Siemens TMR vs Mark V/Woodward TMR

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Thread Starter

Martin

One of our clients is considering to use a TMR type Siemens control system for the control of their GE Frame gas turbines. How would the Siemens TMR philosophy, architecture and hardware compare to a lets say Mark V TMR or Woodward TMR system?

Are there any other advantages of using a Siemens control rather then GE or Woodward?
 
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bob peterson

There is a big advantage to GE. They can claim anything that goes wrong is the Siemens control system fault. Why would anyone do something this stupid? You will inevitably end up with several field reps standing around pointing fingers at each other on your dime with your machine down.

--
Bob
 
I don't disagree with Bob Peterson's last sentence, having been there and done that.

Everyone's interpretation of TMR is slightly different. Everyone's application of TMR is slightly different. I would imagine there are subtle, as well as significant, differences between Siemens, and GE's versions of TMR.

The critical issues to be investigated are droop speed control, Isochronous speed control (if required), exhaust temperature control, and combustion monitoring. Can Siemens adapt their control philosophies and practices to match GE's, or can they explain why their implementation is at least as good as GE's implementation, if not better?

I've seen several different control systems applied to GE-design heavy duty gas turbines, auxiliaries and driven devices with some very mixed results. Including Woodward (with mixed results). It's all about the people programming the control system and how well they understand some basic concepts (droop/Isoch), and GE's version of exhaust temperature control and combustion monitoring. Most everything else is relatively easy; it's just basic relay ladder logic which can be converted to many other styles of programming.

But, if the transition between droop speed control and exhaust temperature control isn't smooth, or if exhaust temperature control isn't (meaning there is <b>no</b> CPD bias, just a single load limit), and if the combustion monitor fails to adequately detect a high exhaust temperature spread and warn the operators/trip the turbine, then that's where the real problems begin.

Everything else (overspeed trip; low-low L.O. pressure trip; high vibration trip; loss of flame trip; etc.) is pretty much the same for most prime movers.

If the Siemens control system can deal directly with the LVDTs and electro-hydraulic servo-valves without the use of "converters" between the Siemens hardware and the field devices, then that's a plus for them versus, say, a PLC-based system.

I don't think Woodward can contractually offer a control system for most GE-design heavy duty gas turbines, although I've heard recently (third-hand) that they can now sell systems for Frame 5s, but that's hearsay and would not be admissible in a court of law in most civilized nations. So, I think a Woodward system (and I don't think they offer a TMR version) is not a real option (unless this is for Frame 5s and the rumours are true).

It's been said many times on control.com: Just about any programmable controller can be made to work on just about any application. The real proof is in the after-market service and support. I would imagine Siemens probably has a pretty good idea about turbines and auxiliaries, and from what I know of their control philosophies and practices they aren't that dissimilar to GE's, and if their hardware can work directly with the I/O used on GE-design heavy duty gas turbines, then that's a plus, as well.

You client would do well to get the names of some reference customers who have used Siemens control systems on similar machines to the one they are considering using Siemens equipment on. And, then contact those people, even possibly visit the site(s), and get the real low-down from the people who are responsible for operating, maintaining and troubleshooting. I've been to sites where the site personnel can't stand the equipment purchased by a manager in their company. And that manager is highly satisfied with the equipment. So, talk to the people who actually use the equipment.

This is not a choice to be taken lightly.

If you want the least headaches and the highest probability the new turbine control system will perform nearly identically to the old control system and will follow the OEM's control practices and philosophies then the choice is simple. If there are other considerations--and cost should not be the guiding factor here because initial cost is not the same as life costs!--then those other considerations need to be factored into the decision.

Good luck to your client!
 
J
One other important note is that you should not be comparing the GE Mark V TMR, which is ~20 years old, to a current TMR system. To make a fair comparison you should utilize the GE Mark VIe and the Woodward MicronetPlus when comparing against a new Siemens TMR control. Make sure the technology vintages are the same.

Please note: I am the Product Line Leader at GE Measurement and Controls. I would rather not provide additional commercial information in the forum since I don't believe it is the desire or intent for this community.
 
Thanks Bob and CSA,

My concern is mainly about the hardware architecture of both their T3000 and S7 system. I've heard S7 can operate in a customized TMR mode, but since it's never really been designed for the purpose I wonder whether it really works great or whether it's just a patchwork method.
Comments on the S7 TMR system as well as on the T3000-TMR system architecture are welcome.

I understand Woodward has a special control software set dedicated for the Frame V turbines to upgrade from Mark I/II. (this application is a Frame V). They have indeed opened up the market for Frame V retrofits and some of the LM's. I have however no idea how their TMR, which is mostly used on critical steam turbines, compares to the Siemens s7 or ST3000 TMR system.

