good evening everyone here ...

I want to ask bout the margin of FSR warm up for liquid and gas from what to where? the safe values and how much can effect the turbine if I exceed these values? what is the effects? ....

as i Know its 12 for warm up in liquid and 9 for the gas for frame 9E turbine ....

Thanks

 

Ahmed,

First, not all units have the same settings; fuels and control valves and fuel nozzles can vary a lot between sites and machines.

One can't just say, "There is a range of +/-3%" for warm-up FSR. One has to look at all the knock-on effects.

Second, if the warm-up FSR is too high, the unit may accelerate too quickly which may cause a flame-out when warm-up is complete and the unit goes on Acceleration control. If warm-up FSR is too low, there is a chance the unit may lose flame in one or more combustors, and trip on loss of flame.

Third, for Frame 9E's it can be quite a balancing act to keep flame on in all the combustors while not accelerating the unit too quickly resulting in a loss of flame trip when the control transitions to Acceleration Control and the acceleration rate is so high FSR is driven to FSRMIN waiting for the acceleration rate to decrease.

If FSRMIN is set too low the unit can lose flame in one or more combustors and trip on loss of flame.

It's a very delicate balancing act, which sometimes requires an adjustment to the pulsing of the torque adjustor drive motor to help limit acceleration while on warm-up FSR and keep warm-up FSR high enough to prevent loss of flame trips while on warm-up FSR. It might take an adjustment of FSRSU_WU(_LIQ, _GAS), FSRMIN components, and torque adjustor pulse rates to achieve optimal starting reliability without excessive spreads or high temperatures or loss of flame trips.

There is no "range", other than what's required to maintain flame in all the combustors while not accelerating the unit too quickly during warm-up, and then hopefully FSRMIN isn't set too low after warm-up is complete if the acceleration is a little fast.

One has to watch TNHA and TNHAR and FSR and monitor the spreads and flame detectors during firing and warm-up and during the transition from warm-up to Acceleration Control to do the appropriate amount of tuning.

And, as was said above, sometimes it's even necessary to slow down the pulsing of the torque adjustor drive motor during warm-up to reduce the acceleration rate while FSR is being held at warm-up value.

If you tell us about the problem you are having, and can provide some data (TNHA, THNAR, TNH, FSR, TTXSP1, -2 and -3) perhaps we can help.

If this problem just started happening, after a maintenance outage, please describe what was done to the unit during the maintenance outage--including any LVDT calibrations. If the fuel supplier has changed, and/or the fuel make-up has changed, tell us about that, too.

Hope this helps!

 

thanks a lot for your very helpful information and your quick response. actually its my fist thread in this wonderful site.

the problem in began suddenly after a normal shutdown and the GT is still very new its still in RTR. its the same thread that you discussed before about the flame out problem. I am the client, and its not like the end of the thread ("he found the problem" MOE changed the FSR from 12 to 10)

I saw the GT before and yesterday also in starting up it was like the following

firing FSR =23, after the flame was detected the FSR changed to 13.8 which is the same amount of the FSRMIN and the GT began after 60 sec of warming up to accelerate from 13.8 base. i noticed that FSRWU=FSRMIN, and when the starting motor loosen the GT the following alarm comes up "acceleration to low to startup ".

I where there in the commissioning phase the FSR was right just like the control specification 12.. till it changed to FSRMIN...

and thanks again for you help

 

Ahmed,

It sounds like there may be more than one Control Constant that needs tweaking.

I will say this much: A decrease from 23 to 13 from firing to warm-up is high. Either there's too much fuel during firing (which may be the case), or there's not enough fuel during warm-up. And, if when the unit is going to warm-up it's being limited by FSRMIN, then it sounds like the FSRMIN constants need some adjusting, too.

