Q51. FMEA is one of the popular approaches used in the Six Sigma World. What are the limitations of FMEA as a method for Risk Assessment? 

 

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Failure Modes and Effects Analysis FMEA

It is a technique using which we can study all plausible problems  in a process,   the potential/probable impact of each problem and what is the action to be taken to counter with the problem.  Because, the technique is used for capturing potential problems (hence could be risks) and provides a probable action to counter those problems/risks, the technique becomes a good risk assessment tool.  But this technique has its own limitation as well. Let us take a deep dive on this.

 

Types of FMEA

There are 4 types of FMEA viz..,. System FMEA, Design FMEA, Process FMEA, Equipment FMEA

System FMEA:  Analyses systems and subsystems in the earlier part of concept and in design stages and thereby focusing on probable failure modes happening due to design.

 

Design FMEA:  Analyses failure modes in products before they getting released to production.

 

Process FMEA:  Analyses failure modes in manufacturing and transactional processes.

 

Equipment FMEA:  Analyses failure modes in the equipments used in a process.

 

How does FMEA work

Steps associated with FMEA,

1.       Assign a FMEA number

2.       Provide a title to your process

3.       Identify the team responsible for this process

4.       Identify the  member who will prepare the FMEA

5.       Enter the product name of the customer

6.       Assign FMEA Key date and Origination date

7.       Provide the list of core team members who are involved in this activity

8.       List the process function steps which serve as the inputs for the process

9.       List potential failure for modes, effects, causes separately

10.   Assign detection level to each mode

11.   Assign severity to each effect

12.   Assign occurrence level to each cause

13.   List out the current process controls for prevention/detection of failure modes.

14.   Now calculate the Risk Priority Number (RPN) which is nothing but the product of the values in each of the columns - severity, occurrence and detection  

15.   Now , Prioritize the order of the data entered as per the RPN to have a look as which is to be addressed first , by sorting of data with the highest RPN based entry in the top descending towards with the lowest RPN based entry on the bottom

16.   Specify the actions that is recommended

17.   Assign owners for the actions specified and assign the actions to those relevant owners

18.    Now Recalculate the Risk Priority Number (RPN) and then again sort out the (entire) data based on RPN.

 

Limitations of FMEA

 

1.        This is a tool/technique to be managed by the FMEA owner or his/her backup. Not an ideal tool for everyone in a team to maintain this. So there is dependency created on individuals while maintaining the sheet, even if this is the correct and industry practiced way.

2.       Enough exposure/experience required to meddle with this technique/tool as this has considerable amount of fields and you need to ensure that RPN is correctly filled when the problem exists (for the first time) and then for the second time, after an action is taken. This comes out of experience/knowledge gained.  So only Subject Matter Expert (SME) can own or handle this.  This is not the case, in many other risk assessment proprietary tools found in many organisations (especially in IT service sectors) where risk is assessed using probability and impact which are calculated bit differently than what is done through this technique and where team contribution is directly involved with each one of the members being a SME for his/her own activity.  Finally risk owner,  collates the risks obtained and then overall risk is provided to all stakeholders

3.       This provides a living document and hence this needs constant update as and when the FMEA owner receives from his/her team or foresees a problem. This is quite cumbersome to do if there is so much risks and if the owner needs to do frequently as there are too many columns (fields) to address and it would be taxing , however a person is experienced and lot of scrutiny needs to happen on the data to ensure everything is correct and agreed by key stakeholders as well.

 

Conclusion:

Irrespective of its limitations, this tool or technique, if used properly, can be a great one to work or use with. It will make a team to think about its process in a rationalised way. This tool helps in driving a systematic record keeping of the process and can drive change through priorities. A team following this would be constantly improving as well - both knowledge wise and process wise.

 

FMEA :- Failure More Effect Analysis.

 

Failure Mode and Effects Analysis (FMEA) is a structured approach to discovering potential failures and their effects that may exist within the system/process/ product/service.

We can break down FMEA in two parts

FM (Failure modes:-The ways in which the system can fail.)

 

In this all the possible failure modes are defined.

EA(effect analysis:-  Effects are ways that listed failures can result in waste, rework, deficient product reaching the customer)

 

In this we analyze the effect/consequences of those failure modes.

It is essential that all the components are reviewed during the analysis.

With FMEA we can identify, prioritize and limit these failure modes. 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 failures, starting with the highest-RPN.

There are mainly two types of FMEA

1.      Design FMEA (DFMEA)

In DFMEA, analysis is done on basic properties of a product, like material, geometry, etc. Ideally DFMEA is done for products before they reach production

2.      Process FMEA (PFMEA)

PFMEA is done for analysis of manufacturing and assembly processes

In PFMEA, analysis is done on ways in which product quality will affect based on online processes. Like Process parameters, machines, Human errors, etc.

