Gas turbine control system upgrade


Thread Starter


I am planning to upgrade our gas turbine (GE type 5001) control system which is speedtronic Mark II by latest one. I have received offers to replace them by MACH 7- Sematic S7 - Allan Bradley Sentinel. Which one of them is preferred and if have a comparison between them it will be helpful?

I'm pretty sure I'm going to regret this response, but here goes.

The choice of a turbine control system should almost <b>NEVER</b> be based on the manufacturer of the hardware or the cost of the project.

Any decision should be made based on the experience of the company offering the control system--including hardware; programming for turbine control, protection and monitoring; turbine control system installation and commissioning; training; drawings and documentation; and after-market service. Forced to choose the top two criteria from the above list, I would have to choose demonstrated experience with turbine control system programming and proven expertise in turbine control system installation and commissioning.

I am being turned in this regard, but many PLCs are now capable of executing some (but not all!) turbine control and protection functions. So, while a purpose-built turbine control system (such as a GE Speedtronic Mark VIe, for example) is really the best choice for a GE-design heavy duty gas turbine, if the company offering a PLC-based control system has proven experience and demonstrated expertise and can provide after-market service and support a PLC-based option might be right.

<i>Might be right,</i> and here's the other major consideration when choosing a turbine control system: What is your most important criteria? Do the machines need to be on-line 24x7x365 with very high reliability? Or, if necessary, can the machines be shut down to replace control system components? You might be able to find a turbine control system that meets your criteria that is not from the OEM.

Finally, a top consideration should be after-market service and support. Does the company offering the turbine control system have a capable field force to service and support the equipment, both during and after the warranty period? Sure, there are thousands of people who can program PLCs, but how may of those really know turbine control and GE-design heavy duty gas turbine control philosophy and practices? Not many.

So, experience in applying and commissioning and supporting the control system hardware (regardless of the manufacturer of the control system hardware) for the application--which is very specific--is of critical importance. More important than the manufacturer of the control system hardware.

There are actually several considerations--but the manufacturer of the hardware should not be at the top of the list of considerations. For any company you are seriously considering--regardless of control system hardware they are proposing--<b>GET ***AND CHECK*** REFERENCES!!!</b> Even if you're going to consider the OEM's purpose-built control system, be sure to get and check references.

Whatever you decide (and we hope you'll share your deliberations and decisions with us here at, the experience and expertise of the company offering the control system should be the primary consideration.



Is there any particular reason for upgrading the Mark II controller other than that the system is obsolete because we come across many users who think of an upgrade due to lack of availability of spares and service even though they are happy with the controller.

If this is the case mail your woes to [email protected] as we may be able to help you.
CSA, I was going to reply to this post, but since the poster asked about controls retrofits and then mentioned three companies of which none was the OEM I suspect where he is going.

Ahdash, I am with CSA in saying that I still side with the OEM. They designed the machine, built the machine and should know the most about it. Like CSA I believe that the PLC's or PAC's or whatever they are being called these days can perform most functions of controlling a turbine. But can they do synchronizing, vibration protection, backup overspeed, etc. All the things that a new Speedtronic system can do without intermediate conditioning modules? Will the logic written perform exactly as the original GE logic? How can they prove it?

This thread could go way off course, so I will stop now. Do I have any experience with the aftermarket systems you mention, no. Will they perform and have a demonstrated life like the current Speedtronic system now, who knows? Will any of them cost less than a system from the OEM, most likely yes. So if you are choosing based on cost I know what will not being going in as a replacement.
Good luck and let us know how you proceed.
The OEM will almost always say that "your system is obsolete and must be upgraded". And the beauty of the world is that there are often independent third party outfits that will still support the old control systems. is one that I know of (no affiliation).

The GE Speedtronic control system may be proven, reliable, etc...but it also is proven to be a headache to repair when problems occur UNLESS you like to spend $400 an hour for a GE TA (and then hope you get one that is competent).

