Gs Saf 216a-Area Classification

TOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELF

EXPLORATION PRODUCTION

GENERAL SPECIFICATION

GS SAF 216

AREA CLASSIFICATION

0 10/00 No change to TOTALFINA SP-SEC-216 Rev. 7

Rev Date Notes

"This document is the property of TotalFinaElf. It must not be reproduced or transmitted to others without written authorisation"

GS SAF 216TOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELF AREA CLASSIFICATION Page 2 of 63

DGEP/SE Rev.0 Oct. 2000

TABLE OF CONTENTS

1. INTRODUCTION......................................................................................................................................................4

1.1...REFERENCE DOCUMENTS........................................................................................................... 41.2. .INTENT AND SCOPE OF AREA CLASSIFICATION ........................................................................................ 41.3...LIMITS OF APPLICABILITY.......................................................................................................... 5

1.3.1. Type Of Petroleum Installations And Fluids .................................................................................................. 51.3.2. Scenarii .......................................................................................................................................................... 51.3.3. Existing And New Installations ...................................................................................................................... 6

1.4...TERMINOLOGY & DEFINITIONS ..................................................................................................................... 6

2. KEY PARAMETERS OF AREA CLASSIFICATION.........................................................................................12

2.1...TYPES OF SOURCES AND GRADES OF RELEASE ...................................................................................... 122.2...ZONES ............................................................................................................................................................. 122.3...CHARACTERISTICS OF PETROLEUM FLUIDS ............................................................................................ 13

2.3.1. Classification Of Petroleum Fluids Based On Closed Cup Flash Points (Ip 15)......................................... 132.3.2. Fluid Categories........................................................................................................................................... 14

2.4...BUOYANCY OF RELEASE ............................................................................................................................... 142.5...TYPE OF LOCATION......................................................................................................................................... 15

2.5.1. Open Area .................................................................................................................................................... 152.5.2. Sheltered Area.............................................................................................................................................. 152.5.3. Enclosed Area .............................................................................................................................................. 152.5.4. Guidelines .................................................................................................................................................... 16

2.6...TYPE OF VENTILATION .................................................................................................................................. 172.6.1. Foreword...................................................................................................................................................... 172.6.2. Adequate Ventilation.................................................................................................................................... 172.6.3. Dilution Ventilation And Evacuation Of Gas Leaks..................................................................................... 182.6.4. Ventilation Checks........................................................................................................................................ 19

2.7...PRESSURISATION VENTILATION ................................................................................................................. 212.7.1. Overpressure Protection .............................................................................................................................. 212.7.2. Underpressure Protection ............................................................................................................................ 22

3. DETERMINATION OF THE HAZARD RADIUS...............................................................................................23

3.1...THE HAZARD RADIUS ..................................................................................................................................... 233.2...METHOD ............................................................................................................................................................. 233.3...PUMPS ............................................................................................................................................................. 243.4...DRAINS AND SAMPLE POINTS ...................................................................................................................... 243.5...COMPRESSORS.................................................................................................................................................. 263.6...COLLECTION OF PSV'S AND VENT EFFLUENTS........................................................................................ 263.7...PIPING, INSTRUMENT TUBING, FLANGES AND VALVES........................................................................ 273.8...PIG RECEIVERS AND LAUNCHERS............................................................................................................... 283.9...SUMPS, INTERCEPTORS AND SEPARATORS IN OILY WATER TREATMENT UNITS.......................... 28

4. CLASSIFICATION OF OPEN, SHELTERED AND ENCLOSED AREAS ......................................................31

4.1...OPEN AREAS...................................................................................................................................................... 314.2...SHELTERED AREAS.......................................................................................................................................... 334.3...ENCLOSED AREAS............................................................................................................................................ 36

4.3.1. Size Of Hazardous Area ............................................................................................................................... 364.3.2 Zone Classification For Enclosures ............................................................................................................. 38

5 CLASSIFICATION OF WELLHEADS AND EQUIPMENT USED IN WELL OPERATIONS.....................39

5.1...FOREWORD........................................................................................................................................................ 395.2...DRILLING ........................................................................................................................................................... 395.3...WIRELINE........................................................................................................................................................... 405.4...PRODUCTION..................................................................................................................................................... 405.5...SURFACE MUD SYSTEMS ............................................................................................................................... 44



5.5.1. Water Based Mud Systems ........................................................................................................................... 445.5.2. Oil Based Mud Systems ................................................................................................................................ 45

5.6...GAS VENT........................................................................................................................................................... 45

6. INTERNAL COMBUSTION ENGINES AND HEATERS ..................................................................................46

6.1...GAS TURBINE.................................................................................................................................................... 466.1.1. Foreword...................................................................................................................................................... 466.1.2. Pre-Purging.................................................................................................................................................. 466.1.3. Ventilation And Classification Of The Turbine Enclosure ........................................................................... 476.1.4 Protection By Pressurisation........................................................................................................................ 476.1.5. Ventilation And Classification Of The Turbine Room.................................................................................. 486.1.6. Hot Surfaces In Areas Not Provided With Dilution Ventilation (e.g. exhaust pipes) ................................... 48

6.2...GAS AND LIQUID FUEL ENGINES ................................................................................................................. 506.2.1. General Requirements.................................................................................................................................. 506.2.2. Gas Engines ................................................................................................................................................. 506.2.3. Diesel Engines.............................................................................................................................................. 50

6.3...HEATERS ............................................................................................................................................................ 52

7. ACCUMULATOR BATTERIES............................................................................................................................53

7.1... INSTALLATION OF ACCUMULATOR BATTERIES IN BUILDINGS.......................................................... 537.1.1. Basics ........................................................................................................................................................... 537.1.2. Location And Hydrogen Detection............................................................................................................... 53

7.2...DILUTION VENTILATION CRITERIA ............................................................................................................ 547.2.1. Open Batteries.............................................................................................................................................. 547.2.2. Certified Recombination Batteries ............................................................................................................... 54

8. HYDROCARBON STORAGE ...............................................................................................................................55

8.1...UNDER-GROUND OR WITHIN-EMBANKMENT STORAGE TANKS : ....................................................... 558.2...OVERHEAD, FIXED ROOF STORAGE TANKS :............................................................................................ 558.3...OVERHEAD, FLOATING ROOF STORAGE TANKS :.................................................................................... 568.4...LPG STORAGE STORED UNDER PRESSURE :.............................................................................................. 568.5...REFRIGERATED LPG STORAGE :................................................................................................................... 578.6...LNG STORAGE................................................................................................................................................... 57

9. MISCELLANEOUS.................................................................................................................................................58

9.1...LABORATORIES ................................................................................................................................................ 589.2...ANALYSER SHELTERS..................................................................................................................................... 599.3...SMALL STORAGE OF FLAMMABLE PRODUCTS ........................................................................................ 599.4...LOADING AN FILLING OPERATIONS (ROAD TANKER, RAIL CAR, DRUM FILLING) ......................... 609.5... JETTIES (LOADING, DISCHARGE) ................................................................................................................. 609.6...AIR INTAKES ..................................................................................................................................................... 609.7...AIR EXHAUSTS.................................................................................................................................................. 609.8...CHIMNEYS AND EXHAUSTS .......................................................................................................................... 609.9...FLARES ............................................................................................................................................................. 609.10.TRAFFIC ............................................................................................................................................................. 61

9.10.1 Roads And Railways (ONSHORE) ............................................................................................................... 619.10.2 Helidecks, Helipads And Air Strips .............................................................................................................. 619.10.3. Boats............................................................................................................................................................. 61

9.11.PURGING ............................................................................................................................................................ 619.12.CLASSIFICATION OF ENCLOSED BUILDINGS ............................................................................................ 63



1. INTRODUCTION

1.1. Reference documents

For the classification of hazardous areas in COMPANY petroleum installations the orderof precedence is as follows:1. Relevant national regulations if they are more stringent than GS SAF 216.2. Project Safety Concept and S.O.R. (Statement Of Requirement) approved by

COMPANY.3. COMPANY general safety specification GS SAF 216.4. IEC (International Electrotechnical Commission) standards.5. IP-15: Area Classification Code for Petroleum Installations, Part 15 of the Institute of

Petroleum Model Code of Safe practice (London, March 1990).6. Other relevant international standards.

This specification can be used as a stand-alone document. It complies with IEC 79-10“Classification of hazardous areas”. Since IEC 79-10 does not provide detailedrecommendations regarding the extent of the hazardous areas in specific industries andapplications and allows reference to other codes, GS SAF 216 is mainly based on IP-15.The general philosophy of IP-15 and a lot of its detailed recommendations are adopted. Thisspecification and IP-15 differ mainly in areas not adequately covered by the code or wherethe code requires interpretation.

In some cases reference is made to standards other than IP-15, including API RP 500,although the latter shall not be used as a general reference.

The COMPANY general safety specifications that are referred to in this document are:

GS SAF 221 : Safety rules for buildings.GS SAF 222 : Safety rules for equipment handling hydrocarbon in enclosed areas.GS SAF 228 : Liquid drainage.GS SAF 253 : Impacted area, restricted area and fire zones.GS SAF 261 : Pressure protection & relief, emergency shut-down and depressurisation.GS SAF 262 : Safety rules for hydrocarbon disposal system.

1.2. Intent and scope of Area Classification

Installations in which flammable materials are handled or stored shall be designed so thatthe probability of coincidence of a flammable atmosphere and a source of ignition is sosmall as to be acceptable. To meet this objective a method, called Area Classification, isused to classify the locations where a flammable atmosphere may occur.For example, in situations where a flammable gas atmosphere has a high likelihood ofoccurring and that likelihood cannot be reduced, reliance will be placed on using equipmentwhich has a low likelihood of creating a source of ignition.

A hazardous area is defined as a three dimensional space where a flammable atmospheremay be expected to be present at such frequencies as to require special precautions for thetype and use of electrical apparatus or other potential ignition sources.

Hazardous areas will be identified and classified into Zones 0, 1, 2 based on the frequencyof the occurrence and duration of a flammable atmosphere. The outcome of the areaclassification exercise is a partition of a petroleum installation into Zones 0, 1 and 2 which



are marked on plot plans, and the rest of the installation classified as non-hazardous or“safe”.

This document is concerned with the classification of the areas located around facilitieshandling or storing flammable petroleum fluids. In practice, all hydrocarbons handled at atemperature above their flash point, or whose flash-point is below 21°C, are liable togenerate hazardous areas (the classification of the hydrocarbons commonly encountered inCOMPANY installations is detailed in § 2.3 of this document).

1.3. Limits of applicability

1.3.1. Type of petroleum installations and fluids

GS SAF 216 covers all E&P operations: drilling, production, treatment, storageand bulk distribution.

The scope of GS SAF 216 is limited to the petroleum flammable fluids or fluidswith similar physical characteristics. In particular it does not apply to toxic gases,which on manned installations may lead to more stringent rules, to combustibledusts and to ignitable fibres.

GS SAF 216 is applicable to all petroleum products: LNG (Liquefied Natural Gas)and LPG (Liquefied Petroleum Gases) can be treated as Category A fluids in thepoint source method (refer to chapters 2 & 3).For the classification of installations producing and/or storing LNG however,NFPA 59A shall be applied until a European standard (EN) covering the samescope is available (e.g. pr 50145 under preparation at time of issue of thisspecification).

The marine facilities covered by the IMO (International Maritime Organisation)codes (e.g. tankers) are excluded from the scope of this specification. The case oftankers at berth that generate a hazardous area on the jetty is covered in § 9.5 ofthis document.

The application of this specification to a FSO (Floating, Storage and Offloading)and to the oil storage related facilities on a FPSO (Floating, Production, Storageand Offloading) is not mandatory if IMO codes apply. The battery limits betweenthe process areas where GS SAF 216 applies and marine areas where IMO codesapply shall be defined on a case by case basis with the nominated classificationagent and COMPANY.

1.3.2. Scenarii

The classification of hazardous areas takes into consideration events which are"liable to occur during normal or abnormal plant operating conditions” (IP-15).



Are not considered for Area Classification:

1. Large gas/vapour releases from process vents or flares. Such releases shallrequire appropriate dispersion calculations (refer to § 3.6 of this specification).

2. Failure scenarios that are not predictable, such as the rupture of a processvessel or pipe (IEC 79-10). For these scenarios reliance is placed on theemergency shutdown system (ESD) and safety distances resulting fromconsequence analysis calculations (refer to GS SAF 253) to protect theinstallation.