Steps for FMEA

 

1. Form FMEA Team.
2. Identify process steps.
3. Identify the potential failure modes for each process step.
4. Identify potential effect of failure and rate their severity.
5. Identify current control and rate the detection.
6. Identify probability of occurrence, severity and probability of detection.
7. Calculate RPN( Risk Priority Number) and prioritize.
8. Identify recommended actions and follow up.

 

Below is the template that can be used for process FMEA

 

 

 

Limitations of FMEA

 

1.     Entire process is depending on the knowledge and skill level of team members.

2.     FMEA analysis takes lot of time and effort, team has to be very cautious about defining the scope. Going too deep will make the analysis never ending.

3.     A team member who is having biases can manipulate RPN no. Making a small problem bigger and vice versa.

4.     FMEA is not a static model. For successful risk management, the FMEA should be regularly updated as new potential failure modes are identified and corresponding control plans are developed.

5.     It is an assessment tool, not one that is designed to eliminate problems. It will yield the best results when supplemented with other project management tools to see the control plans through.

6.     FMEA often has repeated information

7.     FMEA works best as a bottom up tool and fails to identify all the failure modes if used for a top down analysis

8.     FMEA does not provide any assessment or discover complex failures involving combination of failures

Primary limitation of FMEA as risk assessment method is subjectivity involved in assessing severity, occurrence and detectability. Though various industries have established the criteria to rate these parameters to arrive at Risk Priority Number, while the assessment is done for these parameter its largely dependent on the experience and perception of the assessor which would introduce subjectivity in to this assessment. Also while potential failure modes are assessed this methodology does not provide clear guidance to make sure that all possible failure modes are explored. It will again be dependent on the expert to assess all possible failure modes. Also this tool does not help expose potential future failure, apart from those that can be anticipated based on expert experience. FMEA also do not draw boundary in terms of scope of exercise, so they is possibility of too much information gathered and directionless to address all failure modes. Also other area in which FMEA can be misused is not having regular refinement of the FMEA would make it disconnected from current reality which is changing always.

Speaking of limitations of using an FMEA as a method of Risk Assessment :

1) Some possible modes of Failure may be difficult to predict : Process Step failure is easy to visualize. However, the several ways in which  Failure can come knocking on the door may not be that easy.

2) The Risk Priority Number Calculation : The assignment of value  [to Severity/ Frequency of Occurrence & ease of detection of failure ] is subjective and can be prone to error.

3) The Solution List : The corrective steps that need to be taken in case of a failure in most cases are visualized to best ability. However, in real scenario, actualizing the recommended steps in case of a Failure may not be that easy.

Overall, FMEA helps in figuring out what needs to be done in the eventuality of an anticipated process step failure or a breakdown. It's ability to ensure a speedy recovery to Normal State can only be tested when anticipated Failure happens. In case of an unplanned kind of Failure the situation can be worse.

FMEA is ideally referred to as “Potential Failure Mode Effect Analysis”. No doubt it is a very popular tool, when used the way it is intended, will give its benefits. It is important to know what to expect out of this tool.

 

One of the common human behavior is to refrain from thinking and talking negative. There is a belief that talking and thinking positive always will motivate our mind and we will be more associated with positivity and positive results. However, in the case of FMEA exercise, a team is expected to think about ‘failure modes’ that could potentially occur – be it a Design FMEA or Process FMEA. The idea is to pre-think about such likely failures, attach a severity, based on the impact to customer or the organization, should such a failure occur, assess the probability of such an occurrence and ability of current controls to detect, in case it occurs. The exercise provides a method of quantifying the influence of all these 3 factors, Severity, Occurrence and Detection in the form of RPN (Risk Priority Number). Having done the exercise with the best set of people, we will get a priority for working on actions to mitigate the risk due to the Failure Modes.

 

Let’s examine the limitations that the FMEA exercise

 

1.     Effective only if team has right experience:

Since it is the potential failure modes that need to be identified, it is important that the team members have good grasp about the product expectations in case of DFMEA, and of the Process details in case of PFMEA. Sometimes the best of the members may not have adequate fore-thought about the failure modes, and chances of missing out certain failure modes is a risk. We never know what we did not know!

 

2.     Perception about severity:

As part of FMEA, there are guidelines to rank the severity. However, the severity is the impact to the customer. For instance we might rank a failure mode such as color fading as one with low severity as per definition, since it would have no bearing on the functioning or safety of a consumer durable, but it could form such a poor impression for the customer and could be a major factor to lose business. Similarly a minor leak in a water heater may not get classified as a failure mode of high severity, but if the customer places the appliance over an electrical point and the minor leak can result in sparking off a fire, it could be a gross error.

