Exploration & Production
GENERAL SPECIFICATION
SAFETY
GS EP SAF 216
Area classification
05
01/2011
Extent of hazardous areas modified for pumps, compressors,
pig traps, flanges and valves, as well as wellheads
04
10/2009
Sections 2, 8,11, 12, Appendix 5, 8 and 9 updated Appendix
12 created
03
10/2008
Reviewed and rewritten in accordance with IP 15 3rd edition
02
10/2005
Addition of EP root to document identification and replaced
reference API RP 500 by API RP 505
Rev.
Date
Owner: EP/HSE
Notes
Managing entity: EP/SCR/ED/ICS
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
Exploration & Production
Date: 01/2011
General Specification
Rev: 05
GS EP SAF 216
Contents
1. Scope ....................................................................................................................... 5 1.1 Purpose .............................................................................................................................5 1.2 Applicability ........................................................................................................................5 2. Reference documents ............................................................................................. 6 3. Terminology and definitions .................................................................................. 9 4. Area classification procedure .............................................................................. 13 4.1 Scenarios .........................................................................................................................13 4.2 Procedure ........................................................................................................................14 4.3 Deliverables .....................................................................................................................14 5. Partition between hazardous and non hazardous areas ................................... 14 6. Hazardous zones ................................................................................................... 15 6.1 Sub division of hazardous areas into hazardous zones ..................................................15 6.2 Hazardous Zone ranking .................................................................................................16 7. Classification of open, sheltered and enclosed areas ....................................... 20 7.1 Open areas ......................................................................................................................20 7.2 Sheltered areas ...............................................................................................................20 7.3 Enclosed areas ................................................................................................................21 8. Determination of the hazard radius ..................................................................... 23 8.1 Characteristics of petroleum fluids...................................................................................23 8.2 Hazard radius ..................................................................................................................25 8.3 Typical sources of release ...............................................................................................25 8.4 Procedure for continuous and primary grade releases ....................................................26 8.5 Procedure for secondary grade releases .........................................................................26 8.6 Particular case of sheltered areas ...................................................................................26 9. Sizing and drawings of hazardous areas ............................................................ 27 10. Drilling rigs, equipment and well operations ...................................................... 27 11. Internal combustion engines and fire heaters .................................................... 27 11.1 Gas turbines ....................................................................................................................27 This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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11.2 Gas engines.....................................................................................................................29 11.3 Liquid fuel engines ...........................................................................................................29 11.4 Fired heaters....................................................................................................................30 12. Accumulator batteries in buildings ..................................................................... 30 12.1 Basics ..............................................................................................................................30 12.2 Location and hydrogen detection.....................................................................................31 13. Hydrocarbon storage ............................................................................................ 31 13.1 Under-ground or within-embankment storage tanks ........................................................31 13.2 Overhead, fixed roof storage tanks..................................................................................31 13.3 Overhead, floating roof storage tanks..............................................................................31 13.4 LPG storage tanks ...........................................................................................................31 13.5 Refrigerated LPG storage ................................................................................................31 13.6 LNG storage ....................................................................................................................32 14. Miscellaneous ........................................................................................................ 32 14.1 Laboratories .....................................................................................................................32 14.2 Analyser shelters .............................................................................................................32 14.3 Small storage of flammable products ..............................................................................33 14.4 Loading and filling operations (road tanker, rail car, drum filling) ....................................33 14.5 Jetties (loading, unloading) ..............................................................................................33 14.6 Air intakes ........................................................................................................................33 14.7 Air exhausts .....................................................................................................................33 14.8 Chimneys and exhausts ..................................................................................................33 14.9 Flares ...............................................................................................................................34 14.10 Traffic ...............................................................................................................................34 14.11 Purging ............................................................................................................................34 14.12 Classification of enclosed buildings .................................................................................35 Bibliography................................................................................................................. 36 Appendix 1 Table of hazardous equipment ...........................................................................37 Appendix 2 Area classification procedure ............................................................................38 Appendix 3 Procedure for assessing type and degree of ventilation .................................39 Appendix 4 Guidelines for the determination of the level of ventilation of sheltered areas40 Appendix 5 Determination of hazard radii (R1) values for equipment.................................41 This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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5.1 Equipment/arrangements generally generating continuous or primary grade releases .....41 5.2 Equipment/arrangements generally generating secondary grade releases .......................45 Appendix 6 Sizing of hazardous zones..................................................................................47
Appendix 7 Drilling rigs, equipment and well operations ....................................................50 7.1 Foreword ............................................................................................................................50 7.2 Drilling, workover and pulling operations on Non Live Wells .............................................50 7.3 Surface mud systems.........................................................................................................51 7.4 Rig gas vent .......................................................................................................................51 7.5 Well servicing (Wire-line - Coiled tubing - Snubbing) operations on Live Wells.................52 7.6 Wellheads in production operation .....................................................................................52 Appendix 8 Gas turbines .........................................................................................................61 Appendix 9 Gas/liquid fuel engines and heaters ..................................................................65 9.1 Gas engines .......................................................................................................................65 9.2 Diesel engines ...................................................................................................................65 9.3 Fired heaters ......................................................................................................................66 Appendix 10 Hydrocarbon storage ..........................................................................................68 10.1 Overhead, fixed roof storage tanks ....................................................................................68 10.2 Overhead, floating roof tank (Category C on release) .......................................................68 10.3 LPG storage stored under pressure ...................................................................................69 Appendix 11 Miscellaneous ......................................................................................................70 11.1 Laboratories .......................................................................................................................70 11.2 Small storage of flammable products .................................................................................70 11.3 Air intakes ..........................................................................................................................70 11.4 Air exhausts .......................................................................................................................70 11.5 Chimneys and exhausts .....................................................................................................70 11.6 Traffic .................................................................................................................................70 11.7 Enclosed buildings .............................................................................................................71 This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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1. Scope
1.1 Purpose
This specification defines the method called Area classification used to classify the locations
where a flammable atmosphere may occur in such frequencies as to require special precautions
for the construction and use of electrical apparatus or other potential ignition sources.
Area classification consists in:
 The partition of a facility into hazardous and non hazardous areas,
 The sub-division of hazardous areas into hazardous zones,
 The sizing of the hazardous zones.
1.2 Applicability
This specification applies to:
 New or modified installations constructed by Company or affiliates both onshore and
offshore including LNG and LPG plants
 All E&P operations: drilling, production, treatment, storage and bulk distribution
operations.
The scope is limited only to petroleum fluids and all other flammable products that are present
in the installations.
This specification does not apply to:
 Toxic gases (which on manned installations may lead to more stringent rules),
 Combustible dusts,
 Ignitable fibres,
 Marine facilities covered by the IMO code (International Maritime Organisation) e.g.
tankers.
Particular case of F(P)SO’s:
 This specification applies to the whole production deck facilities on FPSO’s (Floating,
Production, Storage and Offloading) and to utilities on FSO’s (Floating, Storage and
Offloading),
 For all spaces in the hull of a F(P)SO or concerning the cargo deck, GS EP SAF 380
applies, which refers to IEC 60092-502,
 The battery limits between the process areas where GS EP SAF 216 applies and marine
areas where GS EP SAF 380 / IEC 60092-502 applies is defined hereafter:
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Figure 1 - Battery limits on FP(S)O's
The case of tankers at berth that generate a hazardous area on unit limits is covered in section
14.5 of this document.
This specification is not retroactive: its application to the facilities put in operation before the
issue of this specification is not mandatory.
2. Reference documents
The reference documents listed below form an integral part of this General Specification. Unless
otherwise stipulated, the applicable version of these documents, including relevant appendices
and supplements, is the latest revision published at the EFFECTIVE DATE of the CONTRACT.
For the classification of hazardous areas in Company petroleum installations, GS EP SAF 216
can be used as a stand-alone document unless a relevant National Regulation is applicable.
It complies with IEC 60079-10-1 “Classification of hazardous areas”.
Since IEC 60079-10-1 does not provide detailed recommendations regarding the extent of the
hazardous areas in specific industries and applications and allows reference to other codes,
GS EP SAF 216 is mainly based on IP Code, Part 15.
The general philosophy of IP Code, Part 15 and a lot of its detailed recommendations are
adopted.
This specification and IP Code, Part 15 differ mainly in areas not adequately covered by the
code or where the code requires interpretation. Also, differences will be found regarding the
area classification of some standard equipment/arrangements (namely pumps, compressors,
pig traps, flanges and valves, as well as wellheads): for the sake of simplification and
consistency between installations, Company purposely specifies hazardous area extent in line
with former publications of the code and the GS so as to use well-established, widely accepted
hazard radii.
In some cases reference is made to standards other than IP Code, Part 15, including
API RP 505, although the latter shall not be used as a general reference.
The definitions of zones comply with the requirements of the ATEX Directive 1999/92/EC.
After the hazardous zones have been determined, the compatibility of all electrical equipment or
any potential ignition sources with the zoning classification shall be ensured (see the relevant
General Specifications of Company by discipline for the design, installation and use of
equipment with potential ignition source).
This document is the property of Total. It must not be stored, reproduced or disclosed to others without written authorisation from the Company.
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Some of the specifications issued by the Company disciplines (instrumentation, electricity,
mechanics, HVAC, etc.) require ATEX-certified equipment (in conformity with
ATEX Directive 1994/09/EC).
Standards
Reference
Title
EN 1834-1
Reciprocating internal combustion engines - Safety requirements
for design and construction of engines for use in potentially
explosive atmospheres Part 1: Group II engines for use in
flammable gas and vapour atmospheres
IEC 60079-10-1
Explosive atmospheres – Part 10-1: Classification of areas –
Explosive gas atmospheres
IEC 60079-13
Electrical Apparatus for Explosive Gas Atmospheres Part 13:
Construction and Use of Rooms or Buildings Protected by
Pressurization
IEC 60079-16
Electrical Apparatus for Explosive Gas Atmospheres Part 16:
Artificial Ventilation for the Protection of Analyzer(s) Houses
IEC 60079-20-1
Explosive atmospheres – Part 20-1: Material characteristics for
gas and vapour classification – Test methods and data
IEC 60092-502
Electrical Installations in Ships – Part 502: Tankers - Special
Features
IEC 61285
Industrial-Process Control - Safety of Analyser Houses
IEC 61892-6
Mobile and fixed offshore units – Electrical installations
Part 6: Installation
IEC 61892-7
Mobile and fixed offshore units – Electrical installations
Part 7: Hazardous areas
ISO 10418
Petroleum and natural gas industries - Offshore production
installations - Analysis, design, installation and testing of basic
surface process safety systems
ISO 23251 / API STD 521
Petroleum and natural gas industries—Pressure-relieving and
depressuring systems
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Professional Documents
Reference
Title
API Publ 4615
Emission Factors for Oil and Gas Production Operations
API RP 505
Recommended Practice for Classification of Locations for
Electrical Installations at Petroleum Facilities Classified as Class I,
Zone 0, Zone 1, and Zone 2
API RP 2216
Ignition Risk of Hydrocarbon Liquids and Vapors by Hot Surfaces
in the Open Air
NFPA 59A
Production, storage, and handling of Liquefied Natural Gas (LNG)
Regulations
Reference
Title
ATEX Directive 1994/09/EC Directive 1994/09/EC of the European Parliament and of the
Council of 23 March 1994 on the approximation of the laws of the
member states concerning equipment and protective systems
intended for use in potentially explosive atmospheres
ATEX Directive 1999/92/EC Directive 1999/92/EC of the European Parliament and of the
Council of 16 December 1999 on minimum requirements for
improving the safety and health protection of workers potentially at
risk from explosive atmospheres
Arrêté du
9 novembre 1972 modifié
au 28 avril 2008
Aménagement et exploitation de dépôts d’hydrocarbures liquéfiés
Codes
Reference
IP Code, Part 15
Title
Area classification code for petroleum for installations, part 15 of
the Institute of Petroleum Model Code of Safe practice
Other documents
Reference
Title
Not applicable
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Total General Specifications
Reference
Title
GS EP CIV 402
Design and construction of oil field laboratory on production
installations
GS EP ELE 001
Electrical design criteria
GS EP ELE 021
Electrical design criteria for floating units
GS EP ELE 079
Electrical apparatus for potentially explosive gas atmospheres
GS EP HVA 100
HVAC Basis of design
GS EP SAF 021
Layout
GS EP SAF 221
Safety rules for buildings
GS EP SAF 222
"Safety rules for turbines, diesel engines, gas engines and
process units in sheltered or enclosed areas"
GS EP SAF 227
Safety rules for fired heaters
GS EP SAF 228
Liquid drainage
GS EP SAF 253
Impacted area, restricted area and fire zones
GS EP SAF 262
Pressure protection relief and hydrocarbon disposal systems
GS EP SAF 312
Fire and gas detection systems
GS EP SAF 380
Safety engineering requirements for an F(P)SO
3. Terminology and 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 derogation approved by Company.
Should
Is to be understood as strongly recommended to comply with the
requirements of the specification. Alternatives shall provide a similar
level of protection and this shall be documented.
