Are You Ready for an SIS?

What to do before starting on your SIS…and after it’s installed

March 24, 2009

Presenter: Mike Schmidt, P.E.

Principal Bluefield Process Safety

Principal Safety ConsultantEmerson Process Management

Are You Ready for an SIS?, ©2009Slide 2

Before starting on an SIS

Steps of the Safety Life Cycle and Why They Matter

SIFs and SIL AssignmentThe SRSAfter the SIS is installed

– a conversation

Are You Ready for an SIS?, ©2009Slide 3

The Safety Life Cycle

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Analysis

Implementation

OperationProcess Design

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Are You Ready for an SIS?, ©2009Slide 4

The Safety Life Cycle

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Analysis

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OperationHazard Identification

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Are You Ready for an SIS?, ©2009Slide 5

The Safety Life Cycle

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Analysis

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OperationRisk Assessment

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Are You Ready for an SIS?, ©2009Slide 6

The Safety Life Cycle

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Analysis

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Operation

Risk Tolerance Criteria Confirmation

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Are You Ready for an SIS?, ©2009Slide 7

The Safety Life Cycle

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Analysis

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Risk Reduction Allocation

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Are You Ready for an SIS?, ©2009Slide 8

The Safety Life Cycle

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Analysis

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OperationSafety Function Definition

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Are You Ready for an SIS?, ©2009Slide 9

The Safety Life Cycle

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Analysis

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OperationSafety Function Specification

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Are You Ready for an SIS?, ©2009Slide 10

The Safety Life Cycle

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Analysis

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OperationReliability Verification

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Are You Ready for an SIS?, ©2009Slide 11

The Safety Life Cycle

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Analysis

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Operation

Mechanical/ Electrical/ Structural Detailed Design

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Are You Ready for an SIS?, ©2009Slide 12

The Safety Life Cycle

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Analysis

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OperationSoftware Configuration

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Are You Ready for an SIS?, ©2009Slide 13

The Safety Life Cycle

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Analysis

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Operation Equipment Build

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Are You Ready for an SIS?, ©2009Slide 14

The Safety Life Cycle

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Analysis

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Operation

Factory Acceptance Testing

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Are You Ready for an SIS?, ©2009Slide 15

The Safety Life Cycle

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Analysis

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OperationConstruction/ Installation

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Are You Ready for an SIS?, ©2009Slide 16

The Safety Life Cycle

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Analysis

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OperationSite Acceptance Testing

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Are You Ready for an SIS?, ©2009Slide 17

The Safety Life Cycle

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Analysis

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OperationValidation

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Are You Ready for an SIS?, ©2009Slide 18

The Safety Life Cycle

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Analysis

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OperationTraining

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Are You Ready for an SIS?, ©2009Slide 19

The Safety Life Cycle

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Analysis

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OperationPre-Startup Safety Review

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Are You Ready for an SIS?, ©2009Slide 20

The Safety Life Cycle

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Analysis

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OperationOperation

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Are You Ready for an SIS?, ©2009Slide 21

The Safety Life Cycle

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Analysis

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Are You Ready for an SIS?, ©2009Slide 22

The Safety Life Cycle

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Analysis

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OperationProof Testing

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Are You Ready for an SIS?, ©2009Slide 23

The Safety Life Cycle

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Analysis

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OperationInspection

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Are You Ready for an SIS?, ©2009Slide 24

The Safety Life Cycle

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Analysis

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OperationMaintenance

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Are You Ready for an SIS?, ©2009Slide 25

The Safety Life Cycle

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Analysis

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OperationManagement of Change

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Are You Ready for an SIS?, ©2009Slide 26

The Safety Life Cycle

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Analysis

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De- commissioning

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Are You Ready for an SIS?, ©2009Slide 27

The Analysis Phase

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Implementation

Operation

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Analysis: Before starting on an SIS

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Are You Ready for an SIS?, ©2009Slide 28

Process Design

Process Design has the greatest influence on the need for an SIS

This includes all of the main Process Design Documents

Conceptual DesignPFDs and Heat/Material BalancesP&IDs

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Are You Ready for an SIS?, ©2009Slide 29

Hazard Identification

Hazards are identified during the Process Hazard Analysis (PHA)

Preliminary PHAs“What If?”Checklist

Detailed PHA HazOp (Hazard Operability Review)

Are You Ready for an SIS?, ©2009Slide 30

HazOps: Some tips

Tip 1. Take care in identifying the cause. If it’s a deviation, that normally means a failure.