 

3.     Actions seldom bring down severity rating

Most of the actions based on FMEA address the occurrence and detection. The severity of the failure if occurred, continues to remain same and is seldom addressed.

 

4.     Occurrence estimation:

Often the estimation of occurrence would be done based on the historical experience of the capability of similar processes. Many a time, there would not be adequate record for the occurrence data. There is always a risk that the occurrence for a particular failure mode can spike up due to special causes. In a mass production, even one day’s spike for a low severity failure mode can be very disastrous in terms of heavy rework, product recalls, or warranty expenses.

 

5.     FMEA by itself will not mitigate risks

FMEA exercise will identify and prioritize the risks. However other efforts are required to identity the remedial actions to overcome these risks. Otherwise it remains as an exercise without impacting a change.

 

6.     Striking the right balance on details

The FMEA exercise is driven by the extent of Design or Process details that is fed in. This will set depth of the rest of the exercise. Inadequate level of detailing can result in missing out important failure modes, and too much level of detailing can digress the exercise. It is important to strike the optimum balance on the level of detailing done.

 

7.     Control plan derivation

For many of the controls and containment items identified, the FMEA has to be followed by a good control plan. The sequence of drawing synergy from FMEA and Control plan has been well addressed in the TS 16949 QMS standard. As we know the control plans are tools that need to be administered with good amount of discipline, otherwise the findings of FMEA will not bear fruit.

 

8.     FMEA has to be a living document

Once prepared, FMEA document has to be maintained and subject to updation as and when new Failure Modes are identified. All lessons learned need to get transferred as part of the preventive actions for new products / processes. Otherwise, we will only end up repeating the same efforts.

 

The above limitations, however do not undermine the power of this team based tool. if the exercise is facilitated by a good professional, along with steps that overcome the said limitations, it will certainly prove as an effective 'preventive' tool.

FMEA stands for Failure Mode and Effects Analysis 

 

Limitations of FMEA:

 

1. Ratings might mislead or even Biased :- if all ratings are given in highest[close to highest] possible values, but the actual fault might reside there only. In the scenario it will be impossible to identify the fault.

 

2. It is always not possible to find out 'what if' in big companies there might have lakhs of discrete components where we might loose the trivial issues.

 

3. As possible list of failure mode is ever increasing and its only a list not a corrective process to implement.

 

4. It needs experienced and knowledgeable members to fulfill its goal

 

5. The more late we start FMEA in the design phase the more weaker it becomes.

 

6. It requires a detailed analysis and focused to fulfill it's goal or will miss many failure modes.

 

7. It should have a proper fault detection techniques/processes 

 

8. It should be a top-down tool, not bottom-up a tool or else it will miss most of the important issues.

 

9. Use of RPN can limit its efficiency.

 

10. FMEA worksheet's complexity.

 

11. Huge entries in FMEA worksheet

 

12.  Improper prioritization of risks 

 

13. It needs regular updation, as it is not a static model

 

14. Costing 

 

15. Dependency on Human diagnosis and management factors.   

 

 

FMEA is a very important tool to identify risk,  it has a lot of advantages and benefits.  It identifies important hazards in a system. FMEA is used a top down and bottom up approach. 

FMEA calalculate RPN number stands for risk priority number which is calculated by multiplication of three factors named severity, occurrence,  and detection.  Each one assigned a value  between one to ten. Major limitation of fmea is this multiplication  because this ranking may result in ranking reversal.  Possibilities are there a less failure mode gets a more RPN and on the other hand a more failure mode gets a lower RPN number. So it is very difficult to prioritise the all on which we need to work.  Because highest RPN number will give you lower failure mode on the other ha d we are ignoring which is having less RPN but potential of major failure mode. The reason behind this because we are giving ranking with the ordinal scales that is from one to ten which is normal scale. The ordinal ranking only tell us that which ranking is more or less worse but  not tell by how much.  So this is major limitation of fmea although various manipulation are there to resolve this. 

 

 

 

 

 

 

FMEA is highly effective for risk analysis but this technique has few limitations.

 

Rating of severity and occurrence are subjective and depends on users. Therefore analysis from different sources for same process may give different risk priority number.

 

External influences that causes safety issue are often overlooked. 

 

Identification of failure mode is discussion based brainstorming activity. Any information unnoticed may cause failure. 

 

 

 

Q51. FMEA is one of the popular approaches used in the Six Sigma World. What are the limitations of FMEA as a method for Risk Assessment? 

 

FMEA stands for Failure Mode and effect analysis.

 

We must have seen many products failing after its delivery to the customer. In such cases, the customer and the manufacturer sit and understand the issue what went wrong. FMEA is a methodology which allows the company or manufacturer to identify the potential failures during design phase itself and also its impact on the product been studied. This will help us in creating a actionable which can reduce such errors or failures and protect the customer.