May
Is to be understood as permission.
Can
Is to be understood as a physical possibility.
Must
Expresses a regulatory obligation
Note that “will” is not to be understood as a statement. Its use is to be avoided, unless it is
necessary to describe a sequence of events.
For the purpose of this specification, the following definitions shall apply:
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Adequate ventilation
Natural, artificial, or a combination of both ventilations, sufficient
enough to avoid persistence of flammable atmospheres within
sheltered or enclosed areas but insufficient to avoid their initial
formation and spread throughout the area. This will normally be
achieved by a uniform ventilation rate of a minimum of twelve air
changes per hour with no stagnant areas (IP Code, Part 15)
Air-lock
Two self-closing vapour-tight doors with a space in between (the
“gap”) kept above the pressure prevailing in the adjacent hazardous
area. The minimum pressure difference between the gap and the
hazardous area shall be 25 Pa (0.25 mbar). A local alarm buzzer
plus an alarm sounding and lighting in the main control room are to
be provided to warn the operators and personnel if both doors are
open simultaneously. Loss of differential pressure in the gap
between the two doors shall also alarm in the main control room
Area
For the purpose of this specification, an area is a three-dimensional
region or space (as per IEC 60079-10-1)
Area classification
Area classification is the assessed division of a facility into
hazardous areas and non-hazardous (or not classified or safe)
areas, and the sub-division of hazardous areas into zones (refer to
section 5.3 of IP Code, Part 15).
Competent
Person who by combination of training, experience and supervision
is able to make objective judgments
Dilution ventilation
Artificial ventilation sufficient to maintain generally as nonhazardous an enclosed area containing a source of release or an
aperture into a hazardous area (IP Code, Part 15).
In the case of a turbine enclosure, this will normally be achieved by
a uniform ventilation rate of a minimum of ninety air changes per
hour with no stagnant areas (Company definition from
IP Code, Part 15)
Emergency Shutdown
(ESD)
Control actions undertaken to shutdown equipment or process in
response to a hazardous situation (ISO)
Emergency Shutdown
System
System, activated by automatic or manual signals, which
undertakes the control actions to shutdown equipment or processes
in response to a hazardous situation (ISO 10418)
Enclosed area
Any building, room or enclosed space within which, in the absence
or failure of artificial ventilation, the air movement will be limited
and any flammable atmosphere will not be dispersed naturally
(IP Code, Part 15)
ESD system
System of manual stations and automatic devices that, when
activated, initiate a shutdown of the installation
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Fire and Gas system
(F&G)
The Safety System which monitors the temperature or the energy
flux (fire), the concentration of flammable or toxic gases (gas), and
initiates relevant actions (alarm, ESD, emergency depressurisation,
active fire-fighting, electrical isolation) at pre-determined levels
(Company)
Fired heater
A vessel in which the temperature of a fluid is increased by the
addition of heat supplied by a flame within the vessel (Company
from API). Fired heater is a generic term that covers all type of
heaters including steam boilers, reboilers (flame tube or flue gas
tube), indirect heaters (hot oil or hot water), incinerators, etc.
For the purpose of this specification, fired heaters are sorted out into
the following classes:
 Class A: a heater that has heat utilisation equipment operating
at approximately atmospheric pressure wherein there is a
potential explosion or fire hazard that could be created by the
presence of flammable volatile or combustible materials
processed or heated in the heater
 Class B: a heater that has heat utilisation equipment operating
at approximately atmospheric pressure wherein there are no
flammable volatile or combustible materials being heated
Flammable atmosphere Mixture of flammable gases or vapours with air in such a proportion
that, without any further admixture, it will burn when ignited. In the
context of area classification the term “flammable” is preferable to
“explosive” (IP Code, Part 15)
Flammable limits
(upper, lower)
The limits of combustibility of flammable gases or vapours when
mixed with air (IP Code, Part 15)
Flash-point
Lowest temperature to which a liquid must be heated to give off
sufficient vapour to form a flammable mixture with air. Ignition does
not occur at the flash point unless there is a source of ignition
(IP Code, Part 15)
FPSO
Floating, Production, Storage and Offloading system includes, in
addition to storage and offloading capability, facilities for receiving
crude oil from producing wells and processing it for export by
separating water and gas (OGP)
FSO
Floating, Storage and Offloading system consisting of a ship or
barge-shaped floating hull incorporating tanks for storage of
produced oil, and a method of loading the oil onto off take tankers
(OGP)
Fuel source
Same as ISO definition of "source of release" (API)
Hazard radius
The hazard radius of a source of release is the largest horizontal
extent of the hazardous area that is generated by the source when
situated in an open area under unrestricted natural ventilation
(IP Code, Part 15)
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Hazardous area and
zone
A hazardous area is defined as a three dimensional space in which
a flammable atmosphere may be expected to be present at such
frequencies as to require special precautions for the control of
potential ignition sources (IP Code, Part 15). All other areas are
referred to as non-hazardous areas in this context. In a hazardous
area three types of zones (0, 1 and 2) are recognised
(IP Code, Part 15)
HVAC
Abbreviation for Heating, Ventilating and Air Conditioning
Ignition source
Source of temperature and energy sufficient to initiate combustion
(API)
The temperature at which a substance will begin to burn without
Ignition temperature
application of any source of ignition (IP Code, Part 15). The test
(synonymous with
conditions shall be as per IEC 60079-20-1
“auto”- and “selfignition temperatures”)
Interceptor/coalescer
Vessel open or vented to 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 (IP Code, Part 15)
Laboratory
A specific closed room or building where analyses are carried out by
personnel
Normal operation
Operation within the plant design parameters, including start-ups,
shutdowns, routine maintenance and any degraded modes of
operations foreseen during design
Open area
An area that is outdoors without stagnant regions, where vapour is
rapidly dispersed by wind and natural convection (IP Code, Part 15)
Over pressurisation
Artificial ventilation of an enclosed area to maintain the area at a
controlled pressure above the ambient pressure (IP Code, Part 15)
Over pressure obtained by artificial ventilation is referred to as
simply over pressurisation in this specification
Safe area
Other term used for non hazardous or not classified area
Self-closing doors
Doors that are designed to close by themselves and to remain
closed if not intentionally opened or kept opened
Sheltered/obstructed
area
An area within or adjoining an open area (which may include a
partially open building or structure) where, owing to obstruction,
natural ventilation is restricted and less than in a true open area
(IP Code, Part 15)
Source of release
Point from which a flammable gas, vapour or liquid may be released
into the atmosphere (ISO)
Sump
A vessel, open or vented to atmosphere, 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
an appreciable part of the total liquid entering (IP Code, Part 15)
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Under pressurisation
Artificial ventilation of an enclosed area to maintain the area at a
controlled pressure below the ambient pressure (IP Code, Part 15)
Under pressure obtained by artificial ventilation is referred to as
simply under pressurisation in this specification
Units
Areas within the installation resulting from its partition into a
reasonable number of geographical and functional groups of
equipment having the same type (e.g. hydrocarbon, pressure,
inventory or ignition) and levels (high, medium, low) of risks
(Company)
Ventilation (natural,
artificial)
Ventilation is a general term to indicate air movement and
replacement by fresh air. Natural ventilation refers to ventilation
caused by wind or convection effects. Artificial ventilation refers to
ventilation caused by air purges or mechanical means (fans)
(IP Code, Part 15).
4. Area classification procedure
The objective of the area classification is to reduce as much as possible the probability of
coincidence of a flammable atmosphere and an ignition source.
The area classification shall be carried out before choosing appropriate electrical equipment or
any equipment generating ignition sources.
The area classification process reduces the installation overall risk level through design
improvements.
Additionally, the optimisation of the equipment layout shall be carried out to decrease the risk of
ignition (e.g. pertinent grouping of equipment, optimisation of ventilation).
A flow diagram summarizing the basic steps of the procedure is included in Appendix 2.
4.1 Scenarios
The classification of hazardous areas takes into consideration events which are "liable to occur
during normal or abnormal plant operating conditions” (IP Code, Part 15).
Events not considered for Area Classification:
 Large gas/vapour releases from process vents or flares. Such releases shall require
appropriate dispersion calculations
 Failure scenarios which are very unlikely to occur, such as the rupture of a process vessel
or pipe (IEC 60079-10-1). For these scenarios reliance is placed on the Emergency
Shutdown System and safety distances resulting from consequence analysis calculations
(refer to GS EP SAF 253) to mitigate the consequence of a failure in the installation.
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4.2 Procedure
Area Classification shall be carried out by competent persons 1.
Area classification shall be conducted in 5 steps (IP Code, Part 15):
 Partition of the installation into hazardous and non hazardous areas by identification
of all the potential release sources of flammable products,
 Sub-division of hazardous areas into hazardous zones which shall be ranked
according to the estimated probability of the presence of a flammable atmosphere,
 Determination of the hazard radii around each potential source of release,
 Sizing of the hazardous Zone around each potential source of release,
 Prepare/modify the hazardous area drawings; draw the envelopes of the zones.
4.3 Deliverables
The following results shall be delivered:
 The table of hazardous equipment as per Appendix 1,
 When relevant, the calculation notes necessary for the hazard radius determination
 The drawings of hazardous zones showing the Zone envelopes and their main
dimensions, the rest of the installation being classified as non hazardous or safe 2.
5. Partition between hazardous and non hazardous areas
The main principles governing the partition between hazardous and non hazardous areas are
as follows:
 All hydrocarbons handled at a temperature above their flash point, or whose flash point is
below 21°C (69.8 °F), are liable to generate hazardous areas,
 A hazardous area is generated when a flammable mixture may be created further to an
equipment release,
 All equipment containing flammable products (for the definition and characterisation of a
flammable product, see section 8.1) shall be considered as potential release sources
where the material quantities exceed the following thresholds:
1
For new projects it is recommended that Area Classification is conducted by a senior safety engineer assisted by a
process engineer. For the modifications of an existing installation the team should include a member of the
operating crew. It should be noted that although the results of Area Classification have direct implications on the
selection of the electrical apparatus, knowledge in electrical matters is not a must for conducting or participating to
an Area Classification exercise.
2
As a requirement regarding the number of hazardous area drawings to be provided: for onshore plant, plan view
and cross sectional view; for offshore plant plan view of each deck level and at least two elevations.
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Table 1 - Capacity thresholds above which hazardous area classification is required
Gas: volume
corrected to 1
bar (a) pressure
Liquefied
flammable gas
Flammable liquid at
a temperature
above its flash point
50 litres
5 litres
25 litres
1000 litres
100 litres
200 litres
Inside
Outside
 All-welded piping, flexible hoses (without fittings such as valves, instruments and flanges)
and instrument tubing designed and constructed according to Company specifications
shall not generate hazardous areas.
6. Hazardous zones
The extent of the hazardous area depends on the rate of release, ventilation conditions, and
fluid properties.
6.1 Sub division of hazardous areas into hazardous zones
GS EP SAF 216 shall be used for:
 Defining the Zones 0 and 1 inside units (see section 6.2.2),
 Defining the Zone 2 contour around the items of equipment located at the deck/unit
surface limits.
The following documents shall be available for the determination of hazardous areas:
 Equipment list,
 A layout drawing showing the position of all equipment, air inlets/exhausts and main
sources of ignition (e.g. furnaces, roadways, flares, etc.),
 The extent of confinement (open, sheltered or enclosed) and HVAC calculations,
 A process flow diagram,
 A piping & instrumentation diagram
 Material identification and process conditions (e.g. temperature and pressure).
The main following information shall be collected in the table included in Appendix 1:
 The equipment type and codification,
 The nature of the hazardous fluid,
 The main characteristics of the hazardous fluid.
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6.2 Hazardous Zone ranking
The determination of the following parameters shall be made in order to evaluate the rank of the
hazardous zone:
 The grade of release as per section 6.2.1,
 The type of area (open, sheltered or enclosed) as per sections 6.2.3 and 7,
 The type of ventilation as per section 6.2.4
All the above information shall be included in the table in Appendix 1.
6.2.1 Grades of release (or types of source)
Three grades of release 3 are defined in terms of their likely frequency and duration.
6.2.1.1 Continuous grade release
A release which is continuous or expected to occur for long periods: the cumulative duration of
release exceeds 1000 hours per year.
Example: Gaseous atmosphere in a hydrocarbon storage tank.
6.2.1.2 Primary grade release
A release which can be expected to occur periodically or occasionally during normal operation:
the cumulative duration of release is in the range of 10 to 1000 hours per year.
Examples: Sampling connection (for regular, open to atmosphere sampling), operating purge,
drain.
6.2.1.3 Secondary grade release
A release which is not expected to occur in normal operation and, if it does, is likely to do so
only infrequently and for short periods: the cumulative duration of release is less than 10 hours
per year 4.
Examples: Flanges, pump seals.
6.2.2 Zones
Hazardous areas shall be identified and classified into Zones 0, 1 or 2 based on the frequency
of the occurrence and duration of a flammable atmosphere.
