Explosion Proof Basics

Explosion Proof Basics
Basics of Explosion Protection
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Introduction to Explosion Protection
for Electrical Apparatus and Installations
Product Range
Product Range
R. STAHL SCHALTGERÄTE GMBH
A company of the
R. STAHL TECHNOLOGY GROUP
PRODUCT RANGE
Switchgear
Lighting
Instrumentation
Installation equipment
Fluorescent light fittings
Safety barrier modules
Control and monitoring equipment
Emergency fluorescent light fittings
I.S. Isolators
Terminal boxes and control stations
Light fittings in sheet steel
Remote I/O
Position switches
Pendant light fittings
Operating and monitoring systems
Load and motor switchgear
Bulk head light fittings
Instrumentation systems
Switching and distribution systems with EEx modules
Floodlights
Switching and distribution systems with
flameproof enclosures
Portable lamps
Control equipment in pressurized enclosures
Signaling and monitoring equipment
Portable searchlights
Tank inspection lights
Emergency light power supply units
Measurement and control equipment
Equipment for conduit installation
2
It is a fact that gases, vapours and mists escape during the
production, processing, transportation and storage of flammable materials in the chemical and petrochemical industries, as
well as in the production of mineral oil and natural gas, in mining
and in many other sectors. During many processes also
flammable dusts are created. These flammable gases,
vapours, mists and dusts, form an explosive atmosphere with
the oxygen of the air. In the case that this atmosphere is ignited,
explosions take place which can result in severe harm to
human life and property
To avoid the danger of explosions, protective regulations in
form of laws, specifications and standards have been
developed in most countries and are aimed at ensuring that a
high level of safety is observed. Due to the growing international
economic link, extensive progress has been made in harmonizing the regulations for the explosion protection. The conditions
for a complete harmonization have been created in the European Union by the 9/94 EC Directive. However, world-wide
there is still much to be done in this area.
The aim of this brochure is to provide both experts and
interested laymen with an overview in the field of explosion
protection; in conjunction with electrical apparatus and
installations, it does not replace the study of the relevant statutory regulations and applicable standards.
In mining, miners underground have always lived under the
threat of firedamp explosions. Herein lie the origins of
explosion protection, which has been consistently developed
in industrialized countries and now provides a high level of
safety.
Picture of a pit explosion
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Introduction
Introduction
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Contents
Contents
2
1
The basic physic Principles and Definitions of Explosion Protection
Statutory Regulations and Standards
2.1
2.2
International Standards
European Directives and Standards
2.2.1 Introduction
2.2.2 EC Directive 94/9/EC (ATEX 100a)
2.2.3 Certification and Marking
2.3
3
5
4
6
Statutory Regulations in Germany
Technical Principles
3.1
Zone Classification
3.2
Explosion Groups and Temperature Classes
3.3
Types of Protection
3.3.1 Application and Combination of Types of Protection ”d” and ”e”
3.3.2 Applications of Type of Protection “Intrinsic Safety“
Installation and Operation of Electrical Equipment
4.1
Duties of Installer, Manufacturer and Operator
4.2
Classification of Zones and Selection of Apparatus
4.3
Methods of Installation
4.4
Repair and Maintenance
Explosion Protection in North America
5.1
Introduction
5.2
Classification of Hazardous Locations
5.3
Regulations for Installation
5.4
Constructional Requirements
5.5
5.6
Degrees of Protection provided by Enclosures
Certification and Marking
Appendix
6.1
6.2
6.3
Comparison of IEC Publications and European Standards (EN)
Safety Characteristics of Flammable Gases and Vapours
Classification of Hazardous Locations in North America
6.4
6.5
Constructional Requirements in North America
Degrees of Protection to IEC 60529 – IPXX
6.6
6.7
Degrees of Protection to NEMA Standards
Overview of the most important Approval and Testing Authorities
Literature
Index
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Page 6-7
Page 8-10
Page 11-15
Page 16-17
Page 18-19
Page 20-26
Page 28
Page 29
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1. The basic physic Principles and Definition
of Explosion Protection
An explosion is the sudden chemical reaction of a flammable
material with oxygen with the simultaneous release of high
energy. Flammable materials may be present in the form of
gases, vapours, mists or dusts. In order for a fire or explosion
to occur three conditions must exist:
1. Flammable material (in ignitable quantities)
2. Oxygen (in the air)
3. Ignition source
Flammable
brennbarer
MaterialStoff
E x p l o s i o n
Ignition
Source
Sauerstoff
Oxygen
Zündquelle
Certain characteristic properties of these materials are
required for safety considerations. The flash point of a
flammable liquid is the minimum temperature at which a
liquid gives off vapour in sufficient concentration to form an
ignitable mixture with air near the surface of the liquid (at
normal air pressure). If the flash point of a flammable liquid is
far above the maximum temperatures which arise, an explosive atmosphere may not be formed. The flash point of a mixture of various liquids may be lower than that of the individual components.
Flammable liquids are classified into four danger classes in
the German Technical Regulations for Flammable Liquids (TRbF):
Danger class
AI
AII
AIII
B
Flash point
< 21°C
21 to 55°C
> 55 to 100°C
< 21°C, soluble in water at 15°C
between the lower and upper explosion limit that the mixture
reacts explosively when ignited. The explosion limits depend
on the ambient pressure and the proportion of oxygen in the
air.
Substance
designation
Acetylene
Ethylene
Lower explosion limit
[Vol. %]
2.3
2.3
Upper explosion limit
[Vol.%]
78.0 (self-decomposing)
32.4
Gasoline
Benzol
~ 0.6
1.2
~8
8
Natural gas
Heating oil/diesel
4.0 (7.0)
~ 0.6
13.0 (17.0)
~ 6.5
Methane
Propane
4.4
1.7
16.5
10.9
Carbon disulphide
Town gas
Hydrogen
0.6
4.0 (6.0)
4.0
60.0
30.0 (40.0)
77.0
Explosion Limits of selected Gases and Vapours
Extract from the table ”Safety characteristics of
flammable gases and vapours” by K. Nabert
and G. Schön - (6th addendum)
The terms used here are deflagration, explosion or detonation,
depending on the speed of combustion.
An atmosphere is described as dangerous or explosive if there
is danger to human life or to property. An explosive atmosphere
of even just a few litres can be dangerous in an enclosed space.
Source of Ignition
In order for an explosive atmosphere to ignite, a certain
amount of energy is needed. The minimum ignition energy is
the smallest possible amount of energy which is converted
during the discharge of a capacitor and is just enough to
ignite the most ignitable mixture. The minimum ignition
energy is around 10 -5J for hydrogen and a few
joules for certain dusts.
For an explosive atmosphere to form, the flammable material
must be present in a certain concentration.
100 Vol %
concentration of air
0 Vol %
mixture
too lean
ignition range
mixture
too rich
no
combustion
deflagration,
no explosion
lower
0 Vol %
explosion limit
upper
concentration of
100 Vol %
combustible material in air
If the concentration is too low (lean mixture) or too high (rich
mixture), no explosion occurs, rather there is just a slow
combustion reaction or none at all. It is only in the range
6
Comparison between the minimum ignition energy of gases,
dusts and practical sources of ignition.
1
Ignition can be caused by various sources:
• hot surfaces
• electrical arcs and sparks
• electrostatic discharge
• atmospheric discharge (lightning)
• mechanical friction or impact sparks
• electromagnetic radiation
• ultrasonics
• adiabatic compression (shock waves)
• ionizing radiation
• optical radiation
• chemical reactions
• open flames
Primary Explosion Protection
The term primary explosion protection refers to all precautions which prevent a dangerous, explosive atmosphere from
being created.
This can be achieved by:
• avoiding flammable substances (replacement technologies)
• deactivation (addition of nitrogen, carbon dioxide etc.)
• limitation of the concentration
• natural or artificial ventilation
The principle of integrated explosion protection requires
explosion protection measures to be taken in a certain
sequence.
Integrated
Explosion Protection
Avoiding of the
formation of an
explosive
atmosphere
Prevention of the
ignition of an
explosive
atmosphere
1
2
Limiting of the
results of an explosion
to a harmless
level
3
Secondary Explosion Protection
If the danger of explosions cannot be completely or only partly
avoided by primary explosion protection measures, then measures must be taken which prevent the ignition of an explosive
atmosphere. The hazardous locations are therefore devided
into zones, according to the probability of an explosive atmosphere being created (see Section 3.1). In the USA and other
countries, hazardous locations are classified into Classes and
Divisions (see Section 5). For areas classified in this way,
requirements must be met concerning the apparatus which
are approved to be used in these locations. In addition it is stipulated how to prove that these minimum requirements have
been met (see section 2.2.3 and 5.6).
7
4094-P
Polyester Resin Control Station 8146
2. Statutory Regulations and Standards
2.1 International Standards
The IEC (International Electrotechnical Commission) is
responsible for international standardization in the field of
electrical technology. IEC publications which deal with
explosion protection for electrical apparatus and installations,
are developed by the Technical Committee TC31. IEC publications have the status of recommendations which are used for
orientation purposes for national and regional standards
(see Appendix 6.1).
The IEC has introduced a procedure - the so called IEC-Ex
Scheme - intended to become a globally recognized test and
certification procedure in the field of explosion protected electrical apparatus. Many technical and legal hurdles still have to
be overcome before this procedure can operate world-wide.