1.3.3. Existing and new installations

New installations constructed by COMPANY and the modifications to existinginstallations operated by COMPANY affiliates, onshore and offshore, shallcomply with GS SAF 216.

GS SAF 216 is not retroactive: its application to the facilities put in operationbefore the issue of the specification is not mandatory.It is recommended however that the status of the equipment in these installationsbe checked. Where the design is of a standard lower than this specification andthis introduces a significantly risk, modifications should be implemented toupgrade the design to a standard as close as possible to GS SAF 216, orprecautions should be taken (e.g. procedures) to mitigate the risk.

1.4. Terminology & definitions

There are three types of statements in this specification, the “shall”, “should” and “may”statements. They are to be understood as follows:

Shall :Is to be understood as mandatory. Deviating from a “shall” statement requires derogationapproved by the COMPANY Corporate Safety and Environment Division.

Should :Is to be understood as strongly recommended to comply with the requirements of thespecification. Alternatives shall provide a similar level of protection and this shall bedocumented.

May :Is used where alternatives are equally acceptable.

For the purpose of this specification, the following definitions shall apply (the terms definedin this section are often in bold characters in the text of the specification):

AreaFor the purpose of this specification, an area is a three-dimensional region or space (as perIEC 79-10).



Adequate ventilationThis is ventilation, natural, artificial or a combination of both, sufficient to avoidpersistence of flammable atmospheres within sheltered or enclosed areas but insufficientto avoid their initial formation and spread throughout the area. This will normally beachieved by a uniform ventilation rate of a minimum of twelve air changes per hour with nostagnant areas (IP-15).

Air-lockTwo self-closing vapour-tight doors with a space in between (the “gap”) kept above thepressure prevailing in the adjacent hazardous area. The minimum pressure differencebetween the gap and the hazardous area must be 50 Pa (0.5 mbar). A local alarm buzzer plusan alarm sounding and lighting in the main control room are to be provided to warn theoperators and personnel if both doors are open simultaneously. Loss of differential pressurein the gap between the 2 doors shall also alarm in the main control room.

Area classificationArea classification is the notional division of a facility into hazardous areas and non-hazardous areas, and the sub-division of hazardous areas into zones (refer to chapter 2,§2.2). Definition from IP-15.

Dilution ventilationThis is artificial ventilation sufficient to maintain generally as non-hazardous an enclosedarea containing a source of release or an aperture into a hazardous area (IP-15).

Emergency Shut-Down (ESD)Control actions undertaken to shut down equipment or process in response to a hazardoussituation (ISO).

Enclosed areaAny building, room or enclosed space within which, in the absence or failure of artificialventilation, the ventilation does not meet the requirements for adequate ventilation (IP-15).

ESD systemSystem of manual stations and automatic devices that, when activated, initiate a shutdownof the installation.

Fire & Gas system (F&G)The Safety System which monitors the temperature or the energy flux (fire), theconcentration of flammable or toxic gases (gas), and initiates relevant actions (alarm, ESD,emergency depressurisation, active fire-fighting, electrical isolation etc.) at pre-determinedlevels (COMPANY).

Flammable atmosphereMixture of flammable gas or vapour with air in such a proportion that, without any furtheradmixture, it will burn when ignited. In the context of area classification the term“flammable” is synonymous with “explosive” (IP-15).

Flammable limits (upper, lower)The limits of combustibility of flammable gases or vapours when mixed with air (IP-15).



Flash-pointLowest temperature to which a liquid must be heated to give off sufficient vapour to form aflammable mixture with air. Ignition does not occur at the flash point unless there is asource of ignition (IP-15).

Fuel sourceSame as ISO definition of "source of release" (API).

Hazard radiusThe hazard radius of a source of release is the largest horizontal extent of the hazardousarea that is generated by the source when situated in an open area under unrestrictednatural ventilation (IP-15).

Hazardous area and zoneA hazardous area or zone is defined as a three dimensional space in which a flammableatmosphere is or may be expected to be present in such frequencies as to require specialprecautions for the construction and use of electrical apparatus or other potential ignitionsources (IP-15). All other areas are referred to as non-hazardous areas in this context. In ahazardous area three types of zone (0,1,2) are recognised (IP-15).

HVACAbbreviation for Heating, Ventilating and Air Conditioning.

Ignition sourceSource of temperature and energy sufficient to initiate combustion (API).

Ignition temperature (synonymous with ‘auto-‘ and ‘self-ignition temperatures’)The temperature at which a substance will begin to burn without application of any sourceof ignition (IP-15). The test conditions shall be as per IEC 79-4 and BS 4056.

Open areaAn are in an open air situation where vapours are readily dispersed by wind. Typically airvelocities should rarely be less than 0.5 m/s and should frequently be above 2 m/s (IP-15).

OverpressureArtificial ventilation of an enclosed area to maintain the area at a controlled pressureabove the ambient pressure (IP-15). Overpressure obtained by artificial ventilation isreferred to as simply overpressure in this specification.

Self-closing doorsDoors that are designed to close by themselves and to remain closed if not intentionallyopened or kept opened.

Sheltered areaAn area within an open area where ventilation may be less than in a true open area but isadequate ventilation (IP-15).

Source of releasePoint from which flammable gas, liquid or a combination of both can be released into theatmosphere (ISO).

Underpressure



Artificial ventilation of an enclosed area to maintain the area at a controlled pressurebelow the ambient pressure (IP-15). Underpressure obtained by artificial ventilation isreferred to as simply underpressure in this specification.

Ventilation (natural, artificial)Ventilation is a general term to indicate air movement and replacement by fresh air. Naturalventilation refers to ventilation caused by wind or convection effects. Artificial ventilationrefers to ventilation caused by air purges or mechanical means such as fans (IP-15).

1.5. Area classification procedure

Area Classification should be carried-out by persons who have a good knowledge of theproperties of the flammable materials used in the installation, of the processes and of theenvironment of the installation to be classified.

For new projects it is recommended that Area Classification is conducted by a senior safetyengineer assisted by a process engineer. For the modifications of an existing installation theteam should include a member of the operating crew. It should be noted that although theresults of Area Classification have direct implications on the selection of the electricalapparatus, knowledge in electrical matters is not a must for conducting or participating to anArea Classification exercise.

The area classification shall be done in three steps:1. Identify the sources of release. Determine and record their basic characteristics for area

classification. All the sources of release in the installation shall be analysed. Theircharacteristics shall be recorded in a data base which shall contain all the informationrequested in Table 1.

2. Study how to reduce the risk through design improvements. Consider reducing thenumber and grades of the releases and optimise the equipment lay-out wherever possibleto decrease the risk of ignition (e.g. pertinent grouping of equipment, optimisation ofventilation, consideration of buoyancy).

3. Prepare/modify the hazardous area drawings, draw the envelopes of the zones.

A flow diagram showing the basic steps for determining the hazardous area around a sourceof release is shown in Figure 1.

This procedure shall be followed at each stage of a development Project and whenever thereis a modification to an existing installation.

The classification of hazardous areas depends on the ventilation of the areas whereflammable vapours are likely to be present and to accumulate. This specification definesonly the functional requirements for ventilation or pressurisation systems to effectivelydilute flammable gases or prevent the ingress of flammable gases in areas not suitable forthe presence of a flammable atmosphere. It is not a specification for the design andoperation of ventilation and pressurisation systems. It does not cover in particular HVACrequirements for human comfort, temperature control and the extraction of smokeduring/after a fire (refer to GS SAF 221 for ventilation in buildings).



Figure 1 – How to determine a hazardous area

ZONE NUMBER FOR ENCLOSURES - § 4, tables 4.3 and 4.4

HAZARDOUS AREA ENVELOPE- § 4, tables 4.1 and 4.2

POINT TYPE SOURCE HAZARD RADIUS - § 3.3 to § 3.8 COMMON TYPE EQUIPMENT - § 3.9, § 5 ,6 ,7 ,8 & 9

VENTILATION - § 2.6

LOCATION - open, sheltered, enclosed area - § 2.5

BUOYANCY OF RELEASE - § 2.4

FLUID CATEGORY - § 2.3.2

GRADE OF RELEASE - § 2.1

EQUIPMENT

RULES FOR DETERMINATION GS SAF 216TOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELFTOTAL FINA ELF AND CLASSIFICATION Page 11 of 63

DGEP/SE OF HAZARDOUS AREAS Draft October 1999

Hazardousequipment

Flammable fluid Area Source of release Classification Remark

Tagnb.

Description Nature

MW T°C

Pbara

Flash°C

Buoyancy Category Type Ventilation

Nature Grade Flowm3/h

Zone Hazard radiusm

V 110 Separator Gas 22(1)

50(2)

75(2)

-(3)

heavierand lighter

G Shelter Adequate Instrumentvent

2 -(4)

2 7.5

Note 1 Range of MW to cover all situations.Note 2 Design pressure and design temperature or the most critical combination of P and T for hazardous releases.Note 3 For liquids only.Note 4 Only for vents that are covered by this specification (see section 3.6)

Table - 1 - Hazardous equipment table



2. KEY PARAMETERS OF AREA CLASSIFICATION

2.1. Types of sources and grades of release

For the purpose of area classification a source of release is defined as a point or surfacefrom which a flammable gas, vapour or liquid may be released into the atmosphere. Threegrades of release are defined in terms of their likely frequency and duration.

Continuous grade release = continuous sourceA release which is continuous or expected to occur for long periods : the cumulativeduration of release exceeds 1000 hours per year.Example : Gaseous atmosphere in a hydrocarbon storage tank.

Primary grade release = 1st degree sourceA releases which can be expected to occur periodically or occasionally during normaloperation : the cumulative duration of release is in the range of 10 to 1000 hours per year.Example : Sampling connection (for regular, open to atmosphere sampling).

Secondary grade release = 2nd degree sourceA releases which is not expected to occur in normal operation and, if it does, is likely to doso only infrequently and for short periods : the cumulative duration of release is less than10 hours per year.Examples : Flanges, pump seal.

Releases not considered for Area Classification :Refer to section 1.3.2.

Note: “Normal operation” means operation within the plant design parameters, includingstart-ups, shutdowns, routine maintenance and any degraded modes of operations foreseenduring design.

2.2. Zones

The classification in zones or “zoning” is the partition of the installation into volumes inwhich a flammable atmosphere may be present (refer to the definition of a hazardous area).The following definitions are from IP-15:

Zone 0 :That part of a hazardous area in which a flammable atmosphere is continuously present, orpresent for long periods.

Zone 1 :That part of a hazardous area in which a flammable atmosphere is likely to occur in normaloperation.

Zone 2 :That part of a hazardous area in which a flammable atmosphere is not likely to occur innormal operation, and, if it occurs, will exist only for a short period.

For further guidelines refer to IP-15 (§ 1.5.3).



"Type of sources" and "zones" are not synonymous. The type of a zone depends on thelevel of ventilation in the considered area. In “open areas” only they agree (for thedefinition of open area refer to § 2.6) i.e.:• Zone 0 is generated by a continuous grade release,• Zone 1 is generated by a primary grade release,• Zone 2 is generated by a secondary grade release.

Throughout this specification, the zones are represented as follows:

2.3. Characteristics of petroleum fluids

For Area Classification in petroleum installations, the classification of petroleum fluidsshall be done in two steps, first in classes then in categories:

1. The Class of liquid hydrocarbons relates to their flash point and handling temperatureat actual storage or process conditions.

2. The Category is derived from the class and indicates to which extent a fluid onrelease can form a flammable mixture with air. This is a determining factor in thecalculation of the hazard radius (chapter 3).

2.3.1. Classification of petroleum fluids based on closed cup flash points (IP 15)

Class 0: liquefied petroleum gases.

Class I: liquid hydrocarbon with a flash point below 21°C.

Class II: liquid hydrocarbon with a flash point equal or above 21°C but below55°C.II(1): handled below flash pointII(2): handled at or above flash point.

Class III: liquid hydrocarbon with a flash point equal or above 55°C but below100°CIII(1): handled below flash point,III(2): handled at or above flash point.

Unclassified are liquid hydrocarbons with a flash point above 100°C. Howeverthey should be considered as class III(2) when handled at, or above, their flashpoint temperature.

For further guidance on this classification refer to Appendix A of IP-15.

Class 0, I, II(2) and III(2) liquids shall be categorised as per section 2.3.2.

Zone 0 Zone 1 Zone 2



2.3.2. Fluid categories

Cat DefinitionG Flammable gas or vapour.A Any flammable liquid that, on release, will vaporise rapidly or

substantially. Includes LPG and lighter flammable liquids e.g. LNG.Also includes any flammable liquid at a temperature sufficient toproduce, on release, more than 40% vaporisation with no heat inputother than from the surroundings.