In any case, I suggest you trend TTXM during firing, note how quickly flame is established when the fuel stop valve opens, and then how high exhaust temp spikes. If you get flame VERY quickly, it's likely the exhaust temp will be increasing faster than it should be, and then when FSR gets cut back to warm-up/minimum then I suspect the exhaust temperature spreads will start increasing even though the exhaust temperature will start increasing so quickly. And this is when flame-outs can occur. This is a sure sign of too much fuel during firing, and too little fuel during warm-up.

If the warm-up value of FSR is too high, though, then acceleration may be too fast (TNHA is much greater than TNHAAR when warm-up is finished) and then the fuel might get cut back to minimum which would make things even worse. If the spreads are already high and FSR gets cut back even more when it should be increasing to assist with acceleration, then flame-outs can occur at this time as well.

And, also, when the torque converter is being pulsed to maximum after flame is detected during warm-up if the pulses are too quick (too long in duration, or too little time between pulses) then this can also cause the acceleration rate to be excessive.

I'm presuming the unit has a Voith torque converter with an variable torque adjustor mechanism; if there is some other kind of starting means then I'm not familiar with it or how it works.

So, it's a very delicate balancing act--something which <b>must</b> be tuned during commissioning. The Control Specification is <b>NOT</b> gospel when it comes to starting, acceleration, and even shutdown FSRs. Remember: Firing FSR and Warm-up FSR are OPEN LOOP. They're just values--and they usually need to be adjusted. The basis for tuning is a reliable start without loss of flame, without excessive exhaust temperature spikes, and without high spreads and flickering flame indications, and without excessive acceleration during warm-up. The Control Specification is a starting point, and only that. Firing- and Warm-up FSR are estimations based on expected fuel characteristics and design parameters, some of which can, and usually do, change from the time the unit is ordered until it is commissioned causing tuning to be required.

And, I'm primarily referring to natural gas fuel above. Worse, if the unit also starts and runs on liquid fuel the flow divider feedback scaling has been known to be wrong VERY often, and that can cause a lot of tuning to be necessary for liquid fuel starting.

Again, the Control Specification is <b>NOT</b> gospel when it comes to starting and acceleration, and shutdown. It's a guide and a starting point, especially for starting and shutdown, but it's almost never 100% correct--especially for liquid fuel.

Please write back to let us know how this progresses.

 

We have 9E DLN1.0 equipped units and Firing and Warmup FSR values for Liquid and Gas is as below

On Liquid Fuel Firing FSR is 29% and Warm-up FSR is 14%
On Gas Fuel Firing FSR is 1.9% and Warm-up FSR is 0.8%

Hope this will also helpfull to you, as this is first article replied by me

 

sb,

I have three questions and a request.

First, what is the gas fuel P2 pressure during Firing (the pressure <b>down</b>stream of the Stop-Ratio Valve)?

Second, what is the P2 pressure at 100% speed?

Third, what is Firing Speed (Control Constant value TNK14HM1) at your site?

Last, please provide the values of the two Control Constants, FPKGNG and FPKGNO.

Thank you for the information!

 

Dear Sir

Sorry for delay in response, I am glad to communicate with you.

Please check the parameters and constants value

FKPGNG= 3.3291 PSI
FPKGNO= 375.464177754493 psi
TNK14HM1= 10%
Firing speed for fuel gas is 12% and for fuel oil is 16%
P2 I don't remember exactly but it remains like 22~23bar

 

sb

The <b>ONLY</b> formula for P2 pressure reference I have ever seen is:

(TNH * FPKGNG) + FPKGNO

At 10% TNH, that would translate to a reference of:

(10 * 3.3291) + 375.464 = 33.291 + 375.464 = 408.755 PSI

<b>THAT'S OUTRAGEOUS</b> especially for a DLN unit<b>!!!!!!!!!!!!</b>

That explains the ridiculously low Firing FSR on gas fuel.

Something is very, Very, VERY. <b>VERY</b> wrong--OR the machine has EXTREMELY unusual control schemes and/or Control Constants.

