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Control System Retrofit
Retrofitting/upgrading MARK IV control system with Siemens to gain MARK VIe benefits

Our GE gas turbine is working by MARK IV control system. We are planning to upgrade the control system by replacing MARK IV with Siemens control system to gain Mark VIe benefits.

What is your solutions for doing that? is it logical? which part of control system should be modified?

1 out of 1 members thought this post was helpful...

Anna Kendrick (or SaraAsghariii),

This is a very interesting post: Replacing a Mark IV turbine control system with a Siemens turbine control system to gain Mark VIe benefits.

If what you're looking for is state-of-the-art hardware, as well as up-to-date HMIs (operator interfaces with color graphics) you can choose from many different turbine control systems.

If you're looking for specific features of the Mark VIe turbine control system they're probably going to be very hard to obtain in a different manufacturer's turbine control system.

GE offers the Mark IV Migration which guts the existing turbine control panel and installs a Mark VIe in it's place--using specially-made terminal board bases to facilitate an easy change-out because more than 90% of the wires do not have to be determinated. This has allowed GE to reduce or eliminate loop-checks which can add weeks to a turbine control system upgrade. This solution negates the need to completely remove the Mark IV and replace it with another control panel, which will require determination of all the wires in the existing turbine control panel and re-termination of the wires in the new turbine control panel, along with loop-checks to ensure all devices are properly terminated.

I'm pretty confident in saying that any other turbine control system provider will most likely say that the Mark IV turbine control panel will have to be completely removed and replaced with their offering, which will require wiring and loop-checks--both of which will add greatly to the time required to complete the upgrade.

The thing you would be avoiding by going with something other than a GE offering would be their "upgraded" software. GE feels the need to force their software "improvements" and safety "enhancements" on their Customers, without any warning about what the effects will be. For example, if your unit burns natural gas GE will add gas fuel control valve leak-checking software. This software will add to the time required to reach FSNL (Full Speed-No Load) from a START. But most importantly, if the gas fuel valves (Stop/Ratio Valve and/or Gas Control Valve) have any leaks at will--which many older valves usually have some leaks--the START will fail and the unit will be unable to be started.

That's just ONE of MANY "enhancements" and "improvements" GE will give you with their new software. And, they WILL NOT tell you about a single one of them. Many will not be known until they cause a trip or failure to start weeks or months after commissioning is completed. The Mark VIe gets a bad reputation for this--but it's NOT the Mark VIe. It's that GE doesn't tell Customers what they will be getting with their new turbine control system hardware and HMIs.

Most other turbine control system providers are going to take the software from the Mark IV (by using the Mark IV Speedtronic elementary drawing) and duplicate that in their control system. Unless you request special software modifications you won't be getting any unknown software additions. The algorithms used for things like Droop Speed Control and exhaust temperature control will probably change, but hopefully not noticeably to your operators. GE won't do that--duplicate what you have in your existing turbine control system. They have to make it better, even if that results in unknown changes to your operations and potential problems with starting and running reliability because of older field devices which may (will likely) need some refurbishment or repairs. The Mark IV works just fine with that hardware with the existing control logic and sequencing. If you added the new GE software to the Mark IV it would also start "having problems"--not because of the Mark IV, but because of the new logic/sequencing in use with older field devices in need of refurbishment/repair.

The Mark VIe is a FINE turbine control system, built to control and protect turbines, as opposed to a PLC (Programmable Logic Controller) built to serve many industries but not really turbine control and protection. The Siemens turbine control offering is a STEP-7 PLC with a couple of special modules and some special software which allows the special modules to work with the PLC hardware. The software is more user-friendly that GE's CIMPLICITY (or PROFICY as they now like to call it--but a pig is still a pig no matter what you call it).

But when these "enhancements" and "improvements" are added to the Mark VIe software that's when the problems begin.

My solution would be to write in the contract to purchase a Mark VIe that GE CANNOT provide any "enhancements" or "improvements" to the logic in the Mark VIe that they do not document IN ADVANCE to you. The contract should state that the new turbine control system should operate identically like the current software in the Mark IV, because it IS possible for GE to duplicate the Mark IV software in the Mark VIe without any "enhancements" or "improvements." They will protest and say, "Functionally, it's identical!" but it won't be--unless they are contractually required to only duplicate what's in the Mark IV. If they want to add any "enhancements" or "improvements" to the software for ANY purpose, they should be contractually required to explain, in writing, what that will entail and how it will affect operation and the Customer must accept, in writing, the change(s) before they are included in the software.

If what you want is state-of-the-art hardware and modern operator interface(s) and Mark VIe benefits--get a Mark VIe. Just be aware of what "else" you will be getting and do your best to get what you want: A direct replacement for the existing logic/sequencing that doesn't change your operation OR impact turbine reliability. You can get this from several turbine control system suppliers, not just Siemens or GE. Most will use a PLC-based control system (and remember: Siemens is just that, a PLC-based control system adapted to a turbine and auxiliaries), and while that's not necessarily a bad thing, it isn't the best thing, either.

Hope this helps! Many people may think I'm being very hard on GE, but GE has brought it on themselves. They are forcing their Customers to accept what they think their Customers want--and without even being able to tell them what they will be getting. Except to say, it's the latest and greatest in turbine control and protection, and that, functionally, it's identical to what was in the Mark IV. But that's not true, and the way the "enhancements" and "improvements" will and can impact operation and reliability should be known in advance.