In Mark VI control system during startup sequence of gas turbine after auxiliaries ready to start (L3ARS) control system check the status of "CORE ENGINE". Same thing is checked by the system after auxiliaries ready to fire (L3ARF). Please explain what is core engine.

 

The only time I've every heard of "core engine" is when the Mark VI was used in a unique aero-derivative control system called the "Millennium" control system. I believe the core fuel control functions (probably including speed control and load control and start-up/shutdown fuel control and some protective functions (overspeed?)) were accomplished with a "smaller" Mark VI processor, and all of the "basic" auxiliary sequencing (pumps, fans, solenoids, motor starters, etc.) was done using a PLC, and the two communicated using EGD and MODBUS (yes, MODBUS).

From the signal name descriptions, this sounds like an aero-deriviative turbine with some kind of Mark VI-based control system similar to the one described above. My presumption is that the two control systems (the Mark VI and the PLC) are possibly monitoring or "checking" each other to be sure they are healthy and communicating with each other before continuing with the current process or moving to the next state/mode. But, that's just a SWAG on my part; I've been fortunate enough never to have to work on one of these Mark VI/PLC systems.

I believe there was a manual produced by the GE Aero systems group (based in Houston, TX) on the Millennium control system. There is probably more and better information in that document, which should be in the manuals provided with the unit.

 

Strangely we have exactly the same wording in a Start organogram for our Frame 6 generators from GE (Nuovo Pignone) (and I've never understood it either)
In order we have

Auxiliaries Permissive OK?
Yes (L3ARS=1)
Core Engine and Diagnostics OK
Yes
Master Selector
Not "OFF"
Unit Ready to Start
L3RS=1

If I check the logic for L3RS, I see nothing that could even relate to core engine or diagnostics to give a L3RS permissive

Is this a Nuovo Pignone or Alstom supplied package?

Our GE guys are still on site, I'll go ask them what they mean by it and see if I can get any answers

I agree, "core engine" usually refers to aero-derivative machines

 

This is a frame V GE gas turbine and MArk VI checks core engine status at two points

1. After Auxiliaries ready to start L3ARS
2. After Auxiliaries ready to fire L3ARF

I just what to know what are the checks that control system does during "Core Engine test"

 

There was some sequencing/application code logic that ran in some early digital Speedtronic systems that performed some communication/health checks between processors and between processors and the protective processors. Those communication/health checks been replaced of late by some operating system code that runs "in the background" and if there are problems, there will be Diagnostic Alarms (yes, cryptic Diagnostic Alarms) to alert a conscious operator or technician to the condition, likely in addition to some LEDs that are lit or have changed from green to red or amber.

It's been said before on control.com:<pre>
<b>The only sequence that matters is the one running in the controller.</b></pre>
What does that mean? It means, no matter what document you read about how the turbine and control system operates <b>the turbine at your site</b> the only document that matters is the one derived from the sequencing (or in the case of Mark VI, application code) running in the control processor.

Whenever you read documents about GE control system and turbine operation--even ones produced by GE--you should read them for <b>INTENT</b>, <b><i>not</b></i> content.

What does that mean? It means when you read documentation (flow charts, organograms (never heard that one before!), paragraphs, sentences, etc.) that you interpret that to mean that's the way the sequencing/application code was written to operate the unit <b>at the time the document was written.</b> There are many iterations and changes made to sequencing/application code over the years, and most of the changes never get documented. In GE Energy, the last thing that's done in producing a system or unit is the documentation. And once it's written, it's rarely--if ever--modified to incorporate any updates or changes.

It means that if you interpret written documentation to mean the turbine or control system <b>especially for a unit that has been running for some time with no problems</b> should be running differently because of what you read, you're likely to be mistaken (wrong). The people who review and write the sequencing/application code for a particular turbine application have no obligation or responsibility or deliverable (corporate-speak) to review and update any corresponding documentation.

So, the problem you are describing is one that appears to be one of trying to reconcile some written document with the application code that's running in the processors(s). <b>What's running in the processor(s) wins.</b> Every time. Right or wrong. What's running in the processor(s) "over-rides" whatever's written in some description or flow-chart or manual.

Period.

End of discussion.

 

Dear CSA

Thanks for the reply