Fire and Gas Detection and Suppression Systems (FGS) have long been successfully employed as a safeguard in the process industries. Unfortunately, design methods for determining the quantity and placement of detectors have historically been less than satisfactory. Design practices based on rules of thumb and experiences have often resulted in design inconsistencies, and achievement of tolerable risk cannot be ascertained. Rule-based methods often place detectors where they are not needed and leave high risk areas unnecessarily exposed. ISA released technical report TR 84.00.07 to address this problem. This technical report explains the metrics, such as detector coverage, and techniques that can be applied to the design of FGS which results in optimal designs that are safer and more repeatable. This paper will provide an overview of the contents of the technical report, and also provide some case study examples that show how these performance-based methods result in superior designs to currently used techniques such as grid-based approaches.

1. Optimizing Fire and Gas
System Design Using the
ISA Technical Report
ISA TR 84.00.07
EDWARD MARSZAL
Standards
President and CEO
SRINIVASAN GANESAN
MENA Region Manager
Certification
Education & Training
Publishing
Conferences & Exhibits
ISA Automation Conference 2013- EMEA
(Dammam, Saudi Arabia) – December 10-12, 2013

2. Presenter Introduction
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ISA84 Expert
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Edward M. Marszal, PE, ISA84 Expert
President, Kenexis
20 Years Experience
ISA Author “SIL Selection”
ISA Committees - S84, S91, S18,
S84 WG7 Fire and Gas
ISA Safety Division Past Director
ISA Fellow
AIChE, NFPA Member
BSChE, Ohio State University

3. Title
 Introduction
 Main Topics
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‘Basis of Safety’
Prescriptive v. Performance Basis
FGS Design Lifecycle
Performance Target Selection
Detector Coverage Verification
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

4. ‘Basis of Safety’ for FGS
• All critical instrumentation / control systems require
a ‘basis of safety’
• specify adequate equipment selection and design
• specify functional testing requirements
• For fire and gas systems ‘basis of safety’ are
developed in two ways:
• Prescriptive ‘Basis of Safety’,
NFPA/EN standards, etc.
• Performance Basis / Risk Assessment
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

5. Prescriptive Standards in FGS Design
• Well‐established guidance for
design of detection and
mitigation systems
• Provide detailed requirements for basis of
safety for most types of FGS function
• Do not provide detailed requirements for fire and gas
detection in chemical processing areas
• Allow for performance based alternatives to be used
(where appropriate)
• Generally not specific to chemical processing
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

6. Performance-Based Standards
• ISA TR 84.07 Provides guidance for FGS design in
accordance with the principles of ISA84 / IEC61511
• Specify and Verify Performance Targets
• Availability
(equivalent to SIL)
• Detector Coverage
• Written specifically for
process industry
• Not intended as
replacement for
prescriptive design;
intended as supplement
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

7. Fire and Gas Design Lifecycle
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

8. Typical Workflow for FGS Design
Identify Requirement
for FGS
Design Specification
Develop FGS Philosophy
Procedure Development
FGS Zone Definition
Construction, Installation,
And Commissioning
Determine FGS
Performance Requirements
PSAT
Verify Detector Coverage
Verify FGS Availability
Modify Design
(if required)
Operation, Maintenance
and Testing
Management of Change
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

9. Fire and Gas Performance Targets
Input
PFD
P&ID
Plot/Deck Plan
Cause-and-Effect
FGS Philosophy
& Procedure
Task
Tools
Deliverable
FGS Zone Definition
FGS
Toolkit
FGS Zone List
Determine FGS
Performance Requirements
FGS
Toolkit
FGS Design Basis
Report
Effigy™
FGS Detector
Mapping Report
Verify Detector Coverage
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

10. Risk Modeling Requirements
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Desire a Risk Model that is sensitive to:
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Detector Coverage
FGS System Probability of Failure on Demand
Analysis Considerations include:
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Hydrocarbon Processing Equipment
Fire and Gas Consequences
Release Likelihood
Level of Human Occupancy of Zone
Ignition Probabilities
Production Value for Process
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

11. Performance Target Determination
• Two Common
Approaches
– Semi‐Quantitative
(Similar to LOPA)
– Quantitative Risk
Analysis (QRA)
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

12. Fully Quantitative Approach
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Targets calculated through rigorous modeling
of hazards
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Consequence characterized by
dispersion/consequence modeling
Release likelihood characterized by equipment
failure database
Mitigating factors characterized by site specific
factors
Calculated risk compared against tolerability
criteria
Design criteria are iteratively modified in order
to achieve the tolerable risk target
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Analysis based on Scenario Coverage and safety
availability
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

13. Hazard Scenario Identification
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Hazard scenarios should include general release / fire
scenarios
– Identify all credible release scenarios, including:
– Vessels, process piping, flanges, instruments,
wellheads, pumps, compressors, heat
exchangers, launchers/receivers, risers and
pipelines
Identify specific factors effecting release scenario
– Hole size, location, orientation, phase, toxicity (H2S),
occupancy
Result should be a detailed list of release scenarios with
enough detail to undertake consequence and likelihood
analysis
Identify potential incident outcomes:
– Jet fire, Flash Fire, …..
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

