Fire & Gas System Philosophy.docx

January/2019

DOCUMENT NUMBER :

West-African Exploration and Production

Classification Status: Unrestricted

Fire & Gas System Philosophy Proprietary Information: This document contains proprietary information and may not be partly or wholly reproduced without prior written permission from Shell Petroleum Development Company The Process Manager for this procedure is the Project Manager, the Process Owner is the Installation Manager Revision

Date

Description

Originator

R01

18-Jan-2019

Issued for Internal Review

I.Oghene

Checker

Approver

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KALAEKULE OFFSHORE PLATFORM Fire & Gas System Philosophy Doc No.

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CHANGE RECORD PAGE REV. N°

Status

Description of Revision

R01

INT

Issued for Internal Review

A01

IFR

Issued for Review

C01

AFC

Approved for Construction

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CONTENTS 1.0 1.1 1.2 1.2.1 1.2.2 1.3 2.0 2.1 2.1.1 2.1.2 2.1.3 2.1.4 2.2 2.3 3.0 3.1 3.2 3.2.1 3.3 3.3.1 3.3.2 3.4 3.5 3.6 3.7 4.0 4.1 4.2 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.4 5.0 5.1 5.2 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.4 5.4.1 5.4.2 5.4.3

PROJECT DESCRIPTION ................................................................................................................ 6 Objective 6 Definition and Abbreviation ................................................................................................................ 6 Definition 6 Abbreviation 7 Site Environmental Conditions .......................................................................................................... 8 APPLICABLE CODES & STANDARDS .......................................................................................... 10 List of Applicable Codes & Standards ............................................................................................. 10 Master Practices–WAEP Local Engineering Practices ................................................................... 10 International Standards.................................................................................................................... 11 WAEP Loss prevention procedures documents .............................................................................. 11 Project Documents .......................................................................................................................... 11 Order of Precedence ....................................................................................................................... 12 Health, Safety And Environmental Requirements ........................................................................... 12 F&G SYSTEM PHILOSOPHY ......................................................................................................... 12 FGS Scope 12 FGS Purpose 13 General 13 Hazards 13 Controlling Flammable Gas Hazards ............................................................................................... 13 Controlling Fire Hazards .................................................................................................................. 13 Fire Zones 13 Voting 14 Executive Actions ............................................................................................................................ 14 Design Efficiency ............................................................................................................................. 15 FLAMMABLE GAS DETECTION .................................................................................................... 15 Detection Requirement .................................................................................................................... 15 Detection Technology Selection ...................................................................................................... 15 Selection Hierarchy.......................................................................................................................... 15 Boundaries/Areas Monitoring .......................................................................................................... 15 Significant Potential Leak Sources .................................................................................................. 15 Congested Plant Modules................................................................................................................ 15 Ducting and Air Intakes.................................................................................................................... 15 Difficult Access or Conditions .......................................................................................................... 16 Building Interior 16 Oil Mist Area 16 Flammable Gas Connection Alarm Limits ....................................................................................... 16 FIRE DETECTIION .......................................................................................................................... 17 Detection Requirements .................................................................................................................. 17 Detector Technology Selection ........................................................................................................ 17 Selection Hierarchy.......................................................................................................................... 17 Wide Area Coverage ....................................................................................................................... 17 Single Point Coverage ..................................................................................................................... 17 Congested Platform/Plant Modules ................................................................................................. 17 Inside Enclosures ............................................................................................................................ 17 Other Selection Scenarios ............................................................................................................... 18 Building Interiors .............................................................................................................................. 18 Critical / High Value Equipment ....................................................................................................... 18 Wellheads 18 This document is controlled electronically and is uncontrolled when printed

KALAEKULE OFFSHORE PLATFORM Fire & Gas System Philosophy Doc No.

5.4.4 5.4.5 5.4.6 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.8.1 6.8.2 6.8.3 6.8.4 6.9 6.9.1 6.9.2 6.9.3 6.9.4 6.9.5 6.9.6 6.10 6.11 6.12 6.13 6.14 7.0 7.1 7.2 7.3 7.4 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.7.1 8.7.2 8.7.3 8.7.4 8.8 8.9 8.10 8.11 8.12 8.12.1 8.12.2

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Gas Generator Enclosures .............................................................................................................. 19 Low Hydrocarbon Fires.................................................................................................................... 19 Manned Areas 19 SYSTEM DESIGN ........................................................................................................................... 19 General 19 Main Fire And Gas Detection System (FGS)................................................................................... 20 FGS input 20 Voting Modules 20 FGS output 20 FGS Power Supply .......................................................................................................................... 21 FGS and SIS Physical Location ...................................................................................................... 21 Civil Facilities 21 FGS Separation & Architecture: ...................................................................................................... 21 F&G Alarm Panel Interface: ............................................................................................................. 21 Detectors: 21 Annunciators: 21 Complex Equipment Package FGS Systems .................................................................................. 22 Package FGS Integration ................................................................................................................ 22 Package Independence ................................................................................................................... 22 Field Cabling and Terminations ....................................................................................................... 22 Vendor Testing and Package Integration ........................................................................................ 22 Hardware 22 Standard Compliance ...................................................................................................................... 22 Simple Equipment Packages ........................................................................................................... 23 Sequence Of Event Recording ........................................................................................................ 23 Maintenance Overrides.................................................................................................................... 23 Scalability 23 Certification 23 HUMAN MACHINE INTERFACE .................................................................................................... 23 PAS Displays 24 Geographic Mimic Panels ................................................................................................................ 24 Alarm Annunciators ......................................................................................................................... 24 FGS Response Time ....................................................................................................................... 24 DETECTION AND FIELD MOUNTED EQUIPMENT ...................................................................... 24 General 24 Detector and Annunciator Layout .................................................................................................... 25 Field Device Hazardous Area Protection Rating ............................................................................. 25 Ingress Protection ............................................................................................................................ 25 Gas Detection Elements .................................................................................................................. 25 Calibration Gas 26 Line-Of-Sight Gas Detectors ........................................................................................................... 26 Boundary Monitoring........................................................................................................................ 26 Area Monitoring ............................................................................................................................... 26 Installation 26 Sensor Robustness ......................................................................................................................... 26 Point Gas Detectors ......................................................................................................................... 26 Air Intake / Outlet Gas Detectors ..................................................................................................... 27 Accoustic Leak Detection ................................................................................................................ 27 Gas Detector Location And Mounting .............................................................................................. 27 Flame Detection ............................................................................................................................... 27 Technologies 27 Installation 28

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8.13 8.13.1 8.13.2 8.13.3 8.14 8.14.1 8.14.2 8.14.3 8.15 8.16 8.16.1 8.16.2 8.16.3 8.16.4 8.17 9.0 9.1 9.2 9.3 9.4 10.0 11.0 12.0 13.0

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Smoke Detection ............................................................................................................................. 28 Technologies 28 Installation 28 High Sensitivity Smoke Detection: ................................................................................................... 28 Heat Detection 28 Voting 29 Point Heat Detection ........................................................................................................................ 29 Linear Heat Detection ...................................................................................................................... 29 Manual Call Point ............................................................................................................................. 29 Audible Alarm Sounders .................................................................................................................. 30 Site Siren 30 Individual Alarm Sounder................................................................................................................. 30 Civil Facilities 30 Visual Alarm Device ......................................................................................................................... 30 Lightning Protection ......................................................................................................................... 31 QUALITY ASSURANCE AND CONTROL....................................................................................... 31 Cause And Effects Review .............................................................................................................. 31 FGS Risk Assessment (SIL classification) ...................................................................................... 31 SIL Verification (FMEDA / PFD Calculation) ................................................................................... 31 Reviews and Audit by the WAEP .................................................................................................... 32 APPENDIX 1- FLAMMABLE GAS SENSING TECHNOLOGIES .................................................... 33 APPENDIX 2 – COMBUSTION (FIRE & SMOKE) SENSING TECHNOLOGIES ........................... 34 APPENDIX 3 - TONAL CHARACTERISTICS OF ALARM SOUNDERS ........................................ 36 APPENDIX 4 – FIRE ZONE SCHEDULE........................................................................................ 37

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1.0

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PROJECT DESCRIPTION OML’s 71 and 72 are located at approximately 27km and 50 km respectively south of the Bonny River inside the shallow Offshore Waters – Water depths are 65ft (OML71) and 131ft (OML72). To date while oil production is from OML 72 only in the KALAEKULE field which was discovered in 1984 and production from the field started in July 1986. OML 71 is largely undeveloped. KCPPA: A single train 3 stage (XHP, HP, LP) three phase Gas Separation (250 MMSCFD) and Oil (25 MBBLs/Day). The KCDP-A and KCPP-A are located 30m apart and linked by a walk way bridge while KCDPB and KCJV-A are located about 970m and 600m respectively from KCPP -A. In an effort to monetize oil and gas in OML 72 based on the available resources, the COMPANY has planned to re-furbish the existing facilities on KCPP-A and KCDP-A by installing new process modules/packages.

