Hazardous Guide

Hazardous Guide
International
Reference Guide
to Hazardous Areas
1
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
HAZARDOUS AREA STANDARDS AND APPROVALS
There are different standards used for hazardous areas and electrical equipment designed for use in those
environments, depending upon where in the world they are to be used. In Europe EN standards are used to
gain compliance with the ATEX directive. In the USA the standard is NEC (National Electric Code), with a
variant called CEC (Canadian Electric Code) used in Canada. In addition some countries have their own
approval standards (e.g. GOST for Russia and the former Soviet States, TISI for Thailand, etc), however these
are often based on IEC standards.
To simplify matters an attempt is being made to harmonise all major standards for use in the IECEx scheme.
The aim of the IECEx Scheme is to facilitate international trade in electrical equipment intended for use in
explosive atmospheres (Ex equipment) by eliminating the need for multiple national certification while
preserving an appropriate level of safety.
Whilst the standards used in Europe and America are intended to achieve the safe installation and operation
of electrical equipment in hazardous areas, they are different in principles, classification and approach.
The purpose of the following guide is to detail some of the differences in the two approaches and to use a
step-by-step process to select the correct type of luminaire or other electrical equipment for use in a
hazardous area.
THE CLASSIFICATION OF HAZARDOUS AREAS INTO ZONES IS GIVEN FOR GAS MIXTURES, IN IEC OR
EN 60079-10 AND SELECTION IN IEC OR EN 60079-14.
FOR COMBUSTIBLE DUST HAZARDS THE EUROPEAN STANDARDS ARE EN 61241-10 AND EN 61241-14.
THE INFORMATION FOLLOWING IS GIVEN AS BACKGROUND TO THE USE OF THE ABOVE STANDARDS.
THE APPLICATION OF THE STANDARDS AND ANY LOCAL REGULATION IS THE RESPONSIBILITY OF THE USER.
EUROPEAN HAZARDOUS AREA EQUIPMENT DIRECTIVE,
STANDARDS AND APPROVALS
ATEX DIRECTIVE
The ATEX Directive 94/9/EC is a directive adopted by the European Union (EU) to facilitate free trade in the EU
by aligning the technical and legal requirements in the Member States for products intended for use in
potentially explosive atmospheres.
The Directive covers electrical and mechanical equipment and protective systems, which may be used in
potentially explosive atmospheres (flammable gases, vapours or dusts.) It became mandatory at the end of
June 2003 for Europe.
One of the significant changes that was introduced in the ATEX directive was the move away from defining
types of equipment by their protection concept and using categories instead. These are in effect levels of
safety. They are linked to the protection concept by the wording in the individual harmonised European
standards. In fact the definition of the categories aligns the protection concept with it’s traditional area of use.
The directive for use is 99/92/EC.
The table below shows the relationship between the category and the expected zone of use.
It is very important to emphasise that the ATEX categories are levels of safety. The various types of protection
are put into these categories of safety as shown in the EN equipment standards. The hazardous area
classification into zones is entirely separate.
However, because the types of protection have been designed for use in particular hazardous areas and the
application/installation standards give the basic suitability of types of protection for different zones, the ATEX
categories align with the zone of use for practical purposes. This is provided that other attributes of the
equipment or zone do not conflict and that the risk assessment for the zone does not dictate differently.
Category 1 - Zone 0
Category 2 - Zone 1
Category 3 - Zone 2
Category
Degree of Safety
1
Very high level
of Safety
Design Requirement
Application
Two independent means of
Where explosive
protection or safe with two
atmospheres are
independent faults
present continuously
Expected Zone of Use
Zone 0 (gas)
and
Zone 20 (dust)
or for lengthy periods
2
High level of
Safety
Safe with frequently
occurring disturbances or
with a normal operating
fault
Where explosive
atmospheres are
likely to occur
Zone 1 (gas)
and
Zone 21 (dust)
3
Normal level
of Safety
Safe in normal operation
Where explosive
atmospheres are
likely to occur
infrequently and be
of short duration
Zone 2 (gas)
and
Zone 22 (dust)
ATEX Categories and Applications
2
STEP BY STEP PRODUCT SELECTION GUIDE
STEP 1
Establish if the hazardous area is due to the presence of an explosive gas or an explosive dust.
