Transcript Document

Exploratory Data
Analysis
Approaches to
Reliability: Some
New Directions
Chris McCollin
Cornel Bunea
Maria Ramalhoto
Chris McCollin
The Nottingham Trent
University
• Involved in Reliability since
1976
• Worked as a reliability engineer
for 3 major aerospace
companies
• Consultancies/Training:
Nuclear, Rail, Commercial
• Involved with Q&RE paper for
Engineering Council for last 8
years
• RSS representative for BSI
• ENBIS Reliability Website
coordinator
Areas of Common SME
Problems
• Effect of short-term
management outlook on
reliability
• Lack of time, manpower for
analysis and improvement
• Lack of expertise, resources
• OEM dependency, meeting
requirements only
• Lack of knowledge retention
FMEA/FRACAS
Comparison
FAILURE
FMEA
S
E
V
O
C
C
D
E
T
R
P
N
RECOMMENDED
ACTIONS AND
DATE
Excessive
Gap between
damper
Bracket and
assembly
Damper out of
position.
Effect: Reject
Assy. Customer
has difficulty
assembling
Failure: Assy not
linished.
Effect: customer
Unable to use.
Reject assembly.
Failure:
Incomplete
linishing
Effect: customer
unable to use.
Reject assembly.
Effect: Premature
Failure in service.
4
6
4
96
None
(26/09/95)
Excessive
weld
(material)
Faulty weld
of
Nut.
Burn through
at filter neck
Incorrect
filter
Fitted
Plating on
Filter
Neck
missing.
Filter loose
Notch being
Missed
The FMEA for
this
Operation
does
not
Consider this
failure.
But blowholes are
considered.
YES: Effect:
Possible damage
….
4
….
3
3
3
-
-
….
9
….
3
ACTIONS
TAKEN
AND
DATE
None
None
(25/09/95)
None
….
3
….
36
4
36
None
(25/09/96)
None
-
-
-
-
….
3
….
81
………………..
monitor alarm
performance
31/08/94
……….
None
8
4
7
224
No FMEA for
Operation 92.
-
-
-
FMEA for fitting
Filter did not
consider this
failure mode or
effect.
YES: Effect was
severe
Customer
dissatisfaction.
-
-
8
2
08/05/96
None.
Last FMEA
update
08/05/96
-
Poka-Yoke
delivery of Filter,
to link Filter selection
with notching.
(12/07/94)
-
-
-
-
-
4
64
None
None
-
Problem Solving
Requirements
• Structured approach, easy to
use, computer/web based
• Developing hypotheses to
answer (inter-related) problems
over life cycle of a product(s)
• Using past/present information
across diverse databases
• Central storage access on-line
Flowchart of Problem
Solving Database
Issues Site:
Examples of
Hypotheses
Statistical
Flowcharts +
Packages
Past Solutions
Database: Case
studies, Reports
Discussion Site:
Past Issues: Papers
Existing Data
Repository
Methods Site
Recommendations
Site
Problem Solving
Procedure
• 1. Layout of Scenario
Problem: environment,
conditions, flowcharts, etc
2. State Null Hypothesis
Consider Problem effect across
all interfacing levels leading
to possible (multiple) causes
(flowchart). Address
complexity of problem,
whether there is more than
one. Alternative hypotheses
listed. Costing issues
addressed.
• 3. Analysis Flowchart
Failure records, statistical
flowcharts – alternative
research methodologies
identified
• 4. Risks
Previous works, arguments,
risk assessments available?
• 5. Problem solving tools,
Working model
Physical assumptions,
background theory – design
equations, physics, use of C
and E (appropriate method),
5 Whys, brainstorming, Fault
tree, FMEA, MORT, Design of
Experiments, etc
• 6. Bias, Rejection criteria
for null hypothesis
• 7. Hard Collection,
analysis
Analysis: Questionnaires,
Engineering analysis:
e.g. materials test,
statistical analysis, etc
• 8.Conclusions Accept/reject
hypothesis
based
on
model/assumption/bias or change
hypothesis (go to step 2)
• 9.
Recommendations
for
corrective action Change to
schedules, procedures, PokaYoke
devices,
etc.
Standardisation.
• 10. Feedback/Feed forward
To next problem, to database for
dissemination and comment
Job Description of
Facilitator
• Aids the problem solving activity
• knowledge and experience of the
problem solving approach, team
dynamics
• knowledge of what expertise is
required for a particular problem and
who can provide it (available from
personnel files)
• has the ability to aid incorporation of
diverse knowledge
• can mediate in issues arising from
differing viewpoints
• suggest methods of solution
(qualitative and/or quantitative)
• provide guidance of the holistic
view of the company strategic plan.
No Fault Found
(NFF)
Reason: not been installed on
the aircraft and since the
classification ‘Missing’ did not
exist in the failure definitions
inventory (because ‘Missing’
was not a failure category)
the nearest most appropriate
category was NFF. In this
case, NFF is a misleading
classification because it may
indicate that a failure did not
exist in the first place.