1.1

Objective This document provides the philosophy that defines the basic principles for the design of the Fire and Gas detection and protection system and field devices for the KALAEKULE Platform refurbishment Project Facilities. This document forms part of the overall safety philosophy with respect to project hazard identification, risk assessment and mitigation and hence it is imperative that it is read in conjunction with the project applicable documents. listed in Section 2.1.4 The primary design objective shall be to provide instrumentation, control and automation systems that are:            

Safe Fit for purpose Cost effective Reliable and offer a high availability Simple to operate and maintain Capable of integrating and inter-operating with the rest of SPDC’s control and communications infrastructure seamlessly Flexible and capable of accommodating future modifications, updates, upgrades and expansions Based on the latest mature technology Suitable for and supported through the project design lifespan Maintainable by specialist personnel resident within easy reach Centralized and offer enterprise-wide monitoring and control of all facilities within the Project from a central location. Standardized to afford spare parts commonality / Interchangeability, and reduction in training effort and maintenance costs.

1.2

Definition and Abbreviation

1.2.1

Definition COMPANY

NNPC/WAEP JV

Contractor

The party that carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project or operation of a facility. The Principal may undertake all or part of the duties of the Contractor. This document is controlled electronically and is uncontrolled when printed

KALAEKULE OFFSHORE PLATFORM Fire & Gas System Philosophy Doc No.

Vendor

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Party(s) responsible for manufacturing and/or supplying materials, equipment, technical documents/drawings and services to perform the duties specified by COMPANY.

Principal

The party that initiates the project and pays for its design and construction, in this case West-African Exploration and Production (WAEP)/NNPC JV.

1.2.2

Shall

This indicates a mandatory requirement.

Should

This indicates a preferred (but not mandatory) course of action

May

This indicates a possible course of action

Abbreviation ALARP

As Low As Reasonably Practicable

API

American Petroleum Institute

BS

British Standards

CEM

Cause and Effect Matrix

CR

Control Room

ESD

Emergency Shutdown

EWS

Engineering Work Station

RTU

Remote Terminal Unit

F&G

Fire and Gas

F&GDM

Fire & Gas Detection Mapping

F&GS

Fire & Gas System

FDS

Functional Design Specification

FEED

Front End Engineering Design

FMEDA

Failure Mode Effects and Diagnostic Analysis

FIREPRAN

FIRE PRotection ANalysis

GOR

Gas Oil Ratio

HART

Highway Addressable Remote Transducer

HMI

Human Machine Interface

HSE

Health, Safety and Environment

HVAC

Heating, Ventilation and Air Conditioning

I/O

Input / Output

IC&A

Instrumentation, control and automation

IASS

Integrated Automation and Shutdown System

IEC

International Electrotechnical Commission.

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1.3

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IP

Institute of Petroleum

IR

Infra Red

IS

Intrinsically Safe

ISA

Instrumentation, Systems and Automation Society

LED

Light Emitting Diode

LFL

Lower Flammable Limit

LFLm

Lower Flammable Limit meter

NAG

Non Associated Gas

OPC

Object Linking & Embedding for Process Control

OSD

Operational Shutdown

PA

Public Address

PAS

Process Automation System

PFD

Probability of Failure on Demand

ROR

Rate Of Rise

SER

Sequence Of Event Recorder

SIF

Safety Instrumented Function

SIL

Safety Integrity Level

SIS

Safety Instrumented System

WAEP

West-African Exploration and Production

JV

Joint Venture

KCDP-A

Kaleakule Drilling Platform

KCPP-A

Kaleakule Central Processing Platform

SCSSV

Surface Control Sub-Surface Safety Valve

TDC

Target Detection Coverage

TDO

Target Detection Objectives

TDP

Target Detection Perfromance

TuV

Technischer Uberwachungsverein (German body, Translates to Technical Inspection Agency).

UPS

Uninterruptible Power Supply

VCE

Vapour Cloud Explosion

Site Environmental Conditions Kaleakule Platform where the instruments and equipment shall be installed are located within the Niger Delta area; approximately 27km and 50 km respectively south of the Bonny River inside the shallow Offshore Waters – Water depths are 65ft (OML71) and 131ft (OML72).; . This means that for most part of the year, equipment and instrumentation will be installed and operated in

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environment with potential for saline corrosion and water ingress. The environmental data listed below give an overview of the conditions prevalent over these locations in general, for the purpose of selection and protection of the instruments. The environmental conditions (weather and MetOcean) at the Kalaekule field are considered typical of any shallow offshore location in the Niger Delta region. Available data shows that the extreme conditions in this region are driven by both sea wind and swells. Company is in the process of acquiring recent MetOcean data specific to OML-71 and -72. Water Depth: The Mean Sea Level (MSL) at Kalaekule platforms’ location (OML 72) is 19.0m.

Tides: The highest astronomical tide and storm tide shall be assumed to occur simultaneously. This total effect shall be considered in conjunction with both storm and operating waves and winds. The astronomical and storm tides are 0.75m each. Tables 1 below provide the available data on the wind and wave characteristics of the region for both operating and 100 year Table 1: Operating and 100 Year Return MetOcean Data Parameter

Operating Condition

100 Year Condition

Wave Height (m)

4.8

9.8

Wave Time Period (sec)

8.3

14.5

Current Speed Surface (m/s)

at

0.7

1.6

Current Speed at 2.3m from mudline (m/s)

0.3

0.8

Wind at one minute mean velocity (m/s)

16.5

31

Storm

Marine Growth: A 50mm radius increase shall be applied to the outside of all structural members between the mudline and elevation +3m above MSL for the purpose of simulating marine growth. Meteorological Data: The available meteorological data for the area are summarized in table 2 below. Table 2: Meteorological Data Minimum Air Temperature

20oC

Maximum Air Temperature

33oC

Minimum Seawater Temperature

22oC

Maximum Seawater Temperature

30oC

Wind Speed Gusting to

19m/s

Average Wind Speed

5.4m/s

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Maximum Wind Speed

8m/s

Pre-dominant Wind Direction (rainy season)

South-West

Pre-dominant Wind Direction (dry season)

North East

Raining Season

March-October

Dry season (harmattan, dusty air)

November - March

Maximum mean monthly rainfall

600mm.

Humidity :Maximum mean monthly value

93%

Humidity: Maximum recorded

100%

Significant Wave Height HS

Between 0.65 in winter and 1.45m in Summer

Wave Period

Between 4.0 and 5.0s

Barometric pressure

Approx. 1010 mbar (fairly constant all year)

All field devices, fittings and installation materials shall be suitable for and unaffected by the indicated climatic conditions.

2.0

APPLICABLE CODES & STANDARDS

2.1

List of Applicable Codes & Standards Design of the F&G system and the field devices shall be based on the standards and codes listed below in this document.

2.1.1

Master Practices–WAEP Local Engineering Practices

MPL 41-P-19

Diesel Systems

WLP 70-P-01

Loss Prevention - Facilities

WLP 70-P-03

Hazard Assessment

WLP 70-P-04

Offshore Platform Layout

WLP 70-P-05

Fireproofing

WLP 70-P-09

Fire and Gas Detection

WLP 70-P-13

Use of Composite Pipe in Offshore Firewater Service

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2.1.2

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International Standards ANSI 1638

Visual Signalling Appliances – Private Emergency and General Utility Signalling

BS 5839

Fire Detection and Fire Alarm Systems for Buildings

EN 54

Fire Detection and Fire Alarm Systems

EN 61779 1-5

Combustible (flammable) gas detectors

EP 95-0230

HSE Manual, Design

EP 95-0351

Fire Control & Recovery

IEC 60079

Electrical Apparatus for Explosive Gas Atmospheres

IEC 60529

Degrees of protection provided by enclosures (IP Code)

IEC 61000-4-3

Electromagnetic Compatibility (EMC) – Testing and Measurement Techniques – radiated, radio frequency, electromagnetic field Immunity test.

