Explosion protection - Fundamentals - Siemens

Explosion protection 

Fundamentals 

Overview · April 2003

Introduction 

Table of Contents Page 

· Introduction 2 

· Fundamental physical principles and definitions 3 

· Legislative basis and standards 5 

· Classification of explosion-protected equipment 7 

· Intrinsic safety 11 

· Setting up and operating electrical systems 12 

· Ex protection in North America 

Comparison of zones/divisions 

· Safety ratings 16 

· Approval and test centers 17 

· Distributed I/O devices 

- ET 200 ® iS 

- ET 200M 

In many industries, the manufacture, 

processing, transport, or storage of 

combustible materials results in the creation, 

or release into the surrounding 

environment, of gases, vapors, or mist. 

Other processes create combustible 

dust. The gases, vapors, dust, and mist 

created in these processes form an explosive 

atmosphere in conjunction with 

the oxygen in the air that could result in 

an explosion if ignited. 

Particularly in areas such as the chemical 

and petrochemical industries, the 

transport of crude oil and natural gas, 

the mining industry, milling (e.g. grain, 

granular solids), and many other 

branches of industry, explosions can occur, 

causing serious injury to personnel 

and damage to equipment. 

15 

19 

20 

To prevent explosion hazards, most 

countries have developed protection 

rules in the form of legislation, standards, 

and regulations. These rules are 

designed to guarantee a high level of 

safety. As a result of increasing globalization 

of the markets and more intensive 

economic cooperation among different 

countries, laws in the large economic 

groupings of the world such as 

Europe and North America have been 

harmonized to a large degree. 

Within the framework of the European 

Union, explosion protection regulations 

have been brought together in Directive 

9/94/EC. This Directive will come into 

force on 30.06.2003. 

Global harmonization of legislation into 

a uniform regulation is still a long way 

off. 

References 

Directive 94/9/EC of the European Parliament and Council of 23 

March 1994 on the approximation of the laws of the Member States 

concerning equipment and protective systems intended for use in 

potentially explosive atmospheres 

Official Journal of the European Communities, No. L 100/1 

K. Nabert and G. Schön: 

Safety ratings of flammable gases and vapors 

Published by Deutscher Eichverlag, Brunswick 

DIN VDE 0170/0171 Part 1 ff. (EN 50014 ff.) 

Electrical apparatus for potentially explosive atmospheres 

DIN VDE 0470 Part 1 (EN 60529) 

IP degrees of protection; protection against touch, and the ingress 

of solid foreign objects and water for electrical equipment 

DIN VDE 0165/02.91 

Installation of electrical apparatus in hazardous areas 

DIN EN 60079-14 VDE 0165 Part 1:1998-08 

Electrical apparatus for explosive gas atmospheres 

Electrical installations in hazardous areas 

Published by VDE-Verlag GmbH, Berlin 

NFPA 70 - 1996 National Electrical Code, 1996 

National Fire Protection Association, Quincy, MA, USA 

NFPA 70 -1999 National Electrical Code, 1999 

National Fire Protection Association, Quincy, MA, USA 

1998 Canadian Electrical Code, 18th Edition 

Canadian Standards Association, Etobicoke, ON, Canada 

1996 National Electrical Code Review and Application Guide 

Killark Electric Manufacturing Company, St. Louis, MO, USA 

1998 Canadian Electrical Code Review and Application Guide 

Hubbell Canada Inc. - Killark, Pickering, ON, Canada 

Brochure 

Basics of Explosion Protection 

R. STAHL SCHALTGERÄTE GMBH, 

Waldenburg 

The brochure "Explosion Protection 

Fundamentals" is designed to provide 

users and interested readers with an 

overview of explosion protection in conjunction 

with electrical equipment and 

systems. 

As well as providing an overview, it is 

also intended as an aid to interpreting 

and decoding device labels and as a reference 

work. 

However, it does not replace intensive 

study of the relevant fundamentals and 

guidelines when planning and installing 

such systems. 

The drafting and creation of regulations 

and standards have their origins in the 

United Kingdom where miners were 

threatened by the hazard of fire damp 

right from the start.The result is an extremely 

high level of safety in the industrialized 

nations today. 

2 2

Fundamental physical principles and definitions 

An explosion is the sudden chemical reaction 

of a combustible substance with 

oxygen, involving the release of high 

energy. Combustible substances can be 

present in the form of gases, mist, vapor, 

or dust. An explosion can only take 

place if the following three factors coincide: 

1. Combustible substance (in the relevant 

distribution and concentration) 

2. Oxygen (in the air) 

3. Source of ignition (e.g. electrical 

spark) 

Fig. 1 Explosion 

Combustible 

substance 

Explosion 

Oxygen Ignition source 

When considering safety-related factors, 

it is necessary to know certain 

characteristic quantities of these materials. 

The flash point for flammable liquids 

specifies the lowest temperature at 

which a vapor-air mixture forms over 

the surface of the liquid that can be ignited 

by a separate source. If the flash 

point of such a flammable liquid is significantly 

above the maximum ocurring 

temperatures, a potentially explosive 

atmosphere cannot form there. However, 

the flash point of a mixture of different 

liquids can also be lower than the 

flash point of the individual components. 

In technical regulations, flammable liquids 

are divided into four hazard classes: 

Hazard class Flash point 

AI 55 to 100 °C 

B < 21°C, soluble in 

water at 15°C 

Combustible substances form a potentially 

explosive atmosphere when they 

are present within a certain range of 

concentration (see Fig.2). 

If the concentration is too low 

(lean mixture) and if the concentration 

is too high (rich mixture) an explosion 

does not take place. Instead slow burning 

takes place, or no burning at all. 

Only in the area between the upper and 

the lower explosion limit does the mixture 

react explosively if ignited. 

Fig. 2 Area subject to explosion hazard 

Substance designation Lower explosion limit 

[Vol. %] 

The explosion limits depend on the surrounding 

pressure and the proportion 

of oxygen in the air 

(see the table below). 

We refer to a deflagration, explosion, or 

detonation, depending on the speed of 

combustion. A potentially explosive atmosphere 

is present if ignition represents 

a hazard for personnel or materials. 

A potentially explosive atmosphere, 

even one of low volume, can result in 

hazardous explosions in an enclosed 

space. 

100 Vol % Air concentration 0 Vol % 

Mixture 

too lean 

No 

combustion 

Area subject to explosion Mixture 

too rich 

lower explosion limit upper 

Partial 

deflagration 

No 

explosion 

0 Vol % Concentration of 

combustible substance 

100 Vol % 

Upper explosion limit 

[Vol. %] 

Acetylene 2.3 78.0 (self-decomposing) 

Ethylene 2.3 32.4 

Petrol ~ 0.6 ~ 8 

Benzol 1.2 8 

Natural gas 4.0 (7.0) 13.0 (17.0) 

Heating oil/diesel ~ 0.6 ~ 6.5 

Methane 4.4 16.5 

Propane 1.7 10.9 

Carbon bisulphide 0.6 60.0 

City gas 4.0 (6.0) 30.0 (40.0) 

Hydrogen 4.0 77.0 

Explosion limits of combustible substances 

3 3

Fundamental physical principles and definitions 

Ignition source 

The application of a certain amount of 

energy is required to ignite a potentially 

explosive atmosphere. 

The minimum energy is taken to be the 

lowest possible converted energy, for 

example, the discharge of a capacitor, 

that will ignite the relevant flammable 

mixture. 

The minimum energy lies between approximately 

10 -5 J for hydrogen, and 

several Joules for certain dusts. 

What can cause ignition? 

· Hot surfaces 

· Adiabatic compression 

· Ultrasound 

· Ionized radiation 

· Open flames 

· Chemical reaction 

· Optical radiation 

· Electromagnetic radiation 

· Electrostatic discharge 

· Sparks caused mechanically 

by friction or impact 

· Electrical sparks and arcs 

Primary and secondary explosion 

protection 

Protective measures can be taken 

against explosions. A distinction is 

made here between primary and secondary 

protective measures. 