2.2 European Directives and Standards
2.2.1 Introduction
Already in 1976 the Council of the European Community established the prerequisite for unrestricted trade of explosion
protected electrical equipment within the European Union
by ratifying the ”Directive on the harmonization of the laws of
the member states concerning electrical equipment for use
in potentially explosive atmospheres (76/117/EEC)”.
This directive has since then been supplemented by further
directives.
Complete harmonization in this area was achieved in 1994
with the new Directive 94/9/EC. Of course, in addition to a
uniform statutory regulation, uniform standards are required
as well. CENELEC is the European Committee for Electrotechnical Standardization in which the countries of the European
Union and the West European EFTA states cooperate.
European standards (EN) are published in three official versions (French, English and German). The members of CENELEC
are obliged to adopt the European Standards unchanged as
national standards.
The European Standards series EN 50 014 and following
which deal with electrical explosion protection, have been
developed by the Technical Committee CENELEC TC31 and
adopted in the EU states as identical national standards (see
table below).
It is determined that the member states of the European
Union may not forbid the free trade of electrical apparatus, if
it complies with these standards and has a Certificate of
Conformity from a recognized EC testing authority.
The European directives and the uniform standards in the
field of electrical explosion protection have proved to be very
worthwhile in practice.
2.2.2 EC Directive 94/9/EC (ATEX 100a)
The EC Directive 94/9/EC was issued in 1994 to further
standardize explosion protection and make corresponding
adjustments in line with a new directive concept. It specifies
the requirements for explosion protected equipment and protective systems by prescribing essential health and safety
requirements. It guarantees the free trade within the European Community, as agreed in Article 100a of the Treaty established between the European Community member states.
This is also where the term ATEX 100a, generally used among
the experts , comes from.
The directive applies to all industrial potentially
explosive areas including mining and also covers dust
explosion protection. The scope covers all electrical and
mechanical equipment and protective systems. In addition to
the basic health and safety requirements, the classification
of the equipment and protective systems according to categories has also been re-organized, as well as the certification and
marking of these.
Constructional Requirements for Explosion Protected Electrical Apparatus
CENELEC
Germany
France
Great Britain
General requirements
EN 50 014
DIN EN 50 014
VDE 0170/0171 T. 1
NF EN 50 014
BS EN 50 014
Type of protection ”o”
EN 50 015
NF EN 50 015
BS EN 50 015
Type of protection ”p”
EN 50 016
DIN EN 50 015
VDE 0170/0171 T. 2
DIN EN 50 016
NF EN 50 016
BS EN 50 016
NF EN 50 017
BS EN 50 017
VDE 0170/0171 T.3
Type of protection ”q”
EN 50 017
Type of protection ”d”
EN 50 018
DIN EN 50 017
VDE 0170/0171 T.4
DIN EN 50 018
NF EN 50 018
BS EN 50 018
EN 50 019
VDE 0170/0171 T.5
DIN EN 50 019
NF EN 50 019
BS EN 50 019
EN 50 020
VDE 0170/0171 T.6
DIN EN 50 020
Type of protection ”e”
Type of protection ”i”
Type of protection ”n”
prEN 50 021
VDE 0170/0171 T.7
pr DIN EN 50 021
pr VDE 0170/0171 T.16
Type of protection ”m”
EN 50 028
DIN VDE 0170/0171 T.9
8
NF EN 50 020
BS EN 50 020
pr C23-521
BS 6941
NF EN 50 028
BS 5501:Part 8
2
• A ”potentially explosive atmosphere” is an atmosphere which
could become explosive due to
local and operational conditions.
Definitions
• ”Electrical installations” are individual or interconnected
items of apparatus for the generation, conversion, storage,
transmission, distribution, measurement, regulation, and
consumption of electrical energy.
• ”Equipment” means machines, apparatus, fixed or mobile
devices, control components and instrumentation thereof and
detection or prevention systems which, separately or jointly,
are intended for the generation, transfer, storage, measurement, control and conversion of energy for the processing of
material and which are capable of causing an explosion
through their own potential sources of ignition.
• ”Protective systems” is the definition for design units which
are intended to halt incipient explosions immediately and / or
to limit the effective range of explosion flames and explosion
pressures. Protective systems may be integrated into equipment separately placed on the market for use as autonomous
systems. The components of the above defined equipment
are not to be considered ”protective systems”.
•”Components” means any item essential for the safe functioning of equipment and protective systems but with no
autonomous function
• An ”explosive atmosphere” is a mixture with air, under
atmospheric condition, of flammable substances in the form
of gases, vapours, mists, or dusts in which, after ignition has
occured, combustion spreads to the entire unburned mixture.
EC Directive
Validity
Range of validity for equipment in
hazardous areas
QM system of manufacturer
Certificate of conformity
Scope
The directive applies to equipment and protective systems for use in potentially explosive atmospheres. Safety devices intended for use outside potentially
explosive atmospheres but required for or contributing to the
safe functioning of equipment with respect to explosion are
also covered by the scope of this Directive. The Directive
ATEX 100a doesn’t include a reference to mandatory standards, whereas specifies the essential health and safety
requirements to be maintained and which are mandatory for
the design and construction. The protection against other
hazards (e.g. electric shock) which could be caused by this
equipment, is required as well.
2.2.3 Certification and Marking
In potentially explosive atmospheres only approved and
marked equipment is allowed to be used. For the placing on
market of explosion protected equipment two directives
apply in parallel.
79/196/EEC
until 30.06.2003
- Electrical equipment
- Gases and vapours
- not for mining
no requirements
94/9/EC
since 01.03.1996
- All equipment and protective systems
- Gases and vapours and dusts
- including mining
”QM certificate” from
Certificate of conformity or inspection
certificate from a resting authority
a designated authority
Manufacturer’s declaration
of on the basis of type
conformity examination
Marking is specified by the Directive and the applicable standards
Name or mark of
manufacturer
Type designation, (e.g.)
6000/562-....
6000/562-....
Address
CE mark, number of testing
—
D-Künzelsau
authority, (e.g. PTB)
Testing authority, Number of certificate, (e.g.)
Mark according to EC Directive
—
PTB No. Ex- 91.C.1045 1)
2)
0102
PTB 97 ATEX 2031 1)
2)
I or II
Group I: M 1 or M 2
Group II: 1 G/D, 2 G/D, 3 G/D
Marking in accordance with EN
Types of protection, (e.g.)
EEx / Ex
d, e, q, ...
ib or [ ib ] 3)
EEx / Ex
d, e, q, ...
ib or [ ib ] 3)
Subdivision for Group Il
(only for d and i)
Temperature class for II
A or B or C
A or B or C
T1 - T6
T1 - T6
Electrical ratings
V, A, W, Hz
V, A, W, Hz
Ambient temperature, if other than -20 °C ... +40 °C, (e.g.)
Ta ≤ 50 °c
Ta ≤50 °c
(free trade of goods)
Group and equipment category:
Mining (I)
Others (II)
1) With an ... X if reference special conditions for use etc.
With a ... U for Ex components
9
2) new: always present, old: not on Ex components
3) Intrinsically safe apparatus: ib / associated apparatus: [ ib ]
Manufacturer’s EC Declaration of Conformity (94/9/EC)
The CE conformity marking and the written declaration of conformity confirm that the product complies with all requirements and assessment procedures specified in the EC Directives.
The certificates from notified bodies are recognized throughout the European Community, moreover many testing authorities have concluded bilateral agreements with other national
testing authorities outside the EC regulating the acceptance of
test results (Appendix Overview of Testing Organizations).
Marking
In addition to the usual data such as the name of the manufacturer, type, serial number and electrical ratings, any data relating to explosion protection must be contained in the marking
(see table above).
The CE marking of the equipment confirms that it is designed
and manufactured in compliance with all applicable EC Directives. For example, an explosion protected luminaire marked
with the CE conformity mark must comply with both the
”Explosion Protection Code of Practice” as well as the ”EMC Directive”.
10
2.3 The Statutory Regulations in Germany
The Directive 94/9/EC (ATEX 100a) required the last modification for the time being to the national regulations. It was
adopted completely into German law on 12 December 1996
when the 11th Regulation on the Equipment Safety Law
became effective.
The requirements concerning equipment used in hazardous
locations are stipulated in the Regulation on Placing on the
Market of Equipment and Protective Systems - Regulation
concening Electrical Installations in Explosive Atmospheres
(ExVO)”.
The installation and operation of electrical systems in hazardous locations is governed by the ”Regulation concerning
Electrical Installations in Explosive Atmospheres (ElexV)”,
which includes a reference to the ExVO in respect of the
requirements concerning the equipment.
These new regulations will replace all previous relevant
regulations with effect from 1.7.2003.
During the transition period, equipment can be certified for
use in explosive atmospheres in accordance with the previous regulation as well as the new Ex-Directive 94/9/EC.
A mixing of both regulations is possible, provided the basic
health and safety requirements of the Directive have been met.
3
3. Technical Principles
3.1 Zone Classification
Hazardous locations are classified into zones to facilitate the
selection of appropriate electrical apparatus as well as the
design of suitable electrical installations. Information and
specifications for the classification into zones are included in
IEC 60 079-10 and in national standards.
Furthermore, a European Directive (ATEX 118a), which deals
with the installation and operation of electrical systems in
hazardous locations and governs the zone classification within
the EC, is currently being prepared.
