95-8533
3-43
18.2
Phosphate esters
C. Materials that remove the catalytic metals
from the active element of the sensor. Some
substances react with the catalytic metal
forming a volatile compound that can erode
the metal from the surface of the sensor’s
active element.
Halogens and compounds containing
halogen are materials of this nature and
others include:
Examples:
Chlorine
Bromine
Iodine
Hydrogen Chloride, Bromide or Iodide
Organic halides:
Trichloroethylene
Dichlorobenzene
Vinyl chloride
Freons
Halon 1301
(Bromotrifluoromethane).
NOTE
Brief exposure to these materials can
temporarily increase sensor sensitivity
due to the surface of the active element
being etched. Prolonged exposure
continues this process until the sensitivity
of the sensor is degraded, resulting in
shortened sensor life.
D. Exposure to high concentrations of
combustible gases for extended periods
of time can stress the sensing element and
seriously affect its performance.
The degree of damage to the sensor is
determined by a combination of contaminant
type, contaminant concentration in the
atmosphere, and the length of time the
sensor is exposed.
NOTE
If a sensor has been exposed to
a contaminant or a high level of
combustible gas, it should be calibrated
at the time of exposure. An additional
calibration a few days later should
be performed to determine whether
a significant shift in sensitivity has
occurred. If necessary, sensor should be
replaced.
NOTE
A combination of accessories such
as rain shields and dust covers is not
recommended and can result in slow
response to a gas leak.
EQ22XXDCU DIGITAL COMMUNICATION
UNIT USED WITH DET-TRONICS
H2S/O2 SENSORS OR OTHER
TWO-WIRE 4-20 MA DEVICES
Determine the best mounting locations for
the detectors. Whenever practical, detectors
should be placed where they are easily
accessible for calibration.
WARNING
Do not apply power to the system with
the cover removed unless the area has
been veried to be free of combustible
gases or vapors.
The DCU utilizes the following:
1. A terminal wiring board mounted at the
bottom of the junction box.
2. A communication module mounted above
the terminal wiring board using the standoffs
provided. See Figure 3-50.
Assembly and Wiring Procedure
Attach the sensor to the DCU enclosure. Do not
over-tighten. If a sensor separation kit is being
used, attach the sensor to the separation kit
junction box and wire the device as described
in the “Sensor Separation” section.
CAUTION
The sensor threads can be coated
with an appropriate grease to ease
installation. Also lubricate the cover
threads. (See “Ordering Information” for
part number of recommended lubricant.)
Connect the external wiring to the appropriate
terminals on the DCU terminal wiring board.
Refer to Figure 3-51 for terminal identification.
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