B Any flammable liquid, not in Category A, but at a temperature sufficientfor boiling to occur on release.

C Any flammable liquid, not in Category A or B, but which can be at atemperature above its flash point or form a flammable mist, on release.

Following are guidelines for application to the oil and gas productioninstallations :• Unstabilised crude oil should be put in Category B because of the wide

boiling temperature range involved.• Stabilised crude oil should be put in Category C. Crude oil may be regarded

as stabilised when separation from gas has been at a pressure at or below1.1 bara.

• When handled below their boiling temperature, Class I, Class II(2) and ClassIII(2) liquid hydrocarbons should be put in Category C.

• When handled at or above their boiling temperature, Class I, Class II(2) andClass III(2) liquid hydrocarbons should be put in Category B.

• Class II(1) and Class III(1) hydrocarbon liquids may be categorised as "non-hazardous" when they do not form a flammable mist or spray on release.

For further guidance to categorise the petroleum fluids refer to IP-15,Appendix B.

2.4. Buoyancy of release

The general rule is:

• gas with MW < 21 shall be considered as lighter than air,• gas with MW > 31 shall be considered as heavier than air,• gas whose MW is between 21 and 31 shall be considered lighter and heavier than air

(see bottom note).

It should be noted that this rule differs from IP-15. MW is the molar mass of the gas.



Where a buoyancy categorised “lighter and heavier than air” leads to excessively largehazardous areas or impracticable design, the buoyancy can be further assessed using one ofthe two following methods :

Method n°1 :• gas can be considered as heavier than air if MW > 29 and T release < T ambient,• gas can be considered as lighter than air if MW < 29 and T release > T ambient.Method n°2 :• gas can be considered as heavier than air if it is demonstrated that relative density > 1 at

release conditions and T release > T ambient,• gas can be considered as lighter than air if it is demonstrated that relative density < 1 at

release conditions and T release < T ambient.The relative density is the density relative to the density of air at the same pressure andtemperature.When variations of the effluent MW during the life of field can be anticipated (e.g. fromreservoir depletion), they should be considered during initial design phases.

Note : An example of vapours that are categorised “lighter and heavier than air” is a LNGrelease. It generates a vapour heavier than air because of its very low temperature, but it isbound to become lighter than air after warming up. For vapours and gases having thisbuoyancy, the hazardous area resulting from the classification exercise is the envelope ofthe hazardous areas determined for a “heavier” and a “lighter” than air vapour or gas.

2.5. Type of location

2.5.1. Open area

An area in an open air situation where vapours are readily dispersed by wind.Typically air velocities should rarely be less than 0.5 m/s and should frequentlybe above 2 m/s (IP-15).

2.5.2. Sheltered area

An area within an open area where ventilation may be less than in a true openarea but is adequate ventilation (IP-15).Note : the API RP 500 word is "partially enclosed area" and the IP-15 word is"sheltered or obstructed open area".

2.5.3. Enclosed area

Any building, room or enclosed space within which, in the absence or failure ofartificial ventilation, the ventilation does not meet the requirements foradequate ventilation (IP-15).All pits and depressions are enclosed areas.



2.5.4. Guidelines

The table in this section provides guidelines to determine whether a location iscategorised as “Sheltered” or “Enclosed” for the purpose of Area Classification,based on their geometrical characteristics i.e. with natural ventilation only.Guidance from this table is broadly in line with the guidance offered inAPI RP 500 (§6.3.2.4.7, second edition, November 1997).There was no attempt to segregate between “sheltered” and “open” in this tableas both types of location are adequately ventilated. Some types of locationsindicated as “sheltered” in the table may be eligible for the “open” category.

Walls (% surface) (2)

0 to 25 25 to 50 50 to 75 75 to 100

Floor + ceiling sheltered enclosed(3) enclosed enclosed

No floor (1) +ceiling

sheltered sheltered enclosed enclosed

Floor, no ceiling sheltered sheltered sheltered enclosed

No floor (1), noceiling

sheltered sheltered sheltered sheltered

Note 1 : Gratings are regarded as no floor.Note 2 : Plain walls (no louvers).Note 3 : May be regarded as “sheltered” i.e. natural ventilation may be found

adequate in some cases.

The buildings described below are regarded as sheltered areas and may be usedas weather protection for equipment handling flammable fluids.• Buildings where no walls extend below 2.5 m above ground, and the space

under the roof is adequately ventilated (e.g. there are openings in the roof forthis purpose, examples are given in Figure 4.3 and 4.4 of chapter 4).

• Buildings where the walls are provided with louvers or other types of slitspurposely designed for ensuring that natural ventilation will be adequate. Asa minimum the louvers should be present on three (out of the four) sides ofthe building: two strips of louvers, each with a minimum vertical width of1 m, shall run along the full length of the wall, one at the top i.e. close to theroof/ceiling, the other at the bottom i.e. close to the floor/ground. It shouldalso be checked that these buildings offer a sufficient free area of inletopenings as per the formula given in §6.3.2.4.6 of API RP 500.



2.6. Type of ventilation

2.6.1. Foreword

This specification addresses only the issues of dilution and dispersion offlammable gases in hazardous areas. This specification does not deal withdangers associated with the toxicity of gases and vapours which may be dealtwith by similar techniques. It does not deal with requirements not related toexplosion safety.

For all artificial ventilation systems, the ventilation air shall be taken from a non-hazardous area and shall not, by virtue of any chemical products or impuritieswhich it may contain, produce deleterious effects or introduce a risk of reducedsafety.

2.6.2. Adequate ventilation

This is ventilation, natural, artificial or a combination of both, sufficient toavoid persistence of flammable atmospheres within sheltered or enclosedareas but insufficient to avoid their initial formation and spread throughout thearea. This will normally be achieved by a uniform ventilation rate of a minimumof twelve air changes per hour with no stagnant areas (IP-15).

Application:1. Open areas : natural ventilation is adequate in open areas.2. Sheltered areas : they shall be regarded as adequately ventilated.3. Enclosed areas : adequate ventilation as a minimum provided by an artificial

ventilation system shall be implemented when they contain sources ofsecondary grade releases (and/or if they have a direct opening to an externalZone 2 area). Such enclosed areas will be classified Zone 2 in presence ofadequate ventilation. Enclosed areas shall not contain a source of primarygrade of release and shall not be open to a Zone 1 area.

Loss of artificial ventilation:This paragraph applies to enclosed areas provided with artificial ventilation andclassified Zone 2 in presence of adequate ventilation.Audible and visual alarms shall be provided in case of loss of the artificialventilation. If the area is not provided with fixed gas detection the electricalequipment and the other sources of ignition not suitable for use in Zone 1 shallbe immediately and automatically suppressed.If the area is provided with fixed gas detectors, gas detection shall immediatelyand automatically suppress these sources of ignition. Suppression of theseignition sources on loss of ventilation may be delayed to allow the loss to beinvestigated.Note : if an enclosure contains sources of primary grade of release the equipmentnot suitable for use in Zone 0 shall be shut down immediately and automaticallyon loss of ventilation, even if gas detection is installed in the enclosure (Note thata primary grade of release is not acceptable in enclosed areas and shall require aderogation to this specification approved by COMPANY).



2.6.3. Dilution ventilation and evacuation of gas leaks

This is artificial ventilation sufficient to maintain generally as non-hazardous anenclosed area containing a source of release or an aperture into a hazardous area(IP-15). Dilution ventilation must be sufficient to immediately bring theflammable gas concentration under 20% of the Lower Flammability Limit(LFL) and keep it so all the time.

Typical ventilation rates covering all scenarios for dilution ventilation cannot beproposed. A calculation shall be carried-out to estimate hydrocarbon leaks. Itshall be based on the largest secondary grade release. Should simultaneousrelease from more than one secondary grade releases be likely, then thecumulated release shall be considered.Note 1 : Any primary grade of release if present shall be added (Note that aprimary grade of release is not acceptable in enclosed areas and shall require aformal derogation to this specification approved by COMPANY).Note 2 : As pipe rupture or other low probability accidental leak scenario are notconsidered for dilution ventilation, all electrical apparatus installed in anenclosure protected by dilution ventilation shall be suitable for Zone 2.

Applications:Dilution ventilation provided by an artificial ventilation system shall beimplemented in enclosed areas containing sources of secondary grade of release(and/or if they have an aperture to an external Zone 2 area) and ignition sourcesnot suitable in a hazardous area (e.g. hot surface). Enclosed areas shall notcontain a source of primary grade of release and shall not have a direct openinginto a Zone 1 area.1. Case of gas turbine hoods : refer to chapter 6.2. Case of laboratories and analyser shelters : refer to chapter 9.3. Case of battery rooms : refer to chapter 7.

Note that methods to calculate minimum introduction rates to achieve adequateventilation are proposed in API RP 500 (Appendices B & C, 1997).

Loss of ventilation :Audible and visual alarms shall be provided in case of loss of the artificialventilation ensuring dilution. If the area is not provided with fixed gas detectionthe electrical equipment and the other sources of ignition not suitable for use inZone 1 shall be immediately and automatically suppressed.If the area is provided with fixed gas detectors (mandatory inside gas turbineenclosures), gas detection shall immediately and automatically suppress thesesources of ignition. Suppression of these ignition sources on loss of ventilationmay be delayed to allow the loss to be investigated.The bottom note of § 2.6.2 applies.

Note on toxicity: the possibility for the presence of toxic gases in an enclosedarea where personnel may be present shall be systematically checked. Dilutionventilation shall be installed so as to prevent the formation of a toxic atmosphere.The design shall be based on an estimation of (i) the leaks which may occur innormal operation and of (ii) the abnormal leakage caused by a foreseeable failureof the components which will create the most dangerous situation. The dilution



ventilation shall keep the concentration of the toxic component(s) in the airbelow the Threshold Limit Value(s) (TLV) for continuous exposure (TWA orTime Weighted Average). Presence of personnel in such enclosed areas shall besubjected to strict control measures including personal toxic gas detectors, fixedtoxic gas detection and the provision safe escape facilities (e.g. breathingapparatus) in the building. Toxic gas detectors shall be set no higher than theTLV-TWA.

2.6.4. Ventilation checks

The degree of ventilation required in a location should be investigated using themethod of Figure 2.1. from IP-15. This method applies in areas where sources offlammable gases are present. Where toxic gases may be released, the ventilationrates given in the figure are not relevant.



Figure 2.1 - Ventilation check



2.7. Pressurisation ventilation

This section is concerned with the protection of a room or building containing electricalequipment or other potential sources of ignition and located where flammable gases orvapours may be present. The ingress of these gases or vapours into the room is preventedby maintaining inside it a protective gas at a higher pressure than that of the outsideatmosphere.

A room or building is an enclosure of sufficient size to permit the entry of a person. Thissection is not concerned with the electrical apparatus for which protection bypressurisation in hazardous areas follows the electrical codes (The protection of theelectrical apparatus in hazardous areas shall comply with COMPANY specification SP-ELC-120).

The protection by pressurisation of COMPANY rooms and buildings containing electricalequipment shall adhere to IEC 79-13 and GS SAF 216 (some of the requirements of thissection exceed the requirements of IEC 79-13). This specification addresses onlyfunctional requirements.

The types of pressurisation and associated construction requirements for buildings areaddressed in IEC 79-13.

Enclosed areas shall contain no source of primary/continuous grade of release and shallnot have a direct opening into a Zone 1 area. They may contain only sources of secondarygrade of release and/or have a direct opening into a Zone 2 area.

The protective gas shall not, by virtue of any chemical products or impurities which it maycontain, produce deleterious effects or introduce a risk of reduced safety.

For the purpose of this specification over and underpressure are defined as thedifferential pressure (respectively above or under that of the surroundings) that isnecessary to prevent ingress of flammable gases or vapours. This does not relate in thiscontext to the design or maximum allowable pressure in the equipment.

2.7.1. Overpressure protection

Overpressure protection (overpressurisation) is achieved when artificialventilation or static pressurisation controls the pressure inside an enclosed areasufficiently above that of the surrounding (hazardous) area to prevent ingress of aflammable atmosphere from an outside fuel source.

Overpressurisation shall be fitted to totally enclosed areas:1. Containing ignition sources, but no source of release, and having a direct

opening to an external hazardous area (e.g. electrical room, workshop).2. Containing sources of secondary grade of release and sources of ignition, and

having a direct opening to an external hazardous area, in conjunction withdilution ventilation (e.g. turbine hood in process area).