The following table contains an overview of the zones and
allocation of equipment (equipment category according to
94/9/EC) for the relevant zones.
Gases, Vapours, Mists
Dusts
Definition (94/9/EC)
explosive
atmosphere is
present:
Zone 0 ➞ Category 1 G
Zone 20 ➞ Category 1 D
continiously or longterm or frequently
Zone 1 ➞ Category 2 G
Zone 2 ➞ Category 3 G
Zone 21 ➞ Category 2 D
Zone 22 ➞ Category 3 D
occasionally
infrequently
or short period
which can also occur in these
areas must be further
classified as shown in Group II.
Electrical apparatus in Group II is
further classified into explosion groups
and temperature classes.
Explosion Groups
The ignitability and explosion characteristics of an explosive
mixture are properties typical of the material. The gases and
vapours are classified into explosion groups. Classification
criteria are the ”Maximum Experimental Safe Gap (MESG)”
and the ”Minimum Ignition Current (MIC)”. The MESG and
MIC are determined for the various gases and vapours
according to a stipulated testing arrangement. The maximum
experimental safe gap is the gap width of a vessel with an
adjustable gap of 25 mm path length at which an internal
ignition of an explosive mixture is not propagated to the exterior (IEC 60 079-1A). The minimum ignition current relates to
the minimum ignition current for laboratory methane (IEC
60 079-3).
An overview of the maximum experimental safe gaps and
minimum ignition currents for the various explosion groups is
shown in the following table:
Explosion groups
G = gases, D = dusts
If there are any doubts with the zone classification, the
scope of the protective measures in the entire hazardous
location should be based on the highest possible degree of
likelihood of the occurance of dangerous explosive atmosphere. In such cases use of specialists is recommended.
In Zones 0 and 1, only electrical apparatus with a Certificate of
Conformity or EC Type Examination Certificate may be used,
however in Zone 0 only equipment which has been expressly
approved for this purpose. In Zone 2, electrical apparatus which
meet the basic health and safety requirements of the Directive
94/9/EC and which has a Manufacturer’s Declaration of Conformity can be used. Of course, equipment which has been certified for use in Zones 0 and 1 may also be used in Zone 2.
3.2 Explosion Groups and Temperature Classes
It would be uneconomical and sometimes not even possible
to design all explosion protected electrical apparatus in such
way that it always meets the maximum safety requirements,
regardless of the use in each case. For this reason, the
equipment is classified into groups and temperature classes
in accordance with the properties of the explosive
atmosphere for which it is intended.
First of all a differentiation is made between two groups of
equipment:
Group I: Electrical apparatus for mining.
Group II: Electrical apparatus for all remaining potentially
explosive atmospheres.
In the case of electrical apparatus in Group I (mining), it is
assumed that the only flammable gas to occur is methane,
but in combination with coal dust. Other flammable gases
11
II A
II B
II C
Maximum experimental safe gap
> 0.9 mm
0.5 mm to 0.9 mm
< 0.5 mm
Minimum ignition current ratio
rel. to methane
> 0.8
0.45 to 0.8
< 0.45
The dangerousness of the gases increases from explosion
group IIA to IIC. The requirements for the electrical
apparatus increase accordingly to these explosion groups.
For this reason, the marking of the electrical apparatus must
show for which explosion group it is designed. Electrical
apparatus approved for IIC may also be used for all other
explosion groups.
Temperature Classes
The ignition temperature of a flammable gas or liquid is the
lowest temperature of a heated surface at which the gas/air
or vapour/air mixture ignites. It is ascertained using precisely
defined test equipment (IEC 60 079-4) and represents virtually
the lowest temperature at which a hot surface can ignite a
respective explosive atmosphere. Flammable gases and
vapours may be classified into temperature classes using the
ignition temperature.
The maximum surface temperature of electrical apparatus shall
always be lower than the ignition temperature of the gas/air or
vapour/air mixture in which it is used. Of course, equipment
classified in a higher temperature class (eg T5) may also be
used for application in which a lower temperature class is
required (eg T2 or T3). In North America there is a system
incorporating further classification according to temperature
subclasses.
3.3 Types of Protection
Only explosion protected equipment may be used in areas in
which a dangerous, explosive atmosphere may still be
expected despite the implementation of primary explosion
protection measures.
Electrical, explosion protected equipment can have various
types of protection according to the construction regulations
of the series of standards EN 50 014 following (DIN VDE
0170/0171 Part 1 - following). The type of protection used by
the manufacturer for apparatus essentially depends on the
type and function of the apparatus. From a safety point of
view, all standardized types of protection should be seen as
being equal, but it should be noted here that the type of protection ”n”can only be used in Zone 2.
The table on page 13 shows an overview of the standardized
types of protection and describes the basic principle as well as
the usual applications.
The code letter ”s” is also used in Europe for
non-standardized protection measures.
Temperature Classes according to IEC
Temperature class
IEC/EN
NEC 505-10
T1
T2
Max.
surface temperature
of equipment [°C]
450
300
280
260
230
215
200
180
165
160
135
120
100
T3
T4
T5
T6
Ignition temperatures
of the flammable substance
[°C]
> 450
> 300 ≤ 450
> 280 ≤ 300
> 260 ≤ 280
> 230 ≤ 260
> 215 ≤ 230
> 200 ≤ 300
> 180 ≤ 200
> 165 ≤ 180
> 160 ≤ 165
> 135 ≤ 200
> 120 ≤ 135
> 100 ≤ 135
Temperature class
NEC 500-3
CEC 18-052
T1
T2
T2A
T2B
T2C
T2D
T3
T3A
T3B
T3C
T4
T4A
T5
> 85 ≤ 100
85
T6
Examples for the Classification of Gases and Vapours into Explosion Groups and Temperature Classes
I
II A
T1
Methane
T2
T3
T4
Acetone
Ethane
Ethyl ethanoate
Ethanol
i-Amyl acetate
n-Butane
Benzine
Diesel fuel
Aircraft fuel
Acetaldehyde
Ethylether
Ammonia
n-Butyl alcohol
Heating oils
Benzol (pure)
Ethanoic acid
Carbon oxide
T5
T6
n-Hexane
Methane
Methanol
Propane
Toluene
II B
II C
Coal gas
(lighting gas)
Hydrogen
Ethylene
Acetylene
Carbon disulphide
12
3
Type of protection
in accordance with
IEC or EN
Basic principle
Flameproof
enclosure
d
IEC 60 079-1
EN 50 018
Parts which can ignite a potentially explosive
atmosphere are surrounded by an enclosure
which withstands the pressure of an explosive
mixture exploding inside the enclosure and prevents the propagation of the explosion to the
atmosphere surrounding the enclosure.
Switchgear and control
gear and indicating
equipment, control
systems, motors, transformers, heating equipment, light fittings
Increased
safety
e
IEC 60 079-7
EN 50 019
Additional measures are taken to increase the
level of safety, thus preventing the possibility of
unacceptably high temperatures and the creation
of sparks or electric arcs within the enclosure or
on exposed parts of electrical apparatus parts,
where such ignition sources would not occur
under normal operation.
Terminal and connection
boxes, control boxes for
installing Ex-components
(which have a different
type of protection), squirrel-cage motors, light fittings
Pressurized
apparatus
p
IEC 60 079-3
EN 50 016
The formation of a potentially explosive
atmosphere inside a casing is prevented by maintaining a positive internal pressure of inert gas in
relation to the surrounding atmosphere and,
where necessary, by supplying the inside of the
casing with a constant flow of inert gas which
acts to dilute any combustible mixtures.
Switchgear and control
cabinets, analysers,
large motors
Intrinsic safety
i
IEC 60 079-11
EN 50 020
Apparatus used in a potentially explosive area
contain intrinsically safe electric circuits only. An
electric circuit is intrinsically safe if no sparks or
thermal effects are produced under specified test
conditions (which include normal operation and
specific fault conditions) which might result in the
ignition of a specified potentially explosive atmosphere.
Measurement and control
technology, communication technology, sensors,
actuators
Oil immersion
o
IEC 60 079-6
EN 50 015
Electrical apparatus or parts of electrical
apparatus are immersed in a protective fluid
(such as oil), such that a potentially explosive
atmosphere existing over the surface or outside
of the apparatus cannot be ignited.
Transformers, starting
resistors
Powder filling
q
IEC 60 079-5
EN 50 017
Filling the casing of an electrical apparatus with a
fine granular packing material has the effect of
making it impossible for an electric arc created in
the casing under certain operating conditions to
ignite a potentially explosive atmosphere
surrounding the casing. Ignition must not result
either from flames or from raised temperature on
the surface of the casing.
Transformers, capacitors,
terminal boxes for
heating conductors
Encapsulation
m
IEC 60 079-18
EN 50 028
Parts which may ignite a potentially explosive
atmosphere are embedded in sealing compound
such that the potentially explosive atmosphere
cannot be ignited.
Switchgear with small
capacity, control and signalling units, display units,
sensors
Type of protection
n
IEC 60 079-15
EN 50 021
Electrical apparatus is not capable of igniting a
potentially explosive atmosphere
(under normal operation and under defined
abnormal operating conditions).
Diagram
13
Zone 2
This type of protection includes several methods of
ignition protection.
