201205 presentation
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A Case Study: Updating a Refinery Boiler
Controls utilizing ISA 84 Standard for
Safety Instrumented Systems
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Presenters
Alan Sharkey Audubon
Chuck Laughter Audubon
Matt Hufford Wilson Mohr
Steve Papp - Wilson Mohr
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Agenda
Functional Safety Life Cycle Overview
Case Study of Boiler in Refinery
HAZOP
LOPA PFD/SIL Determination
SRS Development
SIS Implementation Phase
Operation & Maintenance Phase
Q&A
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Process Safety Management
ISA 84
IEC 61508/11
NFPA
API
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Safety Life Cycle Flow-Chart
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Hazard ID and Risk Assessment
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HAZID/HAZOP Objectives
Identify Hazards and Hazardous events of the process and
associated equipment
Task Required For each hazard identified , determine the consequence /severity
level, the deviation, the initiating cause(s), and the safeguards(s)
Note: Safe design should be developed as far as reasonably
practical before reliance is placed on the SIS to reduce risk
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LOPA
Objectives Identify required mechanical, operational & safety instrumented
functions (SIF) protection layers for each consequence carried intoLOPA
For each SIF determine the associated SIL & and risk reduction
target
Tasks required
Review hazard identification, for each hazard assign risk reductioncredits
Assign target PFD (SIL x) to each SIF
Note: Client will most likely have own risk graph and acceptablelevels of risk
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SRSDefinition of SRS: Function design requirements of the SIS
Minimum Requirements
SIS System architecture (sensor, logic solver & end control elements
System hardware standards
Spare capacity, loading & expansion
Specify testing interval(s)
I/O requirements
I/O signal types and field interfaces
System communications
Equipment and field termination/marshalling cabinet design
requirements Operator MOS Override requirements (HSW/KSW/Status Panel)
Optional Items
Preliminary SIL verification calculations
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Det ai l Designing of SIS Objectives To design, procure and test the SIS equipment to meet the SRS
Detailed specification of hardware; data sheets, etc
Provide SIS detailed design drawings; loop diagrams, etc.
Application software functional logic design and development. Construct SIS following approved procedures designed to reduce
systematic faults.
Verify compliance to SRS; confirm testing intervals are satisfied.
Provide procedures to operate and maintain the SIS. To validate, through inspection and testing, that the designed,
built & configured SIS logic solver, application software (SIFs) &
associated hardware meets in all respects the requirements as
stated in the SRS (FAT).
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Ins ta l la t ion & Comm iss ion ing Objectives Install and commission the SIS according to design
documentation so that it is ready for final system validation.
Commission and check calibration of the SIS components
To integrate and test the SIS (SAT)
To validate, through inspection and testing, that theinstalled & commissioned SIS & its associated SIFs meets
in all respects the requirements as stated in the SRS.
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Operat ion & Main tenanc e Objectives To ensure that the functional safety of the SIS is maintained
during operation and maintenance
SIS documentation is maintained
To control maintenance and testing activities, so that the
design intent of SIS is retained over the asset life
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Management o f Change Objectives To control all SIS modifications, so that safety integrity of
the SIS is maintained over the asset life.
To ensure that any SIS changes are properly planned,designed reviewed, approved and tested prior to
implementation.
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Case Study of Refinery SRU
HAZOP
LOPA
SRS
SIS
Operations & Maintenance
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SIS Implementation
-Customer Timing
-Plant Control
Infrastructure
-CorporateSpecifications
-S84 vs NFPA 85
-CustomerAwareness
-MaintenanceRestrictions
Practical Considerations
-Concurrent
Development Cycle
-Vendor
Restrictions
-Conflicting
Requirements
-Needs dont match
capabilities
Impact on Cycle
QualificationsResulting
Complications
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SIS Implementation
- Customer Timing:
- 2 Year Turnaround Schedule
- Confecting Requirements
- Corporate Spec for S84
- Plant Spec for NFPA 85
- Concurrent design cycle required
- Forced SIL Target
- Commitment to Amend Mechanical design
- Preselected Control Vendor
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SIS Implementation
- RedundantProcessors UtilizingIndependent Tasks
- Shared Power &Comm Backbone
- DedicatedRedundant Analog &Digital Inputs on SISI/O
- SIS & BMS OperateTotally independently
- SIS Processes SIF
and Controls SafetyRelay Only
- MFT Circuit is theInterlockingMechanism Betweenthe Two Systems
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SIS Implementation
DCS Controlled
Combustion Circuit
with BMS Dump
Vale on IP
Backup Nitrogen
System on IA
Single Block with
Vent on Headers
Low Fire Light off on
Individual Burner Trains
2of3 Voting on all
NFPA Recommended
SignalsDouble Block and
Bleed on all
Individual Trains
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SIS Implementation
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SIS Implementation
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Quest ions?
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