Having had the displeasure to work on a few control systems...I honestly believe GE stands for Good Enough.

In today's modern world, there are often many other options besides the OEM. The OEM will ALWAYS be able to support you...if you have enough money.
Dear Adash,

Please apologize my poor english first. We having 12 numbers of MACH 7 installed in 2 of our plants, running GE Frame6 gas turbines. The installation was performed in 2004 to 2006. Originally we had GE Speedtronic MKII and MKIV turbine controls installed. This controls were retrofitted by the MACH 7 control system. We also got a new HMI called TMOS to operate all of the 12 gas turbines.

Up to now, we did not face any problem with the installation. You mentioned, you have a quote for a MACH7 system in hand, so for sure you have also a reference list. As i don't want to surface here, because our company regulations are very strict in this matter, i suggest to contact my company officials for a statement.
But back to your questions:

The MACH7 is using the original sequencing and protection philosophy from the GE turbines. It is using PLC components, but programmed in a different way. I don't know exactly how the modifications work, but at the end it is a multi tasking system, which runs sequences in parallel, like the OEM philosophy. The overspeed protection is done TMR at the IO processing level, and 2 out of 3 in the sequencing too. So a 2 stage electronic protection. As we have a mechanical overspeed bolt, no additional requirements were necessary by the TÜV authorities to approve operation. The vibration monitoring is done inside the sequence, signals are provided by signal conditioners. Which i think is not really a bad thing, like stated often as a pro OEM speedtronic argument. Every channel has its own power and protection circuits. So if some fail, only one channel fails, not the whole card.

The servo and LVDT controller loops are operated directly with standard Siemens components. The digital servo valve regulator is 8 channel TMR, and runs at 200Hz. So all our 2 coil servos, where changes to 3 coil MOOG servos during the retrofit. But as stated by all the others here, you can write a book of pros. and cons. of PLC based turbine controllers.

During the years we had many service companies on our site doing mechanical overhauls and commissioning works. At the beginning, we were afraid, that companies who are not familiar with the MACH7 are unable to handle it. But due to the fact, that any Speedtronic guy, who knows MKIV or MKV or even MKVI is able to read the sequence and handle the tools, this was absolute no problem.

out of my view i can say, we are very happy with it.

There is no perfect turbine control system. Period. The Speedtronic control system suffers from lack of documentation, and, worse, poor documentation. If people had good documentation to refer to, and if terms were used consistently in GE-design control systems, Speedtronic control systems and the programming/configuration of them would be much easier to understand--not only for owner/operator technicians, but for GE field service people as well! Alarm messages are cryptic and there is no useful help feature--unless you pay extra for it!!! (And some companies pay for it, believe it or not!) Worse, Diagnostic Alarms are even more poorly documented (though that's improving in the Mark VI and Mark VIe in Vol. III of their respective System Guides).

The lack of documentation and poor documentation isn't just limited to the Speedtronic, though. Basic turbine and auxiliary operation is generic and lacking. Many problems that are attributed to the Speedtronic are caused by a lack of understanding of how turbines and auxiliaries operate. People perceive (think) this or that should or shouldn't be happening, and there's almost no documentation they can refer to for help.

krush's comment's with respect to the OEM are pretty much spot on. The Speedtronic really is a very good control system, but when there are problems it's sometimes very difficult to find knowledgeable people to help.

And there is the cost. But, lower cost doesn't always translate to better quality.

As I said, I'm being turned with respect to using PLCs/PACs for turbine control. I would rather use a purpose-built control system, such as the Speedtronic, but I have a lot of experience with it and with GE turbines and auxiliaries. I can understand how people can be soured on the system, but when you find a site that was properly commissioned and has good technicians that dig and strive to understand the equipment (turbine, auxiliaries, and control system) you will find that people are very satisfied with Speedtronic control systems. I know of several sites that had some really good technicians and operators who kept the equipment running and could respond to problems quickly and competently, and when those people retired or left the company all of a sudden there were "lots" of problems with the Speedtronic control system (problems which weren't really problems; they were perceived problems in most cases). Same site; same turbine and auxiliaries; and same control system. Just different people.