The classification in zones or “zoning” is the partition of the installation into volumes in which a
flammable atmosphere may be present (see section 3).
The following definitions are from IP Code, Part 15:
 Zone 0
That part of a hazardous area in which a flammable atmosphere is continuously present, or
present for long periods.
3
4
For releases not considered for Area Classification see section 4.1.
Where releases are likely to be present for 1 to 10 hours per year but are anticipated in normal operation (e.g.
routine sampling points) they should be regarded as primary grade releases unless carried out under permit-towork circumstances (IP Code, Part 15).
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 Zone 1
That part of a hazardous area in which a flammable atmosphere is likely to occur in normal
operation.
 Zone 2
That part of a hazardous area in which a flammable atmosphere is not likely to occur in normal
operation, and, if it occurs, will exist only for a short period.
For further guidelines refer to IP Code, Part 15.
"Type of sources" and "zones" are not synonymous as the type of a Zone depends on the level
of ventilation in the considered area and for enclosed areas, the pressure relative to the
surrounding areas and their Zone classification.
Throughout this specification, the zones are represented as follows:
Zone 0
Zone 1
Zone 2
6.2.3 Confinement (types of location)
An area can be classified in three categories with respect to confinement:
 An open area (basically no roof/ceiling, no walls and floor made of grating) or
 A sheltered, partially enclosed, partially confined area (various combinations of solid floor,
ceiling and walls or equivalent obstructions to natural draft) or
 An enclosed area.
The extent of confinement governs the determination of the level of ventilation.
The level of ventilation achievable for the three categories is described below (section 6.2.4).
6.2.4 Ventilation and pressurisation
The openness of an area is an important factor in determining the effectiveness of ventilation
and the extent and severity of a hazardous area.
 Two boundary cases (open area, enclosed area) and an intermediate case (sheltered
or obstructed area) are defined in section 6.2.4.3
 The degree of ventilation (unrestricted, restricted, adequate or inadequate) is a key
factor in determining the Zone classification of an area
 The level and extent of hazardous area classification depends on the ventilation of the
zones where flammable vapours are likely to be present and to accumulate
 Conditions of ventilation and likelihood of detecting the leak may change the Zone
definition for each grade of release.
 This specification defines only the functional requirements for ventilation or pressurisation
systems to effectively dilute flammable gases or prevent the ingress of flammable gases
in areas not suitable for the presence of a flammable atmosphere
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 It is not a specification for the design and operation of ventilation and pressurisation
systems. It does not cover in particular HVAC requirements for human comfort;
temperature control and the extraction of smoke during/after a fire (refer to
GS EP SAF 221 for ventilation in buildings and to GS EP HVA 100 for basis of HVAC
design)
 Ventilation can either be natural when it is caused by wind or convection effects or
artificial when it has to be provided to dilute and remove flammable gases or vapour
released within a room or a building
 Pressure differential with respect to surrounding areas can only be achieved for enclosed
areas and in conjunction with artificial ventilation
 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 impurities which it may contain
produce harmful effects or introduce a reduction of the safety level.
6.2.4.1 Types of ventilation
The different types of ventilation are as follows:
6.2.4.1.1 Adequate/Inadequate ventilation
Adequate ventilation is defined as ventilation sufficient enough to prevent the accumulation of
concentrations of flammable gas-air. This will normally be achieved by a uniform ventilation rate
of at least 12 volumetric air changes per hour with no stagnant areas.
Open areas are considered as adequately ventilated and typically, air velocities will frequently
be above 2 m/s and rarely less than 0.5 m/s.
By definition, any ventilation that does not match the above criteria will be considered as
inadequate which normally results from natural draft less than 0.5 m/s or artificial ventilation rate
less than 12 volumetric air changes per hour (sheltered areas or loss of ventilation of an
enclosed area for example).
6.2.4.1.2 Dilution ventilation
Dilution ventilation shall be sufficient to immediately bring the flammable gas concentration
below 20% of the Lower Flammability Limit (LFL) and keep it so all the time.
Typical ventilation rates covering all scenarios for dilution ventilation cannot be proposed. A
calculation shall be carried-out to estimate hydrocarbon leaks 5 . This can only be achieved by a
very large number of air changes (well in excess of 12 per hour).
It shall be based on the largest secondary grade release.
Should simultaneous releases from more than one secondary grade releases be likely, then the
cumulated release shall be considered.
Ventilation rates higher than those required for dilution ventilation may be required in case
ventilation also serves other purpose than dilution to prevent flammability (e.g. in case toxic
fluids are involved or in case high cooling requirements).
5
Methods to calculate minimum introduction rates to achieve adequate ventilation are proposed in API RP 505
(Appendices B, first edition 11/1997, reaffirmed 11/2002). Unless otherwise specified, the default values for gas
leaking rates should be those of API Publ 4615, assuming the equipment is in poor condition (leaking rates) but
there is no failure (e.g. pipe rupture).
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6.2.4.2 Loss of artificial ventilation in enclosed areas
Loss of artificial ventilation can cause the level of ventilation of the area to be less than dilution
ventilation or even less than adequate. In such event:
 The Zone classification is temporarily down graded,
 All potential sources of ignition incompatible with the downgraded zoning shall be isolated
(electrically or else, with or without delay).
6.2.4.3 Ventilation assessment
A method included in Appendix 3 of this specification will help to assess the type and level of
ventilation for each type of area (open, sheltered or enclosed).
The level of ventilation available in a location shall be established in order to allow Zone
classification:
 Open areas shall be deemed adequately ventilated (natural draft exceeding 2 m/s)
 For sheltered areas (or obstructed areas), the level of ventilation shall be established on
the basis of API RP 505 (see Appendix 4)
 For enclosed areas, ventilation is inadequate; it can be made adequate or better (e.g.
dilution) by providing artificial ventilation to disperse any flammable atmosphere
6.2.4.4 Pressurisation
Pressurisation shall be provided to ensure the protection of a room or building 6:
 Containing electrical equipment or other potential sources of ignition and located in a
hazardous area where flammable gases or vapours may enter (over pressurisation)
 Containing sources of release and surrounding by a safe area containing electrical
equipment or other potential sources of ignition (under pressurisation)
The ingress of gases or vapours into a room is prevented by maintaining inside it a protective
gas at a higher pressure than that of the outside atmosphere.
The egress of gases or vapours from a room is prevented by maintaining inside it a protective
gas at lower pressure than that of the outside atmosphere.
This section does not deal with the electrical apparatus for which protection by pressurisation in
hazardous areas follows the electrical codes (the protection of the electrical apparatus in
hazardous areas shall comply with Company specification GS EP ELE 079).
The protection by pressurisation of rooms and buildings containing electrical equipment shall
comply with IEC 60079-13 and with this specification (some of the requirements of this section
exceed the requirements of IEC 60079-13).
The types of pressurisation and associated construction requirements for buildings are
addressed in IEC 60079-13.
The pressurizing gas shall not, by virtue of any chemical products or impurities which it may
contain, produce harmful effects or introduce a reduction of the safety level.
6
A room or building is an enclosure of sufficient size to permit the entry of a person.
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6.2.4.4.1 Over pressurisation protection
Protection by over pressurisation is achieved when artificial ventilation or static pressurisation
controls the pressure inside an enclosed area sufficiently above that of the surrounding
hazardous area to prevent ingress of a flammable atmosphere from an outside fuel source.
The difference in pressure to be maintained shall be greater or equal to 25 Pa (0.25 mbar).
Overpressure should be monitored or detected by a pressure switch as a minimum.
Loss of overpressure shall initiate an alarm.
Pressurised enclosed areas shall be provided with fixed gas detection as per GS EP SAF 312
to immediately and automatically isolate all ignition sources not suitable for Zone 1 7.
6.2.4.4.2 Under pressurisation protection
Protection by under pressurisation is achieved when artificial ventilation keeps the pressure
inside an enclosed area sufficiently below that of the surrounding area to prevent possible
egress of a flammable atmosphere to an outside less or non hazardous area.
The difference in pressure to be maintained shall be greater or equal to 25 Pa (0.25 mbar).
Under pressure should be monitored or detected by a pressure switch as a minimum.
Loss of under pressure shall initiate an immediate alarm, and isolate all ignition sources located
in the vicinity of the enclosed area and not suitable for Zone 1.
Isolation of these ignition sources on loss of under pressure may be delayed to allow the loss to
be investigated.
7. Classification of open, sheltered and enclosed areas
7.1 Open areas
Where a facility is categorized as an open area (provided with adequate natural ventilation), the
following classification applies:
 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.
7.2 Sheltered areas
For a sheltered or obstructed area, the natural ventilation may be restricted. The level of
ventilation may then be adequate or inadequate (see definitions in section 6.2.4).
When the level of ventilation of a sheltered/obstructed area is assessed as adequate, the
classification rules for open areas shall apply (see section 7.1).
When the level of ventilation of a sheltered/obstructed area is assessed as inadequate, the
area shall be classified as an enclosed area (see table in section 7.3 - “inadequate” column).
7
If gas detection is not provided or if a source of primary grade of release is installed in the building (each of them
requiring derogation to this specification approved by Company), loss of overpressure shall automatically and
immediately isolate all ignition sources not suitable for Zone 1.
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7.3 Enclosed areas
An enclosed area is any building, room or enclosed space within which, in the absence or
breakdown of artificial ventilation, the ventilation will be regarded as inadequate (refer to section
6.2.4).
The Zone classification of the outside areas shall be taken into account when classifying the
enclosed areas in contact (via an aperture) with them unless the enclosed walls, ceilings, floors
and any ducting are vapour-tight by construction.
A vapour-tight door or hatch, locked in normal operation and opened only under a permit 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) shall be considered as an aperture.
The outside areas in contact through an aperture with the enclosed area shall be considered for
classification.
Areas having a direct opening onto another area:
 Shall take the Zone classification of adjacent areas if they are more stringent
 Shall extend their own classification to adjacent areas of openings if they would otherwise
be less stringent.
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Zone classification of enclosed areas
Grade of
internal
release
(1) (3)
Continuous
(1) (3)
Continuous
(1) (3)
Primary
(1) (3)
Primary
(3)
Secondary
Secondary
(3)
Internal
ignition
sources
yes
no
yes
no
yes
no
No source
yes
No source
no
Inadequate
Not allowed
Not allowed
Not allowed
Not allowed
Zone 1 if
surrounded
by a safe
zone
Zone 1 if
surrounded
by a safe
Zone or a
Zone 1 or 2.
Zone 0 if
surrounded
by a Zone 0
or 1
Zone 1 if
surrounded
by a Zone 2
Zone 0 if
surrounded
by a Zone 0
or 1
Zone 1 if
surrounded
by a Zone 2
Adequate
Dilution
(2)
Type of ventilation
Dilution +
Dilution + under
overpressure
pressure
Not allowed
Not allowed
Not allowed
Not allowed
Not allowed
Not allowed
Not allowed
Not allowed
Not classified Not classified if
surrounded by a safe
if surrounded
Zone containing an
by a Zone 0, 1
ignition source
or 2.
Not classified Not classified if
surrounded by a safe
if surrounded
Zone containing an
by a Zone 0, 1
ignition source
or 2.
Overpressure
(4)
Not allowed
Not allowed
Not allowed
Not allowed
Zone 1 or 2 depending on
the ventilation rate, if
surrounded by a safe zone
Under pressure
(4)
Not allowed
Not allowed
Not allowed
Not allowed
Zone 2
Not allowed
Not allowed
Not allowed
Not allowed
Not classified
if surrounded
by a safe zone
Zone 2
Not classified
if surrounded
by a safe zone
Zone 0 if surrounded
by a Zone 0
Zone 1 if surrounded
by a Zone 1
Zone 2 if surrounded
by a Zone 2
Not classified
if surrounded
by a safe zone
Not classified
Not classified if
surrounded by a safe
zone
Not classified
Not classified if
surrounded by a safe
zone
Zone 0 if surrounded
by a Zone 0
Zone 1 if surrounded
by a Zone 1
Zone 2 if surrounded
by a Zone 2
Not classified
Not classified
Not classified
Not classified
Not classified
Zone 1 or 2 depending on
the ventilation rate, if
surrounded by a safe zone
Not allowed
Not allowed
Not allowed
Not allowed
Zone 1 or 2 depending
on the ventilation rate, if
surrounded by a safe
zone
Zone 1 or 2 depending
on the ventilation rate, if
surrounded by a safe
zone
(1)
With the exception of accumulator batteries (see section 12.1), continuous or primary grade sources shall not be located within an enclosed area. Such design
shall require formal derogation to this specification.
(2) An area within a larger enclosure subject to local artificial ventilation, i.e. by extractor fan, shall be classified according to the local ventilation rate in that local
area, i.e. either dilution or adequate ventilation depending on which is met.
(3) With a source of small hazard radius, e.g. a sample point, the local ventilation may be high enough to prevent the source from influencing the classification of
the whole enclosure. There should still be a local Zone 1 or 2 around the source and the extent of this Zone should be greater than in the open air, typically
about twice the extent.
