FMECA: Failure Mode, Effects, and Criticality Analysis

Overview

The FMECA (Failure Mode, Effects, and Criticality Analysis) method is originally developed by the U.S. military. The reference Military MIL-P-1629, entitled "Procedures for the Analysis of Failure Modes, Effects and Criticality, dated 9 November 1949.

This method was employed as a technique for evaluating failures to determine the reliability of equipment and system. The failures were classified according to their impact on personnel and the success of missions for the security of equipment. The concept interchangeable personnel and equipment shall not apply in the modern world of manufacturing consumer goods. Manufacturers of consumer products have established new values such as safety and customer satisfaction.

The FMECA was first used in the 1960s in the field of aeronautics for the analysis of the safety of aircraft. The implementation has long been limited to use in studies of reliability of equipment.

In the late seventies, the method was widely adopted by Toyota, Nissan, Ford, BMW, Peugeot, Volvo, Chrysler and other major manufacturers of automobiles.

In 1988, ISO issued the standards of the ISO 9000 series. QS 9000 is the equivalent of ISO 9000 for the car. A working group representing other Chrysler developed the QS 9000 standard for quality systems of suppliers. In accordance with QS 9000, automotive suppliers must use the quality of the planning process (APQP), including the FMECA tool and developing plans control.

The AIAG (Automotive Industry Action Group) and the ASQC (American Society for Quality Control) emit FMECA standards in February 1993. The standards are presented in a handbook of the FMECA approved and supported by three automobile manufacturers. This manual provides general principles for preparing a FMECA.

Despite having suffered much criticism due to cost and the cumbersome nature of its implementation, it remains one of the most popular and most effective. It is indeed increasingly used in security, maintenance and availability not only in material but also on the system, functional and software.

Therefore it is now widely recommended at international level and systematically used in all industries at risk, such as nuclear, aerospace, chemicals, food and others in order to find the preventive security operation.

Definition of terms related to the FMECA method

Criticality

Criticality is the mathematical evaluation of the occurrence and severity. Criticality = (S) × (O). This number is used primarily for items that require a higher quality.

Controls

Controls (design and process) are the mechanisms preventing the cause of a failure to occur.

Clients

External customers and internal staff and processes that will be affected by the failure of the product. Customer could be the next operation, subsequent operations or the end user.

Detection

Detection is an assessment of the likelihood that the controls (design and process) will detect the cause of a malfunction or failure itself.

Failure

A failure occurs when a product, component or set: Do not work, does not occur on schedule, does not stop on time, works at a desired or not work, but the performance requirements are not obtained.

Failure Modes

How a product, a component, an apparent failure or deviation from specifications. This mode can be one of the following forms: A strain, vibration, binding, loosening, corrosion, leakage, loss of performance, short-circuit, knotted, difficult to stop or start, exceeding the upper limit tolerated, etc.. The failure modes are sometimes described as categories of defects. A potential failure mode describes the way in which a product or process could fail in fulfilling its primary function.

Causes of failure

The causes of failure (upstream) are the circumstances involved in the design, manufacture or use, resulting in a failure. They belong to Mr. 5

Effects of failure

The effects of a failure (down) are the symptom which is detected by the alteration or termination of a required function, which is the consequence.

Elements FMECA

FMECA elements are identified or analyzed in the FMECA process. The common examples are: the functions, failure modes, causes, effects, controls and actions. FMECA elements become column titles of the form.

Feature

A function could be the purpose of a product or process. FMECA The functions are described in verbal form.

Occurrence (frequency of appearance)

The case is an evaluation of the emergence of a market failure (with the use, manufacture or design of a product).

Risk Priority Number: NPR

The risk priority number is the product of the Severity of the Occurrence, Detection. NPR = (S) * (O) * (D). This number is used primarily on items that need a quality education.

Severity (Severity)

The severity (or gravity) is an assessment of the importance of the effect of potential failure on the Client.

Special features of the process

Special features of the process are the characteristics for which changes should be checked against a target value for a particular characteristic of the product. This variation is maintained at its target value during manufacturing and assembly.

Special features of the product

The special characteristics of product characteristics for which a planned change could significantly affect the safety of a product or compliance with regulations or government standards.

The FMECA method: General principles

FMECA : Failure Mode Effects and Criticality Analysis.

AFNOR (French Association for Standardization) defines the FMECA as: An inductive method that allows a qualitative and quantitative analysis of the reliability or safety of a system.