Primary explosion protection covers all 

measures that prevent the formation of 

a potentially explosive atmosphere. 

What form can these protective measures 

take? 

· Avoidance of combustible substances 

· Inerting (addition of nitrogen, carbon 

dioxide, etc.) 

· Limiting of the concentration 

· Improved ventilation 

4 

Minimum ignition energy 

Rare 

Rare 

Rare 

Gases Dusts 

Practice-oriented 

ignition source 

Fig. 3 Comparison of the minimum energy of gases and dusts 

with practice-oriented ignition sources 

Integrated 

explosion protection 

Prevent the formation 

of potentially 

explosive 

atmospheres 

Prevent the ignition 

of potentially 

explosive 

atmospheres 

Resrict the effects 

of an explosion 

to a negligible 

level 

Fig. 4 Integrated explosion protection 

-Welding sparks 

- Sheaf of impact 

sparks in mills 

- Sheaf of grinding 

sparks 

- electrostatic 

discharges 

- Impact sparks 

Secondary explosion protection is 

required if the explosion hazard cannot 

be removed or can only be partially 

removed using primary explosion 

protection measures. 

The principle of integrated explosion 

protection requires all explosion protection 

measures to be carried out in 

a defined order.

Legislative basis and standards 

Legislative basis of explosion protection 

Globally, explosion protection is regulated 

by the legislatures of the individual 

countries. National differences in technical 

requirements and the required approvals 

for explosion-protected devices 

are a significant hindrance to trade primarily 

for global players, and they require 

considerable overhead in development 

and approval testing. For some 

time now, particularly among the leading 

industrial nations, there has therefore 

been interest in removing barriers 

to trade by harmonizing the appropriate 

technical standards, and in implementing 

uniform safety standards in parallel. 

Within the European Community, the 

harmonization process in the area of explosion 

protection is largely complete. 

At the international level, the IEC is attempting 

to get closer to the aim of "a 

single global test and certificate" by introducing 

the IECEx Scheme. 

EC directives 

In the European Community, explosion 

protection is regulated by directives and 

laws. 

Electrical equipment for use in potentially 

explosive atmospheres must 

therefore possess test certification. The 

relevant systems and equipment are 

graded as systems requiring monitoring 

and must only use devices approved for 

this purpose. In addition, commissioning, 

modification, and regular safety inspections 

must only be accepted or carried 

out by approved institutions or societies. 

The EC directives are binding for all 

Member States and form the legal 

framemork. 

Short name Full text Directive no. Valid from End of 

transition 

period 

Low-voltage 

Directive 

Council Directive of 19 February 1972 on the approximation of 

the laws of the Member States concerning electrical equipment 

for use within specific voltage limits 

73/23/EEC 19.08.74 01.01.97 

· Modification 93/68/EEC 01.01.95 01.01.97 

EMC Directive Council Directive of 3 May 1989 on the approximation of the 

laws of the Member states concerning electromagnetic compatibility 

89/336/EEC 01.01.92 31.12.95 

· Modification 92/31/EEC 28.10.92 - 

· Modification 93/68/EEC 01.01.95 01.01.97 

Machinery Directive Directive of the European Parliament and Council of 22 June 

1998 on the approximation of the laws and administrative regulations 

of the Member States concerning machinery 

EX Directive 

(ATEX 100a) 

Pressurized 

equipment Directive 

ATEX 137 

(old: ATEX 118a) 

Selection of important EC directives 

Directive of the European Parliament and Council of 23 March 

1994 on the approximation of laws of the Member States concerning 

equipment and protective systems intended for use in 


Directive 97/23/EC of the European Parliament and Council of 

29 May 1997 on the approximation of the laws of the Member 

States concerning pressurized equipment 

Minimum regulations for improving the health protection and 

safety of employees that could be endangered by potentially 

explosive atmospheres 

98/37/EC 

(based on 

89/392/EEC) 

01.01.93 31.12.94 

94/9/EC 01.03.96 30.06.03 

97/23/EC 29.11.99 29.05.02 

1999/92/EC 16.12.99 30.06.03 

5

Legislative basis and standards 

National laws and regulations 

In general, the EC directives are European 

law that must be incorporated by the 

individual member states unmodified 

and "one-to-one" by ratification. Directive 

94/9/EC was adopted completely 

into the German explosion protection 

regulation ExVO. The underlying legislation 

for technical equipment is the 

Equipment Safety Law (GSG) to which 

ExVO is as a separate regulation 

(11. GSGV). 

In contrast, ATEX 137 (Directive - 

1999/92/EC) contains only "Minimum 

regulations for improving the health 

protection and safety of employees that 

could be endangered by potentially explosive 

atmospheres", so that each EC 

state can pass its own regulations beyond 

the minimum requirements. In the 

German Federal Republic, the contents 

of the directive have been implemented 

in factory safety legislation. In order to 

simplify the legislation, the contents of 

several earlier regulations have been simultaneously 

integrated into the factory 

safety legislation ('BetrSichVO'). From 

the area of explosion protection, these 

are: 

· The regulation concerning electrical 

installations in potentially explosive 

atmospheres (ElexV) 

· The acetylene regulation 

· The regulation concerning flammable 

liquids 

These regulations became defunct 

when the factory safety legislation 

came into force on 01.01.2003. 

Explosion protection guidelines 

(EX-RL) of the professional associations 

In the "Guidelines for the prevention of 

hazards from potentially explosive atmospheres 

with listed examples" of the 

German Chemicals Professional Association, 

specific information is given on 

the hazards of potentially explosive atmospheres, 

and measures for their prevention 

or limitation are listed. Of special 

use are the examples of individual 

potentially explosive process plants in 

the most diverse industrial sectors in 

which these measures are listed in detail. 

Valuable suggestions and risk evaluations 

are available for planners and 

operators of such plants or similar process 

plants. 

6 

While the EX Directives have no legal 

status, they are nevertheless to be regarded 

as important recommendations 

that can also be called upon for support 

in deciding legal questions in the event 

of damage. 

Standards 

There are a host of technical standards 

worldwide for the area of explosion protection. 

The standards environment is 

subject to constant modification. This is 

the result both of adaptation to technical 

progress and of increased safety demands 

in society. International efforts 

at standardization also contribute, with 

the aim of achieving the most uniform 

global standards possible and the resulting 

removal of barriers to trade. 

EC standards 

The standards for explosion protection 

valid in the European Community are 

created on the basis of the EC Directives 

under the leadership of CENELEC (European 

Committee for Electrotechnical 

Standardization). CENELEC comprises 

the national committees of the member 

states. Since, in the meantime, standardization 

at international level gained 

greatly in importance through the dynamism 

of the IEC, CENELEC has decided 

only to pass standards in parallel with 

the IEC. In practice, this means European 

standards in the area of electrical/ 

electronic systems will now be created 

or redefined almost exclusively on the 

basis of IEC standards as harmonized EN 

standards. For the area of explosion 

protection, this affects primarily the 

standards of the EN 60079 series. 

The numbers of harmonized European 

standards are structured according to 

the following scheme: 

e.g. EN 50014 : 1997 

IEC 

At the international level, the IEC (International 

Electrotechnical Commission) 

issues standards for explosion protection. 

The Technical Committee TC31 is 

responsible. Standards for explosion 

protection are found in the IEC 60079-x 

series (previously IEC 79-x). The x represents 

the numbers of the individual 

technical standards, e.g. IEC 60079-11 

for intrinsic safety. 

Year of publication 

Number of standard 

Harmonized European standard 

Modifications, released supplementary to the basic standard, are indicated 

by the letter "A" with consecutive number, e.g. A1.

Classification of explosion-protected equipment 

The equipment for explosion-protected 

areas are classified according to device 

groups/categories, zones, types of protection, 

explosion groups, and temperature 

classes. 

This information can be found in the 

identification code of the equipment 

(see Fig. 5). 

