rcm tools histogram pareto chart cause and effect diagram fmea
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RCM ToolsRCM Tools
Histogram Pareto Chart Cause and Effect Diagram FMEA
HistogramHistogram
A histogram is a of a bar chart representing the frequency of an entire data grouped into evenly spaced category. It can be viewed as a graph of class versus frequency. It used for the following:– Organizing data.– Spotting variation in data.– Identifying data distribution.
Frequency DistributionFrequency Distribution
Let us examine the following data for the demand in weeks for the last 30 orders of computers/drug.
15 6 21 15 12 9 18 6 9 9 18 6 12 15 3 21 6 18 12 9 15 9 6 18 12 12 6 18 12 12 n = 30
Frequency DistributionFrequency Distribution
The Frequency Dist. Is Table that provide classes and frequency (number of occurrences in the class). For the demand data it is No. Class Frequency 1 1 – 4 | 1
2 5 – 8 |||||| 63 9 – 12 |||||||||||| 124 13 – 16 |||| 4
5 17 – 20 ||||| 5 6 21 – 24 || 2
30
1 6 12 4 5 2 4.5 8.5 12.5 16.5 21.5 24 Range
The graph of class versus frequency called The graph of class versus frequency called HistogramHistogram
Frequency
1 6 12 4 5 2 20.5 24
PercentilesPercentiles
Concept of DistributionConcept of Distribution
Histogram ShapesHistogram Shapes• While the number of shapes that a histogram ca
take is unlimited, certain shapes appear often then others.
• Drawing a line that connects the edges of the bars in a Histogram forms a curve. We can make certain inferences about the data from the shape of the curve.
Distribution
Histogram QuestionHistogram Question
Does the shape of the histogram tells something?
If the answer is yes how? How do we assess variability from
the histogram?
Use of HistogramUse of Histogram After you have created a Histogram, it will
take one of five shapes:
Exponential : Failure is random
Use of HistogramUse of Histogram
Normal Distribution:
Use of HistogramUse of Histogram
Positively Skewed:
Negatively Skewed: Preventive maintenance
Use of HistogramUse of Histogram
Bi-Modal Distribution:
Multi-Modal Distribution:
1, ½, ¾, 2, ½, ½, 1, 1, ¾, 3, 1, ¾ 1, ¾, 2, 8, 3, ¾, ½, 8, 4, 7, 10, ¾ 2, ½, 1, ½, 30, 1, 2, 1, 50, 6, 3, 3 5, 4, 6, 5, 72, 2, 4, 2, 3
Table 1 : Grinder downtime in hours for the last three months (rounded to the nearest half hour)
Exercise in Class
Pareto ChartPareto Chart
Pareto chart/diagram is a bar chart that categories possible causes of problem areas and organize them in order of decreasing frequency/cost/impact. It is a problem solving tool used to separate the “Major” few from the trivial “many”. It can be used for:
– Identify important causes for bad quality
– Prioritizing allocation of resources.
Example on Pareto ChartExample on Pareto Chart
Below is a check sheet that lists type of injury in a factor
Type of injury Tally Frequency Fingers (F) 1111 1111 1111 1111 111 23
Eyes (E) 1111 1111 9
Arms (A) 1111 1111 111 13
Leg (L) 1111 5
Total 50
Pareto ChartPareto Chart
5
5
10
15
20
25
F A E L
Pareto Chart UsesPareto Chart Uses
Identifying major quality problems Identifying major unsafe acts Identify major causes of budget over run Identify major costs factors in a process Identify major reasons for not meeting
targets.. Many others.
Cause and Effect DiagramCause and Effect Diagram
It is a chart that relates the problem to its causes.
It’s objective is to identify causes of a problem
It is useful in sorting, interrelating and visualizing the causal factors influencing a particular problem
Cause-and-Effect DiagramCause-and-Effect Diagram
Figure11-10 in text
Effect
MaterialsMethods
EquipmentPeople
Environment
Cause
Cause
Cause
Cause
Cause
CauseCause
Cause
CauseCause
Cause
Cause
The steps of the CED are:
Decide the quality characteristic, and effect needed to be studied. This is usually a phenomena (effect) we need to improve and control. As an example not meeting production targets. (next Figure)
Write the effect on the right side. Draw a broad arrow from the left side to the right side
Write the main factors which may be causing the target miss, directing a branch arrow to the main arrow (Figure 7). Group the major possible causes into categories such as materials, equipment, methods of work, and measuring methods. Each category will form a branch as in the next Figure.
Missing Target
Equipment People Methods
Procedures Materials
Write on each of the side branches the detailed factors which may be regarded as the causes. These will be like twigs and on these write more detailed factors and so on. (see next figure)
Check to make sure that all causes are included in the diagram and the relationships are properly illustrated.
