Commissioning The Sensing Head - Dräger Polytron SE Ex PR M1 DQ Notice D'utilisation

Installation & commissioning
– The line resistance per wire is not permitted to exceed 10 Ohms.
– For the wiring between the gas measurement transmitter and sensing head
(e.g. sensing head SE Ex ... DQ), only use wires with a cross-section of at
2
least 0.75 mm . Wires with a cross-section of 0.5 mm
with an insulated ferrule (Zoller+Fröhlich, type V3AE0005, V3AE0037 or
equivalent). This ensures that the protection rating of IP 30 is preserved if
the housing is opened for maintenance purposes.
This results in the following maximum distances for the different wire cross-
sections:
Wire cross-section
0.5 mm
Max. line length 50 m
1. Remove the transmitter housing cover.
2. Place the cable shielding around the plastic cone as shown in the figure and
insert into the metal cable gland. Tightening the cable gland means that 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.
A
≈ 55 mm
3. Connect terminals in accordance with figure A.
a. Connect "brown" terminal to terminal 1.
b. Connect "yellow" terminal to terminal 2.
c. Connect "black" terminal to terminal 3.
4. Close the housing cover and tighten with the screws (1.2 Nm).
Carefully connect all measuring line connections. Select the measuring lines
according to the installation instructions for each operating temperature range.
2
can be used if fitted
2 2 2
1.0 mm 1.5 mm
100 m 150 m
≈ 12 mm
4.3

Commissioning the sensing head

CAUTION
Delayed response time on the control unit.
When the sensing head is connected to the control unit, the overall response
time may be delayed. The entire measuring path must be taken into account
(e.g. latency of the control unit).
► Ensure that the required response time is maintained.
Observe the following instructions relating to the measuring function:
– Response to very high gas concentrations:
The measuring principle of heat of reaction, which is based on the catalytic
oxidation of a flammable gas, is essentially ambiguous because at high
measuring gas concentrations there is not enough oxygen in the sensor for
oxidation of the flammable gas. As a result, the measuring signal decreases
at high gas concentrations and can lead to values within the measuring
range. The downstream controller must be operated with alarm devices and
measured value outputs (if present), as well as alarm outputs operating as
latched if the measuring range is exceeded. These types of latching alarms
are only permitted to be reset when it has been demonstrated via a
measurement taken outside the gas detection system that the concentration
of flammable gases or vapours is below the full scale value.
– Minimum oxygen concentration:
The catalytic measuring principle requires a minimum oxygen concentration
of 12 Vol%, otherwise the measured values displayed will be too low due to
oxygen deficiency.
– Ensure adequate ventilation! Always position the sensing head and sensor
in the air flow between possible leak or collection points and the potential
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 sensing head 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 sensing head must be installed beneath a possible leak or at the
lowest points where these gases and vapours may be present.