Main application
All electrical apparatus
for Zone 2, less suitable
for switchgear and control gear
3.3.1 Application and Combination of
Types of Protection ”d” and ”e”
The most important type of protection for switchgear is
”Flameproof Enclosure”, usually in conjunction with “Increased Safety”. Switchgear does produce sources of ignition in normal use and therefore ”Increased Safety” alone is
not applicable as type of protection for switchgear, since
”Increased Safety” is based on the principle to avoid sources of ignition by additional measures. However, ”Increased
Safety”, in conjunction with ”Flameproof Enclosure”, cut a
great figure for switchgear and control gear.
3717-P
Modern, explosion protected luminaires also use a combination of several types of protection to achieve the best results
with regard to safety, function and economy.
2-pin lampholder
Electronic ballast
Terms and Definitions
Intrinsically safe electrical circuit
An electric circuit in which neither a spark nor the effect of
heat can cause a certain explosive atmopshere to ignite.
Intrinsically safe electrical apparatus
Electrical apparatus in which all circuits are intrinsically
safe.
Associated electrical apparatus,
Electrical apparatus which contains circuits some of which
are intrinsically safe and some are not, and which is
designed such that the non-intrinsically safe circuits cannot
negatively influence the intrinsically safe circuits.
Minimum ignition energy
The minimum ignition energy of a gas/air and vapour/air
mixture is the smallest level of electrical energy which
occurs while a capacitor is discharging and which may still
be sufficient to ignite the most ignitable mixture of a gas or
vapour and air at atmospheric pressure and 20°C. (This is
tested using the spark test apparatus in accordance with
EN 50 020 Appendix B).
Intrinsically safe electrical apparatus and intrinsically safe
components from related equipment are classified according to categories ia or ib. Equipment from category ”ia” is
suitable for use in Zone 0, and equipment from category ”ib”
for use in Zone 1.
Switch
Category ”ia”
Category ”ia” electrical apparatus
shall not be capable of causing ignition under normal operation and if
one fault occurs or if a combination
of any two faults occurs.
Category ”ib”
Electrical apparatus from category
”ib” shall not be able to cause the
ignition of one substance during normal operation or in the event of one
fault.
Safety factor 1.5:
Safety factor 1.5:
during normal operation and with
during normal operation and with
one fault
8 W lamp, G 5 2-pin cap
Terminals
one fault
3994-P
Safety factor 1.0:
Interior design of compact light fitting C-LUX 6100
two independent faults
3.3.2 Applications of Type of Protection ”Intrinsic Safety”
The type of protection ”Intrinsic Safety” is based on the
principle of current and voltage limitation within an electric
circuit. The energy from a power circuit capable of causing
an explosive atmosphere to ignite is thus limited to such an
extent that the surrounding explosive atmosphere cannot
ignite as a result of sparks or inadmissible surface heating of
the electrical components.
The type of protection ”Intrinsic Safety” is particularly used in
measurement and control technology, as no high currents,
voltage and capacities are required here.
14
Safety factor 1.0:
with one fault, if the electrical
apparatus does not have
unprotected switching contacts in
those components which may be
exposed to an explosive atmosphere,
and if the fault is monitored.
3
Intrinsically safe apparatus
Associated electrical apparatus
This contains intrinsically safe electric circuits only
This contains both intrinsically safe and non-intrinsically safe electric circuits
EEx ib IIC T6
[EEx ib] IIC T6
All necessary information is provided such as
category, gas group and temperature class.
The square brackets indicate that the associated electrical apparatus contains an intrinsically safe electric circuit which may be introduced into Zone 1, gas groups IIA, IIB and IIC.
The apparatus may be used in Zone 1.
The apparatus must be installed outside of
The apparatus may be used in zone 1 due to
the potentially explosive area.
installation in a flame-proof enclosure (”d”)
EEx de [ib] IIC T6
Isolation of Intrinsically Safe Circuits from non-intrinsically
Safe Circuits
An important measure for intrinsically safe circuits is the
safe isolation of all intrinsically safe circuits from non intrinsically safe circuits. Safe electric isolation is always required,
with the exception of safety barriers. One rule which applies
especially to Germany is that safety barriers are not permitted for the protection of intrinsically safe circuits in Zone 0.
Galvanic isolation is generally required for Zone 0.
Zener diodes, used for limiting voltage, as well as other
semiconductor components are considered to be susceptible to failure and must therefore be safeguarded by means
of redundant components. Wire wound or sheet resistors
for current limitation are considered to be infallible
components (they have high resistivity in the event of a fault).
Therefore one single component is sufficient.
Single fault safety:
In the event of the failure of one zener diode, a second zener
diode must take its function (Category ”ib”: one
redundant zener diode)
Double fault safety:
In the event of a failure of two zener diodes, a third zener
diode must take its function (Category ”ia”: two redundant
zener diodes)
4085-P
Temperature field station
15
4. Installation and Operation of Electrical Apparatus in Potentially Explosive Areas
Electrical apparatus must be selected and installed such that
it is protected against external influences which may
adversely affect the explosion protection.
4.1 Duties of Installer, Manufacturer and Operator
Safety in potentially explosive areas can only be guaranteed
by a close and effective working relationship amongst all
parties involved.
4.3 Methods of Installation
Essentially, three installation systems are used for electrical
facilities in hazardous locations:
User
The technical design of the electrical apparatus used with
the individual types of installation is accordingly different.
Sta
nda
rdi
zat
ion
Ins
tal
ler
r
ure
act
nuf
Ma
ty
ori
uth
gA
tin
Tes
Authority
1. Cable system with indirect entry
2. Cable system with direct entry
3. Conduit system
The operator is responsible for the safety of his equipment. It is
his duty to judge where there is a risk of explosion and then
divide areas into Zones accordingly. He must ensure that the
equipment is installed in accordance with regulations and is
tested before initial use. The equipment must be kept in a fit
state by regular inspection and maintenance.
The installer must observe the installation requirements and
select and install the electric apparatus correctly for its intended use.
Manufacturers of explosion protected apparatus are responsible for routine testing, certification and documentation and are
required to ensure that each device manufactured complies
with the design tested.
4.2 Classification into Zones and Selection of
Apparatus
The question of possible risks of explosion must be
addressed at the early stages of planning a new facility.
When classifying potentially explosive areas, the influence
of natural or artificial ventilation must be considered in
addition to the levels of flammable materials being released.
Furthermore, the classification figures relating to explosion
technology must be determined for the flammable materials
being used (see Appendix 6.2). Only then a decision can be reached on the division of potentially explosive areas into Zones
and the selection of suitable apparatus. IEC 60 079-14 (DIN 60
079-14) applies to the installation of electrical apparatus in
potentially explosive areas Group II.
Equipment shall only be used within the ambient temperature
range stipulated in its marking. If the marking does not contain any information, the standard range of between -20°C
and +40°C does apply.
Electrical apparatus with the types of protection ”d” and ”i”
must correspond to a subgroup IIA, IIB or IIC.
16
3023-P
The installation systems worldwide;
left: Cable system with indirect entry
centre: Cable system with direct entry
right: Conduit system
Only the conduit system or mineral insulated cables (MI) are
permitted in the USA for all applications in Class 1, Division 1
in accordance with NEC 501-4, whereby the mineral insulated cables are mainly used as heating lines and fire resistant
signal and control lines. Certain types of cable and line are
also permitted in Division 2. A comparison of the various
systems is shown below.
Cable systems
Cable systems are mainly used in Europe. For this, high-quality cables and lines are laid uncovered. It is only in areas in
which mechanical damage could be expectd that they are laid in
conduits which are open at both ends.
In the case of indirect entry, the cables and lines are
conducted via cable entrances into a wiring space in the type
of protection ”Increased safety” and connected to the terminals also provided in ”Increased Safety”. From here, the individual wires are conducted via flameproof line ducts into the
flame proof enclosure.
The line ducts are installed by the manufacturer, with the
result that, by contrast with direct entry, a routine test of the
factory wired flame proof enclosure can be made.
The installation engineer need only open the wiring space for
the connection, not the flameproof enclosure with factory
wiring.
4
In the case of direct entry, the connecting lines are
conducted directly into the flameproof enclosure. Only cable
glands which have been specially certified for this purpose
may be used for this type of entry. The flexible gasket and the
cable sheath must form a gap through which no flames can
penetrate. For this reason, attention must be paid to the appropriate selection of cable union depending on both the type and
structure of cable and installation location. The flame proof
enclosure primarily depends here on the care taken by the
installation engineer when laying the cables and lines.
Conduit system
In the case of installation using the conduit system, the electrical lines are drawn as single wires into enclosed metal
tubes. The tubes are connected to the housings by means of
unions and equipped with a seal at each entrance point.
The entire conduit system is flame proof.
The aim of the seal is to prevent explosions which may occur
inside the housing from penetrating the pipeline. Otherwise
extremely high explosive pressures would be created as a
result of pre-compression in long cylindrical tubes. For this
reason, it is recommended that seals be installed not just at
the entrance points but at specific intervals. Drains must be
installed at low points at which condensate can accumulate.
4.4 Repair and Maintenance
Regular maintenance is required to maintain the safety of
electrical facilities in hazardous locations.Personnel who
carry out such maintenance and repair work should work
under the guidance of an explosion protection specialist and
should be informed of the particular dangers involved.