Errors or failures are very expensive. Hence all potential failures and its impact should be anticipated during the design stage itself.

 

It is a structured step by step approach to identify the possible ways in which a product or precess fail, estimate its risk associated with the causes, prioritize the actions that has to be taken to reduce the risks identified and create a  control plan.

 

Definitions:

Failure modes – Are the ways in which the product or process can fail.

Effects – Are the ways that the failures modes results in errors, defects, waste or even a fatal consequences to the customer.

Failure mode and effect analysis is a step by step approach to identify, prioritize and control the failures occurring. It will help you by answering these questions… how serious the failures are, how easily it is detected, how frequently it is occurring, etc.

 

Benefits of FMEA –

1.      It helps identify the how likely the process fails..

2.      It helps improve the internal and external customer satisfaction scores

3.      It helps to identify the rare potential failures as well in the process and risk mitigation plan is also created against it.

4.      It is a step by step approach helps to identify all the failures in the process.

 

Why FMEA is required –

1.      To satisfy the internal and external customer

2.      To mitigate the risks identified.

3.      Lower cost solutions to the step step problem analysis.

4.      To improve the process

5.      To prevent the errors before it occurs

6.       To reduce possible wastes identified through potential failures.

7.      As a tribal knowledge, standard work utilized

 

When to conduct the FMEA –

1.      Early in the design phase of the product or process

2.      As part of the process improvement phase

3.      When the process or product requires some change

4.      When trying to replicate the other designs in other or new applications

5.      When the customer requests for FMEA before starting out a business.

6.      When the errors and risks are frequently identified

 

Types of FMEA –

1.      Process FMEA – used to analyses the manufacturing and assembly processes after they are implemented. it explores the product malfunctions, reduced product life due to failure and safety / regulatory concerns are gathered from material properties, geometry, tolerances, noises and interface troubles.

 

2.      Design FMEA – analyses the product design before its manufacturing could happen, as part of design phase it is done early in design phase. identifies failures that impact quality, reliability and customer satisfaction. It is derived from human factors such as 5M’s – Materials, methods, machines, man power, mother nature and measurement errors.

 

FMEA Procedure –

1.      Identify the inputs through some of tools like cause and effect diagram or process map and determine in what ways the inputs can go wrong.

2.      Determine the effects for every potential failures or risks (Severity)

3.      Identify the potentials causes for all failure modes(Occurrence)

4.      List current controls for each cause.(Detection)

5.      Calculate RPN (severity * occurrence * Detection)

6.      Develop actions and implement it.

7.      Assign the predicted severity, occurrence and detection levels, calculate RPN and compare the RPNS before and after the process improvements.

 

FMEA inputs & Outputs –

 

 

 

 Severity, Occurrence and detection:

1. Severity – how important it is to the customer and it is rated in 1- 10 rating scale.

             1=  Not severe and 10 = Very severe

2.  Occurrence – how frequent the failures occurs with given cause as it is collected from past history. And ratings are given accordingly in 1-10 rating scale

              1=  Not likely and 10 = Most likely

3. Detection – ability of detecting the errors in the given controls and then to prevent the error. It is also rated in 1-10 rating scale.

               1= Easy to detect and 10 = most difficult to detect

 

RPN Calculation:

It is a product of the above mentioned attributes.

 

 

RPN Action Priority

When risk is determined to be unacceptable, it is recommended to prioritize the actions.

1.      Error Proofing (Eliminate Failure Mode or Address Cause)

ü  Failure Mode (Only Severity of 9 or 10)

ü  Causes with High Occurrence

2.      Improve Potential Process Capability

ü  Increase Tolerance (Tolerance Design)

ü  Reduce Variation of the Process (Statistical Process Control and Process Capability)

3.      Improve Controls

ü  Mistake-proofing of the tooling or process

ü  Improve the inspection / evaluation techniques

 

FMEA linkage to Problem solving technique:

 

DMAIC Phases	Linking FMEA to
Define	Problem statements in the charter and FMEA are linked. Problem areas are easily identified through prebrainstormed areas. It would be easy to locate, where the error is happening from an FMEA
Measure	Cause and effect diagram is linked to FMEA, where the possible causes are priortized using FMEA and then the respective data is collected.
Analyse	Each failures are listed and anlaysed part by part for its occureneces and controls available to strenghthened the process.
Improve	When the new product is on the way or the existing requires a change, the design phase involves the risk assessment and risk mitigation plan using FMEA
Control	Current controls are validated and new controls as pe rhte change process, it is recommended.

