Positioner Series 3730 and Series 3731
EXPERT/EXPERT+ Valve Diagnostics

Application
Positioner firmware for early detection of control valve faults
giving maintenance recommendations

EXPERT and EXPERT+ are enhanced firmwares designed forpredictive, status-oriented maintenance on control valves withpneumatic actuators. All diagnostic functions are completely integrated into the positioner.
EXPERT and EXPERT+ enable operators to conveniently viewand edit data in the TROVIS-VIEW and FDT/DTM engineering
tools, which makes operation easy to learn. Integration intoother engineering tools is made possible by DD/eDD.
TROVIS-VIEW: graphical user interface for configuration andparameterization of various SAMSON devices
FDT: Field Device Tool; for manufacturer-independent integration of field devices
DTM: Device Type Manager; contains the device and communication properties
DD/eDD: Device Description/enhanced Device Description

Special features• Diagnostic tests performed on control valves without requiring additional sensors• Raw diagnostic data are permanently collected andanalyzed online in the positioner and status alarms are generated• Automatic plotting of reference graphs during initialization• Cyclical refresh of diagnostic data, multiplexing capability• Monitoring and test functions for predictive maintenance topinpoint critical conditions before faults occur• Display of the minimum and maximum temperatures with details on how long the limits have been exceeded• Automatic start of test functions• Display of service and maintenance recommendations• Display of classified status and fault alarms• Status classification and condensed state based on NAMUR
recommendation NE 107• Status alarms and condensed states also displayed on thepositioner’s LCD as well as issued to the fault alarm contact*• Plotting of y-x signature (drive signal) for fault detection• Test functions to determine friction changes• Operating hours counter allows data and test results to besorted by time
• Diagnostic data and test results saved and analyzed in thepositioner

TROVIS-VIEW Data SheetType 3730-x Positioner
Type 3731-x Positioner

T 6661 EN
T 8384-x EN
T 8387-x EN

Fig. 1 · Type 3241-1 Control Valve andType 3730-3 Positioner with HART® communication

Fig. 2 · Type 3731 Ex d Positioner

Edition February 2007

Data Sheet

T 8388 EN

Scope of functions
The diagnostic functions can be applied to any valve fitted witha pneumatic actuator.
Integrated into the positioner

Firmware version orhigher

Type 3730-2 and Type 373x-3

1.30Type 3730-4

K 1.0 / R 1.43

Type 373x-5

K 1.21/ R 1.41

Test function
Valve end
position trends

Seesection
2.1.2

Test function

Dynamic stress acting on
packing and metal bellows•

Histograms

2.1.4

Display of x, e and the cycle counter; overview ofworking range and control
response•

Information on spring force,
pneumatics, supply air,mechanical attachment••

Initialization
diagnostics

1.1

•

•

Operatingparameters,
current process
variables

1.2.1
1.2.2

Status alarms,
classification
Data logger

y-x signature
Description

Positioner self-test, mechanical attachment, valve travel
range, initialization timeOK?, opening and closing
times

2.2.1

On- Offline line•

Process variables w, x, e, y;operating hours counter,
number of zero calibrations
and initializations, temperature, total valve travel,self-monitoring of positioner

•

1.2.3
2.4
3.1

Display and logging ofclassified status alarms andcondensed states•2.1.1

Plotting and saving of process variables w, x, yand e with trigger function

••

2.1.3

EXPERT is available as an option.

See
sectionAutomatic closed position
logging, detection of end
position shift due to wear
and dirt on the seat andplug, alternation of closing
position

Cycle counter+

Table 1 · Available functions

On- Offline line

Description

Hysteresis test

2.2.2

Detection of friction changes

Staticcharacteristic

2.3.1

Analysis of the control loop,
e.g. dead band of control
valve

•

Step response

2.3.2

Analysis of the dynamic
control response (dead time,transit time, overshooting,rise time and settling time)•Display andparameterization
over software•3

Display of allcollected data and analysis
results using a suitable software tool,
simple parameterization••

Fig. 3 · TROVIS-VIEW, graphical user interface with Type 3730-3 Positioner

2T 8388 EN

1EXPERT

1.1
Initialization diagnostics
EXPERT monitors the control valve during automatic initialization to ensure trouble-free start-up. In addition, the opening andclosing times are determined.
The diagnostic function also indicates faults concerning attachment and the entire valve travel range as well as hardware anddata memory defects and the correct initialization time.