Before carrying out any modification and repair work, it must
be ensured that there is no danger of explosions occurring
during this work. Normally, formal written permission for this
should be acquired from the company management. On
completion of the work, a record should be kept of what work
was carried out, and confirmation given that all relevant
regulations have been observed.
A relevant specialist should check any extensive modifications which may have a negative effect on the explosion
protection. This is not necessary if the manufacturer of the
apparatus concerned has carried out the modification.
When exchanging components or fully assembled
apparatus, the explosion and device-related characterisitc
data should be noted. Only original parts from the
manufacturer should be used.
Non-asbestos packing fiber
Sealing compound
Seal for horizontal installation – without drain
Wires
Close-up plug
Drain channel formed
in compound
non-asbestos
packing fiber
Sealing compound
Drain
Conduit
Seal for vertical installation – with drain
17
5. Explosion Protection in North America
5.1 Introduction
The basic principles of explosion protection are the same all
over the world. However, technologies have developed in North
America in the field of explosion protection for electrical
equipment and installations which deviate considerably from
those of the IEC (International Electrotechnical Commission).
The differences from IEC technologies are among others the
classification of hazardous locations, the construction of
apparatus and the installation of electrical systems.
5.2 Classification of Hazardous Locations
For potentially explosive atmospheres the term ”hazardous
(classified) locations” is used in North America. They are
defined in Articles 500 and 505 of the National Electrical Code
(NEC) in the USA and in Section 18 and Annex J of the Canadian Electrical Code (CEC) in Canada.The hazardous locations are those locations, where fire or explosion hazards may
exist due to flammable gases, vapours or liquids (Class I),
combustible dusts (Class II), or ignitable fibers or flyings
(Class III).
Based on the likelihood or risk that an ignitable concentration of a flammable material will be present the hazardous
locations are traditionally subdivided into Division 1 and Division 2.
In 1996 the IEC classification system was introduced as a
parallel system to the existing system for Class I in the USA.
This system was implemented by the new Article 505. This
now gives the end user the possibility to choose the system
which best suits his needs.
The IEC zone classification for Class I was also introduced in
Canada (CEC, 1988 edition). All newly built facilities in
Canada need to be classified according to this principle.
5.3 Regulations for Installation
The National Electrical Code in the USA and the Canadian
Electrical Code in Canada apply to electrical apparatus and
installations for hazardous locations.
These have the character of installation regulations for electrical facilities in all locations and refer to a number of further
standards of other institutions which contain specifications
for the installation and construction of suitable equipment.
The methods of installation for the zone concept in accordance with the NEC are similar to the traditional Class/Division
system. New to the NEC 1996 is the use of listed Metal Clad
(MC) cables in addition to rigid conduit and Mineral Insulated
cables in Class I, Division 1 or Zone 1.
One significant advantage of the CEC is the increased
possibility of using wires and cables. In contrast to the USA,
Canada has, for some time now, also permitted the use
of special cables similar to the IEC steel-wire armoured
cables.
5.4 Constructional Requirements
The regulations of the National Electrical Code and the
Canadian Electrical Code stipulate which apparatus and
methods of protection may be used in different hazardous
locations.
Various standards and regulations govern the construction
and testing of explosion-protected electrical apparatus and
installations in North America. In the USA, these are mainly
the standards issued by Underwriters Laboratories Inc. (UL),
Factory Mutual Research Corporation (FM) and the International Society for Measurement and Control (ISA). In
Canada, those of the Canadian Standards Association (CSA)
apply.
The traditional North American classification system divides
Class I flammable gases, vapours, mists and liquids into Gas
Groups A, B, C and D and Class II combustible dusts into
Groups E, F and G.
The tables in appendix 6.4 provide an overview of the
constructional requirements for hazardous locations and
methods of protection.
Group A is the most hazardous gas group in the traditional
NEC system whereas Group IIC is the most volatile in the IEC
system in Article 505 of the NEC.
5.5 Degrees of Protection provided by Enclosures
The standard IEC 60 529 defines the degrees of protection
provided by enclosures. In the USA the degrees of protection are included in the NEMA Publication No. 250 (National
Electrical Manufacturing Association). These enclosure
types could not be exactly equated with the IEC enclosure
classification designation since NEMA additional environmental influences (such as cooling lubricant, cutting coolant, corrosion, iceing, hail) takes into account.
In Canada both gas grouping systems may be used with the
zone classification system.
The maximum surface temperature classification given in the
new Article 505 maintains a pure IEC approach of having six
main temperature classes T1 to T6. This deviates from the
traditional NEC temperature class structure which has further subdivisions between the main temperature classes.
In the 1998 CEC this traditional structure T1-T6 with intermediate subdivisions was maintained.
18
IEC Enclosure Classification
1
2
IP 10
IP 11
3
3R
IP 54
IP 14
3S
4 and 4X
IP 54
IP 56
5
6 and 6P
IP 52
IP 67
12 and 12K
13
IP 52
IP 54
(2) Zone Equipment: Equipment
meeting one or more of the protection techniques described in
Article 505 of the NEC or Section
18 of the CEC shall be marked with
the following in the order shown:
1. Class (optional in Canada)
2. Zone (optional in Canada)
3. AEx (USA) or Ex or EEx (Canada)
4. Method(s) of protection
5. Equipment group II or applicable gas group(s) IIA, IIB or IIC
6. Temperature class
Example: Class I Zone 0 AEx ia IIC T6
5
NEMA Enclosure
Type Numbers
Note:
As the NEMA Types meet or exceed the test requirements for the associated IEC
Classifications the table cannot be used to convert from IEC Classifications to NEMA
Types.
5.6 Certification and Marking
In the USA and Canada, electrical apparatus and apparatus
used in hazardous locations are, as a rule, subject to approval. Exceptions to this are items of electrical apparatus
which, due to their design and the type of the explosive
atmosphere in which they operate, cannot create sparks.
The responsible authorities shall decide whether such
equipment is subject to approval.
Equipment which has been developed and manufactured for
use in hazardous locations is tested and approved in the USA
and Canada by a recognized testing laboratory. In the USA,
this is for example the Underwriters Laboratories or Factory
Mutual and in Canada the Canadian Standards Association.
In addition to data such as manufacturer, model, serial number
and electrical data, any data relating to explosion protection
must be shown on the marking of the equipment. The requirements for this are specified in the NEC, the CEC as well as the
relevant construction regulations of the testing authority.
Class I, II & III, Division 1 and 2
The approved electrical equipment for Class I, Class II and
Class III, Division 1 and Division 2 must be marked to show
the following information:
1. Class(es), Division(s) (optional except for Division 2)
2. Gas/dust group(s)
3. Operating temperature or temperature class (optional T5
and T6
Example: Class I Division 1 Groups C D T6
Class I, Zone 0, 1 and 2
For equipment intended for use in Class I, Zone 0, Zone 1 or
Zone 2, a distinction is made between ”Division Equipment”
and ”Zone Equipment”.