 

Dear Sb

If you've study and have seen algorithms to G.R Valve, they scored (FPKGNG, FPKGNO) GAIN and OFFSET. They define the output pressure of the G.R Valve during at different speeds in startup times. Units of measurement are V DC and V/%N not psi.

Every chat with friends on this site, is required to send the correct information. Otherwise unfeasible conclusion the no.

good luck

 

Dear mohamad noruzi,

Yes; I was remiss not to have included the units for the gain and offset. For all later Mark IV panels (not the early Mark IV panels), all Mark V, Mark VI, and Mark VIe panels the units would be PSIG/%TNH and PSIG, respectively. (Mark VI and Mark VIe are not <b>usually</b> configured with Metric units in Toolbox or ToolboxST.)

Early Mark IV and prior control systems used VDC/%TNH and VDC, respectively, where 5.00 VDC was equal to the upper calibration value of 96FG-2A (usually 200.00 PSIG, or higher depending on Frame size and gas fuel supply conditions).

Based on the values supplied by sb (which were also unitless), V/% and V would not have worked properly. And, the Speedtronic panel in use at his site would most likely be a Mark IV at a minimum, and one if the later models with engineering units instead of VDC.

Finally, all Speedtronic panels are <b>NOT</b> configured identically, just as all Frame 9Es (or Frame 5s, or Frame 6Bs, etc) are not identical. Yes they all suck, squeeze, burn and blow--but the components, auxiliaries and packaging can be VERY different. As can be the programming of the turbine control system.

Sorry for any confusion.

 

Dear CSA

Go through the following figures

FPKGNG 3.3291 psi/% REAL Fuel Gas Pressure Ratio Control Gain
FPKGNO_GLT375.464177754493 psi REAL Gas Leak Test SRV Drive Open Constant
GT firing spee 12% on Fuel Gas
Firing FSR=1.8% VSR= 8.9% P1= 27.1 bar P2= 6.5 bar and Warm up FSR=0.8%
TNK14HM1 10 % REAL HP SPEED LEVEL DETECT 14HM PICKUP SETPOINT
In earlier topic I missed to say that P2=22.6 bar is at FSNL

Hope this will clarify, any other parameters you need, plz tell me, I will check and observe further

Thx

 

P2 at firing 2.5 bar at fire and after fire warmup and accelerate noted 6.5, Or this time at startup I will check.

 

SB,

As was said earlier in this post, one needs to be more precise when posting--not just with Engineering Units for REAL values, but also for Control Constant names.

 

CSA,

Does the self sustaining speed of a turbine = starting means top speed.

Is it possible to hold this speed while starting means is still engaged unit warmup temp is reached.

Not sure about restrictions on starting means time limit before cut out.

> As was said earlier in this post, one needs to be more precise when
> posting--not just with Engineering Units for REAL values, but also for Control Constant names.

 

David,

No; the self-sustaining speed of a GE-design heavy duty gas turbine does not equate to starting means top speed. In many cases the turbine is self-sustaining long before the starting means top speed is attained. In any case, it's not really about starting means speed versus turbine shaft speed--it's about the transmission of torque from the starting means to the turbine shaft, which while related to speed is not directly a function of the output speed of the starting means prime mover (electric motor or diesel engine or expander turbine) or the output shaft speed of the torque converter (most units have torque converters, but not all).

It is not possible to control the speed of a GE-design heavy duty gas turbine below 95% of rated speed with a GE Speedtronic turbine control system. GE does not want an operator to accidentally stop acceleration at a critical speed which could cause high vibration to damage the unit.

Also, the air flow through a GE-design heavy duty gas turbine is usually very low at less than rated speed (a characteristic of axial compressors). And, if you look at a plot of exhaust temperature versus speed during the acceleration of a GE-design heavy duty gas turbine you will see that the exhaust temperature increases to nearly the maximum allowable and then as speed increases further and air flow through the axial compressor increases the exhaust temperature decreases. It is not good for the turbine or exhaust components to experience high temperatures at low axial compressor flows and discharge pressures, so the GE philosophy is just not go give the operator any method for controlling speed below approximately 95% speed.

