Series 3730
EXPERTplus Valve Diagnostics for Type 3730-6 Positioner

Application
EXPERTplus records the valve condition while the process isrunning (in automatic mode) and generates messages on therequired maintenance work. In addition, numerous tests canbe performed in manual mode to pinpoint emerging faults.

EXPERTplus is a diagnostic firmware integrated into the positioner which allows the predictive, status-oriented maintenance of valves with pneumatic actuators.
The diagnostic functions of EXPERTplus are completely integrated into the Type 3730-6 Positioner. Diagnostic data arecompiled, saved and analyzed in the positioner itself. The
data are analyzed and classified status messages are generated about the condition of the valve based on the NAMUR
Recommendation NE 107 on the state of the valve.
Special features•• Diagnostic firmware for control valves•• Start-up monitoring•• Diagnostic functions performed without any additional
sensors (except for seat leakage detection using the optional leakage sensor)•• Cyclical polling of diagnosis data, multiplexer-capable•• Diagnostic data and test analysis saved in the positioner•• Logging with operating hours counter allows data andevents to be sorted by time•• Automatic generation of status messages•• Status classification and condensed state based on
NAMUR Recommendation NE 107•• Minimum and maximum temperature readings with details
on how long the limits have been exceeded•• Classified status messages and condensed state can beread in the operator software, at the positioner display or
issued at the fault alarm contact

Fig. 1: Control valve with Type 3730-6 Electropneumatic
Positioner with HART® communication and pressuresensors

Operator software
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.
•• TROVIS-VIEW · Operator 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 andcommunication properties•• DD/eDD · Device description/enhanced device description

Associated Information Sheet
Data Sheet for Type 3730-6 Positioner

T 6661 EN
T 8384-6 ENEdition February 2015

Data Sheet

T 8389-1 EN

Diagnostic functions
The diagnostic functions in EXPERTplus are divided into two categories: monitoring and dynamic tests.
•• Monitoring tests
Data are compiled, saved and analyzed by the positioner
while the process is running without disrupting it. The positioner follows the set point to position the valve. A classified
status alarm or fault alarm is generated if the positioner detects an event.
•• Dynamic tests
Similar to the monitoring tests, data are compiled, saved andanalyzed by the positioner. However, in this case, the valve
position is not determined by the set point, but by the activetest. The dynamic tests can only be started when the conditions in the plant allow it (e.g. plant shutdown or service workin the workshop).

1 Initialization results
EXPERTplus monitors the valve during automatic initialization toensure trouble-free start-up. For this purpose, the positioner determines the nominal range, opening and closing times of thevalve as well as the control parameters, such as proportionalaction coefficient (Kp level) and the derivative-action time (Tvlevel). Additionally, initialization errors including supply pressure status, attachment, initialization time exceeded or pin/switch position are reported.

Table 1 shows the diagnostic functions with their test analyses.

2 Diagnostics and measured process values
EXPERTplus shows the key process variables collected by thepositioner, such as set point w, valve position x, operatingstate, supply pressure ps and signal pressure pout. Leakage inthe pneumatic system is additionally shown for control valves.

2		T 8389-1 ENTable 1: Overview of EXPERTplus functions
FunctionAnalysis

Initialization result

Nominal range, min. transit times OPEN and CLOSED,
supply pressure during initialization,
proportional-action coefficient (Kp level),derivative-action time (Tv level),switch position ATO/ATC (closed position)

See section
1

Messages: Supply pressure status, x > range,
Δx < range, attachment, initialization time exceeded,
internal solenoid valve/forced venting/supply pressure, transit time reached, pin/switchposition,
no emergency mode, valve signature canceled
Measured process values

Condensed state, operating hours counter, set point w,
valve position x, set point deviation e, operating status, supply pressure, signal pressure,absolute total valve travel, inside temperature, dynamic load factor,
differential pressure, flow rate

2

Monitoring
Status messages
Condensed state

3.1
Display and logging of classified status messages and condensed state

Logging

3.2
3.3

Monitoring tests
Data logger

Depending on the trigger condition selected

4.1.1

Valve signature

Messages: Friction change, supply pressure,pneumatic leakage, actuator springs defect