The difference in pressure to be maintained shall be greater than 50 Pa (0.5mbar).



Loss of pressurisation :Overpressure shall be monitored, or detected by a pressure switch as a minimum.Pressurised enclosed areas shall be provided with fixed gas detection toimmediately and automatically suppress all ignition sources not suitable forZone 1. Loss of overpressure shall initiate an alarm.Note : if gas detection is not provided or if a source of primary grade of release isinstalled in the building (either shall require a derogation to this specificationapproved by COMPANY), loss of overpressure shall automatically andimmediately suppress all ignition sources not suitable for Zone 1.

2.7.2. Underpressure protection

Underpressure protection (underpressurisation) is achieved when artificialventilation keeps the pressure inside an enclosed area sufficiently below that ofthe surrounding area to prevent possible egress of a flammable atmosphere to anoutside less or non hazardous area.

Underpressure protection shall be fitted to an enclosed area containing sources ofsecondary grade of release and ignition sources, and having a direct opening toan external non-hazardous area, in conjunction with dilution ventilation (e.g.turbine hood in non hazardous area).

The difference in pressure to be maintained shall be greater than 50 Pa (0.5mbar).

Loss of pressurisation :Underpressure shall be monitored, or detected by a pressure switch as aminimum. Loss of under-pressure shall initiate an immediate alarm, and suppressall ignition sources located in the vicinity of the enclosed area and not suitablefor Zone 1. Suppression of these ignition sources on loss of underpressure maybe delayed to allow the loss to be investigated.



3. DETERMINATION OF THE HAZARD RADIUS

This section provides the requirements for the classification and extent of the hazardous areasusing the individual point source method from IP-15.It is a generic method that should be used in cases not covered by the direct examples given inchapters 5, 6, 7, 8, and 9 of this specification.

3.1. The hazard radius

The hazard radius of a source of release is the largest horizontal extent of the hazardousarea that is generated by the source when situated in an open area under unrestrictednatural ventilation.

The hazard radius is not the result of a fully deterministic approach. It should be regardedas a standard to be used when no better method is available. It is not a substitute for goodengineering judgement. For example one may consider that a particular item of equipmentgives rise to a critical risk and decide to enlarge the associated hazardous area.

The hazard radius does not take into consideration all the actual physical properties of thegas, characteristics of the environment and conditions of release. Gas dispersioncalculations, if necessary, shall be carried out as per GS SAF 253, using codes (computerprograms) approved by COMPANY.

3.2. Method

The classification of hazardous areas (zone number and extent) shall be conducted in twosteps1. First the hazard radius around each potential release source. It is determined in this

chapter. It depends on the characteristics of the source of release, the fluid category,and the dimension of the release (e.g. flowrate, diameter of release point).

2. Then this hazard radius is used to set up the three dimensional envelope of thehazardous area taking account of the type of area, the ventilation in the area, the naturalor artificial obstacles in the gas path, and the buoyancy of the release (see chapter 4).

To draw the line between hazardous and non-hazardous areas, apply the following:• Secondary grade releases : it shall be considered that the source of release can be

anywhere at the periphery of the equipment skid. A detailed study of each singlesecondary grade release is not required. It is only in case of difficulty that the exactlocation of the sources of release should be considered. This would require input fromthe equipment vendor.

• For non skid mounted equipment e.g. vessels, it shall be assumed that sources of releaseare located at a distance of 0.8 m from the equipment external limits (e.g. vesselshell).

• The accurate location of each primary or continuous grade releases shall be consideredfor drawing the hazardous areas they generate.

• Two adjacent hazardous areas shall be joined in any point where their distance does notexceed 3 m.



Generally a whole offshore deck or a whole onshore unit containing essentiallyhydrocarbon processing or storage equipment should be classified as Zone 2. GS SAF 216shall then be used for:� Defining the Zones 0 and 1 inside such unit.� Defining the Zone 2 contour around the items of equipment located at the deck/unit

surface limits.

All distances in this chapter are given in metre.

3.3. Pumps

LNG pumps, for which motor and pump are submerged in a “can” or in a storage tank, donot generate a hazardous area.

Sources of release on pumps include their seals, vents, drains, valves, piping flanges andfilter/strainers. They are normally all secondary grade sources because flanges are broken,filters opened and vents and drains operated infrequently. Likewise a seal failure resultingin an appreciable release of liquid is unlikely. Should any of these events be part of“normal operation” (as defined in § 2.1) or occur frequently then the item should beregarded as an individual primary grade source.

Hazard radius (m)

Fluid category Standard pump High integritypump

A

B

C

30

15

7.5

7.5

3

3

Table 3.1 - Pumps

In this table the term "high integrity" refers to a pump for which the design reducessignificantly the probability of release. The pumps of glandless type, or fitted with adouble mechanical seal system with a means of detecting leaks through the inner sealshould be regarded as “high integrity pumps”.

The hazardous area generated by the pump should be drawn from the periphery of thepump. For this purpose the term "pump" should include the associated equipment whichcan be source of release.

Vents and drains which are not blanked off in normal operation generate their ownhazardous areas, independently from the pump they are associated with.

3.4. Drains and sample points

This section applies to process equipment drains, instrument drains and liquid samplepoints that discharge directly to atmosphere.



Drains and sample points should be graded based on the expected frequency of use. If usedmore than once a day they should be regarded as primary grade sources as a minimum.

The following rules shall apply:

1. Draining and sampling of Category A liquids shall not be done directly to atmosphere.They shall require a closed collection system, designed to be safely vented to anappropriate disposal system such as a flare (refer to GS SAF 262 for the design ofhydrocarbon disposal systems, and GS SAF 228 for the design of closed drainsystems).

2. Draining and sampling of Category B liquids directly to atmosphere should beavoided. Wherever feasible, draining should be done to a closed drain system. Samplesshould be taken in a sealed container designed to be connected to the drain point for theduration of the sampling. And there shall be a hazardous area of 3 m radius aroundsuch sample points as for flanges and valves (§ 3.7).

3. Equipment drains (with the exception of the instrument drains) shall be designed as perGS SAF 228. As such they are normally blanked off and used only after the equipmentis isolated and depressurised. They generate a hazardous area as for valves and flanges(§ 3.7). If for any reasons equipment drains were not blanked off they would follow theTable 3.2 and in this case the possibility for draining category B liquids shall beconsidered.

4. Sampling of gases to an open system, i.e. with a release to atmosphere, shall generate ahazard radius equivalent to a vent (§ 3.6 applies). Sampling to a closed system withnormally no release to atmosphere shall generate a hazard radius of 3 m as for flangesand valves (§ 3.7).

In all other cases, in particular the instrument drains and sampling of liquids to an opensystem, the hazard radius shall be determined in Table 3.2. The hazardous area will extendfrom the point of draining/sampling.

Hazard radius (m)

Fluidcategory

Diameter *

3 mm

Diameter *

6 mm

Diameter *

12 mm

Diameter *

25 mm

A

B

C

**

3

0.3

**

7.5

1.5

**

15 ***

1.5

**

30 ***

3

* This is the diameter of the smallest item on drain or sample line i.e. line, valveor restriction orifice.

** Draining and sampling of Category A liquids directly to atmosphere shall notbe allowed.

*** For hazard radii of 15 or 30 m, alternative design options should be considered:a closed collection system (refer to the text of this section), or a smallerdiameter (e.g. a restriction).

Table 3.2 – drains (not blinded) and liquid sample points



3.5. Compressors

Sources of release on compressors include seals, glands and joints. The hazardous areashould be drawn from the periphery of the unit.

Gas buoyancy Hazard radius (m)

Heavier than air

Lighter than air

15 *

5

* The radius may be reduced to 7.5 m for pressures below 20 bara and shaftdiameters of 50 mm or less.For diaphragm compressors the hazard radius may be reduced to 3 mprovided there are no vents or drains to atmosphere at the compressor.

Table 3.3 - Compressors

Vents and drains which are not blanked off in normal operation generate their ownhazardous areas, independently from the compressor they are associated with.

3.6. Collection of PSV's and vent effluents

Process vents

As far as practicable, permanent or occasional outflows of combustible vapour shall becollected and discharged away from possible sources of ignition.If the collecting piping is all welded i.e. is without flanged fittings and valves, the spacearound the piping shall be regarded as a safe area.

All vent flowrates in this section are given at ambient conditions.

Table 3.4 applies to vents with a peak flowrate not exceeding 200 m3/h and a gas exitvelocity below 150 m/s. These recommended distances are based on unrestricted upwarddischarge and dispersion of vapour without condensation.

For vents with flowrates exceeding 200 m3/h a dispersion calculation shall be carried outto check if the distances of this table are adequate (gas dispersion calculations shall becarried-out as per GS SAF 253). A dispersion calculation is also recommended for ventswith flowrates exceeding 100 m3/h. Material that could condense shall not be venteddirectly to atmosphere. The hydrocarbon disposal systems recommended by COMPANY(e.g. cold vent, flare…) are described in GS SAF 262.

For vents with flowrates kept below 100 m3/h and where the velocity of all the releases areabove 150 m/s, the distance to LFL given in API RP 521 should be adopted.

Vents should be classified as continuous, primary or secondary grades of releasedepending on the frequency of operation. Vents used frequently (e.g. daily) should beclassified as primary grade as a minimum. For some vents there may be a small flow froma continuous or primary grade with a larger occasional flow, for example during abnormalor emergency operation. When the expected frequency of the smaller release generates a



Zone 0 or 1, and an occasional larger release is graded as secondary, then the Zone 0 or 1hazardous area shall be surrounded by a larger Zone 2 area defined by the larger flow.

Gaseous sample points should be designed so that the flowrate is less than 10 m3/h atambient conditions.

Vent rate at ambient conditions (m3/h) Hazard radius (m)

Less than 10

10-100

100-200

3

7.5

15

Note : This table applies only to velocities up to 150 m/s. It applies to heavier-than-airgases and vapours with unrestricted discharge upwards. For lighter-than-air gasesdischarged upwards a 5 m hazard radius may be used or alternatively the radiusmay be obtained by calculation.

Table 3.4 - Process vents

Instrument vents

The hazard radius from vents on instrument systems should be based on Table 3.5. Thisincludes vents from vessel level glasses. Instrument vents may generally be regarded assecondary sources of release.

Hazard radius (m)

Fluid category Diameter * 6 mm Diameter * 12mm

Diameter * 25mm

A

B

C

G lighter than air

G heavier than air

7.5

3

0.3

3

3

15

7.5

1.5

5

7.5

30

15

3

7.5

15

* This is the diameter of the smallest item on the vent line, i.e. line, valve or restriction orifice. 25 mmshall not be considered unless specifically requested in the COMPANY approved Project SafetyConcept.

Table 3.5 - Instrument vents

3.7. Piping, instrument tubing, flanges and valves

All-welded (without fittings such as valves, instruments and flanges) piping and instrumenttubing designed and constructed to COMPANY specifications should not be considered assources of release.



Flanges and valves are normally sources of secondary grade releases. Flanges routinelybroken in normal operation e.g. with a frequency greater than once a week, should beconsidered as primary grades of releases.

Blow out of part of a gasket has not been considered since it is regarded as an incidentwith a low probability that is considered in consequence analysis for the determination offire zones (refer to GS SAF 253).

Hazard radii listed below are from the periphery of flanges and valves in piping andinstrument tubing.

Fluid Category Hazard radius

A 3

B 3

C 1.5

G heavier or lighter than air 3

Table 3.6 - Flanges and valves

3.8. Pig receivers and launchers

The design of the pig traps shall be such that they cannot be opened while under pressure ;this is normally achieved by a mechanical interlock between the door mechanism and thevent. A pressure gauge shall be provided with a range suitable for checking zero pressurebefore opening the door.

On this basis, the doors of the pig traps should be regarded as sources with a hazard radiusof 7.5 m. Vents and drains should discharge to a safe location and the hazard radius theygenerate shall be estimated using section 3.6 of this chapter.

Pig receivers and launchers are likely to be opened frequently and should normally beregarded as sources of primary grade release.

3.9. Sumps, interceptors and separators in oily water treatment units

For the purposes of this specification a sump means a vessel, open or vented toatmosphere, used to collect petroleum liquids, usually as a result of deliberate draining.Other liquids, e.g. water, can enter the sump but the petroleum liquid is normally anappreciable part of the total liquid entering.In contrast, interceptors and separators in oily water treatment are vessels open or ventedto atmosphere, used to separate petroleum liquids from other non-flammable liquids,typically water, and in which the petroleum liquids are present in smaller quantity.Typically they are found on the main oily water effluent treatment system of a facility.