(1) Division Equipment: Equipment approved for Class I,
Division 1 and/or Class I, Division 2 shall be permitted to be
marked with the following in addition:
1. Class I, Zone 1 or Class I, Zone 2 (as applicable)
2. Gas group(s) IIA, IIB or IIC
3. Temperature class
Example: Class I Zone 1 IIC T4
19
4244-P
Control and Signal Station
ConSig 8040
6. Appendix
6.1 Comparison of IEC Publications and European Standards (EN)
Electrical Apparatus for Explosive Gas Atmospheres
IEC publications
IEC 60079-0
EN
EN 50 014
General requirements
IEC 60079-1
IEC 60079-1A
EN 50 018
-----
Construction and verification test of flameproof enclosures of electrical apparatus
Method of test for ascertainment of maximum experimental safe gap
IEC/TR 60079-2
IEC 60079-3
EN 50 016
EN 50 020
Electrical apparatus, type of protection ’p’
Spark-test apparatus for intrinsically-safe circuits
IEC 60079-4
IEC 60079-4A
-----
Method of test for ignition temperature
IEC 60079-5
IEC 60079-6
EN 50 017
EN 50 015
Powder filling ’q’
Oil-immersion ’o’
IEC 60079-7
IEC 60079-10
IEC 60079-11
EN 50 019
EN 60079-10
EN 50 020
Increased safety ’e’
Classification of hazardous areas
Intrinsic safety ’i’
IEC 60079-12
EN 50 014
Classification of mixtures of gases or vapours with air according to their maximum experimental safe gaps and minimum ignition currents
IEC/TR 60079-13
IEC 60079-14
IEC 60079-15
IEC/TR 60079-16
IEC 60079-17
IEC 60079-18
----EN 60079-14
pr EN 50 021
EN 60079-17
EN 50 028
Construction and use of rooms or buildings protected by pressurization
Electrical installations in hazardous areas (other than mines)
Electrical apparatus with type of protection ’n’
Artificial ventilation for the protection of analyser(s) houses
Inspection and maintenance of electrical installations in hazardous areas (other than mines)
Encapsulation ’m’
IEC 60079-19
IEC/TR 60079-20
prEN 60079-19
-----
Repair and overhaul for apparatus used in potentially explosive atmospheres (other than mines or explosives)
Data for flammable gases and vapours, relating to the use of electrical apparatus
Electrical Apparatus for Use in the Presence of Combustible Dust
IEC publications
EN
IEC 61241-1-1
-----
IEC 61241-1-2
-----
IEC 61241-2-1
-----
IEC 61241-2-2
EN 61241-2-2
IEC 61241-2-3
-----
IEC 61241-3
-----
Part 1: Electrical apparatus protected by enclosures
Section 1: Specification for apparatus
Part 1: Electrical apparatus protected by enclosures
Section 2: Selection, installation and maintenance
Part 2: Test methods
Section 1: Methods for determining the minimum ignition temperatures of dust
Part 2: Test methods
Section 2: Method for determining the electrical resistivity of dust in layers
Part 2: Test methods
Section 3: Method for determining minimum ignition energy of dust/air mixtures
Part 3: Classification of areas where combustible dust are or may be present
20
6
6.2 Safety Ratings of Flammable Gases and Vapours
Material
1,2-dichloroethane
Ignition temperature °C
440
Temperature class
T2
Gas group
II A
Acetaldehyde
Acetone
140
540
T4
T1
II A
II A
Acetylene
Ammonium
305
630
T2
T1
II C (3)
II A
Benzins, petrol fuels
Boiling point < 135 °C
220 to 300
T3
II A
Benzole (pure)
Cyclohexan0ne
555
430
T1
T2
II A
II A
Diesel fuels (DIN 51601)
Jet fuels
Acetic acid
220 to 300
220 to 300
485
T3
T3
T1
II A
II A
II A
Acetic anhydride
Ethane
330
515
T2
T1
II A
II A
Ethyl ethanoate
Ethanol
460
425
T1
T2
II A
II A / II B
Ethyl chloride
Ethene
Ethylene oxide
Diethyl ether
Ethyl glycol
EL fuel oil (DIN 51603)
L fuel oil (DIN 51603)
M and S fuel oils (DIN 51603)
i-Amyl acetate
Carbon monoxide
Methane
Methanol
Methyl chloride
Naphthalene
n-Butane
Butanol
n-Hexane
n-Propyl alcohol
Oleic acid
510
425
440 (self-decomposing)
170
235
220 to 300
220 to 300
220 to 300
380
605
595 (650)
455
625
540
365
340
240
405
360 (self-decomposing)
T1
T2
T2
T4
T3
T3
T3
T3
T2
T1
T1
T1
T1
T1
T2
T2
T3
T2
T2
II A
II B
II B
II B
II B
II A
II A
II A
II A
II A / II B
II A
II A
II A
II A
II A
II A
II A
-*)
-*)
Phenol
Propane
Carbon disulphide
595
470
95
T1
T1
T6
II A
II A
II C (1)
Hydrogen sulphide
Special benzines
Boiling point > 135 °C
270
200 to 300
T3
T3
II B
II A
Coal gas (lighting gas)
560
T1
II B
Tetralin
(1,2,3,4-tetrahydronaphthalene)
Toluol
425
T2
-*)
535
T1
II A
Hydrogen
560
T1
II C (2)
Extract from the tabular work ”Sicherheitstechnische Kennzahlen brennbarer Gase und Dämpfe [Safety ratings of
flammable gases and vapours]”
by K. Nabert and G. Schön - (6th edition)
-*) The gas group for this substance has not yet been determined.
(1) Also gas groups II B + CS2
(2) Also gas groups II B + H2
(3) Also gas groups II B + C2 H2
21
6.3 Classification of Hazardous Locations in North America
Gases, Flammable Vapours or Mists
Class I Area Classification
NEC 500-5
Combustible Dusts,
Class II Area Classification
Fibres and Ignitable Flyings
Class III Area Classification
NEC 500-7
CEC 18-010
NEC 505-7
CEC 18-006
NEC 500-6
CEC J18-004
Division 1
Locations where ignitable concen-
Zone 0
Locations where ignitable concen-
Division 1
Locations where ignitable concen-
trations of flammable gases,
vapours or liquids can exist all the
time or for long periods of time
trations of combustible dusts can
exist all the time or some of the time
t rations of flammable gases,
vapours or liquids can exist all the
time or some of the time under
normal operating conditions.
CEC 18-008
under normal operating conditions.
Division 1
Locations where ignitable fibres or
materials producing combustible
flyings are handled, manufactured
or used .
under normal operating conditions.
Zone 1
Locations where ignitable concentrations of flammable gases,
vapours or liquids can exist some of
the time under normal operating
conditions.
Division 2
Locations where ignitable concentrations of flammable gases,
vapours or liquids are not likely to
exist under normal operating
conditions.
Class I Groups
NEC 500-3
CEC J18-050
Zone 2
Locations where ignitable concentrations of flammable gases,
vapours or liquids are not likely to
exist under normal operating
conditions.
NEC 505-7
CEC 18-050
Divisions 1 and 2
A (acetylene)
B (hydrogen)
C (ethylene)
Zones 0, 1 and 2
IIC (acetylene + hydrogen)
D (propane)
IIA (propane)
IIB (ethylene)
Class I Temperature Classes
Division 2
Locations where ignitable concentrations of combustible dusts are
not likely to exist under normal operating conditions.
Division 2
Class II Groups
NEC 500-3
CEC 18-050
Class III Groups
Divisions 1 and 2
E (metal)
F (coal)
G (grain)
Divisions 1 and 2
none
Class II Temperature Classes
Class III Temperature Classes
Divisions 1 and 2
none
Divisions 1 and 2
T1 (≤450°C)
T2 (≤300°C)
Zones 0, 1 and 2
T1 (≤450°C)
T2 (≤300°C)
Divisions 1 and 2
T1 (≤450°C)
T2 (≤300°C)
T2A, T2B, T2C, T2D
(≤280°C, ≤260°C, ≤230°C, ≤215°C)
T3 (≤200°C)
-T3 (≤200°C)
T2A, T2B, T2C, T2D
(≤280°C, ≤260°C, ≤230°C, ≤215°C)
T3 (≤200°C)
T3A, T3B, T3C
--
T3A, T3B, T3C
(≤180°C, ≤165°C, ≤160°C)
T4 (≤135°C)
T4A (≤120°C)
T4 (≤135°C)
--
(≤180°C, ≤165°C, ≤160°C)
T4 (≤135°C)
T4A (≤120°C)
T5 (≤100°C)
T5 (≤100°C)
T5 (≤100°C)
T6 (≤85°C)
T6 (≤85°C)
T6 (≤85°C)
22
Locations where easy ignitable fibres are stored or handled.
6
6.4 Constructional Regulations for North America
Area
Type of ignition protection
Applicable standards for approval
UL
FM
CSA
Zone 0
• Intrinsically safe, ia (2 fault)
UL 2279, Pt. 11
FM 3610
CSA-E-79-11
• Class I, Div.1 intrinsically safe (2 fault)
ANSI/UL 913
FM 3610
• Encapsulation, m
• Flameproof, d
UL 2279, Pt. 18
UL 2279, Pt. 1
FM 3614 (ISA S12.23.01)
FM 3618 (ISA S12.22.01)
CSA-E-79-18
CSA-E-79-1
• Increased safety, e
• Intrinsically safe, ib (1 fault)
• Oil immersion, o
UL 2279, Pt. 7
UL 2279, Pt. 11
UL 2279
FM 3619 (ISA S12.16.01)
FM 3610
FM 3621 (ISA S12.26.01)
CSA-E-79-7
CSA-E-79-11
CSA-E-79-6
Zone 1
• Powder filling, q
UL 2279
FM 3622 (ISA S12.25.01)
CSA-E-79-5
• Purged pressurized, p
• Any Class I, Zone 0 method
• Any Class I, Div. 1 method
UL 2279, Pt. 2
---
(IEC 79-2)
---
CSA-E-79-2
---
• Nonincendive, nC
UL 2279, Pt. 15
(ISA S12.12.01, IEC 79-15)
CSA-E-79-15
• Non-sparking device, nA
• Restricted breathing, nR
• Hermetically sealed, nC
• Any Class I, Zone 0 or 1 method
• Any Class I, Div. 1 or 2 method
UL 2279, Pt. 15
UL 2279, Pt. 15
UL 2279, Pt. 15
---
(ISA S12.12.01, IEC 79-15)
(ISA S12.12.01, IEC 79-15)
(ISA S12.12.01, IEC 79-15)
---
CSA-E-79-15
CSA-E-79-15
CSA-E-79-15
---
Divison 1
• Explosionproof
• Intrinsically safe (2 fault)
• Purged/pressurized (Type X or Y)
ANSI/UL 1203
ANSI/UL 913
ANSI/NFPA 496
FM 3615
FM 3610
FM 3620
CSA 22.2 No. 30
CSA 22.2 No. 157
ANSI/NFPA 496
Division 2
• Nonincendive
• Non-sparking device
• Purged/pressurized (Type Z)
• Hermetically sealed