4.1.2

Valve position histogram

Messages: Course of the manipulated variable range,
manipulated variable range

4.1.3

Set point deviation histogram

Average set point deviation

4.1.4

Messages: Manipulated variable range limitation,seat leakage, positioner-valve linkage
Cycle counter histogram

Dynamic stress factor

4.1.5

Message: Packing leakage
Leakage sensor

Message: Seat leakage

4.1.6

Course of end position

Zero shift

4.1.7

Message: Course of end position
Dynamic tests
Valve dead band
Binary input

Dead band–T 8389-1 EN		

4.2.1
53

3 Monitoring

3.3 Logging

3.1 Status messages
The valve diagnostics integrated into the positioner generates
classified status messages based on NAMUR recommendation
NE 107.
Messages generated from the analysis of the diagnosis can beclassified according to the possible causes.

The positioner saves the last 30 plain-text messages that havebeen generated including time stamp and details on how longthe message exists. The message logging generated by the diagnostics can be deactivated.

The following classifications are possible:•• No message
If an event is classified as “No message”, this event does nothave any affect on the condensed state.
•• Function check
Test or calibration procedures are performed in the positioner. The positioner is temporarily unable to perform its
control task as long as the procedure is taking place.
•• Maintenance required/maintenance demanded
The positioner still performs its control task (with restrictions). A maintenance demand or above average wear has
been determined. The wear tolerance will soon be exhausted or is reducing at a faster rate than expected. Maintenance is necessary in the medium term.
•• Out of specification
The positioner is running outside the specified operating
conditions.
•• Failure
The positioner cannot perform its control task due to a functional fault in the positioner itself or in one of its peripherals
or an initialization has not yet been successfully completed.

3.4 Dynamic HART® variables
The four dynamic HART® variables can be assigned to variables, such as set point, direction of action set point, set point
after transit time specification, valve position, set point deviation, absolute total valve travel, binary input status, internalsolenoid valve/forced venting status, condensed state, temperature, sound level (leakage sensor), ambient pressure, signalpressure, supply pressure, flow rate and differential pressure
as well as all active errors.

3.2 Condensed state based on NAMUR
Recommendation NE 107
To provide a better overview on the condition of the valve, allstatus messages are summarized in a condensed state which
is made up from a summary of all classified messages in thepositioner. The status message with the highest priority determines which condensed state is set.
The condensed state is also issued at the fault alarm output.
Status message

TROVIS-VIEW
or DTM

Positioner

FailureredFunction checkorangeTESTING, TUNEor TEST

Out of specification

yellow

blinking

Maintenancerequired/maintenancedemandedblue

No message, OKgreen

Priority

Text e.g.

4		

T 8389-1 EN4.1.4

Set point deviation histogram

4.1.5

Cycle counter histogram

As a result, recommendations for predictive maintenance canbe given. In addition, immediately required action is reported.

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.

4.1.1

Data logger

4.1.6

Leakage sensor

4.1.2

Valve signature

4.1.3

Valve position histogram

4 Diagnostic functions
The analysis of diagnostic functions highlights possible valve
malfunctions.

4.1 Monitoring tests
By permanently recording raw diagnostic data (w, x, pout ande) in the positioner, the user can gather information about
how the valve behaves under process conditions.
Signal logging enables an analysis of the current measuring
scope as well as of the positioner’s entire service life.
The following statements can be made, for example:–– Valve positioning range OK–– Valve mainly operates in the upper or the lower end position–– Dynamic stress factor

The data logger records the following variables: valve position
x, set point w, set point deviation e and signal pressure pout.
The recorded data are plotted against time in a graph. The
last 100 data points per variable are saved in a FIFO memoryin the positioner. The time between recording data points isuser-definable.
In addition to permanent logging, data logging can be started
automatically while the process is running, provided a defined
trigger condition is met.
The valve signature plots the signal pressure pout as a functionof valve position x, the course of supply pressure (supply pressure ps vs. the number of measurements) and friction (hysteresis vs. valve position x).
To perform the monitoring tests while the process is running,
the reference curve (signal pressure pout vs. valve position x)
must be recorded first.
The valve signature allows EXPERTplus to detect the following
malfunctions:–– Actuator spring compression reduced–– Zero error–– Supply pressures too high, fluctuates, too low, does not exist or the permissible limits exceeded–– Lower/higher friction change in entire range/in mid-position/near max. OPEN position/near CLOSED position