IEC 61000-6-2

Generic Standard Environment

for

Immunity

in

Industrial

IEC 61000-6-4

Generic Standard Environment

for

Emission

in

Industrial

IEC 61131

Programmable Controllers – programming languages

IEC 61508

Functional Safety of Electrical / Electronic Programmable Electronic Safety Related Systems

IEC 61511

Functional Safety of Safety Instrumented Systems for the Process Industry

Mode

2.1.3

WAEP Loss prevention procedures documents WLP 70-P-05 Loss Prevention Fireproofing WLP 70-P-07 Loss Prevention FIREWATER SYSTEMS AND DEVICES WLP 70-P-09 Loss Prevention Fire and Gas Detection WLP 70-P-11 Loss Prevention PORTABLE FIRE EXTINGUISHERS WLP 70-P-13 Loss Prevention USE OF COMPOSITE PIPE IN OFFSHORE FIREWATER SERVICE WLP 70-P-05 Loss Prevention Fireproofing WLP 70-P-07 Loss Prevention FIREWATER SYSTEMS AND DEVICES WLP 70-P-09 Loss Prevention Fire and Gas Detection

2.1.4

Project Documents

/

---

Platform Layout

----

PAS Architecture Diagram

---

Safety Instrumented System Specification

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2.2

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---

ESD & Safeguarding Philosophy

---

Instrumentation & Control Philosophy

---

Fire and Gas Specification

---

General Specification for Instruments

---

Process Automation System Specification

---

Process Safeguarding Memoranda

---

KCPP/KCDP Fire and Gas Cause and Effect Matrix

---

Safety Instrumented Classification and Report

Function

(SIF)

Order of Precedence In the event of conflicts between the above listed applicable regulations, codes and standards, the following priority order shall be applied: 

Nigerian Government legislation



Project Specification and Datasheets



WAEP LPPs



Industry standards



Vendor / contractor codes and working standards

Latest editions of all codes and standards as at the date of issue of this philosophy shall apply. Deviations from applicable rules, codes and standards shall be subject to written consent from WAEP.

2.3

Health, Safety And Environmental Requirements The Vendor shall at all times, maintain awareness of the Health, Safety and Environmental (HSE) legislation and regulations concerning safe and environmentally friendly working practices, and comply with these in the manufacturing, fabrication and testing operations pertaining to this specification. The Vendor shall institute and adopt the use of safe working practices and encourage, train and require their workforce / personnel and his sub-suppliers to comply with such practices at all times. The Vendor shall operate a formal Health, Safety and Environmental Management System and demonstrate in their bid how they comply with Health, Safety and Environmental policies and the requirements of HSE regulations. The HSE management system shall ensure compliance during design, manufacture and testing processes.

3.0

F&G SYSTEM PHILOSOPHY

3.1

FGS Scope Within the scope of this refurbishment project, the FGS is responsible for detecting fire and flammable gas. Toxic gas detection is not required; however the system shall be capable of incorporating this function in the future if required. This document is controlled electronically and is uncontrolled when printed

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3.2

FGS Purpose

3.2.1

General

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The primary purpose of the FGS is the protection of personnel, environment, equipment and reputation by:  Continuous monitoring of designated areas for release or accumulation of gas, fire or products of combustion (smoke),  Initiation of alarms to alert personnel to the hazard,  Initiation of executive actions to mitigate such events and to prevent escalation It is unlikely that the FGS will act quickly enough to reduce the size of the initial event. However the FGS shall annunciate the hazard and effect appropriate executive actions, to reduce the potential for escalation 3.3

Hazards The following hazards are expected from the facilities:          

3.3.1

Cellulosic fire Electrical fire Gas ingress Hydrogen build up from batteries Diesel fire Lube oil fire Gas Cloud VCE Jet fire Spray fire

Controlling Flammable Gas Hazards The role of flammable gas detection is to detect accumulations of gas, or gas migrating between areas, sufficiently early for shutdown actions to be initiated before flammable concentrations reaches key ignition sources. If process shutdown is initiated before the cloud has grown to such a size that its ignition could threaten the shutdown devices, the system can be considered to have performed its function. The detection of fugitive leaks is outside of the scope of the FGS

3.3.2

Controlling Fire Hazards The fire detection system shall detect fires early enough to allow shutdown actions to be reliably taken which minimise the risk to personnel and damage to facility. Priority should be given to gas detection over fire detection, as gas detection has a more ‘preventative’ role than that of fire detection. However, in cases where specific executive actions require a high reliability of incident detection, use of fire detection as an input may be appropriate

3.4

Fire Zones The fire & gas detection philosophy shall be developed around the concept of zones (often referred to as “Fire Zones”) Zones are identified process or geographic areas to which a particular fire & gas detection, alarm, and executive action strategy is assigned. Such strategy takes account of hazard characteristics such as platform layout and separation, boundary isolations, stored inventory, meteorological conditions, location of personnel and escape routes.

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Individual process modules are normally treated as separate zones except where the modules are in close proximity to one another and there is a high likelihood of a gas cloud or a fire enveloping more than one module. In this case, the modules concerned may be treated as a single zone. A key consideration is the location of effective boundaries or boundary isolations with respect to the likely events. Non-process areas such as offices, warehouses and other buildings are regarded as civil structures and treated as separate zones, often on a per room or per building basis. A detailed fire zones arrangement for the Kalaekule platform is shown in Appendix 4. 3.5

Voting FGS voting is the configuration of the FGS to consider the indicated status of more than one detector before executive actions are triggered. Detector voting is generally employed on a per zone basis. The purpose of voting is two-fold: 1. Removal of spurious alarms and executive actions by the fire system that would otherwise result from detector falsely indicating hazardous situations. 2. Allowing detector redundancy and online maintenance to be performed more readily and without compromising plant safety. The voting scheme shall be 2ooN (Fire,gas and smoke detection systems) and shall be done taking into account a number of factors including:      

Relevant standards The reliability of the detector correctly sensing a hazardous situation. The sensor placement and plant layout. Required SIL Rating of FGS. Sensor redundancy The magnitude of the risk being controlled

To ensure full consideration of plant operation, reliability, production continuance and maintenance activities, WAEP’s approval of the voting system is required. 3.6

Executive Actions In response to detected hazards, the FGS may trigger executive actions such as:      

Fire suppression systems Blowdown of platform or area Isolation of fuel or energy supply Annunciations such as sounders and lighting Activation or isolation of ventilation systems Remove notification of authorities’/emergency response groups

A Cause and Effects Matrix shall be prepared indicating a list of executive actions and their trigger conditions. Operator approval for particular executive actions shall be required in areas where automatic blow down of facilities is not required. For instance, in certain plant locations it may not be appropriate to blow down automatically as it will cause escalation of the hazardous event (e.g. a fire event affecting the flare/vent system itself) executive action shall be manually initiated at the discretion of the control system Operators.

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3.7

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Design Efficiency There can be a tendency to adopt a ‘more and better’ approach to FGS, especially regarding detector selection and position. Typically the largest component of the life-cycle cost of a FGS is maintenance. The design shall take into account the practicality, maintainability and overall lifecycle cost of the system.

4.0

FLAMMABLE GAS DETECTION

4.1

Detection Requirement Flammable gas detection shall be provided in all hydrocarbon process areas where accumulation of a flammable atmosphere is likely, or in open areas where early detection of large migrating gas release is beneficial.

4.2

Detection Technology Selection The remainder of this section outlines the various flammable gas detection techniques allowable on the project, and the philosophy to be applied for their selection and application. A table of the various detection techniques and their characteristic strengths and weaknesses is included in the appendices.

4.3

Selection Hierarchy This section lists various typical detection scenarios and the technologies to be used, in order of descending preference.

4.3.1

Boundaries/Areas Monitoring The first preference for gas detection is the application of Line-Of-Sight (LOS) techniques, due to its reliable and cost effective coverage of large areas. This technology is especially useful for detecting the migration of significant gas clouds between process modules and the accumulation of gas clouds within process modules.

4.3.2

Significant Potential Leak Sources In areas where there is a significant risk of leak (e.g. flanged or screwed joints), additional IR point gas detectors shall be employed e.g. combustion and ventilation air intakes. Acoustic Leak Detection may be considered for use in areas of open plant where there is little chance of accumulation and operator attendance is infrequent so that significant leaks may go undetected for some time. An example is the flanged sections where there is a risk of jet fire due to high pressure leaks. Acoustic Leak Detection may be used for detection of high pressure gas releases as the prime detection technology or in combination with conventional detection (open path / point).

4.3.3

Congested Plant Modules In congested areas within process modules where LOS detection is unsuitable due to the absence of any substantial sight lines, or where there is increased risk of accumulation due to confinement, then additional point gas detection shall be employed.