On the subject of "obsolete and must be upgraded", well, that's a salesperson's job, right? However, the troubleshooting tools available in the new control systems are worth the price. Having worked with Mark II and Mark IV control systems early in my career I can say unequivocally that the trending capabilities available in Toolbox and ToolboxST are extremely valuable. In the past we had to use paper chart recorders, and couldn't always "get at" every signal. Of course, that made us better troubleshooters, being able to separate the wheat from the chaff, but it was difficult and resulted in a lot of unnecessary card-swapping and calibrations.

It would be great if there were a perfect turbine control system, or a perfect computer operating system, or a perfect automobile. But there isn't. When choosing a turbine control system, there are a lot of things to consider, and there are a multitude of vendors offering systems. But, the hardware shouldn't necessarily be the highest consideration; it's the knowledge and experience and expertise of the company providing the hardware. There's where the value is--not necessarily with the hardware. The OEM has that, but it's very difficult to find--again, as krush has said.
As usual CSA's answer is right on the mark!

In my opinion it boils down to a system that has:

1) Code that is written well and documented.

2) Hardware that is reliable, robust, and will be supported for many years.

3) People exist that are familiar with the logic, hardware and understand how it should all work.

4) Software that is easy use and has good tools for diagnosing and finding problems when they develop.

Gregor provides a nice response for Ahdash, hopefully more will follow.

If there was one perfect system out there everyone would be using it.
Although krush's comments may have been true in the past, GE is working hard to communicate our GE ControlsCare Services lifecycle approach which allows the operator to decide when it is beneficial to upgrade. Just a couple examples... we offer repair and exchange for Mark I, Mark II and Mark IV parts. These parts are shipped with new part warranties and meet all OEM specifications. In addition, moving forward, we will offer services for the Mark V to support operators that want to continue operating the unit and don't see benefit from the improved processing power, troubleshooting, visualization, etc. We are currently running a series of webinars that introduce each of these offerings and will be specifically addressing Mark I/II and Mark IV units later in August. To see the full webinar series you need to log into GE Controls Connect and register under the NEWS-WEBINARS link. Past webinars will be posted for on-demand viewing with written Q&A.

The title of the webinar series is DISCOVER THE CURE FOR OBSOLESENCE. I hope many owners/operators will find it valuable.

CONTROLS CONNECT NOTE: If you have a GE SSO#/Login and are a GE turbine operator, business associate or EPC firm, please send me an email at [email protected] with the subject "Controls Connect Access" and include your SSO#, Name and Company. Note that we do not accept generic email addresses (e.g. @yahoo, @hotmail, @gmail, etc). Company based email addresses are required for security reasons. Your registration will take approximately 3 days. If you do not have a GE SSO# you can register at or just perform a Google search on "Controls Connect". Just click on the register button to start the process. Registration forms should require less than 5 minutes to complete. If you have any questions feel free to contact me at [email protected]

I am the Product Line Leader at GE Measurement and Controls.

man to man help


regarding to the post question I would like to advise you to upgrade your control system by GE Mark6 it is best one as I did this upgrade with same Gas Turbine type (frame 5). so I think you must to contact GE agency in your country they will provide you by the best information about Mark6 or Mark6 modified. (there is new speedtronic mark6 with some modifications about first generation of Mark6 you can read about it on GE web site). by the way I'm not control systems provider I'm working in power station (generation plant).

Dimitris Kostis

Dear Sir,

I am interesting in a GE Gts control system retrofit. Can you please help me with this MACH 7 control system. Where can i find details for this system? Contact info for an integrator working with this system fro the replacement of an old GE control system of existing GE GTs and an old ABB GT?

Thank you in advance fro your feedback and help.

