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THE 10TH TANK & REFINERY CONFERENCE, COPENHAGEN, DEC 2017
FUNCTIONAL SAFETY / “SIL” IN PROCESS INDUSTRIES
BARIS ARSLAN MANAGING DIRECTOR ORS CONSULTING WWW.ORSCONSULTING.NO
www.orsconsulting.no
ORS CONSULTING
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• Control and mitigation of fires & explosions in the process industries – main concern!
• As a part of traditional process design, two different protection layers are installed to avoid accidents
• Typically, it is achieved by – An electrical system (instrumented), such as
Emergency shutdown system (ESD) – A mechanical system – such as Pressure Safety
Valve (PSV) or similar
• These systems are called primary and secondary
• Primary and secondary systems are independent of each other!
PROCESS SAFETY IN PETROLEUM- OCH PETROCHEMICAL INDUSTRIES
Process Safety
Instrumented
systems (ESD)
Mechanical
Systems (PSV)
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WHAT DO WE KNOW ABOUT FUNCTIONAL SAFETY?
Sensor Logic Final
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SAFETY INTEGRITY LEVEL (SIL) CONCEPT
Maximum one (1) system failure in 500 Times?
SIL 4 10-5 < PFD < 10-4
Fails 1 in 10 000 demands
SIL 3 10-4 < PFD < 10-3
Fails 1 in 1000 demands
SIL 2 10-3 < PFD < 10-2 Fails 1 in 100 demands
SIL 1 10-2 < PFD < 10-1 Fails 1 in 10 demands
Higher reliability
SIL Requirement: Functions+Integrity+Condition
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ORS CONSULTING
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CONTAINMENT OF FLAMMABLE/EXPLOSIVE INVENTORIES IN PROCESS
IEC 61511
Safety Instrumented Systems for the Process Industry
IEC 61508 Functional Safety of Electrical/Electronic
and programmable electronic safety related systems
ISO 13702 Control and mitigation of fires
and explosions
ISO 10418 Basic Surface Process Safety
Systems
API 14 C
(Process Safety)
API 521
(Depressurization, Pressure-relief)
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PROTECTION LAYERS VS RELIABILITY
PROTECTION LAYERS PROBABILITY OF FAILURE
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FUNCTIONAL SAFETY FROM A LIFECYCLE PERSPECTIVE
• IEC61511 provides a complete framework for management of functional safety from a lifecycle perspectives.
• Different roles as: – Supplier / Vendor – Design Realization (Engineering) – System Integrator (typically the Operator)
• INVOLVEMENT OF ASSET OPERATIONS IN SIS DESIGN PHASE IS CRITICAL FOR SUCCESS
Plan
ning
/ Ve
rific
atio
n / V
alid
atio
n / C
ompe
tenc
e Hazard and Risk Assessment
Allocation of Safety Functions to Protection Layers
Design and Engineering of SIS
Installation, Commissioning and Validation
Operation and Maintenance
Modification
Decommissioning
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• Functional requirements • Failure rates (collection and
categorization of failure rates) • Type and number of Demands • Spurious failures • Independent protection layers • Overall PFD/reliability monitoring • Other issues (systematic failures,
Common cause) • Lifetime monitoring
SIS OPERATIONS PERFORMANCE MONITORING
Test procedure SRS
SIS lifecycle
plan
Integrity check
Integrity
Condition
Function
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ORS CONSULTING
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SIS PERFORMANCE MONITORING
0,00E+00
1,00E - 01
2,00E - 01
3,00E - 01
4,00E - 01
5,00E - 01
6,00E - 01
7,00E - 01
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Failu
re R
ate
Year
Average Failure Rate per Year/1 Mil hours
Average OREDA Trend Line
Integrity
condition
Function
Testing
Reliability Inspection
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FAILURE REPORTING – KEEP IT SIMPLE
In and ideal world; All failures for all components should be reported Pragmatic (mimimum) approach; Dangerous undetected failures must be reported (even if they can be easily fixed!)
Failure
Damage type and damage code
Safe failureDangerous
failure
Safe detected
Safe undetected
Dangerous detected
Dangerous undetected
To be recorded in ERP system
Dangerous undetected
Used in Reliability Analysis
Classification of failures for
Reliability Analsis
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SIS RELIABILITY IN OPERATIONAL PHASE
Start Time 1τ 2τ 3τ 4τ 5τ 6τ 7τ TimeTOTAL
(MTTF) Σ Up-time
Σ Down-time (MDT)
Dangerous Undetected Failures (DUF) Function Test Interval (τ)
Repair Time To Repair (MTTR)
Test Independent Failures (TIF)
Time Dependent CSU
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FUNCTIONAL SAFETY – WEAKEST LINK
Subsystem PFD
TIF CSU Common Cause Random
Pressure Transmitter 8,86E-6 1,09E-6 2E-6 1,19E-5
Hardwired Logic Solver - 2,22E-4 1E-7 2,22E-4
HIPPS Valve incl. actuator - 2,67E-3 2E-6 2,67E-3
Solenoid Valve - 2,42E-3 2E-6 2,43E-3
Total 8,86E-6 5,32E-3 6,1E-06 5,33E-3
SIL 2?
Final Element
Sensor Element
Logic Element
CSU
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FAILURE CATEGORIES
Prob
abili
tty o
f Det
ectio
n
Det
ecte
d U
ndet
ecte
d
Consequence of Failure Safe Dangerous
Our Concern!
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CONCEPT OF USEFUL LIFETIME
• Useful Life-time: Constant failure rate.
Not fully true! It is only an assumption - up to 8-10 years.
• Useful Life-time, Extended: Progressive failure rate!
Assumption of constant failure rate invalid
Not allowed to use constant failure rate.