▪ Part 1 – Functional Safety

▪ Part 2 – Case study (Application of

Functional Safety)

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▪ Question – Why Functional Safety?

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Source – Risk Management Model (Nertney Wheel, Bullock 1979)

▪ Question – How does this help?

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▪ Definition (AS61508.0)

▫ Freedom from unacceptable risk of –

▪ Economic / business losses, and/or

▪ Physical injury, and/or

▪ Environmental sustainability.

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▪ Objectives

▫ Improve WHSE and economic

performance

▫ Provide a risk-based approach

▫ Compliance with legislation

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▪ Background

▫ Functional Safety gained traction in

the 1980’s (UK, USA, Germany)

▫ IEC v’s ISO

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▪ Buncefield

▫ 40 people injured

▫ $1.6 Billion

▫ “Shutdown

systems failed to

operate.”

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▪ Bhopal Disaster

▫ 8000 people died / 500,000 injuries

▫ “The safety systems failed to prevent /

control the toxic gas leak.”

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Source –“Out of Control: Why control systems go wrong and how to prevent

failure”, U.K. Health & Safety Executive, 1995

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Source – AS61508.1:2011 Functional safety of electrical / electronic /

programmable electronic safety-related systems

▪ What about mining in Australia?

▪ How do we compare to other

industries?

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▪ In Australia –

▫ Started adopting these standards in

the late 1990’s

▫ Harmonisation, Legislation, Australian

Standards

▫ NSW has led the introduction of these

practices 13

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▪ DRAFT Work Health and Safety (Mines)

Regulation 2014

▫ (m) that any electrical safeguards provided

to control the risk from both electrical and

non-electrical hazards have a safety

integrity sufficient for the level of risk being

controlled

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▪ General comments –

▫ Application of functional safety?

▪ Overly cautious

▫ Understanding of functional safety?

▪ Mixed

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▪ General comments (cont.) –

▫ Cost benefit analysis?

▪ Benefits not fully realised (E.g.

Safety improvements, productivity

gains)

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Source –“Out of Control: Why control systems go wrong and how to prevent

failure”, U.K. Health & Safety Executive, 1995

▪ Background

▫ Design and construct an underground

high voltage substation

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▪ Sample specifications

▫ The designer shall be responsible for completing all

necessary Functional Safety activities, in accordance

with AS61508, AS61511, AS4024, ISO13849.

▫ The designer shall use components that are listed in

the site’s preferred equipment list AND design an

Emergency stop circuit that meets the requirements

of SIL 2.

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Source – AS61508.1:2011 Functional safety of electrical / electronic /

programmable electronic safety-related systems

▪ Objective

▫ Develop a level of understanding of

the substation and its environment

(physical, legislative etc.).

▪ Comment

▫ We generally do this well (E.g. AFE) 22

▪ Objectives

▫ Determine the battery limits of the

substation and specify the scope of

the hazard and risk analysis

▪ Comment

▫ This stage was re-visited 23

▪ Objective

▫ Determine the hazards, hazardous

events and hazardous situations

relating to the substation and its

control system (in all modes of

operation) for all reasonably

foreseeable circumstances

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▪ FMEA

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▪ Risk Graph

▪ Objective

▫ Develop the specification for the

overall safety requirements, in terms

of the overall safety functions

requirements and overall safety

integrity requirements

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▪ Operational Manual

▪ Maintenance Manual

▪ Installation and Test Plans

▪ Commissioning Plans

▪ Training Plans

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▪ Hardware / Software design

▪ System architecture

▪ Systematic fault avoidance

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▪ Design

Validation

▪ Operational efficiency gain

▫ Section Isolator fitted upstream of

substation

▪ Design did not meet SIL target

▫ Emergency Stop function did not meet

SIL 2 requirements 32

▪ Solution

▫ Cost benefit analysis

▫ Conduct quantitative analysis (E.g.

LOPA), consider other risk reduction

measures and determine total level of

risk reduction

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Zero Risk (R=0) Substation Risk (R=CxL)

Tolerable Risk

SRCF (SIL 2)

SRCF (SIL 1)

SRCF (SIL 1)

▪ Additional benefits

▫ Cost control (known inputs and a

controlled output)

▫ Increased communication between

the end-user and the designer/OEM

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