Performance based gas detection for hydrocarbon storage

Performance Based Gas Detection
for Hydrocarbon Storage

Kenexis

Copyright 2011 - Kenexis

Presenter Introduction
• 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
ISA84 Expert


„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


Prescriptive Standards in FGS Design

• Well-established guidance for
design of FIRE detection and
mitigation systems
• Provide detailed requirements for basis of
safety for most types of fire detection
and alarming function
• Allow for performance based alternatives to be used
(where appropriate)
• Generally not specific to chemical processing
• Very little guidance on gas detection


Performance-Based Standards
• ISA TR 84.07 Provides guidance for gas detection
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

Performance-Based or Prescriptive…
What‟s Better?
• A combination of both prescriptive and
performance-based methods in best
• Many FGS elements are adequately addressed by
prescriptive standards
• Many FGS elements (although addressed by prescriptive
standards) can be better designed using performance-
based methods
• Some FGS elements typical found in chemical processing
facilities are not adequately covered by prescriptive
standards


Fire and Gas Design Lifecycle


Fire and Gas Design Lifecycle

• Consistent with the
underlying principles of ISA
84.00.01 and IEC 61511

• Does not provide a
complete process for FGS
design – only intended for
application to process
areas


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
Operation, Maintenance
and Testing
Verify FGS Availability

Management of Change
Modify Design
(if required)


Identifying Requirements for FGS
• Recommended from Previous for FGS
Safety Studies
• Process Hazards Analysis (PHA)
• Layer of Protection Analysis (LOPA)
FGS Zone Definition
• Quantitative Risk Assessment (QRA) Construction, Installation,
And Commissioning
• Required by Government Determine FGS
Performance Requirements
Regulation
PSAT
• Required by Industry or Verify Detector Coverage
Corporate Standards Operation, Maintenance
and Testing
• Required by Insurance Provider Verify FGS Availability

Modify Design
(if required)

QRA / safety case analysis assumes performance for FGS. Performance
Based FGS analysis can be used to verify assumed performance.


FGS Philosophy Development
Input Task Tools
for FGS Deliverable
for FGS
FGS Zone Definition
And Commissioning
Determine FGS
Risk Tolerance Performance Requirements
FGS Philosophy
Criteria Develop FGS Philosophy Template and FGS Philosophy
PSAT
HSE Philosophy checklist And Procedures
Verify Detector Coverage
and Testing
FGS
FGS Design Basis
Define FGS Zones Toolkit –
Modify Design
(if required)
PHA Pro Report


FGS Philosophy Elements
• Standardized Methods for Categorizing FGS
Hazards and Risk
• Criteria for Hazard Identification
• Criteria for Risk Categorization
• Requirements for Safety Analysis and Risk Studies
• Standardized FGS Design Heuristics
• Criteria for FGS Zone Definition and Grading
• Criteria for Assigning Performance Targets to FGS
Equipment
• Criteria for Selecting Appropriate Sensor Technologies
• Alarming Requirements
• Manual Activation
• Detector Voting for Automatic Action Requirements
• Criteria for Detector Setpoint Selection


Procedures Resulting From Philosophy
Hazard Identification (HAZID) Zone Definition and Grading

Performance Target Selection Performance Target Verification
Residual FGS
Release Detected? FGS Effectiveness Residual Fire Effectiveness Frequency
Early Ignition? ("Detector Coverage") ("PFD") Delayed Ignition? Detected ("PFD") (1/year)

Success 9.10E-06
Yes 0.9
0.85
Failure 1.01E-06
Yes 0.1
0.04
No 1.78E-06
0.15

Success 2.18E-04
0.9

Yes Success 7.43E-07
0.85 0.9
Release Yes
2.97E-04 0.85 Failure 8.25E-08
Yes 0.1
0.04
No 1.46E-07
Failure 0.15
0.1
No 2.33E-05
0.96

No Success 1.31E-06
0.96 0.9
Yes
0.85 Failure 1.46E-07
Yes 0.1
0.04
No 2.57E-07
No 0.15
0.15
No 4.11E-05
0.96
Total 2.97E-04


Definition of Fire and Gas Zones

Input Task Tools Deliverable
Risk Tolerance FGS Philosophy
Criteria Develop FGS Philosophy Template and FGS Philosophy
HSE Philosophy checklist And Procedures

