Series 3793
TROVIS SAFE 3793 Electropneumatic Positioner
EXPERTplus valve diagnostics

Application
Positioner firmware to detect potential valve faults and to provide maintenance recommendations

For on/off valves in safety-instrumented systems

The EXPERTplus valve diagnostics for TROVIS SAFE positioners
can detect faults and provide predictive, status-oriented maintenance recommendations for valves with pneumatic actuators
in safety-instrumented systems. The full scope of diagnostic
functions is completely integrated into the positioner. The numerous diagnostic functions allow faults to be pinpointed in
on/off valves at an early stage.
The discrete analysis of the set point is performed in automaticmode. The positioner moves the valve to the operating point
or fail-safe position depending on the adjustable limits. An
automated partial stroke test is started when the set point is
between the predefined upper and lower test limits.
The TROVIS-VIEW software, which allows the user to access,read and edit the diagnosis, is easy to learn. The integration
options including eDD, eEDD, FDT/DTM allow the diagnostic
functions to be also used in other engineering tools. Classified
status messages and the condensed state conforming to theNAMUR Recommendation NE 107 can also be read on site at
the positioner display.
TROVIS-VIEW: User interface used to configure various
SAMSON devices
FDT: Field device tool for the manufacturer-independent integration of field devices
DTM: Device type manager to describe the device and communication properties
DD/eDD: Device description/enhanced device description
Special features•• Diagnostics for on/off valves•• Diagnosis data are constantly compiled, saved and analyzed in the positioner. Status messages are automaticallygenerated. Test data and their analysis are saved in thepositioner.
•• Cyclical polling of diagnosis data, multiplexer-capable•• Minimum and maximum temperature readings with analarm when the limits have been exceeded

Fig. 1: TROVIS SAFE 3793 Positioner with EXPERTplus
valve diagnostics•• Statistical information (in-service monitoring) and tests(out-of-service diagnostics) pinpoint critical states before
malfunctions can affect the process, allowing the user toplan predictive maintenance and service work on on/offvalves•• Display of classified status and error messages•• Status classification and condensed state based on
NAMUR Recommendation NE 107•• Status messages and condensed state can also be read off
at the positioner display•• Operating hours counter allows data and events to besorted by time•• Partial stroke test to assess the valve's ability to move•• Diagnosis data, test results and analysis saved in the positionerOptions•• Binary input, e.g. to start tests, monitor external solenoid
valve, etc.

Data Sheet for TROVIS-VIEW

T 6661

Data Sheet for TROVIS SAFE 3793 Positioner

T 8493SEdition January 2018

Data Sheet

T 8389-2S EN

Table 1: Overview of EXPERTplus functions
FunctionSee
sectionDescription

From user level

Start-up diagnostics

1.1

Positioner self-test, mechanical attachment, valve working range, initialization
time, opening and closing times

On-site: readCurrent process variables

1.2.1

Process variables: set point, valve position, set point deviation, operating hours
counter

On-site: read

Operating parameters

1.2.2

Number of zero calibrations and initializations, temperature, total valve travel,self-monitoring of positioner

On-site: read

Status messages/classification

1.2.3

Display and logging of classified status messages and condensed state

Diagnostics

3.1

Status classification change

Diagnostics

Statistical information

Data are compiled, saved and analyzed by the positioner while the process is running without disrupting the process. The data
are saved and analyzed in the positioner, i.e. the positioner follows the set point to position the valve. A classified status message
or error message is generated if the positioner detects an event.
On/off

2.1.1

Breakaway threshold, limit to detect open/closed position, time stamp, start value,dead time, transit time, end value of transit time measurement, reason formovement, status of last measurement

Diagnostics

Valve position histogram

2.1.2

Statistical distribution of the valve position

Diagnostics

Set point deviation
histogram

2.1.2

Statistical distribution of the set point deviation

Diagnostics

Load cycle histogram

2.1.2

Statistical distribution of the load cycle, dynamic stress factor acting on packing
and metal bellows

Diagnostics

Course of end position

2.1.3

Observing end position, detection of zero shift

Diagnostics

Tests

Similar to the statistical information, data are compiled, saved and analyzed by the positioner. However, in this case, the valve
position is not determined by the set point, but the active test. The tests can only be started when the conditions in the plant allow
it (e.g. plant shutdown or service work in the workshop).
Step response (PST)

2.2.1

Time stamp, dead time, T86, overshooting, pressure (only with pressure sensors
option), test status

On-site: write 2),
diagnostics

Step response (FST)

2.2.2Time stamp, dead time (rising/falling), T86 (rising/falling), T98 (rising/falling),
test status

On-site: write 2),
diagnostics

3

Collected data and analysis results can be displayed in graphs.