SumpsSumps are intended to contain petroleum liquids and normally should be considered ascontinuous or primary grade sources depending on the frequency with which oil isexpected to enter (see § 2.1 of this specification).The sump may be regarded as a secondary grade source when oil can enter only duringmaintenance operations which are expected to be infrequent, e.g. major maintenance atintervals of about 2 years or longer. The possibility of more frequent unplannedmaintenance should always be considered.

The typical layout of a sump is shown in Figure 3.1 and the space within the walls of anopen sump or to ground level, whichever is higher, should be regarded as an enclosed area.For a primary grade source it should be classified as Zone 0 and for a secondary gradesource as Zone 1.

The hazardous area above ground and outside the sump walls should be drawn as shownfrom the periphery of the sump using the appropriate distances obtained from Table 3.7 incases when it can be assumed that entry of only category C fluids can occur. Generallythis assumption can be made only in the case of storage and tankage areas, includinginstallations and depots. This area should be classified as Zone 1 or Zone 2 depending onwhether the source is primary or secondary grade.

When there is a possibility that hot material could enter the sump in sufficient quantity toproduce appreciable quantities of gas, or that Category A or B material couldinadvertently enter, then a horizontal distance D2 of 15 m should be used with thecorresponding vertical distances of Table 3.7.

Interceptors and separatorsInterceptors and separators should normally be regarded as primary grade sources.They may be regarded as secondary grade sources when oil can enter only as a result ofequipment failure, e.g. failure of a cooler tube in a cooling water system or a majorspillage and they can not be polluted accidentally more than once a year.

The space within the walls of an interceptor or separator or to ground level, whichever ishigher, should be regarded as an enclosed area. For a primary grade source it should beclassified as Zone 0 and for a secondary grade source as Zone 1. The hazardous area aboveground and outside the separator walls should be drawn from the periphery of theseparator, as shown in Figure 3.2.

These relatively large areas and the Zone 2 around a Zone 1 area are recommendedbecause larger quantities of more volatile material than normal can often inadvertentlyenter an interceptor or separator. The appropriate distances obtained from Table 3.7should be used in cases when it can be assumed that entry of only category C fluids canoccur. In storage facilities including installations and depots containing only category Cfluids the larger Zone 2 area outside the Zone 1 may be omitted.

For vented sealed sumps, interceptors and separators, the hazardous area should be drawnfrom the vent.

Open sumps and vessels with covers removable in normal operation e.g. removableconcrete slabs should not be regarded as sealed vessels but as open sumps.



L D1 D2 H1 H2Less than 5

5 to less than 10

10 or greater

3

7.5

15

3

7.5

7.5

3

3

7.5

3 + h

3 + h

7.5

Notes : 1.This table should be used only for Category C liquids. 2.L is the width of the sump. The hazardous area should extent from the edge of the

pool.

Table 3.7 - Sumps, interceptor and separators (all distances in metres)

Notes : 1.For a secondary grade source the areas shown as Zones 0 and 1 would be Zones 1 and 2. 2.Dimensions from Table 3.7.

Figure 3.1 - Open sump - zoning shown for primary grade source

Figure 3.2 - Separator or interceptor - primary grade source

Zone 0 Zone 1

LiquidD1

D2

H2

H1

h

Ground

Ground

Liquid

7.5

m (H

) 1

15 m (D )17.5 m(D )2

3 m

Zone 0 Zone 1 Zone 2

h



4. CLASSIFICATION OF OPEN, SHELTERED AND ENCLOSED AREAS

The size of the hazardous zones is determined in this chapter based on the hazard radius fromchapter 3, the buoyancy of the release and the degree of ventilation at the location of the fuelsource.

The size of the hazardous zones does not depend on the grade of release. The grade of release ishowever a key factor for the classification in Zone 0, 1 or 2.

4.1. Open areas

Notes : 1.Hazardous areas shown should be classified as Zone 1 or 2 depending on the grade ofrelease.

2.S is the distance from source to edge of solid platform.

Figure 4.1 - Hazardous area from point source - open area - release heavier-than-air

Source

Ground

Source above groundPitZone 1

D1

D2

H1

h

H2

GroundSource above elevated platform

Solid platform

SourceH2

H1

D2

h

D1 D1

D - S1 D - S1

S3

H 1

Ground/deck

0.3H1min

D1

D2

h

Source

Vapour tightroof/deck

H1m

inH

2

0.3H1min

D1

D2

H1min



Hazard radius(m)

D1 (m) D2 (m) H1 (m) H2 (m)

30

15

7.5

3

1.5

0.3

30

15

7.5

3

1.5

0.3

15

7.5

7.5

3

1.5

0.3

7.5

7.5

3

3

1.5

0.3

3

7.5

H1 + h

H1 + h

H1 + h

H1 + h

Notes : 1.h is the height of the source above ground level or solid platform floor. 2.D1 for open area by definition is equal to the hazard radius. 3.The hazard radius is determined from the Tables in chapter 3.

Table 4.1 - Hazardous area envelope dimensions - open area - release heavier-than-air

Note : The hazardous area is Zone 1 or 2 depending on grade of release.

Figure 4.2 - Hazardous area from point source - open area - release lighter-than-air

H2

H1

Source

Ground or solid deck

D1

Open area (release lighter than air)

D1

H1

Source

Solid deck

Source

H1

D1

D - S1

S

H2

D - S1

H2

h <

Ground/deck

0.3H1min

SourceVapour tight

roof/deck

H1m

inH

2

0.3H1min

D1 D1

h

H1min



Hazard radius(m)

D1 (m) H1 (m) H2 (m)

5

3

1.5

5

3

1.5

7.5

5

1.5

3

3

1.5

Note : The hazard radius is determined from Tables in chapter 3.

Table 4.2 - Hazardous area envelope dimensions - open area - release lighter-than-air

4.2. Sheltered areas

There are many cases of natural ventilated situations where there is some restriction to freeair circulation : some associated with an otherwise open area layout but where there is anobstruction in the form of a wall, adjacent structure or open-sided roof, which will intrudeinto what otherwise would be within the open area hazard zone ; others where a partialrestriction to natural air flow is in-built by design in the form of a structure that has piercedopenings or louvers to provide weather protection.

The term sheltered area applies to any such part of an otherwise open area where naturalventilation is less than in a true open area but is adequate to avoid persistence of aflammable atmosphere (refer to chapter 2, section 2.5 and 2.6).

The determination of the extent of the hazardous area will therefore depend on the type ofsheltered area, as shown below.

Notes : 1.The area shown around the roof should be classified as hazardous, with the same zoneclassification as the hazardous area from a source (outside or below the area) whichimpinges upon it.

2.Where two areas do not directly impinge, it is prudent to fill the gap between these twoareas.

3.Where the underlying hazard zone is Zone 1, then the intermediate space, up to andincluding the roof area, may be classified Zone 2 for heavier than air gases or vapours.

4.H1 is obtained from Table 4.1 for heavier-than-air gases or vapours and from Table 4.2 forlighter-than-air gases.

Figure 4.3 - Extent of hazardous area around unventilated roof (producing a shelteredarea above the open-sided area) : applicable to lighter or heavier-than-air gas orvapour)

Ground

0.3 H1

0.3

H 1

0.3 H1

0.3

H 1

Vapour-tight roof

Open area unwalleddown to groundlevel-classifiedas in Fig. 4.1 and 4.2



Notes : Same as Figure 4.3

Figure 4.4 - Extent of hazardous area around ventilated roof (producing a shelteredarea above the open-sided area : applicable to lighter or heavier than air gas orvapour)

Notes : 1.The open area hazard radius is determined from chapter 3. From this the dimensions D1, D2, H1and H2 are obtained from Table 4.1.

2.The above diagram illustrates the case where the release is great enough for the open area hazardradius to substantially fill or extend beyond the confines of the aperture walls.

3.The area is classified Zone 1 or 2 throughout its entire area according to the grade of release of thesource. All pits within the zone should be Zone 1.

4.With a source of smaller hazard radius e.g. a sample point, the ventilation locally can sometimesbe high enough to prevent the source from influencing the classification of the whole enclosure.There would still be a local Zone 1 or 2 around the source and the extent of this zone should begreater than for an open area, typically about twice the hazard radius of an open area.

Figure 4.5 - Extent of hazardous area around sheltered area with perforated wallscontaining source (gas or vapour heavier-than-air) and meeting the criterion of adequateventilation

Ground

Open area unwalleddown to groundlevel-classifiedas in Fig. 4.1 and 4.2

0.3 H10.

3 H 1

0.3 H1

roof

Source

Ground

d > D1 D > d1

D2

Vapour-tight roof

0.3 H min1h

H2

0.3 H minupwardfrom top ofuppermostaperture

1

Extendingvertically downto ground level

H

min

10.3 H min1

0.3 H min1



Notes : 1.The open area hazard radius is taken from chapter 3. The dimensions H1, D1 and H2 are thenobtained from the table of Table 4.2.

2.With a source of smaller hazard radius, e.g. a sample point, the ventilation locally can sometimesbe high enough to prevent the source influencing the classification of the whole enclosure. Therewould still be a local Zone 1 or 2 around the source, and the extent of this zone should be greaterthan in the open air, typically about twice.

Figure 4.6 - Extent of hazardous area around sheltered area with perforated wallscontaining source (gas or vapour lighter-than-air) and meeting the criterion of adequateventilation

Notes : 1.D1 is obtained from Table 4.1 or Table 4.2. 2.The wall should extend to at least the full vertical height of the hazardous area if it is to be used as

a deflection wall.

Figure 4.7 - Extent of hazardous area around wall producing sheltered area (gas or vapourlighter or heavier than air)

Source

GroundD1

Vapour-tight roof

0.3 H minfrom top ofuppermostaperture

1

H2

H

min

1

0.3 H min1

0.3 H min1

0.3

H

min

1

Source

D1S

RadiusD - S1

Plan view



4.3 Enclosed areas

4.3.1. Size of hazardous area

An enclosed area is any building, room or enclosed space within which, in theabsence or breakdown of artificial ventilation, the ventilation will not beregarded as “adequate” (refer to sections 2.5 and 2.6 of chapter 2).

For the purpose of Area Classification any enclosed area shall be assumed to bein contact with (i.e. have an aperture in) an outside area, unless the enclosedwalls, ceilings, floors and any ducting are vapour-tight by construction. Avapour-tight door or hatch, locked in normal operation and opened only under apermit to work procedure, and air-locks should not be considered as apertures.One ordinary door or one door of a vapour-tight design (self-closing or not) shallbe considered as an aperture.Air-locks and self-closing doors are defined in § 1.4.

When a source of release is located within an enclosed area then the whole spacewithin the enclosure should be classified, depending upon the grade of releaseand the degree of ventilation. The outside areas in contact with the enclosed areashould be classified as shown in the figures of this section. Only sources ofsecondary grades of release may be located within an enclosed area: sources ofprimary grade of release in enclosed areas shall require a derogation to thisspecification approved by COMPANY.

When there are no sources within the enclosed area but the enclosure is incontact with (has an opening into) an external hazardous area, then the enclosureshould be classified based on the zone number of the external area and the degreeof internal ventilation that is provided.



Notes : 1.The vertical dimension H1 of the external zone area is considered as if the largest source inthe enclosed area was located at the top of the aperture, height h. The values of D1, D2,H1 and H2 should be taken from Table 4.1 using the open air hazard radius.

2.The zone classification for both the internal and surrounding external areas should bedetermined based on the ventilation and grade of release.

3.All pits and depressions within a hazardous area with gas heavier-than-air shall beclassified as Zone 1.

Figure 4.8 - Extent of hazardous area around the aperture of an enclosed areacontaining a source of release (gas or vapour heavier-than-air)

Notes : 1.The dimensions H1, D1 and H2 are taken from the Table 4.2 using the open air hazardradius for the largest source of release.

2.For releases lighter-than-air, H1 and H2 are taken from the top and bottom of the aperturerespectively.

3.The zone should be determined from Table 4.3.

Figure 4.9 - Extent of hazardous area around the aperture of an enclosed areacontaining a source of release (gas lighter-than-air)



4.3.2 Zone classification for enclosures

Grade of Type of artificial ventilation

internal release Inadequate (2) Adequate(3) Dilution ifattainable (4)

Overpressure

Continuous

Primary

Secondary

Zone 0 (1)

Zone 0 (1)

Zone 1

Zone 0 (1)

Zone 1 (1)

Zone 2

Non-hazardous

Non-hazardous

Non-hazardous

Not applicable where there is aninternal primary or continuousgrade of release, but may beapplicable in conjunction withadequate ventilation for anenclosed area containing onlysecondary grade releases, classedas Zone 2, surrounded by a Zone 0or 1 area.