Best regards
Dimitris Kostis
I&C engineer, Thermal Power Plants
Dear Dimitris Kostis,

please take a look at the website There you can find some further information about Mach7 and the manufacturer. Our contact persons are Thomas Finstermann and Jochen Burgstaller.

Best regards

Maarten Swets


Another option you can explore is to contact one of Woodward's Recognized Turbine Retrofitters. This would give you the benefit of having dedicated turbine control hardware with proven control software within a similar price range as a PLC-based solution.

You can find the Woodward RTR's at or you can contact [email protected] and we can guide you in the right direction depending on your location

(Sales Manager PM Control)

While this note doesn't matter to the original poster, it is important to others who might be considering a Woodward turbine control.

This is very difficult to explain, but Woodward turbine control offerings for the GE-design heavy duty gas turbine market are very limited because of contractual agreements which came into existence when GE purchased the turbine control <b><i>engineering division</b></i> of Woodward more than 10 years ago.

GE didn't purchase Woodward; GE didn't purchase the turbine cocntrol division of Woodward; they only purchased the turbine control engineering division. Woodward continues to make turbine controls, and all of their other products. The agreement between GE and Woodward prevents them from selling Woodward turbine controls for certain applications. Woodward are only allowed to sell turbine controls for Frame 5 or smaller GE-design heavy duty gas turbines. They are "free" to sell turbine controls for any other manufacturer's gas turbines, and for Frame 3 or Frame 5 GE-design heavy duty gas turbines. But they are not allowed to sell for use on Frame 6s, or Frame 7s, or Frame 9s.

GE does use Woodward controls for some smaller steam turbines they sell or retrofit; they do use Woodward controls for some aircraft-derivative gas turbines they sell.

A further clarification is that they can really sell their turbine control hardware to anyone for any turbine, but they can't sell their programming software to build an application for GE-design heavy duty gas turbines larger than Frame 5. Hardware without configuration and programming software doesn't do much....

Having said that, Woodward hardware is compliant with several international standards for programming, and if someone wants to develop their own turbine control application using some programming application other than Woodward's GAP they are free to do so. But most people dont' want to develop their own turbine control algorithms and "blocks" so that's probably not realistic (and GE knows that).

Isn't capitalism wonderful? And so easy to understand, too.


CSA are you sure this is the case?? This is very interesting if so. The purchase of Woodwards Global Controls Service was 12 years ago, and i'm certain the was a limit of non-compete for only 5 or 6 years which has since expired. Nevertheless Woodward has changed focus and primarily concentrates on the various OEM. There is very little to no overlap where they now compete.

If you wanted custom software they would decline and introduce you to their turbine retrofitters. You can buy anything hard or soft from there distrubutors/retrofitters. There Altas platform based GTC family of controls is fixed software but field configurable and suitable for smaller turbines such as the Ge Frame 3 and 5, Ruston TB5000 Solar turbines etc. The only hardware rights GE obtained were products for the hydro market.

Woodwards GLobal Control was after market retrofit arm of Woodward. The purchase was very strategic one which allowed them to purchase a potential competitor and then gave them access to two different talent pools.

The first was the creation of GE Global Control Service ... Out of Control ... errr... I mean Optimization and Control...Measurement and whatever they are called today. Whilst another portion helped build the IFS organization which was expanding due the purchase of the various turbine packagers. And then there are those that wouldn't have anything to do with it and joined the end users.
I am sure. It is not easy to understand, but I am sure.

GE buy a LOT of valves and other components from Woodward these days, and I'm sure Woodward are loathe to upset the apple cart.

The original contact, as you say, has expired; but a new contract permitting the sale of controls for Frame 5 and smaller machines is now in place for some period of time. And, it's not technically hardware, but more the software that is limited. And what is hardware without software to configure and program it?

As you say, the GTC platform is "configurable" for Frame 5 and smaller GE-design heavy duty gas turbines. That's what's being permitted. They "configurable" portion is the way that the programming application is prevented from being used for larger GE-design heavy duty gas turbines.

