APPLICATION
OF SYSTEM ANALYSIS AND PREVENTIVE MAINTENANCE ON CIGARETTE PACKER LINE
Mohamed fathi karoui
University of Carthage, Tunisia
E-mail: fathi.karoui@gmail.com
Mohamed Najeh Lakhoua
University of Carthage, Tunisia
E-mail: mohamednajeh.lakhoua@enicarthage.rnu.tn
Submission: 1/15/2020
Revision: 5/13/2020
Accept: 6/3/2020
ABSTRACT
The use of system
analysis and preventive maintenance in today’s industry becomes a necessity as it
increases equipment availability. These methods reduce the frequency of
failures. The objective of this article is to present a case study for
improving the reliability and availability of a production group in an
industrial enterprise. Next, we present an improvement in
maintenance. Finally, we present and discuss the application of preventive
maintenance. Through an industrial manufacturing model, we will combine three
tools; SADT modelling, the FMECA analysis and the Pareto diagram to arrive at
an optimal maintenance approach that will be a decision support tool in order
to minimize the repair costs and the downtime of the system.
Keywords: System analysis; industry;
preventive maintenance; SADT; FMECA;
Pareto diagram
1. INTRODUCTION
The
systemic approach, sometimes called systemic analysis, is an interdisciplinary
field relating to the study of objects in their complexity. Indeed, it
allows the description of a study object in its environment, in its
functioning, in its mechanisms and also in the interactions that result from
these three aspects (Lakhoua, 2013; Lakhoua, 2011; Lakhoua et al., 2016). The application of
system analysis and preventative maintenance allows the industrial company to
increase its profit thanks to the reduction of the budget needed for
maintenance (Lakhoua, 2018). In order to effectively implement effective
preventive maintenance that meets the company needs, it must follow a specific
approach that allows knowing first the most critical components of each
machine, and then to clear preventive actions related to these components.
In this context, we propose a
methodology to improve the reliability and availability of a production system.
This methodology consists of three stages; the first consists of a functional
analysis by the SADT method, the second in an analysis of failures by the FMECA
approach and finally in the prioritization of problems according to the number
of their occurrence by the Pareto diagram (Lakhoua et al., 2016; Bareib et al.,
2016; Monchy, 2015; Marca, 2012).
2. PRESENTATION OF A
CIGARETTE-MAKING PROCESS
The purpose
of this part is to visualize the main stages of the cigarette manufacturing
process (Figure 1). It is a way to understand, analyze, standardize and improve
the process (Rocha,
1998). Indeed, diagnosis is an essential step to
get a general idea of the current state of the process. Knowing the status will
be crucial to better detect failures and causes of malfunctions and will help
us to provide effective solutions. To do this, we will initiate our approach by
diagnosing the current functioning of the system which will allow us to locate
the most critical machine in the manufacturing process (Fakhfakh et al., 2011).
Although our
diagnosis was made on all of the factory's production equipment, in our case we
will limit the study to cigarette packaging equipment, where there have been
frequent stops and a very serious increase in cost during its malfunction, the
one hour shutdown cost is equivalent to 60,000 dinars with a very low machine
efficiency ƞ = 60% (Malaoui et al., 2017).
The tools
used in this work to improve maintenance will then be generalized on all
equipment of the plant after confirmation of the expected approach's results.
Figure 1: Cigarettes manufacturing
process
3. GENERAL INFORMATION ON
MAINTENANCE
In this
section, we will describe the main tools used in this approach. This is why we
present the concept of functional analysis by the SADT method, the objectives
and the different types of maintenance, as well as the history and interest of
the FMECA method, finally the Pareto diagram construction stage (Bassetto,
2005).
According to
standards NF X 60-010 and NF X 60-011: Maintenance is the set of actions to
maintain or restore a property in a specified state or capable of providing a
specified service.
Based on
this definition, two different concepts can be distinguished, one referring to
a corrective aspect and the other referring to a forward-looking aspect
(Vari-Kakas et al., 2015).
The maintenance objectives are
(Lakhoua et al., 2011 ; Lakhoua et al., 2018) :
·
Reducing the
outages frequency;
·
Minimizing the
duration of downtime due to
accidental service interruptions;
·
Ensure rigorous
and regular monitoring of maintenance performance (dashboard).
There
are different types of maintenance according to the NF X 60-000 standard.
Failure can
be defined as an alteration or cessation of a property’s ability to perform the
required function. There are two forms of failure: partial failure which is an
alteration or degradation of a property’s ability to perform the required
function and total failure which is the cessation of a property’s ability to
perform the required function.
