RS 523 Training Seminar
Application of Fault Trees in Reliability, Maintainability
and Risk Analysis

RS 523 discusses the application of fault trees for risk (safety) analysis and system reliability/maintainability analysis, with hands-on practical examples using ReliaSoft’s fault tree analysis software (BlockSim). Topics include fault tree construction/analysis, advanced fault tree gates, common cause failures, minimal cut sets, load sharing, standby, preventive maintenance and availability analysis.

The course presents concepts and software tools that you could use to help your organization:

• Identify vulnerabilities in a system and determine the most effective ways to reduce the risk.
• Expand upon traditional fault tree capabilities to achieve other system analysis objectives, such as identifying the most effective ways to improve a system design and using simulation to obtain maintainability metrics that support decision-making.

Course Outline

Theory and Principles Coverage

Introduction to Fault Tree and System Reliability Analysis

• Defining a system.
• Viewing a system as a collection of components and/or component failure modes.
• Overview of Fault Tree (FT) analysis.
• Origins and benefits of FT Analysis.
• Building blocks of FT.
• Steps to constructing a FT.
• Some rules and conventions

Types of Events, Elementary FT Gates and their Analytic Quantification

• Types of events (basic, house, undeveloped, conditional).
• OR gate.
• AND gate.
• Inhibit gate.
• Voting gate.

Introduction to Time Dependent Fault Trees

• Traditional vs. BlockSim Fault Tree events.
• Using distributions in addition to fixed probabilities.
• Inclusion of "used" components in modeling.
• System reliability metrics:
  • Obtaining a system pdf.
  • Derivation of functions of interest: system failure rate function, system MTTF, etc.
• Expanding the classical voting OR gate.

Advanced FT Gates and Features

• Traditional vs. BlockSim Fault Tree gates.
• Load sharing gate:
  • Combining life distributions with life-stress (load) relationships to describe dependency effects.
  • Basic load sharing gate.
  • k-out-of-n load sharing gate.
• Standby gate:
  • Energized and quiescent failure distributions.
  • "Hot," "Warm" and "Cold" standby definitions.
  • Switching (perfect or imperfect switching, with delays, retries and switch quiescent failure probabilities).
  • k-out-of-n-plus-M standby configurations.
• Sequence enforcing gate
• Priority AND gate
• Encapsulation (subdiagram blocks).
• Event Mirroring.

Minimal Cut Sets and Common Cause Failures

• Definition of Minimal Cut Sets
• Obtaining Minimal Cut Sets
• Using minimal cut sets to model complex configurations
• Definition of common cause failures
• Treating common cause failures

Identifying Opportunities

• Identifying importance of components, subsystems (and or modes) and their overall impact on system reliability.

Optimum Reliability Allocation

• Cost/Feasibility functions.
• Determining component reliabilities to achieve system goal.
• Specifying component reliabilities to achieve system goal.

Reliability Block Diagrams

• Definitions
• Comparing Fault Trees to RBDs
• RBD equivalents to all types of Fault Tree gates
• Advantages of RBDs over Fault Trees

Introduction to Discrete Event Simulation

Introduction to Repairable Systems Analysis: Fundamentals of Maintainability and Availability

• Traditional vs. BlockSim Fault Tree gates.
• Repair and downtime distributions and metrics.
• Introduction to renewal theory.
• Introduction to maintainability.
• Imperfect repairs (restoration factors).
• Availability definitions:
  • Instantaneous (Point) Availability
  • Mean Availability
  • Steady State Availability
  • Inherent Availability
  • Achieved Availability
  • Operational Availability

Introduction to Preventive Maintenance (PM) Principles

• When does "Preventive Maintenance" make sense?
• The fallacy of "Constant Failure Rate" and "Preventive Replacement."
• Quantifying preventive vs. corrective replacement strategies.
• Determining optimum PM intervals.
• Modeling effects of PM actions.

Advanced Simulation Options: Using Policies, Pools and Resources

• Adding Crews to the analysis.
  • Probabilistic elements.
  • Crew costs.
  • Crew utilization metrics and bottlenecks.
• Adding Spare Part Pools (Depots) to the analysis.
  • Probabilistic elements.
  • Spare part inventory management, costs.
  • Spare utilization metrics and bottlenecks.
  • Standard, on-condition and upon emergency spare part provisioning with associated costs and probabilistic delays.
• Utilizing "Corrective," "Preventive" and "Inspection" actions with associated policies.
  • Corrective actions, "Immediate" or "Upon Inspection" (hidden/discovery).
  • Inspections based on system time, component age and/or other system events (e.g. similar component failure elsewhere in the system).
  • PM actions based on system time, component age and/or other system events (e.g. similar component failure elsewhere in the system).

Visualizing and Improving System Availability

• Looking at common metrics (MTBF, MTBDE, MTBE, AX, etc.) and charts.
• Additional (new) metrics for identifying opportunities in repairable systems:
• RS-FCI (ReliaSoft's Failure Criticality Index).
• RS-DECI (ReliaSoft's Downing Event Criticality Index).
• FRED reports.

Including Costs in the Analysis, Introduction to Life Cycle Cost Analysis

• Determination of the probabilistic costs associated with system operation.
• Sample financial analysis.
• Throughput Analysis.

Computer Hands-On Section

BlockSim Software Familiarization

• Introduction to and familiarization with BlockSim.
• Creating models in BlockSim that apply all of the above principles.

Hands-on Workshop, Examples

• Individually work through detailed examples with step-by-step instructions to complete sample analyses.

Group Case Studies

• Using realistic cases (described in an objective statement), determine how to set up and analyze each case in a team environment.