Safety instructions and general notes
2.3 Notes about usage
OP 73micro, TP 177micro (WinCC flexible)
Operating Instructions, 09/2007, 6AV6691-1DF01-0AB0
21
Potentially explosive atmosphere, Zone 2
Potentially explosive atmospheres are organized by zones. The zones are classified
according to the probability of the presence of an explosive atmosphere.
Zone Risk of explosion Example
2 Infrequent and brief development
of an explosive gas atmosphere
Areas around flanged pipe joints with flat
gaskets in closed rooms
Safe zone no
• Outside Zone 2
• Standard applications of distributed IO
WARNING
Observe the degree of protection
The HMI device must be installed in a metal enclosure or in a cabinet The minimum degree
of protection of these is IP54 (conforming to EN 60529). Make allowances for the ambient
conditions under which you install the HMI device. The enclosure must have a
manufacturer's declaration for Zone 2 (conforming to EN 50021).
Special conditions for operation in potentially explosive atmospheres of Zone 2
● In situations where the temperature on the cable or at the cable inlet of this enclosure
exceeds 70° C is or the temperature on the wire branching point exceeds 80° C under
operating conditions, the properties of the cables used must ensure that these can
withstand the actually measured temperatures.
● The cable inlets must be compliant with the required degree of protection (conforming
to 50021.)
● All peripheral devices connected to the HMI device must be certified conforming to
explosion protection types EEx nA or EEx nC.
● Measures must be taken to prevent transient voltages from causing the voltage to exceed
its nominal value by more than 40%.
● Ambient temperature range: 0° C ... 50° C vertical
● The temperature of the HMI device's cabinet surface should not exceed 60° C.
● The HMI device should be switched off immediately and replaced if damaged.
Such damage might be:
– Tears or detachment of individual membranes
– A tear in proximity to the viewing window
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