Failure Mode and Effects Analysis (FMEA)

What is FMEA? || What purpose of FMEA? || Common definitions || Why FMEA || FMEA Process Map Table || FMEA Process Flow || Type of FMEA || Process Failure Modes and Effects Analysis (PFMEA) || PFMEA Procedure || PFMEA Severity Ranking Criteria || PFMEA Occurrence Raking Criteria || Common Mistakes in FMEA Implementation ||

What is Failure mode and effects analysis (FMEA)?

"Failure mode and effects analysis(FMEA): A process which use a multidisciplinary approach to recognize and evaluate the potential failure of a product/process and the effects of that failure. "

Failure mode and effects analysis(FMEA): A process which use a multidisciplinary approach to recognize and evaluate the potential failure of a product/process and the effects of that failure. This process will be followed by the identification of preventive action that could eliminate or reduce the chance of the potential failure occurring.

In casual use "FMEA" also means "Failure modes and effects Criticality Analysis (FMECA)". FMEA Is proactive analysis tool support to anticipate failure modes even before any occurrences as well as possible to prevent the negative effects of these failures modes from reaching the customers before new product / process is released.

Failure mode and effects analysis(FMEA) is a systematic practice or procedure set for identifying and evaluate the potential failure modes of a process / product & its effects, and Identify actions that assessing the risks associated with these failures to eliminate or reduce the change of potential failure occurring. The results of FMEA cycle process is the FMEA Table / Risk assessment table, describe how vulnerable a product /process is to its potential failure modes and represent the level of risk attached to each potential failure mode, as well as what sufficient actions / corrective actions are required to make the change of product / process more robust.

Purpose of Failure mode and effects analysis (FMEA)?

Common definitions

Keyword Abbraviation
Fault Inability to function in a desired manner, or operation in an undesired manner, regardless of cause.
Failure As simply, Failure mean system, products / parts, assembly or function in not accordance with design committed or not meeting the specification. A mistake, fault or error owning to breakage, wear out, or compromised structural integrity.
Failure Mode The manner in which a fault occurs, that is the way in which the element faults. A failure mode we can considered is the manner in which a product / parts, assembly or system failure occurs.
Failure effects The consequences of a failure mode on a function, status, operations of a process, environment, system. The adverse consequence is cannot meet end application, poor appearance, and or the undesirable results of a fault of a system element in a particular mode. Failure effects can be harmless or fetal that equipment loss and major damage can perform.

Why FMEA?

FMEA Process Map: Table

What Results
(Process Indicators)
By What?
(Equipment, Materials)
Inputs By Whom
(Personal)
How? Outputs
Number of field failure mode did not identify in failure mode and effect analysis. Generally, outcomes from internal audit reporting. To use suitable equipment and materials Process flow chart, product / process control specification, and previous field failures of similar type of products. Personal in charge - As Per Defined FMEA form, qualified in process / product knowledge. Failure mode and effects analysis guidelines, manuals Potential failure mode and effect analysis report

FMEA Process flow

FMEA Process flow chart, fault tree analysis, PFMEA process flow template, PFMEA process flow Diagram

Type of FMEA

There are many type of failure mode and effects analysis, but the probably used in general are (1) Design FMEA and (2) Process FMEA or Product FMEA, others are (3) system FMEA (4) Service FMEA (5) Software FMEA. Here we are talk about design & Process FMEA, but design & process FMEA is simply fit to any segment or organization that we discuss both type of FMEA.

