Very interesting topic..

I have got many points from experience you shared. We do have suffered that problem twice on our machine.and alarm turbine shaft failed to break away was also received. Controlman and Salman points are exactly that were faced

Once it was due to Generator lift oil discharge pressure low, and second time it was due to Lube oil console level low switch in actuated state. in both cases Machine will not come on Turning Gear.

Thanks

 

Dear all

We have experienced the same problem with G.E ms9001 E (frame 9) turbine where the problem once was due to the starting means filter restricting pressure build up for the torque converter. the other was the generator jacking oil filters found dirty. again restricting sufficient pressure for jacking the the generator bearing 1 and 2.

It is also advised to test the lube oil for its viscosity.

we once tried to increase the angle of torque converter motor to 75% just to provide initial torque manually as the turbine turned bought the control of 88 tm back to auto position.

Best Regards
suhail

 

This thread was very helpful as i am currently encountering this issue

@CSA, I appreciate you greatly. can i have your email please?
Thank you.

 

I am currently experiencing this in my plant. it is a GE Frame 9E turbine. The unit was on grid and there was system disturbance which made it to trip. It was unable to attain the cooldown mode. Efforts to put it on cooldown proved abortive as the alarm; starting means device failed to breakaway L45CR_Alm. At first, we thought it was the jacking oil pump 88QB but it wasn't. Meanwhile the wheelspace temperature is about 55deg.
Right now, we are suspecting the torque converter,which is at 67.9deg opening.

What must have been the cause of this failure to breakaway that is inhibiting the cooldown mode operation please?

 

No.

 

Based on the (minimal) information provided, it's impossible to make even an educated guess about what the cause might have need. The previous replies to this thread and many other similar threads on control.com contain a lot of possible causes, but because you have chosen not to share any specific information about the turbine (type of cooldown mechanism (slowroll; turning gear; ratchet; etc.)) or tell us how long the unit was at zero speed before you could try to put it on cooldown there's really no way to answer your question.

Lastly, contrary to wildly popular and false belief every GE-design Frame 9E heavy duty gas turbine is not identical to every other GE-design Frame 9E heavy duty gas turbine. Many different packages, auxiliaries and combustion systems have been supplied over the decades the machines have been produced.

 

We are using 6 Units Frame 9E gas turbines and we often have the problem with failure to break away.

Up to now, most of the time, we have experienced problem with starting means filter blockage. Now we started to replace the filter after each outage as a preventive measure, the problem rarely happens.
Other than the starting means filter, we experienced the problem with Torque converter, which is not giving sufficient torque to break away with the reference angle from the controller. The main MCC of the torque converter have option to raise the angle manually, we could solve the problem adjusting manually to get rid of shaft failure to break way issue.

There were some coinsurance, we have changed total torque converter, due to malfunctioning of the equipment.

Only one or two times in the entire history, we had problem with 20TU solenoid, which dumps the oil from torque converter. The solenoid is provided with a limit switch also.

As you mentioned, you have pressure measurement on the torque converter inlet, it will definitely help you to find out where the problem lies. If everything in torque converter is clear, then we need to suspect the jacking oil pressure. I believe, there is are pressure switches installed to tell the system if jacking oil pressure is low for both the generator bearings. (L63QBL in our case) Or, as by measuring the lift by Bentley probe or by fixing a dial gauge. If the lift is less, the relief valve in the system can be adjusted to make it okay. However, this will be done with help of mechanical, who tells you how much lift is required on each bearings.

Hi boos
we have 2 like this turbine model and the we are facing like this problem .my question is if the pressure inside the torque converter is 17 bar is that possibles we check or replace the filter?

 

Who had faced this problem and what is the solution ,please?

 

We faced a similar issue on our frame 9E gas turbine as the original poster. My question here is: how can we
differentiate whether the issue lies with the torque converter, or if there was actual mechanical rubbing in the turbine that was preventing the rotor from rotating. We are suspecting that due to low temperatures in the turbine compartment and high rotor temperature, there was rubbing inside the compressor which was preventing the rotor from rotating. How can we, now that the turbine is in operation, conduct a root cause analysis and what parameters should we focus on that would differentiate between these two things?