EXPLOSIVE GASES
Using the table FIG. 1.0 below, ascertain first if the gas present is a group I or group II gas.
●
Group I gases are firedamp methane gas. These are usually associated with mining applications.
●
Group II gases are all other explosive gases as listed opposite with relevant subdivisions A, B or C according
to the nature of the chemical content. These are usually associated with surface applications.
GROUP IIA
Hydrocarbons
Mixtures of
Alkanes:
hydrocarbons:
Methane
Industrial methane
Ethane
Turpentine
Propane
Petroleum naphtha
Butane
Oil naphtha
Pentane
Petroleum (including
Hexane
petroleum spirits)
Heptane
Dry cleaning solvents
Octane
Fuel oil
Nonane
Kerosene
Decane
Gas-oil
Cyclobutane
Benzole for cars
Cyclopentane
Compounds containing
Cyclohexane
oxygen:
Cycloheptane
Oxides:
Methylcyclobutane
(including ethers):
Methylcyclopentane
Carbon monoxide
Methylcyclohexane
Dipropyl ether
Ethylcyclobutane
Ethylcyclopentane
Alcohols and phenols:
Ethylcyclohexane
Methanol
Decahydronaphthalene
Ethanol
(decaline)
Propanol
Butanol
Alkenes:
Pentanol
Propene (propylene)
Hexanol
Aromatic hydrocarbons:
Heptanol
Styrene
Octanol
Methylstyrene
Nonanol
Cyclohexanol
Benzene and its
Methylcyclohexanol
derivatives:
Phenol
Benzene
Cresol
Toluene
Diacetone-alcohol
Xylene
Ethylbenzene
Aldehydes:
Trimethylbenzene
Acetaldehyde
Naphthalene
Methaldehyde
Cumene
Cymene
COMBUSTIBLE DUSTS
Ketones:
Acetone
Ethyl-methyl ketone
Propyl-methyl ketone
Butyl-methyl ketone
Amyl-methyl ketone
2,4-Pentanedione
(acetylacetone)
Cyclohexanone
Chloroethylene
(vinyl chloride)
Benzyl trifluoride
Methylene chloride
Compounds containing
Oxygen:
Acetyl chloride
Chloroethanol
Esters:
Methyl formate
Ethyl formate
Methyl acetate
Ethyl acetate
Propyl acetate
Butyl acetate
Amyl acetate
Methyl methacrylate
Ethyl methacrylate
Vinyl acetate
Ethyl acetyacetate
Compounds containing
Sulphur:
Ethyl mercaptan
Propyl mercaptan
Thiophene
Tetrahydrothiophene
Acids:
Acetic acid
Amines:
Methylamine
Dimethylamine
Trimethylamine
Diethylamine
Propylamine
Butylamine
Cyclohexylamine
Monoethanolamine
Diaminoethane
Anline
Dimethylaniline
Amphetamine
Toluidine
Pyridine
Compounds containing
halogens
Compounds with no
Oxygen:
Chloromethane
Chlorethane
Bromoethane
Chloropropane
Chlorobutane
Bromobutane
Dichlorethane
Dichloropropane
Chlorobenzene
Benzyl chloride
Dichlorobenzene
Allyl chloride
Dichloroethylene
Compounds containing
Nitrogen:
Ammonia
Acetonitrile
Nitromethane
Nitroethane
GROUP IIB
GROUP IIC
Hydrocarbons
Allylene (Propyn)
Ethylene
Cyclopropane
Butadine
Hydrogen
Acetylene
Carbon disulphide
Compounds containing
Nitrogen:
Acrylonitrile
Isopropyl nitrate
Hydrocyanic acide
Compounds containing
Oxygen:
Mrthyl ether
Ethylmethyl ether
Ethyl ether
Butyl ether
Ethylene oxide
(epoxyethane)
Epoxy-propane
Dioxoian
Dioxin
Trioxin
Butyl hydoxyacetate
Tetrahydrofurfuryl
Methyl acrylate
Ethyl acrylate
Furane
Crotonaldehyde
Acrolien
Tetrahydrofuran
Mixtures:
Gas from a coke
furnace
Compounds containing
Halogens:
Telrafluoroethylene
Propane, 1 chloro.
