Design & Evaluation of Safety Instrumented Systems

Major incidents at home and overseas have taught us a lot about risk and loss prevention. We are slowly turning hindsight into foresight, examining the causes of incidents to find ways to prevent similar occurrences. There has been, and still is, a resistance to change, but there is a gradual acceptance that designing for safety can also be cost-effective.

Only recently in the process industry have there been internationally accepted standards to provide guidance on the design and implementation of safety instrumented systems. These standards are performance based rather than prescriptive, and outline what needs to be done in the form of a safety lifecycle. This workshop takes you through the safety lifecycle, and at each step describes how to fulfill the requirements of the standards.

Day 1

Introduction

Disasters – what went wrong, what can we learn? How can we prevent them?

§         Standards IEC 61508, IEC 61511, ISA 84.01

§         Philosophy of Safe Design

§         Safety Lifecycle

§         Safety Instrumented Function (SIF)

§         Safety Integrity Level (SIL)

§         Exercise

Risk Management

How can we represent risk?

§         Components of Risk – Frequency & Severity of Consequence

§         Consequence – Injury, Environment, Economic

§         Risk Matrix and Risk Graph

§         Tolerable Risk

§         Risk Reduction

§         Exercise

Process Risk

How can we reduce process risk?

§         Incidents – Causes and Consequences

§         Preventative Controls (reduce the frequency)

§         Mitigative Controls (reduce the consequence)

§         Bow-Tie diagrams illustrate the risk reduction process

§         Exercise

Day 2

Introduction to the Safety Lifecycle

How can we make sure we get it right?

§         Phases of the Safety Lifecycle

§         Activities within each phase

§         Exercise

Reliability

How can we measure reliability?

§         Definition of Terms

§         Probability

§         Failure Modes – Safe and Dangerous

§         Fault Tree Analysis (FTA)

§         Reliability Block Diagrams (RBD)

§         Markov Analysis

Day 3

Analysis Phase

Where does the information come from?

§         Determination of Tolerable Risk

§         Hazard Identification

§         Risk Analysis (frequency & consequence)

§         Identifying Safety Instrumented Functions

§         Determining Safety Integrity Level - Layer of Protection Analysis (LOPA)

§         Writing the Safety Requirement Specification

§         Exercise

Day 4

Realization Phase

How do we design the system we need and verify the result?

§         System Technologies – Relay, Solid State, Programmable

§         Subsystems – Sensor, Logic Solver, Final Element

§         Architectures – 1oo1, 1oo2, 1oo2D, 2oo2, 2oo3, 2oo4

§         Sensor Subsystems

§         Final Element Subsystems

§         Effects of Field Devices on SIF Performance

§         Common Cause – Separation, Diversity, Physical Environment

§         SIL Verification – PFDavg and Architectural Constraints

§         Exercise

Other Design Considerations

What else do we need to think about?

§         Power

§         Grounding

§         Bypasses

§         Interfaces

§         Alarm Management

Day 5

Operation Phase

How do we make sure we maintain safety integrity?

§         Factory Acceptance Testing (FAT)

§         Commissioning

§         Maintenance

§         Decommissioning

§         Documentation

§         Management of Change (MOC)

§         Exercise

Design Exercise

A Safety Instrumented Function – from start to finish

§         Identify a Safety Instrumented Function

§         Determine the required SIL of the Safety Instrumented Function

§         Write the Safety Requirement Specification for the Safety Instrumented Function

§         Design the Safety Instrumented Function

§         Verify that the design meets requirements

§         Document the results