·
Corrective maintenance,
sometimes called curative maintenance (a
non-standard term), aims to restore equipment
to an optimal
operating state for use. Various defects, failures or damage
requiring corrective maintenance resulting in immediate or very
short-term unavailability of the affected
equipment and/or a decrease in the quantity and/or quality of
the services provided.
·
Preventive maintenance:
Maintenance performed according to predetermined
criteria, the objective of which
is to reduce
the probability of failure of
a good or degradation of a service rendered. This should help prevent hardware failures in use.
The cost analysis should show a gain on the failures
it avoids. The purpose of preventive maintenance
is to: increase
the service life of the
equipment; reduce the likelihood of service failures;
reduce downtime in case of overhaul or
failure; Prevent and anticipate costly maintenance interventions. Make a corrective maintenance decision in good conditions; Avoid abnormal consumption of energy, lubricant, spare parts, etc. Improve working conditions of production personnel;
reduce maintenance budget; eliminate the causes of serious accidents.
·
Systematic Preventive
Maintenance: Preventive maintenance performed according to a schedule based on the
time or number of units of
use (produced). Even if time is the
most common unit, other units may
be used such
as: the quantity of products manufactured,
the length of the products
manufactured, the distance travelled, the mass of
the products manufactured, the number of cycles
carried out, etc. Conditional
preventive maintenance: Preventive maintenance subject to a predetermined
type of event
(self-diagnosis, sensor information,
wear measurement, etc.). Predictive maintenance is performed based
on the evolution
of a symptom or degradation for improved reliability, improved maintainability, etc. to evolve to zero failure.
3.1.
SADT
method
Structured
Analysis Design Technique (SADT) represents an image of the system (Figure 2).
It is a method of analysis to understand the main function of the system, what
sub-functions it must perform and finally, how these functions are performed
and the degree of their complexity. The method is based on a graphical model.
The modelling approach is top-down; from general behavior to detailed
operation, focusing on system activity (D. T. Ross, 1977).
The SADT method appears to be
suitable for modelling such systems for at least one reason: it applies
perfectly to multi-technology systems, that is, it adapts to mechanical,
electronic and software systems. But it does not take into account the dynamic
aspect of the system.
Figure
2: Structure of an SADT model
The boxes called ICOM’s
input-control-output-mechanisms are hierarchically decomposed. At the top of
the hierarchy, the overall purpose of the system is shown, which is then
decomposed into components-sub activities. The decomposition process continues
until there is enough detail to serve the purpose of the model builder.
SADT/IDEF0 models ensure consistency of the overall modelled system at each
level of the decomposition
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the main idea of the paper and must be typed in times new roman, 12, all caps,
centered.
3.2.
FMECA
The method presented in this research relates to failure mode, effects
and criticality analysis (FMECA). In fact, this method is an extension of the
failure mode and effect analysis (FMEA) (Buzzatto,
1999; Saman, 2017). The FMEA is an inductive upward
analysis method that can be performed at the functional level or at the part
level. The FMECA expands the FMEA by including a criticality analysis, which is
used to represent the probability of failure modes based on the severity of
their consequences. The result highlights the failure modes with a relatively
high probability and severity of consequences, which helps guide repair efforts
where they will produce greater value.
The FMECA analysis
procedure typically consists of the following logical steps:
·
Define the system;
·
Define ground rules and
assumptions in order to help drive the design;
·
Construct system block
diagrams;
·
Identify failure modes
(piece part level or functional);
·
Analyse failure
effects/causes;
·
Feed results back into
design process;
·
Classify the failure
effects by severity;
·
Perform criticality
calculations;
·
Rank failure mode
criticality;
·
Determine critical
items;
·
Feed results back into
design process;
·
Identify the means of
failure detection, isolation and compensation;
·
Perform maintainability
analysis;
·
Document the analysis,
summarize uncorrectable design areas, identify
special controls necessary to reduce risk;
·
Make recommendations;
·
Follow up on corrective
action implementation / effectiveness.
FMECA may be performed at the functional or piece part
level (Lakhoua et
al., 2019; Hammouda et al., 2015). Functional FMECA considers the effects of failure at
the functional block level, such as a power supply or an amplifier. FMECA
considers the effects of individual component failures, such as resistors,
transistors, microcircuits, or valves.
The
criticality analysis may be quantitative or qualitative, depending on the
availability of supporting part failure data.
