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Contek Systems Ltd, Aberdeen,
UK
Control engineering
consultant for the oil and gas industry.
Process control, de-bottlenecking, compressors,
slugging and control system PID tuning.
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Recent press releases and
other news are available
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Contek Systems Ltd,
25 Wilson Road,
Banchory,
AB31 5UY
+44 (0)1330 823643 |
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Try my well-known Process Identification and PID Tuning package
U-Tune.
Click
here for details and screenshot. |
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See my FREE
tuning calculator.
Download
here. |
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I have written several
tutorials on the practicalities of process control.
Click
here for links to our
tutorials. |
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Check back from time
to time. New articles will be added as time permits. |
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Note: emails can be
accessed offshore - telephones can't! |
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Home page |
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U-Tune PID
Tuning Package (Version 2)
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Process
measurements in the process industries are
typified by excessive noise and disturbances. In
these environments, automatic tuning software
often fails to identify even the most obvious
characteristics of the process response resulting
in poor selection of tuning parameters.
U-Tune
minimises this inaccuracy by helping you to
select the primary elements of the process step
or pulse response.
U-Tune
calculates the tuning parameters giving options
for PI and PID control, all the common controller
algorithms and parameter types, and two sets of
parameters, one for fast and the other for slow
responding loops.
U-Tune lets
you compare the results from a series of tests
and provides you with the best parameters to
enter into the controller.
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To install the
software, click on the Download button. When
the dialog window opens, select Run and
follow the instructions. |
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Process
Identification
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The image on
the left shows the Identification view with data
captured during the step testing of a compressor
anti-surge controller. Click on the image to
enlarge.
The upper
trend shows the output to the recycle valve (blue
line) and the lower trend shows the process
variable (also blue line) responding to the
increased gas flow. Note the considerable noise
on this trend. The valve is clearly also sticking
slightly. This meant that automatic tuning
packages failed to give consistent
results.
By moving
the sliders, the start and end of the output step
have been identified (magenta line on upper
trend) as have the start, end and shape of the
process variable (magenta line on lower trend).
Note the way the output step has ramped up
gradually at first and then faster. This is
because the output is driven using up/down
pushbuttons on the controller faceplate.
The primary
characteristics of the step test are given in the
box at the bottom of the screen.
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Controller
Tuning
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U-Tune
supports self-regulating and integrating processes,
two- and three-term controllers (PI and PID),
ideal, series and parallel algorithms, and all the
common forms of gain, integral and derivative
terms. Two sets of tuning parameters are provided,
one set for processes needing a slow response such
as temperature controllers and the other for
processes requiring fast responses such as flare or
minimum flow recycle controllers. |
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Model
Management
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One step test
is rarely sufficient. Generally, a test must be
repeated three or four times. The Manager view
collates the test results into a tabular format
giving the process characteristics and tuning
parameters for each of up to ten tests.
The records
can be selected for display, deletion or editing.
An average set of process characteristics is
calculated from the test results and the
corresponding tuning parameters are generated.
Records can be included or excluded from this
calculation.
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The tables
in the Manager view can be printed or written to
a text file for incorporation in reports
etc.
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Text File
Conversion
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U-Tune will convert any
column-based numeric text file (comma, space or tab delimited fields)
into its internal format, so data from many sources can be used.
The internal format is the same as the waveform files of the popular DATAQ data
acquisition equipment (www.dataq.com), so if this is the
device you use to collect data, no extra conversion is
necessary.
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Help
Pages
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U-Tune is
simple to use, allowing you to concentrate on the
vital controller tuning. But if you do need a
helping hand, the U-Tune Help pages are no more
than a function keypress away.
Please note
that some of the images on this site show data
collected while tuning controllers on compressors
and other rotating machinery. While Contek has
considerable experience in process tuning and
optimisation, you are reminded that utmost care
must be taken when working with these and other
devices.
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