2,3 epoxy
(epichlorohydrin)
FIG 1.0
If an area is classed as hazardous due to the presence of combustible dust, it is important to establish if it is a
metallic or non metallic dust. The latest series of standards for electrical apparatus in the presence of
combustible dust that will provide protection concepts, installation and selection requirements will be the
EN/IEC 61241 series.
The most commonly used part of the EN 61241 series applicable to luminaires will be EN 61241-1: Protection by
enclosures with marking "tD". It should be noted that this standard outlines to two techniques that provide
equivalence in safety but different requirements in terms of selection and installation.
The two techniques are "Practice A" and "Practice B", practice B is principally a prescriptive based technique
where practice A is performance based. Practice A is the most commonly used technique, where dust may
form in layers up to 5mm thick and where a temperature difference of 75K is specified between the maximum
surface temperature and the ignition temperature of the dust; the method of determining dust ingress is
according to IEC 60529 the IP code. Practice A and Practice B apply to Zones 21 and 22. For clarity the zones
for dust can be described as follows:
ZONE 21
Where a combustible dust, as a cloud, is likely to occur during normal operation in sufficient quantity to be
capable of producing an explosive concentration of combustible or ignitable dust in mixture with air.
ZONE 22
In this zone, combustible dust clouds may occur infrequently, and persist for only a short time, or in which
accumulation or layers of combustible dust may be present under abnormal conditions and give rise to
ignitable mixtures of dust in air. Where following an abnormal condition, the removal of dust accumulations or
layers cannot be assured, then the area shall be classified as zone 21.
3
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
STEP 2
Now having established which gas or dusts are present, the next thing to establish is the hazardous area category.
FIG 1.1 below sets out the zone definitions to classify your area.
ZONE
TYPE OF PROTECTION ASSIGNED TO APPARATUS
Zone 0
An area in which an explosive atmosphere is continuously present or for long periods or frequently
Zone 1
An area in which an explosive atmosphere is likely to occur in normal operation occasionally
Zone 2
An area in which an explosive atmosphere is not likely to occur in normal operation
and if it occurs it will exist only for a short time.
(Zone 2 is often described as the ‘remotely hazardous area’.)
HAZARDOUS AREA CLASSIFICATION
FIG 1.1
Using the guide in FIG 1.1 you can now classify the hazardous area into a zone. If you are unsure as to which
zone an area should be classified as, please refer to your local health and safety officer or your fire brigade
for guidance. Victor Lighting or any other manufacturer of hazardous area equipment is not able to offer any
advice in this respect.
STEP 3
Having now identified the zone and gas/dust present in the hazardous area, the ignition temperature of the
gas/dust needs to be ascertained. For atmospheres containing explosive dust, the ignition temperature of the
dust needs to be established both when it is in a cloud and when it is in a layer. This information can be found
from the table in FIG 1.2.
EXPLOSIVE GASES
GAS
IGNITION
TEMP oC
GAS
IGNITION
TEMP oC
GAS
IGNITION
TEMP oC
Acetic acid (glacial)
464
Isopropyl ether
443
Vinyl chloride
472
Acetone
465
Mesityl oxide
344
Xylenes (o-xylene)
463
Acrylonitrile
481
Methane (natural gas)
537
Acrolein (inhibited)
220
Ammonia
651
Methanol (methyl alcohol)
385
Arsine
NA
Benzene
498
3-methyl-1-butanol (isoamyl alcohol)
350
Butadiene
420
Butane
287
Methyl ethyl ketone
404
Ethylene oxide
429
1-butanol (butyl alcohol)
343
Methyl isobutal keytone
448
Hydrogen
500
2-butanol (secondary butyl alcohol)
405
2-methyl-1-propanol (isobutyl alcohol) 415
Propylene oxide
449
N-butyl acetate
425
2-methyl-1-propanol (tertiary butyl)
478
Propylnitrate
175
Isobutyl acetate
421
Petroleum naphta
288
Ethylene
450
Sec-butyl alcohol
343
Pyridine
482
Ethylenmine
320
Di-isoutylene
391
Octanes
206
Ethyl mercaptan