• Any Class I, Div. 1method
• Any Class I, Zone 0, 1 or 2 method
UL 1604
UL 1604
ANSI/NFPA 496
UL 1604
---
FM 3611
FM 3611
FM 3620
FM 3611
---
CSA 22.2 No. 213
CSA 22.2 No. 213
ANSI/NFPA 496
CSA 22.2 No. 213
---
Division 1
• Dust-ignition proof
ANSI/UL 1203
FM 3616
Class III
Class II
Class I
Zone 2
• Intrinsically safe
ANSI/UL 913
FM 3610
CSA 22.2 No. 25 or
CSA-E 1241-1-1
CSA 22.2 No.157
• Pressurized
ANSI/NFPA 496
FM 3620
ANSI/NFPA 496
• Dust tight
UL 1604
FM 3611
CSA 22.2 No. 25 or
• Nonincendive
• Non-sparking
• Pressurized
UL 1604
UL 1604
ANSI/NFPA 496
FM 3611
FM 3611
FM 3620
----ANSI/NFPA 496
• Any Class II, Div. 1 method
--
--
--
Division 1
• Dust tight
• Intrinsically safe
Ul 1604
ANSI/UL 913
FM 3616
FM 3611
CSA 22.2 No.157
CSA 22.2 No.157
Division 2
• Dust tight
UL 1604
FM 3611
CSA 22.2 N0.157
• Any Class II Div. 1 and Class III method
--
--
--
Division 2
CSA-E 1241-1-1
23
6.5 Ingress Protection Codes in accordance with IEC 60 529 - IPXX
Table 1: Scope of Protection for the IP Protection Classes
Digit
First digit
Physical protection
Foreign body protection
Second digit
Water protection
0
1
No protection
Protection against back of hand contact
No protection
Protection against solid foreign bodies
No protection
Protection against water drops falling vertically
2
Protection against finger contact
50 mm diameter
Protection against solid foreign bodies
Protection against contact from tools
12.5 mm diameter
Protection against solid foreign bodies
Protection against water-spray at an angle up to 60°
Protection against contact with a wire
2.5 mm diameter
Protection against solid foreign bodies
Protection against water spray from all directions
5
Protection against contact with a wire
1.0 mm diameter
Protection against dust
Protection against water jets
6
7
Protection against contact with a wire
-
Dust-tight
-
Protection against strong water jets
Protection against intermittent immersion in water
8
-
-
Protection against continuous immersion in water
3
4
Protection against water drops falling at an
angle (15°)
6.6 Degree of Protection provided by Enclosures according to NEMA
(Publication No. 250 Enclosures for Electrical Equipment 1000 Volts Maximum)
Enclosure
Type
Type 1
Type 2
Type 3
Type 3R
Degree of Protection
Protection against limited amounts of falling dirt
Protectionn against limited amounts of falling water and dirt
Protection against rain, sleet, windblown dust, and damage for external ice formation
Protection against rain, sleet, and damage for external ice formation
Use
Indoor
Indoor
Outdoor
Outdoor
Outdoor
Indoor or Outdoor
Type 7
Protection against rain, sleet, windblown dust, and for operation of external mechanisms when ice laden
Protection against windblown dust and rain, splashing water, hose directed water, and damage from external ice
formation
Protection against corrosion, windblown dust and rain, splashing water, hose directed water, and damage from
external ice formation
Protection against settling airborne dust, falling dirt, and dripping noncorrosive liquids
Protection against hose directed water, the entry of water during occasional temporary submersion at a limited
depth, and damage from external ice formation
For use in locations classified as Class I, Groups A, B, C, or D as defined in the NEC
Type 8
Type 9
For use in locations classified as Class I, Groups A, B, C, or D as defined in the NEC
For use in locations classified as Class II, Groups E, F, G as defined in the NEC
Indoor or Qutdoor
Indoor
Type 10
Type 11
Constructed to meet the applicable requirements of the Mine Safety Health Administration
Protection against the corrosive effects of liquids and gases by oil immersion
Mining
Indoor
Type 12, 12K
Type 13
Protection against circulating dust, falling dirt, and dripping non corrosive liquids
Protection against dust, spraying of water, oil, and non corrosive coolant
Indoor
Indoor
Type 3S
Type 4
Type 4X
Type 5
Type 6
24
Indoor or Outdoor
Indoor
Indoor or Outdoor
Indoor
6.7 Overview of the most important Approval and Testing Authorities *
Country
Country
Approval authority
Testing authority
Australia
Quality Assurance Services
R Jacobi
Locked Bag 2032
STRATHFIELD NSW 2135
Tel: +61 2 9746 4900
Fax: +61 2 9746 8460
International Testing and Certification
Services (ITACS)
2 Second Street
BOWDEN S A 5007
Tel: +61 8 83468680
Fax: +61 8 83467072
TÜV Hannover/Sachsen-Anhalt e.V.
P.O.Box 81 05 51
D 30505 Hannover
Tel: +49 511 986 1552
Fax: +49 511 986 1590
FSA - Forschungsgesellschaft für angewandte
Systemsicherheit und Arbeitsmedizin mbH
Dynamostraße 7-11
D 68165 Mannheim
Tel: +49 621 44 56 36 06
Fax: +49 621 44 56 34 02
Safety in Mines Testing and Research
Station (SIMTARS)
2 Smith Street
REDBANK QLD 4075
Tel: +61 7 3810 6370
Fax: +61 7 3810 6366
Brazil
Canada
CENTRO DE PESQUISAS
DE ENERGIA ELETRICA (CEPEL)
Cx. Postal 2754
CEP 20001 Rio de Janeiro - RJ
Tel: +5521 598 2442
Fax: +5521 598 2443
Technical Research Centre of Finland (VTT)
Automation/Electrotechnical Testing
Otakaari 7B, Espoo
P.O. Box 13051
FIN 02044 Vtt
Tel: +358 9 4561
Fax: +358 9 4567042
France
Laboratoires Central des Industries
Electriques (LCIE)
33 avenue du Général Leclerc
F 92260 Fontenay-aux-Roses
Tel: +33 1 409 55519
Fax: +33 1 409 55520
Canadian Standards Association (CSA)
178 Rexdale Boulevard
Etobicoke, Ontario M9W 1R3
Tel: +416 747 4000
Fax: +416 747 4149
Institut National de l’Environnement Industriel
et des Risques (INERIS)
B Piquette
Parc Technologique ALATA - B.P.2
F-60550 Verneuil-En-Halatte
Tel: + 3 44 55 66 77
Fax: +3 44 55 66 99
E-Mail: [email protected]
Great
Britain
Centre for Explosion Protection and
Safety of Instrumentation (NEPSI)
103 Cao Bao Road
Shanghai
Tel: +21 643 86180
Fax: +21 643 335 66
Czech
Republic
Fyzikalne technicky zkusebni ustav (FTZU)
Statni zkusebna c. 210
CZ 71607 Ostrava-Radvanice
Tel: +42 69 6215484
Fax: +42 69 214860
Denmark
DEMKO
Lyskaer 8
DK-2730 HERLEV
Tel: +45 44 947 266
Fax: +45 44 947 261
Federal
Republic
of Germany
Finland
TÜV ÖSTERREICH
Krugerstraße 16
A 1015 Wien
Tel: +43 1 514 07 0
Fax: +43 1 514 07 240
CANMET
555 Booth Street
Ottawa, Ontario K1A 0G1
Tel: +613 947 6580
Fax: +613 947 4198
China
Testing authority
IBExU - Institut für Sicherheitstechnik GmbH
Institut an der Bergakademie Freiberg
Fuchsmühlenweg 7
D 09599 FREIBERG
Tel: +49 3731 3805 19
Fax: +49 3731 23650
WorkCover Authority of NSW
Londonderry Occupational Safety
919 Londonderry Road
LONDONDERRY NSW 2753
Tel: +61 47 244 900
Fax: +61 47 244 999
Austria
Approval authority
Electrical Equipment Certification Services (EECS)
Health and Safety Executive
Harpur Hill
BUXTON DERBYSHIRE SK17 9JN
Tel: +44 1 298 28000
Fax: +44 1 298 28244
Explosion and Fire Hazards Laboratory
ERA Technology Ltd
G R Oliver
Cleeve Road
LEATHERHEAD SURREY KT 7SA
Tel: +44 1372 367 000
Fax: +44 1372 367 099
SIRA Certification Service (SCS)
South Hill
M Shearman
CHISELHURST KENT BR7 5EH
Tel: +44 181 467 2636
Fax: +44 181 295 1990
Physikalisch-Technische
Bundesanstalt (PTB)
Bundesallee 100
D 38116 Braunschweig
Tel: +49 531 592 3400
Fax: +49 531 592 3405
Hungary
DMT - Gesellschaft für Forschung und Prüfung mbH
Fachstelle für Sicherheit elektrischer Betriebsmttel
Bergbau-Versuchsstrecke (BVS)
Beylingstr. 65
D 44329 DORTMUND
Tel: +49 231 2491 0
Fax: +49 231 2491 224
Italy
*) where no approval authority is given,
the testing authority is also the approval authority
25
SIRA Test and Certification Ltd
Saighton Lane
A J McMillan
GB - Chester CH3 6EG
Tel: +44 1244 332200
Fax: +44 1244 332112
Hungarian testing authority for explosion-proof
electrical apparatus (BKI)
Mikoviny S. u. 2-4
H 1037 Budapest
Tel: +36 1 168 7260
Fax: +36 1 250 1720
Centro Elettrotecnico Sperimentale Italiano (CESI)
Via Rubattino 54
I 20134 Milano
Tel: +39 2 212 53 72
Fax: +39 2 212 54 40
6
Country
Japan
Luxemburg
Netherlands
Approval authority
Testing authority
Country
The Technical Institution of Industrial Safety (TIIS)
1-4-6 Umezono Kiyose
Tokyo 204
Tel: +81 424 91 4514
Fax: +81 424 95 2461
Sweden
Service de l´Energie de l´Etat Luxembourgeois
B.P. 10
L 2010 Luxembourg
Tel: +352 46 97 48
Fax: +352 22 25 24
Switzerland
KEMA
Postbus 9035
NL 6800 ET ARNHEM
Tel: +31 26 3 56 34 28
Fax: +31 26 3 51 01 78
Norway
NEMKO
P O Box 73 Blindern
N 0314 OSLO
Tel: +47 22 960330
Fax: +47 22 698636
Poland
Glowny Institut Gornictwa
Kopalnia Doswiadczalna ”BARBARA”
ul. Podleska 72, skrytka pocztowa 72
PL 43-190 Mikolow
Tel: +58 2028 024 9
Fax: +58 2028 745
Ukraine
USA
Republic
Korea
Rebublic of
South Africa
Romania
Russia
INSEMEX PETROSANI
Equipment Ex. Certification Service
Str. Gen. Vasile Milea nr.32-34
Cod 2675 Petrosani.