Different between Design & process FMEA

Details Process FMEA Design FMEA
Purpose To meet specification in drawing. Production in compliance with Drawing's specification To meet Target Specification.
Responsibility Process Planning / Production Design & Development
Objective To avoid quality failure in process planning, production implementation. To avoid quality failure in design & Development
FMEA start After Design release. After concept design.
FMEA - Period of Review Prior to any investment Prior to first run
FMEA Initial / First completion Prior to bulk production Prior to production release
FMEA End Prior to series production Prior to production

Process Failure mode and Effects Analysis (PFMEA)

The process failure mode and effects analysis (PFMEA) is an analytical method to ensure that potential failure mode and their associated causes have been considered and addresses.
The process failure mode and effects analysis (PFMEA) used to studying production planning risk management in manufacturing and other product realization activities is to focus the quality system control and processes with high risk. This article (qualitybook.org) provide methods and instructions for risk analysis study using process failure mode and effect analysis (PFMEA).

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General Procedures to conduct PFMEA:

» Process function and Requirements: When we making a FMEA for particular product / process that all the details and descriptions should be specific and must first be expressed. The details must be easier that concern / responsible personnel can understand and ensures functions & system of product / process. Each function of the process should be specified and list outputs of the process maintained.
» Potential failure mode: Describe how the particular part could potentially fail to execute its task. Index the failure modes those are possible to occur against the requirements specified.
» Potential effects of failure: Index the effects of failure in next operation, subsequent operations, customers and end user environment. For each failure mode, effects must be identified and indexed at in particular field, the customer (internal / external) experience with failure occurs.
» Severity: Severity is the rank associated with most serious effect for a given failure mode and it is also requiring consumer involvement while assessing the severity. For the minimize or reduce significant level of severity ranking needs to sufficient change in design. For instant ranking manage refer ranking table. Assess the seriousness of the effect in specific scale, the rating should apply to effect only and remember that the while giving ranking consider only the required criteria that is next operation.

Severity ranking Criteria Table: PFMEA

Effect Description Rank
Failure to meet safety and/ or regulatory requirements (1) Major Customer Dissatisfaction (2) Cause Non-system operations (3) Non-compliance of government regulations 10
Significant Disruption, Degradation of primary functions (1) High degree of customer dissatisfaction (2) Non-functionality of system 8-9
Loss of secondary function (1) customer Infuriation (2) deterioration of part / system performance 6-7
Annoyance / Moderate effects (1) Appearance or Auditable (2) Moderately deterioration of system performance 3-5
Minor (1) Minor natural that internal / external customer (2) probably not detect the failure 1-2
» Classification: Classification field / column generally used to identify safety risks. It is classifying any special product characteristics and indicate the special characteristics symbol. Confirm these appearances are identified with symbol on methods and manufacturing related documents.
» Potential cause(s) of failure: Identify possible causes of each failure mode and Index all possible potential causes of failure mode like man, machine, tools, process parameters, use cause & effect diagram , index the root causes under the first level causes using why-why analysis. Generally, a potential cause should be actually initiate the failure to occur, as example the equipment setup, operator error etc. Define the causes in such a way that can be eliminated or controlled.
» Occurrence: Occurrence is the likelihood that a particular cause or failure will occur. Rank how often a particular cause is likely to consequence in the failure mode being analyzed and it should be estimated the probability of occurrence on specific scale. In case of new processes having no historical experience that use the team judgement.

Occurrence Ranking Criteria Table: PFMEA

Likelihood of Failure Description Rank
Very high > 100 / 1000
> 1 in 10
10
High 50 / 1000
1 in 20
9
High 20/1000
1 in 20
8
High 10 /1000
1 in 100
7
Moderate 2/1000
1 in 500
6
Moderate 1 / 1000
1 in 2000
5
Moderate 0.5/1000
1 in 10000
4
Low 0.01 / 1000
1 in 100000
3
Low < 0.001 /1000
1 in 1000000
2
Very low Eliminated by preventive control 1
» Current process control - Prevention and Detection: Current process control prevention is used for the methods that have been used to prevent a specific cause hence the detection field used to document methods that have been used to detect either the cause or failure mode. Index the existing controls, which can detect the causes or failure mode, while indexing specifies the frequency of detection measures.