Notes : 1.Continuous or primary grade sources shall not be located within an enclosed area. Such design shall requireformal derogation to GS SAF 216

2.With inadequate ventilation, for a source within an enclosed area, the external zone classification will be : forcontinuous release – Zone 0, for a primary release – Zone 1, for a secondary release – Zone 2. The extent of theseexternal zones will be as shown in Figures 4.8 and 4.9.

3.With adequate ventilation, for a source within an enclosed area the external zone classification will be the sameas that of the enclosed area itself.

4. An area within a larger enclosure subject to local artificial ventilation, i.e. by extractor fan, should be classifiedaccording to the local ventilation rate in that local area, i.e. either dilution or adequate depending on which ismet.

5.With a source of small hazard radius, e.g. a sample point, the local ventilation may be high enough to preventthe source from influencing the classification of the whole enclosure. There should still be a local Zone 1 or 2around the source and the extent of this zone should be greater than in the open air, typically about twice theextent.

Table 4.3 - Enclosed area with an internal source of release - effect of ventilation on zone classificationof the hazardous area

Grade of Type of artificial ventilationexternal zone Inadequate Adequate Dilution Overpressure (1)

Zone 0

Zone 1

Zone 2

Zone 0(1)

Zone 0(1)

Zone 1

Zone 0(1)

Zone 1(1)

Zone 2

Not applicable

Not applicable

Not applicable

Non-hazardous if source isoutside the enclosed area. Formeasures to be taken in theevent of loss of overpressurerefer to section 2.7.1.

Notes : 1.Location of an enclosed area without overpressure protection in a Zone 0 or 1 is not acceptable, this shallrequire formal derogation to GS SAF 216.

Table 4.4 - Enclosed area with no internal source of release but in connected to an outside hazard zone -effect of ventilation on zone classification of the hazardous area



5 CLASSIFICATION OF WELLHEADS AND EQUIPMENT USED IN WELLOPERATIONS

5.1. Foreword

This chapter sets out COMPANY requirements for the Area Classification of production,wireline, workover and drilling operations, onshore and offshore. It does not cover theproduction operation equipment located downstream of the wellheads.

5.2. Drilling

Classification of areas for drilling and workover operations is shown on Figures 5.1 and5.2, based on the potential sources of hydrocarbon release on the surface at the bell-nippleand around the flowline outlet.

In an open area the hazardous area should extend 7.5 m vertically and horizontally fromthe bell-nipple and down to ground or sea level. When a solid deck or platform is morethan 9 m above the sea then the hazardous area may stop 9 m below this deck or platform.

Hazardous areas from miscellaneous sources such as vents, drains, valves and flanges onthe BOP, its stack and the riser assembly will normally be within the hazardous area shownon Figure 5.1. If not, they shall be determined as per the relevant sections of chapter 3.Vents and pressure drains should as far as practicable not be released directly toatmosphere, i.e. they should be collected in a purposely designed system discharging at asafe location (away from ignition sources, refer to chapter 3).

The occurrence of a blow-out is not considered in Area Classification. "Kicks" are notconsidered as well. Kicks are regarded as accidental, rare events on COMPANY drillingand work-over sites: the installation of equipment for degassing the mud and continuouslymonitoring the pit level, the level of hydrocarbon gases and gas extraction is mandatory onthese sites.

On drilling installations, the "dog house" and all other technical facilities should beclassified as Zone 2. Generally, sheltered areas (§ 2.5) should generate a hazardous areaextending 3 m outside the shelter (beyond the 7.5 m from the bell-nipple if necessary). Anyapertures from an enclosed area containing a source of release should be regarded as asecondary grade source (§ 2.1) and the resulting hazardous area should be drawn fromthe apertures (see chapter 4).

If the derrick is enclosed (§ 2.5), and if it contains a secondary grade source of release(e.g. flanges, valves in hydrocarbon pipes) the internal space should be classified as Zone1, with a Zone 2 extending 3 m outside the enclosure. Primary grade sources of releasesuch as vent line outlets shall not be allowed within an enclosed derrick or the shieldedportion of a derrick.

If the sub-structure is enclosed and if it contains a secondary grade source of release(e.g. flanges, valves in hydrocarbon pipes), the internal space should be classified as Zone1 with a Zone 2 extending 3 m outside the enclosure or 7.5 m from the bell-nipplewhichever is greater. Primary grade sources of release such as vent line outlets shall notbe allowed within an enclosed area.



The hazardous area generated from the mud system is not in the scope of this section andshould be determined as per § 5.5.

All electrical equipment on the drilling mast shall be suitable for Zone 2 as a minimum(sufficient if the derrick is adequately ventilated).

All electrical equipment needed for controlling drilling operations in an emergency (i.e.kick, blow out) shall be suitable for Zone 1.

For a non eruptive onshore well the zone numbers may be reduced, as shown inFigure 5.2.

5.3. Wireline

Area Classification for wireline operations is shown on Figures 5.3 and 5.4, based on thepotential sources of hydrocarbon release on surface and at the stuffing box.

For a non eruptive onshore well the zone numbers may be reduced, as shown inFigure 5.4.

5.4. Production

Area Classification for production operations are shown on Figures 5.5 and 5.6. For anonshore well the ground cellar is classified as Zone 1 for all servicing and productionoperations. In the case of a beam pumping well, the stuffing box of the pump shall beconsidered as a secondary source of release generating a Zone 2 with the extent shown inFigures 5.5 and 5.6.



Figure 5.1 - Offshore wellhead in drilling and workover phase

Figure 5.2 - Onshore wellhead in drilling and workover phaseFor a non eruptive well Zone 1 becomes Zone 2 and Zone 2 becomes a safe area

7.5

m

DRILLING AND WORKOVER

Sea level

9 m

or t

o se

a le

vel

Main deck

Cellar deckWellhead W

HP riser

Rig floor

Top of wind break

Bell-nipple (rig floor level)Flowline

7.5 m

Zone 2

Zone 1

BOP

BOP

7.5 m

Ground

Zone 2

Zone 1

Wellhead

W

7.5 m

Bell-nipple (rig floor level)Flowline

7.5

m



Figure 5.3 - Offshore wellhead in wireline phase - source point is at stuffing box

Figure 5.4 - Onshore wellhead in wireline phase for an eruptive well.For a non eruptive well Zone 1 becomes Zone 2 and Zone 2 becomes a safe area

WIRELINE

Sea level

Xmas tree

7.5

m

9 m

or t

o se

a le

vel

Main deck

Cellar deck W

BOP

7.5 m 7.5 m

xx

Zone 2

Zone 1Stuffing box

Wellhead

7.5

m7.5 m

Ground

7.5

m

Xmas tree

BOP

15 m

7.5 m

W

xx

Zone 2

Zone 1

Wellhead

Stuffing box



Figure 5.5 - Offshore wellhead - production or injection (open area)

Note : In the case of a beam-pumped well, the release source to be considered is the stuffing box

Figure 5.6 - Onshore wellhead production or injection (open area)



5.5. Surface mud systems

The surface mud system includes the mud circulating pumps, the shale shaker area and thesettling tank, together with any mud degassing equipment.

5.5.1. Water based mud systems

Pumps on the surface mud system should normally not be regarded as sources ofrelease.

Hazardous areas around mud tanks and shale shakers located in open areas areshown on Figures 5.7 and 5.8.

Enclosures containing a mud tank should, unless there is adequate (artificial)ventilation, be classified as Zone 1, with an additional Zone 2 area extending 3 mfrom any openings in the enclosure.

When a shale shaker is located in an enclosure without adequate (artificial)ventilation, the enclosure should be classified as Zone 1, with an additionalZone 2 area extending 7.5 m from any openings.

The extent of the hazardous area from sources of release on the mud degassersystem should be based on the requirements of Chapter 3.

Figure 5.7 - Hazardous area around mud tank (open area)

Figure 5.8 - Hazardous area around shale shaker (open area)

3 m3

m

7.5 m

3 m

Groundor deck

Liquid level

7.5

m

1.5

m

Ground or deck

1.5 m7.5 m



5.5.2. Oil based mud systems

The possibility of the mud being itself hazardous (e.g. an oil-based mud) shall beconsidered. A mud shall be considered hazardous whenever its temperature mayreach its flash point or the auto-ignition temperature during:• storage, or• circulation (as a result of high subsurface temperature and/or mixing with

reservoir hydrocarbons), or• upon release (e.g. heated by sun radiation, other hot objects, or when spray

atomisation leading to mist formation can occur).

Advice from geologist should be obtained to estimate the maximum operatingtemperature of the mud.

When the drilling mud itself is considered to be hazardous the extent of thehazardous areas around the mud system equipment should be estimated based onChapter 3. Open tanks should be regarded as sumps. The larger of the distancesindicated in Chapter 3 and those defined in this chapter should be used to definethe hazard zones.

Mud pumps and associated pipe work, valves and fittings should be consideredas sources of release when the mud is hazardous, and the extent of the hazardousareas should be based upon Chapter 3.

5.6. Gas vent

The gas vent outlet of the main mud system should be located at the top of the derrick(outside the enclosure if the derrick is enclosed) or be remote from the drilling area.

When the maximum anticipated vent rate can be estimated, then the extent of thehazardous area should be based on the recommendations on process vents given inChapter 3 (§3.6). When this information is not available, the hazardous area shouldextend at least 15 m in all directions from the vent.

With a vent at the derrick top, any area within the derrick less than 15 m from the ventshould be considered hazardous.

The gas vent should normally be considered a source of secondary grade release (seechapter 2).



6. INTERNAL COMBUSTION ENGINES AND HEATERS

6.1. Gas turbine

6.1.1. Foreword

§ 6.1 sets out the COMPANY requirements for the design and installation of gasturbines normally fuelled by hydrocarbon gas, with regard to the risk ofignition/explosion.

Gas turbines shall be installed in a totally enclosed area. One important functionof the enclosure/room as defined below is to reduce the noise level around theunit (“acoustic enclosure”), the other is to make this area safe by dilutionventilation.

The turbine enclosure designates the enclosure housing the gas turbine and itsauxiliaries (e.g. liquid-fuel and/or fuel gas supply, the lower part of the exhaust,ventilation and cooling). It is assumed that dual-fuel turbines do not raiseadditional, specific hazards. Note that a small turbine enclosure may also becalled a “turbine hood”.

The turbine room contains the turbine and its enclosure, the driven equipmentand all the auxiliaries. The main justification of a turbine room is to provide asafe environment to the driven machinery (e.g. alternator) if it has to be installedin a hazardous area (e.g. offshore). In cases where the driven equipment does notrequire a safe environment (or is installed in a safe area of the plant), the turbineroom is not mandatory. The hazardous area classification of the turbine roomshall be determined as per § 4.3 of this specification.

The requirement for over/underpressure protection of a gas turbine enclosuredepends on the classification of the area outside the enclosure (refer to § 6.1.4).

Gas turbines shall not be installed in Zone 0 or Zone 1. As a result gas turbinesshall drive equipment that is either a source of secondary grade of release(hydrocarbon gas compressor, oil pump), or that is not a source of release(alternator, water pump).

6.1.2. Pre-purging

In cases where there is electrical equipment under the enclosure not suitable forZone 1, the enclosure shall be purged with at least 5 air changes before startingthe turbine or energising any other electrical equipment not suitable for Zone 1.The purging system shall be suitable for Zone 1.Note that purging is of course not required if the enclosure is kept pressurisedwith hydrocarbon free air at all times.



6.1.3. Ventilation and classification of the turbine enclosure

Fuel supply (gas, liquid) and combustion chambers are in the enclosure, where alot of heat is generated by the operation of the turbine. The enclosure containsboth ignition sources (hot surfaces, and electrical equipment not suitable forZone 1) and sources of release during the operation of the turbine. Therefore theenclosure shall be provided with a ventilation system for cooling purposes and todilute flammable gases. 90 air changes an hour is a minimum to achievedilution ventilation.

The ventilation necessary to run the turbine is called the “normal” ventilation. A“standby” ventilation shall also be provided. The standby ventilation shallautomatically start on loss of normal ventilation.