(4) Typical case of living quarters where ventilation rate is low.
General Note: In the above table, ‘If’ to be taken as a restrictive condition
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8. Determination of the hazard radius
This section provides the general requirements for the determination of the hazard radius.
Hazard radii may be determined by either:
 Direct examples limited to common facilities given in sections 10, 11, 12, 13 and 14, or
 A point source method developed in present section 8, or
 A risk based method for secondary grade release equipment or when the release rate
(hole size and pressure) is unknown (IP Code, Part 15).
Hazard radii depend on the following parameters:
 The grade of release (determined in section 6.2.1)
 The fluid category (determined as per section 8.1)
 The release pressure
 The hole release size
For the determination of hazard radii, see Appendix 5.
8.1 Characteristics of petroleum fluids
For Area Classification in petroleum installations, the classification of petroleum fluids shall be
done in two steps, first in classes then in categories:
 The Class of liquid hydrocarbons relates to their flash point and handling temperature at
actual storage or process conditions
 The Category is derived from the class and indicates to which extent a fluid on release
can form a flammable mixture with air. This is a determining factor in the calculation of the
hazard radius (see section 8 and Appendices 5 & 6).
8.1.1 Classification of petroleum fluids based on closed cup flash points
(IP Code, Part 15)
CLASS
0
I
II
III
Fluid
LPG
Liquid hydrocarbon
with TF < 21°C
Liquid Hydrocarbon
with 21°C≤TF<55°C
II(1): TH < TF
II(2): TH≥ TF
Liquid Hydrocarbon
with 55°C≤TF<100°C
III(1): TH < TF
III(2): TH≥ TF
Where: TF is the flash point of the fluid in °C.
TH is the temperature at which the fluid is handled in °C.
Unclassified are liquid hydrocarbons with a flash point above 100°C. However, they should be
considered as class III (2) when handled at, or above, their flash point temperature 8.
8
For further guidance on petroleum fluids classification refer to IP Code, Part 15, Appendix A.
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8.1.2 Fluid Categories
Following are guidelines for application of Categories to the oil and gas production installations
9
.
 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 below 1.1 bar(a).
Category
Definition
G(ii)
Refinery hydrogen
G(i)
A typical methane-rich natural gas.
A
Any flammable liquid that, on release, would vaporise rapidly or substantially.
Includes LPG and lighter flammable liquids e.g. LNG. Also includes any
flammable liquid at a temperature sufficient to produce, on release, more than
40% vol vaporisation with no heat input other than from the surroundings.
B
Any flammable liquid, not in Category A, but at a temperature sufficient for
boiling to occur on release.
C
Any flammable liquid, not in Category A or B, but which can be at a temperature
above its flash point or form a flammable mist or spray.
8.1.3 Relationship between fluid classification and fluid category
The following table may be used to convert classification to fluid category:
CLASSIFICATION OF PETROLEUM BASED
ON CLOSED CUP FLASH POINTS
FLUID CATEGORY
Class
Description
Handled
above
flash
point
0
LPG
Yes
A
I
Flash point less than 21°C
Yes
B
(1)
Handled
above
boiling
point
Can be
released
as mist
A
Handled below
boiling point and
cannot be
released as mist
(2)
A
C
C
(1)
C
C
N/A(1)
C
II
(2)
II
Flash point 21-55°C
Flash point 21-55°C
No
Yes
N/A
B
III (1)
III (2)
Flash point 55-100°C
Flash point 55-100°C
No
Yes
N/A
B
(1)
C
C
N/A(1)
C
Unclassified (1)
(2)
Unclassified
Flash point > 100°C
Flash point > 100°C
No
Yes
N/A(1)
B
C
C
N/A(1)
C
(1) Not applicable because liquids not handled above their flash point cannot be above their boiling point.
(2) Cryogenic fluids need special consideration.
9
For further guidance on petroleum fluids classification refer to IP Code, Part 15, Appendix A.
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8.2 Hazard radius
The hazard radius of a source of release is the largest horizontal and vertical extents of the
hazardous area that is generated by the source when situated in an open area under
unrestricted natural ventilation.
The hazard radius is not the result of a fully deterministic approach. It should be regarded as a
standard to be used when no better method is available. It is not a substitute for good
engineering judgement. For example one may consider that a particular item of equipment gives
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 the gas,
characteristics of the environment and conditions of release. Gas dispersion calculations, if
necessary, shall be carried out as per GS EP SAF 253, using codes (computer programs)
approved by Company.
8.3 Typical sources of release
The typical grades and sources of release for the current standard equipment/arrangements are
included in the following table:
Type of equipment
(1)
Sources of release
Typical release Grade
Seals, vents, drains, valves,
piping flanges, filter/strainers
Secondary
Drains and sample points
Drain sampling point
Primary or secondary
(depends on the frequency of
sampling)
Compressors
Seals and joints
Secondary
Process vents (includes
degassing and cold vents)
Discharge point assuming that
all welded collecting piping =
safe area
Continuous, primary or
secondary (depends on the
frequency of venting)
Instrument vents
Discharge point
Continuous, primary or
secondary (depends on the
frequency of venting)
None
Safe area
Seals and joints
Secondary
Pig receivers
Door
Primary
Sumps
Ventilated concrete slab/metal
grill
Continuous or Primary
Interceptors or coalescers
Ventilated concrete slab/metal
grill
Primary
Pumps
All welded piping
Flanges and valves
(2)
(1) In case of frequent seal failure in “normal operation”, should be considered as primary source of release
(2) In case of frequent failure in “normal operation”, should be considered as primary source of release.
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8.4 Procedure for continuous and primary grade releases
The hazard radii may be determined using the generic hazard radius values included in the
tables in Appendix A1; however, a more accurate value of hazard radius may be determined
using dispersion models when data for the equipment are available.
8.5 Procedure for secondary grade releases
The hazard radii may be determined using the generic hazard radius values included in the
tables in Appendix A2; however, a more accurate value of hazard radius may be determined
using dispersion models when data for the equipment are available.
8.6 Particular case of sheltered areas
There are many cases of natural ventilated situations where there is some restriction to free air
circulation:
 Some associated with an otherwise open area layout but where there is an obstruction in
the form of a wall, adjacent structure or open-sided roof
 Others where a partial restriction to natural air flow is in-built by design in the form of a
structure that has pierced openings or louvers to provide weather protection.
Note 1:
R1 is the hazard radius obtained from section 8.
Note 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.
Note 3:
S is the shortest distance from the source to the edge of the retaining wall.
Figure 2 - Extent of hazardous area around wall producing sheltered area
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9. Sizing and drawings of hazardous areas
The extent of hazardous areas shall be conducted in two steps:
 First the hazard radius around each potential release source is determined as per
section 8
 Then this hazard radius is used to set up the three dimensional envelope of the hazardous
area taking account of the type of zone, the ventilation in the area, the natural or artificial
obstacles in the gas path, and the buoyancy of the release.
Hazardous zones sizing is detailed in Appendix 6.
To draw the line between hazardous areas and non hazardous areas, the following rules apply:
 For skid mounted equipment (e.g. packages), it shall be assumed that secondary grade
release sources (see section 6.2.1) can be anywhere at the periphery of the equipment
skid. A detailed study of each single secondary grade release is not required. It is only in
case of difficulty that the exact location of the sources of release shall be considered. This
would require input from the equipment Vendor
 For non skid mounted equipment e.g. vessels, it shall be assumed that sources of
secondary grade release are located at a distance of 0.8 m from the equipment external
limits (e.g. vessel shell)
 The accurate location of each primary or continuous grade releases shall be considered
for drawing the hazardous areas they generate
 Two adjacent hazardous areas shall be merged in any point where their distance does not
exceed 3 m
 Generally a whole offshore deck or a whole onshore unit containing essentially
hydrocarbon processing or storage equipment should be classified as Zone 2 after
identifying the Zones 0 and 1 if any
 Extension of Zone contours at unit borders should be considered on a case by case basis.
10. Drilling rigs, equipment and well operations
See Appendix C for the classification of drilling rigs, equipment and well operations.
11. Internal combustion engines and fire heaters
Reference is also made to GS EP SAF 222, GS EP SAF 227.
11.1 Gas turbines
11.1.1 Main principles for classification
Gas turbines are potential sources of ignition and release.
Gas turbines shall not be installed in Zone 0 or Zone 1. As a consequence, gas turbines shall
drive equipment that is either a source of secondary grade release (hydrocarbon gas
compressor, oil pump) or not a source of release (alternator, water pump).
Gas turbines shall be installed in an enclosed area (called turbine enclosure) in order to reduce
the noise level and make the area safe by dilution ventilation.
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It may happen that the turbine enclosure, the driven equipment and all the auxiliaries are
enclosed in a bigger enclosure (called unit room).
The main justification of a unit room is to provide a safe environment to the driven equipment
(e.g. generator, compressor or pump) if it has to be installed in a hazardous area (e.g. offshore).
In cases where the driven equipment does not require a safe environment or is installed in a
safe area of the plant (e.g. onshore), the unit room is not mandatory.
For the classification of gas turbines, see Appendix 8.
11.1.2 Turbine enclosure principles
The turbine enclosure shall be provided with a ventilation system for cooling and dilution
purposes.
The turbine enclosure ventilation system shall be independent from the ventilation system of the
unit room, if any.
Turbine enclosure ventilation is ensured by a “main” ventilation system backed up by a “stand
by” ventilation system.
The stand by ventilation shall automatically start on loss of main ventilation.
Stand-by ventilation shall be supplied by an emergency power source independent from normal
power and shall be suitable for Zone 1.
After the turbine is shutdown, the auxiliary power source shall be capable of keeping the
ventilation running until hot surfaces have been cooled down below the auto-ignition
temperature of the gas/air mixtures that may be present in the enclosure.
Differential pressure shall be provided as applicable:
 Under pressure where the turbine enclosure is surrounded by a safe area
 Overpressure where the turbine enclosure is surrounded by a hazardous area.
In both cases (under pressure and overpressure), an alarm shall be initiated in the control room
if the differential pressure drops below 25 Pa (0.25 mbar).
The electrical equipment within the enclosure shall be certified for use in Zone 2 as a minimum.
The turbine enclosure shall be ventilated before energizing of any electrical equipment not
suitable for Zone 1. The purge ventilation shall be suitable for operation in Zone 1 and shall
ensure a minimum of 5 air changes.
11.1.3 Unit room principles
Any electrical equipment outside the turbine enclosure (power generator or auxiliaries) shall be
suitable for use in the type of hazardous area that prevails, either Zone 2 or safe area.
Where provided, the unit room of the totally enclosed type, shall be rendered safe as follows:
 A unit room containing a secondary fuel source and surrounded by an external hazardous
area shall be adequately ventilated
 A unit room containing a secondary fuel source and surrounded by an external safe area
shall be adequately ventilated and under-pressurised at a minimum of 25 Pa
 A unit room containing no fuel source and surrounded by an outside Zone 2 hazardous
area shall be maintained at a minimum overpressure of 25 Pa with respect to all
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surrounding classified areas with potential openings to the room including the turbine
enclosure itself
 In both cases, an alarm shall be provided in the control room if the differential pressure
drops below 25 Pa.
See Figures 8.1 to 8.3 in Appendix 8.
11.1.4 Hot surfaces in areas not provided with dilution ventilation (e.g. exhaust pipes)
When located in hazardous area, hot surfaces shall be thermally insulated. Their surface
temperature shall not exceed 80% of the ignition temperature (in °C) of any flammable gas
mixtures likely to be present. By default the surface temperature shall not exceed 200°C
(corresponding to ATEX requirement for T3 skin temperature). For more details refer to
API RP 2216.
11.2 Gas engines
Gas engines, as gas turbines, are considered as sources of ignition and release.
Gas engines:
 Shall not be installed in Zones 0 or 1
 Shall not be installed in a Zone 2 where a category G(ii) gas (e.g. Hydrogen, acetylene)
may be present
 Shall not be installed in areas where liquid hydrocarbon spillage or liquid mist may occur
and result in the release of vapours with an auto-ignition temperature lower than 135°C
 Should not be installed in a hazardous area.
Gas engines, their auxiliaries and driven equipment, shall in any case be adequately ventilated
even if their driven equipment does not constitute a fuel source.
Offshore, gas engines installed in Zone 2 shall be installed in an enclosure, protected by internal
overpressure and dilution ventilation which complies with the requirements of section 6.2.4.
The above requirement is not mandatory for onshore gas engines if requirement specified in
Appendix E1 are met.
For the classification of gas and liquid fuel engines, see Appendix 9.1.
11.3 Liquid fuel engines
Spark ignited gasoline-fuelled engines shall not be installed in hydrocarbon plants.
A Diesel fuel engine and its fuel circuit are not considered as a source of release, i.e. they do
not generate a hazardous area. The quantity of hydrocarbon vapour involved is small enough to
be disregarded. However, when fed with crude oil, a Diesel fuel engine shall be considered as a
source of release.
A Diesel fuel engine is a source of ignition, mainly due to its high skin temperature and the
possibility of spark emission.
