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Transcript of 24316769 Safety Instrumented System
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Safety Instrumented Systems
ANGELA E. SUMMERS, PH.D., P.E.
SIS-TECH Solutions, LLC
Were Proven-in-Use.
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Terminology
Critical Control Systems
Safety Shutdown Systems
Protective Instrumented Systems
Equipment Protection Systems
Emergency Shutdown Systems
Safety Critical Systems
Interlocks
Safety Instrumented Systems
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What is a Safety Instrumented System (SIS)?
An SIS is designed to:
respond to conditions in the plant which may behazardous in themselves or,
if no action was taken, could eventually give rise to ahazard, and
to respond to these conditions by taking definedactions that either prevent the hazard or mitigate thehazard consequences.
Input ---- Logic Solver ---- Output
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Examples of Safety Instrumented Systems
High fuel gas pressure furnaceinitiates shutdown of main fuel gasvalves.
High reactor temperature initiatesfail open action of coolant valve.
High column pressure initiates failopen action of pressure vent valve.
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OSHA & EPA
Process SafetyManagement
GOOD ENGINEERING PRACTICE
Written InternalGuidelines
Mentor/Engineering Practices
Industry Codes& Standards
Emergency ShutdownSystems, Control, Relief
Systems
SIF included here
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Standards Bodies that Define Good Engineering
Practice for Safety Instrumented Systems
ISA, Instrumentation Systems and
Automation SocietyIEC, International ElectrotechnicalCommission
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Other standards and guidelines must be
integrated with SIS standards!
ISA 84.01-2003
IEC 61508 IEC 61511ASME
NFPAAPI
ISO AICHE
BooksBoiler Codes
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Safety Instrumented System Standards
ISA 84.01-2003 -Functional Safety: Safety
Instrumented Systems for the Process IndustrySectorIdentical to IEC 61511 with inclusion of grandfatherclauseTo be published October 2003
IEC 61508 -Functional Safety: Safety RelatedSystemsCurrent version released 1999Under revision for next release 2005
IEC 61511 -Functional Safety: SafetyInstrumented Systems for the Process IndustrySectorPublished 2003
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Front EndEngineering
EngineeringDesign
Commissioning
Management of Change
SafetyLifecycle
Planning
Operations &Maintenance
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Manage risk - People
Identify role of individual or departmentsWho is assigned to project?
What are their roles?
Document competency of individuals anddepartments
Does anyone need more training?
Who will mentor inexperienced engineers?
Who will review and approve?
This is good project management.
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Manage risk ProceduresDefine when the following will take place:
Verifications,
Audits, and
Validation.Require procedures for evaluating theperformance of the SIS after it has beeninstalled
Performance audits and
Tracking failures rates.
This is good quality control.
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Assess risk and mitigate it
Will talk about the how to later
The assessment results in theassignment of Safety IntegrityLevel
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Safety Integrity Level
SIL PFDavg Risk Reduction
Availability (%)
4 10-4 to 10-5
10,000 to100,000
99.99 to99.999
3 10-3 to 10-4
1,000 to10,000
99.9 to99.99
2 10-2 to 10-3
100 to1,000
99 to 99.9
1 10-1 to 10-2
10 to 100 90 to 99
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Lets talk about Risk.
What is your wager?
How many times doyou place the wagereach year?
What are your odds of
losing your wager?
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Design SIF
Justify selection of devices
Document the safety requirementsspecification
Design SIFs to achieve SafetyIntegrity Level.
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Prove itVerify
Safety Integrity Level
Fault tolerance
CommissioningInstall SIFs per design documents
Functional safety assessmentMake sure all documents are in place andall hazards analysis items are addressed.
ValidationTest SIFs to ensure that they havedesired functionality
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Maintain it Operation, maintenance andtesting
Use diagnostics and testing tomaintain performance
Create and maintain procedure tosupport these activities
Train personnel on procedures
Management of changeMonitor changes to SIS that might affect SIL
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Audit it
Includes design and procedures
Define frequency of auditsDetermine the degree ofindependence of auditing activity
Document auditDefine follow-up activities
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Front EndEngineering
EngineeringDesign
Commissioning
Management of Change
SafetyLifecycle
Planning
Operations &Maintenance