Tip 2. Some HazOp methods prompt an identification of frequency. If this is done, do it consistently…with or without safeguards, with or without recommendations, with or without SIFs

Are You Ready for an SIS?, ©2009Slide 31

Risk Assessment

Intolerable Risk

Negligible Risk

Consequence

Lik

elih

ood

Risk = Consequence x Likelihood

Are You Ready for an SIS?, ©2009Slide 32

Risk Assessment

Consequence AnalysisOffsite Consequence Analysis (OCA)Quantitative Risk Analysis (QRA)

Likelihood AnalysisLayers of Protection Analysis (LOPA)

Are You Ready for an SIS?, ©2009Slide 33

How much risk is too much?

Intolerable Risk

Negligible Risk

Consequence

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ood

Compare: Risk against Risk Tolerance Criteria

Risk Tolerance Criteria

Are You Ready for an SIS?, ©2009Slide 34

Risk Tolerance Criteria

May come from any of several sourcesPlant policy Corporate policyIndustry benchmarks and guidelinesGovernment mandates

The United States does not set tolerable risk levels or offer guidelines.

Outside consultants should not decide for you what is tolerable

Are You Ready for an SIS?, ©2009Slide 35

ALARP: Levels in the UK

10-3 fatalities/ work-year (worker)

10-6 fatalities/ work-year (worker)

10-4 fatalities/year (public)

Intolerable Risk

Negligible Risk

ALARP or Tolerable Risk Region

10-6 fatalities/year (public)

Are You Ready for an SIS?, ©2009Slide 36

Factors to Consider

Number of facilitiesMulti-national or notSocietal expectations

Large, multinational companies tend to set levels consistent with international mandates, while smaller companies tend to operate in wider ranges and implicitly, at higher levels of risk

Are You Ready for an SIS?, ©2009Slide 37

Risk Reduction Allocation

When additional risk reduction is requiredNon-instrumented IPLs

Passive components: Dikes Blast walls Secondary containment

Active components: Relief devices Redundant equipment or installed spares

Instrumented IPLsControl loops within the BPCSSafety Instrumented Functions

Are You Ready for an SIS?, ©2009Slide 38

How much risk reduction?

Intolerable Risk

Negligible Risk

Consequence

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SIL: Difference Between Risk and Risk Tolerance Criteria

SIL Assignment

Are You Ready for an SIS?, ©2009Slide 39

Safety Function Definition

Non-SIS Safety Functions (IPLs):Scope definitionProject specification(This follows the normal project cycle)

SIS: SIF List SIL assignment

Note: SILs are assigned to functions, not to systems

Are You Ready for an SIS?, ©2009Slide 40

SIF List

Typically includesSIF TagHazard DescriptionSIL Assignment/Required PFDavgTrip conditions

Instrument tagsSet point and directionVoting

Trip actionsInstrument tagsTrip state

Are You Ready for an SIS?, ©2009Slide 41

Safety Function Specification

For an SIS, this is the Safety Requirements Specification – the SRS

Used to develop system quotesBasis of detailed designBasis of configuration

More extensive than a SIF List

Are You Ready for an SIS?, ©2009Slide 42

The SRS – §10.3.1

“These requirements shall be sufficient to design the SIS and shall include the following:”

A list of 27 bullet items followThe SIF List addresses five of them

Are You Ready for an SIS?, ©2009Slide 43

The SRS – §10.3.1

Other items includeSource of demand and demand rateProof test intervalsResponse time intervalsEnergize-to-trip or de-energize-to-tripMaximum allowable spurious trip rateOverrides/inhibits/bypassesResetsDangerous combinations

Are You Ready for an SIS?, ©2009Slide 44

Organizing an SRS

Suggested approachGeneral SIS RequirementsSpecific SIF RequirementsBasis of Design

Policies Procedures Documents Reports

Are You Ready for an SIS?, ©2009Slide 45

General SIS Requirements

Are You Ready for an SIS?, ©2009Slide 46

Specific SIF Requirements

Are You Ready for an SIS?, ©2009Slide 47

Reliability Verification

Two kinds of “SIL Calcs”SIL Assignment Calculations

Consequence Analysis Likelihood Analysis

SIL Verification Calculations Required by standards Use a combination of software

tools and custom calculations exida – SILVER (exSILentia) SIS-Tech – SilSOLVER

Are You Ready for an SIS?, ©2009Slide 48

Before starting SIS design

Process DesignHazard IdentificationRisk AssessmentRisk Tolerance Criteria ConfirmationRisk Reduction AllocationSafety Function DefinitionSafety Requirements SpecificationReliability Verification

Are You Ready for an SIS?, ©2009Slide 49

After the SIS is installed

Are there questions about:WitnessingProceduresResponsibility (Vendor or customer?)CertificatesFrequency Training after installation (Who

needs it? Who can operate?)

Are You Ready for an SIS?, ©2009Slide 50