Interesting choice of 'Author' pseudonyms, NoWayBigDimLightBulb....


You started this thread many months ago. What have you decided with respect to a vendor/supplier of an upgrade turbine control system for your site?

Have you listed the important requirements for your unit? Meaning, does your turbine need to be running 24 hours per day, 7 days per week, 365 days per year? Or, does it just need to start reliably when required and operate for a few hours or a couple of days?

Because the choice of a turbine control system should start with this analysis of how your turbine is, or is going to be, operated. If you need 24x7x365 reliability, then you need a high degree of redundancy (TMR or DUAL Redundant) so the unit can be kept running to replace major components of the control system.

If your turbine just needs to start reliably when required to do so and operate for a few hours or a couple of days, then you probably don't require a high degree of redundancy.

Redundancy can be very expensive, in both initial cost, and in spares. Remember: A TMR control system, with "three times" the number of components (cards, controllers, etc.) will have three times the number of failures of the same control system that does not have triple redundancy. That's right--for the same failure rate of each card, when you have three sets of each card or component you will have three times the number of failures, meaning you will need to have more spares to keep the system running. Note that the failure rate doesn't increase; but the fact that there are three times the number of cards and components failing at the same rate means that there will be more failures (as much as three times more) in a TMR system than a SIMPLEX system built with the same cards and components.

Now, the failure rate can be improved by proper maintenance and attention to details, such as grounds and Diagnostic Alarms (if the system has them), but a multi-modular redundant system is simply going to experience a higher number of failures than a control system with a lower redundancy level.

The difference with a TMR control system versus a SIMPLEX control system, and some DUAL Redundant control systems, is that with most TMR control systems most components can be replaced while the unit (turbine and driven device and auxiliaries) are running--meaning that it's not usually necessary to shut the unit down to replace a failed card or component. This means there will be little to no loss of production/generation while the failed card or component is being replaced with a TMR system.

However, if a major card or component of a SIMPLEX system (and many DUAL Redundant systems) fails, the turbine will trip and there will be a loss of production/generation while the repair is being affected. If a loss of production/generation can be tolerated when a component fails then a high degree of redundancy (and initial- and spare parts costs) are not necessary.

So, the two most important things to consider when undertaking a turbine control system upgrade are, first, how is the turbine going to be operated after the control system is upgraded? IN other words, what level of redundancy is required to provide the required level of reliability and protection of loss production/generation that gives the owner the best feeling of security at the least cost.

The second thing to consider is does the supplier have the knowledge and support required to implement the control system upgrade in the time required and then provide after-installation service and support? In my mind, this is one of the most important aspects of the project. Because, there are any number of companies that will claim to be able to provide a turbine control system, but if they can't implement the retrofit/upgrade on time and within budget then the project ends up leaving a very bad impression with everyone. And, if they can't provide after-installation service and support then the control system may become a very great liability in the short term, not to mention the long term.

Don't be fooled by OEMs who claim they, and only they, can provide the control system to properly control and protect your turbine and driven device and it's auxiliaries. In many cases, the OEM has a very good product--but where they fall very flat is in the removal of the old control system, the installation of the new control system, the commissioning of the new control system, and the start-up of the new control system. And, it's not just the OEM that has this problem; many suppliers suffer from an inability to complete the project in the field in the allotted time with proper results.

Control systems today can be implemented with many different types of hardware and software, but it's the installation and commissioning and start-up that are the real critical portions of the project. Do your homework and get references from anyone offering you a turbine control system and check with those references to see if the project was implemented in the field on time and with proper results. The best hardware and software aren't going to install themselves and commission themselves. Installation and commissioning and start-up requires knowledge and experience and planning and an ability to execute.

After you decide on how the unit is going to be operated and what kind of control system (level of redundancy required for the level of reliability required), you need to then focus closely on the supplier--not the components (hardware and software) but the supplier of the components. This is where the real value, and the hidden costs, are contained.

Please write back to let us know how you are progressing with your decision.