Reliability Risk Assessment Ray Barlog, PE March 24, 2015 “Service Measured to the Standard” Cornerstone Electrical Consultants, Inc.

Safety and Reliability Both deal with uncertainty, aim to reduce undesired outcomes Safety mostly concerned with avoiding harm to humans Reliability most often concerned with reducing economic losses - $$ Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Risk - An event that has a negative consequence and has a probability of occurring (not an opportunity) Risk = Likelihood x Consequence Reliability Risk = Failure Probability x $$ Impact Reliability Risks are often not constant across time Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Risk Do We Want To………… Eliminate Risk? Reduce Risk? Manage Risk? Cornerstone Electrical Consultants, Inc.

Risk Management Process Identify Analyze Evaluate Respond Control Assessment Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Risk Assessment The process of identifying, analyzing, and evaluating, and prioritizing risks Cornerstone Electrical Consultants, Inc.

Some Reliability Risk Assessment Methods Functional FMEA Process FMEA Equipment FMEA Expected Value FMEA Fault Tree Analysis Qualitative Fault Tree What If Analysis Bow Tie Analysis RAM Modeling Stochastic Life Cycle Cost Concept FMEA Event Tree Analysis Layer of Protection Analysis Markov Analysis Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. 3 Reliability RA Tools Functional Failure Mode and Effects Analysis Bow Tie Analysis Reliability, Availability, Maintainability (RAM) Modeling Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. FMEA Probably the most common reliability risk assessment tool Structured method Best using team with diverse backgrounds Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. FMEA Came from Military Procedure MIL-P-1629, Procedures for Performing a Failure Mode, Effects and Criticality Analysis, dated November 9, 1949. FMEA used and improved by NASA in the 1960's to improve and verify reliability of space program hardware. Mil-Std-1629A used in the military and by commercial Used in the Nuclear Power Industry for evaluating design risks SAE J1739 - an FMEA standard used in the auto industry Cornerstone Electrical Consultants, Inc.

FMEA-asks the questions What is the intended function? How does it fail? ( failure mode ) How often do we expect the failure to occur? How severe are the effects? What are the potential causes of the failure? How likely is the onset of failure to be detected? Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Common Example Objective: Determine the most critical risk and its cause(s) for this boiler feed water system. Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Common Example If 2 pumps fail, both boilers trip Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Common Example P-1 P-2 P-3 Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Risk Rating Factors Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. FMEA Worksheet Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Bow Tie Analysis A simple graphical tool that shows the link between potential causes, preventive and mitigating controls, and consequences of a risk event Shows at a glance how risks are managed Can be purely qualitative or semi-quantitative Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Reason’s Swiss Cheese Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Generalized Bow Tie Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Example Risk Matrix Cornerstone Electrical Consultants, Inc.

Bow Tie-Common Example Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. RAM Model RAM: Reliability, Availability, Maintainability Reliability: Probability of surviving a given time interval without failure under given conditions Availability: Average % time a system is in a state to perform a function Maintainability: Probability of completion of a maintenance task in a given time interval Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. RAM Model A graphical and mathematical representation of system operation, dependency, and performance Most quantitative of the three methods presented Requires failure data, repair time data, and system operating logic Cornerstone Electrical Consultants, Inc.

RAM Model Building Block Series Cornerstone Electrical Consultants, Inc.

RAM Model Building Block Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. RAM Model-Example Cornerstone Electrical Consultants, Inc.

RAM Model-Typical Input Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. RAM Model Results Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. RAM Model Results Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Pros / Cons - FMEA Tedious, Time Consuming Requires robust risk matrix Doesn't handle redundancy or multiple failures well Doesn't handle dependencies well Doesn’t handle increasing failure rates well Structured, Thorough Easy to Learn Uses Group Knowledge Requires no special software Excellent for evaluating designs early in the process Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Pros / Cons – Bow Tie Quantifying risk requires modification Requires robust risk matrix Software recommended for good documentation Becomes complex with large systems Excellent risk management communication tool Easy to learn and interpret Uses group knowledge to develop Fairly quick to develop Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Pros / Cons – RAM Model Can be labor and $$ intensive for large systems Not easily understood by person not trained Requires special analyst skills for model building Quality of model depends on quality of data Quantifies risks for prioritization Estimates risks over time Handles dependencies, redundancy, special ops rules Evaluating “What Ifs” can be done quickly Cornerstone Electrical Consultants, Inc.

Cornerstone Electrical Consultants, Inc. Final Thoughts There is NO one best or universal method. Use the simplest method that can help you meet the objective of your assessment with the minimum investment of time and resources. Risk assessment alone is valueless- risks must be managed and that takes action. Cornerstone Electrical Consultants, Inc.

What are your questions? Cornerstone Electrical Consultants, Inc.