The set point deviation histogram contains a statistical analysisof any set point deviations recorded. It provides a summary of
how often and to which level a set point deviation has occurred during the valve service life and whether malfunctions
may arise. Ideally, the set point deviation should be as small
as possible.
A short-term histogram and a long-term histogram are plotted.
EXPERTplus generates a corresponding message when the histogram pinpoints to internal valve leakage or an limitation of
the upper or lower manipulated variable range.

By upgrading the positioner with a leakage sensor, it is possible to detect seat leakage when the valve is in the closed position. To achieve this, the leakage sensor measures the soundpressure level (dB) while the valve is tightly shut and compares
the current sound pressure level with predefined alarm limits.
To be able to use the full scope of functions, the response of
the leakage sensor to standardized conditions and to the prevailing process conditions must be measured. Furthermore, thelimit to activate the alarm must be entered.
The positioner generates a message if the current sound pressure level exceeds one of the limits to trigger an alarm.

Fig. 2: Type 3241-7 Control Valve with Type 3730-6 Positioner
and optional leakage sensor

The valve travel histogram is a statistical analysis of the plotted valve positions. It provides information about where thevalve mainly works during its service life and whether it showsa recent trend concerning changes in its operating range.
A short-term histogram and a long-term histogram are plotted.
EXPERTplus generates the corresponding message when thepositioner mainly works near or in the CLOSED/max. OPEN
position or an operating range shift is detected.

T 8389-1 EN		5

4.1.7

Course of end position

The course of end position is used to detect an alternating
zero point or a creeping zero point shift due to seat and plug
wear or dirt between the seat and plug.
The course of the end position records the valve position x andthe signal pressure pout together with the time stamp by theoperating hours counter when the valve moves to the lower
end position. The new recorded valve position is compared tothe last saved zero point.
A graph of the recorded valve positions at the lower end position is plotted over time.
EXPERTplus generates a corresponding message when the end
position shifts.

4.2 Dynamic tests
For reasons of safety, the dynamic tests can only be started
when the positioner is in the MAN operating mode. Therefore,
it is important to make sure before starting a test whether theconditions (in the plant or process) allow the valve to move.
The dynamic tests provide a trend showing the current valve
state, any possible existing malfunctions and help to pinpoint
faults and to schedule predictive maintenance work.

4.2.1

Valve dead band

The difference in set point w that causes a minimal change inthe valve position x is termed ‘dead band’.
The valve dead band is affected by the friction hysteresis andthe elastic processes in the valve stem packing.
The positioner specifies the set point w in a defined test range
in small steps and records the response of the valve position x.
The ascendent and descendent are plotted within the testrange. The response of the valve position x to the change inset point (∆w) is plotted in a graph.
The dead band is analyzed in the positioner when a stepheight is smaller than 0.2 %.

Visualization and parameterization
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 accessible
to other engineering tools using the DD (device description) or
EDD (enhanced device description), which enables the data tobe displayed in a graph, e.g. using Siemens PDM, AMS. How
the data are displayed depends on the tool.
Graphs in TROVIS-VIEW 4, DTM, EDD
The Trend Viewer function in TROVIS-VIEW allows the following compiled raw data and test results as well as variables (w,x, e, pout) recorded in the data logger to be displayed in agraph:–– Process variables–– Valve signature–– Course of end position–– Valve dead band
The long-term and short-term monitoring tests described insections 4.1.3 to 4.1.5 are displayed in bar graphs.
The valve signature and the histograms use long-term andshort-term monitoring tests.
These graphs make any changes in positioning or control performance apparent to the user and support predictive maintenance.

5 Binary input
The optional binary input allows various actions to be performed which also affect the diagnostic functions. If an action
is started over the binary input, this action is logged.

6		T 8389-1 EN

T 8389-1 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 8389-1 EN

2015-02-25 · English

Specifications subject to change without notice