300
Ethane
472
Pentanes
260
Ethyl sulfide
NA
Ethanol (ethyl alcohol)
363
1-pentanol (amyl alcohol)
300
Hydrogen cyanide
538
Ethyl acetate
426
Propane
432
Hydrogen sulfide
260
Ethylene diamine (anhydrous)
385
1-propanol (propyl alcohol)
412
Morpholine
310
Ethylene dichloride
413
2-propanol (isopropyl alcohol)
399
2-nitropropane
428
Gasoline (56-60 octane)
280
Propylene
455
Tetrahydrofuran
321
Hexanes
223
Styrene
490
Unsymmetrical dimethyl
Heptanes
204
Toluene
480
hydrazine (udmh 1. 1-
Isoprene
395
Vinyl acetate
402
dimethyl hydrazine
249
4
EXPLOSIVE DUSTS
METALLIC
MATERIAL
EXPLOSIVE DUSTS
NON METALLIC
CLOUD LAYER
Aluminum
Magnesium
Titanium
Zinc
Bronze
Chromium
Tin
Cadmium
650
620
330
630
370
580
630
570
MATERIAL
Alfalfa
Cocoa
Coffee
Corn
Cornstarch
Malt
Skim milk
Rice
Sugar
Wheat
Coal (pittsburgh seam)
Wheat flour
Cellulose acetate
Ethyl acetate
Nylon
Polyethylene
Polystyrene
Epoxy
Polyurethane
Cork
Wood flour (white pine)
760
490
510
430
190
400
430
250
EXPLOSIVE FIBRES
MATERIAL
CLOUD LAYER
Cotton lint
Flax
Rayon
520
430
520
230
250
CLOUD LAYER
460
420
410
400
380
400
490
440
350
480
610
380
450
450
500
450
560
540
550
490
470
200
200
220
250
200
250
200
220
400
220
180
360
390
390
430
380
390
280
260
FIG 1.2
STEP 4
Knowing the ignition temperature of the explosive atmosphere, the zone and the gas grouping or dust type
we are better able to decide upon the appropriate type of electrical apparatus required. It is important
therefore to understand the certified protection concepts recognised for safe operation as used for an ATEX
category and/or within a zone.
The category in ATEX links to types of protection listed below. If the ATEX categories are used as a cross
reference to zones then the protection concepts listed apply.
ATEX CATEGORY PROTECTION TYPE - STANDARDS AND PROTECTION METHODS
CATEGORY
1
2
PROTECTION TYPE
STANDARDS
PROTECTION METHOD
Ex 'ia' Intrinsic Safety.
EN 60079-11
Where the design limits the ignition spark energy to
below that which will ignite the explosive gas.
Safe even with two simultaneous faults.
Special protection for
Category 1 [and Zone 1]
EN 60079-26
Special construction normally based on the use of
two independent types of protection both
individually suitable for Category 1.
Intrinsic Safety
EN 60079-11
All protection methods described above for
Category 1 are also suitable for Category 2.
Ex 'e' Increased Safety
EN 60079-7
Design prevents any ignition from occurring by
ensuring no normally sparking components are
used and other components reduce the risk of
causing a fault that may cause an ignition. This is
achieved by strictly controlling and limiting the
temperature of components, ensuring adequate
insulation is used, all electrical connections are
true and the IP rating offers adequate protection
against contamination.
Ex 'd' Flameproof
EN 60079-1
The components may produce sparks that could
cause ignition of the explosive gas but which are
housed in an explosive proof enclosure. The design
of the enclosure may allows the gas to enter, but
any explosion is contained within the enclosure.
5
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
CATEGORY
PROTECTION TYPE
STANDARDS
PROTECTION METHOD
Ex 'ib' Intrinsic Safety
As Ex ia
As Ex ia but allows for the occurrence of only one
component fault.
Ex 'tD'
EN 61241-1
Design ensures dust ingress protection and surface
temperature limitation to avoid ignition of dust
layer or cloud.
Ex 'm' Encapsulation
EN 60079-18
Integral components which can potentially ignite
an explosive gas are encapsulated allowing the
isolation of these components from the explosive
atmosphere surrounding them. This allows the strict
control of surface temperatures under normal and
fault conditions.
Ex 'p' Pressurised
Apparatus
EN 60079-2
One type of pressurisation maintains a positive
static pressure inside the apparatus to prevent
entry of gas and another maintains a continuous
flow of air or inert gas to neutralise or carry away
any explosive mixture entering or being formed
within the enclosure. Essential to these methods
are continuous monitoring systems to ensure their
reliability and purging schedules on installation and
following opening.