4.3.4

Ducting and Air Intakes Due to the potential difficultly of high air flows and maintenance access, it is preferable to protect an air inlet/duct from hydrocarbon gas using IR Point Detection in the vicinity of the intake, rather than inside the duct itself. Typically the installations protected would be combustion air intakes for gas generator, emergency diesel generators, HVAC inlets etc. This document is controlled electronically and is uncontrolled when printed

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If it is possible that concentrated gas might flow into the duct undetected using point detection, then Line-Of-Sight detectors across the duct cross-section shall be employed, with consideration given to how these detectors may be tested by maintenance in the future. Where maintenance access is an issue, then remote testing facilities or aspirated detection should be considered. 4.3.5

Difficult Access or Conditions For high temperatures such as inside motor enclosures, or difficult access conditions such as under-floor, aspirated detection systems may be employed. For forced ventilation enclosures, the outlet may be monitored for gas. Detection requirements for gas engine enclosures should be in accordance with applicable international standard/industry practice (Gas generator/turbines for the petroleum, chemical, and gas industry services).

4.3.6

Building Interior The first preference for protecting building interiors from hydrocarbon build-up is the detection of hydrocarbons much closer to their release in the field. If this is not possible then protection of the building air inlet is preferred. If this is not possible, then detection within the building should be employed.

4.3.7

Oil Mist Area A pressurised leak of flammable fluid may produce an explosive oil mist that cannot be detected by any of the previously described methods. In locations where this may occur, especially indoors, then Oil Mist Detection shall be considered.

4.4

Flammable Gas Connection Alarm Limits The following table indicates the alarm limits to be universally applied for gas detection systems, according to their application and technology. Approval from WAEP is required to vary from these values: Application/ Detection Technology IR Point Detection Catalytic Point Detection Gas Turbine/generator Ingression Line Of Sight Detection (IR)

Low Alarm Limit

High Alarm Limit

Comment / Explanation

20% LEL

60% LEL

If only a single alarm limit is used, then set to 50% LEL

20% LEL

60% LEL

15% LEL

40% LEL

1.0 LFLm

3.0 LFLm

Figures chosen to protect turbine from overspeed due to gas ingress into combustion air inlet i.e. High Alarm on :  10m gas cloud of 30% LEL, or  100m gas cloud of 3% LEL. Suggest calibrated FSD=5.0 LFLm.

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5.0

FIRE DETECTIION

5.1

Detection Requirements

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The primary purposes of fire detection are to:      5.2

Detect any fire in its early stages Alert the operator and personnel Minimise the potential for escalation by isolating the flammable inventory and where appropriate, depressurize the affected and/or adjacent unit or system. Contribute to possible firefighting actions. Contribute to the safety of both on and off site personnel.

Detector Technology Selection A critical aspect of all of the fire detection goals is the earliest practical reliable detection of a fire or potential fire. Fire detection technologies are used either to detect flame directly, or detect the heat and smoke by-products of combustion. A table of the various detection techniques and their characteristic strengths and weaknesses is included in the appendices. Further details can be obtained from WAEP LPPs (Loss Prevention Procedure for Fire, gas and smoke detection systems). The specification and Installation section later in this document details implementation and project standards associated with each technology.

5.3

Selection Hierarchy In contrast to gas detection which must address the migration of gas throughout a processing plant, fires generally start in defined locations where fuel is known to be available, and then move / spread relatively slowly. Hence fire detection is typically more focussed on specific locations where fuel is located and likely to combust (such as generator/turbine enclosures or LPG loading bays, etc). This section lists various typical detection requirements that typically exist on platform/plant, and the technologies to be used, in order of descending preference.

5.3.1

Wide Area Coverage The first preference for wide area coverage (e.g. load-out jetty) is Triple Band IR Flame Detection, due to its fast response time and cost effective coverage of large areas. Depending upon location / installation, backup protection may be implemented using heat detection, due to its high reliability and very low false trigger rates.

5.3.2

Single Point Coverage The first preference for covering a single area (e.g. metering skid) is Triple Band IR Flame Detection, with possible heat detection (e.g. fusible loop) employed as a backup. In applications where IR Flame Detection is not attractive (due to requirements for ultra-low maintenance, or sub-zero temperatures, etc) then heat detection mounted directly above the area may be employed and no IR is required.

5.3.3

Congested Platform/Plant Modules The same approach as for Single Point Coverage (above) shall be applied.

5.3.4

Inside Enclosures Triple Band IR Flame Detection is the preferred option, where adequate sight lines exist inside the package and the ambient temperature of the enclosure allows installation of the sensors. Consideration shall be given to installing heat detectors near the ventilation outlet as a backup to This document is controlled electronically and is uncontrolled when printed

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the IR detectors. Where no substantial enclosure ventilation occurs, then consideration shall be given to installing heat detectors high-up in the enclosure. For heat producing packages such as diesel engines housed inside an enclosure, compensated rate-of-rise heat detectors shall be installed as a back up to the IR detectors. Activation of a single heat detector shall be regarded by the associated FGS as a confirmed fire and all associated executive actions shall be triggered. Where enclosure temperatures exceed the capability of the IR detectors, alternative techniques may be employed. One option is the use of UV type fire detectors, however they shall not be employed in dusty environments, for fires that produce heavy smoke, or where airborne oil droplets may exists. WAEP approval is required for the use of UV type sensors due to their tendency to false trip due to welding, X-rays (as used in on-site non-destructive testing), sunlight and lightning. UV type sensor shall not be used to trigger potentially destructive executive actions. 5.4

Other Selection Scenarios The following is a discussion of other typical scenarios where fire detection system selection is required for projects:

5.4.1

Building Interiors All non-process buildings/carbins shall be fitted with redundant optical type smoke detectors in their interiors. All HVAC intakes shall have redundant ionisation type smoke detectors. Where a building is not adequately sealed from dusty / dirty conditions then consideration may be given to the use of ceiling mounted point heat detection in lieu of smoke detection. Single detection of smoke or heat shall be regarded as a confirmed fire for that zone, and all executive actions shall be triggered.

5.4.2

Critical / High Value Equipment For location with critical and /or high value equipment installed, such as instrument, telecoms and switchgear equipment, the use of a High Sensitivity Smoke Detection (e.g. VESDATM type) system may be considered, especially for detection of combustion in difficult access areas such as under floor and ceiling areas. These High Sensitivity Smoke Detection systems detect pre-combustion emissions from material, and hence allow intervention prior to the equipment being damaged by smoke and /or effort to contain the subsequent fire that might develop. High Sensitivity Smoke Detection systems are sensitive to dust ingression, can be prone to false alarms, and also require significant maintenance. Hence the genuine usefulness of the early warning offered by these high sensitivity systems need to be well demonstrated to justify their usage. A high sensitivity smoke detection system shall be used for alarm only. Approval of the Principal is required for inclusion of this type of system.

5.4.3

Wellheads Wellheads shall be protected by heat detectors which perform the executive action to close the well in the event of a 2ooN detection indicating confirmed fire. This shall be implemented using suitably rated fusible alloy plugs installed in the hydraulic supply lines to the SSSV, SCSSV and Wing valve actuators, at the wellhead. In the event of fire at the wellhead, the fusible alloy plugs will fail causing the hydraulic pressure to be vented from the springreturn valve actuators, resulting in closure of the SSSV, SCSSV and Wing valves.

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The hydraulic control system shall include low pressure alarms to alert the operator to loss of hydraulic pressure. 5.4.4

Gas Generator Enclosures Detection requirements for gas generator enclosures shall use triple band IR detectors, and compensated rate-of-rise heat detectors installed in accordance with applicable international standard. IR detector locations shall be selected so that all possible fire locations inside the enclosure are monitored from two different angles / detector locations. A single detector location indicating fire triggers an alarm. Two different detector locations indicating fire in the same location shall trigger executive action. Additionally, each detector location shall have a pair of detectors installed for equipment redundancy. UV type flame detection shall not be used.

5.4.5

Low Hydrocarbon Fires For outdoor applications, heat detection shall be used. Multiple point detection is preferred. Fusible Loop (linear) detection may be employed where an excessive number of point detectors would be required for coverage, or where a mechanical / hydraulic triggered automatic deluge is required. For indoor applications, UV type flame detection may be considered only with the approval of WAEP. Careful consideration of redundancy, voting systems and operator approval of executive actions shall be considered.

5.4.6

Manned Areas Manual alarm call points shall be provided in all living quaters, located adjacent to fire points and exits. They shall also be provided at designated locations on personnel egress routes within the platform facilities. Activation of any manual call point in either a building or process area shall be regarded by the associated FGS as a confirmed fire in that zone and all associated executive actions shall be triggered.