PFD
P&ID FGS
FGS Zone Definition FGS Zone List
Plot/Deck Plan Toolkit
Cause-and-Effect

Determine FGS FGS FGS Design Basis
Performance Requirements Toolkit Report


Why is Zone Definition Important?
• Areas in processing plant have differing fire and gas hazards
• Building Fire Protection – zones where goal is protection of personnel and
assets from general building fire hazards
• Processing Area – zones where goal is incipient detection of fire and/or gas
releases in processing areas
• Process/Non-Process Segregation – zones where goal is segregator of process
hazards from non-process areas

• Requirement for clear communication of hazards to
operations and emergency responders


FGS Zone Categories
• Zones are categorized to facility development of
basis of design
Zone Categories Area Definition Examples

H Hydrocarbon Possessing Area, General Fire / Flammable Gas, Production Separation,
Toxic Gas Hazard Gas Compression,
N Non-Hydrocarbon Fire Hazard Combustible Liquid Storage,
Lubrication Oil System
G General Occupancy, No Hydrocarbon Fire Hazard Accommodations Area,
Control Building
E Non-Hydrocarbon Special Equipment Protection
Non-classified Electrical Equipment
T Gas Turbine or Engine Enclosures
Gas Turbine and Turbine Enclosures
V Combustion Air Intake / Ventilation Air Intakes Combustion Air blower, HVAC Fresh Air
Intake


FGS Zone List
• Complete list of FGS Zones, including:
• Identifier (tag, name)
• Description
• Category


Fire and Gas Performance Targets

PFD
P&ID FGS
FGS Zone Definition FGS Zone List
Plot/Deck Plan Toolkit
Cause-and-Effect

FGS Philosophy Determine FGS FGS FGS Design Basis
& Procedure Performance Requirements Toolkit Report

Verify Detector Coverage Effigy™ FGS Detector
Mapping Report


Risk Modeling Requirements
• Desire a Risk Model that is sensitive to:
– Detector Coverage
– FGS System Probability of Failure on Demand
• Analysis Considerations include:
– Hydrocarbon Processing Equipment
– Fire and Gas Consequences
– Release Likelihood
– Level of Human Occupancy of Zone
– Ignition Probabilities
– Production Value for Process


Performance Target Determination

• Two Common
Approaches
– Semi-Quantitative
(Similar to LOPA)

– Quantitative Risk
Analysis (QRA)


FGS Performance Targets
• Performance Targets Specify requirements for
Risk Reduction:
• Fire and Gas Detector Coverage
• Geographic Coverage
• Scenario Coverage
• Equipment Probability of Failure
• Safety Availability
• Safety Integrity Level (SIL)


Fully Quantitative Approach
• Targets calculated through rigorous modeling
of hazards
• 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
• Analysis based on Scenario Coverage and safety
availability


Hazard Scenario Identification
• 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
• Release Scenarios with extremely low likelihood and/or
consequence need not be considered
• 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, …..

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

Fully-Quantitative Method Copyright 2011 - Kenexis

Individual Scenario Overlay

Large
Hole Size

Medium
Hole Size

Small
Hole Size


Risk Integration
• Join Consequence and Likelihood to generate a list of
possible scenario outcomes
– Each outcome has an associated level of risk (PLL, Financial
Loss)
– Event Trees are used to determine risk for each outcome
• Event outcomes are integrated to determine risk for a
FGS zone or Platform
– Risk for FGS zone/platform is compared against Customer
tolerable risk criteria
• Initially select low detector coverage and progressively
increase until tolerable risk achieved.


Unmitigated Geographic Risk


Risk Integration – Event Tree Residual FGS
Release Detected? FGS Effectiveness Residual Fire Effectiveness Frequency
Early Ignition? ("Detector Coverage") ("PFD") Delayed Ignition? Detected ("PFD") (1/year)

Success 9.10E-06
Yes 0.9
0.85
Failure 1.01E-06
Yes 0.1
0.04
No 1.78E-06
0.15

Success 2.18E-04
0.9

Yes Success 7.43E-07
0.85 0.9
Release Yes
2.97E-04 0.85 Failure 8.25E-08
Yes 0.1
0.04