Device groups/categories 

Devices are classified into device 

groups: 

· Device group 1 

- in underground operations 

- in mines 

- as well as open-cast operations 

· Device group II 

- Devices for use in the other areas 

Each device group contains equipment 

that is in turn assigned to different categories 

(Directive 94/9/EC). The category 

specifies the zone in which the equipment 

may be used. 

Zones 

Areas subject to explosion hazard are divided 

into zones. Division into zones depends 

on the chronological and geographical 

probability of the presence of 

a hazardous, potentially explosive atmosphere. 

Information and specifications 

for zone subdivision can be found 

in EN/ IEC 60079-10. 

Equipment in areas where a constant 

explosion hazard exists (Zone 0) are 

subject to stricter requirements, and by 

contrast, equipment in less hazardous 

areas (Zone 1, Zone 2) is subject to less 

stringent requirements. 

In general, 95% of systems are installed 

in Zone 1 and only 5% of equipment is 

in Zone 0. 

Device group 1 (mining) 

Category M1 

Extremely high level of safety 

Sufficient safety Through 2 protective measures/in 

the event of 2 faults 

Device group II (other areas subject to explosion hazard) 

Sufficient 

safety 

Device group 

Categories 

Zone 

Fig. 5 Subdivision of explosion-protected equipment 

Category 1 

Extremely high level of 

safety 

Through 2 protective 

measures/in the event of 

2 faults 

Category 2 

High level of safety 

In the event of frequent 

device faults/in the 

event of one fault 

Category M2 

High level of safety 

Must be switched off in the 

presence of an Ex atmosphere. 

Category 3 

Normal level of safety 

In the case of fault-free 

operation 

Use Zone 0 Zone 20 Zone 1 Zone 21 Zone 2 Zone 22 

Atmosphere 

G (gas) D (dust) G D G D 

Comparison of device groups and categories 

Flammable gases, vapors, and mist Flammable dusts 

Zone 0 Hazardous, potentially 

explosive atmosphere 

present 

continuously and over 

extended periods. 

Zone 1 It is to be expected that 

a hazardous, potentially 

explosive atmosphere will 

only occur occasionally. 

Zone 2 It is to be expected that a 

hazardous, potentially 


occur only rarely and then 

only for a short period. 

Subdivision of combustible substances into different zones 

Type of protection 

Explosion group 

Temperature class 

Zone 20 Areas where a potentially 

explosive atmosphere comprising 

dust-air mixtures is 

present continuously, 

over extended periods, 

or frequently. 

Zone 21 Areas where it is expected 

that a hazardous, potentially 

explosive atmosphere comprising 

dust-air mixtures will 

occur occasionally and for 

short periods. 

Zone 22 Areas in which it is not to be 

expected that a potentially 


be caused by stirred-up 

dust. If this does occur, then 

in all probability only rarely 

and for a short period. 

7


Types of protection 

The protection types are design measures 

and electrical measures carried 

out on the equipment to achieve explosion 

protection in the areas subject to 

explosion hazard. 

Protection types are secondary explosion 

protection measures. The scope of 

the secondary explosion protection 

8 

Types of protection Examples Application 

in Zone 

Type of protection Schematic 

representation 

General 

requirements 

Basic principle Standard 0 1 2 

General requirements for the 

type and testing of electrical 

equipment intended for the Ex 

area 

Increased safety e Applies only to equipment, or its 

component parts, that normally 

does not create sparks or arcs, 

does not attain hazardous temperatures, 

and whose mains voltage 

does not exceed 1 kV 

Flameproof enclosure d If an explosion occurs inside the 

enclosure, the housing will withstand 

the pressure and the explosion 

will not be propagated 

outside the enclosure 

Pressurized enclosure p The ignition source is surrounded 

by a pressurized (minimum 

0.5 mbar) protective gas - 

the surrounding atmosphere cannot 

enter 

Intrinsic safety i By limiting the energy in the circuit, 

the formation of impermissibly 

high temperatures sparks, or 

arcs is prevented 

Oil immersion o Equipment or equipment parts 

are immersed in oil and thus 

separated from the Ex atmosphere 

Sand filling q Ignition source is buried in sand. 

The Ex atmosphere surrounding 

the housing cannot be ignited by 

an arc 

Molding m By embedding the ignition source 

in a molding, it cannot ignite the 

Ex atmosphere 

Protection types n Zone 2 

Several protection 

types are included 

under this type 

measures depends on the probability of 

the occurrence of a hazardous, potentially 


Electrical equipment for areas subject to 

explosion hazard must comply with the 

general requirements of EN 50014 and 

the specific requirements for the relevant 

type of protection in which the 

equipment is listed. 

Slightly simplified application of 

the other Zone-2 protection types 

- "n" stands for "non-igniting" 

EN 50014 

EN 50 019 

IEC 60 079-7 

FM 3600 

UL 2279 

EN 50 018 

IEC 60 079-1 

FM 3600 

UL 2279 

EN 50016 

IEC 60 079-2 

FM 3620 

NFPA 496 

EN 50 020 

IEC 60 079-11 

FM 3610 

UL 2279 

EN 50 015 

IEC 60 079-6 

FM 3600 

UL 2279 

EN 50 017 

IEC 60 079-5 

FM 3600 

UL 2279 

EN 50 028 

IEC 60 079-18 

FM 3600 

UL 2279 

The types of protection listed on the 

pages below are significant in accordance 

with EN 50014. All types of protection 

are based on different principles. 

Terminals, 

connection boxes 

Switchgear, 

Transformers 

Control cabinets 

switching cabinets 

Actuators, 

sensors, 

PROFIBUS DP 

RS 485-iS 

Transformers, 

switchgear 

Heater strips, 

capacitors 

Sensors, 

switchgear 

EN 50 021 

IEC 60 079-15 Programmable 

controllers 

X X 

X X 

X X 

X X X 

X X 

X X 

X X 

X X


Explosion groups 

In the explosion groups, a distinction is 

first made between equipment of 

Group 1 and of Group II: 

Electrical equipment of Group II is further 

subdivided into explosion groups. 

The subdivision depends on the spark 

ignition capability through a gap with a 

defined width and length (in accordance 

with EN 60079-14). 

Electrical equipment with approval for 

Explosion group IIC can also be used in 

explosion groups IIA and IIB. 

Determining the explosion group 

A gas is present both inside and outside 

a flame-proof enclosure. The gas inside 

the explosion chamber is ignited. 

Result: If an ignition inside the explosion 

chamber is not transferred through 

the gap of defined width to the outside, 

the explosion group has been determined 

(see Fig. 6). 

Explosion group Use 

Group 1 Electrical equipment for 

mines subject to fire-damp. 

==> fire-damp protection EEx...I 

Group II Electrical equipment for all other areas subject 

to explosion hazard 

==> explosion protection EEx...I 

Explosion group Maximum permitted 

gap on fireproof 

enclosures 1) 

IIA > 0.9 mm 

IIB 0.5 mm to 0.9 mm 

IIC < 0.5 mm 

Definition of the explosion groups 

Fig. 6 Explosion chamber 

Degree of hazard Equipment 

requirements 

1) The gap width is the width between two 25-mm long parallel flange surfaces of an explosion chamber 

Gap width 

Gap length 

Explosion chamber 

Potentially explosive atmosphere 

9


Temperature classes 

The ignition temperature of flammable 

gases or a flammable liquid is the lowest 

temperature of a heated surface at 

which the gas/air or vapor/air mixture 

ignites. 

Thus the highest surface temperature of 

any equipment must always be less 

than the ignition temperature of the 

surrounding atmosphere. 

Temperature classes T1 to T6 have been 

introduced for electrical equipment of 

Explosion Group II. Equipment is assigned 

to each temperature class according 

to its maximum surface temperature. 

Equipment that corresponds to a higher 

temperature class can also be used for 

applications with a lower temperature 

class. 

Flammable gases and vapors are assigned 

to the relevant temperature class 

according to ignition temperature. 

