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8/13/2019 Safety Instrumented Systems Angela Summers (1)
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Safety I nstrumented 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 I nstrumented 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 defined
actions that either prevent the hazard or mitigate thehazard consequences.
Input ---- Logic Solver ---- Output
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Examples of Safety I nstrumented Systems
High fuel gas pressure furnace initiatesshutdown of main fuel gas valves.
High reactor temperature initiates failopen action of coolant valve.
High column pressure initiates fail openaction of pressure vent valve.
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OSHA & EPA
Process Safety Management
GOOD ENGINEERING PRACTICE
Written InternalGuidelines
Mentor/EngineeringPractices
Industry Codes& Standards
Emergency ShutdownSystems, Control, Relief
Systems
SIF included here
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Standards Bodies that Def ine Good Engineer ing
Practice for Safety I nstrumented Systems
ISA, Instrumentation Systems and
Automation SocietyIEC, International ElectrotechnicalCommission
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Other standards and guidel ines must be
integrated with SIS standards!
ISA 84.01-2003
IEC 61508 IEC 61511ASME
NFPAAPI
ISO AICHE
BooksBoiler Codes
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Safety I nstrumented System Standards
ISA 84.01-2003 -Functional Safety: Safety
Instrumented Systems for the Process Industry SectorIdentical to IEC 61511 with inclusion of grandfather clauseTo be published October 2003
IEC 61508 -Functional Safety: Safety Related SystemsCurrent version released 1999Under revision for next release 2005
IEC 61511 -Functional Safety: Safety InstrumentedSystems for the Process Industry SectorPublished 2003
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Front EndEngineering
EngineeringDesign
Commissioning
Managementof Change
Safety Lifecycle
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 riskProcedures
Define when the following will take place:Verifications,
Audits, and
Validation.
Require procedures for evaluating theperformance of the SIS after it has beeninstalled
Performance audits andTracking failures rates.
This is good quality control.
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Assess r isk and mitigate it
Will talk about the how to later
The assessment results in theassignment of Safety Integrity Level
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Safety I ntegrity Level
SIL PFDavg Risk Reduction Availability (%)
4 10-4to 10-5 10,000 to 100,000 99.99 to 99.999
3 10-3to 10-4 1,000 to 10,000 99.9 to 99.99
2 10-2to 10-3 100 to 1,000 99 to 99.9
1 10-1to 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 oflosing your wager?
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Design SI F
Justify selection of devices
Document the safety requirementsspecification
Design SIFs to achieve Safety IntegrityLevel.
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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 and allhazards analysis items are addressed.
ValidationTest SIFs to ensure that they have desiredfunctionality
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Maintain itOperation, maintenance andtesting
Use diagnostics and testing to
maintain performanceCreate 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 of independenceof auditing activity
Document auditDefine follow-up activities
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Front EndEngineering
EngineeringDesign
Commissioning
Managementof Change
Safety Lifecycle
Planning
Operations &Maintenance
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