Type of Controls

Level Type Examples
Prevention Prevention of causes Mistake Proofing
Detection Detection of causes and leading to corrective action detection of defects Statistical process control, visual control etc., full inspection
» Detection: Rate our capability to detect either a cause or a subsequent failure mode. Use best detection available. The rank allied with the best detection control indexed in current process control field. Assume failure had occurred and then evaluate the capabilities of controls to prevent or detect. Measure the possibility of controls indexed in the earlier field, which will detect the root or failure mode. While giving ranking.

Detection Ranking Criteria Table: PFMEA

Description Rank
Very low (or zero) probability that the defect will be spotted. Substantiation and/or controls will not or cannot detect the existence of an insufficiency or defect. 10
Low probability that the defect will be spotted. Substantiation and/or controls not probable to detect the presence of a deficiency or defect. 8-9
Moderate probability that the defect will be spotted. Substantiation and/or controls are likely to detect the existence of a deficiency or defect. 5-7
High probability that the defect will be noticed. Confirmation and/or controls have a good chance of detecting the existence of a deficiency or defect. 3-4
Very high probability that the defect will be spotted. Substantiation and/or controls will almost certainly detect the existence of a deficiency or defect. 1-2
» Risk Priority Number (RPN): Calculate the risk priority number(RPN) is the multiplication of severity x occurrence x detection. Simply the part the failure mode severity, Failure cause probability and control detection effectiveness ratings, therefore RPN is multiple of all three above. While calculating RPN, consider only highest severity rating of each failure mode.
» Recommended Actions: Identify actions to address potential failure modes that have a high risk priority number noted. When any risk priority number identified as high needs to immediate attention of the concern since it indicates that the failure mode can consequence in a massive negative effect. It is failure source have a high probability of arising, and there are inadequate controls to catch it. So actions must be defined to address failure modes that have high risk priority numbers.

Common Mistakes in FMEA Implementation

Conclusion:

Failure mode and effects analysis (FMEA) is a tool to identify risks in your process, it can be used in multiple places in process improvement and it is helps to determine where problems are, identify cause/ effect relationship and highlight risks in solutions and actions to take. It is easier to identify risks to define categories like: (1) severity of impact (2) probability of occurrence and (3) ability to detect the occurrence. Generally, this tool used on early stage that is initial stage, new product / process development needs to define to understand process and identify problem areas, and analyze data to assist identification of root cause to determine best improvement with lowest risk. To the complete Failure mode and effects analysis, needs to accurate ranking for each field, see below table:

Failure mode and effects analysis(FMEA) Rankings

Severity Occurrence Detection Ranking
Hazardous without warning Very high and almost inevitable Cannot detect or detection with very low probability. 10
Loss of primary function High repeated failures Remote or low chance of detection
Loss of secondary function Moderate failures Low detection probability
Minor defect Occasional failures Moderate detection probability
No effect Failure Unlikely Almost certain detection 01

General Process Steps:

▾ Describe the product or process in first field.
▾ Design a block diagram of the process or product.
▾ Complete the header details of the failure mode and effects analysis Table.
▾ Tally the objects (components, functions, steps, etc.) that create the product or process.
▾ Identify all potential Failure Modes associated with the product or process.
▾ Index each Failure Mode to communicate and discuss with technical term.
▾ Describe the effects of each of the failure modes listed and assess the severity of each of these effects.
▾ Identify the possible cause(s) of each failure mode.
▾ Quantify the probability of occurrence of each of the failure mode causes.
▾ Identify all current controls that contribute to the prevention of the occurrence of each of these failure mode causes.
▾ Determine the ability of each control in preventing or detecting the failure mode or its cause.
▾ Calculate the Risk Priority Numbers (RPN).
▾ Identify action(s) to address potential failure modes that have a high RPN.
▾ Implement the defined actions.
▾ Review the results of the actions taken and reassess the RPN's.
▾ Keep the FMEA Table updated.


First Published On Date: Monday, May 15, 2017 8:00 PM

Author: ARUN RAVAL | Business & Systems Analyst