Failure Mode and Effects Analysis.

➥ The Detection ranking scale:

→ A Detection ranking of “1” means the chance of detecting a failure is certain.
→ Conversely, a “10” means there is absolute certainty of non-detection.
→ This basically means that there are no controls in place to prevent or detect.

➤ Process FMEA Step 7 | Calculate the RPN

PFMEA Step 7 | Calculate the RPN

➥ Calculation of RPN (Risk Priority Number)

→ RPN = Severity X Occurrence X Detection.
→ The RPN is the Risk Priority Number.
→ The RPN gives us a relative risk ranking.
→ The higher the RPN, the higher the potential risk.
→ The RPN is calculated by multiplying the three rankings together.
→ Multiply the Severity ranking times, Occurrence ranking times and Detection ranking.
→ Calculate the RPN for each failure mode and effect.

⟹ Note:
→ The RPN gives us an excellent tool to prioritize focused improvement efforts.

➤ Process FMEA Step 8 | Develop an action plan

PFMEA Step 8 | Develop an action plan

→ Define who will do what by when in the 8th step of PFMEA.

➥ Action Plan Development for High RPN value

→ The RPN can be reduced by lowering any of the three rankings (severity, occurrence, or detection) individually or in combination with one another.
→ A reduction in the Severity ranking for a Process Failure Mode and Effects Analysis is often the most difficult.
→ The severity usually requires a physical modification to the process equipment or layout.
→ Reduction in the Occurrence ranking is accomplished by removing or controlling the potential causes.
→ Mistake-proofing tools are often used to reduce the frequency of occurrence.
→ A reduction in the Detection ranking can be accomplished by improving the process controls in place.
→ Adding process fail-safe shut-downs, alarm signals (sensors or SPC), and validation practices including work instructions, set-up procedures, calibration programs, and preventative maintenance is all detection ranking improvement approaches.

➥ What is considered an acceptable RPN?

→ The answer to that question depends on the organization.
→ For example, an organization may decide any RPN above a maximum target of 160 presents an unacceptable risk and must be reduced.
→ If so, then an action plan identifying who will do what by when is needed.
→ There are many tools to aid the PFMEA (Potential Failure Mode Effects Analysis) team in reducing the relative risk of failure modes requiring action.

➥ Powerful tools for reducing RPN number:

→ Mistake-Proofing (Poka Yoke) - "A Techniques that can make it impossible for a mistake to occur, reducing the Occurrence ranking to 1. Especially important when the Severity ranking is 10.
→ Statistical Process Control (SPC) - "A statistical tool that helps define the output of process to determine the capability of the process against the specification and then to maintain control of the process in the future."
 Design of Experiments (DOE) - "A family of powerful statistical improvement techniques that can identify the most critical variables in a process and the optimal settings for these variables."

➤ Process FMEA Step 9 | Take action

PFMEA Step 9 | Take action

➥ Implement the improvements identified by your PFMEA team in the 9th step:

→ The Action Plan outlines what steps are needed to implement the solution, who will do them, and when they will be completed.
→ A simple solution will only need a Simple Action Plan
→ While a complex solution needs more thorough planning and documentation.
→ Sometimes Project management tools such as PERT Charts and Gantt Charts will be needed to keep the Action Plan on track.
→ Responsibilities and target completion dates for specific actions to be taken are identified.

➤ Process FMEA Step 10 | Calculate the resulting RPN

PFMEA Step 10 | Calculate the resulting RPN

➦ Re-evaluate each of the potential failures once improvements have been made and determine the impact of the improvements.
→ This step in a Process Failure Mode and Effects Analysis confirms the action plan had the desired results by calculating the resulting RPN.
→ To recalculate the RPN, and reassess the severity, occurrence, and detection ranking for the failure modes after the action plan has been completed.

Benefits of Process FMEA:

 Process FMEA identifies potential failure modes during a new product or process setup.
→ PFMEA assesses the potential customer effects of the failures.
 The Process FMEA identifies potential manufacturing and/or assembly process causes.
 It identifies significant process variables to focus controls for the occurrence reduction and detection of failure conditions.
 Process FMEA develops a list of potential failure modes ranked according to their effect on the customer.
 We can set a priority for corrective and preventive action for the potential failure modes with the help of PFMEA.

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