Brochure/Catalogue

EX basics
Safety in hazardous areas
Which explosion protection categories are most
commonly used?
• Pressure-resistant encapsulation (Ex d) in
compliance with EN60079-1:
Components that are capable of triggering an explosion
are enclosed in a housing that is capable of withstanding
the explosion. Openings in the housing are designed to
prevent the explosion from being transmitted externally.
• Increased safety (Ex e) in compliance with
EN60079-1:
This explosion protection category is normally applied to
transformers, motors, batteries, terminal blocks, electrical
lines and cables. It is not suitable for the protection of
electronic components and spark-generating components
(such as switches, relays or surge protection). Additional
measures and an increased safety level are implemented
in order to prevent any sparks, electrical arcing or
unallowable high temperatures which could trigger
ignitions. Increased safety is made possible by housing
that prevents dusts from penetrating within.
• Explosion protection methods (Ex n):
This explosion protection category may only be used in
the hazardous areas 2/22. Here there is no danger of an
explosion from the electrical equipment during normal
operations or during dened malfunctions. This includes
all electrical devices and components that have no spark-
forming contacts and that have a water-proof or dust-
proof housing. Larger creepage and clearance distances
are not required as long as the maximum rated voltage of
60 V AC / 70 V DC is maintained.
•
Intrinsic safety (Ex i) in compliance with EN60079-11:
Power supply to electrical equipment is carried out
through a safety barrier which functions to limit the
current and voltage so that the minimum power and
temperature levels for creating an explosive mixture
are not reached. Intrinsic safety for electrical and
electronic devices is specied so that their circulating
or stored power (even in event of malfunction) is never
strong enough to trigger an explosion in an explosive
atmosphere. You must also remember that not only
the electrical device but also all other components
connected to the circuit may be exposed to the explosive
atmosphere. All switching circuits in intrinsically
safe devices must be designed so that they are also
intrinsically safe.
These devices are divided into the category groups <ia> and
<ib> which differ in the number of occurring malfunctions.
Category <ia>
=> Switching circuits within category <ia> electrical
devices must not be able to cause a spark even if two
independent malfunctions take place.
Category <ib>
=> Switching circuits in electrical devices must not be able
to cause a spark when a malfunction.
Electrical devices for use in explosive gas, vapour and mist atmospheres –
in accordance with CENELEC
Explosion protection type Identication Protective design
Pressure-resistant
encapsulation
Ex d Encloses the explosion and prevents re
from spreading
Increased safety Ex e No spark formation or hot surfaces
Method of explosion protection Ex n No spark formation or hot surfaces
Intrinsic safety Ex i Limited energy for preventing spark formation or
overheated surface temperatures
CENELEC classification of gases, dusts and the maximum permitted
surface temperatures of devices and components
Gas
group
Temperature classes
T1 T2 T3 T4 T5 T6
I Methane – – – – –
IIA Ammonia
Methane
Ethane
Propane
Ethyl alcohol
Cyclohexane
n-Butane
n-Hexane
Benzene,
Kerosene
Acetaldehyde – –
IIB Lighting
gases,
Acrylonitrile
Ethylene,
Ethylene oxide
Ethylene
glycol,
Hydrogen
sulphide
Ethyl ether – –
IIC Hydrogen Ethine
(Acetylen)
– – – Hydrocarbons
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Technical appendix/Glossary
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