Explosion 

group 

10 

I Methane 


II A Acetone 

Ethane 

Ethylacetate 

Ammoniac 

Benzol (pure) 

Ethanoic acid 

Carbon oxide 

Methane 

Methanol 

Propane 

Toluol 

II B City gas 

Illuminating gas 

Temperature class Maximum upper 

surface temperature of 

the equipment 

T1 450 °C > 450 °C 

T2 300 °C > 300 °C 

T3 200 °C > 200 °C 

T4 135 °C > 135 °C 

T5 100 °C > 100 °C 

T6 85 °C > 85 °C 

T1 T2 T3 T4 T5 T6 

Ethylalcohol 

i-amylacetate 

n-butane 

n-butylalcohol 

Ethylene 

Definition of the temperature classes 

Petrol 

Diesel fuel 

Aircraft fuel 

Heating oils 

n-hexane 

Acetylaldehyde 

Ethylether 

Ignition temperatures 

of combustible 

substances 

II C Hydrogen Acetylene Carbon bisulphide 

Classification of gases and vapors into explosion groups and temperature classes

Intrinsic safety 

The intrinsic safety of a circuit is 

achieved by limiting current and voltage. 

This characteristic limits the type of 

protection "Intrinsic safety" to relatively 

low-power circuits. Applications for this 

are found in instrumentation and control, 

for example. 

The basis for the protection type "Intrinsic 

safety" is that a certain minimum ignition 

energy is required to ignite a potentially 

explosive atmosphere. In an intrinsically-safe 

circuit, no sparks or thermal 

effects occur in operation or in the 

event of a fault that ignite a potentially 


Categories of intrinsically-safe 

equipment 

Intrinsically-safe electrical equipment 

and intrinsically-safe parts of associated 

equipment are divided into categories 

(safety levels). The safety levels depend 

on safety requirements in designing the 

equipment. 

Isolating transformers 

Isolating transformers between the intrinsically-safe 

and the non-intrinsicallysafe 

circuits effect the necessary voltage 

and current limitation for the area 

subject to explosion hazard. 

The isolating transformers can be listed 

as separate equipment, or they can be 

integrated into the modules. 

The SIMATIC ® Ex modules and the 

ET 200iS distributed I/O station are 

equipped with integral isolating transformers. 

They have the advantage of reducing 

space requirements and wiring 

costs. 

Terms Definitions 

Intrinsicallysafe 

circuit 

Intrinsicallysafe 

electrical 

equipment 

Associated 

electrical 

equipment 

Minimum 

ignition 

energy 

An intrinsically-safe circuit is a circuit in which no spark and no thermal 

effect can cause the ignition of a potentially explosive atmosphere. 

All circuits in intrinsically-safe equipment are themselves intrinsically safe. 

Voltage and current in the intrinsically-safe circuit are low enough that a 

short-circuit, interruption or short-circuit to ground will not ignite the 

potentially explosive atmosphere. Intrinsically-safe electrical equipment is 

suitable for operation direct in the area subject to explosion hazard. 

Typical designation: 

EEx ib IIC 

In associated electrical equipment, at least one circuit is intrinsically safe. 

Actuators and sensors connected to this intrinsically-safe circuit can be 

located in the area subject to explosion hazard. However, the associated 

electrical equipment must not be located in the area subject to explosion 

hazard without further protection types. 

In the designation of associated electrical equipment, the type of protection 

is placed in brackets. 

Typical designation: 

[EEx ib] IIC 

The minimum ignition energy of a gas and a 

vapor/air mixture is the least possible electrical energy discharged by a 

capacitor that can ignite the most ignitable mixture of a gas or a vapor 

with air at atmospheric pressure and 20°C. 

Terms and definitions for intrinsic safety 

Safety level Description Installation of the 

equipment 

ia Intrinsically-safe electrical equipment must 

not cause any ignition 

· under normal operation 

· when a single fault occurs 

· when a combination of faults occurs 

ib Intrinsically-safe electrical equipment must 

not cause any ignition 

· under normal operation 

· when a single fault occurs 

Safety level of intrinsically-safe equipment 

Fig. 7 SIMATIC products with integral isolating transformers 

To Zone 0 

Zone 2, Zone 1 

11

Installing and operating electrical systems in 


Standards 

The installation and erection regulations 

specified in EN 60079-14 apply, as 

well as national regulations. 

Installation 

Three installation systems are used for 

electrical systems in areas subject to explosion 

hazard (see table on the right). 

Service and maintenance 

Regular servicing is required to maintain 

the safety of electrical systems in areas 


Some of the most important safety 

measures are: 

· Carrying out work on live electrical 

systems and equipment is prohibited 

in areas subject to explosion hazard. 

Work on intrinsically-safe circuits is a 

permissible exception. 

· In areas subject to explosion hazard, 

grounding or short-circuiting is only 

permissible if there is no danger of explosion. 

· In the case of all work carried out in 

areas subject to explosion hazard, 

there must be no possibility of ignitable 

sparks or excessively hot surfaces 

ocurring that cause an explosion in 

conjunction with a potentially explosive 

atmosphere. 

Operators must observe the following 

important principles in service and 

maintenance work: 

· Maintenance of the proper 

state of the system 

· Continuous monitoring of the electrical 

system 

· Undelayed execution of the 

necessary maintenance measures 

· Proper operation of the 

system 

· Cessation of operations in the case of 

unrectifiable faults that can constitute 

a hazard to personnel 

12 

Cable systems with 

indirect cable inlet 

The cables are inserted into 

the connection area of the 

protection type "Increased 

safety" via cable inlets and 

connected to the terminals. 

The terminals also have protection 

type "Increased safety". 

Manufacturer Installation engineer Operator 

Development of the electrical 

equipment intended for 

use in areas subject to explosion 

hazard. 

The manufacturer must observe 

general and specific 

building and design regulations, 

and the current stateof-the-art. 

If the standard requires a 

test to be carried out by an 

independent center, this 

must be organized. 

All approvals and manufacturer 

declarations must be 

made available to the user. 

The manufacturer is obliged 

to produce all electrical 

equipment in accordance 

with the test documentation 

and test patterns. 

Cable systems with 

direct cable inlet 

The connecting cables are 

run direct into the device installation 

ares. Only cable 

glands specially certified for 

this purpose can be used. 

Installation systems in areas subject to explosion hazard 

The installation engineer 

must observe the erection 

requirements and select and 

install the electrical equipment 

correctly in accordance 

with its use. 

If the installer is not also the 

operator, the installer is 

obliged to provide installation 

certification at the request 

of the operator. 

This certification confirms 

that the electrical systems 

correspond to requirements. 

If such certification is available, 

an additional test by 

the operator prior to startup 

is no longer necessary. 

Obligations of the manufacturer, installation engineer, and operator 

Piping systems 

The electrical cables are fed 

into the closed metal piping 

as single cores. The piping is 

connected to the housing 

using glands and provided 

with a seal at every inlet 

point. The entire piping system 

is flameproof in design. 

The piping system is also 

known as a conduit system. 

The operator is responsible 

for the safety of the system. 

The operator must undertake 

the subdivision into 

zones in accordance with 

the explosion hazards. 

Operators must ensure that 

the system has been properly 

installed: 

· before the initial startup 

· at specific intervals 

Operators are obliged to run 

the system properly. 

The operator must report to 

the competent authority every 

explosion that can be 

caused by operation of the 

system.

Ex protection in North America 


Introduction 

The basic principles of explosion protection 

are identical all over the world. 

However, techniques and systems have 

been developed in North America in the 

area of explosion protection that differ 

significantly from those of the IEC 

(International Electrotechnical Commission). 

The difference to IEC technology 

include subdivision of the areas subject 

to explosion hazard, the design of 

equipment, and the installation of electrical 

systems. 

