Hello everybody,
I was looking at the circuit diagram and am just slightly confused about the L4 signal. It would be great if anyone could help me out with finding the exact similar L4 signal in MARK VI in the attached diagram. I think 4-4 on the raw 40 in the attached document is the same signal.



thank you in advance for help

 

I wish I could give you a proper answer, but I've been studying the .pdf file and I don't really see a one-to-tone equivalent. Because I've never had the pleasure of working with a Mark* I it's not clear to me what the Master Protective philosophy was at that time. I suspect it morphed over time to what is is with the digital control systems. Remember, the Mark* I is most electromechanical relays--which have a fixed number of NO and NC contacts associated with each relay. So, it's possible that multiple relays were used and on another page of the elementary most--if not all--of the 4-n relays have NO contacts in some kind of series and/or parallel configuration for some measure of redundancy.

I would be looking at something on the fuel stop solenoid sheet (20 sheets?) to see what relay or relays actually allow the fuel stop solenoid valve to be energized and result in de-energization of the fuel stop solenoid valve for a trip or a normal shutdown.

Sorry; without being to see the entire elementary I just don't know what else to recommend. Please let us know what you find out!!!

 

Hello everybody,
I was looking at the circuit diagram and am just slightly confused about the L4 signal. It would be great if anyone could help me out with finding the exact similar L4 signal in MARK VI in the attached diagram. I think 4-4 on the raw 40 in the attached document is the same signal.



thank you in advance for help

WTF is correct that there are many differences going from Mark I control systems to Mark VI. Mark I was the first electronic gas turbine control system for GE. The sequencing and master protective circuits were all relay logic. The speed, exhaust temperature and fuel control circuits were electronic. I don't remember just when it was first introduced; it was still being used when I started working on gas turbine controls in 1971, although Mark II was being introduced at that time. Mark II replaced most of the sequencing with solid state (discrete) logic, but retained relays for the master protection circuits. As WTF noted, electromechanical relays had a limited number of contacts on them, so multiple relays in parallel were often required to provide sufficient contacts to do the work.

Once microprocessor based controls were introduced (Mark IV was the first by GE) there was no real limit to the number of "contacts" for a signal. There were still some relays used to interface with the solenoid valves that dumped the trip oil on the turbine (125 VDC was a little too much for solid state devices). I think on the current Mark VIe, there are fewer of these type interfaces.

So, the logic "signals" in the Mark VI are generally equivalent to a relay in the Mark I and Mark II controls with the same name minus the leading "L".

Just understand that there are many differences regardless - Mark I units did not have DLN combustion systems for example, Hope this helps.

 

I wish I could give you a proper answer, but I've been studying the .pdf file and I don't really see a one-to-tone equivalent. Because I've never had the pleasure of working with a Mark* I it's not clear to me what the Master Protective philosophy was at that time. I suspect it morphed over time to what is is with the digital control systems. Remember, the Mark* I is most electromechanical relays--which have a fixed number of NO and NC contacts associated with each relay. So, it's possible that multiple relays were used and on another page of the elementary most--if not all--of the 4-n relays have NO contacts in some kind of series and/or parallel configuration for some measure of redundancy.

I would be looking at something on the fuel stop solenoid sheet (20 sheets?) to see what relay or relays actually allow the fuel stop solenoid valve to be energized and result in de-energization of the fuel stop solenoid valve for a trip or a normal shutdown.

Sorry; without being to see the entire elementary I just don't know what else to recommend. Please let us know what you find out!!!

First of all, thank you for your answer. I found that GE used 4-1 and 4-2 NO contact for 20FG (fuel gas solenoid) and used 4-3 and 4-4 NO contact for 20FL (liquid fuel). You can find it in the attachment.

Also, If you attention to the PDF file (attachment of the first post) All signals, I mean (4-1, 4-2, 4-3, and 4-4) are series (see attachment). Therefore, It can be said the coil of the relay of 4-4 signal is the same L4 in other versions of Speedtronic

 

Welcome back, @otised! Thanks for the details; very much appreciated!

 

I don't really have anything more to say on this. Unless you are trying to replace a Mark I (or Mark II) control with a microprocessor control, there isn't a whole lot to be gained by trying to make a 1 for 1 comparison between them. GE (and some competitors) have been supplying these conversions for a long time. I doubt there are many Mark I and Mark II control systems still in service and it must be difficult to get spare parts for them. By the mid to late 1980's, all new GE gas turbines had the microprocessor based controls. Note, I have been retired from GE for 14 years now, and while they are still using the Mark VIe controls, I am pretty sure there have been substantial changes to the control algorithms used over that time-span. I know they were looking into model-base controls, although I don't know if they have used them.

 

@otised,

I was thinking the same thing--this seems like a question about configuring a different control system to replace a Mark* I.

As for Mark* VIe, I think the biggest change has been the way that programming is being done--FBDs, Function Block Diagrams, and other methods for displaying the control scheme. They seem to be moving away from "old school" RLD (Relay Ladder Diagram display). I worked on a very early Mark* VIe upgrade to later technology Mark* VIe and they mixed three different types of application code display methods in ToolboxST and THAT was confusing (as well as having several serious flaws in basic protection logic). AND, it had an entirely new HMI network, using thin-clients and running a UNIX-based OS on the main server and each thin client was running virtual MS-Windows machines. And, of course, NO documentation on any of it. They had to have a person from the utility's IT department come to site to re-start thin clients when there was a problem (and there were many problems).

Of course, there are any number of programming and program display methods which can be used with just about any type of digital, programmable control systems being used to control any process. Beginning with Mark* IV, GE pretty much stayed with RLD format using algorithmic blocks with graphical representation of the inner workings of the block in a RLD-like method) for controls. It made working on Mark* turbine control systems easier for a few decades.

But, Jack Welch's legacy continues to live on: "If it ain't broke, break it," and, "The only constant is change." I, for one, believe that something that has worked extremely well for decades doesn't need to be replaced simply because it's "old" or "old school." I remember (as I'm sure you do) working on Mark* II control systems (pre-ITC), going from RLD to whatever that was called and then going back to RLD with the next-generation Mark* IV (and Mark* V and Mark* VI and Mark VIe). Anyway, I'm happy to be retired and while I miss many of the people I used to work with, I don't miss the politics and chaos of the organization. It has such potential, but until they properly integrate all the different groups into a single cohesive and Customer-facing focus it's going to continue to slowly (sometimes even rapidly) degenerate.

Thanks again for your inputs not just to this thread, but the many others you have contributed to.

 

I don't really have anything more to say on this. Unless you are trying to replace a Mark I (or Mark II) control with a microprocessor control, there isn't a whole lot to be gained by trying to make a 1 for 1 comparison between them. GE (and some competitors) have been supplying these conversions for a long time. I doubt there are many Mark I and Mark II control systems still in service and it must be difficult to get spare parts for them. By the mid to late 1980's, all new GE gas turbines had the microprocessor based controls. Note, I have been retired from GE for 14 years now, and while they are still using the Mark VIe controls, I am pretty sure there have been substantial changes to the control algorithms used over that time-span. I know they were looking into model-base controls, although I don't know if they have used them.

Thank you for your answer. but, as I wrote in the last post I just found my answer and shared it with you.
I mean this:

Also, If you attention to the PDF file (attachment of the first post) All signals, I mean (4-1, 4-2, 4-3, and 4-4) are series (see attachment). Therefore, It can be said the coil of the relay of 4-4 signal is the same L4 in other versions of Speedtronic

thank you again for your guidance.