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MARK II to MARK VI Upgrade: Queries
Some queries about exhaust T/C interface for MARK VI upgrades...
By Rahul P Sharma on 9 June, 2006 - 1:09 am
1 out of 1 members thought this post was helpful...

We have two GTs Viz. GT-1 and GT-2 controlled by SpeedTronic MK II Control System...

In the Exhaust Temp Zone we have 18 Exhaust Thermocouples (XD1 to XD12 for Control Purpose; XDT1 to XDT 6 for Overtemp protection Alarm and Trip Purpose)...

In MARK V (used for our GT-3) we have only 13 Thermocouples for the control as well as protection functionality...

We are in process of finalising the upgradation of MK II System to MK VI system...

The Query:
Can the existing 18 Thermocouples of MK II system (GT-1 & 2) be interfaced with MK VI system or will it need to be changed too?? (The MK V system which we have for GT-3 has very different kind of Exhaust T/Cs not at all resembling those of GT-1 and GT-2!!! Is it right to presume that MK VI will also come with similar T/Cs as used with MK V system??)...

au revoir

Hello sir,

Can u send me Mark V Manual PDF File?
I want to learn it.

thanks & regards,

C&I Engineer

By Bambang Rukamdo on 20 August, 2006 - 5:36 pm

Hi Roma ?
did you got the manual already ?.
if not which manual you want?. it is a big file.


Bambang Rukamdo

By Paras Parmar on 10 June, 2006 - 11:41 pm

Mark-V & VI is able to take any kind of thermocouple (configuration to be done).

Mark-V & VI uses all 18 thermocouples for control and protection purpose both. No need to take separate set of thermocouples for diff. purposes.

Paras Parmar
Field Design Cell
Control Systems & Instrumentation
Reliance Refinery, Jamnagar

The choice to use 12-, 13-, or 18 exhaust T/Cs is not a function of which turbine control system is used--it's a function of the control and protection scheme used in the turbine control system. Basically, the Mk VI can be configured to use any number of T/Cs deemed appropriate by the control system engineer assigned to the job.

This is a very interesting and difficult topic to respond to. Within GE you will find much discussion about this very topic. The short answer is: You need to be proactive in the discussions with GE and ask what your options are and express your desires.

Depending on the sales person you are dealing with and his/her familiarity with the offerings, you may have an easy time of it--or, more likely, you will encounter long delays while your questions are shuffled from one person to another and you may never actually know what you're getting until the work actually begins, or, the project will take a very long time to finalize if you want all the details settled before you sign the contract.


By Rahul P Sharma on 16 June, 2006 - 8:49 pm
1 out of 1 members thought this post was helpful...

Our dilemma is that Exhaust T/Cs in our older machines are physically and looks-wise, so entirely different from the "slim n slender" T/Cs used in MK V controlled Machine... If during upgradation the older T/Cs are to be retained there wouldnt be much of a mechanical job in the Exhaust Plenum side... But it seems, that the chassis might have to be changed (not sure on this one...!!) if new kind of exhaust T/Cs are to be incorporated (cos the new ones wud be different in shape)... The older T/Cs were screwed into the circular periphery of the exhaust frame and those T/Cs are about 1/2" in dia and about two feet in length... Now if they are to be replaced by the T/Cs akin to the ones in MK V machine (or some other newer kind), wud it not require new chassis arrangement too, to house the newer kind T/Cs..??

au revoir

This question is best answered by your GE Mk VI salesperson, but...again...

The Mk VI doesn't care what kind of exhaust T/C is connected to it--new, old, slim, skinny, fat, long, short, thick, thin, silver, black, grey, green, red, white--it's not important!!!!!!!!!!

The number of exhaust T/Cs--that's a function of the control scheme implemented by the requisition engineer configuring the Mk VI.

It's up to YOU as the CUSTOMER to ask what is being supplied or to specify what you want. Just be prepared for the worst--waiting for the responses. You may be pleasantly surprised, or you may be sorely disappointed. (Any guesses where this author's money would be bet?)

But it's still up to you as the CUSTOMER to be proactive (take charge) and ask questions and/or specify what you want.

The new aeroderivative-style T/Cs are real time-savers (and time IS money--anywhere in the world!), but they would require new radiation shields and a new wiring harness, but the time-savings over the years would likely be more than worth the expense.

New "chassis"--no. (Though, after a couple of decades, is the original one still in serviceable shape--and for how much longer? Braden Manufacturing (one of GEs vendors) is supplying new turbine enclosures and exhaust- and inlet ducts for pretty reasonable prices;


Are you sure that the number of exhaust T/Cs are up to the customer? The turbine control system does not require a minimum number of exhaust T/Cs? Is the instrumentation of the turbine totally left to the customer requirements and control system engineer commissioning the turbine, or there are minimum requirements for the Mark V to function?

I am just curious to know if it is possible to cancel out any feedback signal?

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

Nothing was said about leaving the number of exhaust T/Cs up to the Customer; if GE is providing the control system they will choose the number of exhaust T/Cs for the Customer. They feel as the OEM/designer they have the authority to set the number of exhaust T/Cs that will be used/required for protection of "their" unit.

The Customer can work with the control system supplier to improve the exhaust temperature monitoring and protection (usually be increasing the number and/or placement of exhaust T/Cs), but it's probably certain than any control system supplier would attempt to persuade any Customer not to decrease the number of exhaust T/Cs used for protection.

It should be noted that the number--and placement--of exhaust T/Cs on older machines (prior to the Mark IV's production days, early 1980s) was not always symmetrical around the unit. Because older control systems were analog systems and didn't have the horsepower and inputs there were quite "irregularly" placed (non-symmetrical) T/Cs, some used strictly for protection (exhaust overtemperature) and others used for control (compressor discharge pressure-biased exhaust temperature control). And, there were several methods of spread detection that included both control- and protection T/Cs, or only protection T/Cs, or only control T/Cs.

So, GE--when analyzing an older unit being upgraded to a newer digital control system--will look at the number and placement of exhaust T/Cs to ensure that combustion monitoring, in particular, is uniform and not subject to irregular placements which could negatively impact spread detection and monitoring. (Though it does seem that some units "slip through the cracks" (gaping holes in oversight and supervision and documentation) and it's only discovered years later when nuisance spread problems lead to a detailed analysis of T/C placement and usage.)

It's not just the number of exhaust T/Cs--it's the number and placement of exhaust T/Cs that determines how many will be used on a turbine control retrofit/upgradation project.

Hope this helps!

By Amar DAMENE on 2 January, 2017 - 12:55 pm


For us, we just upgraded Mark II to Mark VI. Our GT are GE Frame 3.

About Your Query:

Yes your existing 18 Thermocouples of MK II system (GT-1 & 2)
can be interfaced with MK VI system.

You can keep the model of thermocouples, and it is possible to change them by a another model; let's talk with the contractor......

Au revoir et au plaisir de vous aider (


Nb: Let me know others customers who need help about Speedtronic Mark II; Mark V

Hello Rahul P Sharma!

do you have MARK II manual?

I'm trying to model the control system but i've not found a complete block diagram. Maybe inside manual i can find the model with its parameters, inputs and outputs.
the machine is old and uses a MARK II as speed governor generator.

thank you very much.