Classification of areas subject to 

explosion hazard 

Areas subject to explosion hazard are 

termed "hazardous (classified) locations" 

in North America. In the US, they 

are defined in Sections 500 and 505 of 

the National Electrical Code (NEC), and 

in Canada they are defined in Section 18 

and Annex J of the Canadian Electrical 

Code (CEC). They encompass areas in 

which flammable gases, vapors, or mist 

(Class I), dusts (Class II) or fibers and 

threads (Class III) can be present in hazardous 

quantities. 

The areas subject to explosion hazard 

are traditionally subdivided into Division 

1 und Division 2 according to the 

frequency and duration of their occurrence. 

In 1996, the US introduced the IEC classification 

system additionally to the existing 

system for Class I. This change 

was made by Article 505 of the NEC, enabling 

users to select the optimal system 

from a technical and economic 

point of view. 

The IEC Zone concept was also introduced 

in Canada (CEC Edition 1988). 

Since then, all newly installed systems 

there must be classified according to 

this system. 

In the traditional North-American classification 

system, potentially explosive 

gases, vapors, and mist of Class I are arranged 

in Gas Groups A, B, C and D, and 

flammable dusts of Class II are arranged 

in Groups E, F and G. 

The letter A here indicates the most hazardous 

gas group, while according to 

IEC and the new classification in accordance 

with Article 505, Group C is the 

most hazardous gas group. 

In Canada, it is possible to use both gas 

group systems in zone classification. 

Determination of the maximum surface 

temperature in accordance with Article 

505 in the NEC takes place in agreement 

with IEC in six temperature classes 

T1 to T6, with an additional subdivision 

into temperature sub-classes in the division 

system. The existing system of 

temperature classes has not been 

changed following the CEC 1998. 

Degrees of protection provided by 

enclosures 

Just as the IP degrees of protection 

have been defined in accordance with 

IEC 60529, the US has Standard Publ. 

No. 250 of NEMA (National Electrical 

Manufacturing Association) that deals 

with the degree of protection of housings. 

These degrees of protection cannot 

be equated exactly with those of the 

IEC since NEMA takes account of additional 

environmental influences (e.g. 

coolants, cutting coolants, corrosion, icing, 

hail). The following table is therefore 

intended as a non-binding guideline. 

Degrees of protection acc. to NEMA Degrees of protection acc. to IEC 

1 IP 10 

2 IP 11 

3 IP 54 

3R IP 14 

3S IP 54 

4 and 4X IP 56 

5 IP 52 

6 and 6P IP 67 

12 and 12K IP 52 

13 IP 54 

Comparison of degrees of protection according to NEMA and IEC 

Note: 

Since the degree of protection requirements of NEMA correspond to, or are higher than, the 

IP degrees of protection of IEC, the table cannot be used to convert the IEC degrees of protection 

into corresponding NEMA degress of protection 

13



Gases, vapors, or mist 

Classification Class I 

NEC 500-5 

CEC J18-004 

Division 1 

Areas in which hazardous concentrations 

of flammable gases, 

vapors, or mist are present continuously 

or occasionally under 

normal operating conditions. 

Division 2 



vapors, or mist are not expected 

under normal operating conditions. 

14 

NEC 505-7 

CEC 18-006 

Zone 0 



vapors, or mist are present continuously 

or over long periods 


Zone 1 



vapors, or mist are present occasionally 

under normal operating 

conditions. 

Zone 2 



vapors, or mist are not expected 


Dusts 

Classification Class II 

NEC 500-6 

CEC 18-008 

Division 1 


of flammable dusts 

are present continuously or occasionally 

under normal operating 

conditions. 

Division 2 


of flammable dusts 

are not expected under normal 

operating conditions. 

Fibers and threads 

Classification Class III 

NEC 500-7 

CEC 18-010 

Class I Groups Class II Groups Class III 

NEC 500-3 

CEC J18-050 

Division 1 and 2 

A (acetylene) 

B (hydrogen) 

C (ethylene) 

D (propane) 

Class I Temperature classes 

NEC 505-7 

CEC J18-050 

Zone 0, 1 and 2 

IIC (acetylene + hydrogen) 

IIB (ethylene) 

IIA (propane) 

Division 1 and 2 Zone 0, 1 and 2 

NEC 500-3 

CEC J18-050 


E (metal) 

F (coal) 

G (grain) 

Class II 



T1 (≤450 °C) T1 (≤450 °C) T1 (≤450 °C) None 

T2 (≤300 °C) T2 (≤300 °C) T2 (≤300 °C) 

T2A, T2B, T2C, T2D 

(≤280 °C, ≤260 °C, ≤230 °C, 

≤215 °C) 

-- T2A, T2B, T2C, T2D 

T3 (≤200 °C) T3 (≤200 °C) T3 (≤200 °C) 

T3A, T3B, T3C, 

(≤180 °C, ≤165 °C, ≤160 °C) 

-- T3A, T3B, T3C 

T4 (≤135 °C) T4 (≤135 °C) T4 (≤135 °C) 

T4A (≤120 °C) -- T4A (≤120 °C) 

T5 (≤100 °C) T5 (≤100 °C) T5 (≤100 °C) 

T6 (≤85 °C) T6 (≤85 °C) T6 (≤85 °C) 

Classification of areas subject to explosion hazard 

Division 1 


of flammable fibers 

and threads are present continuously 

or occasionally under normal 

operating conditions. 

Division 2 


of flammable fibers 

and threads are not expected 



None 

Class III 


Division 1 and 2



Installation regulations 

Electrical equipment and systems for 

use in hazardous locations are covered 

by the National Electrical Code (NEC) in 

the US, and the Canadian Electrical 

Code (CEC) in Canada. 

These assume the character of installation 

regulations for electrical systems in 

all areas and they refer to a number of 

further standards from other institutions 

that contain regulations for the installation 

and construction of suitable 

equipment. 

The installation methods for the NEC's 

Zone concept largely correspond to 

those of the traditional Class/Division 

system. A new stipulation in the NEC 

1996, is the use of metal-clad (MC) cables, 

in addition to rigid conduits and 

mineral-insulated cables of Type MI in 

Class I, Division 1 or Zone 1. 

A significant advantage of the CEC is the 

increased potential for using cables. In 

contrast to the US, Canada has for some 

time now permitted the use of special 

cables similar to the steel-wire armored 

cables in the IEC area. 

Constructional requirements 

The regulations of the National Electrical 

Code and the Canadian Electrical 

Code specify which equipment or types 

of protection can be used in the individual 

areas subject to explosion hazard. 

In North America, different standards 

and regulations apply for the building 

and testing of explosion-protected electrical 

systems and equipment. In the 

US, these are primarily the standards of 

Underwriters Laboratories Inc. (UL), 

Factory Mutual Research Corporation 

(FM) and the International Society for 

Measurement and Control (ISA). In Canada, 

it is the Canadian Standards Association 

(CSA). 

Certification and designation 

In the US and Canada, electrical equipment 

and resources in workplaces subject 

to explosion hazard generally require 

approval. Electrical equipment 

that cannot ignite the potentially explosive 

atmosphere in which it is used by 

virtue of its design or special properties, 

is an exception to this rule. The competent 

authority decides if approval is required. 

Equipment that has been developed 

and manufactured for use in hazardous 

areas is tested and approved in the US 

and Canada by nationally recognized 

test centers. In the US, these include the 

test centers of the Underwriters Laboratories 

or Factory Mutual, and in Canada, 

the Canadian Standards Association. 

Any information relating to explosion 

protection must be shown on the marking 

of the equipment, along with information 

such as manufacturer, model, 

serial number, and electrical specifications. 

The requirements for this are 

specified in the NEC, the CECl, and in 

the relevant construction regulations of 

the test centers. 

Class I, II & III, Division 1 and 2 

Approved electrical equipment for Class 

I, Class II and Class III, Division 1 and 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 for T5 and T6) 

Examples: 

Class I Division 1 Groups C D T6 

Class I, Zone 0, 1 and 2 

In the case of equipment for use in 

Class I, Zone 0, Zone 1 or Zone 2, a 

distinction is made between "Division 

Equipment" and "Zone Equipment". 

