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Instruction Manual
IM-106-880C, OI
September 2009
7-7
Hazardous Area OCX 8800
Mapping of PWA Description of the PlantWeb Alerts that are supported by the Hazardous Area
OCX 8800 Fieldbus Output Board are listed in Table 7-3.
Figure 7-3. Description of PlantWeb Alerts
.
Alerts Alarms
AMS
Tab
What does the
alert indicate?
Recommended
Action
Description
Sensor
Malfunction
Transducer
Block:
1) O
2
Cell Open
2) Comb Cell
Error
Sensor
Alerts
This alert is
active when
the sensor is
indicating a
very high or
unexpected
output.
Check sensor wires
for loose or broken
connection or
replace the cell.
1) The oxygen cell interface is designed to
indicate a very high output if the cell becomes
disconnected from the electronics. It is
possible that a wire connection to the cell,
either in the probe tip or at the electronics, is
loose or broken. The cell may also be
damaged from mechanical stress. In extreme
cases, a very low oxygen concentration in the
process may cause this alarm. Diagnosis must
be done at the analyzer. Refer to Section 8:
Troubleshooting for details.
2) This problem could be caused by a mechanical
failure in the sensor housing or at the
electronics. An open circuit in the combustible
sensor could also cause this alarm. Refer to
Section 8: Troubleshooting for details.
Sensor Degraded Transducer
Block:
O
2
Cell
Impedance High
Sensor
Alerts
This alert is
active when the
oxygen sensor
impedance
indicates that the
cell is beyond its
useful life.
Replace the oxygen
cell.
Oxygen cells will degrade over time due to aging
and corrosion. An increasing cell resistance is a
good indicator of reduced cell performance. As
the cell impedance increases, the cell output falls
off and response time increases. Calibrating the
instrument will compensate for the increased cell
resistance up to several hundred ohms, beyond
which the cell is no longer functional. Diagnosis
must be done at the analyzer. Refer to Section 8:
Troubleshooting for details.
Thermo-
couple
Malfunction
Transducer
Block:
1) O
2
T/C Open
2) O
2
T/C
Shorted
3) O
2
T/C
Reversed
4) Comb T/C
Open
5) Comb T/C
Shorted
6) Comb T/C
Reversed
7) SB T/C Open
8) SB T/C
Shorted
9) SB T/C
Reversed
T/C Heater
Alerts
This alert
indicates a
miswired or faulty
thermocouple.
Check the
thermocouple wires
for loose or broken
connections, short
circuit condition,
reverse wire
condition.
When the heater thermocouple alarms are
initiated, they diagnose one of three states:
1) Open
2) Shorted
3) Reversed
The problem could be caused by a mechanical
failure in the probe tip or at the electronics. Power
to the device must be cycled to resume operation.
Diagnosis must be done at the analyzer. Refer to
Section 8: Troubleshooting for details.