 

Limitations for FMEA as risk assessment tool:

1.      Resource limitation: When the risk is assessed and identified that the RPN is high, but has limited resources in terms of knowledge/ manpower / controls, theis has to be given highest priority. Since, this might go out of company and dissatisfy the customer.

 

2.      No definitive RPN thereshold : there is no definite RPN threshold to decide the areas which has to looked into. Now it depends on the factors like quality, safety regulations, etc. However the pareto is used to prioritize the critical risks. Hence 20% of the risks are given high priority basis RPN scores to improve the process.

 

3.      Regrouping of the team for reassessment of process RPN:

Most of the organizations implement the actionable as part of pre FMEA analysis and the process is also improved. But they fail to regroup as a team and reassess the Process using FMEA to calculate the RPN scores. So that we can compare the RPN scores before and after process improvement calculated for project efficiency. This regrouping may not happen due to limited resources, multiple projects, lack of time, etc.

 

4.      Knowledge on the process – If the team behind does not know what to list as failure or how to detect, the failures would be unknown to the FMEA team. In some other cases, if they forget to list one failure mode also,  it is said that failure is waiting to happen.

 

5.      Considering FMEA as solution tool – FMEA only provides us where the problem is how serious it is. It will not provide us solutions to reduce the risk. It is the team that they have to develop actions for the highest RPN’s failure modes.

 

 6.      Problem Scope  – When we try to reveal the entire process in one FMEA, many failure modes would go unnoticed. The solution is break down the process into multiple segments and then perform FMEA for each of the segements

 

7.      FMEA – static model – FMEA is not a static model. This has to be updated frequently whenever the changes are happening to the process, all the failure modes to be listed, calculate RPN and provide some corrective actions.

  

8.      Bias towards RPN ratings – When the ratings are given on a subjective basis, there can be biased in rating. For eg. The severity of smoke while smoking is rated as 10 for a non smoker and 3 for a smoker. This tweeks the RPN score as well. Hence it is important to work out as a team on the ratings.

 

9.      Experienced operators – If the experienced operators of the process are not part of the FMEA team , the FMEA conducted may not be effective. Only they can provide a valuable insight to the process errors.

 

10.  If detection controls are not tested adequately – If the detections are not tested and given ratings, then the FMEA may not be effective to create a corrective or preventive actions.

 

Conclusion:

The important point to remember while doing FMEA is to always update the FMEA regualarly and create related control plans. In order to reduce the risks frequently.  Failure to do so can have serious consequences, when a severe problem is not documented or ends up causing harm to a customer. FMEA is an important part of any production process, but needs to be supplemented with other project methodologies to be completely effective. It is only a assessment tool, where it will not reduce or eliminate the potential failures. Hence it should be clubbed with other error proof tools like 5s, Poka yoke, Visuals, etc to make it effective.

 

 

Reference - https://quality-one.com/fmea/

 

thanks

Kavitha 

 

FMEA:

 

Failure Mode and Effect Analysis is a technique being extensively used in quality management. It is also used in six sigma extensively.

FMEA is a step-by-step approach for identifying all possible failures in a design, production, service and delivery and so on. 

 

The risks of FMEA:

the parameters considered and ranked are based on probability. Hence the actual results may be different from what is ranked.

even though, FMEA rankings are made also based on facts and figures or historic data, it is also sometimes made based on the feeling or experience. 

The results of the analysis in such case may not be true. 

Failure Mode and Effects Analysis (FMEA) is a procedure for determining points where processes, products or designs are most likely to fail and the reason why they would fail.

 

It is used while designing processes (and/or) reviewing and improving an existing process (and/or) for process control.

 

FMEA is essentially a step-by-step procedure to identify each failure mode. Further analysis then helps estimate the effects of failure and devise process control methodologies so that the identified failures can be averted.

• Process FMEA used to evaluate manufacturing and assembly processes.
• System FMEA used to analyze complete systems and/or sub-systems during the design concept stage
• Design FMEA used to examine product designs before their release to manufacturing.

 

Limitations:

1. Only as good as the knowledge of the team using it. Issues and failure modes beyond the knowledge of the team member will go undetected or unresolved.
2. Chances of Human error (by the team) of missing out a failure mode is possible, in which case, it would be ignored.
3. FMEA prioritises Failure mode according to their risks. This may not eliminate all failure modes.
4. Selection of the failure modes for analysis could be tricky as the team could land up picking something that is either too big or too small. Process should be broken down into manageable segments.
5. FMEA is a dynamic procedure and needs to be constantly reviewed and revisited to assess new risk and failure modes that may com up and control plans developed.

What is Failure Mode Effect Analysis (FMEA)? 