Division Equipment: 

Equipment approved for Class I, 

Division 1 and/or 

Class I, Division 2, can be labelled 

with the following 

information: 

1. Class I, Zone 1 or Class I, Zone 2 

2. Gas group(s) IIA, IIB or IIC 

3. Temperature class 

Examples: 

Class I Zone 1 IIC T4 

Zone Equipment: 

Equipment that corresponds to one or 

more protection types in accordance 

with Article 505 of the NEC and Section 

18 of the CEC must be labelled as follows: 

1. Class (optional in Canada) 

2. Zone (optional in Canada) 

3. Symbol AEx (USA) or 

Ex or EEx (Canada) 

4. Protection type(s) 

used 

5. Electrical equipment 

Group II or 

gas group(s) IIA, IIB or IIC 

6. Temperature class 

Example: 

Class I Zone 0 AEx ia IIC T6 

15

Safety ratings 

Substance designation Ignition temperature °C Temperature class Explosion group 

1,2-dichloroethane 440 T2 II A 

Acetaldehyde 140 T4 II A 

Acetone 540 T1 II A 

Acetylene 305 T2 II C 3) 

Ammonium 630 T1 II A 

Gasoline 

Initial boiling point < 135°C 

220 to 300 T3 II A 

Benzol (pure) 555 T1 II A 

Cyclohexanone 430 T2 II A 

Diesel fuels (DIN 51601) 220 to 300 T3 II A 

Jet fuel 220 to 300 T3 II A 

Ethanoic acid 485 T1 II A 

Ethanoic acid anhydride 330 T2 II A 

Ethane 515 T1 II A 

Ethylacetate 460 T1 II A 

Ethyl alcohol 425 T2 II A / II B 

Ethyl chloride 510 T1 II A 

Ethylene 425 T2 II B 

Ethylen oxide 440 (self-decomposing) T2 II B 

Ethyl ether 170 T4 II B 

Ethylene glykol 235 T3 II B 

EL heating oil (DIN 51603) 220 to 300 T3 II A 

L heating oil (DIN 51603) 220 to 300 T3 II A 

M and S heating oils (DIN 51603) 220 to 300 T3 II A 

i-amyl acetate 380 T2 II A 

Carbon monoxide 605 T1 II A / II B 

Methane 595 (650) T1 II A 

Methanol 455 T1 II A 

Methyl chloride 625 T1 II A 

Naphthalene 540 T1 II A 

n-butane 365 T2 II A 

n-butyl alcohol 340 T2 II A 

n-hexane 240 T3 II A 

n-propyl alcohol 405 T2 - * ) 

Oleic acid 360 (self-decomposing) T2 - * ) 

Phenol 595 T1 II A 

Propane 470 T1 II A 

Carbon bisulphide 95 T6 II C 1) 

Hydrogen sulphide 270 T3 II B 

Special gasolines 

Initial boiling point < 135°C 

200 to 300 T3 II A 

City gas (Illuminating gas) 560 T1 II B 

Tetralin 

(tetrahydronaphtalene) 

425 T2 - * ) 

Toluol 535 T1 II A 

Hydrogen 560 T1 II C 2) 

Extract from the tables "Safety Ratings of Flammable Gases and Vapors" by K. Nabert and G. Schön - (Edition 6) 

* ) The explosion group for this material has not yet been determined. 

1) Also Explosion Group II B + CS2 

2) Also Explosion Group II B + H2 

3) Also Explosion Group II B + C2 H2 

16

Approval and testing centers 

Country Approval/testing center 

Australia International Testing and Certification Services (ITACS) 

4-6 Second Street, Bowden South Australia 5007 

Tel: +61-8-8346-8680, Fax: +61-8-8346-7072 

E-mail: alyssa.veale@itacslab.com 

Internet: www.itacslab.com 

TestSafe Australia 

919 Londonderry Road, Londonderry NSW 2753 

P.O.Box 592, Richmond NSW 2753 

Tel: +61-2-4724-4900, Fax: +61-2-4724-4999 

E-mail: testsafe@workcover.nsw.gov.au 

Internet: www.testsafe.com.au 

Simtars Head Office 

2 Smith Street Redbank, PO Box 467, Goodna 

Queensland 4300 Australia 

Tel: +61-7-3810-6333, Fax: +61-7-3810-6363 

Internet: www.simtars.com 

SAI Global Assurance Services 

286 Sussex Street, GPO Box 5420, Sydney NSW 2000 

Tel: +61-2-8206-6614, Fax: +61-2-8206-6032 

E-mail: assurance@sai-global.com 

Internet: www.sai-global.com 

Brazil CEPEL 

Caixa Postal 68.007, CEP: 21.944-970, Rio de Janeiro, Brazil 

Tel: +55-21-2598-6458, Fax: +55-21-2280-3687 

E-Mail: pilotto@cepel.br 

China NEPSI - National Center for Explosion Protection and Safety 

of Instrumentation 

103 Cao Bao Road, Shanghai 200233, China 

Tel: +86-21-64368180, Fax: +86-21-64844580 

E-mail: nepsi@online.sh.cn 

Internet: www.sipai.com 

Denmark UL Internationales Demko A/S 

Lyskaer 8, P.O.Box 514, DK-2730 Herlev 

Tel: +45-44-85-65-65, Fax: +45-44-85-65-00 

E-mail: info.dk@dk.ul.com 

Internet: europe.dynamicweb.dk 

Germany Physikalisch-Technische Bundesanstalt (PTB) 

Bundesallee 100, D-38116 Braunschweig 

Tel: +49-531-592-0, Fax: +49-531-592-9292 

Abbestraße 2-12, D-10587 Berlin 

Tel: +49-30-3481-1, Fax: +49-30-3481-490 

Internet: www.ptb.de 

DMT - Gas & Fire Division 

Am Technologiepark 1, D-45307 Essen 

Tel: +49-201-172-1734, Fax: +49-201-172-1735 

E-mail: gasandfire@dmt.de 

Internet: www.gasandfire.de 

IBExU Institut f. Sicherheitstechnik GmbH (Bergakademie 

Freiberg) 

Fuchsmühlenweg 7, D-09599 Freiberg 

Tel: +49-3731-3805-19, Fax: +49-3731-23650 

E-mail: post@ibexu.de 

Internet: www.ibexu.de 

TÜV Hannover/Sachsen-Anhalt e.V. 

Am Tüv 1, D-30519 Hannover 

Tel: +49-511-986-0, Fax: +49-511-986-1237 

E-mail: info@tuev-nord.de 

Internet: www.tuev-nord.de 

TÜV Nord e.V. 

Große Bahnstraße 31, D-22525 Hamburg 

Tel: +49-40-8557-0, Fax: +49-40-8557-2295 

E-mail: info@tuev-nord.de 

Internet: www.tuev-nord.de 

FSA - Forschungsgesellschaft f. angewandte Systemsicherheit 

u. Arbeitsmedizin mbH 

Dynamostraße 7-11, D-68165 Mannheim 

Tel: +49-621-4456-3606, Fax: +49-621-4456-3402 

Internet: www.fsa.de 


France LCIE - Laboratoire Central des Industries Électriques 

33 av du Général Leclerc, F-92260 Fontenay-aux-Roses 

Tel: +33-1-40 95 60 60, Fax: +33-1-40 95 86 56 

E-mail: contact@lcie.fr 

Internet: www.lcie.com 

INERIS Headquarter 

Parc Technologique ALATA BP 2, F-60550 Verneuil en Halette 

Tel: +33-3- 44 55 66 77, Fax: +33-3-44 55 66 99 

E-mail: ineris@ineris.fr 

Internet: www.ineris.fr 

Finland VTT Technical Research Centre of Finland 

P.O.Box 1000, FIN - 02044 VTT 

Tel: +358 9 4561, Fax: +358 9 456 7000 

E-mail: kirjaamo@vtt.fi 

Internet: www.vtt.fi 

GB Baseefa (2001) Ltd, Health and Safety Laboratory Site 

Harpur Hill, GB - Buxton Derbyshire SK17 9JN 

Tel: +44-1298-28255, Fax: +44-1298-28216 

E-mail: info@baseefa2001.biz 

Internet: www.baseefa2001.biz 

ERA Technology Ltd 

Cleeve Road, GB -Leatherhead Surrey KT22 7SA 

Tel: +44-1372-367-000, Fax: +44-1372-367-099 

E-mail: info@era.co.uk 

Internet: www.era.co.uk 

SIRA Test and Certification Ltd 

Rake Lane Eccleston, GB - Chester CH4 9JN 

Tel: +44-1244-670-900, Fax: +44-1244-681-330 

E-mail: exhazard@siratec.co.uk 

Internet: www.siraservices.com 

SIRA Head Office 

South Hill, GB - Chiselhurst Kent BR7 5EH 

Tel: +44-20-8468-1800, Fax: +44-20-8468-1807 

E-mail: sales@siratec.co.uk 


SIRA Certification Service (SCS) 

