Dräger PEX 3000 Manual Del Usuario página 34

en |
Operation
The sensors used are based on measuring elements (pellistors), which are
poison-resistant (PR) and thus have a longer life span than conventional
sensors if catalyst poisons occur. However, there is still the rule to shorten the
test or calibration intervals if catalyst poisons are expected to occur in the
atmosphere to be monitored.
Pay attention to the ventilation conditions!
– Always arrange the sensing head and transmitter in the air flow between a
possible leak or collection point and possible source of ignition.
Note the density of the gas!
–
For gases with densities lower than that of air, such as hydrogen, methane
or ammonia, the transmitter must be located above a possible leak or at the
highest points where greater concentrations of gas may be found.
– For gases and vapours with densities greater than that of air, the transmitter
must be installed beneath a possible leak or at the lowest points where
these gases and vapours may be present.
5.1.2 Mounting the transmitter
– The transmitter is secured with screws (diameter: 4 mm) inserted through
the housing (see "Drilling templates", page 45).
5.2 Installing electrical connections
CAUTION
Electrical wiring is only to be laid and connected by an expert in compliance with
the pertinent regulations and laws concerning electrical equipment in potentially
explosive atmospheres as well as the approval conditions.
Connection between the transmitter and controller
– The maximum cable lengths for input resistances of 250 Ohms can be
found in the following table.
34
minimum sup-
2
0.5 mm
ply voltage at
(36 Ohm/km) (24 Ohm/km) (18 Ohm/km)
controller side
18 V 416 m
20 V 555 m
22 V 694 m
24 V 833 m
26 V 972 m
28 V 1110 m
– With a 3-core screened cable, shield braiding with cover ≥80%, outer
diameter min. 7 mm, max. 12 mm. Connect shielding to the earth clamp of
the controller, keeping this as short as possible.
– Place the cable shielding around the plastic cone as shown in the figure and
insert it into the metal cable gland. By tightening the cable gland,the
shielding is in electrical contact with the conductive inner lining of the
transmitter housing. This measure ensures the required RF-immunity
according to EN 50 270.
≈ 55 mm
WARNING
The cable gland is approved for fixed-location installation only. It is suitable for
line diameters of 7 to 12 mm.
– Remove the transmitter's housing lid
– Connection between the transmitter and controller as shown in the figure.
Core cross-section
2 2
0.75 mm 1.0 mm 1.5 mm
(12 Ohm/k
m)
625 m 833 m 1249 m
833 m 1110 m 1666 m
1041 m 1388 m 2082 m
1249 m 1666 m 2498 m
1457 m 1943 m 2915 m
1666 m 2221 m 3331 m
≈ 12 mm
2
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