On-site: read4

Positioner with binary input option: logged actions of single functions and tests

Diagnostics

Status messages
Software for visualizationand parameterization
Options
Binary input1)

2)

The positioner has three user levels with various read and write access privileges:–– On-site: read · Parameters, which can be displayed at the positioner, can be read using the software–– On-site: write · Parameters, which can be displayed at the positioner, can be read and written using the software–– Diagnosis · Parameters, which can be displayed at the positioner as well as the diagnostic parameters, can be read and written using thesoftware
Restricted function (including test start and test stop)2		

T 8389-2S EN1

EXPERTplus valve diagnostics

1.1 Start-up diagnostics
EXPERTplus monitors the valve during automatic initialization
to ensure trouble-free start-up. At the same time, the supply
and venting times are determined.
The diagnosis also highlights any faults concerning attachment
and the valve working range as well as any hardware, data
memory and initialization time errors.

1.2 Process variables and operating parameters1.2.3 Pinpointing faults and their sources
The alarm and status messages generated by EXPERTplus allow faults to be pinpointed quickly. The last 400 generated
messages are saved in a FIFO memory with a time-stamp(logged by the operating hours counter).
The status messages are divided into the following categories:–– Start-up–– Configuration–– Process data–– Diagnostics–– AMR signal outside range

1.2.1 Current process variables–– Limit for total valve travel exceeded

EXPERTplus provides the key process variables collected by thepositioner (set point, controlled variable, set point deviationand temperature) and analyzes the diagnostic data.

–– Lower/upper end position shifted

1.2.2 Key operating parameters/status messages–– Brownout

To evaluate the current condition of the valve and schedulemaintenance routines, EXPERTplus provides the user with asummary on the device state. The status messages for the operating parameters listed below are time-stamped:•• Operating hours counter, distinction between positioner
switched on since last initialization, positioner in closedloop operation and positioner in closed-loop operation
since last initialization–– Dynamic stress factor exceeded–– Set point deviation–– Current too low/too high–– IP shutdown–– Temperature inside device below min. limit/above
max. limit–– Angle limitation•• Number of zero calibrations•• Number of initializations performed•• Setting a status message•• Resetting a status message•• Completion of a testFig. 2: Event logging

T 8389-2S EN		3

2Functions

2.1 Statistical information
By permanently recording raw diagnostic data in the positioner, the user can gather information about how the valve behaves under process conditions.
The continuous recording of signals enables an analysis of thecurrent measurement span as well as of the positioner’s entire
service life.
Recommendations for predictive maintenance can be given
based on the statistical information. In addition, immediatelyrequired action is reported.
2.1.1 On/off
The on/off diagnosis provides statements on the valve end position, i.e. the actual travel range and changes in transit timeand breakaway times.
The diagnosis runs for on/off valves in AUTO mode in thebackground. The function does not need to be activated.
While the plant is running, breakaway time (rising/falling),
transit time (rising/falling) and valve end position parameters
are recorded. The first values recorded are used as a reference for further tests.
If the analysis detects an error, the positioner generates a corresponding status message.
2.1.2 Histograms

Set point deviation
The set point deviation histogram contains a statistical analysisof any set point deviations recorded. This provides a summaryof how often and to which level a set point deviation has occurred during the valve service life and whether it shows a recent trend concerning the set point deviation. Ideally, the setpoint deviation should be as small as possible.
Load cycle
The cycle counter histogram provides a statistical analysis of
the cycles. As a result, the cycle counter also provides information on the dynamic stress of a bellows seal and/or packing. A valve cycle span starts at the point where the valve
stroke changes direction until the point where it changes direction again.
The positioner generates a corresponding message when thehistogram analysis indicates that the dynamic stress factor is
outside the permitted range.
2.1.3 Course of end position
The positioner monitors the lower and upper end positions todetect wear and dirt in the trim at an early stage. The valve
position is recorded when the lower end position is reached
and any changes logged with a time stamp. The first measured value is used as a reference.
Shifts in the end position are registered according to the assigned status classification.