South Hill, GB - Chiselhurst Kent BR7 5EH0 

Tel: +44-20 8467 2636, Fax: +44-20 8295 1990 

E-mail: certification@siratec.co.uk 


Italy Centro Elettrotecnico Sperimentale Italiano (CESI) 

Via Rubattino 54, I-20134 Milano 

Tel: +39-2212-5372, Fax: +39-2212-5440 

Internet: www.cesi.it 

Japan The Technical Institution of Industrial Safety (TIIS) 

Kiyose Test House 

1-4-6 Umezono Kiyose, Tokyo 204-0024 Japan 

Tel: +81-424-91-4519, Fax: +81-424-91-4846 

Internet: www.ankyo.or.jp 

The Technical Institution of Industrial Safety (TIIS) 

Headquarter 

837-1 Higashi-Nakahara, Kamihirose Syama-shi, 

Saitama, 350-1321 Japan 

Tel: +81-42-955-9901, Fax: +81-42-955-9902 

Internet: www.ankyo.or.jp 

Yugoslavia Savezni zavod za standardizacijuYugoslavia SZS 

Kneza Milosa 20, Post fah 609, YU - 11000 Beograd 

Tel: +381-11-361-31-50, Fax: +381-11-361-73-41 

E-mail: jus@szs.sv.gov.yu 

17

Approval and testing centers 


Canada CSA International 

178 Rexdale Boulevard, Toronto, Ontario, 

CANADA, M9W 1R3 

Tel: +416-747-4000, Fax: +416-747-4149 

E-mail: certinfo@csa-international.org 

Internet: www.csa-international.org 

CANMET 

555 Booth , Ottawa, Ontario K1A 0G1 

Tel: +613-947-6580, Fax: +613-947-4198 

Korea 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 

Luxembourg Service de I'Energie de I'Etat Luxembourgeois 

B.P. 10, 34, avenue de la Porte Neuve, L-2010 Luxembourg 

Tel: +352-46-97-46-1, Fax: +352-22-25-24 

Internet: www.etat.lu 

Netherlands KEMA Headoffice 

P.O.Box 9035, NL-6800 ET Arnhem, 

Utrechtseweg 310, NL-6812 AR Arnhem 

Tel: +31-26 3 56 91 11, Fax: +31-26 3 51 56 06 

E-mail: information@kema.nl 

Internet: www.kema.nl 

Norway Nemko AS (Head Office) 

PO Box 73 Blindern, Gaustadalleen 30, N-0314 Oslo 

Tel: +47-22 96 03 30, Fax: +47-22 96 05 50 

Internet: www.nemko.de 

Austria TÜV Österreich 

Krugerstraße 16, A-1015 Wien 

Tel: +43-1-514-07-0, Fax: +43-1-514-07-240 

E-mail: office@tuev.or.at 

Internet: www2.tuev.at 

Poland Glowny Institut Gornictwa 

Kopalnia Doswiadczalna "BARBARA" 

ul. Podleska 72, skrytka pocztowa 72, PL 43-190 Mikolow 

Tel: +58-2028-0249, Fax: +58-2028-745 

Romania INSEMEX PETROSANI, Equipment Ex. Certification Service 

Str. Gen. Vasile Milea nr. 32-34, 

Cod 2675 Petrosani, Rumänien 

Tel: +4-054-541-621, Fax: +4-054-232-277 

Russia Test Center for Explosion-protected Electrical Equipment 

(VNIIEF), formerly Arzamas 16 

Prospect Mira, 37, 607190 Sarov, Russia 

Tel: +831-30-45669, Fax: +831-3045530 

Sweden 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 

Internet: www.sp.se/eng 

Switzerland Schweizerischer Elektrotechnischer Verein (SEV) 

Luppmenstraße 1, CH-8320 Fehraltorf 

Tel: +41-1-956-1111, Fax: +41-1-956-1112 

E-mail: sev@sev.ch 

Internet: www.sev.ch 

18 

Eidgenössisches Starkstrominspektorat (ESTI) 

Luppmenstraße 1, CH-8320 Fehraltorf 

Tel: +41-1-956-1212, Fax: +41-1-956-1222 

Internet: www.esti.ch 


Slovakia EVPU a.s., SKTC 101 

Trencianska 19, SK - 01851 Nova Dubnica (Slovakia) 

Tel: +421 42 44 03 500, Fax: +421 42 44 34 502 

E-mail: sktc101@evpu.sk 

Internet: www.evpu.sk 

Slovenia SIQ - Slovenian Institute of Quality and Metrology, Mr Igor 

Likar 

Trzaska cesta 2, SI - 1000 Ljubljana 

Tel: +386-1-4778-100, Fax: +386-1-4778-444 

E-mail: info@siq.si 

Internet: www.siq.si 

Spain 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 

South Africa South African Bureau for Standards (SABS) 

1 Dr. Lategan Road; Groenkloof, Private Bag X191, 

Pretoria 0001, South Africa 

Tel: +27-12-428-7911, Fax: +27-12-344-1568 

E-mail: info@sabs.co.za 

Internet: www.sabs.co.za 

Explosion Prevention Technology, Mr Roelof Viljoen 

Private Bag X 191, Pretoria, 0001; South Africa 

Tel: +27-12-428-6990, Fax: +27-12-428-6854 

TCS - Electrotech, Mr Gert Brink 

Private Bag X 191, Pretoria, 0001; South Africa 

Tel: +27-12-428-6325, Fax: +27-12-428-6327 

Czech Republic Physical - technical testing institute, Ostrava-Radvanice 

Pikartska 7, CZ - 71607 Ostrava-Radvanice 

Tel: 0420 595223111, Fax: 0420 596232672 

E-mail: ftzu@ftzu.cz 

Internet: www.ftzu.cz 

Ukraine Testing Certification Center of Explosion protected Electrical 

Epuipment 

50-ty Gvardeysky, divizii str., 17, Ukraine, 83052 Donetsk 

Tel: +38-(0622)-941243, Fax: +38-(0622)-941243 

E-mail: info@iscve.donetsk.ua 

Internet: www.tccexee.bizland.com 

Hungary Prüfstelle für Ex-geschützte Elektrische Betriebsmittel, BKI 

Mikoviny Sámuel u. 2-4, H - 1300 Budapest, Pf. 115 

Tel: (361) 368 9697, Fax: (361) 250 1720 

E-mail: bkiex@elender.hu 

Internet: www.bki.hu 

US Northbrook Division, Illinois, Corporate Headquarters 

333 Pfingsten Road, Northbrook, IL 60062-2096; USA 

Tel: +1-847-272-8800, Fax: +1-847-272-8129 

E-mail: northbrook@us.ul.com 

Internet: www.ul.com 

Bosten Operations, Northeast Field Engineering 

P.O.Box 9102, Norwood, MA 02062; United States 

Tel: 781-440-8000, Fax: 781-440-8718 

E-mail: information@fmglobal.com 

Internet: www.fmglobal.com

ET 200iS distributed I/O station 

Distributed systems are increasing in 

importance in process engineering too. 

