Process stability and tuning

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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Contek Systems Ltd,
25 Wilson Road,
Banchory,
AB31 5UY

+44 (0)1330 823643

Try my well-known Process Identification and PID Tuning package U-Tune.

Click here for details and screenshot.

See my FREE tuning calculator.

Download here.

I have written several tutorials on the practicalities of process control.

Click here for links to our tutorials.

Check back from time to time. New articles will be added as time permits.

Note: emails can be accessed offshore - telephones can't!

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Consultancy Services

I am a specialist process control consultant for the Oil and Gas industry. My quality statement is 'to be considered a valuable asset to my client's business'.

This means providing more than just loop tuning. The following sections introduce some of my core oil and gas activities which include process optimisation and de-bottlenecking, flare reduction, improvement of produced water systems, compressor surge line mapping and slug mitigation as well as the 'conventional' control engineering tasks of PID tuning.

Please contact me for further details (JohnGreene@contek-systems.co.uk).

Process Optimisation

It is often said that 90% of process controllers have not been correctly tuned and many loops still retain their factory default settings despite years of inadequate performance. Every controller should be optimised for its specific environment with consideration given to the process conditions, startup/shutdown requirements and process dynamics.

Then again, the root-cause of many control problems can be rather more subtle than poor PID tuning: see this tutorial for a selection of some control-related problems solved by Contek over the last few years.

Contek Systems Ltd has been directly responsible for the performance improvements of many assets throughout the North Sea. Improved process stability is not only beneficial to the operators, but also improves production and reduces environmental emissions.

Simulation and Modelling

Dynamic simulation, mathematical modelling and optimisation techniques provide detailed insight into the process dynamics to facilitate the design of suitable control schemes.

Contek Systems Ltd has experience with Hysys Dynamics, General Algebraic Modelling System (GAMS) and Matlab.

Gas Compression

Gas composition and process conditions generally alter as the field ages. If the compressor control system is not retuned for the new conditions, inadequate surge protection, unstable control and excessive recycling can occur.

Contek Systems Ltd has considerable hands-on experience with anti-surge and performance controllers from CCC and other vendors, including surge line mapping and surge controller tuning.

Slugging

Standard constant-gain oil level controllers on slug-catchers and separators prevent the vessel from 'washing out' liquid slugs and induce instability into the downstream process.

Contek Systems Ltd has experience of non-linear control techniques which enable slug-catchers and separators to do their intended jobs. These techniques can usually be implemented in the existing control system with no modifications to pipework or instrumentation. Algorithms have also been configured in readily available panel-mounted industrial controllers.

Fault-finding

The root-cause of many process instability problems can be traced to incorrect implementation of commonly-used control techniques, such as split-range control, low- or high-output selectors, signal filters and output clamps. These techniques are often specified in the design phases without any true understanding of the limitations.

Contek Systems Ltd has considerable experience in correcting the implementation of these and many other issues.

Offshore and site work

Much of my work is carried out offshore or onsite, generally requiring a visit of four to five days during which the critical process and control issues will be identified and improved. High speed data acquisition equipment is used to collect detailed plant data for analysis and optimisation.

Please contact John Greene for the latest schedule of rates (JohnGreene@contek-systems.co.uk).

Programming

I can assist in designing and implementing Windows^TM based software packages for any process, control or mathematical application. Take a look at my current product range.