14. Likelihood Analysis
• Based on Historical Offshore Data:
– Offshore Release Statistics, 2001. UK Health
& Safety Exec.
– PARLOC 2001: The update of Loss of
Containment Data for Offshore Pipelines. UK
Health & Safety Exec.
• Sensitive to hole size distribution
• Sensitive to Equipment Type
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013
Fully-Quantitative Method

15. Risk Integration – Event Tree
Early Ignition?
Release Detected?
("Detector Coverage")
FGS Effectiveness
("PFD")
Delayed Ignition?
Residual Fire
Detected
Residual FGS
Effectiveness
("PFD")
Yes
0.04
Success
0.9
9.10E-06
Failure
0.1
Yes
0.85
1.01E-06
No
0.15
1.78E-06
Success
0.9
2.18E-04
Yes
0.85
Success
0.9
Release
Yes
0.85
2.97E-04
Yes
0.04
Estimated Risk is
greater than
performance
target, adjust
parameters to
achieve targets
Frequency
(1/year)
7.43E-07
Failure
0.1
8.25E-08
No
0.15
Failure
0.1
1.46E-07
No
0.96
2.33E-05
No
0.96
Success
0.9
Yes
0.85
Yes
0.04
1.31E-06
Failure
0.1
1.46E-07
No
0.15
No
0.15
2.57E-07
No
0.96
4.11E-05
Total
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013
Fully-Quantitative Method
2.97E-04

16. Semi-Quantitative Approach
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Team‐Based approach employing calibrated
risk assessment tables
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Risk factors qualitatively ranked by team
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Likelihood
Consequence
Mitigating factors
Selected categories determine the “zone grade”
Zone grade defines geographic coverage and safety
availability
Grade
Level of Risk
Detection Coverage
A
High Risk
FGS Safety Availability
0.90
0.95 (High SIL 1 Equivalent)
B
Medium Risk
0.80
0.90 (SIL 1 Equivalent)
C
Low Risk
0.60
0.90 (SIL 1 Equivalent)
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

17. Calibration
• Parameters and
performance target
calibrated by full
QRA of typical
zones
• Safety Availability
and Geographic
Coverage Set
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

18. Extents of Graded Areas
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Grade C
Define extents of area the overall zone that are
required to be covered by fire and gas detection
Limits analysis to location where risk is high
Function of process equipment with potential to leak
and process conditions
Similar to electrical area classification
Grade B
Grade A
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

19. Verifying FGS Detector Coverage
Input
Task
Tools
Deliverable
FGS Philosophy
& Procedure
Determine FGS
Performance Requirements
FGS
Toolkit
FGS Design
Basis Report
FGS Philosophy
& Procedure
Verify Detector Coverage
Effigy™
FGS Detector
Mapping Report
FGS
Toolkit
FGS Availability
Report
Verify FGS Availability
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

20. Why Verify Detector Coverage?
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Failure of Fire and Gas System to Function
are related to one of two Mechanisms:
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Inadequate Coverage - Failure to detect hazard
due to inadequate sensor type, number and/or
location
Inadequate Availability - Failure of component
hardware to function as intended
Proposed detector layout should be
assessed to ensure adequate coverage:
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The coverage footprint is sufficient to provide the
required hazard alarms and control actions
Detector views are not impeded by pipework, cable
trays and other obstruction
The Maginot Line
HSE Statistics Indicate that 36% of Major Gas Release in North Sea Offshore
Installations are Not Detected by Gas Detection Systems
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

21. Verifying Detector Coverage for Process Areas
• Two methods of coverage verification are defined by ISA TR
84.07:
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“Detector Geographic Coverage – The fraction of the geometric area
(at a given elevation of analysis) of a defined monitored process area
that, if a release were to occur in a given geographic location, would
be detected by the release detection equipment considering the
defined voting arrangement.”
“Detector (Scenario) Coverage – The fraction of the release scenarios
that would occur as a result of the loss of containment from items of
equipment of a defined and monitored process area that can be
detected by release detection equipment considering the frequency
and magnitude of the release scenarios and the defined voting
arrangement.”
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

22. FGS Detector Mapping Assessment
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Detector Performance characterized
based on data from FM approval
testing
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Detector Coverage calculated based
on 3-dimensional modeling
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50 %
Sensitivity
75 %
Sensitivity
Achieved coverage is compared
against performance target
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013
100 %
Sensitivity

23. FGS Detector Mapping Assessment
Geographic Fire Detector Coverage
Geographic Gas Detector Coverage
Scenario-Based Geographic Risk
Scenario-Based Coverage
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

24. Verifying FGS Availability
Input
Task
Tools
Deliverable
FGS Detector
Locations
Verify FGS Availability
Effigy™
FGS Detector
Mapping Report
FGS List
Verify FGS Availability
FGS
Toolkit
FGS Availability
Report
Modify Design (if required)
FGS
Toolkit
FGS Performance
Specifications
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

25. Parameters Impacting Availability

26. Implementation Phase
Design Specification
Procedure Development
Construction, Installation,
And Commissioning
PSAT
Operation, Maintenance
and Testing
Management of Change
• Prepare detailed design
documents based on FGS
SRS
• Verify and validate prior to
startup
• Perform ongoing maintenance
and testing as required
• MOC is important! Many plant
changes impact coverage
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013

27. Questions?
ISA Automation Conference 2013- EMEA (Dammam, Saudi Arabia) – December 10-12, 2013