Diesel engines:
 Shall not be installed in Zones 0 or 1
 Shall not be installed in a Zone 2 where a category G(ii) gas (e.g. Hydrogen, acetylene)
may be present
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 Shall not be installed in areas where liquid hydrocarbon spillage or liquid mist may occur
and result in the release of vapours with an auto-ignition temperature lower than 135°C
 Should not be installed in a hazardous area.
Diesel engines, their auxiliaries and driven equipment, shall in any case be adequately
ventilated even if their driven equipment does not constitute a fuel source.
Offshore, Diesel engines installed in Zone 2 shall conform to EN 1834-1or be installed in an
enclosure, protected by internal overpressure which complies with the requirements of section
6.2.4.
The above requirement is not mandatory for onshore Diesel engines if requirement specified in
Appendix 9.2 are met.
For the classification of Diesel engines, see Appendix 9.2.
11.4 Fired heaters
Fired heaters themselves do not generate hazardous area.
Main burners, igniters and pilots do not generate hazardous area.
As a consequence of what precedes, air intakes for natural draught fired heaters can be located
in the immediate vicinity of the burner, as long as they are outside the Zone 2 hazardous area
generated by the fuel or the process lines.
For the classification of fired heaters, see Appendix E3.
12. Accumulator batteries in buildings
12.1 Basics
With the exception of small capacity sealed batteries which are outside the scope of this
specification, accumulator batteries are regarded as primary sources of release: they release
hydrogen when they are being charged.
The purpose of ventilating a battery location or enclosure is to maintain the hydrogen
concentration below the 4% volume hydrogen Lower Flammability Limit (LFL) threshold. Battery
locations and enclosures are to be considered as safe from explosions when, by natural or
forced (artificial) ventilation, the concentration of hydrogen is kept below the LFL limit.
Particular attention shall be given to the fact that the gas emitted is lighter than air and will tend
to accumulate in any pockets at the top of the space. When batteries are arranged in two or
more tiers, all shelves shall have not less than 50 cm space, front and back, for circulation of air.
Reference is made to international standard IEC 61892-6 and IEC 61892-7 for the installation of
accumulator batteries in enclosures/buildings. This section 12 sets out the basic safety
requirements for the design of installations designed by or on behalf of Company.
Two types of accumulator batteries shall be considered:
 Open batteries which include recombination type or vented batteries
 Sealed batteries.
Refer to GS EP ELE 001 for the classification of accumulator batteries, and GS EP ELE 021 for
the electrical design of floating units. Refer also to GS EP HVA 100 for the dilution ventilation
criteria for accumulators.
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When dilution ventilation is achieved by artificial means, the battery charge shall be stopped on
loss of ventilation.
12.2 Location and hydrogen detection
Accumulator batteries and their charger may be located in the same cubicle only if this cubicle is
provided with natural or artificial dilution ventilation as per the requirements of this section.
The requirements set out in section 12.1 shall apply to all batteries liable to release flammable
gases. This section addresses additional requirements that depend on the capacity and
discharge voltage of the accumulator batteries.
 Sealed batteries: can be located in the same room as electrical equipment and no
hydrogen detection is required
 Open batteries shall be located in a dedicated battery room. The safety of personnel
handling the acid fluids associated with open batteries in this room shall be considered:
provision of an eye wash station. The fans in this battery room shall be suitable for
operation in Zone 1 for category G(ii) gases. Hydrogen detection shall be installed. On
hydrogen detection the battery charge shall be switched off (in order to stop hydrogen
release) and all ignition sources in the room shall be isolated, with the exception of the
electrical equipment certified for Zone 1 category G(ii) gases.
13. Hydrocarbon storage
For storage containing Category C or non-hazardous fluids on release, IP Code, Part 15,
section 3 shall be complied with. This is illustrated in sections 13.1, 13.2 and 13.3. As part of
this specification, IP Code, Part 15 recommendations shall apply even if the ambient
temperature exceeds 30°C.
13.1 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 depend on
whether the tank is pump or gravity fed. Refer to IP Code, Part 15, section 3 for more details.
13.2 Overhead, fixed roof storage tanks
For the classification of overhead, fixed roof storage tanks, see Appendix F1.
13.3 Overhead, floating roof storage tanks
For the classification of overhead, floating roof storage tanks, see Appendix F2.
13.4 LPG storage tanks
The extent and classification of hazardous areas around storage vessels containing Class 0
liquids (LPG) shall be based on French regulation, Arrêté du 9 novembre 1972
modifié au 28 avril 2008 for liquefied hydrocarbons stored under pressure at more than 0°C
ambient temperature (Category A2 under French classification).
For the classification of LPG storage tanks, see Appendix F3.
13.5 Refrigerated LPG storage
LPG stored at atmospheric pressure (below 0°C) is outside the scope of this specification. Refer
to the local regulations and standards prevailing in the country of application.
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13.6 LNG storage
NFPA 59A or more stringent national regulations shall be followed.
14. Miscellaneous
14.1 Laboratories
A laboratory contains potential sources of release such as hydrocarbon gas samples, and
vapours from heated hydrocarbon liquids. Some of the equipment used for hydrocarbon gas
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 leak sources may be toxic for
health. Adequate ventilation (refer to section 6.2.4.1.1) shall be implemented in laboratories to
ensure that they can be continuously and safely occupied by personnel.
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 into consideration the
hazards specific to each case. The following dilution rates apply only in the 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 are assessed:
 A laboratory handling flammable gases or liquids shall be provided with an exhaust fan
certified for Zone 1, which will achieve adequate ventilation
 A fume cupboard shall also be provided, with an exhaust fan certified for Zone 1 which will
achieve a ventilation rate of at least thirty air changes per hour.
Electrical equipment such as fixed lighting, sockets, junction boxes, lighting switches inside the
laboratory shall be certified for Zone 2 and defined as per GS EP ELE 079. The inventory of
flammable products in laboratories shall be minimised: flammable products other than the
minimum quantities necessary for the day-to-day work shall be stored outside the laboratory, in
suitable locations.
A laboratory should be a separate building, located in a non-hazardous area. If incorporated in a
larger building, it should be completely isolated from other parts of the building. For laboratories
where a pressure below that of the surrounding area is maintained, air-locks may be permitted
between the laboratory and the remainder of the building. The laboratory ventilation system
should be independent from the ventilation of the remainder of the building 10.
The doors of a laboratory should be self-closing and of a vapour-tight design.
For the classification of laboratories, see Appendix G1.
14.2 Analyser shelters
An analyser shelter or house is a specific closed room or building containing one or more
analysers for sampling of flammable fluids which are or may be connected to a process
installation together with electrical equipment and auxiliary devices (IEC 60079-16).
The design of analyser shelters shall comply with the requirements of IEC 60079-16, IEC 61285
and present specification. In particular:
 The analyser shelter shall be a separate building or shall be completely isolated from
other parts of the building
10
In certain cases, air inlets may be common to two ventilation systems.
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 If the analyser shelter is located in a hazardous area the ingress of the external
atmosphere into the shelter shall be prevented by an internal overpressure produced by
forced ventilation (refer to section 6.2.4.1.1)
 The analyser shelter containing ignition sources (e.g. electrical apparatus not suitable for
operation in Zone 2) and secondary grade of release sources shall be provided with
dilution ventilation (see section 6.2.4.1.1). The dilution ventilation shall ensure thirty air
changes per hour as a minimum (IP Code, Part 15).
Continuous or primary grade of release sources shall be vented. Sampling operations which
involve the intentional release of flammable substances shall be carried out in a suitable
location outside the shelter 11.Hydrocarbon vent lines shall be fitted with a flame arrester.
Air intakes for ventilation of analyser shelters should also be taken from outside the hazardous
area.
False ceilings and floors shall not be used in analyser shelters. Blowout panels should be
provided to minimise the consequences of an explosion.
14.3 Small storage of flammable products
This section addresses the case of portable containers with small volumes of flammable
products e.g. cylinders containing liquefied hydrocarbons or hydrocarbon gases under pressure
(acetylene, LPG). Storage locations shall be identified and designated on layouts during the
design of an installation for this equipment such that the hazard of ignition or explosion
associated with such storage be minimised.
For the classification of small storage of flammable products, see Appendix G2.
14.4 Loading and filling operations (road tanker, rail car, drum filling)
Refer to IP Code, Part 15, section 3.
14.5 Jetties (loading, unloading)
Refer to IP Code, Part 15, section 3.
14.6 Air intakes
Air intakes shall be located to prevent ingress of flammable gas or vapour in areas containing
ignition sources: e.g. air intakes to heating and ventilation systems and to combustion
chambers.
For the classification of air intakes, see Appendix G3.
14.7 Air exhausts
For the classification of air exhausts, see Appendix G4.
14.8 Chimneys and exhausts
Exhausts and chimneys releasing hot gases shall not be located in hazardous areas Zone 1 or
Zone 0.
11
If a primary source cannot be vented outside the shelter, dilution ventilation shall be provided even if there are no
ignition sources in the shelter (this shall require a derogation to this specification approved by Company and an
assessment of the dilution rate).
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They may be installed in Zone 2 hazardous areas only if their external skin temperature does
not exceed 200°C.
The external skin temperature limits as given above apply to all hot exhaust chimneys and
exhausts within the restricted areas of all petroleum installations (for the definition of the
restricted area refer to GS EP SAF 253).
For the classification of chimneys and exhausts, see Appendix G5.
14.9 Flares
Flares shall be installed in a non-hazardous area.
Flares shall be designed in accordance with GS EP SAF 253 and GS EP SAF 262.
14.10 Traffic
14.10.1 Roads and railways
For railways, refer to IP Code, Part 15.
In case requirements of the relevant section of Appendix 11.6 are not applicable, traffic
restrictions shall be implemented based on fixed gas detection which initiates visual and audible
alarms (design and risk mitigation measures shall be approved by Company). The safe
distances should be materialised by signs wherever an access road enters a hazardous area.
14.10.2 Helidecks, helipads and air strips
In case requirements of the relevant section of Appendix 11.6 are not applicable, traffic
restrictions and control procedures shall be implemented based on fixed gas detection which
initiates visual and audible alarms, presence of a HLO (Helicopter Landing Officer) or other
personnel qualified to authorise landing and take-off (design and risk mitigation measures shall
be approved by Company).
14.10.3 Boats
In case requirements of the relevant section of Appendix 11.6 are not applicable, traffic
restrictions shall be implemented based on fixed gas detection which initiates visual and audible
alarms (design and risk mitigation 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 of ignition.
14.11 Purging
Purging is the operation of passing a quantity of air through an enclosure and its associated
ducts in order to reduce to a safe level any concentration of flammable gas or vapour within the
enclosure and its associated ducts (from IEC 60079-16).
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 of sweeping
air shall be five times the total volume of the enclosure/premises. Purging shall be done with
air being totally free of flammable gas. This shall be established with flammable gas detectors,
fixed or portable. For the precautions specific to the operation of fired heaters refer to
GS EP SAF 227.
Care shall be taken that all areas have been effectively purged, particularly the confined areas
such as:
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 Pits, if heavier than air gas or vapour is present,
 Ceiling recesses if lighter than air gas or vapour is present
 Blind corners.
Flammable gas detectors shall be used to check all spots where gas is likely to accumulate.
14.12 Classification of enclosed buildings
The classification of the enclosed buildings shall be based on the rules defined in present
specification (refer to section 7.3), with due consideration for ventilation and pressurisation (as
per section 6.2.4) and in conformity with the relevant section of Appendix 11.
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Bibliography
Reference
Title
API Publ 4615
Emission Factors for Oil and Gas Production Operations
GS EP INS 101
Instrumentation engineering, supply and construction general
requirements
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Appendix 1
Appendix 1 Table of hazardous equipment
Hazardous
equipment
Tag
number
Description
Flammable fluid
Phase
MW
T
P
Flash
°C
bar(a)
Point
°C
Category
Area
Density
Auto
ignition
T°C
Explosive
limits
Type
Ventilation
Source of release
Nature
Grade
Flow
Classification
Zone
m3/h
% LFL
Hazard
radius
Remark
Gas
group
Temp
class
II A
T3
m
% UFL
V 110
Separator
Vapor
22
50
75
-
(5)
(1)
(2)
(2)
(3)
G(i)
L
502
4%
16%
Sheltered
Adequate
(1)
Range of MW to cover all situations.
(2)
Design pressure and design temperature or the most critical combination of P and T for hazardous releases.
(3)
For liquids only.
(4)
Only for vents that are covered by this specification (see Appendix A).
(5)
Vapours from a release are to be considered either heavier (H) or lighter than air (L).
Instrument
vent
2
-
2
1
(4)
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Appendix 2
Appendix 2 Area classification procedure
This procedure shall be followed at each stage of a development project and whenever there is
a modification to an existing installation.