• The FMEA is an team oriented analytical methodology which aims for identifying and correcting potential failures in a systematic and structured manner

   

• The FMEA is already implemented in an early phase of the product engineering process and tries to identify imaginable/possible failures and implements corresponding corrective actions. 

• The FMEA aims for reducing the risk of possible failures in the best possible way. The method records the generated knowledge to the advantage of the organization and integrates the lessons learned into future tasks and scopes.

   

• The FMEA is living documents that must be reviewed and updated whenever the process has been modified 

There are three basic cases for which FMEA process is to be applied….

 

1. New designs, New Technology or New Process  

2. Modification to existing design or process

3. Use of an existing design or process in a new environment, location or application usage on the existing design or process. 

In Six sigma DMAIC methodology, Initially, FMEA is done in Measure phase and provides recommended actions for the team to minimize risk to the customer. Its revision continues up to the Analyze and Improve Phase to ensure that the evaluation criteria and cause/effect relationships are updated with data-driven conclusions. During the Control phase, the FMEA needs to be updated to reflect the final state of improved project. The information from FMEA is then summarized in the control plan documents

 

Process of Carrying out FMEA

 

1. Review the process and list the Process steps and key Process inputs  – can be derived from process maps, cause and effect diagram, brainstorming sessions or existing process data.

2. Brainstorm all the expected potential failure modes for each key process input – can be described in physical/technical terms ,not as a symptoms noted by the customer

3. List the potential cause for this failure mode – May be several causes for such failure, here consider the operating conditions, usage or in-service, and possible combinations as potential causes.

4. List the controls that are existing in place to detect the cause of the failure mode.

5. Rate the severity of the failure effect  the customer experiences  in a Scale of 1 to 10 (1 being no effect and 10 being the Hazardous without warning)

6. Determine how often the cause of the failure mode occurs and rate the occurrence in a scale 1 to 10 (1 being unlikely to 10 being almost inevitable)

7. Determine the effectiveness of the current controls to detect the cause of the failure and rate the detection criteria in a scale of 1 to 10 (1 being very effective detection and 10 being no detection.)

8. Calculate the risk priority number(RPN)by multiplying Severity, Occurrence and detection together.

   Note : Risk priority number (RPN) = (probability of occurrence) x (severity ranking) x (detection ranking).Highest RPN would be 1000 and lowest would be 1 , lowest RPN is lower risk. However if the severity rating is 9 or 10 ,efforts should first focus on these key process inputs to ensure detection is at least 1 or 2 and occurrence is also low.

9. Establish the action plan which can help to minimize the risk to customer by using the RPN value –recommended action can only impact the detections or Occurrence. Severity will remain same until and unless the product/service or information is used for a different intent.

10.  Identify the person responsible to complete the recommended action with target date

11. Once the action taken, list the specific actions taken, along with the actual completion date

12. Calculate or reevaluate the resulting RPN, based on the completed action.

13. After finishing the above-mentioned steps, sort the RPN numbers and identify most critical issues and where to focus first 

For understanding clarity, tried to describe the rating scale elaborately as below, which can be used as reference for FMEA RPN calculation  …  

 

Severity	Rating	Occurrence	Rating	Detection	Rating
No effect -None (Unable to realize a failure has occurred.)	1	Very Low <1 /1500000 (Failure is unlikely)	1	Almost certain (Defect is obvious and can be kept from affecting the customer)	1
Annoyance- Very Minor (Very Minor on product or system performance. Minor defects noticed by discriminating customers. No disruption to product line. No effect to performances. Inconvenience to administration of customer)	2	Low- 1/150000 (Relatively low failures)	2	Very high (Very high chance of detection. All units are automatically inspected.)	2
Annoyance - Minor (Minor on product or system performance. Minor defects noticed by some customers)	3	Low- 1/15000 (Relatively low failures. Isolated failure associated with similar process,)	3	High (High Chance of detection. SPC is 100% inspection surrounding out of conditions)	3
Annoyance - Very Low (Small impact on product performance. The product does not require repair. Minor defects noticed by most customers.                               Major disruption to production line. Significant delays in delivery to end customer. No effect on performance)	4	Moderate -1/2000 (Occasional failures. Generally associated with processes similar to previous processes which have experienced occasional failure, but not in major proportions)	4	Moderate high (SPC is used with an immediate reaction to out of)	4
Loss or degradation of secondary function -Low (Moderate impact on product performance - The product requires repair. Reduced secondary function performance.)	5	Moderate -1/400 (Occasional failures. Occasional failures. Generally associated with processes similar to previous processes which have experienced occasional failure, but not in major proportions)	5	Moderate (Process is monitored and manually inspected)	5
Loss or degradation of secondary function -Moderate (Product performance is degraded. Comfort or convenience function may not operate. Loss of secondary function performance. Major disruption to prod line. Customer product may have to be reworked. Customer product operable. End use experiences some dissatisfaction.)	6	Moderate - 1/80 (Occasional failures. Occasional failures. Generally associated with processes similar to previous processes which have experienced occasional failure, but not in major proportions.)	6	Low (Manual inspection with mistake proofing modification)	6
Loss or degradation of Primary function -High (Product performance is severely affected but functions. Reduced primary function performance. A portion (<100%) of customer product may have to be scrapped. Customer product operable but at a reduced level of performance. End user dissatisfied.)	7	High- 1/20 (Repeated Failures. Generally associated with processes similar to previous processes that have often failed)	7	Very Low (All units are manually inspected)	7
Loss or degradation of Primary function - Very High (Product is inoperable with loss of primary function. The system is inoperable./ Loss of primary function. 100% of customer product may have to be scrapped. Customer product inoperable, loss of primary function. End user very dissatisfied.)	8	High- 1/8 (Repeated Failures. Repeated Failures. Generally associated with processes similar to previous processes that have often failed.)	8	Remote (Units are systematically sampled and inspected)	8
Failure to meet safety/regulation - Hazardous with warning (Failure involves hazardous outcomes and/or noncompliance with govt. regulations or standards)	9	Very high -1/3 (Failure is almost inevitable)	9	Very Remote (Occasional units are checked for defects)	9
Failure to meet safety/regulation - Hazardous without warning (Failure is hazardous, and occurs without warning. It suspends operation of the system and/or involves noncompliance with govt regulations)	10	Very high >1/2 (Failure is almost inevitable)	10	Almost impossible (Defects caused by failure is not detectable)	10