Strengths of FMECA include its comprehensiveness, the
systematic establishment of relationships between failure causes and effects,
and its ability to point out individual failure modes for corrective action in
design (figure 3).
Figure 3: Corrective actions of the FMECA method
Weaknesses
include the extensive labour required, the large number of trivial cases
considered, and inability to deal with multiple-failure scenarios or unplanned
cross-system effects such as sneak circuits.
FMECA
is an excellent hazard analysis and risk assessment tool, but it suffers from
other limitations. This alternative does not consider combined failures or
typically include software and human interaction considerations. It also
usually provides an optimistic estimate of reliability. Therefore, FMECA should
be used in conjunction with other analytical tools when developing reliability
estimates.
The
FMECA was presented in some woks in order to analysis medical process in
hospital systems (Lakhoua, 2016; Lakhoua,
2018)
According to the figure 3, one notes that exist three
corrective action types: prevention actions, actions of preventive detection
and actions of effect reductions.
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3.3.
Pareto
Diagram
The Pareto
diagram prioritizes problems based on the number of occurrences and sets
priorities for problem-solving. This tool is based on the law of 20/80. In
other words, this tool highlights the 20% of causes that need to be addressed
to solve 80% of the problem.
It will be useful in determining
which levers should be given priority to significantly improve the situation.
This tool, relatively simple, makes it possible to present a factual business
problem. Phrases such as "We think the problem comes from", "if
we solve this problem it will probably improve" are thus avoided (Pareto,
1965).
The
construction steps of the Pareto diagram are: count the observed data; add the
number of observations/frequency; rank items in descending order; make the
total data; calculate the percentage for each data; calculate the cumulative
percentage; chart construction (Piketty, 2013).
4. ANALYSIS OF THE MAINTENANCE OF
THE PACKER MACHINE OF CIGARETTES
In
this part, we will identify the various subsystems and components of the packer
machine of cigarette on the basis on the analysis by the graphical tool SADT
(Structured Analysis Design Technique) ,the functional decomposition in order
to apply the FMECA method (Failure mode, effects and criticality analysis) and
the pareto diagram. This analysis allows us to
examine patterns of failures related to each component in order to have the
action to be taken.
4.1.
Structured
analysis of the packer
machine
The
cigarette packaging line has four machines: the packer which ensures the
entrance of cigarettes, pack it in 20 and wrap it to get packages; the over
wrapper which allows to wrap packages with cellophane paper; the cartridge use
which allows to group two packets in 10 interposed, and wrap them in cellophane
paper to get a carton of 10 packs. The cartoner which allows grouping 50
cartridges and packing in a carton. Figure 4 shows node A-0 of SADT model of
packer machine.
Figure 4: Node A-0 of SADT
model of packer machine
4.2.
FMECA
analysis of the packer machine
In this step we will present the
results of the study by describing different modes of failure with its causes
and its effects, so the values of the frequency of occurrence of risk, their
gravities, their no detection probabilities and their criticalities (Tables 1).
Table 1: FMECA analysis for the electrical cabinet
Life of the
components of the electrical cabinet follows an exponential distribution (unpredictable
failure), and equipment whose life follows an exponential distribution should
not be the subject of a preventive maintenance so: the type of maintenance the
electrical cabinet needs is corrective maintenance with spare parts
availability in store.
Each machine in the packer
cigarettes line is studied separately to identify its failures using the FMECA
method.
4.3.
Pareto
diagram of the packer machine
A Pareto is performed to target
faulty components and thus to be a decision-making tool for the preventive
maintenance tasks to be selected
Figure 5: Pareto diagram of the industrial company
As shown in the figure 5: Zone A: 20% of
failures cause 80% of costs. Zone B: The 30% more failures cost only 15% more.
Zone C: the remaining 50% of failures relate to only 5% of the overall cost.
Our priority will be to the failures of Zone A.
In this part, we managed to implement
a preventive maintenance plan, available to the maintenance department to
improve the rate of return and reduce the cost of corrective maintenance of
packer cigarettes line.
5. CONCLUSION
During this work, SADT method, FMECA study and Pareto
diagram are carried out on a cigarette packer line of a plant in order to
improve the maintenance function. Our studies begin with a decomposition of the
cigarette packer line based on the functional analysis in order to achieve
functional decomposition to identify the components of each machine. Each machine in the chain is
studied separately to identify its failures by applying the FMECA method. A
Pareto is performed to target faulty components and thus to be a
decision-making tool for the preventive maintenance tasks to be selected. This
allowed us to propose a set of preventive actions for the most critical
components of each equipment on the line.
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