Emerson Rosemount OCX 8800, Instruction Manual

Page: 122 / 306

Section 7: Foundation
Fieldbus
April 2017
Instruction Manual
IM-106-880C, OI
96
Mapping of
PWA
7.7.2 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 .
Table 7-3 Description of PlantWeb Alerts.
Sensor
Malfunction
Sensor
Degraded
Thermo-
couple
Malfunction
Transducer
Block:
1) O
2
Cell Open
2) Comb Cell
Error
Transducer
Block:
O
2
Cell
Impedance
High
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
Sensor
Alerts
Sensor
Alerts
T/C
Heater
Alerts
This alert is
active when
the sensor is
indicating a
very high or
unexpected
output.
This alert is
active when
the oxygen
sensor
impedance
indicates that
the cell is
beyond its
useful life.
This alert
indicates a
miswired or
faulty
thermocouple.
Check sensor
wires for loose or
broken
connection or
replace the cell.
Replace the
oxygen cell.
Check the
thermocouple
wires for loose or
broken
connections,
short circuit
condition, reverse
wire condition.
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, Overview page
165 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, Overview page 165
for details.
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, Overview page 165 for details.
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,
Overview page 165 for details.
What does
AMS the alert
Alerts Alarms Tab indicate?
Recommended
Action Description