Normal and standby ventilation should normally be identical. This means thatthey achieve cooling and dilution ventilation, are suitable for Zone 1 and aresupplied from an auxiliary power source (i.e. independent from normal powerand which takes over in case of shutdown of the normal power). After the turbineis shut down, the auxiliary power source shall be capable of keeping theventilation running until hot surfaces have been cooled below the auto-ignitiontemperature of the gas/air mixtures that may be present in the hood. If thisdesign cannot be wholly implemented the following lists the minimumrequirements for the safe operation of the turbine:1. The standby ventilation shall be suitable for Zone 1 and be supplied from an

auxiliary source of power as defined above.2. The standby ventilation shall provide dilution ventilation as a minimum.3. The normal ventilation shall be suitable for Zone 2.

The electrical equipment under the enclosure shall be certified for use in Zone 2as a minimum.

Fuel gas supply to the turbine shall be provided with a double block and bleedarrangement (bleed to safe location), actuated by the turbine protection system,to automatically isolate the combustion chambers on any turbine shut down. Inaddition to this double and bleed arrangement, a shutdown valve (not part of theturbine package) shall be provided to shut off the main fuel gas supply at thesource and be actuated by the main process plant Emergency Shutdown System.

The fuel gas equipment under the turbine enclosure should be minimised andlimited to: a pressure control valve (or regulator), a normally dry knock-out potbeing the ultimate protection in case of accidental liquid carry-over, the doubleblock and bleed arrangement, and the inter-connecting piping.

6.1.4 Protection by pressurisation

Differential pressure shall be provided as applicable :• underpressure where the turbine enclosure is surrounded by a safe area,• overpressure where the turbine enclosure is surrounded by a hazardous area.

If the turbine enclosure is located in a non-hazardous area the pressure within thehood shall be controlled to below the outside pressure with a minimum under-



pressure of 50 Pa (0.5 mbar). If the enclosure is located in a turbine room theunderpressure may be achieved from the combined effect of the underpressureinside the enclosure and the overpressure in the turbine room.

When the turbine enclosure is located in a hazardous area the pressure within thehood shall be controlled to above the outside pressure with a minimumoverpressure of 50 Pa (0.5 mbar).

In both cases (underpressure and overpressure) a pressure switch shall initiate analarm if the differential pressure drops below 50 Pa (0.5 mbar).

6.1.5. Ventilation and classification of the turbine room

If the driven equipment is not a source of release (e.g. alternator, water pump)and the turbine room is located in a hazardous area, the turbine room shall bemade safe by adequate ventilation and overpressure protection (seeFigure 6.2).An overpressure of at least 50 Pa (0.5 mbar) shall be maintained in the turbineroom with respect to all surrounding classified areas with apertures into the room(including the turbine enclosure itself which shall be maintained 50 Pa under theturbine room pressure). A pressure switch shall initiate an alarm if thedifferential pressure drops below 50 Pa (0.5 mbar).The fuel gas line shall be all-welded inside the room (no flanges and no valves).In particular, the fuel gas isolation valves shall be located outside the turbineroom.The fuel gas double block and bleed arrangement shall be installed so that thebulk of the fuel gas inventory inside the turbine hood is depressurised on anyturbine shutdown.

If the driven equipment is a source of release the turbine room shall be madeZone 2 by adequate ventilation. The fuel gas line to the turbine enclosure may inthis case have flanges inside the room. The turbine enclosure shall beoverpressurised.

6.1.6. Hot surfaces in areas not provided with dilution ventilation (e.g. exhaust pipes)

When located within the restricted area of the petroleum installation, they shallbe thermally insulated as far as practicable. Their surface temperature shall notexceed 80% of the ignition temperature of any flammable gas mixtures likely tobe present. By default the surface temperature shall not exceed 250°C (Note thatthe restricted area is defined in GS SAF 253).



Figure 6.1 - Turbine driven compressor in a hazardous area

Figure 6.2 - Typical gas turbine arrangement in a room

Ventilation

COMP.

d > 2 m

d > 2 m

Combustion air

Safe zone

Turbine

External hazardous area

To flare Fuel-gas

d : distance from exhaust and air intake location to any hazardous area.

Turbine hood.Over pressure = 0.5 mbar

d > 2 m

d > 2 munder-pressure

over-pressure

Turbine hood ventilationair intake

Combustion airintake

Turbine roomventilation air intake

Turbine

Turbine hood

Load(alternator

pump, etc.)

Turbine room - adequateventilation and over pressure

Dilutionventilation andunder pressure

To flareFuel gas

Turbine hoodventilation exhaust

Main and standby fans

Turbine exhaust

under-pressure

over-pressure



6.2. Gas and liquid fuel engines

6.2.1. General requirements

Spark ignited, gasoline-fuelled engines shall not be installed in hydrocarbon plants.

A diesel fuel engine and its fuel circuit are not regarded as a source of release, i.e.they do not generate a hazardous area. The quantity of hydrocarbon vapour involvedis small enough to be disregarded. A diesel fuel engine is a source of ignition,mainly due to its high skin temperature and the possibility of spark emission.

Gas engines, as gas turbines, are both sources of ignition and sources of release.

Diesel fuel and gas engines should be installed in a non-hazardous area. They shallnot be installed in Zone 0 or 1. They shall not be installed in a Zone 2 where a groupIIC gas (e.g. hydrogen, acetylene) may be present. They shall not be installed inareas where liquid hydrocarbon spillage may occur and result in the release ofvapours with an auto-ignition temperature lower than 135°C.

6.2.2. Gas engines

Gas engines should comply with the requirements of § 6.1 (pressurised enclosurewith dilution ventilation), as gas turbines. Adherence to § 6.1 is mandatory for a gasengine installed offshore.

Onshore, adherence to § 6.1 is not mandatory if a package comprising one engine,its driven equipment and their “auxiliaries” (see the note below) is installed:1. 30 m or more from the hydrocarbon process and storage facilities and their

technical rooms (see the note below), and2. 45 m or more from LPG units, and3. 45 m or more from the installation main control room, and4. 60 m or more from the living quarters, offices and workshops.Ignition sources should be made suitable for Zone 2 as far as practicable.Note: process facilities and technical rooms shared by several gas engines such asthe fuel gas treatment unit are not regarded as “auxiliary” and shall be installed atthe distance specified above. Several gas engine driven packages of the same typeand function may be grouped in the same unit (refer to Figure 6.3).

6.2.3. Diesel engines

A diesel fuel engine installed in Zone 2 should either be EEMUA certified forZone 2 or protected by internal overpressure in an enclosure. This is mandatoryoffshore.

Onshore this is not mandatory if the engine, its driven equipment and their“auxiliaries” (see the note below) are installed:1. 30 m or more from the hydrocarbon process and storage facilities and their

technical rooms (see the note below), and2. 45 m or more from LPG units, and3. 45 m or more from the installation main control room, and4. 60 m or more from the living quarters, offices and workshops.



Ignition sources should be made suitable for Zone 2 as far as practicable.Note: process facilities and technical rooms shared by several diesel engines such asthe fuel gas treatment unit are not regarded as “auxiliary” and shall be installed atthe distance specified above. Several diesel engine driven packages of the same typeand function may be grouped in the same unit (refer to Figure 6.3).

Figure 6.3 – Diesel and gas engines in a hazardous area onshore

Unit edge

ENGINE

ENGINE

ENGINE

Unit edge

Haza

rdous area boundary encroaching onto engines

d

d = defined in §6.2



6.3. Heaters

The extent and classification of hazardous areas around fired heaters and other fuelledutilities shall be based upon the following principles :1. any valve or set of flanges on the fuel gas network shall generate a Zone 2 with a

radius of 3 m,2. any valve, set of flanges on the liquid-fuel network shall generate a Zone 2 of a radius

of 1.5 m for Diesel oil or Category C liquids and 3 m for lighter liquids,3. main burners, igniters and pilots generate no hazardous area in normal operation.

However, any equipment within a radius of 1.5 m around the main burners, ignitersand pilots shall be suitable for use in zone 2,

4. the tubes/coils within the radiant or convection sections in a direct fired heatergenerate no hazardous area,

5. point leak sources on the heated fluid including valves, set of flanges, etc. shallgenerate hazardous areas according to the rules defined in chapter 3.



7. ACCUMULATOR BATTERIES

7.1. Installation of accumulator batteries in buildings

7.1.1. Basics

With the exception of small capacity sealed batteries which are outwith the scopeof this specification, accumulator batteries are regarded as primary sources ofrelease: they release hydrogen when they are charged.

At the time of issue of this specification, there is no international standard (IECor CEN) for the installation of accumulator batteries in enclosures/buildings.Chapter 7 sets out the basic safety requirements for the design of installationsdesigned by or on behalf of COMPANY. They are based on two Frenchstandards which, until an IEC or CEN standard covering this scope is approvedand issued, shall be adhered to:� NFC 15-100, part 5, chapter 55, § 554 and its “Annexe”� NFC 58-311.

Gases released by batteries in charge mode can be recombined. Two types ofaccumulator batteries shall be considered:� Batteries for which the recombination rate is less than 95%. They are called

open batteries.� Batteries for which the recombination rate is 95% or more. They are called

recombination batteries. To be regarded as recombination type, batteriesshall be certified as per NFC 58-311 requirements.

Dilution ventilation shall be provided in the enclosures containing accumulatorbatteries. The dilution ventilation rates shall be calculated as per § 7.2.

When dilution ventilation is achieved by artificial means, the battery chargeshould be stopped on loss of ventilation (in most cases this means that the batterychargers are switched off).

7.1.2. Location and hydrogen detection

Accumulator batteries and their charger may be located in the same cubicle onlyif this cubicle is provided with natural or artificial dilution ventilation as per therequirements of this chapter.

The requirements set out in § 7.1.1 shall apply to all batteries liable to releaseflammable gases. This section addresses additional requirements that depend onthe capacity and discharge voltage of the accumulator batteries.

If Capacity (Ah) x Discharge voltage (V) is less than 1000, hydrogen detectionis not mandatory in the room (building) where the accumulator batteries areinstalled.



If Capacity (Ah) x Discharge voltage (V) is more than 1000, batteries and theircubicles shall be installed in an electrical room.• For certified recombination batteries with certified chargers fitted with

downstream protections which shut down the charger supply on maximumcharging current, this may be a standard electrical room containing otherelectrical equipment and where there is no hydrogen detection.

• Open batteries shall be located in a dedicated battery room. The safety ofpersonnel handling the acidic fluids associated with open batteries in thisroom shall be considered: provision of an eye wash station, type of paintetc... The fans in this battery room shall be suitable for operation in Zone 1for Group IIC gases. Hydrogen detection shall be installed. On hydrogendetection the battery charge shall be switched off and all ignition sources inthe room shall be suppressed, with the exception of the electrical equipmentcertified for Zone 1 Group IIC gases.

7.2. Dilution ventilation criteria

7.2.1. Open batteries

The minimum air flow Q in m3/h required is:Q = 0.05 I N where "I" is the maximum charging current in Ampere (A) and Nis the number of elements.

The value of the maximum charging current "I" depends of the battery charger'sprotections and shall be stated by the supplier.• For a certified charger fitted with downstream current protections which shut

down the charger supply on maximum charging current, the value of "I" maybe assumed to be 0.2 x C (capacity in Ah) for a rough estimation of theventilation. This shall be checked as soon as the supplier's data is available.

• For a charger fitted with upstream maximum current protections only, thevalue of "I" cannot and shall not be estimated without supplier’s data.

7.2.2. Certified Recombination batteries

The use of certified recombination batteries is justified only if they areassociated with a certified charger fitted with downstream protections which shutdown the charger supply on maximum charging current.

In this case only the minimum air flow Q in m3/h required is:Q = 0.0025 I N where "I" is the maximum charging current in Ampere (A) and Nis the number of elements.The value of "I" may be assumed to be 0.2 x C (capacity in Ah) for a roughestimation of the ventilation. This shall be checked as soon as supplier's data isavailable.



8. HYDROCARBON STORAGE

For storage containing Category C or non-hazardous fluids on release, IP-15, Section 3 shall beadhered to. This is illustrated in sections 8.1, 8.2 and 8.3 of this chapter. As part of thisspecification, IP-15 recommendations shall apply even if the ambient temperature exceeds 30°C.

8.1. Under-ground or within-embankment storage tanks :

For under-ground or within-embankment storage tanks containing liquids of Class I, II(2)or III(2), the extent and classification of hazardous areas around the surface vents dependon whether the tank is pump or gravity fed. Refer to IP-15, Section 3 for more details.

