Troubleshooting; Diagnosis Of Transmitter Health From Measurement Data; Table 12 Diagnosis Of Transmitter Health - Honeywell XYR 6000 User Manual

6. Troubleshooting

6.1. Diagnosis of Transmitter Health from Measurement Data

6.1 Diagnosis of Transmitter Health from Measurement Data
The output from the corrosion transmitter can provide insight into the health of the transmitter operation.
Table 12 shows the output expected for each variable when the transmitter is operating properly and the
table also shows an indication when a probe short condition exists and when no probe is connected.
Description
Corrosion rate
Pitting Factor
B value
Corrosion
Monitoring
Index
Note 1: Corrosion rate maximum will depend on the material constants and surface area entered. From a
measurement perspective, it relates to the absolute value of the polarization resistance of the working
electrode. If the polarization resistance is very low (<10 ohms), the instrument will be close to current
saturation. For optimal operation it is preferable to maintain the polarization resistance of the working
electrode at values of >100 ohms. This may be achieved to some extent by changes to the surface area
of the working electrode, thereby optimizing the span of the corrosion measurement.
Note 2: Items shown in brackets are general statements. No specific value can be provided.
Note 3: An exact zero value will not be achieved. It will be almost zero or very small, for example, 0.001
mpy.
Under conditions when general corrosion is prevalent on the material being monitored, the measured
corrosion rate observed as the primary variable (PV) may be expected to show evidence of being stationary
for a short term. In these cases the corrosion rate will tend to exhibit only slight variation in the short term,
perhaps over periods of hours or longer. Any slight process change, such as temperature variability is
often reflected in the corrosion rate behavior. Larger excursions in the corrosion rate may be experienced
if there are more pronounced changes to the environment, for example due to flow rates or changes in
composition.
The secondary variable, Pitting Factor, will typically exhibit a low value under these conditions (for
example, <0.01), although it may exhibit some short term response to abrupt changes in the environment,
for example sudden changes in temperature, flow rate or fluid composition.
The tertiary variable (the B value) will usually fall in a range of 0.010 to 0.030 volts, and will be stable.
The quaternary variable (Corrosion Mechanism Indicator) is largely dependant on the type of material
being studied, but generally, if active corrosion is being observed (>5mpy), it will tend to be significantly
larger than the case for very low corrosion rates.
34 OneWireless XYR 6000 SmartCET Corrosion Transmitter User's Manual
6. Troubleshooting

Table 12 Diagnosis of Transmitter Health

Transmitter General
output Corrosion
variable
PV Across range
SV <0.1
TV (Stable)
Note 2.
QV Across the
range
Pitting / Probe short
Localized
Corrosion
Across range Maximum
value
Note 1.
>0.1 <0.001
(Unstable) (Unstable)
Note 2. Note 2.
Across the (~ 0)
range
Note 2.
No probe
connected
~ 0
Note 3.
~ 1
(Unstable)
Note 2.
~ 0
Revision 3
6/24/08