Of course, someone can always "force" things to hold fuel flow stable during acceleration--but they would be doing so at their own peril and would have to take responsibility for the consequences of the action should damage occur to the unit because of either maintaining elevated exhaust temperatures for an excessive period or high vibrations.

No; GE does not publish the critical speeds of their turbine-generators.

 

CSA, thanks for responding.

You have given me clarity to some concerns that I have had for some time.

David,

 

CSA, just thinking out loud.

When a turbine is on warmup FSR, what is its speed then?

The reasons for my questions are. As you said, its a balancing act for the transition from warmup to acceleration control.

like any mechanical device,as a unit ages, its as shipped (new)characteristics and control constants may no longer hold true, especially if they were tight to begin with.

In my thinking, of trying to get a handle on the approach of fine tuning, and troubleshooting these questions arise.

Could you lay out an approach, to resetting these constants for an aged unit, where the suspected problem is, example-flame out on transition to acceleration control.

 

> It is not possible to control the speed of a GE-design heavy duty gas turbine below 95% of rated speed with a GE
> Speedtronic turbine control system. GE does not want an operator to accidentally stop acceleration at a
> critical speed which could cause high vibration to damage the unit.

One minor clarification on this statement. The 5001M or R or whatever the current letter is for the "Mary" compressor 5001: This machine in mechanical drive applications can operate down to 80% speed. All other single shaft GE heavy duty gas turbines have the 95% minimum operating speed limit. The LP rotor on 2-shaft machines can generally be operated as low as 50% speed.

 

David,

If the turbine is experiencing loss of flame on transition from warm-up FSR to Acceleration FSR, that usually means the acceleration rate is too high. In other words TNHA is so much higher than TNHAR that FSR is driven to FSRMIN. And if FSRMIN is too low then the unit will lose flame.

For newer Speedtronic systems, FSRMIN is calculated based on speed level and some factory-"set" Control Constants, which are just approximations, at best.

The acceleration rate may be too high because of the assist from the Starting Means. Sometimes it's possible to slow down the assist through the torque converter, but usually only on units with a Torque Adjustor mechanism which is pulsed open. Most turbines don't have an adjustable torque output, unfortunately.

If a unit does not a Torque Adjustor mechanism that is pulsed open then one really only has the option of decreasing Warm-up FSR--which can also lead to loss of flame if decreased too far; and/or increasing FSRMIN in the speed range where the problem is occurring.

One should NOT change the FSRMIN speed ranges (FSRMINNs), ever, as FSRMIN is also used during fired shutdown (isn't GE wonderful?!?!). Only change the FSRMIND value for the speed range where the loss of flame is occurring during starting.

But, be aware--unfortunately, this might also negatively impact a fired shutdown in the same speed range. GE really didn't think the use of FSRMIN for both start-up and shutdown very well!

If the unit was working fine, and then it started having problems one should always consider what changed to prompt the problem. And try to address that before changing controls settings. To everyone, the Speedtronic can be tweaked to overcome any mechanical change or problem. And sometimes that's true, but often it's not and leads to even more unintended consequences. There is cause for every problem, and the Speedtronic control systems are involved the cause is quite often mistakenly blamed on the Speedtronic, and the "solution" is often mistakenly made by modifying some Speedtronic parameter(s). Don't fall into that trap!

 

David,

The turbine is NOT on speed control during firing or warm-up. So the speed is not fixed and will--and does--change while in FIRE mode.

During warm-up (and during firing) the fuel control valve is being positioned based a fixed values of FSR (FSKSU_WU and FSKSU_FI, respectively). Fuel is not being varied to maintain any speed during these two periods.

Speed changes while in FIRE mode, but not because the Speedtronic is changing the fuel flow/fuel valve position.