CONTROL VALVE ADVANCED DIAGNOSTICS WITH

FOUNDATION FIELD BUS POSITIONER

K.N.Narayanan

P.Ramakrishnan

Sr.Manager

SAMSON CONTROLS PVT.LTD.

Positioner type 3730-5

Product management

Jens Bargon / V42

Smart Valve Positioner with

diagnostic functions

Communication of Foundation Field bus

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Control Valves

Product overview Process Valves

Positioner and Accessories

Control Valves are the “Final Control

element”

in every process plant

They are subject to wear and tear

and therefore an important target

for asset management and predictive

maintenance procedures

Control Valves & FF Smart Positioners

Smart positioners with integrated diagnostic

functions and FOUNDATIONTM Fieldbus technology

deliver optimal solution

· 6

Life Cycle Costs (Total Cost of Ownership)

Calculated with SAMSON Programme

Standard control valve for PN (Class 300) cast steel 1.0619/A216 WCC, equipped

with pneumatic actuator and FF smart positioner

15 years of useful lifetime

1 manly hour repair time

Repair on site

Smart diagnosis for predictive / proactive

maintenance

Smart Positioners with advanced diagnostic features offer us information , enabling

fault detection and analysis on line.

This acts as a powerful tool for predictive maintenance.

Integrated statistics analyses & provide remedies for the fault.

Problems like , air leakage, actuator leakage , packing friction change,

Diaphragm failure, process deviation etc . Can be addressed by the Positioner.

Information available can be utilised for preventive ,predictive or proactive maintenance.

Usually the term „diagnostic“ is used in the medicine and means

interpretation of symptoms with the target to get information about the

actual status or reasons of a malfunction.

1 step: condition monitoring → measuring different process parameters

Deliver symptoms of expected or existing malfunctions

2 step: diagnosis → interpretation of the process parameters

By experienced service personal

Better: via software, based on experienced algorithms

3 step: maintenance requirements / measures → constructive steps

Service-> Keep the working condition

Recondition-> Restore the working condition

What is diagnosis?

Samson/KNN/ 13th July 2012

Example of Diagnostic Functions

Travel histogram

(The histrogram provides information about where the valve mainly works during its

service life and if it shows a recent trend towards changes in its working range.)

Hysteresis test

(It displays changes in friction. The positioner generates a message when the

results of the hysteresis test pinpoint to „Friction“ or „External leakage“.

Trend of travel end position

(This feature detects fluctuating zero points or creeping zero point shifts due to

seat and plug wear or dirt between seat and plug.

Steady-state Drive Signal Diagram

It allows changes in the supply pressure or leakage in the pneumatics to be

detected.

Cycle counter histogram

(It provides a statistical analysis of the cycles and also information on the dynamic

stress of a bellows and packing.

Dynamic stress factor: percentage of the stress of a bellows and packing. Error

message „External leakage—maybe to be expected soon“ is generated if the

dynamic stress factor exceeds 90%.

General requirements

Diagnostics should be realized without any additional sensor systems

The valve is in controlled operation and the process may not be to interrupted!

Histograms allow to evaluate the valve travel [x], the set point deviation [e]

and the valve cycle counter as an automatic function without any setup in the

background

The valve signature function allows …

to detect possible changes in friction

to detect possible changes in the supply pressure or maybe leakages in the pneumatic supply

The Final position trend monitoring function allows to detect a fluctuating or creeping

zero point due to seat & plug wear or material between seat and plug

Dynamic Stress factor to monitor the stuffing box

Partial Stroke Test for on/off applications

Leakage sensor to detect inner leakages between seat & plug

Monitoring functions during the running process

Drive signal y

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Automatic y recording (monitor-function steady state) , assigning to a valve travel

class and averaged (long- and short-term)

Test function, test started by means of (E)DD, DTM or TROVIS-VIEW…

determines y at fixed travel positions, over the entire travel range (hysteresis)

Message generation

Reference with time stamp

Drive signal y

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Static Characteristic

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Test function Across the travel range possible

Test for static control response

Generates small steps of the set point. The response of the travel x in relation to the reference w is recorded after a short delay time.

Checking of both travel directions

Evaluation of

Min. dead band

Max. dead band Control valve

Average dead band

Storing last 30 messages in FF Positioner

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Total travel counter

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Temperature monitor

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Cycle counter histogram

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Counting of cycle frequency and

detecting of highness of span

Assigning of the travel performed

in the cycle to a determined

valve travel class

Number of measurement values

Average calculation

Long- and short-term diagram

Differentiation (stuffing box)

Self-adjusting

Adjustable packing

Bellows seal

Others max. cycle counter limit

Dynamic stress factor

Percent indication

Message generation

The operator needs to differentiate the

stuffing box! The corresponding values are

based on experiences in the SAMSON

development department!