 

 

As we know, the latter the failure is detected, the higher will be the corrective cost and customer dissatisfaction. If FMEA is done in the early stage with right way it will help in reducing the risk of possible failures in the best possible way. While FMEA as a preventive tool is highly beneficial for the organization, but it has certain limitations too.

 

Limitations: 

1. Team Formation: Depends on how the interdisciplinary team is formed and what is their expertise on subject knowledge (product, process) and FMEA methods – If team is good, output will be good.

2. Team members Involvement: Whatever the subject matter expert team may be, If the team is not actively involved, a superficial look at the process will miss many failure modes.

3. FMEA Moderator: if the moderator is not expert, competent, target orientated and biased towards certain opinion, it may derail from its objectives.

4. Prioritization: The initial output of an FMEA is the prioritizing of failure modes based on their risk priority numbers. Mostly Severity and occurrence ratings are often difficult for individuals or teams to estimate.  

5. Time factor: This process takes time for discussion/brainstorming session

6. Rating Scale Customization: Generic rating scale may create confusion; creation of meaningful rating scale plays a vital role in rating.

7. Unknown Failure mode: Certain failures which is outside of the team experience, may be left in discussion and documentation.

8. FMEA Timing: FMEA not initiated on early stage or design stage, may miss certain design /process verification

9. Target Customer: Customer is both internal and external, but if the FMEA is targeted considering only external customers, internal process failure impacts may be missed from consideration.

10. Product/Process: Every product /process is not similar and different from others and FMEA should be carried individually not coping & pasting from one to another.

11. Detection Control: Assuming detection controls are more effective while in real they are not

12. Action on Recommended failure mode: FMEA is a prioritization tool. It doesn’t eliminate failure modes or effects by itself. Organization need to apply mistake-proofing tools to eliminate the root causes of failure modes, especially true with failure modes that have very severe effects.

13. FMEA/Control Plan Update: It is a live document, needs regular review and update if a new potential failure mode is identified, that should be added to the FMEA and control plans developed for that. The control plan tells people how to react when a failure mode occurs, if FMEA is not tied to control plan, people would not be aware how to react in case of failure.

Note : FMEA Worksheet template is attached for better understanding

FMEA-template.xls

Rating Template.docx

Edited November 23, 20178 yr by Anirudh Kund
Attaching Rating Template

Given the many benefits of FMEA in assessing posaible risks in a process and predicting any possible failures that may be there in a process, there are certain limitations that FMEA has... 

-FMEA by itself, in isolation is only a tool for assessment and has to be supplemented with another error eliminating strategies or tools to actually see the benefit of the exercise. 

- The effectiveness or Impact of FMEA is proportional to the knowledge, experience, awareness, attitude and wisdom of the people behind it. 

- It is not a one time process and needs to be updated and reviewed as the new elements of risks keep occurring or coming up in a given process. 

- FMEA as a process needs to be balanced... It cannot have too much of detail or too less of detail for analysis as too much can cause a lot of effort and time consumption and too little will not give enough o relevant output. 

