HMI selectors identification

A

Thread Starter

Amr Karam24

Dear CSA,
I need your experience to identify some selectors on the HMI,
And how it will take the GT in starting.

(1) select "SC fire" NOT SC or CC.

(2) select "pre-start" to be master control.

(3) select "fast load" to be master control.

My GT is 9Fa, MK VIe, DLN 2.6+
 
Amr Karam24,

Hello, again.

1) You probably already know this, but SC likely stands for 'Simple Cycle', and CC likely stands for Combined Cycle. When turbines are equipped with this there is usually a diverter damper and bypass stack and HRSG (Heat Recovery Steam Generator ("boiler")) on the gas turbine exhaust and the turbine can be operated in either simple cycle (GT exhaust directed to bypass stack) or combined cycle mode (GE exhaust directed to HRSG).

When being started in SC mode, the greatest effect on start-up is that the purge time is usually much shorter than when being started in CC mode (because the HRSG and exhaust stack has a very large volume to be purged, and the bypass stack is usually a much smaller volume that doesn't require as long to purge).

Other than that, I don't understand the question.

2) I've never encountered "pre-start"; as I said the GE 'Belfort Bunch' do some really kinky things--unnecessarily complicated and virtually inexplicable things that only they can "explain" (and sometimes, they can't even explain it!).

If I had to hazard a guess, "pre-start" might mean a START and automatic synchronization and loading to the current value of Pre-Selected Load--but that's <b>JUST</b> a SWAG (Scientific Wild-Arsed Guess). And with anything that comes out of Belfort, <b>France</b>, it may, or may not, be correct.

3) A Fast Load START is one that sometimes has a fast acceleration rate (from firing to FSNL (Full Speed-No Load)), but once the unit reaches FSNL it automatically synchronizes the unit (usually without the operator having to select AUTO SYNCH!) and then very quickly loads the unit to either Pre-Selected Load or Base Load. The acceleration- and loading rates are usually very fast--so fast that these starts have special "factors" associated with them that greatly impact maintenance outage planning (because the fast rates are very hard on the hot gas path components because of the high thermal stresses that are experienced in a very short period of time during a Fast Load START).

Hope this helps!
 
A
Dear CSA,

I compeletly agree with you that GE "Belfort Bunch" do some really kinky things and sometimes they can't even explain it. And that's why i asked your help.

And about my first question "SC fire" here you are. On my HMI there's a selector named "SC fire" as "SC" selector and"CC" selector. So when i select the selector named "SC fire" and start the GT, what will happen?

I hope that my question became clear.

Thank you again for your NONSTOP help.
 
Amr Karam24,

Without being able to review the application code running in the Mark VIe of the turbine at your site it's virtually impossible to say for sure what that 'target' (what you're calling a 'selector') does.

Most targets on the Start-up display are grouped together. There's the 'Master Select' group (sometimes called the 'Mode Select' group); the 'Fuel Select' group, the 'Load Select' group, the 'Governor Mode' group, etc. Which group is this 'SC fire' target in?

Have you asked GE?

Have you looked in the Control Specification drawing provided with the unit?

Usually when some unusual function like this is provided it is in response to some requirement by the plant designer or owner for some desired operational capability. Most combined cycle power plants these days are provided with a set of manuals put together by the plant designer to describe how the plant was intended to be operated ('intended' because quite frequently some of these designs don't work very well when put into service and so there is some modification and retrenchment--which unfortunately usually doesn't incorporated into the plant operation manuals...).

So, if you can't get an answer from GE then you're going to have to look elsewhere--the application code, and/or the plant operation manuals provided by the plant designer/EPC firm.

Lastly, it's not uncommon for some targets on GE-design heavy duty gas turbine displays to not work--sometimes because they weren't configured properly, and sometimes they just weren't removed because that functionality wasn't provided with the turbine.

Wish I could have been more help, but dealing with the Belfort Bunch is difficult at best when one can have a face-to-face discussion. It's virtually impossible to try to guess what they're doing, especially when their description (translated from French to English) is cryptic (and no one, even in Belfort, has the secret decoder ring!).
 
IF SC means Simple Cycle and CC means Combined Cycle, then:
The main difference is the control curve for the inlet guide vanes. In simple cycle, the IGV's go to full open at a relatively low exhaust temperature. In combined cycle they are kept at a minimum operating angle (usually 54 to 57 degrees) until the unit nears base load condition. They will get to the full open position (usually 84 degrees) just before base load is reached. This keeps the exhaust temperature higher, which improves the steam cycle performance.

Typically, you would only use the SC Fire if you were going to run in simple cycle mode, either using dampers to port the exhaust gas to a bypass stack, or sometimes there are less convenient methods like blanking plates when the only reason for simple cycle operation is to be able to run the gas turbine while maintenance is being performed on the HRSG.
 
otised,

I agree with everything you said--<b><i>except</i></b> this unit is a DLN unit. The IGVs operate very differently on DLN units--even when in simple cycle versus combined cycle mode.

And DLN 2.n units don't usually have the selection for IGV Exhaust Temperature Control, or even IBH ON/OFF that some DLN-I units have, either. (In fact the IBH control valves fail open on DLN 2.x units, while they fail closed on DLN-I units. And IBH does interact with the IGVs.)

This appears to be something the GE Belfort dreamed up and apparently haven't provided much explanation for or detail about. The most likely place for any "explanation" would be the Control Specification, and possibly some notes in the application code running in the Mark VIe. Or, in the manuals provided by the plant designer/EPC.
 
A
Thank you both CSA, otised.

I'll try to contact GE belfort and have more information about this.
And i'll publish it as soon as i can.

Regards,
Amr Karam24
 
CSA,

Point taken, IGV's do operate differently on DLN units than what I stated. All of my experience on DLN units has been with combined cycle units that really had no capability to operate in simple cycle mode.
 
Top