SENSITRON
A Halma Company
MTEX4899
SMART S-MS MED
Manuale (IT)
P. 26/36
ceiling in order to maximise the effectiveness of the detection. All of
the gases heavier than air (LPG, Butane, Petrol Vapours) tend to spread
downwards; the detector should be placed at 30 cm from the floor.
-
Catalytic sensors (Pellistors) offer excellent output linearity up to
100% LFL and have an estimated lifetime of 4 years. Catalytic sensor
performance may be altered by the presence of some substances that,
when present in the atmosphere being analysed, can considerably
change the response of the sensor and even damage it irremediably.
The presence of inhibitors or poisons is the most common cause
of problems in the gas detection and, for this reason, it is necessary
to pay attention in order to avoid any contamination. Among the
most common poisons or inhibitors we can list silicones, tetraethyl
lead, sulphurous compounds (hydrogen sulphide), chlorinated
compounds (carbon tetrachloride), trichloroethylene and halogenated
hydrocarbons. These compounds do not affect the Infrared sensor,
which find a suitable application whenever a flammable gas is to
be detected in environments where Pellistor cannot work. This new
technology has undoubted advantages such as lower dependence
from environmental factors (temperature and humidity and the non
“poisoning”. Infrared sensors estimated lifetime is 4 years.
Warning
In case of varnished aluminium enclosures there’s the possibility of electric
charges accumulation. This accumulation could generate a flame under extreme
conditions. To avoid this risk, the user has to guarantee that the equipment won’t
be installed in places where extreme conditions could provoke an accumulation
of electrostatic charges. Moreover, the user has to clean the equipment with a
damp cloth.
Do not use gas detectors in atmospheres with a oxygen concentration greater
than 21%.
4. Special conditions
for safe use
-
The installation, use, maintenance and restoration must be done
following these Safety Instructions supplied by Sensitron.
-
The gas detector installation must guarantee the equipotential
connection of the enclosure.
-
Only the models equipped with dust filter can be installed in zone 21
and 22.
-
The dust filter has a membrane, this must not be damaged or removed.
Moreover, the membrane cannot be touched with bare hands to avoid
filter damage.
-
For models with varnished aluminium enclosures, there’s the risk of
electrostatic charges accumulation. The equipment must be cleaned
with a damp cloth or antistatic products.
-
The operating temperature conditions are described in the label, they
are compatible with sensing elements’ operating temperatures.