Dräger SE Ex HT M, Инструкция по эксплуатации, Страница: 36 / 60

Installing Equipment
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— Consider the complete scope of environmental conditions influencing the
sensing head. Avoid external influences such as splashing water, oil, corrosive ae-
rosols (salty sprays) etc. and the possibility of mechanical damage.
— Leave at least 30 cm free space beneath the sensing head to provide accessibility
for calibration work.
Mounting of the sensing heads Polytron SE Ex PR M and SE Ex LC M by means of
four screws (diameter 4 mm) through the holes of the housing, for sensing head
Polytron SE Ex HT M screws with diameter of 6 mm are necessary (see dimension/
dimensional drawing see page 59).
Remark
Certain substances in the atmosphere to be monitored may impair the sensitivity of
the sensors (Ex-Sensor PR M, Ex-Sensor HT M or Ex-Sensor LC M) installed in the
sensing head. The following substances are known at present:
a) polymerizing substances such as Acrylo nitrile, Butadiene and Styrene,
b) corrosive compounds such as ammonia and halogenated hydrocarbons (releas-
ing halogenes such as bromine, chlorine or fluorine when being oxidized),
c) catalyst poisons such as sulphurous and phosphorous compounds, silicon com-
pounds (especially silicones), and metal-organic vapours.
The sensors used are based on measuring elements (pellistors) which are poison-
resistant and so have a longer lifetime than conventional sensors if catalyst poisons
occur. However there is still the rule to decrease the test or calibration intervals if
catalyst poisons are expected to occur in the atmosphere to be monitored.
Pay attention to ventilation!
— Always arrange sensing head in air flow between possible leak or collection point
and possible source of ignition.
Pay attention to the density of gas!
— In case of gases, the density of which is 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 at which major concentrations of gas may be found.
— In case of gases and vapours with a density greater than that of air, the sensing
head must be installed beneath a possible leak or at the lowest points at which
such gases and vapours may be present.