FMECA & CMMS: maintenance excellence
Wednesday 23 december 2020
The implementation of an FMECA strategy, based on the knowledge base of failure modes, their effects and criticality, will, on the one hand, improve the design of equipment for greater reliability and safety, and on the other hand, seek to facilitate maintenance for a better level of service and cost reduction.
It should also be noted that an FMECA strategy is frequently required during a standardization process. Examples include ISO 9001, QS 9000, ISO/TS 16949, Good Manufacturing Practices, GMP as required by the U.S. Food and Drug Administration (FDA).
In this article, we will discover exactly what FMECA covers, how to implement this maintenance excellence strategy and how its interest is reinforced when it is associated with CMMS software.
WHAT IS AN FMECA STRATEGY?
The acronym FMECA stands for Failure Modes, Effects and Criticality Analysis.
The aim is to analyze the types of failures, breakdowns and shutdowns of equipment, their effects on production and the probability of such events occurring in order to take anticipatory measures. Thus, a maintenance action such as the change of a component of an equipment can be added to the preventive maintenance plan, following the results of the FMECA analysis.
The FMECA analysis therefore requires the identification of the following information:
- Which equipment is concerned
- What is its main function
- A list of the types of breakdowns that may occur, as well as their probable causes and effects
- Maintenance and controls already in place
- Recommended actions to prevent shutdowns
All this information is held by a CMMS in which the technical data has been correctly collected and centralized and can therefore be easily shared and used by all the players. We will come back to this later: the association of a CMMS with a FMECA strategy will allow us to enter the virtuous circle of maintenance.
WHAT IS THE DIFFERENCE BETWEEN FMEA AND FMECA?
First of all, it should be noted that the acronym FMEA for Failure Mode and Effects Analysis is sometimes used. The two notions are very close: FMEA can be considered as a necessary but not completely sufficient subset of the analysis. The "C" of FMECA adds criticality analysis.
The steps for setting up a FMEA strategy are as follows:
- Identify and list all failure modes
- Analyze the effects of the failure
- Determine the causes of the failure
- Report results graphically
In order to implement a comprehensive strategy, the following essential actions must be added to this approach:
- Carry out criticality calculations: i.e. assign a score per risk and weight it according to its probability.
- Determine the equipment presenting the highest risk
- Take risk mitigation measures and justify, document remaining risks
- Monitor the implementation and effectiveness of corrective measures
Thus, the criticality component of FMECA consists of assigning a score from 1 to 10 to the criteria of probability of failure, consequences and confidence.
The confidence criterion is the plausibility of detecting the failure in time, i.e. before it reaches the end user or customer: the more difficult it is to detect, the higher the score will be, and conversely, the easier it is to detect, either with the naked eye or with sensors, the lower the score will be.
Multiplying these 3 factors gives a score from 1 to 1000, called Risk Priority Score or RPN for Risk Priority Number. The equipment with the highest score should be processed first.
Since this criticality is essential, it is possible to abandon the term FMEA to refer only to the complete strategy: FMECA.
DIFFERENT APPROACHES DEPENDING ON THE AVAILABLE DATA
Top-down, bottom-up, criticality analysis, several approaches are possible when conducting an FMECA analysis.
The top-down approach is used in an upstream phase during the design and conception of the machine in order to maximize its robustness. The analysis starts with the main production functions and the probable causes of breakdowns. Functional failures with significant effects on production are prioritized in the analysis results, but the analysis should be completed at a later stage of the design.
The top-down approach can also be used on an existing system to focus on the most problematic areas or those that have already shown signs of weakness.
The bottom-up approach is used when the machine design is completed. All the elements are studied one by one starting with the least critical parts, located lowest on the machine tree. The analysis ends when all elements have been taken into account.
Criticality analysis can be performed using a quantitative or qualitative approach. The availability of part configuration and failure rate data will determine the approach to the analysis. The general rule is to use a quantitative approach when actual data on components or sub-equipment are available and a qualitative approach when data are not yet available or are too generic.
The aim is to define the reliability or unreliability of each component, at a point in time T of operation and to identify whether the unreliability can lead to a failure, and especially whether the damage is probable and/or serious.
The calculation formula is therefore as follows:
item unreliability x probability of failure x probability of loss or stoppage of production
Qualitative criticality without real data on the equipment will be based on a criticality matrix, with the abscissa the severity of the potential effects of the failure and the ordinate the probability of occurrence of each failure.
A CMMS TO CONDUCT FMECA ANALYSIS
On the one hand, to be conducted efficiently, FMECA analysis requires a significant amount of information about the equipment. On the other hand, the FMECA will produce new data that will have to be recorded and analyzed periodically to evaluate the positive or negative impact of the actions implemented. In these 2 inseparable parts of the FMECA analysis, CMMS plays an essential role.
Indeed, the CMMS lists the equipment and holds their technical characteristics sheet, it records breakdowns, damages and curative and preventive maintenance actions already implemented.
By extracting these data from the CMMS, in raw Excel format but also in the form of ratios and graphs such as the number of failures over a period, the time spent in intervention, the preventive / curative ratio, the preventive maintenance coverage rate, etc., the maintenance expert will obtain the raw material to begin your analysis.
Once the FMECA analysis has been completed and the equipment to be treated as a priority has been determined, the expert will be able to design the update of the list of maintenance actions to be implemented to reduce the level of risk carried by your machines.
These actions are in turn automatically recorded in the CMMS as they are carried out, whether it is a one-time curative maintenance or an addition to the preventive maintenance plan. The restitution of intervention reports, photos, time spent and parts used allow for an operational and financial analysis of the new procedures.
Finally, a new export carried out in the 6 months following the execution of the FMECA will make it possible to continue to update the list of equipment at risk and to learn from the first implementation.
FMECA analysis is the "absolute weapon" that maintenance managers must have at their disposal when they are looking to increase their efficiency and quality of service, while reducing their operating costs. FMECA is a major consumer of statistical data on equipment and events that have occurred, and must always be accompanied by the use of CMMS, from the beginning of data analysis to the study of the changes made. It is therefore essential to have a clear, modern CMMS, with an integrated FMECA module, capable of permanently exploiting the feedback of observed events to keep the service ranges and maintenance plans up to date. At present, very few CMMS have such a module. A good listener...
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