Equipment
Grade of release - § 6.2.1
Zone ranking - § 6.2.2
Location - Open, sheltered, enclosed area - § 6.2.3, 6.2.4 & 7
Ventilation - § 6.2.4
Fluid category - § 8.1
Hazard radius - § 8.2 to 8.6 and Appendix A
Direct example method - § 10, 11, 12, 13 & 14 &
Appendices A & B give hazardous radius and
envelope at once
Hazardous area envelope - § 9 & Appendices A & B
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Appendix 3
Appendix 3 Procedure for assessing type and degree of ventilation
This method for assessing type and degree of ventilation applies in areas where sources of
flammable gases are present. Where toxic gases may be released, the ventilation rates given in
the figure are not relevant.
Determine openness of region to be classified by inspection of installation layout
Open Area
Enclosed Area
Open air conditions
(wind speed rarely
< 0,5 m/s and
frequently > 2 m/s
Are there any
significant obstacles
to natural wind
ventilation?
Does enclosed area contain internal source
of release?
No
No
Yes
Yes
If external source
exists is enclosure
pressurised to
> 25 Pa
Yes
Consider general or
local artificial
ventilation
No
Does ventilation system give
>12 air changes per hour?
No
Yes
Are there sufficient
air changes to give
dilution ventilation at
all ignition sources?
Yes
Open area:
Adequate
Natural
ventilation
Sheltered
or
obstructed
area:
Restricted
natural
ventilation
Over
pressurized
enclosed
area:
No
Enclosed
area:
Enclosed
area:
Enclosed
area:
Dilution
ventilation
Adequate
ventilation
Inadequate
ventilation
Non
hazardous
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Appendix 4
Appendix 4 Guidelines for the determination of the level of
ventilation of sheltered areas
Guidance from this table is broadly in line with API RP 505 (section 6.6, first edition 11/1997,
reaffirmed 11/2002).
The buildings described below are regarded as sheltered areas and may be used as weather
protection for equipment handling flammable fluids:
 Buildings where walls height is less than 2.5 m above ground, and the space under the
roof is adequately ventilated
 Buildings where the walls are provided with louvers or other types of slits purposely
designed for ensuring that natural ventilation will be adequate. As a minimum the louvers
should be present on three (out of the four) sides of the building: two strips of louvers,
each with a minimum vertical width of 1 m, shall run along the full length of the wall, one at
the top i.e. close to the roof/ceiling, the other at the bottom i.e. close to the floor/ground. It
should also be checked that these buildings offer a sufficient free area of inlet openings as
per the formula given in section 6.6.2.4.6 of API RP 505.
Walls (% surface) (2)
> 0 to 25
Top and bottom parts
> 25 to 50
> 50 to 75
> 75 to 100
Type of ventilation
Floor + ceiling
Adequate
Inadequate (3)
Inadequate
Inadequate
No floor (1) + ceiling
Adequate
Adequate
Inadequate
Inadequate
Floor, no ceiling
Adequate
Adequate
Adequate
Inadequate
No floor (1), no ceiling
Adequate
Adequate
Adequate
Adequate
(1)
Gratings are regarded as no floor
(2)
Plain walls (no louvers)
(3)
In some cases may be regarded as adequate.
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Appendix 5
Appendix 5 Determination of hazard radii (R1) values for equipment
For further guidance, see section 5 and Appendix C of IP Code, Part 15- 3rd Edition - July 2005.
All distances in this section are given in meters.
The maximum hazard radii for categories A, B, C and where appropriate G(i) and G(ii) are given
in the following tables.
Hazard radii (R1) are given using dispersion calculation methodology applied to particular fluid
compositions; however, a more accurate value of hazard radius may be determined using
dispersion models which take into consideration all the actual physical properties of the gas,
characteristics of the environment and conditions of release.
Gas dispersion calculations, if necessary, shall be carried out as per GS EP SAF 253, using
codes (computer programs) approved by Company.
Where appropriate, a risk based approach may be used to determine release hole size (see
Appendix 5.2).
The risk based methodology provides a means of adjusting release frequency and hence
hazard radii, to fit specific process scenarios.
5.1 Equipment/arrangements generally generating continuous or primary grade
releases
5.1.1 Drains and liquid sample points
This section applies to process equipment drains, instrument drains and liquid sample points
that discharge directly to atmosphere.
Drains and sample points should be graded based on the expected frequency of use.
If used more than once a day they should be regarded as primary sources as a minimum.
The following rules shall apply:
 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 an
appropriate disposal system such as a flare (refer to GS EP SAF 262 for the design of
hydrocarbon disposal systems, and GS EP SAF 228 for the design of closed drain
systems).
 Draining and sampling of Category B liquids directly to atmosphere should be avoided:
Wherever feasible, draining should be done to a closed drain system. Samples should be
taken in a sealed container designed to be connected to the drain point for the duration of
the sampling. There shall be a hazardous area resulting from the flanges and the valves
(see Appendix 5.2.3).
 Equipment drains (with the exception of the instrument drains) shall be designed as per
GS EP SAF 228. As such they are normally blinded and used only after the equipment is
isolated and depressurised. They generate a hazardous area as for valves and flanges
(see Appendix 5.2.3). If for any reasons equipment drains were not blinded they would
generate hazard radii as per Table 5.1 and in this case the possibility for draining category
B liquids shall be considered.
 Sampling of gases to an open system, i.e. with a release to atmosphere, shall generate a
hazard radius equivalent to an instrument vent (Appendix 5.1.4 applies).
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Appendix 5
 Sampling to a closed system with normally no release to atmosphere shall generate a
hazard radius as for flanges and valves (Appendix 5.2.3).
In all other cases, in particular the instrument drains and sampling of liquids to an open
system, Table A1 gives the maximum hazard radius for fluid categories A, B and C for the
“worst case” discharge pressure. The hazardous area will extend from the point of
draining/sampling.
Table 5.1 - Drains (not blinded) and liquid sample points
Fluid
category
Pressure
(Bar(a))
A
Hazard radius R1 (in m)
Diameter (2)
2 mm
Diameter (2)
5 mm
Diameter (2)
10 mm
Diameter (2)
20 mm
100
(3)
(3)
(3)
(3)
B
100
4
10
20
(1)
C
100
5
12
22
(1)
(1) For this diameter the radius exceeds 30 m. The size of the potential release is greater than normally considered
for area classification and should be avoided. Alternative design options should be considered such as a closed
collection system (refer to the text of this section), or a smaller diameter (e.g. a restriction).
(2) This is the diameter of the smallest item on drain or sample line i.e. line, valve or restriction orifice.
(3) Draining and sampling of Category A liquids directly to atmosphere shall not be allowed.
5.1.2 Tank vents (category C fluid)
Freely vented tanks will allow vapour /air mixtures to be released in normal operation.
Table 5.2 gives the hazard radii from the storage tank vent of a typical category C fluid:
Table 5.2- Tank vents
Hazard Radius R1 (in m)
3
Vent rate (Nm /h)
250
500
1000
2500
Vent Diameter (in mm)
50
80
100
250
2
3
3
4
2
3
4
5
2
3
4
5
3
4
6
6
5.1.3 Process vents
Permanent or occasional outflows of combustible vapour shall be collected and discharged
away from possible sources of ignition.
All vent flow-rates in this section are given at Normal conditions.
Material that could condense shall not be vented directly to atmosphere.
Vents shall be classified as continuous, primary or secondary grades of release depending on
the frequency of operation. Vents used frequently (e.g. daily) should be classified as primary
grade as a minimum.
For some vents there may be a small continuous or primary grade release flow (generating a
Zone 0 or 1) with a larger secondary grade release occasional flow (generating a Zone 2) for
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Appendix 5
example during abnormal or emergency operation. In this case, the Zone 0 or 1 hazardous area
shall be surrounded by a larger Zone 2 area defined by the larger flow (refer to Appendix 6).
The hazard radii for process vents have been calculated for a matrix of venting rates and vent
diameters and are given in Table 5.3.
The peak venting flow rate of the release is to be considered for determining the hazard radius.
These recommended distances are based on unrestricted upward discharge and dispersion of
vapour without condensation.
Table 5.3 - Process vents
Hazard Radius R1 (in m)
Vapor Emission rate
(Nm3/h)
Vent diameter (mm)
50
100
250
3
5
6
3
5
6
250(2)
3
5
6
(2)
4
5
7
5
5
9
10
(1) (3)
100
500
(1) (2)
1000
(2)
(1) For vents with flow rates kept below 100 Nm3/h and where the velocity of all the releases are above 150 m/s, the
distance to LFL given in ISO 23251 / API STD 521 (section 6.3 fifth edition 01/2007) should be adopted.
3
(2) For vents with flow rates exceeding 200 Nm /h a dispersion calculation shall be carried out to check if the
distances of this table are adequate (gas dispersion calculations shall be carried out as per GS EP SAF 253). A
dispersion calculation is also recommended for vents with flow rates exceeding 100 Nm3/h.
(3) Gaseous sample points should be designed so that the flow rate is less than 10 Nm3/h at ambient conditions. It
may be necessary to fit a flow restrictor on high pressure systems.
5.1.4 Instrument vents
The maximum hazard radii from vents on instrument systems shall be based on Table 5.4 which
gives the maximum hazard radius for fluid categories A, B, C, G(i) and G(ii) for the “worst case”
discharge pressure of 100 bar(a).
Table 5.4 - Instrument vents
Fluid
category
Hazard radius R1 (in m)
Diameter
1 mm
Diameter
2 mm
Diameter
5 mm
A
2.5
4
9
B
2
4
9
C
2.5
4.5
9
G(i)
<1
<1
1
G(ii)
1
1
2
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Appendix 5
5.1.5 Sumps in oily water treatments units
The typical layout of a sump is shown in Figure 5.1.
The hazardous area above ground and outside the sump walls should be drawn as shown from
the periphery of the sump using the appropriate hazard radius obtained from Table 5.5 in cases
when it can be assumed that entry of only Category C fluids can occur.
Generally this assumption can be made only in the case of storage and tank areas, including
installations and depots.
This area should be classified as Zone 1 or Zone 2 depending on whether the source is primary
or secondary grade of release.
When there is a possibility that hot material could enter the sump in sufficient quantity to
produce appreciable quantities of gas, or that Category A or B material could inadvertently
enter, then a hazard radius of 15 m should be used with an increased vertical distance of 3 m.
Note 1:
The Zone 2 is applicable where there is a possibility of a secondary grade release and the hazard radius
R1, for the primary grade release is less than 15 m.
Note 2:
Dimension from Table 5.5.
Note 3:
h depends on the temperature of release and the volatility of the material released. For Category C fluids
up to 50°C, h is nominally 1 m; for volatile fluids or at elevated temperatures, a nominal height, h, of at
least 3 m should be applied. However it is recommended that this height is verified by calculation.
Note 4:
For a secondary grade release, the area shown as Zones 0 and 1 would be Zones 1 and 2 respectively.
Figure 5.1 - Open sump - Zoning shown for primary grade source
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Appendix 5
Table 5.5 - Sumps (all distances in meters)
L
Less than 5
5 to less than 10
10 or greater
R1
3
7.5
15
Note 1:
This table should be used only for Category C liquids.
Note 2:
L is width of the sump. The hazardous area should extent from the edge of the pool.
5.1.6 Pig receivers and launchers
Pig receivers and launchers are likely to be opened frequently and should normally be regarded
as sources of primary grade release. The hazardous area should be classified as Zone 1.
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 the drain or
vent systems. A pressure gauge shall be provided with a range suitable for checking zero
pressure before opening the door.
On this basis, the doors of the pig traps should be regarded as sources with a hazard radius
(Zone 1) of 3 m around the trap door.
This distance may be reduced to 1.5 m if the equipment is purged with nitrogen and water
washed through before opening.
On pig receivers and launchers without an interlock between the door mechanism and the drain
or vent systems, there should be an additional Zone 2 area from the trap door with a hazard
radius of 7.5 m.
Vents and drains should discharge to a safe location and the hazard radius they generate shall
be estimated using Appendices 5.1, 2, 3 & 4.
5.2 Equipment/arrangements generally generating secondary grade releases
5.2.1 Pumps
LNG pumps, for which motor and pump are submerged in a “can” or in a storage tank, do not
generate a hazardous area.
Sources of release on pumps include their seals, vents, drains, valves, piping flanges and
filter/strainers.
They are normally all secondary grade sources because flanges are broken, filters opened and
vents and drains operated infrequently. Likewise a seal failure resulting in an appreciable
release of liquid is unlikely. Should any of these events be part of “normal operation” (as defined
in section 3) or occur frequently then the item should be regarded as an individual primary grade
source.
The hazardous area generated by the pump should be drawn from the periphery of the pump.
For this purpose the term "pump" should include the associated equipment which can be source
of release.
Vents and drains which are not blinded in normal operation generate their own hazardous
areas, independently from the pump they are associated with.
For the sake of simplification, a uniform hazard radius of 7.5 m shall be considered for high
integrity pumps, irrespective of fluid category. This hazard radius shall be used for discharge
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Appendix 5
pressures up to 100 bar(a). For higher pressure releases, appropriate dispersion calculations
shall be carried out.