As special protection, Ex 's' is not subject to any
formal standard as such. It is used where
equipment does not comply exactly with
standards but where its method of operation is
proven to be safe in a hazardous area
environment.
Ex 's' Special Protection
Ex 'q' Powder filling
EN 60079-5
3
This technique involves the mounting of potentially
incendive components in an enclosure filled with
sand or similar inert powder. The sand prevents
explosive ignition. It was originally developed to
protect heavy duty traction batteries. It is now
primarily of use where the incendive action is the
abnormal release of electrical energy by the
rupture of fuses or failure of components used in
electronic apparatus. The likelihood of possible
incendive failure of the components is assessed
and precautions taken to minimise it. Usually Ex q is
used for discrete sub-assemblies and components
inside Ex e apparatus.
All protection methods described above for
Category 1 & Category 2 are suitable for use in
Category 3
Ex 'n' non sparking
EN 60079-15
This is a method very similar to Ex 'e'
increased safety although not as stringent. The
components are designed so as not to produce
any sparks or dangerous temperatures in
operation.
Ex 'nA' and Ex 'nR'
EN 60079-15
The Ex non sparking 'nR' denotes the use of a
restricted breathing enclosure. This technique is
used where internal components run hotter than
the required T rating. The T rating is achieved by
mounting the offending components in a sealed
enclosure to prevent the explosive atmosphere
contacting them. This technique by virtue
incorporates high IP ratings of minimum IP65.
Ex 'o' Oil Immersion
EN 60079-6
Ex 'o', involves the immersion of the sparking
components in oil with controlled venting.
FIG 1.3
6
STEP 5
Now that you have clarified the gases/dusts present, their ignition temperature, the zone and
applicable protection methods, the certified temperature codings must be understood for choosing the
correct luminaire. Failure to understand the relationships could result in selecting an inappropriate
luminaire for the zone and atmosphere. If the luminaires T rating code signifies the surface temperature
of the equipment is greater than the ignition temperature of the gas/dust present, the luminaire will
ignite the surrounding atmosphere causing an explosion.
Below FIG 1.4 shows the temperature codes related to surface temperatures. Using this table check the
ignition temperature of the gas/dust present, as shown in FIG 1.2. This will then indicate the suitability of
the equipment you have selected, or the temperature rating of the equipment you need to select.
TEMPERATURE
MAXIMUM SURFACE TEMPERATURE
CLASSIFICATION
OF EQUIPMENT (OC)
T1
T2
T3
T4
T5
T6
450
300
200
135
100
85
FIG 1.4
STEP 6
The environment that the equipment will operate in is also important. Many environments are arduous
and may involve the equipment being subject to the following:
TYPES OF ENVIRONMENT
EXAMPLES
Extreme high or low temperatures
Arduous weather conditions
Immersion in water
Subject to dusty atmospheres
Middle East/Norway
Offshore/Marine
Dry docks
Clean rooms/Grain silos
FIG 1.5
In order to ensure that the equipment selected will perform in the environment for which it is intended,
the following factors of equipment performance need to be considered.
●
Ambient temperature - Does the equipment have certification to operate within the minimum
and maximum temperatures of the environment ?
●
How much dust/liquid etc will the equipment be subjected to and for how long ?
●
Will the equipment be subject to any likely impact during its service life ?
●
Are there any chemicals/vapours present that could attack luminaires with plastic enclosures ?
When selecting equipment, the product information will state the certified operating temperature such
as the example below. If in selecting equipment the product information contains no statement or
reference to ambient temperature be very sceptical and do not assume. Always check and obtain
written confirmation from the manufacturer.
Example Floodlight VL65A
-50OC to +55OC
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
Always check that the ambient temperature certification is applicable to your relevant choice of
product as maximum ambient performances are often quoted and may only be applicable to certain
product variants.
If the environment will subject the equipment to any dust/fibres/liquids, ensure it is certified to an
appropriate level of ingress protection. This can be done using the table below.
INDEX OF PROTECTION (IP XX)
IP** degree of protection of enclosures of electrical equipment in accordance with standards IEC 529,
EN 60529 and NFC 20-010. The ingress protection number (IP) is found by putting the first and second
figure together. An example is shown below.