6.0

SYSTEM DESIGN

6.1

General The process facility shall have a suite of Instrumentation, Control and Automation (IC&A) systems, which comprises Process Automation System (PAS), Safety Instrumented System (SIS) and Fire & Gas Detection System (FGS) installed in the refurbished Kalaekule Platform. The new FGS shall seamlessly integrate with the SIS but shall be functionally separate from the SIS. All the F&G devices installed shall interface with the new PAS, SIS / F&G system cabinets provided for the Project except where advised otherwise by the Company. All fire & gas detection and safeguarding functions shall be executed separately from the SIS. The PAS shall act as the main human-machine interface for all IC&A system including FGS. The FGS shall be responsible for all logic and shutdown functions associated with the detection of flame, heat, smoke and flammable gases. Any executive actions required (e.g. shutdowns, depressurization and inventory isolations) shall be performed indirectly, via the main SIS system.

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The well head shall be supplied with fusible loop for fire detection and shut down of the wells. 6.2

Main Fire And Gas Detection System (FGS) The main FGS shall be located in the Kalaekule Platforms control room. The FGS shall continuously monitor each zone for any potential hazards, and on detection the FGS shall raise an alarm, bring up the appropriate displays, and (may) initiate executive actions in accordance with the voting system adopted. The FGS shall have native compatibility with the full range of detection and manual initiation devices required in the design. Complex interface conversion devices shall not be employed between the FGS processor and its field devices. The FGS shall have in-built self diagnostic capability with data interfacing facilities to the PAS for fault reporting and visual display of project wide FGS status and alarm conditions. The FGS shall be capable of driving hard-wired mimics. Provision shall be made for hardware to be tested on-line using maintenance overrides.

6.3

FGS input The FGS shall be designed with hard-wired field detector inputs. All input circuits shall be continuously monitored for open circuit and closed circuit fault conditions. Alternatively, inputs may use digital data bus connections to the field sensors; however consideration of the SIL requirements and approvals ratings of the detectors shall be considered in accordance with company LPP and process control philosophy. The use of 0-20 mA transmitters which communicate sensor diagnostic messages in the 0-4 mA range is encouraged over simple open / closed switch indicating type sensors is preferred. Input cards as a minimum shall have status LEDs to indicate input status, override status and fault status. For process area related detectors, there shall be one input to the FGS per detector, allowing each individual detector to be identified on the HMI interface, unless another approach is approved by the Company. For detectors in buildings, the inputs may be combined on a per zone basis, allowing many detectors to be combined using field wiring and then connected to a single FGS input. (Field circuit integrity monitoring must be maintained).

6.4

Voting Modules Voting modules shall have status LEDs to indicate the status of each input channel / the output status (vote) and fault status as a minimum.

6.5

FGS output Output channels as a minimum shall not have output overrides. Output channels shall have status LEDs to indicate output status and fault status. All output circuits shall be continuously monitored for open circuit and closed circuit fault conditions. Executive actions derived from automatic or manual initiation of the FGS shall be routed by hardwired connection to the ESD/OSD system, except for certain executive actions which shall be performed directly from the FGS system (such as local deluge systems). Output shall be fail-safe (normally closed or normally energised) unless the consequences of a spurious trigger of the executive action might result in excessive damage to plant or personnel, or pose an unnecessary hindrance to plant operations (for example, deluge/foam systems). This document is controlled electronically and is uncontrolled when printed

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FGS Power Supply The FGS shall have a separate power supply to the PAS and SIS systems. Failure of the PAS or SIS power supply shall not affect the FGS. The FGS systems shall be powered from redundant Uninterruptible Power Supplies (UPS). UPS output shall conform to the following:   

6.7

Output Voltage: Frequency: Max THD:

230 VAC +5% 50 Hz +1% 5%

FGS and SIS Physical Location As part of the integrated IASS system, the design, implementation, geographical locations and architectural layout of the processors, communications and interfaces of the FGS shall be similar to the SIS or process control system..

6.8

Civil Facilities Civil facilities are enclosed structures not directly related to the plant processes. Examples of civil facilities include crib-rooms, sleep quarters, etc. However, analysers’ houses, FAR or switchroom buildings/contaniners are directly related to the process and hence are not civil facilities. Civil facilities shall be subject to the same philosophy as the rest of the process facility, except for variations listed in this section.

6.8.1

FGS Separation & Architecture: Civil facilities shall have fire detection systems entirely separate from the process FGS and these shall be in accordance with the relevant building codes. Each civil facility building shall have a separate FGS control unit that interfaces to the building’s detectors and alarm indicators. The FGS systems shall be designed with hard-wired field detector inputs and outputs, with all input and output circuits continuously monitored for fault conditions.

6.8.2

F&G Alarm Panel Interface: The F&G alarm panel shall include status LEDs to indicate power supply status, input status, override status and fault status as a minimum, and these indications shall be provided at or near the FAR’s (Control room carbin) main entrance.

6.8.3

Detectors: Typically the FGS system will employ smoke detectors, and possibly heat detectors, in accordance with the building interiors section of this document. Where addressable detectors are used they shall have a unique address (e.g. IP) for each detector head. Additionally, manual alarm call points (break glass units) shall be easily triggered by personnel leaving the building from any of the building exits. Typically this requires manual alarm call points be installed near the buildings access points. Where practical manual alarm call points shall be installed on the outside of the building, as this allows personnel to operate the call points without having to enter or remain inside the building.

6.8.4

Annunciators: Each building shall have an audible alarm fitted to its interior (typically hallway mounted), as a minimum. External audible alarms are recommended. Audible fire alarms for buildings shall be either a continuous bell or intermittent alarm. There shall be no all-clear signal in keeping with corporate HSE policies. This document is controlled electronically and is uncontrolled when printed

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Complex Equipment Package FGS Systems Complex equipment packages have their own dedicated package FGS embedded within the package. All package FGS shall comply fully with all the requirements detailed in this philosophy for the main FGS.

6.9.1

Package FGS Integration The package FGS shall be fully integrated into the main FGS as a daughter node, using either hardwired connection or a certified digital network. Integration includes propagation of FGS information to the PAS HMI and SER. Wherever practical, alarms and status information from the package FGS shall be transmitted in full to the PAS and not grouped into common alarms prior to transmission.

6.9.2

Package Independence All FGS functions required for packages shall be managed locally by the package FGS so that failure of the communication link between the package FGS and main FGS does not impede the local FGS from safeguarding the package. Exception to this is where operator intervention is required prior to triggering executive actions (such as operator triggered deluge of compressor enclosures).

6.9.3

Field Cabling and Terminations The main Automation Contractor (MAC) shall be responsible for ensuring the supply of the required field cabling between the equipment package and the main FGS and SIS systems, marshalling, field termination assemblies (FTAs), I/O and logic.

6.9.4

Vendor Testing and Package Integration The FGS shall be fully tested and pre-commissioned as a component of the Vendor’s integration and testing activities, preferably at the Vendors’ workshop. Where the package is composed of separate modules, it is preferable that these are integrated and the FGS tested as a completed package prior to shipment to site. Reducing the amount of on-site modification and re-testing of the FGS improves the overall final system integrity. Hence the Vendor’s site shall be used to perform all practical system testing and integration prior to shipment of the package.

6.9.5

Hardware Preferably, the package FGS will be implemented using hardware identical to the rest of the project. If this is not practical then packages shall employ FGS equipment consistent with the facilities to ensure seamless integration with the process FGS. Careful consideration shall be given to rationalisation of hardware spares and maintenance activities. Even if it is not practical to use the FGS processor as the main, it is preferred that the same field equipment be employed as this simplifies spares, maintenance, troubleshooting and calibration activities for the lifetime of the system.

6.9.6

Standard Compliance All safety functions implemented in package controls shall be designed in accordance with IEC 61508 / 61511 standards. External third-party certification such as TüV compliance of the hardware and software implementation of the safety-related functions shall utilise the standards of IEC-61508 / 61511.

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Simple Equipment Packages Simple equipment packages (e.g. electric motor driven pumps) are packaged systems supplied without their own FGS. Simple equipment packages shall be considered part of the general platform; hence any fire and gas detection shall be performed using the main FGS system. The ICSS Contractor shall be responsible for ensuring that all F&G sensors, junction boxes and connecting cables that are deemed within the scope of supply of the equipment package supplier shall be identical in make, model and technical specification as those specified for the general plant in which the equipment package is located. The equipment package supplier shall be responsible for correctly installing and terminating the package F&G detection sensors, cables and junction boxes. The FGS system supplier shall be responsible for the supply and designation of the required FGS marshalling, FTAs I/O equipment and logic for inclusion into the main FGS protection scheme.