The term "high integrity" refers to a pump for which the design reduces significantly the
probability of release. The pumps of glandless type, or fitted with a double mechanical seal
system with a means of detecting leaks through the inner seal should be regarded as “high
integrity pumps”.
For non high integrity pumps (single seal with or without throttle bush), refer to IP Code, Part 15
3rd edition -Appendix C - Calculation of hazard radii.
5.2.2 Compressors
Sources of release on compressors include seals, glands and joints. The hazardous area
should be drawn from the periphery of the unit.
Vents and drains which are not blinded in normal operation generate their own hazardous
areas, independently from the compressor they are associated with.
For the sake of simplification, a uniform hazard radius of 7.5 m shall be considered for both G(i)
and G(ii) fluid categories handled by high integrity (dry gas seals) compressors. This hazard
radius shall be used for discharge pressures up to 100 bar(a). For higher pressure releases,
appropriate dispersion calculations shall be carried out.
For non dry gas seals reciprocating compressors, a hazard radius of 15 m shall be applied for
both G(i) and G(ii) fluid categories. The radius may be reduced to 7.5 m for pressures below 20
bara and shaft diameters of 50 mm or less.
For non dry gas seals centrifugal compressors (purged labyrinth or floating ring seals), refer to
IP Code, Part 15 3rd edition - Appendix C.
5.2.3 Piping, instrument tubing, flanges and valves
Hazard radii are from the periphery of flanges and valves in piping and instrument tubing.
All-welded (without fittings such as valves, instruments and flanges) piping and instrument
tubing designed and constructed to Company specifications should not be considered as
sources of release.
Flanges routinely broken in normal operation e.g. with a frequency greater than once a week,
should be considered as primary grades of releases.
All valves shall be considered as sources of release.
Blow out of part of a gasket has not been considered since it is regarded as an incident with a
low probability that is considered in consequence analysis for the determination of fire zones
(refer to GS EP SAF 253).
For the sake of simplification, a uniform hazard radius of 3 m shall be considered for fluid
categories A, B, C, G(i) and G(ii). This hazard radius shall be used for discharge pressures up
to 100 bar(a). For higher pressure releases, appropriate dispersion calculations shall be carried
out.
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Appendix 6
Appendix 6 Sizing of hazardous zones
The relationship between the hazard radius R1 and the full 3-dimensional envelope of the
hazard Zone is determined using the following figure:
(c) Releases where H > R1 +1
Figure 6.1 - Shape factors for pressurised releases
The shape factor depends upon the height and orientation of the release and the hazard radius.
The key features are:
 Releases below (H) of 1 m are influenced by the ground and have a hazard radius R2
 Releases above 1 m, but at heights below the hazard radius R1 + 1 m are influenced by
the ground if the release is directed downward and passes below 1 m
 Releases at height above the hazard radius R1 + 1 m are independent of the ground.
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Appendix 6
The ground effect R2 can be estimated from the hazard radius R1, directly using Table 6.1:
Table 6.1 - Hazard Radii at ground level R2
Fluid
category
Release
Pressure
(bara)
Hazard radius R2 (m)
Release hole diameter
1 mm
2 mm
5 mm
10 mm
5
10
50
100
2
2.5
3
3
4
4.5
5.5
6
16
20
20
20
(1)
5
10
50
100
2
2.5
2.5
3
4
4
5
5
14
16
17
17
(1)
5
10
50
100
2.5
2.5
3
3
4
4.5
5.5
6
20
21
21
21
(1)
G(i)
5
10
50
100
<1
<1
<1
1
<1
<1
1.5
2
1
1.5
3.5
5
2
3
7
11
G(ii)
5
10
50
100
<1
<1
1
2
<1
1
2
3
2
2.5
6
8
4
5
11
14
A
B
C
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1)
(1) For this diameter the radius exceeds 30 m. The size of the potential release is greater than normally considered
for area classification and should be avoided.
Note: The hazard radius determined at ground level (R2) shall be consistent with the radii defined before in Appendix
5: in any case, R2 shall be higher (or equal) to the hazard radius (R1).
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Appendix 6
Note 1:
Vent pipe opening should have at least R1 metres of free space around it in all directions to allow dispersal
of vapour, and be away from open windows, doors, etc.
Note 2:
To avoid placing a working platform in a Zone 1 area, h should be measured from any working level within
R1 metres of the vent stack.
Note 3:
In (c), R1 for Zone 1 should be for the primary grade release and R1 for Zone 2 should be for the
secondary grade release.
Figure 6.2 - Typical hazardous areas around vents
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Appendix 7
Appendix 7 Drilling rigs, equipment and well operations
7.1 Foreword
This section sets out onshore and offshore Company requirements for the area classification of:
 Drilling, workover and pulling operations on Non Live Wells
 Well servicing operations on Live Wells
 Wellheads in production operations.
It does not cover the production equipment located downstream of the wellheads.
7.2 Drilling, workover and pulling operations on Non Live Wells
Classification of areas for drilling, workover and pulling operations on Non Live Wells, on single
and clustered wells for an onshore or offshore location is shown on Figures 7.1 to 7.4, based on
the potential sources of hydrocarbon release at:
 The rig substructure (from rig floor to main platform deck - offshore - or ground level onshore-) in which the bell nipple, diverter and blow out preventers are located
 The wellhead area down to the cellar
 The upper works of the rig, above the rig floor
 The circulating surface mud system
 Tanks, flanges, vents or drains
 Gas vents from any of the above.
In an open area a spherical hazardous area (Zone 1) of 3 m radius shall extend from the centre
of the bell-nipple.
A hazardous area (Zone 2) surrounding the spherical 3 m radius hazardous area shall extend
7.5 m vertically and horizontally from the centre of the bell nipple and down to ground or sea
level. When a solid deck or platform is more than 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 on the
BOP, its stack and the riser assembly will conservatively be within the hazardous area shown
on Figures 7.1 to 7.4. Alternatively, they can be determined as per the relevant sections of
Appendices 5 and 6.
The occurrence of a blow-out or a ‘kick’ is not considered in this area classification specification.
Kicks are regarded by Company as rare and accidental events because mud degassing
equipment, continuous monitoring of pit level, hydrocarbon gases level and gas extraction is
mandatory on its drilling and work-over rigs.
On drilling installations, the "dog house" and all other technical facilities shall be classified as
Zone 2.
Generally, sheltered areas shall generate a hazardous area extending 3 m outside the shelter
(beyond the 7.5 m from the bell-nipple if necessary). Any apertures from an enclosed area
containing a source of release should be regarded as a secondary grade source and the
resulting hazardous area should be drawn from the apertures.
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Appendix 7
If the derrick is enclosed, and if it contains a secondary grade source of release (e.g. flanges,
valves in hydrocarbon pipes) the internal space shall be classified as Zone 1, with a Zone 2
extending 3 m outside the enclosure.
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 Zone 1 with a
Zone 2 extending 3 m outside the enclosure or 7.5 m from the bell-nipple whichever is greater.
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.
7.3 Surface mud systems
Open tanks should be regarded as sumps. The larger of the distances indicated in Appendices
5 and 6 and those defined in this chapter shall be used to define the hazardous zones.
The surface mud system includes the mud circulating pumps, the shale shaker area and the
setting tank, together with any mud degassing equipment.
The possibility of the mud being itself hazardous shall be considered. A mud shall be
considered hazardous whenever its temperature may reach 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 operating temperature of
the mud.
Mud pumps and manifolds in the surface mud system should normally not be regarded as
sources of release.
Typical hazardous areas around mud tanks and shale shakers located in open areas are shown
on Figures 7.5 and 7.6.
In an open area, the space within the mud tank walls shall be classified Zone 1 with a Zone 2
area outside (See Figure 7.5).
In an open area, a shale shaker should generate a horizontal Zone 1 area and an additional
Zone 2 extending from Zone 1 (See Figure 7.6).
When a shale shaker or a mud tank is located in an enclosure with adequate artificial
ventilation, the enclosure should also be classified as Zone 1 extending 3 m from any opening.
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 m from any openings in the
enclosure.
7.4 Rig gas vent
Primary grade sources of release such as vent line outlets shall not be allowed within an
enclosed area (derrick or the shielded portion of a derrick).
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Appendix 7
Vents should not be released directly to atmosphere i.e. they should be collected in a purposely
designed system discharging at a safe location (away from ignition sources, refer to Appendices
5 and 6).
The gas vent outlet of the main mud system shall 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 the hazardous
area should be based on the recommendations on process vents given in Appendices 5 and 6.
When this information is not available, the hazardous area shall extend 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 vent shall be
considered hazardous.
The gas vent should normally be considered as a source of primary grade release.
7.5 Well servicing (Wire-line - Coiled tubing - Snubbing) operations on Live
Wells
Area classification for well servicing operations (wire-line - coiled tubing - snubbing) on Live
Wells is shown on Figures 7.7 and 7.8 based on the potential sources of hydrocarbon release
on surface and at the source point of release.
7.6 Wellheads in production operation
Area Classification for production operations are shown on Figures 7.9 and 7.10.
For an onshore well, the ground cellar is classified as Zone 1 for all servicing and production
operations.
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Appendix 7
7,5m
TOP OF WIND BREAK
RIG FLOOR
BELL- NIPPLE
(RIG FLOOR LEVEL)
FLOWLINE
BOP
Main deck
3m
HP RISER
WELLHEAD
W
9m or
to sea level
Cellar deck
Sea level
7,5m
ZONE 1
ZONE 2
Note:
For an eruptive well, the Zone 2 becomes a Zone 1 and it shall be surrounded horizontally by an additional
Zone 2 of 7.5 m starting from the edge of Zone 1.
Figure 7.1 - Offshore single wellhead during operations on Non Live Wells
(drilling, workover and pulling)
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Appendix 7
TOP OF WIND BREAK
7,5m
7,5m
7,5m
RIG FLOOR
BOP
Main deck
3m
3m
HP RISER
WELLHEAD
X
X
W
W
X
X
W
W
9m or
to sea level
Cellar deck
X
X
Sea level
7,5m
7,5m
1,5m to 3m between wells
ZONE 1
ZONE 2
MAXIMUM LIMIT OF THE ENVELOPE
CONSIDERING ALL THE WELLHEADS
Note:
For an eruptive well, the Zone 2 becomes a Zone 1 and it shall be surrounded horizontally by an additional
Zone 2 of 7.5 m starting from the edge of Zone 1.
Figure 7.2 - Offshore cluster wellhead during operations on Non Live Wells
(drilling, workover and pulling
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Appendix 7
7,5m
TOP OF WIND BREAK
7,5m
7,5m
BELL-NIPPLE
(RIG FLOOR LEVEL)
FLOWLINE
3m
BOP
Ground level
W
WELLHEAD
L
R1
ZONE 1
ZONE 2
Note: For an eruptive well, the Zone 2 becomes a Zone 1 and it shall be surrounded horizontally by an additional
Zone 2 of 7.5 m starting from the edge of Zone 1.
Equivalent diameter of well cellar
L(m)
Hazard radius
R1(m)
less than 10
7.5
10 or greater
15
Figure 7.3 - Onshore single wellhead in operations on Non Live Wells
(drilling, workover and pulling)
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Appendix 7
TOP OF WIND BREAK
7,5m
7,5m
7,5m
RIG FLOOR
7,5m
3m
X MAS TREE
X
X
X
X
W
W
L
BOP
W
L
Ground
level
X
X
W
L
L
WELLHEAD
R1
3m to 5m
3m to 5m
between wells
3m to 5m
R1
ZONE 1
ZONE 2
MAXIMUM LIMIT OF THE ENVELOPE
CONSIDERING ALL THE WELLHEADS
Note:
For an eruptive well, the Zone 2 becomes a Zone 1 and it shall be surrounded horizontally by an additional
Zone 2 of 7.5 m starting from the edge of Zone 1.
Equivalent diameter of well cellar
L(m)
Hazard radius
R1(m)
less than 10
7.5
10 or greater
15
Figure 7.4 - Onshore cluster wellhead in operations on Non Live Wells
(drilling, workover and pulling)
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Appendix 7
3m
Drilling mud
Ground level
L
R1
Figure 7.5 - Hazardous area around mud tanks
3m
Ground level
or Deck level
15m
L
R1
Equivalent diameter of pool
L(m)
Hazard radius
R1(m)
ZONE 1
ZONE 2
less than 10
7.5
10 or greater
15
Figure 7.6 - Hazardous area around a shale-shaker in an open area
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7,5m
Appendix 7
STUFFING BOX
BOP
Main deck
X MAS TREE
WELLHEAD
W
9m or
to sea level
Cellar deck
X
X
Sea level
7,5m
7,5m
ZONE 1
ZONE 2
Note 1:
For a non eruptive well, the Zone 1 generated by the wellhead and the well service equipment becomes a
Zone 2 and the Zone 2 becomes a safe area.
Note 2:
Source point of release is at stuffing box for wireline, head injection for coiled tubing and bowl stripper for
snubbing.
