Union Instruments CWD2000 EX, Original Operating Instructions

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Safety devices
17
4 Safety devices
The calorimeter is a combination of an explosion proof box (analyzer) and
pressurized box with an air heater and PLC. The connection between the boxes is
the Instrument air tube. In the case of loosing the instrument air pressure a non-
return valve prevent a flow back to the heating system. In addition the total system
is powered down and solenoid valves are closed. The heating element is PTC
heating with a self-limitation function (between 200 and 300 °C).
4.1 Ex- enclosure
Inside of the housing components are installed, which could cause an ignition.
The design of the openings of the enclosure are designed for preventing a possible
ignition hazard to the outside.
4.2 Flame arrestor
Flame arresters preventing the dispersal of a possible ignition hazard to other
system components.
4.3 Purging system
The pressurized system ensures by continuous flushing with air, that no explosive
mixture inside of the overall system can occur.
Also ensures a permanent overpressure inside of the EX-p box, that no explosive
gas mixtures can penetrate.
The pre- purge time and the over- pressure is monitored all the time.
Further information:

enclosed documentation! - Manual Pressurized enclosure system -
4.4 Cable glands
Cables and wires which are connected to the housing must guarantee the sealing
and withstand a potential explosion pressure.
The selection of cables and the installation is done by operators.
Exchanging or adding of cable glands leads to the loss of the type approval.
Further information:

enclosed documentation! - Cert cable glands -
4.5 Thermal fuse
NOTE
The irreversible thermal fuse (melting fuse) triggers at 72 °C.
The self-resetting thermal fuse switches off the heater at 50 °C.