6.11

Sequence Of Event Recording Sequence of Event Recording (SER) for acquisition, storage and short-term retrieval of timestamped event data shall reside within the PAS. In summary, all SER information from the ESD/OSD and FGS systems shall be time stamped at source, then transmitted with the time stamp to the PAS. The PAS shall by default combine SER information from various sub-systems with its own alarm list and audit trail, so that a complete sequence of events can be presented to the operator.

6.12

Maintenance Overrides All input to the FGS that initiate executive actions shall be provided with maintenance override facilities to allow testing of such inputs. Operation of the override shall only affect the input to the voting logic and alarm functions shall not be affected. Initiation of an input override shall be indicated locally on the FGS input card, repeated on the FGS mimic display and recorded as a time-stamped event in the PAS based sequence of events recorder. Logic output overrides are not allowed.

6.13

Scalability In keeping with the requirements for the SIS, of which the FGS is a modular part, the FGS hardware and software shall be of scalable and modular design with adequate segregation to permit bumpless incorporation of new modules and shutdown of existing modules with minimal disruption of safeguarding functions. A shutdown and electrical isolation of a plant module shall not adversely impact any of the FGS functions within the active modules.

6.14

Certification External third-party certification such as TüV of the FGS hardware and software shall be fully compliant with IEC-61508 / 61511 standards. The FGS processor and architecture shall be selected to be capable of a minimum of SIL 3, even if the SIL assessment identified lower SIL capability as being required. This allows for future implementation of SIL3 functions without having to change out the entire FGS system. Higher SIL level assessments might be indicated by the structured risk assessment.

7.0

HUMAN MACHINE INTERFACE

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PAS Displays Mimic displays on the PAS shall allow an operator to view the status of the F&G . The PAS HMI shall give the operator sufficient information to quickly assess an incident and initiate the appropriate emergency procedures. This information shall include an overview of the status, identity, current value and location of individual F&G end elements in alarm and shall provide early warnings of impending problems with the ability to track the course of an individual event. The information displayed shall include (where applicable):      

7.2

I/O status Diagnostic information Abnormal situations Analogue values from trip transmitters Status of maintenance overrides Deluge/extinguisher release status Metrological data such as wind speed and direction

Geographic Mimic Panels Executive actions dependent upon operator intervention shall require a hard-wired FGS Geographic Mimic Panel. The mimic panel shall be provided in the platform control room. The mimic panel shall display the zone of a detected hazardous event with sufficient precision to identify the location of the event.

7.3

Alarm Annunciators Zone alarms shall be annunciated through the PAS mimic displays. Each zone shall have a detailed mimic display in the PAS indicating the precise detector in alarm. FGS system audible alarms shall be compliant with industry standard (Fire, gas and smoke detection systems), and comprise a combination of site sirens supplemented by individual alarm sounders mounted in strategic locations where it may not be possible to hear the site siren (e.g. in areas of high noise and within site buildings). Sounders shall be located to provide adequate coverage of the platform facilities. In areas with a high ambient noise level, visual alarm shall be provided.

7.4

FGS Response Time The FGS system has the potential to be multiple-layer architecture, with potentially a large number of processors, bus networks and communications links between the field sensor(s) raising an alarm, the voting logic, the executive action being triggered in the field, and the HMI indication(s). Considerations shall be given to the system’s architecture, interfaces, buffers and processors to ensure the safety of the asset protected by the FGS is not degraded due to communications delays.

8.0

DETECTION AND FIELD MOUNTED EQUIPMENT

8.1

General The correct installation and positioning of detectors and annunciators is of critical importance. This section provides additional information on the selection and installation of field mounted equipment. Device selection shall observe the Company’s preferred Vendor list(s).

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Detector and Annunciator Layout Detector and annunciator layout shall be shown in the Fire and Gas Detection Plan. The optimization of this plan shall include as minimum the following:    

Final device numbers Types Locations (including height) Orientations

Optimization shall include the use of analysis tools such as FIREPRAN (Fire Protection Analysis) which are used to assess the hazards. Development of the Fire and Gas Detection Plan takes into account a large number of factors. Below is subset of typical considerations:           

Likely fuel release points (Flanges, vessels, vents, etc.) Gas release type, velocity, density, temperature, JT-Cooling on release. Likely accumulation areas for fuel (such as densely packed process structures for gas, bunds for liquid). Explosion intensity (affected by structure density and plant topology). Potential ignition sources (flares, kilns, etc.). Gas sensitive process equipment (Gas Generator over-speed due to ingestion). Likely migration paths of gas clouds (from release to an ignition source or populated area). Provision and protection of escape paths and safe refuges. Manning levels, maintenance activities and behaviours, and typical personnel locations. Triggers for hazard release (an unmanned site is likely to experience leaks during maintenance, which is when personnel are there and at risk). Secondary damage as a result of initial event, such as shockwave damage to tanks, heat affecting structural integrity of structures.

In accordance with WAEP HSE systems, the analysis performed to develop the fire and gas detection plan shall be performed addressing all four possible risk types: 1. 2. 3. 4. 8.3

People Assets Environment Reputation

Field Device Hazardous Area Protection Rating Field devices used in process and utility areas shall be ex-certified for use in Zone 1 hazardous areas as a minimum.

8.4

Ingress Protection All field instrumentation shall be protected to a minimum of IP65. Painting and other exterior treatment shall be proven suitable for the environmental conditions specified in the project design data sheets.

8.5

Gas Detection Elements Most common gas detection elements (irrespective of their packaging) rely on one of these two principles: 1. IR Absorption 2. Catalytic (Pellistor)

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Where practical, IR technology is preferred unless the catalytic technology is required to ensure sensitivity to specific fuel types (such as hydrogen, which cannot be detected by IR absorption). 8.6

Calibration Gas Where a single gas type is being detected, the sensor shall be calibrated on this type of gas. Where a range of gas types are being detected, the Manufacturer shall be consulted to determine which of the possible gases the sensor is least sensitive to (for hydrocarbons, the worst-case gas is most likely to be methane). The sensor shall be calibrated using the worst-case gas mixed in air. This ensures the minimum required sensitivity is achieved for all gas types.

8.7

Line-Of-Sight Gas Detectors Flashgun (pulse light) type detectors are preferred as these are the most reliable. Detectors of the type that utilise a separate transmitter and receiver shall be selected. Combined transmitter-receiver types that utilise retro-reflectors shall not be used as these halve the effective path length.

8.7.1

Boundary Monitoring Consideration should be given to using two pairs of detectors for each path, with 2ooN voting applied, where two detectors are employed on a single path, they shall be configured with both a transmitter and a receiver at opposing ends of the path (i.e two opposing beams).

8.7.2

Area Monitoring At minimum, two detectors shall be used for area monitoring.

8.7.3

Installation The recommended path length for open path detectors is 20 to 30 meters for offshore applications, and 30 to 60 meters for onshore applications. LOS detectors must be mounted on substantial, laterally-braced supports that do not flex or vibrate to ensure consistent alignment. Typically the optical alignment accuracy is of the order of 0.5 to 1 degree, and this must be taken into consideration for structures that experience varying structural loading, or are subjected to differential heating, as both of these can lead to ongoing sensor alignment problems. Typically, LOS detectors are mounted 3 to 5 m off grade or deck. Where possible, floor markings should be used to show LOS optical paths in order to avoid inadvertent obstruction.

8.7.4

Sensor Robustness LOS detectors shall be unaffected by short-term beam blockages. Blockages greater than 60 seconds duration shall result in a beam blocked warning. Blockages greater than typically 5 minutes shall indicate that the detector is in fault. Routine maintenance of IR LOS type detectors requires cleaning of the sensor windows only. Calibration tests require the introduction of a piece of calibrated film into the beam path. Each instrument shall be provided with software to compensate for drift by utilisation of an autozero tracking system.

8.8

Point Gas Detectors Test gas inlet to be provided for calibration and testing of sensor operation. Remote facilities shall be provided where sensors are not readily accessible, e.g. inside ducting. This document is controlled electronically and is uncontrolled when printed

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Air Intake / Outlet Gas Detectors The Company’s list of approved Vendor and detector list shall be consulted when selecting detectors for air inlet / outlet and ducting, and the units selected shall be specifically suited to this task. Consideration shall be given to the following:     

8.10

Ease of maintenance, testing and calibration Vibration resistance and vibration free mounting Poison resistance Response time Detectors employing a filter element or flame arrestor between the ambient air and the detection element shall be avoided, as the high air flows in the duct will lead to clogging.