1.2

Online monitoring

1.2.1 Display of the current process variables
EXPERT provides the process variables collected by thepositioner (e.g. the reference variable w, controlled variable x,
error e and manipulated variable y) and analyzes the diagnostic data.

– Display of the current temperature as well as saving of themaximum and minimum temperatures, including alarm function when a limit is exceeded– Total valve travel, including customizable limit
1.2.3 Direct detection of fault sources
The alarms and status alarms generated by EXPERT enable
quick fault detection in case an error occurred. The last
30 alarms are logged in a FIFO (first in, first out) memory together with the operating hour they were generated in.
Possible fault categories are:Operating errors, e.g.:– Control loop error (excessive error, e.g. blocked actuator, insufficient supply pressure etc.)– Zero point shift
Hardware and data memory faults are also indicated.

1.2.2 Important operating parameters (Fig. 4)
EXPERT provides an overview of the valve status as well as thefollowing operating parameters, which enable the operator toanalyze the current valve condition and perform predictive
maintenance:– Operating hours counter, distinction between overall operating time and operating time in active control (since the firststart-up and the last initialization routine)– Number of zero calibrations performed– Number of initializations performed

Fig. 4 · TROVIS-VIEW with status for Type 3730-3 Positioner

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2EXPERT+

2.1
Process monitoring
By permanently recording raw diagnostic data (w, x, y and e) in
the positioner, the user can gather information about how thecontrol 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:– Valve position range OK– Valve mainly operates in the upper or the lower end position
As a result, recommendations for predictive maintenance canbe given. In addition, immediately required action is indicated.
2.1.1 Data logger
The variables reference variable w, valve position x, setpoint
deviation e, drive signal y and the operating hours counter arerecorded and saved in a FIFO memory. The interval between
the individual measuring points can be customized.
Apart from permanent sampling, the data can also be collected
online while the process is running, provided a certain trigger
condition is met.
The trigger condition can be defined by the user as certain
thresholds (valve travel (setpoint) or solenoid valve condition/forced venting).
Additionally, a pretrigger time is available which allows data to
be displayed also before the trigger conditions are met. The
memory size can be selected as required.

2.1.2 Valve end positions
This test serves to detect wear or dirt on the valve trim and is run
automatically while the process is running. The valve position isrecorded when the lower end position is reached and anychanges logged together with the drive signal y and a timestamp.
The first measured value is used as a reference.
Further measured values showing a greater deviation from thelast recorded value are logged.
2.1.3 Cycle counter
The dynamic stress that the valve packing and possibly a metal
bellows are exposed to can be analyzed by counting cycle frequency and assigning the travel performed in the cycle to a determined valve travel class. The results are displayed as along-term histogram and a short-term histogram. Based on the
diagnostic data, a dynamic stress factor [%] with an alarm limit
is generated.
2.1.4 Histograms (Fig. 5)
The variables valve position x and setpoint deviation e are sampled at determined intervals. They are classified and, similar tothe cycle counter, displayed as long-term and short-term histograms. The scan rate of the short-term histograms for x and e
can be adjusted. Additionally, the number of measurement values, the observation period, the average value as well as eminand emax are displayed.

Fig. 5 · Valve travel histogram

4

T 8388 EN

2.2
Internal drive signal y versus valve position x
2.2.1 y-x signature (Fig. 6)
While the process is running, the internal drive signal y is automatically recorded, averaged and assigned to a valve travel
class once the valve has reached a steady state.
The test function is also available in the manual mode. During
which, the valve is moved to certain predefined travel positions x over the travel range and the associated y signal is recorded when the valve reaches a steady state.
The reference graph required for this analysis is automaticallyplotted during initialization.
Statements can be made on the spring force, the pneumatic system, the air supply and the mechanical attachment. Corresponding alarms are generated.
2.2.2 Hysteresis test
This test serves to detect friction changes (hysteresis).
It is started automatically while the process is running as soon asa configurable time between tests has elapsed and the valve hasreached a steady state.
The results are saved, averaged and analyzed according tovalve position classes.
For this test, a minimal change of the valve opening over a certain period of time is preset with a determined tolerance band.
The test is automatically canceled when this tolerance is exceeded or the reference variable changes and the positioner returns to standard control operation. The analysis is based on
Δy.