1st figure: Protection against solid bodies
0
1
2
3
4
5
6
TESTS
IP
No
Protected against solid
Protection bodies of 50 mm and
greater (e.g. accidental
contact with the hand)
Protected against solid
bodies of 12.5 mm and
greater (e.g. finger)
Protected against solid
bodies of 2.5mm and
greater (e.g. tools, wires)
Protected against solid
bodies larger than 1 mm
(e.g. thin tools and fine
wires)
Protected against dust
(no harmful deposit)
Completely protected
against dust
2nd figure: Protection against liquids
IP
0
1
2
3
4
5
6
7
8
TESTS
7
No
Protected against
Protection vertically falling
drops of water
(condensation)
Protected against
drops of water
falling up to 15o
from the vertical
Protected against
drops of water
falling up to 60o
from the vertical
Protected against
Protected against
splashing water from jets of water from all
all directions
directions
Protected against
powerful jets of
water from all
directions
Protected against
the effects of
temporary
immersion in water
Protected against
the continuous
effects of immersion
in water having
regard to specific
conditions
FIG 1.6
Example Floodlight VL65A
Ingress protection to IP66 and IP67
IK CODE
IK00
IK01
IK02
IK03
IK04
IK05
IK06
IK07
IK08
IK09
IK10
Impact
a
0.14
0.2
0.35
0.5
0.7
1
2
5
10
20
energy
STEP 7... FINALLY
Joule
Having covered all the rules and safety considerations of the operation of electrical equipment in a
a not protected
hazardous
area it is
possible to select a safe and appropriate product.
tonow
this standard
FIG 1.7
STEP 7... FINALLY
Having covered all the rules and safety considerations of the operation of electrical equipment in
a hazardous area it is now possible to select a safe and appropriate product.
8
INTERNATIONAL STANDARDS AND APPROVALS
A number of products in the Victor Lighting range are certified to national and international standards,
details of these are outlined below.
IECEx International Certification Scheme
“The aim of the IECEx Scheme is to facilitate international trade in electrical equipment
intended for use in explosive atmosphere (Ex equipment) by eliminating the need for multiple
national certification while preserving an appropriate level of safety.”
“The final objective of the IECEx Scheme is worldwide acceptance of one standard, one
certificate and one mark.”
GOST-R (Russia)
Gosstandart of Russia is responsible for:
●
establishment of the general rules and recommendations for certification of products,
services (works) and systems of quality and production harmonised with international
norms and rules;
●
carrying out the State registration of the mandatory and voluntary certification systems
and of the conformity marks.
Russia participates in the following international certification systems:
●
System of the International Electrotechnical Commission (IEC) for tests of electrical
equipment on conformity to the safety standards.
FSETAN
Rostekhnadzar (Federal service on ecological, technical and nuclear supervision) was
formally known as Gosgortekhnadzor (GGTN) and is responsible for the issue of permits and
licenses for a broad range of machinery and equipment. As a separate entity to
Gosstandart, FSETAN requires product types that fall under its jurisdiction to undergo a further
certification process.
All potentially hazardous machinery and equipment, such as pressure vessels, boilers, burners,
lifts and cranes is subject to FSETAN approval, even if it has already obtained a GOST-R Coc.
In addition, any machinery to be used in hazardous or potentially explosive environments,
such as oil or gas fields, refineries or chemical plants also require a separate FSETAN permit.
This applies even where the equipment itself would not normally require GOST-R approval.
GB (China)
The GB mark is the Chinese national safety certification scheme. These standards are aligned
to the latest IEC standards.
TIS (Thailand)
Thai industrial standards are a national product certification scheme. This is designed to
ensure products used within the county meet minimum electrical and quality standards.
9
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
NORTH AMERICAN STANDARDS AND APPROVALS
PRODUCT CODING
As in the European section, products are coded according to their certification for use in particular
types of environments.
rating
Class
Division
Gas Grouping
Class I
Division 2
Groups A, B, C and D
Surface temperature
T4A
STEP I
As detailed in the European section in STEP 1 the gas/dust/fibre present in the hazardous area needs to
be identified and classified under the CEC\NEC (North American) classifications detailed in FIG 1.9.
