4 Protective equipment
The CWD3000 EXP is supplied without a main switch, as the owner must provide
suitable equipment for separating the supply voltage as part of the voltage supply
equipment.
4.1 Pressurized enclosure ignition protection type
Pressurized enclosure ignition protection type “p” as per IEC EN 60079-2 enables
the operation of electrical devices in explosive atmospheres in which the creation
of a hazardous gas atmosphere in the device is prevented. This is achieved by
always maintaining overpressure with an ignition protection gas inside the device.
The housing may contain points of release. Before starting the device, the device
interior is flushed with ignition protection gas to thin any gas present and flush it
out of the housing.
The CWD3000 EXP is operated with compressed air as the ignition protection gas.
Before startup, the the housing is flushed out with compressed air equaling several
times its volume. Overpressure is then generated. These parameters are
controlled and monitored with control unit FS870 S located outside.
The CWD3000 EXP is divided into containment areas. In the inner containment
area, the combustible gas enters the combustion chamber for analysis. In the
surrounding containment areas, the pressure is higher, which prevents
uncombusted gas from being distributed further should a fault occur. The
difference in pressure is monitored by the pressure switch.
For analysis of the combustion gas, the gas flows into a combustion chamber and
is fully burned there through the corresponding air admixture. The combustion gas
pressure is reduced to 18 mbar inside the device, and the gas flows into the
combustion chamber at approx. 0.5 mbar. Thanks to the overpressure of 23 – 35
mbar in the surrounding housing, the gas cannot spread further in the device.
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