Mark V questions

J

Thread Starter

JiM

Heyas!

Long time reader, first time poster here. First off, just wanted to say what a great site this is! This website has helped me a great deal in regards to my job.

That being said, I have a few (probably simple for most of you) questions regarding the Mark V turbine control from an operations stand point. I'm an operator at a 550MW Combined Cycle facility out here in CA. 2-7FA's (DLN 2.5 w/ MK V) and a D-11 steamer. Before I ask, I will say that we have recently lost a good GE CPM as well as some very good operations guys that were very good at troubleshooting and had a great understanding of the Mark V's,etc.. due to plant political issues. That being said, we as an operations team are lacking as far as troubleshooting and even some of us the basic understanding of things like the Turbine control system.

So, my question is in regard to TTRF and the modes of Operation during, let's say, a start up. Is TTRF temp. the determining factor in when the turbine switches modes? Like at some TTRF setpoint the turbine will switch modes? some of the guys here think it is the MW's and determine the Modes. for example one might say, " The turbine goes into mode 6Q at 75-80 MW".

Any input would greatly be appreciated. I have scoured through our GE manuals as well as searches on here but I can't get clarification. Oh and please keep it simplistic for this humble operator so he can understand LOL : )
 
Hello!

Yes; TTRF (Turbine Temperature-Reference, Firing) is a calculated value which is compared to various setpoints to determine when to change combustion modes. These temperatures occur at roughly identical loads, hence the 75-80 MW range you referred to. If combustion mode switching happened based on load, it would happen at the same load every time, not in some range.

There is usually some "deadband" in the switch setpoints, to prevent toggling during some loading/unloading conditions. For example, lets' say the first combustion mode change occurs at 1700 deg F during loading. During unloading the change back might occur at 1650 deg F, for a 50 deg F deadband, instead of at 1700 deg F.

But, you have the basics correct. TTRF (or TTRF1 at some sites) is used to determine when to change combustion modes on GE-design heavy duty gas turbines equipped with DLN combustion systems.
 
CSA,

Thank you so much for reply this helps! : )

So with what you stated regarding TTRF, if a Unit is in 6Q and in Baseload operation, I'm assuming that it has reached some predetermined setpoint from which what I read in another post here on Control.com is the setpoint where GE deems the gas turbine is most efficient and with the least wear and tear on parts. Is this correct? If so what determines this baseload TTRF setpoint? Is it a calculation of several different inputs? I'm looking at our gas turbines now in baseload and the TTRF temps are different.....how come? Thanks again for your time : )
 
JiM,

The setpoints are Control Constant values, in other word they are "fixed" they are not calculated like TTRF is. TTRF is calculated from a number of parameters, including axial compressor inlet temperature, compressor discharge pressure, I believe ambient (barometric) pressure is also used, etc.

Because every machine--even ones built "side by side" and installed and commissioned "side by side"--is different, calculated values will not be identical. There are many factors which contribute to efficient operation and the values of measured parameters.

6Q is the mode in which the emissions are lowest and the combustor dynamics are optimum. Base Load is where the unit is operating at its most optimum point--optimal parts life, optimal power output. Base Load is a constant "firing temperature"--which is a different value altogether from TTRF which is a calculated value. The firing temperature of a 7FA turbine is the temperature of the combustion gases leaving the first stage turbine nozzle. A constant firing temperature means the thermal stresses on the turbine nozzles and buckets are nil, at a minimum. This is where GE-design heavy duty gas turbines would love to be "parked" (continuously operated) because it's the best for parts life--all of the hot gas path parts--in terms of minimal thermal stresses. It's the starting and stopping--including tripping--that reduce parts life and decrease the time between maintenance outages, which is when money is being spent and no power (and steam) is being generated!

I don't have access to a Mark V CSP right now or I'd look up the names of the combustion mode change setpoints. I'll try to find one soon and respond with the Control Constant names so you can look them up for your units.
 
J
Jim,

Just wanted to let you know of an alternative support opportunity for you from GE called Controls Connect.

The site was established to help users find information quickly. Plus the Technical Support Team is available 24/7 and consists of experienced engineers. CSA does a great job on this forum and I am not trying to minimize his input but GE Controls Connect is just another option available for you.

I am the Product Line Leader at GE Measurement and Controls. GE has launched a new Controls Connect portal that has significant functionality to help answer your questions. In Controls Connect you can search the knowledge database for similar issues plus find manuals, GEHs, GEKs, TILs, white papers, etc or phone/email the technical support team directly. GE provides a level of complimentary phone and email support for controls customers. This is a FREE service. I hope it helps.

CONTROLS CONNECT NOTE: If you have a GE Single Sign-on Number (SSO) and are a GE turbine operator, business associate or EPC firm, please send me an email with the subject "Controls Connect Access" and include your SSO#, Name and Company. Note that we do not accept generic email addresses (e.g. @yahoo, @hotmail, @gmail, etc). Company based email addresses are required for security reasons. Your registration will take approximately 3-5 days.

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