Reference Manual
00809-0100-4801, Rev FA
October 2010
Rosemount 3051S Series
7-18
The LCD will also indicate the diagnostic condition. The “Time Since
Detection” clock in the Time Stamp box will start incrementing until the
statistical value is returned to normal. If the diagnostic alert is latched, the
“Time Since Detection” clock will continue to increment until the alert is reset
or SPM diagnostic is turned off.
Interpreting Results
The SPM diagnostic can be used to detect installation, process and
equipment changes, or problems. However, as the diagnostic is based on
detecting changes in process noise or variability, there are many possible
reasons or sources for the change in values and detection. Following are
some possible causes and solutions if a diagnostic event is detected:
Table 7-6. Possible causes of SPM diagnostic events
Detection Type LCD Display Potential Cause Corrective Action
High Variation
Detected / High
CV Detected
HIGH VARIA /
HIGH CV
Plugged impulse line (DP only). Follow facility procedure to check for and clear plugged
impulse lines. Both lines must be checked as the SPM
diagnostic cannot determine if the plug is on the high or low
side. Conditions that lead to plugging on one side may lead to
an eventual plug on the other side.
Aeration or aeration increase
(liquid flow).
a) If aeration is undesired, take necessary steps to eliminate
aeration.
b) If the measurement is DP flow and aeration is not desired,
move primary element to another location in the process piping
to ensure it remains full (no air) under all conditions.
Liquid present or amount of liquid
increased (gas or steam flow).
If liquid is undesired, take necessary steps to eliminate liquid in
gas or steam flow.
If some liquid is normal, and error correction in the gas flow
measurement is being done (such as an over-reading in wet
natural gas measurements), you may need to determine the
volume fraction of the liquid (e.g. using a test separator) and a
new error correction factor for the gas flow measurement.
Solids present or solids level
increased.
If solids are undesired, take necessary steps to eliminate.
Control loop problem
(valve stiction, controller issue,
etc.).
Review control valve or loop for control problems.
Process or equipment change or
problem has resulted in an
increase in the pressure noise
level.
Check process equipment.
High Variation
Detected
HIGH VARIA Rapid change of process variable
mean value.
Rapid changes in the process variable can result in indication
of high variation. If undesired, increase Alert Delay value
(default is 60 seconds). Increase the Learn/Monitor period
(default is 3 minutes).
(182 Seiten)
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