Estimated Risk is Failure
No
0.15
1.46E-07

0.1
greater than No
0.96
2.33E-05

performance No
0.96
Success
0.9
1.31E-06

target, adjust Yes
0.85 Failure 1.46E-07
Yes 0.1

parameters to 0.04
No 2.57E-07
No 0.15
achieve targets 0.15
No 4.11E-05
0.96
Total 2.97E-04


Mitigated Geographic Risk

22.4% Coverage


Revised Mitigated Risk

15.4% Coverage


Semi-Quantitative Approach
• Team-Based approach employing calibrated
risk assessment tables
• Risk factors qualitatively ranked by team
• Likelihood
• Consequence
• Mitigating factors
• Selected categories determine the “zone grade”
• Zone grade defines geographic coverage and safety
availability

Grade Level of Risk Detection Coverage FGS Safety Availability
A High Risk 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)


Calibration
• Parameters and
performance target
calibrated by full
QRA of typical
zones
• Safety Availability
and Geographic
Coverage Set


Extents of Graded Areas
• 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 C Grade B Grade A


Verifying FGS Detector Coverage

FGS Philosophy Determine FGS FGS FGS Design
& Procedure Performance Requirements Toolkit Basis Report

FGS Philosophy FGS Detector
Verify Detector Coverage Effigy™
& Procedure Mapping Report

FGS FGS Availability
Toolkit Report


Why Verify Detector Coverage?
• Failure of Gas Detection Systems to Function are
related to one of two Mechanisms:
• 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:
• The coverage footprint is sufficient to provide the
required hazard alarms and control actions
• Detectors are appropriately located considering leak
sources, wind directions, and other site specific factors
The Maginot Line
HSE Statistics Indicate that 40% of Major Gas Release in North Sea Offshore
Installations are Not Detected by Gas Detection Systems


Verifying Detector Coverage for Process Areas
• Two methods of coverage verification are defined by ISA TR
84.07:
• “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.”


Gas Detector Mapping Assessment
• Detector Performance characterized
based on data from FM approval testing

• Detector Coverage calculated based on 3-
dimensional modeling

• Achieved coverage is compared against
performance target

• Geographic Coverage considers leak
sources and “Design Basis Cloud Size"


Calculating Gas Geographic Coverage

Design Basis
Cloud

Leak Point
(Covered)

Leak Point
(Not Covered)


Gas Geographic Coverage

15.4% Coverage


Verifying FGS Availability

FGS Detector FGS Detector
Verify FGS Availability Effigy™
Locations Mapping Report

FGS FGS Availability
FGS List Verify FGS Availability
Toolkit Report

FGS FGS Performance
Modify Design (if required)
Toolkit Specifications


Conceptual Design

• Purpose
– Select equipment appropriate for
performance target
– Specify how the system operates
– specific and general
– Basis for detailed design
• Result
– FGS Requirements Specification


Parameters Impacting Availability


Verifying FGS Availability


FGS Requirements Specification

• Defines FGS behavior
– Functional specifications
– Integrity specifications

• Numerous documents, mainly FGS logic
solver functional specification
– Logic Description (Cause-and-Effect or Logic
Diagram)
– General Notes


Detailed Design and Specs

Specification
Design Specification Detailed Design
Templates

Procedure
Procedure Development Templates – Procedure
Word, DB

• Loop Sheets
• Internal Wiring Diagrams
• Cable Schedules
• PLC Programs


Specification
Detailed Design Specs Detailed Design
Templates

Procedure
Procedure Development Templates – Procedure
Word, DB

• Develop procedures for
– Operation of FGS (startup, reset, bypass)
– Response to detected failures of FGS
– Maintenance and testing of FGS


Construction, Installation and
Commissioning

And Commissioning

PSAT

• Purchase equipment
• Install on site – location and orientation
• Load software
• Connect wiring

Pre Start-Up Acceptance Testing


And Commissioning

Checklist
Validation Plan PSAT Punchlists
Template

• Verify that installed equipment and software conform to
safety requirements specifications
• Review software and hardware
• Review all relevant equipment
• Generate deviation record (punchlist)

Operation and Maintenance


And Testing


• Periodic function testing
• Respond to overt faults
• NOTHING!!!!




And Testing


• Follow management of change procedures


Kenexis


Performance based gas detection for hydrocarbon storage

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