CLASS I (EXPLOSIVE GASES)
GROUP A ATMOSPHERE
GROUP D ATMOSPHERE
Methane (Natural Gas)
580
Acetic acid (glacial)
464
Mesityl oxide
Propane
480
Acetone
465
Methane (natural gas)
537
Petrol
400
Acrylonitrile
481
Methanol (methyl alcohol)
385
Ammonia
651
3-methyl-1-butanol (isoamyl alcohol)
350
Benzene
498
Methyl ethyl ketone
404
Butane
287
Methyl isobutal keytone
448
1-butanol (butyl alcohol)
343
2-methyl-1-propanol (isobutyl alcohol) 415
2-butanol (secondary butyl alcohol)
405
2-methyl-1-propanol (tertiary butyl)
N-butyl acetate
425
Petroleum naphta
288
Isobutyl acetate
421
Pyridine
482
Sec-butyl alcohol
343
Octanes
206
Di-isoutylene
391
Pentanes
260
Ethane
472
1-pentanol (amyl alcohol)
300
GROUP B ATMOSPHERE
Acrolein (inhibited)
220
Arsine
NA
Butadiene
420
Ethylene oxide
429
Propylene oxide
449
Propylnitrate
175
GROUP C ATMOSPHERE
344
478
Ethanol (ethyl alcohol)
363
Propane
432
305
Ethyl acetate
426
1-propanol (propyl alcohol)
412
Ethylene
450
Ethylene diamine (anhydrous)
385
2-propanol (isopropyl alcohol)
399
Ethylenmine
320
Ethylene dichloride
413
Propylene
455
Ethyl mercaptan
300
Gasoline (56-60 octane)
280
Styrene
490
Ethyl sulfide
NA
Hexanes
223
Toluene
480
Hydrogen
500
Heptanes
204
Vinyl acetate
402
Hydrogen cyanide
538
Isoprene
395
Vinyl chloride
472
Hydrogen sulfide
260
Isopropyl ether
443
Xylenes (o-xylene)
463
Morpholine
310
Acetylene
2-nitropropane
428
Tetrahydrofuran
321
Unsymmetrical dimethyl
hydrazine (udmh 1. 1dimethyl hydrazine
249
10
CLASS II (EXPLOSIVE DUSTS)
GROUP E
MATERIAL
CLOUD LAYER
Aluminum
Magnesium
Titanium
Zinc
Bronze
Chromium
Tin
Cadmium
650
620
330
630
370
580
630
570
760
490
510
430
190
400
430
250
GROUP F
MATERIAL
MATERIAL
CLOUD LAYER
Alfalfa
Cocoa
Coffee
Corn
Cornstarch
Malt
Skim milk
Rice
Sugar
Wheat
460
420
410
400
380
400
490
440
350
480
200
200
220
250
200
250
200
220
400
220
MATERIAL
Wheat flour
Cellulose acetate
Ethyl acetate
Nylon
Polyethylene
Polystyrene
Epoxy
Polyurethane
Cork
Wood flour (white pine)
CLOUD LAYER
380
450
450
500
450
560
540
550
490
470
360
390
390
430
380
390
280
260
CLOUD LAYER
Coal (Pittsburgh Seam)
610
180
CLASS III (EXPLOSIVE FIBRES)
MATERIAL
CLOUD LAYER
Cotton lint
Flax
Rayon
520
430
520
230
250
FIG 1.9
Using FIG 1.9 we can also ascertain the ignition temperatures of the identified gas/dust/fibre present.
STEP 2
Select the Gas/Dust/Fibre type present from FIG 1.9 and note:
●
Material classification
I = Gas
II = Dust
III = Fibre
●
The material group
●
If the material present is a dust or fibre and whether it forms a cloud or a layer on surfaces
●
The ignition temperature of the material
STEP 3
Assess the hazardous area as in STEP 2 of the european section with regard to the potential frequency
and longevity of an explosive atmosphere. This can be done using the classifications below.
DIVISION
CLASSIFICATION CRITERIA
1
Gas/dust/fibres normally present in explosive amounts during operation.
2
Gas/dust/fibres not normally present in explosive amounts during operation.
11
INTERNATIONAL REFERENCE GUIDE TO HAZARDOUS AREAS
STEP 4
Now having defined the explosive gas/dust/fibres present, the nature of their presence, their ignition
temperature and the classification of the hazardous area we, need to determine the temperature
classifications to ensure the selection of equipment which will be safe in operation.