Figure 7.7 - Offshore wellhead during well servicing operations on Live Wells
(wireline-coiled tubing - snubbing)
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Appendix 7
7,5m
7,5m
7,5m
STUFFING BOX
BOP
7,5m
X MAS TREE
X
X
Ground
level
W
WELLHEAD
R1
L
R1
ZONE 1
ZONE 2
Note 1:
For a non eruptive well, the Zone 1 generated by the wellhead and the well service equipment becomes a
Zone 2 and the Zone 2 becomes a safe area.
Note 2:
Source point of release is at stuffing box for wireline, head injection for coiled tubing and bowl stripper for
snubbing.
Equivalent diameter of well cellar
L(m)
Hazard radius
R1(m)
less than 10
7.5
10 or greater
15
Figure 7.8 - Onshore wellhead during well servicing operations on Live Wells
(wireline - coiled tubing - snubbing)
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Main deck
7,5m
X MAS TREE
Cellar deck
7,5m or up to
fight deck
Appendix 7
X
X
WELLHEAD
9m or
to sea level
W
Sea level
7,5m
Figure 7.9 - Offshore wellhead - Production or injection (open area)
Ground
level
X MAS TREE
X
X
W
WELLHEAD
R1
L
ZONE 1
ZONE 2
Note:
In the case of a beam-pumped well, the release source to be considered is the stuffing box.
Equivalent diameter of well cellar
L(m)
Hazard radius
R1(m)
less than 10
7.5
10 or greater
15
Figure 7.10 - Onshore wellhead - Production or injection (open area)
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Appendix 8
Appendix 8 Gas turbines
This section sets out the Company specific requirements for the classification of gas turbines.
The following figures (Figures 8.1 to 8.3) give details for each typical case:
 Ventilation and pressurisation requirements
 Hazard radii around the vents outlets.
Figure 8.1
 Gas turbine driving a compressor without a unit room
 Gas turbine driving a generator without a unit room.
Figure 8.2
 Gas turbine driving a compressor in a unit room within a Zone 2 hazardous area
 Gas turbine driving a generator in a unit room within a Zone 2 hazardous area.
Figure 8.3
 Gas turbine driving a compressor in a unit room within a safe area
 Gas turbine driving a generator in a unit room within a safe area.
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Appendix 8
Ø=3m
COMBUSTION
AIR
d>5 m
h>2 m
Dilution ventilation>90 Vol./h
P = Patm + 25 Pa
Safe area
VENTILATION
AIR
d>2 m
COMPRESSOR
Turbine enclosure
P = Patm
Zone 2 hazardous area
Ø=3m
COMBUSTION
AIR
d>5 m
Dilution ventilation>90 Vol./h
VENTILATION
AIR
P = Patm - 25 Pa
Safe area
GENERATOR
Turbine enclosure
P = Patm
Safe area
Figure 8.1 - Turbine enclosure without unit room
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General Specification
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GS EP SAF 216
Appendix 8
Ø=3m
d> 5 m
h>2 m
COMBUSTION
AIR
Dilution ventilation>90 Vol./h
TURBINE ENCL.
VENTILATION
AIR
P=Patm + epsilon+25 Pa
Safe area
d>2 m
UNIT ROOM
VENTILATION
AIR
d>2 m
COMPRESSOR
Turbine enclosure
Adequate ventilation > 12 Vol./h
P = Patm + epsilon
Zone 2
hazardous area
Unit Room
P = Patm
Zone 2 hazardous area
Ø=3m
d> 5 m
h>2 m
COMBUSTION
AIR
Dilution ventilation>90 Vol./h
TURBINE ENCL.
VENTILATION
AIR
P < or = Patm
Safe area
d>2 m
UNIT ROOM
VENTILATION
AIR
d>2 m
GENERATOR
Turbine enclosure
Ventilation > 6 Vol./h
Unit Room
P = Patm + 25 Pa
P = Patm
safe area
Zone 2 hazardous area
Figure 8.2 - Turbine enclosure within a unit room in a hazardous area
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General Specification
Rev : 05
GS EP SAF 216
Appendix 8
Ø=3m
d> 5 m
Ø=3m
COMBUSTION
AIR
TURBINE ENCL.
VENTILATION
AIR
Dilution ventilation>90 Vol./h
P > or = Patm
Safe area
COMPRESSOR
UNIT ROOM
VENTILATION
AIR
Turbine enclosure
Adequate ventilation 12Vol./h
P = Patm - 25 Pa
Unit Room
Zone 2 hazardous area
P = Patm
safe area
Ø=3m
d> 5 m
COMBUSTION
AIR
TURBINE ENCL.
VENTILATION
AIR
Dilution ventilation>90 Vol./h
P=Patm + epsilon-25 Pa
Safe area
GENERATOR
UNIT ROOM
VENTILATION
AIR
Turbine enclosure
Ventilation > 6 Vol./h
P = Patm + epsilon
P = Patm
Unit Room
safe area
safe area
Figure 8.3 - Turbine enclosure within a unit room in a safe area
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Exploration & Production
General Specification
GS EP SAF 216
Date : 01/2011
Rev : 05
Appendix 9
Appendix 9 Gas/liquid fuel engines and heaters
9.1 Gas engines
Offshore, gas engines installed in Zone 2 shall be installed in a pressurised enclosure with
dilution ventilation in accordance with the requirements of section 6.2.4.
Onshore, a gas engine, not installed in an overpressurised enclosure fitted with dilution
ventilation, can be installed in a Zone 2 providing the unit comprising the engine, its driven
equipment and their “auxiliaries” 12 is installed at a safe distance “d” of other units, in line with
requirements of GS EP SAF 021 and GS EP SAF 253.
Ignition sources should be made suitable for Zone 2.
9.2 Diesel engines
Offshore, Diesel engines installed in Zone 2 shall conform to EN 1834-1 or be installed in an
enclosure, protected by internal overpressure which complies with the requirements of section
6.2.4.
Onshore, a Diesel engine, not in conformity with EN 1834-1 and not installed in an
overpressurised enclosure, can be installed in a Zone 2 providing the unit comprising the
engine, its driven equipment and their “auxiliaries” 13 is installed at a safe distance “d” of other
units, in line with requirements of GS EP SAF 021 and GS EP SAF 253.
Ignition sources should be made suitable for Zone 2.
Process vessels shared by several Diesel engine driven compressors or pumps shall be
considered as a separate unit, distinct from the Diesel engines' and associated driven
equipment.
All Diesel engines and driven equipment shall be grouped together in one functional unit
separated from other units (process or utility) by minimum distances as per GS EP SAF 021.
Diesel engines in hazardous areas driving different type of equipment (e.g. compressors and
pumps) shall be grouped in different units segregated as per GS EP SAF 021.
12
Process facilities and technical rooms shared by several gas engines such as the fuel gas treatment unit are not
regarded as “auxiliary” and shall be installed at the distance specified below. Several engine driven packages of
the same type and function may be grouped in the same unit (refer to Figure 9.1).
13
Process facilities and technical rooms shared by several Diesel engines such as the fuel gas treatment unit are not
regarded as “auxiliary” and shall be installed at the distance specified below. Several engine driven packages of
the same type and function may be grouped in the same unit (refer to Figure 9.1).
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General Specification
Rev : 05
GS EP SAF 216
a boundary e
ncroach
s are
ou
ing
rd
t
on
Ha
z
a
Appendix 9
oe
ng
in
es
ENGINE
ENGINE
d
ENGINE
Unit edge
Unit edge
Figure 9.1 - Diesel and gas engines in a hazardous area onshore
9.3 Fired heaters
The extent and classification of hazardous areas around fired heaters and other fuelled utilities
shall be based upon the following principles:
 Any fuel gas line (s) and appurtenances (flanges, filters, valves, instrument tapping) shall
generate a Zone 2 with a radius of 3 m
 Any valve, set of flanges on the liquid-fuel network shall generate a Zone 2 of a radius of
3m
 Main burners, igniters and pilots shall be located at least 3 metres off of the closest joint
pertaining to the fuel gas system and from any process flanges
 Any equipment within a radius of 1.5 metre around the main burners, igniters and pilots
shall be suitable for use in Zone 2.
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GS EP SAF 216
Date : 01/2011
Rev : 05
Appendix 9
Non hazardous area but material suitable for Zone 2 required
Figure 9.2 - Hazardous areas around fired heaters
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General Specification
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GS EP SAF 216
Appendix 10
Appendix 10 Hydrocarbon storage
10.1 Overhead, fixed roof storage tanks
For fixed roof storage tanks containing liquids of Classes I, II (2) or III (2) that are normally of
Category C on release, the extent and classification of the hazardous areas shall be as shown
below:
Zon
3m
e1
2m
Zone 0
3m
Zone 2
Pit, if any, Zone 1
Figure 10.1 - Fixed roof storage tank (Fluid class I, II (2) and 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-point of
heavy fuels or bitumen in heated storage is not reliable, it is recommended to classify the ullage
space as Zone 0, with a small Zone 1 around roof vents and openings.
Zone 1
1m
Zone 0
Figure 10.2 - Fixed roof storage tank (Fluid class II (1), III (1) or unclassified)
10.2 Overhead, floating roof tank (Category C on release)
For floating roof storage tanks containing liquids of Classes I, II(2) or III(2) that are normally of
Category C on release, the extent and classification of hazardous areas shall be as shown
below:
2m
Zone 1
2m
Zone 2
Pit, if any, Zone 1
Figure 10.3 - Floating roof storage tank (Fluid class I, II(2) or III(2))
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General Specification
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GS EP SAF 216
Appendix 10
PSV discharge
7.5 m
10.3 LPG storage stored under pressure
Zone 2
5m
assumed to be
Zone 1
at this location
7.5 m
7.5 m
7.5 m
Storage vessel
Capacity < 200 m3
Ground
Figure 10.4 - LPG storage vessel < 200 m3
assumed to be
15
m
PSV discharge
at this location
Storage vessel
Capacity > 200 m3
Zone 2
Zone 1
10 m
0.6 m
Ground
Figure 10.5 - LPG Storage vessel > 200 m3
Notes on figures 10.4 and 10.5:

The figures are the cross-sections of the LPG storage vessel which contain the Pressure Safety Valve (PSV)
discharge point. The Zone 1 envelope is a sphere centred on the PSV discharge point, and the Zone 2
envelope is made of cylinders with a vertical axis containing the PSV discharge point

The size and shape of the hazardous areas are determined by the location of the storage vessel and the
volume of the vessel containing LPG under pressure (less or more than 200 m3). They do not depend on the
shape of the storage vessel (sphere, cylinder)

The hazardous areas generated by piping connections, sample points, instrument vents and all other
equipment shall be determined as per the standard rules given in Appendices 5 and 6
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GS EP SAF 216
Rev: 05
Appendix 11
Appendix 11 Miscellaneous
11.1 Laboratories
The hazardous areas generated by the doors (vapour-tight or not) and the fan exhausts shall
extend to 3 m as shown in Figure 11.1.
3m
Self-closing airtight door
Laboratory
ZONE 2
3m
Adequate
ventilation
Exhaust fan creating under pressure
Figure 11.1 - Laboratories
11.2 Small storage of flammable products
Since a leak from properly designed containers can only be accidental, such containers should
generate a hazardous area Zone 2, extending X m from the envelope of the containers(s). X
should be determined as per Table 5.9 of Appendix 5.2 - Flanges and valves.
11.3 Air intakes
Air intakes shall be located at least 2 m away from the border of any hazardous area.
11.4 Air exhausts
Air exhausts from a classified enclosed area should generate a hazardous area of 3 m radius
with the same classification as the enclosed area.
11.5 Chimneys and exhausts
Chimney outlets shall be at least 2 m away from the border of any hazardous area Zone 2 and 9
m away from the border of any hazardous areas Zone 1 or 0 14.
11.6 Traffic
11.6.1
Roads and railways
The main roads of a plant (peripheral roads) shall be kept no less than 2 m away from the
border of any Zone 2 and 9 m away from the border of any Zone 1 and Zone 0.
11.6.2
Helidecks, helipads and air strips
Any point of these areas as well as any area being part of a helicopter/plane approach Zone
shall be no less than 2 m away from the border of any Zone 2 and 9 m away from the border of
any Zone 1 and Zone 0.
11.6.3
Boats
The boat landing and/or the mooring facilities shall be such that tugs or supply boats are
kept 2 m away from the border of any hazardous area Zone 2 and 9 m away from the border of
any hazardous areas Zone 1 and 0.
14
Vents from turbine lube oil tanks, although generating a Zone 1 hazardous area, may exit into the outlet of the turbine main
exhaust chimney. This standard design is regarded as safe considering the risk specific to this situation.
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GS EP SAF 216
Rev: 05
Appendix 11
11.7 Enclosed buildings
This section is intended to provide examples of the application of these rules, as shown in
Figure 11.2.
Note 1:
Zone classification and extent to be defined according Appendices 5 and 6 assuming the door is wide
open. Installation of self-closing airtight door is recommended.
Figure 11.2 - Classification of enclosed buildings
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