safety instrumented systems angela summers (1)

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

safety instrumented systems angela summers (1)

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