Tel: +4 054 541 621
Fax: +4 054 232 277
Test centre for explosion-proof electrical apparatus (VNIIEF)
formerly Arzamas 16
Prospect Mira, 37
607190 Sarov
Tel: +831 30 45669
Fax: +831 30 45530
Slovenia
Mr Igor Likar
Slovenian Institute of Quality and Metrology (SIQ)
Trazaska cesta 2
SL-1000 Ljubljana
Tel: +386 61 177 8100
Fax: +386 61 177 8444
Spain
Yugoslavia
South African Bureau of Standards (SABS)
1 Dr. Lategan Road, Groenkloof, Pretoria
Private Bag X191
Pretoria 0001
Tel: +12 428 7911
Fax: +12 344 1568
Elektrotechnicky vyskumny a
projektovy ustav (EVPU)
Statna skusobna SKTC 101
SK 01851 Nova Dubnica
Tel: +
Fax: +
Testing authority
Swedish National Testing and
Research Institute (SP)
Brinellgatan 4
Box 857
S-501 15 BORAS
Tel: +46 33 16 5000
Fax: +46 33 13 5502
Eidgenössisches
Starkstrominspektorat (ESTI)
Luppmenstraße 1
CH 8320 FEHRALTORF
Tel: +41 1 956 12 12
Fax: +41 1 956 12 22
Schweizerischer Elektrotechnischer
Verein (SEV)
Luppmenstraße 1
CH 8320 FEHRALTORF
Tel: +41 1 956 11 11
Fax: +41 1 956 11 12
Test and certification centre for
explosion-proof and flame-proof
electrical apparatus (ISZ VE)
ul. Gvardeiskoi Divisii 17
340052 Donezk
Tel: +
Fax: +
Underwriters Laboratories Inc. (UL)
333 Pfingsten Road
Northbrook, IL 60062-2096
Tel: +847 272 8800
Fax: +847 272 8129
Factory Mutual Research Corporation (FM)
1151 Boston-Providence Turnpike
P.O. Box 9102
Tel: +781 255 4840
Fax: +781 762 9375
Korea Industrial Safety Corp. (KISCO)
34-4 Kusa-dong, Poopyoung-gu
Inchon 403-120
The Republic of Korea
Tel: +82 32 5100 865
Fax: +82 32 518 6483-4
Slovakia
Approval authority
Laboratorio Official Jose Maria
Madariaga (LOM)
Calle Alenzaa 1-2
E 28003 Madrid
Tel: +34 1 442 13 66
Fax: +34 1 441 99 33
26
SAVEZNO MINISTARSTVO ZA RAZVOJ,
NAUKU i ZIVOTNU SREDINU
SAVEZNI ZAVOD ZA
STANDARDIZACIJU (SZS)
Federal Ministry for Development,
Science and Environment
Federal Institution for Standardization
Kneza Milosa 20
YU Beograd
Tel: +11 681 999
Fax: +235 10 36
27
7. Literature
Directive 94/9/EU of the European Parliament and the council
of 23 March 1994 on the approximation of the laws of the
member states concerning equipment and protective sytems
intended for use in potentially explosive atmospheres
Official Journal of the European Communities
Second Order to the equipment safety law and amendments
to equipment safety law safety legislation dated 12.12.1996,
Federal Gazette 1996 Part I No. 65
Bulletin of the new edition of the Order on electrical
apparatus in potentially explosive areas dated 13.12.1996,
Federal Gazette 1996 Part I No. 65
Explosion protection of electrical apparatus; order on electrical
apparatus in potentially explosive areas (ElexV), commentary
and collected texts] Erich Schmidt Verlag, Berlin
DIN EN 60 079-14 VDE 0165 Part 1:1998-08
Electrical apparatus in areas prone to gas explosions
Electrical installations in hazardous areas
VDE-Verlag GmbH, Berlin
DIN VDE 0105 Part 9: 1986-05 Operation of high-voltage
equipment - supplementary specifications for potentially
explosive areas
VDE-Verlag GmbH, Berlin
Dust explosion protection on machines and apparatus, ISSA
Prevention Series No. 2033(G), Mannheim 1998
NFPA 70 - 1996 National Electrical Code, 1996 edition
National Fire Protection Association, Quincy, MA, USA
NFPA 70 - 1999 National Electrical Code, 1999 edition
National Fire Protection Association, Quincy, MA, USA
Code of practice for explosion protection (Ex-RL) - code of
practice for the avoidance of the dangers of potentially
explosive atmospheres with collected examples (ZH1/10)
BG-Chemie (1998)
Werbe-Druck Winter, Sandhausen
1998 Canadian Electrical Code, 18th edition
Canadian Standards Association, Etobicoke, ON, Canada
K. Nabert and G. Schön:
Safety ratings of flammable gases and vapours
Deutscher Eichverlag, Braunschweig
1998 Canadian Electrical Code Review and Application Guide
Hubbell Canada Inc. - Killark, Pickering, ON, Canada
Flammability and explosion parameters for dust
Berufsgenossenschaftliches Institut für Arbeitssicherheit
und Bergbau-Versuchsstrecke (1987)
Erich Schmidt Verlag, Bielefeld
D. Beermann, B. Günther, A. Schimmele: Intrinsic safety in
explosion-proof measurement and control systems - functions, selections, installation, operation.
VDE-Verlag GmbH, Berlin and Offenbach
H. Greiner: Explosion protection for three-phase geared
motors Druckschrift SD 393, Eberhard Bauer Motoren,
Esslingen 1993
G. Lüttgens, M. Glor: Understanding and safely controlling
electrostatic charges, Expert Verlag, Ehningen (1988)
DIN VDE 0170/0171 Part 1 ff.(EN 50 014 ff.) Electrical
apparatus for potentially explosive atmospheres
VDE-Verlag GmbH, Berlin
DIN VDE 0470 Part 1 (EN 60 529) IP-Schutzarten; Specification
for degrees of protection provided by enclosures (IP code)
VDE-Verlag GmbH, Berlin
DIN VDE 0165/02.91 Installation of electrical apparatus in
potentially explosive areas
VDE-Verlag GmbH, Berlin
28
1996 National Electrical Code Review and Application Guide
Killark Electric Manufacturing Company, St. Loius, MO, USA
8. Index
Associated electrical apparatus
ATEX 100a
ATEX 118a
14, 15
8
11
Basic health and safety requirements
8
BVS/DMT (Bergbauversuchsstrecke Dortmund) 25
Cable system
Categories (equipment categories)
CEC (Canadian Electrical Code)
CE marking
CENELEC
Certificate of conformity
Class
Components
Conduit system
Construction regulations
EUROPE
NORTH AMERICA
16, 17
11
18, 22
10
8
8, 9
18, 22
9
17
8
23
Danger Class
Declaration of conformity
Degree of protection (IP code)
Division
Dust
Dust explosion protection
6
9, 10
24
18, 22
11, 18
8
EC Directive
Electrical apparatus
EMC Directive
EN (European Standard)
Equipment
Equipment category
Equipment group
Explosion
Explosion limits
ExVo
8, 9
9
10
8, 20
9
11
Fault safety, sinle/double
Flame proof enclosure
Flash point
15
14
6
Galvanic isolation
Gas group
German Technical Regulations for Flammable
Liquids (TRbF)
Group
15
11, 21
IEC (International Electrotechnical Commission)
Ignition temperature
Increased safety
Installation systems
Intrinsic safety
8, 20
12, 21
14
16
14
Maintenance
Marking
MESG (maximum experimental safe gap)
MIC (minimum ignition current)
Minimum ignition energy
16, 17
10, 19
11
11
14
6, 11
6
10
6
18, 22
29
NEC (National Electrical Code)
18, 22
NEMA (National Electrical Manufacturing
Association)
18, 24
Potentially explosive area, hazardous location
Potentially explosive atmosphere
Primary explosion protection
Protective systems
PTB (Physikalisch-Technische Bundesanstalt)
9, 11, 16
9, 11
7
9
10, 25
Quality assurance
10
Routine testing
16
Safety barrier
Safety factor
Secondary explosion protection
Sources of ignition
Special protection
Safety caracteristic
Surface temperature
15
14
7
6, 7
12
21
12, 18
Testing authority
Temperature class
Type examination certificate, EC
Types of protection
25, 26
11, 12, 18, 21, 22
10
12
Zener diode
Zones
15
11, 12, 18, 22
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