YOKOGAWA EXAxt ZR22G, Руководство пользователя, Страница: 187 / 211

<12. Troubleshooting>
12-6
IM 11M12A01-02E 16th Edition : Mar. 19, 2020-00
<Locating cause of failure, and countermeasures>
(1) Check that the following have been set up correctly. If not, correct them. Then, recalibrate.
a. Check the preset zero gas concentration on the Calibration setup display. The displayed
concentration value has agreed with the concentration of the zero gas actually used.
b. 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.
a. From the Basic panel display, move to the Detailed-data display of the channel where the
alarm is being generated.
b. When the [▼] key is pressed once, the cell voltage should be indicated on the top line
(Figure 12.5).
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 theoretical cell
voltages. Although the tolerance to the theoretical value cannot be generally specified, a
reasonable one may be approximately ±10 mV.
Table 12.3 Oxygen Concentration and Cell Voltage
Oxygen concentration
(vol%O
2
)
Cell voltage
(mV)
1% 67.1
21% 0
(4) Check whether the deterioration of or damage to the sensor assembly that caused the
alarm has occurred suddenly during the current calibration in the following procedure:
a. Call up the Detailed-data Display.
b. Use the [Page Scroll] key to check Calibration Data (Figure 12.6). The span and zero
correction ratios of the last ten calibration can be checked here. By checking these data,
whether the sensor deterioration has occurred suddenly or gradually can be determined.
Cell voltage: 0 . 6 mV
Thermo voltage: 4 2 . 1 mV
C.J.resistance: 1 1 8 1 . 4 Ω
Cell resistance: - 4 Ω
Soft.rev.: 0 . 2 4
Tag:
F12.5E.ai
Hold
Calibration data:
1: 2 0 0 0 / 07 / 07 1 4 : 57
Span gas ratio: - 2 . 9 %
Zero gas ratio: 7 0 . 3 %
2: 2 0 0 0 / 07 / 07 1 4 : 5 4
Span gas ratio: - 2 . 9 %
Zero gas ratio: 8 9 . 7 %
Tag:
Hold
Figure 12.5 Detailed Data Display Figure 12.6 Calibration History
(5) If the sensor assembly has deteriorated suddenly, the check valve that prevents moisture in
the furnace from entering into the calibration pipes may have malfunctioned. If the furnace
gas flows into calibration lines, the gas is cooled and thus condensation develops and
accumulates in the pipe. During calibration the condensate is carried with the calibration gas
and blow onto the sensor assembly, whereby the cell is cooled quickly. This results in the
failed sensor assembly.