Apart from the above the most conspicuous limitation that most of the practitioners attribute to the FMEA is the more than due bias towards severity during the calculation of RPN. 

It is a must that FMEA is done by an able team with expertise in subject matter.  

In my humble opinion, there are no distinct advantages or disadvantages of any tool or for that matter anything. Each tool has its unique features, which under some conditions act as advantages and under other conditions act as disadvantages. So is the case with Failure Modes and Effects Analysis (FMEA) also. The best way to identify the limitations and the conditions under which these limitations are experienced is to do an FMEA on FMEA, the results of which is depicted below.

Sr. No.	Limitation	Counter-measures
1	Teams that use FMEA may not always be sufficiently trained on FMEA and also know the domain adequately	Establish and institutionalize norms for participation in FMEA
2	Not all failure modes may be covered	Appoint well experienced facilitators to compere the FMEA session and have the facilitators guide the team through multiple perspectives
3	Prioritization tends to draw attention to certain failure modes only and may not eliminate all failure modes	Consolidate low priority failure modes, repositorize them and keep reviewing them periodically to ensure that they do not drop off the radar
4	Tendency for the FMEA team to misjudge scope, either bite off more than what they can chew or just keep nibbling without getting anything substantial	Present the initial scope in manageable blocks and work on one block at a time
5	Yesterday’s FMEA can become obsolete today	Build in a review frequency in the FMEA procedure and follow it. Include FMEAs and reviews in the scope of periodic process audits or Management Systems audits
6	Sometimes, certain factors will be rated the full 10 out of 10 and may not ever change	When discussing actions to reduce the RPN, spend adequate time on reducing all three factors viz. Severity, Occurrence and Detectability
7	Chances of the FMEA, “running away” with uncontrollably and unmanageably too many failure modes	As part of the FMEA process, whenever a failure mode is proposed for discussion, let the first step of the discussion be to review it for duplicacy and overlap and accordingly decide whether to record it as a separate failure mode or merge it with another failure mode
8	Templates are too cumbersome for filling and discussing	No need to stick to the classical template. Review the template cell by cell and customize it according to requirements. Buy computerized templates or develop your own FMEA application.

FMEA:

            FMEA is a Procedure that helps us to identify & understand the Potential Failure modes, their Causes & the effects of the Failure in the Process or the end User. It helps to analyse the Risks involved with the Failure Modes, Effects & Causes &  Categorize the issues for the Corrective Action.

The Main goal of the FMEA is to align the Risks that are available within the resources. This helps to identify the Root causes of the Risks involved, allows to detect the occurrence of the Risks & to get a better solution to overcome the Risks.The Primary objective of the FMEA is to improve the Process & reduce the failures that would occur in the Process

 

Types of FMEA:

- Design FMEA

- System FMEA

- Process FMEA [Which is being commonly used]

 

Risk, Risk Assessment & Risk analysis:

- Risk can be said as the likelihood of Occurrence of an undesirable event.

- Risk Assessment is the determination of quantitative / qualitative value of Risk related to a Concrete situation

- Risk analysis included

1. Identification of Risks

2. Estimation of the likelihood of Occurrence

3. Estimation of the Causes & impact

4. Risk evaluation & development of risk 

 

Limitations of FMEA in Risk Analysis:

RPN - Risk Priority Number plays an important role in the FMEA, to determine the Risk factors involved.

RPN = Severity X Occurrence X Detection

 There are certain limitations in the FMEA during the Risk analysis. They are as follows

- It needs an effective team to carryout the Risk analysis in an efficient manner. Small disputes between the Team members may lead to improper FMEA 

- FMEA can describe the Risks involved in the Process to a certain extent only. Unknown hidden failures cannot be addressed completely.

- Sometimes it doesn't directly capture the Failure mode & doesn't cover the Multiple failures involved in it

- And another limitation is not covering the entire Failure modes involved. For example what happens if a Product fails at the End user will not be clearly explained in the FMEA

 

So FMEA when it is done correctly & effectively it will be an useful tool to Prevent Problems, reduce the Costs & develop the Process

 

Hi all,

FMEA, another tool developed by military, a qualitative but still one of the structured & most effective tools in identifying and assessing the risk associated with potential failure mode/s along with plausible corrective measures.

The answers from majority of the members were really detailed and only reflects on the fact that we all are giving our best to share our knowledge for the benefits of business excellence fraternity.

  

 The best three answers on this however were from Mr. Venugopal R., Mr. Ronak and Mr. Anirudh Kund.  The key was to address the limitations of FMEA as a tool in risk assessment. There were some more  responses very close in addressing the question quite precisely too. Best answer however, was from Mr. Anirudh Kund addressing not only the limitations but also on how to go about FMEA in a very systematic manner.

Congratulations Mr. Anirudh”