Mis
sin
g
Ta
rg
et
Procedure Methods
Lo
ng
Repair
Job Preparation
Transportation
Documentation
No
t cle
ar
Hard
to
use
Delay in reporting
Inspection Materials
Not structured
Temperature Fatique
Coolant
Ordering policy
Preparation
Lack of material
Equipment
Rotation
Str
uc
k
Un
ev
en
Does not tell situation
FMEA:FMEA: Failure Mode and Effects AnalysisFailure Mode and Effects Analysis
An important tool of RCM
FMEA DefinitionFMEA Definition
A procedure and tools that help to identify every possible failure mode of a process or product, to determine its effect on other sub-items and on the required function of the product or process. The FMEA is also used to rank & prioritize the possible causes of failures as well as develop and implement preventative actions, with responsible persons assigned to carry out these actions.
Failure modes and effects analysis (FMEA) is a disciplined approach used to identify possible failures of a product or service and then determine the frequency and impact of the failure.
FMEA definedFMEA defined
FMEA is a specific methodology to evaluate a system, design, process, or service for possible ways in which failures (problems, errors, risks, concerns) can occur
For each failure identified (known or potential), an estimate is made of its occurrence, severity and detection.
An evaluation is made of the necessary action to be taken
ASQC DefinitionASQC Definition
FMEA is an engineering technique used to define, identify, and eliminate known and/or potential failures, problems errors, and so on from the system, design, process, and or service before they reach the customer
ASQC 1983
PrerequisitesPrerequisites
All problems are not the same
The vital few as opposed to the trivial many The customer must be known
end user or downstream operation
The function must be known
The function, purpose, and objective of what is to be accomplished must be known
Prerequisites (cont’d)Prerequisites (cont’d)
One must be prevention oriented
Continuous improvement is the force that drives FMEA
Good FMEAGood FMEA
Identify known and potential failure modes Identifies the causes and effects of each
failure mode Prioritizes the identified failure modes
according to the risk priority number
(RPN = frequency x severity x detection) Provides for problem follow-up and corrective
action
Components that that help define Components that that help define the priority of failuresthe priority of failures
Occurrence
Severity
Detection
..
Occurrence is the frequency of the failure
Severity is the seriousness (effects) of the failure
Detection is the ability to detect the failure before it reaches the customer
FMEA and RCMFMEA and RCM
Specifying PM tasks without a good understanding of of failure mode and cause information is, at best, nothing more than a guessing game
FMEA play a vital role in the RCM process
How is FMEA performed?How is FMEA performed?
A good understanding of the equipment design and operation is an essential starting point
The FMEA process proceeds in an orderly fashion to qualitatively consider the ways in which the individual parts or assemblies in the equipment can fail. These are the failure modes that we wish to list.
......
Each Failure mode is then evaluated for each effect on
- the component itself (local effect)
- next higher level of assembly
- the top level of assembly or system
Fig 3.6 and Fig 3.8
....
When a well-executed FMEA is accomplished, a wealth of useful information is generated to assist
in achieving the expected product reliability
Breakdown
Duration Frequency Relative
Frequency 0 < t 1 1< t 2 2< t 3 3< t 4 4< t 5 5< t 6 6< t 7
t 8
20 6 5 3 2 2 1 6
44.44 13.33 11.11 6.67 4.45 4.45 2.22
13.33
Total 45 100.00
Table 2 : Frequency distribution for the downtime data in table 8.1
Downtime intervals
1 2 3 4 5 6 7 8
Figure 7
f
5
10
15
20
25
Frequency
Figure 5
GrinderTime
Figure 6
The steps of the CED are:
Decide the quality characteristic, and effect needed to be studied. This is usually a phenomena (effect) we need to improve and control. In our case it is the grinder downtime. (Figure 6)
Write the effect on the right side. Draw a broad arrow from the left side to the right side
Write the main factors which may be causing the grinder downtime, directing a branch arrow to the main arrow (Figure 7). Group the major possible causes into categories such as materials, equipment, methods of work, and measuring methods. Each category will form a branch as in Figure 7.
Figure 7
GrinderTime
Equipment Procedure Methods
Inspection Materials
Write on each of the side branches the detailed factors which may be regarded as the causes. These will be like twigs and on these write more detailed factors and so on. (Figure 8)
Check to make sure that all causes are included in the diagram and the relationships are properly illustrated.
Gri
nde
r
dow
ntim
e
Procedure Methods Long
Repair
Not slanded
Job Preparation
trasnsportation
Documentation
Not clear Hard to use
Delay in reporting
Inspection Materials
Not structured
Rise in temperature
Coolant
Leakage
Does not come out
Wet
Polishing grinder
Equipment
Rotation
Struck
Uneven
Does not tell situation
Figure 8
23
12
5
3
a b c d e
10
20
30
40
Number ofBreak downs
Figure 9