Reference Manual
00809-0100-4021, Rev FB
August 2011
Rosemount 3144P
4-26
FOUNDATION Fieldbus
Statistical Process
Monitoring (SPM)
Statistical Process Monitoring algorithm provides basic information regarding
the behavior of process measurements such as PID control block and actual
valve position. The algorithm can monitor up to four user selected variables.
All variables must reside in a scheduled function block contained in the
device. This algorithm can perform higher levels of diagnostics by distribution
of computational power to field devices. The two statistical parameters
monitored by the Statistical Process Monitoring are mean and standard
deviation. By using the mean and standard deviation, the process or control
levels and dynamics can be monitored for change over time. The algorithm
also provides:
• Configurable limits/alarms for High variation, low dynamics, and mean
changes with respect to the learned levels
• Necessary statistical information for Regulatory Control Loop
Diagnostics, Root Cause Diagnostics, and Operations Diagnostics.
NOTE
Fieldbus devices offer a wealth of information to the user. Both process
measurement and control is feasible at the device level. The devices contain
both the process measurements and control signals that are necessary to not
only control the process, but to determine if the process and control is healthy.
By looking at the process measurement data and control output over time,
additional insight into the process can be gained. Under some load conditions
and process demands, changes could be interpreted as degradation of
instruments, valves, or major components such as pumps, compressors, heat
exchangers, etc. This degradation may indicate that the loop control scheme
should be re-tuned or re-evaluated. By learning a healthy process and
continually comparing current information to the known healthy information,
problems from degradation and eventual failure can be remedied ahead of
time. These diagnostics aid in the engineering and maintenance of the
devices. False alarms and missed detections may occur. If a reoccurring
problem in the process exists, contact Emerson Process Management for
assistance.
Configuration Phase
The configuration phase is an inactive state when the SPM algorithm can be
configured. In this phase, the block tags, block type, parameter, limits for high
variation, low dynamics, and mean change detection can be set by the user.
The “Statistical Process Monitoring Activation” parameter must be set to
“disabled” to configure any SPM parameter. SPM can monitor any linkable
input or output parameter of a scheduled function block that resides in the
device.
Learning Phase
In the learning phase of Statistical Process Monitoring, the algorithm
establishes a baseline of the mean and dynamics of a Statistical Process
Monitoring variable. The baseline data is compared to current data for
calculating any changes in mean or dynamics of the Statistical Process
Monitoring variables.
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