Due to heightened safety requirements, regular function inspections and
calibration are imperative in areas subject to explosion hazards. Since this work can usually, however, only be carried out when the device is open, the plant may have to be shut down to create a safe atmosphere and to prevent ignition by potential sparks. Apart from the logistics problems this causes, there are also the additional costs involved in a loss of production.
For this application J. Dittrich Elektronic (Germany) manufactures the
explosion-proof gas measuring system MF420-Ex. Since the housing does
not need to be opened, it allows one-man calibration at the place of
installation in a potentially explosive atmosphere. Calibration takes place by means of two covered pushbuttons on the housing, synthetic air and test gas. A four-digit, alphanumeric display indicates the measured value as well as possible malfunctions of the sensor and electronics.
MF420-Ex is equipped either with a pellistor to detect explosive gases
and vapours or with a specific electrochemical sensor to detect toxic gases and vapours. The measuring system is easily wall mounted
by means of a separate mounting flange. Processing and output of the measurement signals (linear current output, 4-20 mA) are integrated. Power is supplied via 24 V direct current. The device is approved for use in areas subject to explosion hazards and has the EC Type Examination Certificate in accordance with Directive 94/9/EC (ATEX100a).
In Germany and Switzerland the MF420-Ex detects leakage points on gas pipes, petrol tanks and in paint storage warehouses.
On container ships transporting solvents, it detects any explosive vapours that might possibly escape from the containers. In China the
MF420-Ex promptly identifies any explosive gas-air mixtures that might occur in biogas plants.
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