Turbomehanika successfully retrofitted the controls for two identical steam turbine trains that are parts of the Old Nitric Acid plant in Petrokemija Kutina.  The trains are manufactured by Escher Wyss and commissioned back in 1968. Operating continuously since. Each train consists of a steam turbine, two process compressors and a gas expander all coupled together.  The steam turbine being the main drive with the expander supplementing it by expanding the process product gasses through.

The scope of the retrofit was to replace the existing steam turbine control and the compressors antisurge protection with a new PLC based Integrated Turbine Compressor Controls (ITCC) system.  Siemens SIMATIC S7-1500 PLC together with Bently Nevada Adapt 3701/55 ESD are used as the PLC hardware.

Turbomehanika have been the main contractor for the job with Arirang and Intea being subcontractors.

The Old Control System

The old control system consisted of hydraulic turbine controls and compressor antisurge protection. They were both using the same 7barg hydraulic/lube oil system.

Steam Turbine Controls had a flywheel isochronous governor operating three steam control valves actuated by a linear hydraulic servomotor.  The governor and the trip unit were both integrated together at the steam turbine front pedestrian.  The project spec required to use the existing trip device.  Separating one from each other was quite a challenging task that required gaining a deep knowledge of the Escher Wyss control concept. The governor was cut out while the trip device and the servomotor remained a part of the current system.



Compressor Antisurge System had a control unit and the blow-off valve operated by a hydraulic servomotor.  The control unit was cut out while the blow-off valve with its servomotor remained parts of the current ITCC.

All through the recent years the customer were keep experiencing issues with the antisurge controls.  It would open the blow-off valve when it was not supposed to causing costly plant shutdowns.  While commissioning the new controls we found that in some operating modes compressors are expected to run quite near to the surge region. The old antisurge controls were most probably not being able to deal with that operating situation.



Here is a turbine engineer web site.

While dealing with the Cocohouse web site I built a bit of web design skills.

Internet is a great thing that made our world smaller and all the human kind closer to each other.  As turbine people are also some sort of human kind the internet made us closer as well. 🙂

Hence I decided to put online some of my turbine (control) expertise gained through a lifetime of hands-on experience in the power engineering.  To be used by turbine engineers or anybody who wants to become one.

Putting online some papers and web applications that are available for your non-commercial use.  The applications are listed and briefly explained below:

  • Steam Turbine Thermodynamic
    A simplified core steam turbine design.  The calculus is based on input steam parameters and design conditions.  It predicts the design operating point and the expected output. It also calculates any off- design operating point and predicted output in a case of inlet pressure deviates from the rated one. This kind of assessment is particularly required in geothermal engineering world.
  • ThreeP (bang-bang)
    A time simulation with a bang-bang loop controlling the water level in a vessel.  Was taught this type of bang-bang loop by my teacher prof Sherman back than at the university.  Believe it is quite superior to whatever I’ve seen around since. This application allows you to tune the whole thing, play with it and understand how ThreeP works.
  • TMC Playground
    TMC stands for Turbo Machinery Controls.  This application demonstrate some basic TMC features. It simulates two turbo-generators that can operate in all kind of real life scenarios.  Also demonstrates some advanced load sharing features that I developed through the years of dealing with the matter. Its User Manuals explain well how to go around the playground.
  • Synch Playground
    This application simulates synchronizing generator to grid in a manual mode as it ones used to be.  These days AutoSynch unit does it all by itself.  The simulation gives operators and engineers idea of what is actually happening during synchronizing process. It has its User’s Manual as well.

There is also a part here called Linear Control Theory. That part was put together by prof. Šerman with me just shaping it up for the web publishing. Had a privilege to be prof. Šerman university student and later on worked with him through some tough projects.