The IEC 61511 / ISA 84 Approach to Functional Safety

Mike Boudreaux

DeltaV SIS Brand Manager

Process industry environment

Process

Industry

Risk to personnel,

assets, environment,

business

Fines, lawsuits,

insurability

Public perception

Unplanned shutdowns

Economic downturn

Increased complexity

Aging / unskilled workforce

Increasing ROI drives yourprocess safety needs

FallPrevention

PersonalProtectiveEquipment

StructuralDesign

Ergonomics WorkSchedules

EmployeeTraining

MechanicalIntegrity

ManagementOf Change

Policies &Procedures

InherentlySafer

Design

FunctionalSafety

RiskAssessment s

FacilitySiting

Total Recordables

EmergencyResponse

SafetyAudits

Occupationalsafety

FallPrevention

PersonalProtectiveEquipment

StructuralDesign

Ergonomics WorkSchedules

EmployeeTraining

MechanicalIntegrity

ManagementOf Change

Policies &Procedures

Process safety

Personalsafety

InherentlySafer

Design

FunctionalSafety

RiskAssessment s

FacilitySiting

Total Recordables

EmergencyResponse

SafetyAudits

Process safety

EmployeeTraining

MechanicalIntegrity

ManagementOf Change

Policies &Procedures

InherentlySafer

Design

FunctionalSafety

RiskAssessment s

FacilitySiting

EmergencyResponse

SafetyAudits

Process safety

EmployeeTraining

MechanicalIntegrity

ManagementOf Change

Policies &Procedures

InherentlySafer

Design

FunctionalSafety

RiskAssessment s

FacilitySiting

EmergencyResponse

SafetyAudits

FunctionalSafety

Functional safety

IEC 61511

PFDavg

LOPA

RRF

SIS

HAZOP

SRS

PHA

IEC 61508

FMEDA

BPCS

SIL

SIF

Safety function

Process conditions What to do SIL

SIF #1 High level Drive output 1 1

SIF #2 High pressure Drive outputs 1 + 2 3

SIF #2

SIF #1

SIL 151%

SIL 232%

SIL 38%

SIL 41%

No SIL8%

Process Industry I/O by Safety Integrity Level

Source: Exida Safety and Critical Control Systems in Process and Machine Automation July 2007

PHA

• Identify hazards• Evaluate safeguards

SRS

• Define SIF’s• Define SIL for each SIF

Design

• Specify devices• Design architecture

Verify

• Verify SIL meets SRS

PFDSIF1 = PFDPT-101 + PFDlogic solver + PFDFV-101

SIF #1

FV-101

Logic solver

PT-101

Optimized process reliability • Optimal safety integrity and availability• Meet the specific needs of the process

Flexibility to meet project needs• Staged implementation• Phased maintenance/testing

Reduced engineering and complexity• Simplify and standardize• Reduction of over-engineered designs• Isolation of process equipment

Easier regulatory compliance• Simplified management of change• Practical document management