Accoustic Leak Detection Acoustic Leak Detectors (ALD) are suitable for early detection of significant gas leaks from pressurised sources above 15 barg by detection of ultrasound generated by the leak source. Acoustic leak detectors do not differentiate between flammable and non-flammable gas leaks. ALD should be considered for use in areas of open plant where there is little chance of accumulation and where operator attendance is infrequent so that significant leaks may go undetected for some time. Cognisance should be taken of the module / area risk contribution. ALD may detect ultrasound from other sources such as gas turbines, compressors, pipe work, valves and routine operations such as venting. Detection (alarm) threshold settings should be at least +6 dB above background level. Default alarm threshold settings of 74 dB and 84 dB are recommended for quiet and noisy areas respectively. Time delays may need to be set to allow for short-term venting operations and / or operation of pneumatically actuated valves. Detector types that include integrated self-test capability are preferred. ALD should be commissioned initially to operate in ‘alarm only’ mode and any executive actions will be overridden.

8.11

Gas Detector Location And Mounting Gas sensors should not be mounted less than 1 meter above grade or decking to avoid damage or fouling by splash water. In all cases the location of detectors shall accommodate access for maintenance, with either specific maintenance access provided or alternative facilities such as remote calibration provided.

8.12

Flame Detection

8.12.1 Technologies The primary means of detecting hydrocarbon-based fires shall employ triple-band infrared (IR) type optical flame detectors, as this type of detector provides high reliability without spurious alarms. IR detectors shall not be used for the detection of methanol fires. Ultraviolet type flame detectors are suitable for the detection of non-hydrocarbon fires such as methanol and hydrogen, with the Company’s approval. They shall not be used for detection of hydrocarbon fires. Optical integrity features shall be built into the electronics for self-checking and diagnostic purposes. The detectors shall be solar-blind.

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8.12.2 Installation Flame detectors shall be located as determined by the Fire Safety Assessment, to monitor equipment containing major flammable inventories and likely fire sources. Detector location and coverage, spacing and orientation shall take into account any obstructions. Detectors shall be supplied complete with adjustable mounting brackets that allow the detector alignment to be adjusted on both vertical and horizontal planes and shall be mounted in accordance with manufacturers’ recommendations. Detectors shall be located and oriented such that they cannot be accidentally triggered by detection of flare systems (including reflections off equipment) under high flame conditions. 8.13

Smoke Detection

8.13.1 Technologies Typically Ionisation type smoke detection will be employed, due to their high sensitivity to fully formed fires. Optical type detection is suited to detecting smouldering fires, but relatively insensitive to fully formed fire. Hence when Optical Smoke Detection is employed, additional heat detection shall be included to detect fires that build up rapidly without smouldering. 8.13.2 Installation Smoke detectors are suitable for indoor use only. All smoke detectors covering a single zone may be ‘daisy chained’ to a single FGS input card such that activation of any single detector raises an alert and triggers executive actions for that zone. Other types of detector in the same zone shall not be connected on the same loop. The detectors shall incorporate a latching indicator that preferentially is an LED which illuminates when the detector is in the alarm condition. It shall be reset from the fire and gas control panel only. Detectors in inaccessible areas (e.g. floor / ceiling voids) shall have the capability of driving a remote indicator lamp. The system certification for the detector shall include its use with the indicator. Maintenance access (e.g. hatches) shall be provided. Detectors shall be plug-in type. The sensor head assemblies shall be constructed so that the base may be installed without the sensing element and all field wiring terminations made and sealed against the atmosphere until subsequent installation of the sensing element at the precommissioning stage. 8.13.3 High Sensitivity Smoke Detection: High sensitivity smoke detection systems if fitted should be of the optical type and should include an alarm to denote when any of the sampling system flow rates fall below acceptable limits. High sensitivity smoke detectors of the type that detect chlorine emissions from overheated PVC type cable insulation are not recommended as experience has shown that they are ineffective at detecting emissions from low-chlorine emission cables which are now in common usage. 8.14

Heat Detection Heat detection shall be employed where high reliability and low spurious trips is required and slow response time can be tolerated. Heat detection shall be considered as a backup to optical system which is faster but less reliable. In open, naturally ventilated areas point heat detectors should be sited with a density in the order of one detector per 25 m² and at a maximum spacing of up to approximately 7 meter apart. The maximum distance from a bulkhead should be approximately 3.5 meter. This document is controlled electronically and is uncontrolled when printed

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In enclosed mechanically ventilated modules, point heat detectors should be sited at a density of at least one per 37 m² and at a maximum spacing of up to approximately 9 meter apart. The maximum distance from a bulkhead should be approximately 4.5 meter. 8.14.1 Voting Confirmation of fire detection is typically required before Executive Action is taken in response. In a 2ooN voted configuration, triggering of two detectors in a zone is classed as “Confirmed fire”. Point heat type devices shall not be voted. Pneumatic fire detection systems may be voted at the discretion of the Principal. If voting is deployed, then first detection loop provides an alarm, with the second loop detection providing Executive Action. Detectors used to automatically shut down machinery / plant equipment and initiate the fire protection system shall be voted in a 2ooN configuration. 8.14.2 Point Heat Detection The preferred heat detector characteristic shall be combined rate-of-rise-compensated and fixed temperature threshold type. These characteristic detectors alarm on when either:  

Absolute temperature exceeds a predetermined value in degrees, OR Temperature rises at a rate faster than a predetermined value in degrees-per-minute.

The sensor head assembly shall be constructed so that the base may be installed without the sensing element, all field terminations made and then ingress protected until the subsequent installation of sensing element at the commissioning stage. The detector package shall consist of the detector, base and termination box. 8.14.3 Linear Heat Detection Linear heat detection is performed using Pressurised Fusible Loop (polyflo tubing or fusible plug) type fire detection systems, which offer slow response times and high reliability. Fire detected inputs to the FGS from fusible loop shall be via a pressure transmitter interfaced with the FGS I/O via an analogue input card. Executive actions may be triggered directly from the pressure drop in the detection loop, such as deluge system valves opening or well head SSSV closure on loss of detector loop pressure. The installation shall give careful consideration to the mechanical integrity and protection of the loop, especially where polyethylene piping is involved. Approval from the Company is required for the use of pressurised fusible loop systems. 8.15

Manual Call Point Manual call points associated with civil facilities shall be of the break-glass type. Manual call points associated with process facilities shall lock on activation and require a separate action to release the switch. Manual Call Points shall be installed at strategic locations around the facilities. Manual call points shall be positioned so that they stand out against the background, i.e. they shall be clearly recognizable from a distance. If necessary they shall be provided with signs to enhance their visibility from access routes. Manual call points should be positioned as follows:

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1. Along routes in the platform area at intervals not exceeding 100 m, preferably at or near to lamp posts; 2. Near or at locations having a higher risk such as remote pump floors, manifolds, motor control centres and Wells. 3. Inside Carbins, office/control room entrance etc. 4. Inside the process area and positioned:    8.16

Outside room(s) Outside hazardous enclosed areas Along logical escape routes

Audible Alarm Sounders FGS system audible alarms shall comprise a combination of    

Site siren Individual alarm sounders Visual indications Civil facilities sirens.

Field-mounted fire and gas alarm annunciators shall be powered from critical supplies that have the same (high) availability as the main FGS system supply. The tonal characteristics of each alarm are dependent upon the location / type of the alarm annunciator and the type of hazard triggering the alarm. The tonal characteristics of the alarms shall be in accordance with the Alarm Tone Table in appendix 3. 8.16.1 Site Siren Wide area coverage shall be implemented using high-reliability electric-motor operated sirens that emit an on-off modulated tone. 8.16.2 Individual Alarm Sounder Where additional local enunciation is required, individual alarm sounders shall be installed. They shall have facilities for adjustment to the sound level. In area where there is a public address (PA) system the local audible alarms shall be temporarily silenced during PA announcements. 8.16.3 Civil Facilities Fire, gas and smoke alarms in buildings, including auxiliary/control rooms and offices, shall be annunciated in the buildings themselves by means of a sounder with the same sonic characteristics as individual alarm sounders. These alarms shall be temporarily muted during public address (PA) system announcements. 8.16.4 Visual Alarm Device Where it has been identified that beacons are required for high noise areas, e.g. compressor or generator area, weatherproof flashing xenon beacon(s) shall be employed. The beacon assembly shall be a tough impact resistant material and coloured red (See Appendix 3).

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Lightning Protection It is major concern that all systems shall be designed to have a very high tolerance to lightning strikes, which are prevalent in the area. In order to reduce the effects of lightning strikes on the electronic control and safeguarding systems, the following steps shall be taken; safeguarding systems denote any Safety or F&G loop devices and system hardware. Control denotes any electronic control or indication loop device and system hardware. Cabling systems for both power and signalling shall be protected by means of the installation of proprietary anti-surge devices, which route surges to earth thus protecting the equipment. Typically anti-surge devices shall be installed on the main power incomers to the control room or equipment enclosure. Additionally, individual electronic systems shall be protected by surge protection devices in their power supplies and individual signal and data lines. Surge protectors shall also be installed on antenna connections to the various radio systems. For field instruments, locally mounted surge protection devices shall be used depending on their criticality and consequences of failure of the particular instrument.

