Reliability Maintenance Engineering Day 2 session 1 Concepts and Software
Three day live course focused on reliability engineering for maintenance programs. Introductory material and discussion ranging from basic tools and techniques for data analysis to considerations when building or improving a program.
3. Objectives
• Recognize vulnerabilities in a system and
reduce risk
• Fault Tree Analysis and Block Diagrams
• Using simulation to improve decision making
• Using simulation options (policies, pools &
resources)
• Combining life distributions with life stress
relationships
4.
5. Discovery of Risks
• What could go wrong?
• What has gone wrong?
• Analysis
• Testing
12. FTA Construction
1. Define the fault condition, and write down the top level
failure.
2. Using technical information and professional judgments,
determine the possible reasons for the failure to occur.
3. Continue to break down each element with additional gates
to lower levels.
4. Finalize and review the complete diagram. The chain can
only be terminated in a basic fault: human, hardware or
software.
5. If possible, evaluate the probability of occurrence for each of
the lowest level elements and calculate the statistical
probabilities from the bottom up.
What is Fault Tree Analysis, by Simha Pilot, Quality Progress, March 2002
13. Reliability Block Diagram
• Reliability Block
Diagrams (RBDs) are
graphical
representations of the
components of the
system and how they
are reliability-wise
related
--Reliasoft.com
18. Blocksim Simulation
• An airline does annual
inspections of vests
• Replace faulty vests
only
• Vests fail with Weibull
distribution – beta 2.55
and eta 6.89 years
• Should we change the
inspection interval?
29. Monty Carlo Methods
• Failure mechanism
models
• Empirical models
• Use stress and
environment models
30. Monte Carlo
1. Define a domain of
possible inputs.
2. Generate inputs
randomly from a
probability distribution
over domain.
3. Perform a deterministic
computation on the
inputs.
4. Aggregate the results. Area of Circle = π / 4
Area of Square
31. Example
• 30 known failure
mechanisms
• Distribution of use and
environmental stresses
• Models to predict
failures
34. Summary
• Recognize vulnerabilities in
a system and reduce risk
• Fault Tree Analysis and
Block Diagrams
• Using simulation to
improve decision making
• Using simulation options
(policies, pools &
resources)
• Combining life distributions
with life stress relationships
Fault Trees &
Block Diagrams
Editor's Notes
Recognize vulnerabilities in a system and reduce risk
Balance between investment and value
FTA and RBD-
Balance between investment and value
Blocksim simulation
Balance between investment and value
Simulation options – policies, etc.
In this analysis, the relays are reliability-wise identical; however, their position within the diagram matters. This is best illustrated by the reliability importance plot shown next. As you can see, a specific relay failure affects the system differently due to its position within the system. Specifically and in order of importance, the greatest impact is if relay 2 or 5 fails, followed by relay 4 or 3 and then by relay 1 or 6.
Balance between investment and value
Simulation distributions and environment/assembly variation
<image of multiple distribution into black box and an output distribution>
For example, consider a circle inscribed in a unit square. Given that the circle and the square have a ratio of areas that is π/4, the value of π can be approximated using a Monte Carlo method:[3]Draw a square on the ground, then inscribe a circle within it.Uniformly scatter some objects of uniform size (grains of rice or sand) over the square.Count the number of objects inside the circle and the total number of objects.The ratio of the two counts is an estimate of the ratio of the two areas, which is π/4. Multiply the result by 4 to estimate π.