3�2�9 Mpd Flammable Sensor Operational Life; 3�2�10 Xnx Ec Sensor Operational Life - Honeywell XNX Technical Manual

XNX Universal Transmitter
Sensors should be calibrated at concentrations
representative of those to be measured� It is always
recommended that the sensor be calibrated with the target
gas it is to detect�
Caution: Responsibility for identifying and recording a sensor calibration
made with a different gas rests with the user. Refer to local regulations where
appropriate.
Ensure that the sensor and the vicinity around it is clear of
all traces of the calibration gas before continuing� This is to
avoid triggering spurious alarms�
If calibration fails at any point, discard the cartridge and
replace it with a new one (see Section 4�1) �
7� Remove the test equipment, refit the weatherproof cap to
the sensor (if previously removed for the test), and return
the system to normal operation�
3.2.9 MPD Flammable Sensor Operational Life
The pellistors used in flammable gas sensors can suffer
from a loss of sensitivity when in the presence of poisons or
inhibitors, e�g�, silicones, sulfides, chlorine, lead, or halogenated
hydrocarbons� The pellistors are poison resistant to maximize the
operational life of the flammable sensor� The typical operating life
of the pellistor sensor used in the MPD-CB1 is 60 months�
Section 3 - Calibration
3.2.10 XNX EC Sensor Operational Life
The typical life of a toxic gas sensor dependst on the application,
frequency, and amount of gas exposure� Under normal conditions
(3 month visual inspection and 6 month test/recalibration) the toxic
sensor has an expected life equal to or greater than these lifetimes:
• 12 months for ammonia, hydrogen chloride, and hydrogen
fluoride sensors (see further ammonia information below)�
• 24 months for chlorine dioxide, oxygen, and other toxic
sensors�
See Section 4 - Maintenance for sensor replacement procedures�
Caution: Oxygen deficient atmospheres (less than 6%V/V) may result in
inaccurate readings and performance.
Ammonia electrochemical cells are reliable and suitable for
applications where no background concentration of ammonia exists�
Under these conditions the cells are expected to operate for 12 to 24
months�
These ammonia cells are of the consumptive type� Their operating
life can be adversely affected by continuous or excessive exposure
to ammonia, or by prolonged exposure to high temperatures and
moisture�
To ensure continued detection availability, bump test the sensors
regularly and implement an appropriate cell replacement program�
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