9.0

QUALITY ASSURANCE AND CONTROL The following quality assurance reviews and studies shall be performed, as a minimum, to verify conformance of the Fire and Gas System’s design with the relevant industry, corporate and WAEP standards and specifications. All QA / QC reviews shall be the EPC Contractor’s responsibility, performed according to the Principal's approved methodology as stated herein and in the relevant specifications, devolved to the respective equipment manufacturers where applicable and witnessed by the Principal (WAEP).

9.1

Cause And Effects Review A multi-disciplinary review of the Fire Zone Schedule and FGS Cause and Effects shall be performed, covering all facilities, modules, packages and systems, and involving the relevant Process, Safety, Operations, Maintenance, Rotating Equipment and Control & Automation personnel. Its purpose shall be to assure that the design is safe, operable and robust; aligns with the operating and maintenance procedures; guarantees overall safety of the facilities and affords the necessary operational and maintenance flexibilities without introducing any unwarranted conditions or constraints.

9.2

FGS Risk Assessment (SIL classification) Following the detailed HAZOP of each facility, module, package or system within the facility, all proposed safety instrumented functions identified in the FGS shall be classified according to the methodology defined in the WAEP’s specification documents.

9.3

SIL Verification (FMEDA / PFD Calculation) Following the SIL classification and equipment selection for use in the respective safety functions, failure and reliability analysis shall be undertaken in accordance with the requirements of IEC61508 to verify that all equipment making up each safety function in each facility, module, package or system provide the necessary risk reduction and meet the SIL classification applicable to that function. In the absence of certified failure rate data for any specific equipment, it shall be verified that the “proven-in-use” criteria in the context of IEC 61508 are fulfilled and substantiated.

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Reviews and Audit by the WAEP WAEP shall perform a variety of technical reviews and audits to verify conformance with the pertinent specification requirements. Participation in these audits and implementation of the recommendations arising from them shall form part of the scope of design and delivery for all control and automation systems and equipment.

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APPENDIX 1- FLAMMABLE GAS SENSING TECHNOLOGIES

Name

Method of Detection

Usage

Strengths

Weaknesses

Line Of Sight (LOS)

Detects absorption of IR wavelengths by hydrocarbon gas, from a beam of light directed along the sensitive area.

Cost effective coverage of large areas and boundaries. Fast response. High reliability.

Sturdy structures for mounting required. Can trigger on large size/low concentration gas clouds. Cannot detect all gases (such as H2).

Point Detection (IR absorption)

Detects absorption of IR wavelengths by hydrocarbon gas, from a beam of light contained entirely within a ventilated sensor head Detects the ultrasonic noise associated with a high pressure (sonic) release of gas

Boundary coverage with single instrument Area coverage with two instruments (crossed beams) Lengths 4 to 200 m possible. Typically 20-30m offshore & 40-60m on shore. Point detection of hydrocarbons. Used around point releases, congested areas, ducting, air inlets.

Fast response. High reliability & failsafe behaviour. Low maintenance. Poison resistant. Self-diagnostic.

Sturdy structures for mounting required. Can trigger on large/low concentration gas clouds. Cannot detect all gases (such as H2).

Point detection of hydrocarbons in a well ventilated area where gas build-up may not occur adequately for other detection systems.

Detect a wide range of gases. Detects a gas leak in high ventilation area well before gas build-up can occur.

Point or line detection of hydrocarbons in harsh environments (such as turbine enclosures) or confined spaces.

Can monitor wide range of gases and conditions.

Only detects high pressure releases. (Low pressure release or evaporating pools will not trigger). Well understood/predictable ultrasonic background noise level required for sensor to operate reliably. Must be proven-in-use prior to use for executive action Relatively unproven technology. Moving parts. Requires maintenance.

Point Detection (Acoustic )

Point Detection (Aspirated )

Gas is drawn from detection point to remote gas sensing element. Various sensing elements can be employed.

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APPENDIX 2 – COMBUSTION (FIRE & SMOKE) SENSING TECHNOLOGIES

Name

Method of Detection

Usage

Strengths

Weaknesses

Infrared (Multi-band) Flame Detector

Detects flickering infrared light from hydrocarbon fire. Multiple IR bands are monitored to reduce false triggers. Detects flickering infrared light from hydrocarbon fire.

Rapid hydrocarbon fire detection within a given area.

Reliable and proven technology. Fast response.

Unsuitable for high temp environments. Unsuitable for low hydrocarbon fires (Hence cannot detect Hydrogen or Methanol fires)

Rapid hydrocarbon fire detection within a given area.

Reliable and proven technology. Fast response.

UV Flame Detector

Detection of UV emissions from flame

Rapid hydrocarbon fire detection within a given area, suited to heated environments. Suitable for nonhydrocarbon fires (eg. Hydrogen, Methanol)

Suitability for hot environments. Can detect nonhydrocarbon fires.

Manual Call Point (Flame, Smoke & Heat)

Flame and Smoke Detection: Human detects fire/smoke and manually raises alarm Smoke detection by scattering of light by smoke particles

Plant-wide fire and smoke detection in manned areas– very versatile

Highly discriminating sensor – ultra reliable. Smoke, heat and flame sensitive.

Unsuitable for high temp environments. Unsuitable for low hydrocarbon fires (Hence cannot detect Hydrogen or Methanol fires) Can be prone to false triggers from sunlight Multi-band version is preferred Affected by oil droplets, dust and smoke. False triggering due to light sources such as arc welding. False triggering due to radiation sources. Principal Approval Required Reliant upon staff being present to raise manual alarm.

Point or open-path detection of smoke from smouldering fires

Best suited to detection of smouldering fires. Can be used as Line-Of-Sight detector.

Infrared (single band) Flame Detector

Optical Scattering Smoke Detector

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Reduced sensitivity to fully formed fires Some sensitivity to fog Use indoors only

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Ionisation Smoke Detector

Smoke detection by ionisation of smoke particles

Point detection smoke from smouldering fires

Best suited to detection of fully formed fires.

Combined Heat/Smoke

Combined detection of a thermistor type heat detector and an optical type smoke, in a single sensor Smoke detection by proprietary means

Can detect combustion from a broad range of fuels and fire types.

Detection of combustion from a range of different combustion processes.

Single or multipoint aspirated system for very early detection of smouldering fires

Very early sensitivity, often before a human inspecting can identify the source of the alarm.

Various means including bimetallic, glass bulb and fusible plugs. Detects either rate rise of temperature, or absolute temperature, or a combination.

Point or line detection, for fire that builds up quickly or is very hot. Often employed in high temperature environments or as backup for other faster but less reliable detection techniques

Very reliable. Low spurious alarm rate. Suitable for high temperature environments.

Ultra-High Sensitivity Smoke Detectors

Heat Detectors

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Reduced sensitivity to smouldering fires Point detection only Shall be combined with heat detectors for detecting smouldering files. Use indoors only Not as flexible as separate smoke and heat sensors Principal Approval Required

High sensitivity can lead to false triggers and hard to find sources of smoke. High maintenance Susceptibility to dust. Use indoors only. Slow response rate

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APPENDIX 3 - TONAL CHARACTERISTICS OF ALARM SOUNDERS

Title

Location

Trigger

Type

Frequency

Site Siren

Site Wide Signalling

Fire and Flammable Gas

Bell or Motor Driven Siren

520 Hz pulsing

Individual Alarm Sounder Civil Facilities

Process Areas

Fire and Flammable Gas

Loudspeaker

Two tone warbling, 1 kHz & 2 kHz

Civil Building

Fire and Flammable Gas

Bell

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MarkSpace Ratio ON for 3..5 sec, OFF for 1..5 sec 1:1

Cycle Time

1:1

2 seconds

4..10 seconds

2 seconds

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APPENDIX 4 – FIRE ZONE SCHEDULE Hazard zones

Leakage scenarios

Scenarios

Flowlines (typical)

15 mm hole size leak flanges joints and instrument fittings.

Gas dispersion & Jet fire

Manifold

15 mm hole size leak flanges joints and instrument fittings.

Gas dispersion & Jet fire

15 mm hole size leak flanges joints and instrument fittings at the gas phase.

Gas dispersion & Jet fire

15 mm hole size leak flanges joints and instrument fittings at the liquid phase.

Jet fire

Slug catcher

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