We should stratify the problem
by disseminating our data
into
more
appropriate
categories and discuss them
individually.
No Fault Found
Plenty of Reasons:
No classification for what has
been found
Replace everything (saves time)
Interdependencies between
systems, e.g. common power
supplies
Loading
Working at limits of operation
Intermittent Wiring faults
Ground test conditions cannot
reproduce latent defect
Example Hypothesis
• Aircraft operating, external
temperatures and vibration
affecting systems
• Time lag of thermal shocks 10º
a minute in chamber but system
takes longer
• Rise in temperature causes
expansions – effects on
interconnections (transistors –
pnp,npn; solder: DC wetting;
may create micro-cracks
• (DC wetting is passing of DC
current over dry joint creates an
increase in heat, resulting in the
joint melting back together) –
cannot locate fault
Continued
• Possibly surfaces become more
elastic, cracks open quicker
over time allowing
contamination
• Cracks will close again, only
long term exposure to adverse
conditions may produce
identifiable failure
• Road Surface testing, DOE
(long term effects),
FEA/Thermal effects,
compatible materials, HALT,
Simulation within CAD of
thermal/vibration effects
Step 1.
The
environment,
the
operating conditions and
the
problem
and
associated
interrelationships should be
outlined in sketch form
(e.g. an Affinity diagram)
to highlight areas where
a possible solution may
lie. Flowcharts, diagrams,
previous analyses should
be
made
available
(preferably on-line).
Step 3. Structure
• Approaches to identifying
structure can be split into two
separate areas; where extra
explanatory information is
available and where it is not.
Multivariate Data
Analysis Flowchart
Description of physical and functional
system
Check for missing or corrupt data
Discriminant analysis
Multivariate analyses for determining
structure - PCA, correspondence,
cluster, correlation, distance
measures, etc
EDA
Modelling time metric data - time
series, PHM, PIM, GLIM, regression
Data Analysis
• Hypothesis 1: The stratum of a
number
of
sockets
is
homogeneous. The alternatives
are that times are clustered (nonindependence)
and/or
inhomogeneous
• Hypothesis 2: The processes are
independent against clustering
(process identified as “colored”)
• Hypothesis 3: The colored process
is stationary
• Hypothesis 4: The process is
“color blind competing risk”
• Hypothesis 5: The process is
stationary competing risk
• Hypothesis 6: The process is
renewal competing risk
• Hypothesis 7: The process is
Poisson competing risk and under
the alternative hypothesis, H1:
Renewal process.
Org
NUKE
M
EDA
M
graph
Trend
Test
No
trend
found
NT
Serial
Correl
ation
NT
Distrib
ution
Assum
ptions
Other
Analy
sis
VTT
JRC ISPR
A
INTER
ATOM
TT
Kapla
n
Meier
plot
No
trend
found
GF
TT
Trend
found
CF
TD
NT
Log
rank
WR
LR
NT
NT
EX
WE
GF
EX
WE
GF
See
EDA
above
OS GF
EX
WE
EX
WE
OU
CE
OU
CE
Trend
SC
OU
CE
OU CE
OU
AV
ENE
A–
VEL
Step 5
A repository of tools should be
kept with examples of how
they
may
be
used
in
conjunction with each other.
The repository may contain
examples of the 7 quality
tools, the 7 new quality
tools,
brainstorming,
Management Oversight and
Risk Tree (MORT), Failure
Modes and Effects Analysis
(FMEA), radar charts, etc.
SPEG CLEAN UP
ATTRIBUTE
LOW BEAM CURNT
CRYO COMPRESS
D.P CALIBRATION
FLAG CHNG RLY
LEAK VALVE
AUTO SETUP
PARTICLES
PROCESS ENG
EQUIP.ENG
TERM. COMMS.
RUN SPEED
DATALOCK
SOURCE POWER
CRYO PUMP
FACILITIES
INTERRUPTIONS
POWER CUT
VACUUM CONT
EXTN/SUPN ELEC
MECH PUMP
WAFER BRK
GAS REGULATOR
GAS CHANGE
B/LINE VACUUM
SLIDING SEALS
WFR. HANDLING
E/STN VACUUM
UNSTABLE BEAM
H.V. STABILITY
REGEN
SOURCE PRESS.
P.M
SPEG SET UP
ELEC. FLOOD
PROCESS CAL
SOURCE CHANGE
HOURS DOWNTIME
MACHINE INTERVENTIONS
70
60
50
40
30
20
10
0
• The Pro-Enbis project is
supported by funding under
the European Commission's
Fifth Framework 'Growth'
Programme via the Thematic
Network
"Pro-ENBIS"
contract reference: G6RT-CT2001-05059.
• The authors (i.e., Pro-ENBIS) are
solely responsible for the content
and it does not represent the opinion
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is not responsible for any use that
might be made of data therein