Self-adjusting

Adjustable packing

Bellows seal

Other adjustable threshold

Dynamic stress factor [%]

The rate of wear of the selected stuffing box

will be calculated

New: 0%

Statistical defect 100%

Above 90% a message will be

generated

Long-term histogram

Cycle counter details

Data logger

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Storage of the last 100 values of x, w, e and y in the positioner

Adjustable sampling rate

Storing possibilities

Permanent (FIFO)

Trigger condition/trigger to process values and events

Start value adjustable

Trigger band and Trigger edge

Pre-trigger time

Deviation histogram

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Long-term histogram

Total number of values

Average calculation

Observation period

Short-term histogram

Sampling rate configurable

Average calculation

Last 100 values

x-> information, for instance:

“Shifting working range to closing or

max opening position”, “mostly closing

or max. position”, average value e

-> information for instance:

„Max set-point deviation”, average value,

connection positioner- valve

“Limit working range”

(upward, downward, sticking)

Diagnostic Expert Plus

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Monitor functions—valve in service (statistical information AUTO)

Data logger x, w, e, y (trigger defined start point)

Histograms x and e (long- and short-term histogram)

Frequency of performed stroke amplitudes and amplitude height

Cycle counter (long- and short-term histogram) with analysis

of the dynamic stress of the valve components

Final position trend shift and alternation of the zero point

(seat/plug solid particles/damaged)

Y = f (x) drive signal diagram (long- and short-term diagram)

Online hysteresis test friction changes

Open/close diagnostic, especially for On/Off valves during shut down

(application type open/close valve)

Evaluation of break-away time, transit time, valve end position

with time stamp and alarm function

End position Trend

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Automatic recording

When the valve reach the end position->

Valve position x, drive signal y and time

counter are automatically recorded

(if the end position changes)

User defined threshold value

for data recording

Last 30 values + reference

Reference value

Message generation

Zero point shift monotone down Differentiate: Above or

Zero point shift monotone up below the reference

Zero point alternate point

Samson/KNN/13th July 2012 · 23

Condensed State of Diagnostics

To enhance the overview, the state of the positioner is summarized in a condensed

state being made up from a summary of all classified positioner messages.

Classification of status messages

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Condensed state

Samson/KNN/13th July 2012 · 25

Damaged Diaphragms—Leakage in Pneumatics

A defective diaphragm leads to

leakage.

SAMSON/KNN/13th July 2012 · 26

Worn-out Seat and Plug—Trend of travel end

position

Worn out seat and plug changes the operating

range due to internal leakage.

Damage due to erosion (Abrasive media)

SAMSON/KNN/13th July 2012 · 27

Control Valves & FF Smart Positioners

Typical valve failures

Eroded seat and plug → internal leakage

Erosion of valve body → finally external leakage

Leaking stuffing box → external leakage

Increased / decreased friction → higher / lower hysteresis

Closing (Zero) point shifting → deposits on sealing edge

Change in opening / closing breakaway torque (e.g. ball valves)

Poor control performance → External leakages in the pneumatic supply

Samson/KNN/13th July 2012 · 29

Partial Stroke Test

The Partial Stroke Test (PST) is particularly suitable for the status-oriented

detection of malfunctions in pneumatic shut-off valves. („check on a valve‘s ability to

move“). A valve which is normally in its end position can be prevented from seizing up

or getting jammed.

It is part of the standard positioner features.

Especially for on/off applications (critical ball or butterfly valves, maybe safety related)

Partial Stroke Test without disrupting plant operation (e.g.: 100% to 90% and backwards to the operation point)

Prevent the valve from becoming stuck

Starting time scheduled or manually

Step or ramp function (adjustable ramp to prevent overshoot)

Configurable test abortion conditions

Condensed/test status acc. to NE 107

Documentable & reliable

Goal: maximize the time between full proof tests -> Cost optimization

Full Stroke Test over the entire travel range is always required!

Partial Stroke Test

PRTPFD DU 2

1

months

PFD

12

SIL threshold

6 18 24

test intervall without PST

test tintervall with PST

Thanks for listening…

THANKS.

SAMSON/KNN/13th July 2012 27