7. Test Basis and Safety Information for Intrinsically Safe Control Circuits (Ex-de and Ex-t)
MU2B-0375GE51 R0616C
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7. Test Basis and Safety
Information for Intrinsically
Safe Control Circuits (Ex-de
and Ex-t)
General EN60079-0
Ex-d Pressure-Proof Housing:
EN60079-1
Ex-e Increased Safety:
EN60079-7
Ex-t Protection by Enclosure:
EN60079-31
Ex-d Pressure-Proof Housing is based on
equipping the device with a microswitch
certified according to Ex-d. A spark which
might possible form when the micro-
switch’s contact is opened then has no
effect upon any flammable atmosphere
surrounding the switch. As a result of the
defined ignition gap and designed leak-
tightness, any spark-formation is
effectively suppressed in the microswitch,
so that a flammable atmosphere (the
frequency of which is defined in zones 1,
2, 21, and 22) surrounding the switching
device cannot be ignited. Furthermore,
the housing in the connection compart-
ment features Ex-e Increased Safety.
Through the use of a suitable earthing, a
certified power terminal, and a certified
cable gland, ignitions in the leak-tight
connection compartment are prevented.
Ex-t Protection by Enclosure is based
upon the housing’s IP65 rating, which
means that it is effectively protected
against the ingress of dust and water in
accordance with EN60529. Such devices
are thus suitable for use in dusty
explosive surroundings (the frequency of
which is defined in zones 1, 2, 21, and
22).
Generally speaking, pressure switches
featuring Ex-de and Ex-t are employed on
the switching device side, in zones 1 and
2 (gas) as well as 21 and 22 (dust). In the
case of protection in dusty explosive
surroundings, the sensors are certified for
use on the medium-side in zone 20.