PLCScope is made to assist user in analyzing and troubleshooting PLC controls systems.  It is particularly helpful with demanding controls that operate complex and fast acting power processes as, steam and gas turbines, compressors, boilers, etc.  It has been field-verified with Siemens S7-1500/S7-300 and AB ControlLogix PLC however, it is designed to work with a wider range of other PLCs.

PLCScope consists of two parts.  One works in PLC itself (PLCScope-PLC) with the other part (PLCScope-PC), being a C# application that works within a PC that is LAN connected to the project PLC.


PLCScope-PLC comes as a set of standalone subroutines to be amended to the rest of the control software.  Its task is to keep sending data to the PC.  The data sent are current values of the control algorithm Analog and Boolean variables.  It is not sending all the variables but only those that are of any interest for monitoring and troubleshooting particular control system.  Those variables need to be specified by user.

The Analogs specified are being sent through as per a specified rate.  The rate can be set from as fast as the each PLC scan to anything slower than that.

All the Booleans specified are sent through at the same scan whenever any of the specified variables changes their state from FALSE to TRUE or opposite..

The PLCScope-PC is keep receiving process data and processing them further.  A part of the processing data is to save them to a fixed memory.  Additionally, various PLCScope tools for either on-line or off-line analysing data are available to user.

Live Watch



Live Watch is an online tool. It is continuously displaying selected signals.





Trender can be used both online and offline.  It is a complex tool for process data visual presentation and analysing.  The rate for analogs can be set from a single scan slower while booleans are taken at each scan whenever any of the booleans that are specified for trending  has changed its state.

Any .csv form external data can be incorporated together with data taken from the project PLC.

The default sorting form is a regular trend with process date against time however, any of the analog variables can be defined as the x-axis.



Historian saves project data to a fixed memory.  Analogs are saved at a second pace while every single state change of Booleans are saved as it appears.  The amount of the data saved depends only of the fixed memory size used.

Historian is enabled by default as soon PLCScope is connected to its PLC however, it can be disabled if required.

Saved data can be analyzed using trender or SOE viewer.  Trender can pick both Analogues and Booleans while SOE Viewer analyses Booleans only.




TrigLog continuously monitors specified signals at every PLC scan.  Among the signals specified there needs to be at least one Boolean trigger signal.  The maximum number of triggers is three.  Whenever any of the triggers changed its state all the monitored signals are dumped to a fix memory.

The number of consecutive scans being monitored is 1000 by default however, it can be changed by user. There is also some scans after the trigger saved as well.  The number of scans saved after the trigger  is 50 by default.

The signals saved can be analysed by Trender.


SOE Viewer 


SOE Viewer analyzes Boolean data recorded by Historian.   User can unambiguously determine what is the cause of some process event and what are the consequences.

SOE Viewer can export data as a .csv set to be further analyzed by Excel or else if needed.



If any further interest in PLCScope please drop us an email:

Turbine Dynamic Simulators

Turbine Dynamic Simulators are a range of stand alone C# developed software packages that mimics various turbines dynamic behavior at a reasonably high fidelity level.

It models turbine as a lump system utilizing in house developed relatively simple robust and fast numerical methods.

There are two links at the bottom here.  A link to a simulator resembling the core features of an imaginary steam turbine with one controlled extraction. The image bellow that one is a link to a YouTube video that demonstrates some of the simulator features.

Apart from various steam turbines there are also simulators for other turbo-machines that have been mastered.  A core generic versions of gas turbine, water turbine, pump and compressor simulator have also been developed and is available to be tuned to resemble any such machine available at the market.

The simulator creates a reliable closed loop environment that can have all kind of applications.  At present it has been proven as a perfect tool for developing and pre-commissioning PLC turbine control software as well as for operators training.

The simulators are able to communicate to other Win applications, as various PLC emulators or else.  We have already executed projects with the simulator communicating to the PLC emulators namely,  Simatic S7 (a peper here) and AB CompactLogix.  That can be extended to any other PLC having it’s emulator.

Drop me a note for any additional info about this application.




Here are few presentations covering turbine control basics.  They are focused onto the process aspect of the whole turbine control thing.

These days I see sharp young guys with a deep and detail PLC knowledge doing controls.  Sometimes I don’t see the same strength at the process control side.

Such a discrepancy is easily understood as the PLC technology is so easily accessible these days.  Just Google alone can bring you to all the nitty gritties of,  Siemens, Allan Bradley, ABB, Honeywell, and others.

However, it’s much harder to master the process control side.  It gets to you only through years of hands-on dealing with the matter itself.

Hence, here are some basic process control things related to turbine controls. It is put into three presentations already delivered to their targeted audience a year ago.  The feedback was quite positive all together.

The presentation are:

    Selected Fundamentals Related To Steam Turbine Controls;

Click to cover page link gets you to each of their .pdf versions.




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.