The test can also be started in the manual mode. In this case, thetest is performed at certain valve travel positions x within thetravel range.
The reference graph required for this analysis is automaticallyplotted during initialization.
2.3
Tests for targeted early fault detection
2.3.1 Static characteristic(checking the static control response)
The static control response of the control valve is checked byvarying the reference variable in steps of, for example, 0.1 %.
The response of the controlled variable is recorded after a customized delay has elapsed (travel position when the valve hasreached a steady state).
The control loop is analyzed with the help of the minimum,
mean and maximum dead band of the control valve.
In manual mode, the entire valve travel range is recorded.
2.3.2 Step response(checking the dynamic control response, Fig. 7)
The dynamic control response of the control valve is checked bychanging the reference variable in steps of defined height inboth travel directions (step response).
The course of the controlled variable x, reference variable w,
drive signal y and setpoint deviation e is recorded at a determined scan rate until the valve has reached a steady stateagain. The dead time, T63, T98, overshooting as well as rise timeand settling time are indicated separately for increasing anddecreasing characteristic.
This test can be carried out in manual mode over the entire valve
travel range.

Fig. 6 · y-x signature (drive signal) as indicated in TROVIS-VIEW

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2.4
Plain text diagnostics (Fig. 8)
EXPERT+ automatically generates other additional status alarms
from the collected diagnostic data, e.g.:– Pneumatic leakage– Friction changed
As with EXPERT, the status alarms are logged with the operating
hour they were generated in.

3 Visualization and parameterization ofEXPERT and EXPERT+ diagnostics
The TROVIS-VIEW software or the DTM tool generate graphsfrom the data, test results and status alarms collected by the diagnostics firmware in the positioner.
In addition, the diagnostics data can also be made accessible toother engineering tools using the DD (Device Description) oreDD (enhanced DD), which enables the data to be displayed ingraph form, e.g. using Siemens PDM.
How the data are displayed depends on the applied tool.
3.1 Classification and marking of status alarms
Based on NAMUR recommendation NE 107, the alarms(events) generated by EXPERT and EXPERT+ are assigned a status (classified). The following states can be assigned to an alarm(event):
Status alarm (event)Engineering tool
TROVIS-VIEW/DTM

Inactive
Active · Classified as “No message”
Active · Classified as “Maintenancerequired”/”Maintenance demanded”
Active · Classified as “Function check”
Active · Classified as “Maintenance alarm”

Fig. 7 · Testing the dynamic control response, step response

6T 8388 EN

The classification can be assigned by the user. The classified
status alarms (events) are summarized in a condensed state.
Condensed status

Engineering tool
TROVIS-VIEW/DTM

Positioner
display

Maintenance alarm
Maintenance required
Maintenance demanded
Function check

Text

No message

The condensed status is indicated on the positioner display andcan be read using the communication features. In addition, thecondensed state can be issued to the optional fault alarm contact*.
Type 3730-4: The status classification is consistent with theProfibus Profile 3.01 with condensed status and diagnostic message extension. The process-related fault status is classified.
Type 373x-5: The condensed state is listed in the Resource
Block and can also be issued to the discrete output of either theFunction Block DI1 or DI2. In addition to the condensed state, ablock error for the Resource Block and AO Transducer Blockcan be formed from the classified alarms (events).
In this case, the following assigned states are possible:– No message– Maintenance soon
– Maintenance now*3.2

Diagrams in TROVIS-VIEW, DTM, eDD(e.g. Siemens PDM)
The software with trend viewing function allows the variables
recorded by the data logger (w, x, y, e) to be plotted versus thetime. Similarly, the raw data and data collected in the various
tests are plotted in graphs:– Current process variables– y-x signature– Hysteresis test
– Static characteristic– Step response– Valve end position trending
The long-term and short-term histograms described in section
2.1.4 are displayed as bar graphs.
A difference is made between long-term and short-term in they-x signature and the histograms.
The plotted graphs visualize changes in control behavior andsupport predictive maintenance.

Fault alarm contact in Types 3730-2 and 3730-3, optional inType 3731-3

Fig. 8 · Extended status alarms

7T 8388 EN

T 8388 EN

2007-02

SAMSON AG · MESS- UND REGELTECHNIK
Weismüllerstraße 3 · 60314 Frankfurt am Main · Germany
Phone: +49 69 4009-0 · Fax: +49 69 4009-1507
Internet: http://www.samson.de