8.2. Overhead, fixed roof storage tanks :

For Liquids of Classes I, II(2) or III(2), (normally of Category C on release) - the extentand classification of the hazardous areas shall be as shown below :

Zone 0 2 m

3 m

3 m

Zone 1

Zone 2

Pit, if any, Zone 1

Figure - 8.1 - Fixed roof tank (Fluid class I, II(2) & III(2)).

Liquids of Classes II(1) or III(1) or unclassified are normally non-hazardous on release.Considering however the possible changes in ambient temperature, and that the flash-pointof heavy fuels or bitumen in heated storage is not reliable, it is recommended to classifythe ullage space as Zone 0, with a small Zone 1 around roof vents and openings.

Zone 0

1 mZone 1

Figure - 8.2 - Fixed roof tank (Fluid class II(1), III(1) or unclassified).



8.3. Overhead, Floating roof storage tanks :

For floating roof storage tanks containing liquids of Classes I, II(2) or III(2) that arenormally of Category C on release, the extent and classification of hazardous areas shall beas shown below :

Zone 1

2 m

2 m

Zone 2

Pit, if any, Zone 1

Figure - 8.3 - Floating roof tank (Category C on release).

8.4. LPG storage stored under pressure :

The extent and classification of hazardous areas around storage vessels containing Class 0liquids (LPG) shall be based on French regulation, namely the "Arrété du 9 novembre1972" for liquefied hydrocarbons stored under pressure at more than 0°C ambienttemperature (Class A2 under French classification). Refer to Figures 8.4 and 8.5 below :

5 m

7.5

m

7.5 m 7.5 m

Ground

Storage vessel Capacity < 200 m3

PSV dischargeassumed to be at this location

Zone 2

Zone 1

7.5

m

Figure 8.4 - Storage vessel < 200 m3



Ground

Storage vessel Capacity > 200 m3

PSV dischargeassumed to be at this location

10 m0.6 m

Zone 2

Zone 1

15 m

Figure 8.5 - Storage vessel > 200 m3

Notes on Figures 8.4 and 8.5

1. The figures are the cross-sections of the LPG storage vessel which contain the PressureSafety Valve (PSV) discharge point. The Zone 1 envelope is a sphere centred around thePSV discharge point, and the Zone 2 envelope is made of cylinders with a vertical axiscontaining the PSV discharge point.

2. The size and shape of the hazardous areas are determined by the location of the storagevessel and the volume of the vessel containing LPG under pressure (less or more than200 m3). They do not depend on the shape of the storage vessel (sphere, cylinder..).

3. The hazardous areas generated by piping connections, sample points, instrument ventsetc. shall be determined as per the standard rules given in chapter 3.

8.5. Refrigerated LPG storage :

The case of LPG stored at atmospheric pressure (below 0°C) is outwith the scope of thisspecification. Refer to the local regulations and standards prevailing in the country ofapplication.

8.6. LNG storage

NFPA 59A or more stringent national regulations shall be followed.



9. MISCELLANEOUS

9.1. Laboratories

A laboratory is a specific closed room or building where analyses are carried out bypersonnel. It contains potential sources of release such as hydrocarbon gas samples, andvapours from heated hydrocarbon liquids. Some of the equipment used for hydrocarbongas and liquid analysis cannot be made suitable for use in a hazardous area (e.g.chromatograph) and therefore shall be considered as ignition sources. Also some leaksources may be toxic for health. Dilution ventilation (refer to § 2.6.3) shall beimplemented in laboratories to ensure that they can be continuously and safely occupied bypersonnel.

All products contained in laboratories shall be checked for toxicity and flammability.Dilution ventilation rates shall be determined on a case by case basis to take intoconsideration the hazards specific to each case. The following dilution rates apply only inthe laboratories containing no toxic materials and no sources of primary grade of release.They shall be considered by default until the leak rates of secondary grade releases areassessed.1. A laboratory handling flammable gases or liquids shall be provided with an exhaust fan

certified for Zone 1, which will achieve a ventilation rate of at least 12 air changes/h.2. A fume cupboard shall also be provided, with an exhaust fan certified for Zone 1 which

will achieve a ventilation rate of at least 30 air changes/h.

Fixed lighting and electrical connections inside the laboratory shall be certified for Zone 2.The inventory of flammable products in laboratories shall be minimised: flammable productsother than the minimum quantities necessary for the day-to-day work shall be stored outsidethe laboratory, in suitable locations.

As far as the surroundings are concerned, a laboratory should be regarded as adequatelyventilated, and classified Zone 2. A laboratory should be a separate building, located in anon-hazardous area. If incorporated in a larger building, it should be completely isolatedfrom other parts of the building. For laboratories where a pressure below that of thesurrounding area is maintained, air-locks may be permitted between the laboratory and theremainder of the building. The laboratory ventilation system shall be independent from theventilation of the remainder of the building.The doors of a laboratory should be self-closing and of a vapour-tight design. Thehazardous areas generated by the doors (vapour-tight or not) and the fan exhausts shallextend to 3 m as shown in Figure 9.1.

Figure 9.1 - Laboratories3 m

Adequate ventilation

Laboratory

3 m

Self-closing airtight door

ZONE 2

Exhaust fan creating under pressure



9.2. Analyser shelters

An analyser shelter or house is a specific closed room or building containing one or moreanalysers for samples of flammable fluids which are or may be connected to a processinstallation together with electrical equipment and auxiliary devices (IEC 79-16).

The design of analyser shelters shall adhere to the requirements of GS SAF 216, IEC 79-16 and IEC 1285. In particular:

The analyser shelter shall be a separate building or shall be completely isolated from otherparts of the building.

If the analyser shelter is located in a hazardous area the ingress of the external atmosphereinto the shelter shall be prevented by an internal overpressure produced by forcedventilation (refer to § 2.7.1).

The analyser shelter containing ignition sources (e.g. electrical apparatus not suitable foroperation in Zone 2) and secondary grade of release sources shall be provided withdilution ventilation (see § 2.6.3). The dilution ventilation shall ensure 30 air changes perhour as a minimum (IP-15).

Primary, continuous grade of release sources shall be vented, and sampling operationswhich involve the intentional release of flammable substances shall be carried-out in asuitable location outside the shelter. Hydrocarbon vent lines shall be fitted with a flamearrester.If a primary source cannot not be vented outside the shelter, dilution ventilation shall beprovided even if there are no ignition sources in the shelter (this shall require a derogationto this specification approved by COMPANY and an assessment of the dilution rate).

The analyser shelters containing toxic sources (e.g. hydrocarbon gas containing H2S) shallbe provided with dilution ventilation. The dilution ventilation rate shall be assessed on acase by case basis to make the shelter safe for personnel.

False ceilings and floors shall not be used in analyser shelters. Blow out panels should beprovided to minimise the consequences of an explosion.

9.3. Small storage of flammable products

This section addresses the case of portable containers with small volumes of flammableproducts e.g. bottles containing liquefied hydrocarbons or hydrocarbon gases underpressure (acetylene, LPG..). Storage locations should be identified and designated on lay-outs during the design of an installation for this equipment such that the hazard of ignitionor explosion associated with such storage be minimised.

Since a leak from properly designed containers can be only accidental, such containersshould generate a hazardous area Zone 2, extending X m from the envelope of thecontainers(s). X should be determined as per Table 3.6 – flanges and valves i.e. X=3 forfluids of Categories A, B and G, X=1.5 for fluids of Category C.



9.4. Loading an filling operations (road tanker, rail car, drum filling)

Refer to IP-15, Section 3.

9.5. Jetties (loading, discharge)

Refer to IP-15, Section 3.

9.6. Air intakes

Air intakes shall be located to prevent ingress of flammable gas or vapour in areascontaining ignition sources: e.g. air intakes to heating and ventilation systems and tocombustion chambers.

Air intakes shall be located at least 2 m away from the border of any hazardous area.

9.7. Air exhausts

Ventilation (adequate, non-adequate and purging) air exhausts from a classified enclosedarea should generate a hazardous area of 3 m radius with the same classification as theenclosed area.

9.8. Chimneys and exhausts

Exhaust and chimneys releasing hot gases shall not be located in hazardous areas Zone 1or Zone 0.

They may be installed in hazardous areas Zone 2 only if their external skin temperaturedoes not exceed 250°C.The external skin temperature limits as given above apply to all hot exhaust chimneyswithin the restricted areas of all petroleum installations (for the definition of the restrictedarea refer to GS SAF 253).

Chimney outlets shall be at least 2 m away from the border of any hazardous area Zone 2and 9 m away from the border of any hazardous areas Zone 1 or 0.There is one exception to this rule: vents from turbine lube oil tanks, although generating aZone 1 hazardous area, may exit into the outlet of the turbine's main exhaust chimney. Thisstandard design is regarded as safe considering the risk specific to this situation.

9.9. Flares

Flares shall be installed in a non-hazardous area but this is not sufficient.

COMPANY rules (refer to GS SAF 262 Safety Rules for Hydrocarbon DisposalSystems § 4.1.1) require that flares are located so as to prevent the ignition of a flammablegas cloud resulting from accidental releases, including leaks from process or storage unitsor releases from vents of the installation (a leak from the flare header is not considered).This goes far beyond area classification requirements. Gas dispersion calculation shall becarried out to determine the minimum height of the flare (for elevated flares) or the



minimum distance between the flare and other process/storage units in the installation tomeet the requirements.

9.10. Traffic

9.10.1 Roads and railways (onshore)

The main roads of a plant (peripheral roads) shall be kept no less than 2 m awayfrom the border of any Zone 2 and 9 m away from the border of any Zone 1 andZone 0.

If this is not practicable, traffic restrictions shall be implemented based on fixedgas detection which initiates visual and audible alarms (design and riskmitigation measures shall be approved by COMPANY).

The safe distances should be materialised by signs wherever an access roadenters a hazardous area.

For railways, refer to IP-15.

9.10.2 Helidecks, helipads and air strips

Any point of these areas as well as any area being part of an helicopter/planeapproach zone shall be no less than 2 m away from the border of any Zone 2 and9 m away from the border of any Zone 1 and Zone 0.

If this is not practicable, traffic restrictions and control procedures shall beimplemented: fixed gas detection which initiates visual and audible alarms,presence of a HLO (Helicopter Landing Officer) or other personnel qualified toauthorise landing and take-off (design and risk mitigation measures shall beapproved by COMPANY).

9.10.3. Boats

The boat landing and/or the mooring facilities shall be such that tugs or supplyboats are kept 2 m away from the border of any hazardous area Zone 2 and 9 maway from the border of any hazardous areas Zone 1 and 0.

If this is not practicable, traffic restrictions shall be implemented based on fixedgas detection which initiates visual and audible alarms (design and riskmitigation measures shall be approved by COMPANY).

This requirement covers not only the ship hull and decks but also its chimney,radio aerials and radar antenna and other appurtenances regarded as sources ofignition.

9.11. Purging

Purging is the operation of passing a quantity of air through an enclosure and its associatedducts in order to reduce any concentration of flammable gas or vapour within them to asafe level (from IEC 79-16).



The purging process shall last long enough to keep the flammable gas content under 25 %of the lowest flammable limit in the worst conditions. In any case the minimum volume ofsweeping air shall be five times the total volume of the enclosure/premises. Purging shallbe done with air being totally free of flammable gas. This shall be established withflammable gas detectors, fixed or portable. For the precautions specific to the operation offired heaters refer to GS SAF 227 §5.

Care shall be taken that all areas have been effectively purged, particularly the confinedareas such as :1. pits, if heavier than air gas or vapour is present,2. ceiling recesses if lighter than air gas or vapour is present,3. blind corners.

Flammable gas detectors shall be used to check all spots where gas is likely to accumulate.



9.12 Classification of enclosed buildings

The classification of the enclosed buildings shall be based on the rules defined in thisspecification, particularly in chapter 4, with due consideration for ventilation andpressurisation (as per chapter 2).

This section is intended to provide examples of the application of these rules, as shown inFigure 9.2.

Figure 9.2 - Classification of enclosed buildings

Ordinary door

Self-closing airtight door

ZONE 2

Ventilation fan

ZONE 1

Note 1 : Zone classification and extent to be defined according fig. 4.8 and 4.9 assuming the door is wide open. Installation of self-closing airtight door is recommended.


2nd degree source

Not

e 1

No leak source

Not adequately ventilated

3 m

Not

e 1

3 m


2nd degree source

Not

e 1


2nd degree source

Not

e 1

No leak source


3 m 3 m

Not

e 1

Pressurised as defined in section 2.7

No leak source

Documents

Gs Saf 216a-Area Classification