The classifications, which are similar to Europe, are further subdivided as follows
NORTH AMERICAN TEMPERATURE CLASSIFICATIONS
Temperature in Fahrenheit
Temperature in Celsius
North American Temperature code
842
572
536
500
446
419
392
356
329
320
275
248
212
185
450
300
280
260
230
215
200
180
165
160
135
120
100
85
T1
T2
T2A
T2B
T2C
T2D
T3
T3A
T3B
T3C
T4
T4A
T5
T6
FIG 2.0
Product markings will often show the actual rated temperature in brackets next to the temperature
code to make judgement and selection easier.
STEP 5
Finally we need to take cognisance of the environment in which the equipment will be operating with
respect to the concentration of liquids/gas/dust/fibres and ambient temperature.
In North America environmental protection is classified using the NEMA standard as opposed to the
European IP protection standard.
On establishing these operating conditions we can determine the desired environmental protection
required of the equipment by using the table below.
INDEX OF NEMA PROTECTION
Enclosure type
Provides a degree of protection against the
following environmental conditions
2
3
Dripping and light splashing of non-corrosive
liquids and falling dirt
x
x
x
Circulating dust, lint, fibres and flyings*
-
x
Settling airborne dust, lint, fibres and flyings*
-
Hose-down and splashing water
-
Corrosion
3R 3S
4 4X 5
6
6P 12 12K 13
x
x
x
x
x
x
x
x
x
-
x
x
x
-
x
x
x
x
x
x
-
x
x
x
x
x
x
x
x
x
-
-
-
x
x
-
x
x
-
-
-
-
-
-
-
-
x
-
-
x
-
-
-
Occasional temporary submersion
-
-
-
-
-
-
-
x
x
-
-
-
Occasional prolonged submesrion
-
-
-
-
-
-
-
-
x
-
-
-
Oil and coolant seepage, spraying and splashing
-
-
-
-
-
-
-
-
-
-
-
x
Rain, snow and external formation of ice**
-
x
x
x
x
x
-
x
x
-
-
-
External formation of ice***
-
-
-
x
-
-
-
-
-
-
-
-
Wind-blown dust
-
x
-
x
x
x
-
x
x
-
-
-
FIG 2.1
* These fibres and flyings are non hazardous materials and are not considered sa Class II or III combustable dust or easily ignitable
fibres or flyings. For these types of material refer to the Canadian Electrical Code.
** External operating mechanism(s) shall not be required to operate when the enclosure is covered in ice.
*** External operating mechanism(s) shall be operable when the enclosure is covered in ice.
FIG 2.1
12
EUROPEAN vs NORTH AMERICAN HAZARDOUS AREA CLASSIFICATIONS
TEMPERATURE RATINGS
Temperature in
Temperature in
North American
IEC
Fahrenheit
Celsius
Temperature code
Temperature code
842
450
T1
T1
572
300
T2
T2
536
280
T2A
T2
500
260
T2B
T2
446
230
T2C
T2
419
215
T2D
T2
392
200
T3
T3
356
180
T3A
T3
329
165
T3B
T3
320
160
T3C
T3
275
135
T4
T4
248
120
T4A
T4
212
100
T5
T5
185
85
T6
T6
Note Actual temperatures may be shown instead of T - codes in North America
Note Actual temperatures may be shown instead of T - codes in North America
COMPARISON OF 'NEMA AND IP ENVIRONMENTAL PROTECTION'
CSA or NEMA
Enclosure type
Ingress protection type
IP23
2
IP30
IP55
IP65
IP66
IP67
x
3
x
3R
x
3S
x
4
x
4X
x
6
12
13
x
x
x
x
HAZARDOUS AREA CLASSIFICATIONS
North American to IEC / CENELEC Zone method of protection usability chart.
(Use with caution: most Category 1 products cannot be used in North American Class I Div. 1 Areas)
North American Approval
CENELEC/IEC equivalent Zone
Class I, Division 1
Zone 0 and 1
Class I, Division 2
Zone 2
North American Gas & Vapour Groups
CENELEC/IEC Gas and Vapour classification
Group A
IIC
Group B
IIC
Group C
IIB
Group D
IIA
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