Yokogawa Multi Channel Oxygen Analyzer System ZR22/AV550G - Manual (Page 219)

IM 11M12D01-01E 12-9
12. Troubleshooting
12.2.3 Remedies when Alarms are Generated
1) Alarm 1: Oxygen concentration alarm
See Subsection 8.2, "Setting Oxygen Concentration Alarms.".
2) Alarm 2: Zero-point calibration coefficient alarm
In automatic or semi-automatic calibration, Alarm 2 is generated when the zero correc-
tion factor is out of the range of 100
Ϯ30% (refer to Subsection 9.1.3, "Compensation").
The following are possible causes of this alarm.
1) The zero-gas oxygen concentration does not agree with the value of the zero-gas
concentration set in "Calibration Setup". Otherwise, the span gas is used as the zero
gas.
2) The flow rate of the zero gas is out of the specified range (600 ml/min
Ϯ60 ml/min).
3) The sensor assembly is damaged and so cell voltage is not normal.
<Locating cause of failure, and countermeasures>
1) Check that the following have been set up correctly. If not, correct them. Then,
recalibrate the channel.
* Check the preset zero gas concentration on the Calibration Setup display. The dis-
played concentration value has agreed with the concentration of the zero gas actually
used.
* The piping for calibration gases has been constructed so that the zero gas does not
leak.
2) If the alarm is not generated during the recalibration, improper calibration conditions
are considered as the cause of the alarm generated in the previous calibration. In this
case, no particular restoration is necessary.
3) If the alarm is generated again during the recalibration, deterioration of or damage to
the sensor assembly is considered as the cause of the alarm. It is necessary to replace
the cell with a new one. Before replacement, carry out the following.
Check the cell voltages when the zero gas and span gas are introduced.
When the system is configured for automatic calibration, let the calibration gas flow
from the Indication Check display and measure the voltage between terminals CELL+
and CELL- on the channel card using a tester or relevant equipment. The measured
voltage is the cell voltage. How to perform the indication check, refer to Section 10.4,
"Indication Check.".
When the valves for the calibration gas can be manually operated, the cell voltage can
be checked on the display of the averaging converter. The procedure is as follows.
a. From the basic panel display, move to the Detailed Data display of the channel where
the alarm is being generated.
b. The cell voltage should be indicated on the top line. (Figure 12.8)
c. Check whether or not the displayed cell voltage is very different from the theoretical
value at the oxygen concentration of the relevant gas. See Table 12.3 for the theoreti-
cal cell voltages. Although the tolerance to the theoretical value cannot be generally
specified, a reasonable one may be approximately
Ϯ10 mV.
Table 12.3 Oxygen Concentration and Cell Voltage
T12.3E.eps
Oxygen Conc. (%O 2 ) Cell Voltage (mV)
1% 67.1
21% 0