Data are recorded in the background regardless of the operating mode selected. The data are plotted over the service life
or over a user-defined monitoring period in a histogram.
Valve position
The valve travel histogram is a statistical analysis of the plotted valve positions. It provides information about where thevalve mainly spends the majority of its time during its service
life and whether it shows a recent trend concerning changes
in its operating range.

Fig. 3: On/off4		

T 8389-2S ENFig. 4: Valve position histogram

Fig. 5: Set point deviation
histogram

Fig. 6: Load cycle histogram

Fig. 7: Course of lower end
position

T 8389-2S EN		5

2.2 Tests
Before performing the tests, it is important to make surewhether the conditions (in the plant or process) allow the valve
to be moved.

3.1 Classification and marking of status
messages
Based on NAMUR recommendation NE 107, the messages(events) generated by EXPERTplus are assigned a status (classified).

The tests provide a trend showing the current valve state, any
possible existing malfunctions and help to pinpoint faults andto schedule predictive maintenance work.

The status messages can be classified as required. The classified status messages (event) are summarized in a condensed
state:

2.2.1 Step response test (PST)

Condensed state

The step response test (PST) is particularly suitable for the status-oriented detection of malfunctions in pneumatic shut-off
valves. As a result, the probability of failure on demand (PFD)
can be reduced and it may be possible to extend maintenanceintervals. A shut-off valve normally in its end position can beprevented from seizing up or getting jammed. The initial
breakaway torque must first be overcome after the valve starts
to move from its end position. The initial breakaway torquedepends on the plug/seat seal, deposits on the plug, the process medium and friction at the valve trim. After the initial
breakaway torque has been overcome, it can be assumed thatthe valve is able to close completely. The recording of the test
results additionally allows an analysis of the dynamic control
response. During the test, the valve is moved through a user-defined working range.
A report and diagram show the test results. The positioner cansave a maximum of 52 reports and 7 diagrams.
2.2.2 Step response test (FST)

Status message

TROVIS-VIEW/
DTM

No message, OKgreen

Maintenance requiredblue

Out of specification

yellow

Function checkorangeFailurered

The condensed state is indicated on the positioner display andcan be read over the communication.

3.2 Graphs in TROVIS-VIEW, DTM, eDD(e.g. Siemens PDM)

The dynamic valve performance can be evaluated by performing the test. During the step response test (FST), the valve
moves through its entire working range, contrary to the step
response test (PST).

The trend-viewer function in TROVIS-VIEW allows the compiled raw data and test results as well as variables recordedin the positioner to be displayed in a graph.

A report and diagram show the test results. The positioner cansave a maximum of 7 reports and 7 diagrams.

–– Current process variables

3Visualization and parameterization of
the integrated EXPERTplus diagnostics

The TROVIS-VIEW software or the DTM tool generate graphsfrom the data, test results and status messages collected by thediagnostic firmware in the positioner.
In addition, the diagnostic data can also be made accessibleto other engineering tools using the DD (device description).
The eDD (enhanced device description) enables the data to be
displayed in a graph, e.g. using Siemens PDM, AMS. How
the data are displayed depends on the tool.

6		The raw data and test results include:–– Course of end position–– Step response (PST)The histograms described in section 2.1.2 are displayed as
bar graphs.
These graphs make any changes in positioning or control performance apparent to the user and support predictive maintenance.

4Binary input

The optional binary input allows various actions to be performed which also affect the diagnostic functions. The actions
are logged by the positioner.

T 8389-2S ENFig. 8: Step response test (PST)

Fig. 9: Step response test (FST)T 8389-2S EN		7

SAMSON AG · MESS- UND REGELTECHNIK
Weismüllerstraße 3 · 60314 Frankfurt am Main, Germany
Phone: +49 69 4009-0 · Fax: +49 69 4009-1507
samson@samson.de · www.samson.deT 8389-2S EN

2018-01-17 · English

Specifications subject to change without notice