Thanks for thinking along!
 
Martin,

I would like to comment on your question, offering some facts as I understand them, and some opinions as well.

I do not have any experience with Siemens systems. My experience is with Speedtronic, Micronet, ABB, Advant, and Allen Bradley products mostly.

I can't comment on how other manufacturers handle TMR as compared to GE. I don't feel like I can really fully explain how GE controls TMR, as it has evolved somewhat as the Speedtronic has evolved.
I would ask what part of the TMR equation your customer is really looking for? Is it the ability to keep the machine online in the event of certain component failures? Is it some of the overspeed/overtemperature protections that are offered by TMR architecture? As you said TMR can be marketed in many different ways, it all depends on what you are looking for from the system.

We upgraded a couple older MKIV Frame 5 machines to GE MKVI simplex controls several years back. These machines are peakers that are not called to run often and so we chose to install Simplex rather than TMR to reduce the system cost. The system has worked well and has not had a controls failure that caused a trip or impacted unit availability in the 8 years since the installation.

At a separate site that runs 24/7/365 and is TMR we have benefited from being a TMR system when we have failed a card (Servo card in this case) that would have most likely caused the unit to trip.

Lastly I will say that I don't personally feel that a PLC or DCS system should be controlling a turbine. I am not saying that GE or Alstom or others are perfect, but I believe if they built it and designed controls for it, then they know whats best for the machine. I could go on for a long time on this subject, but will not at least for now.

Good luck with your selection. Hopefully there are some others who can comment on the other systems.
 
Dear Martin,

I heard GE TMR was introduced in Mark IV to compensate for their frequent failure on the electronics card. Then it became a popular design that it was inherited by Mark V and VI.

If you contemplate on the pro's and cons of the TMR, compared to a Master/slave dual redundant system, the redundancy level is actually the same: both can only withstand the failure of 1 main processor. The TMR has extra advantage on the ability to detect false signals, due to the deficiency of IO processing card, at the cost of extra hardware.

With the current advancement of I&C hardware, the chances for such error to occur is much more slimmer, if compared to the era of Mark IV and V (with all those flying wires and ribbon cables, and open PCB to allow dust accumulation).

If you ask me to choose, I think a dual redundant is good enough. But of course if you have enough budget, TMR would be a better choice.

Why a normal PLC/PAC/DCS may not be suitable to control a gas turbine is because, unlike normal processing plant, gas turbine requires a fast speed PID regulator loop to control the fuel valves. Normal PLC and DCS are preinstalled with lower speed PID control blocks.

I have heard ITS from Austria has managed to use the S7 hardware to come out with their own software suitable to control GE gas turbine. They have claimed they can convert the control sequence from old GE system to their system. So the control and protection philosophies are 100% compatible. If I am not mistaken the product is called MACH 7. Also rumors has been they have designed their own firmware so now the S7 can be customized to work like GE TMR.

I agree to CSA that, when we look for choices on the market, not only we should be concerned on the hardware features, but we should also query the vendor whether the control philosophies are the right one for our gas turbines.

We just can't use the Siemen's way to control a GE gas turbine.

All the best.

Kelvin
 
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Bob Peterson

I can't imagine that any PLC made in the last decade would not have a PID loop capable of controlling any mechanical valve fast enough. Mechanical valves move pretty darn slow.

There may well be other issues that make a PLC a poor choice for regulating GT, but it seems unlikely that speed is one of them these days.
 
Hi Bob,

With the power of microprocessor nowadays, I don't think it can't do what Mark IV/V can.

PLC is a too general term. If we look at it as a microcomputer, that can communicate with all kinds of IO processing modules, and be programmed to execute any kinds of sequencing software you want, then what is the difference between a Mark Vie and a PLC? They are pretty close.

But normal PLC/DCS, let say one that you bought as a selected model from the catalogue, would only be fitted with software and IO modules suitable for certain applications specified by OEM.

More specific example is if you have purchased PCS7 (a DCS), the software package comes with a library of objects (blocks of software modules) that you can customize for your application. But those are mainly for process plants, not for power generation. If you need it for Power gen, they will sell you the SPPA-R3000. Because only that has the IO modules and software for you. But the core hardware and firmware are very similar to PCS7.

So the point is not whether it is a PLC or DCS or TC. The most important point we need to understand is whether the controller can interface with all the instruments and actuators we need, and execute the sequencing programs exactly the way compatible to the specific GT.

Most users, as far as I know, when selecting options for upgrade, only look at the hardware specs, or brands. They don't know how to dig in further.

We are not merely selecting Apple or Samsung.

Kelvin
 
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