Dear all.
In our frame 6 manuals the TTXSPL equation was ( 0.145 ttxc - 0.08 ctda + 30 ).
But when i calculate the according to the live value from hmi the resault was not compatible the ttxspl live value.
Is there any mistake in the equation ?
Thanks

 

enigmad,

Most importantly, why do you think the value of TTXSPL on the display of a running Frame 6 GE-design heavy duty gas turbine appears to be incorrect? Is it "too high" or "too low"? What is the value of TTXSPL when the machine is running stably at a constant speed and load for approximately four or five minutes?

1) Does the machine have a conventional diffusion flame combustion system or does it have a DLN-I or DLN-1+ convention system?

2) Give some data from a condition where the machine is running at rated speed:
TTXC
CTDA
TTXSPL
CSGV
TNH or TNH1
DWATT (if the machine is a generator drive)
FSR

3) What fuel is the machine burning?

4) If the machine IS NOT driving a generator, what is it driving (a pump or centrifugal compressor)? If the machine IS driving a generator, what kind of grid/electrical distribution system is the machine synchronized to--and is the grid/system frequency stable when TTXSPL seems to be incorrect?

5) When you say "the frame 6 manuals" SPECIFICALLY what document are you getting this information from? (What is the title of the document, or what is the GE publication number (like GEH-nnnnnnx, GER-nnnnnx, or GET-nnnnnx, or similar designation beginning with GE followed by a one- or two-alpha character designation then a series of numerical digits or numerals then possibly a single alpha character)?

6) Have you used the Dynamic Rung Display or some similar display function for looking at the CSP (Control Sequence Program) to see PRECISELY how the Mark* V AT YOUR SITE calculates TTXSPL? Because many times the ACTUAL CSP is very different from any written description, especially in some GE publication. The best written document for a particular CSP at a specific site is the Control Specification-System Settings document, though even that document is wrong sometimes. It's ALWAYS BEST to look at the running CSP (the relay ladder logic and Big Blocks) to determine exactly how some control or protection function is being calculated or performed rather than trying to understand from some written document as many times written GE documents WERE NOT updated when new control schemes or methods were introduced or modified. Unless you wrote the document you are referring to or you personally know the person who wrote the document you are referring to, it's always best to refer to the site-specific CSP (for a unit equipped with a Mark* V turbine control system) to determine how some value is actually be calculated or determined by the CSP running in the Mark* V at the site.

Sorry; I wish it weren't true--but, sadly, written descriptions of control or protection functions often are not updated or accurate.

TTXSPL is usually a value that is dynamic--meaning that any time a load change is made (either by an operator or some automatic control function, either from some external load control source or sometimes from Pre-Selected Load Control) the value will jump to some number like 300 deg F and then when the load change is complete the value of TTXSPL will begin to ramp down to some number between 35 deg F and 120 deg F and remain there until another load change occurs. So, it can seem to be very misleading--especially if you're not using the proper calculation method that is actually being used in the CSP in the Mark* V. (The Allowable Exhaust Temperature Spread Limit, TTXSPL, is "bumped up" (increased) during a load change, and then ramps back down over time to a more realistic value presuming the Mark* V inputs are valid and working correctly). This is because during a load change the fuel flow-rate, and possibly the IGV angle, changes which makes calculating an exact TTXSPL value difficult. After the load change is complete, the calculated value of TTXSPL then is ramped back down to a more normal operating value, until the next load change. If the machine is a generator drive running in Droop Speed Control mode AND the grid/electrical distribution system the machine is synchronized to is experiencing frequency fluctuations AND the machine is being operated using Pre-Selected Load Control then things can get all disturbed and confused/confusing.)