When sensors and actuators have to be 

connected to a fieldbus, distributed I/O 

devices are the most cost-effective solution. 

The advantage of such solutions is that 

they dispense with the marshalling distributors, 

high cabling overhead, and 

necessary subdistributors and Ex isolation 

stages usual today. The result is 

huge cost savings in times of increasing 

cost pressure. 

The SIMATIC ET 200iS has been developed 

for areas subject to explosion hazard: 

iS stands for intrinsically safe. 

Overview of product features 

· Distributed I/O station in degree of 

protection IP30 

· Bit-modular and flexible design for 

precise adaptation to the 

automation task 

· Installation direct in Zone 1 

· Actuators and sensors can even be installed 

direct in Zone 0 

· Fixed wiring 

· Modules can be replaced without 

tools 

· Spring-loaded connections or screwtype 

connections available for the 

sensors 

· System-wide parameterization with 

STEP 7 

· Optimal integration of HART field devices 

(HART transparency) 

· Diverse diagnostics facilities 

· Reliable and rugged 

design 

· Non-volatile storage of 

manufacturer and user data 

on the electronics modules 

· Hot Swapping: replacement of 

electronics modules and the 

power supply and bus 

connection module under 

power during operation 

· Optimized for use with PCS 7 but still 

open for use with other process control 

systems 

Application areas 

The ET 200iS can be installed direct 

in Zone 1. It has certification in accordance 

with EU Directive 94/9/EC (ATEX 

100a) and so complies with the regulations 

required for equipment in areas 


It is used wherever explosion protection 

for gases is required in accordance with 

the following regulations: 

· CENELEC: EEx de ib [ia/ib] IIB/IIC T4 

· FM: Class I Div. 2 Group A-D T4 with 

actuators/sensors in Div. 1 

(available soon) 

· FM: Class I Zone 1 with actuators/sensors 

in Zone 0 (available soon) 

SIMATIC ET 200iS has been designed for 

use in a variety of sectors, such as: 

· Chemicals 

· Pharmaceuticals 

· Paint shops 

· Cement manufacture 

· Gas turbines 

· Drilling rigs 

Bit-modular and flexible design 

This selective design enables fast and 

optimal adaptation to plant-specific requirements 

for installation in areas subject 

to explosion hazard. 

The following benefits result: 

· Individualized configuration of the 

station 

· No superfluous channels 

· Easy to expand 

· Only a few channels fail in the event 

of a fault 

Terminal module 

for power supply 

24 V DC 

Screw-type 

terminals 

Equipotential 

grounding 

Extraction button 

Power supply, 

intrinsically safe, 

flameproof 

Terminal modules 

Fig. 8 The bit-modular and flexible design of the ET 200iS 

The ET 200iS system comprises terminal 

modules onto which are plugged the 

relevant functional units such as power 

supply, interface module, and electronics 

modules. 

The components in detail: 

· Flameproof power supply 

· IM 151-2 interface module for 

PROFIBUS DP 

· Up to 32 electronics modules in any 

combination for up to 64 analog signals 

or 128 digital signals 

· Bus terminator module 

A secure investment in the future 

with ET 200iS and PROFIBUS 

The SIMATIC ET 200iS handles communication 

between the field devices and 

the process control system/automation 

system over the Number 1 fieldbus – 

PROFIBUS. This open and system-wide 

communication keeps the solution flexible 

and also open to other manufacturers. 

Standardization of PROFIBUS in accordance 

with EN 50170 and IEC 61158 

also guarantees users security for their 

often large and long-term investments. 

The intrinsic safety of PROFIBUS is 

achieved by a fieldbus isolating transformer 

inserted before the area subject 

to explosion hazard. 

This limits the ignition energy to the 

permissible level and routes it to the 

hazardous area with intrinsic safety. 

Interface module 

EEx ib electronics modules 

Screw-type 

terminals 

EEx ia/ib connection terminals 

PROFIBUS DP RS 485-iS connection 

Bus terminator 

module 

19

ET 200M distributed I/O station 

Introduction 

The ET 200M distributed I/O station 

is a modular DP slave in degree of 

protection IP 20. Up to 8 signal and 

function modules and communications 

processors of the S7-300 ® can 

be used as I/O modules – the interface 

to the process. There are no slot 

rules. If active bus modules are 

used, modules can be replaced and 

expanded during operation. Connection 

to PROFIBUS DP is achieved 

using interface modules – optionally 

also using fiber optic cables. 

In addition to the standard modules, 

the versatile range also encompasses 

a whole series of other modules 

for solving special industrial applications. 

Siemens Aktiengesellschaft 

Automation and Drives 

Postfach 4848, D-90327 Nürnberg 

Federal Republic of Germany 

Areas subject to explosion 

hazard 

Different digital and analog modules 

exist as intrinsically-safe versions 

for the Ex area, for example, in 

chemicals, pharmaceuticals, or on 

drilling rigs. They enable isolated 

processing on a channel-by-channel 

basis of signals from Ex Zone 1. 

In addition, there are also HARTenabled 

analog modules. 

Simple installation 

The modules are hung on standard 

DIN rails and screwed into place. The 

backplane bus is self-generating, 

and the sensors/actuators are 

plugged in via the front connector. 

When a module is replaced, the connector 

is simply plugged into the 

new module of the same type. The 

wiring is retained. Coding on the 

front connector prevents mistakes. 

Standards and approvals 

UL UL 508 

CSA C22.2 No. 142 

cULus UL 1604 (Hazardous Locations) CSA-213 (Hazardous Locations) 

FM Class Number 3611, 3600, 3810 

Ex EN 50021 

IEC IEC 61131-2 

PROFIBUS IEC 61784-1:2002 Ed1 CP3/1 

Shipbuilding ABS, BV, DNV, GL, LRS, Class NK 

ET 200M standards and approvals 

Modules Function 

SM 321 Digital input module (4 x NAMUR) 

SM 322 Digital output module (4 x 15 or 24 V) 

SM 331 Analog input module (4 x 0...20 mA or 4...20 mA) 

SM 331 Analog input module (8 thermocouples or 

4 thermoresistors) 

SM 332 Analog output module 

(4 x 0...20 mA or 4...20 mA) 

SM 331 HART analog input module 

(2 x 0...20 mA or 4...20 mA) 

SM 332 HART analog output module 

(2 x 0...20 mA or 4...20 mA) 

S7-300 modules for areas subject to explosion hazard 

www.siemens.com/automation 

Order No.: 6ZB5310-0LE02-0BA0 

Printed in the Federal Republic of Germany 

26100/301475 SB 05032. 

High packing density 

The large number of channels on 

the modules explains the spacesaving 

properties of the ET 200M. 

Modules are available with 8 to 32 

channels (digital) or 2 to 8 channels 

(analog) each. 

Simple parameterization 

When used in the SIMATIC environment, 

STEP ® 7 is used for configuring 

and parameterizing the modules. 

Modules with diagnostics and 

interrupts 

Many modules additionally monitor 

signal acquisition (diagnostics) 

and the signals from the process 

(process interrupt) 

You can find more information on 

sensor technology on the Internet at: 

www.siemens.com/automation 

For a personal discussion, you can locate 

your nearest contact at: 

www.siemens.com/automation/ 

partner 

You can place a direct order 

electronically over the Internet at the 

A&D Mall: 

www.siemens.com/automation/ 

mall 

© Siemens AG 2003 

Subject to change without prior notice. 

All designations marked in this Product 

Brief with ® are registered trademarks 

of Siemens AG. 

products. An obligation to provide the 

respective characteristics shall only exist 

if expressly agreed in the terms of contract. 

Availability and technical specifications 

are subject to change without 

notice. 

The information provided in this brochure 

contains descriptions or characteristics 

of performance which in case of 

actual use do not always apply as 

described or which may change as a 

result of further development of the

Explosion protection - Fundamentals - Siemens

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