Каталог Weidmuller: Enclosures and Cable Glands

IECEx scheme
IECEx scheme
Technical appendix
The IECEx scheme is an international certification scheme for
products which meet the requirements of the international
standards, e.g. the technical committee TC31’s IEC standards.
The certificates awarded in this scheme are published on the
IECEx website (www.iecex.com) as an electronic certificate.
They can be viewed online and printed out.
A Certificate of Conformity (CoC) refers to a test report
(Ex Test Report ExTR) and on an assessment of the quality
assessment report from the manufacturer (QAR).
The standards used for the production of the test report
correspond almost entirely to the harmonised standards in
Europe. Recent EN standards were initially adopted as IEC
standards.
Protection concepts
The zoning described above provides the basis for the
selection of the type of ignition protection. So, as an example,
in the ATEX applicable areas, only ignition protection devices
meeting Ex ia for Zone 0 (highest probability of an explosive
atmosphere being present) are allowed.
Increased safety Ex e
No sparks and a surface temperature limited
to a safe level
Increased safety is for products where
there are no sparks produced during normal
operation or in case of a failure. The surface
temperature of the relevant parts is limited to
a value below the ignition temperature. Increased safety is
achieved by reducing the current load and raising the isolation
properties and by maintaining clearance and creepage distances
above the value in an industrial application. The highest voltage
permitted for this protection scheme is 11 kV (D.C. or A.C. rms).
This protection scheme is usually used for distribution cabinets.
Intrinsically safe Ex i
Limited to a safe level of ignition energy
Intrinsic safety is for products where electrical
energy which flows into the product, or is
stored in the product, is not sufficient to
ignite the surrounding explosive atmosphere.
This also applies in fault conditions. The methods that achieve
intrinsic safety mean that it is important that not only the devices
installed in direct contact with the explosive atmosphere are
constructed correctly, but also the electrical devices to which
they are connected.
Intrinsically safe equipment and intrinsically safe parts of
the associated equipment are divided into protection levels:
ia (for zones 0, 1, and 2), ib (for zones 1 and 2), and ic
(only for zone 2).
A typical application area are control and display circuits with
low voltage and current.
Pressure-resistant Ex d encapsulation
Limits the explosion to the inside of the enclosure
Pressure-resistant encapsulated enclosures are
designed for devices where sparks are
generated or which have hot surfaces which
are a source of ignition during normal
operation. Similarly, industrial components for use in potentially
explosive atmospheres are often made suitable by encapsulating
them in a pressure-resistant enclosure which otherwise could
not be used.
The surrounding possibly explosive atmosphere can enter the
enclosure and will produce an internal explosion during the
equipment’s lifespan.
The enclosure must therefore be stable enough to ensure
that it is not deformed or destroyed by the pressure created.
All connections of the enclosure are sized so that they
cannot transmit an explosion from inside to the surrounding
atmosphere. These connections are known as ignition gaps.
For this sort of ignition protection the explosion groups apply
(IIA, IIB, IIC). Devices using this protection principle may not be
installed in Zone 0.
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