Dräger SE Ex HT M, Инструкция по эксплуатации, Страница: 33 / 60

33
Intended Use
Sensing Head SE Ex LC M for a measuring range of 0 to 10 %LEL
The sensing head Polytron SE Ex LC M comprises a gas sensor type Ex-sensor
LC M (protection type flameproof enclosure and increased safety, "de" resp.
enclosure protection IP 6x, DMT 97 ATEX E 188 X). It must not be operated at
ambient temperatures lower than –40
o
C. The maximum ambient temperature is
40
o
C for temperature class T6, 50
o
C for temperature class T5, and 85
o
C for
temperature class T4.
Dust explosion protection: At the maximum ambient temperatures of 40
o
C or 50
o
C
or 85
o
C the maximum surface temperature is 85
o
C or 100
o
C or 135
o
C respec-
tively.
Not to be used in oxygen enriched atmospheres.
In conjunction with the central controllers Polytron SE Ex or REGARD Ex with pre-
adjusted alarm thresholds audible and visible alarm devices or automatic counter-
measures can be activated before the detected gases or vapours can form danger-
ous flammable mixtures with air.
The following hints in respect to the measuring function have to be observed:
1. Behaviour at very high gas concentrations
Basically, the measuring principle of heat of reaction which is based on the cata-
lytic oxidation of a flammable gas, is ambiguous because at high gas concentra-
tions there is not enough oxygen in the sensor necessary for the oxidation
process. So the measuring signal decreases at high gas concentrations and even
can lead to measuring signal within the measuring range again. A connected
controller must be operated with alarm devices, outputs, and alarm thresholds
operating as latched if the measuring range is exceeded.
In this case do not reset latching alarms without having ensured a safe condition
by means of an independent gas concentrations measurement.
2. Minimum oxygen concentration
The measuring principle of heat of reaction needs a minimum oxygen concentra-
tion of 12 % by vol., otherwise the measuring values will be too low because of oxy-
gen deficiency.