Emerson ROSEMOUNT OCX 8800 - Manual (Page 105)

Instruction Manual
IM-106-880, Rev 1.0
January 2007
7-7
OCX 8800
Figure 7-2. Oxygen and Cell
Output
Cal Warning (Calibration warning)
Cal Failed (Calibration failed)
Probable Cause Recommended Corrective Action
Calibration gas supply low or gas connection
leaking Check calibration gas supplies and connections. Adjust gas pressure and flow.
Replenish low calibration gas supplies and tighten or repair loose or leaking
connections. When calibration gas supplies are adequate, recalibrate.
O
2
cell degraded or failed Check O
2
cell impedance by reading the O2 Snsr R value via HART (see Figure 4-3,
sheet 2). If cell impedance is zero, replace O
2
cell. If cell impedance is less than 5000
ohms, check for cell housing ground fault. Repair ground fault. If cell impedance is
greater than 5000 ohms and no ground fault is indicated, replace O
2
cell.
Flow calibration gas to the O
2
cell. Read the cell millivolt output. Plot the cell millivolt
output and the calibration gas O
2
concentration on the chart shown in Figure 7-2. If the
plotted values do not fall on the slope line shown in Figure 7-2, replace the O
2
cell.
COe sensor degraded Replace COe sensor or increase warning level (SYSTEM, CALIB SETUP, COe Slope
Warn via HART.)
Low sample gas flow in sensor housing due to
flow path plugging Check the following portions of the flow path for plugging:
• blowback filter
• in-situ filter
• eductor outlet path
Table continued on next page
20
10
8
9
7
5
0.8
0.9
0.7
0.5
0.6
0.4
0.3
0.2
0.1
6
4
3
2
1
-20 0 20 40 60 80 100 120
ANALYZER OUTPUT (MILLIVOLT)
(23)
(73)
37390051
OXYGEN
CONCENTRA
TION
(%)