The FMECA method is primarily a method of analysis of systems (systems broadly composed of functional or physical, hardware, software, human ...), static, relying on inductive reasoning (causes - consequences) , organized for the study of causes, effects of failure and criticality.

The FMECA method is to systematically examine potential failures of systems - analysis of failure modes - and their causes and consequences on the functioning of the whole-effects -.

The FMECA is a technique for analysis, particularly applies to the product or process, to estimate the risk of failures and their consequences. Each failure is characterized by:

• Gravity (G) collected by the customer / consumer ',
• the frequency of occurrence (F) and
• the risk of not detecting a fault (D).

It then defines a priority level of risk "NPR

NPR = FxGxD

After a ranking of potential failures, based on the NPR, priority actions are initiated, implemented and followed.

FMECA types and their use

There are several types FMECA as intended:

FMECA organization

The FMECA organization applies to different levels of main processes of the company: the first level which includes management processes, information, production, personnel management and marketing process, until the last level as the organization of a job of work.

FMECA product or project

The FMECA product or project is used to study in detail the design phase of the product or project. If the product of several components, we apply FMECA on components.

FMECA process

The FMECA process is applicable to manufacturing processes. It can analyze and assess the criticality of all the potential failures of a product created by its process. It can be used for the job.

FMECA average

The average FMECA applies to machines, tools, equipment and measuring devices, software and systems for internal transport.

FMECA service

The service applies FMECA to verify that the value added in the service meets the expectations of customers and that the process of realization of service does not failures.

FMECA Security

The FMEA applies security to ensure the safety of operators in processes where there are risks for them.

Stages of implementation of the FMECA

Before starting the implementation itself of the FMEA, it must meet certain preconditions deemed essential to a successful FMECA analysis.

Preconditions

The use of the FMECA requires prior:

• The formation of all potential actors and facilitator of the team.
• Crew training in the use of tools working group (Pareto, Ishikawa, etc.)..
• Description of a pilot FMECA for actions directly related to management.
• Provide the necessary means: The FMECA analysis requires considerable time (8 to 40 hours, see above) for each speaker or participant, and twice for the host.
• Availability of team members.
• Necessary for compliance with the procedure of reference and monitoring corrective actions.

The main stages in the development of the FMECA

The main stages of a process FMECA are:

1. The problem: Clearly define the objective and scope.

2. Identify the applicant and the decision maker: The applicant may be, for example, the client who seeks to ensure that all risks are identified. The decision is the project manager who accepts or not the customer's requirements and identifies the subject, time and budget allocated to the study.

3. Constitute the FMECA team: The team should be multidisciplinary and is composed of the host, which is the guarantor of the FMECA method, and representatives of the various functions involved. It is preferable that the host is not the designer process (or other) purpose of the study.

4. Functional Analysis: The system is decomposed into subsystems, and these elementary components. For each element we determine the main functions (what for) and function constraints (laws, regulations, standards, etc.)..

5. Qualitative analysis of failures: Identification of failure modes, causes that are at the origin (Causes of failure) and their effect (Effect of failure).

6. Quantitative analysis of faults: For each failure mode, assessing the severity, frequency of occurrence, the risk of failure to detect and calculate the risk priority number (NPR).

7. Determine the critical NPR: After ranking of failure modes according to NPR, NPR is determined, above which it should trigger corrective action.

8. Action Plan: Develop an action plan (what, who, how, when) to remove the causes of failures. The actions may be preventive or corrective.

9. Implementation and monitoring of action plan: Officials designated on the plan of action are responsible for implementing and monitoring corrective actions (or preventive) and record the results obtained.

10. Checking the effectiveness of solutions: The implementation of solutions is followed by a verification of their effectiveness. In cases where the solutions do not achieve the desired effect, we must take further analysis and identify new solutions .

Advantages and disadvantages of the method FMECA

Advantages of the method FMECA

Control the risks using the FMECA method used to carry out preventive measures, ie to solve problems before they do occur. If this method is followed throughout the life cycle product, production will be improved and free of problems.

Drawbacks to FMECA method

The FMEA requires a thorough knowledge of the issue to be studied. In general, a brainstorming session with several people involved from conception to delivery is required. This means that a team can reach an agreement on the failure modes studied. This method is, therefore, cumbersome to implement.

FMECA tools

Table listing of failure modes

NPR = GxFxD

Leaf analysis