For further reference, there was no issue with the starting motor. We verified torque converter pressure which was normal at 16 bar. The torque converter filter was also working fine, and we conducted a lift check which was fine as well. When we started the turbine, we preloaded it with our manual turning mechanism at the load coupling and startup happened as normal.

 

@mechengg,

It's very difficult to make a root cause analysis now that the machine is running.

If the machine had been shut down and put on cooldown (slowroll or hydraulic ratchet--we don't know because we don't know the cooldown mechanism on your machine) There should have been no problem with restarting the machine.

If the machine WAS NOT on cooldown within about 20-30 minutes of reaching cooldown "speed" and the axial compressor rotor was hot AND the air temperature in the turbine compartment was cool/cold then it's a very good possibility that there was a rub. The ONLY way to tell for sure would be to inspect the axial compressor blade tips AND the axial compressor casing to see if there was any rubbing.

There's a LOT we don't know about the full details of the specific situation you are referring--or the auxiliary equipment of the machine. The general rule is: If the machine is tripped or shut down from a hot, loaded condition and either can't go on cooldown (slowroll or ratchet) or can maintain cooldown operation for 12-24 hours--WAIT. Keep the Aux. L.O. Pump running to keep the cooling flow of lube oil to the bearings (all of them--not just the compressor and turbine) and WAIT until the highest wheelspace temperature of the machine is below 100 deg F. DO NOT try to force the machine to rotate using jacking and manual turning mechanisms--it's entirely possible (and HAS HAPPENED many times) that trying external means to rotate the rotor can cause serious damage to the compressor if it has bowed or sagged and one or more compressor blades are in contact with the axial compressor casing. VERY EXPENSIVE damage that can take weeks or months to repair, and then there's the lost revenue from power generation in addition to the cost of repair.

After the axial compressor rotor has cooled even if it has sagged or bowed the metal throughbolts of the compressor assembly will start to return to their normal lengths. The won't go to back to exactly equal BUT by using cooldown and some FIREd operation to gently warm the axial compressor rotor at low speeds any lingering effect of the sagging or bowing will be removed and the vibration levels during acceleration to rated speed will most likely be below alarm levels and will smooth over time.

In such a case where the machine couldn't go on cooldown or couldn't maintain cooldown for the proper length of time it's REALLY IMPORTANT NOT TO OPEN THE TURBINE COMPARTMENT DOORS OR MANUALLY OPERATE THE TURBINE COMPARTMENT VENT FANS. As you noted, if the axial compressor casing cools quicker than the axial compressor rotor the chances of a rub (resulting in an inability to rotate the machine with the ratchet mechanism or the torque converter) are much higher and trying to "force" the machine to turn with external methods could be disastrous.

AGAIN, you didn't provide a LOT of important details so we can't say anything more than this. And, trying to develop a definitive correlation between temperature differentials at the time of the incident now that machine is running is nearly impossible unless you have some really good archived operating data from the incident, and even then, a definitive cause and effect can't be properly determined.

Waiting about 24 hours after a machine can't be put on cooldown when it's hot is MUCH LESS COSTLY than trying to force it to turn when the likelihood of a compressor rub is high. If the axial compressor rotor bows or sags when it's hot, the metal is just in it's elastic range--not it's plastic range, and the likelihood of permanent damage by waiting approximately 24 hours means the throughbolts will eventually return to a near normal condition (again because the metal temperature is in the elastic--not plastic--temperature range).

 

In our case, the machine underwent a normal shutdown and was put on turning gear as per procedure for at least 24 hrs. For reference, we do not have a hydraulic rachet and our turning gear does not operate on a clutch. We were carrying out offline washing during which the machine was cranked up to 800 rpm to inject water and detergent and was brought to zero-speed again for soaking. Everything was normal up to this point and the issue started when we attempted to start the machine to 800 rpm for the rinse cycle.

We carried out all checks as mentioned in my last comment. At this point wheelspace temps were in the range of 30 - 40 C (ambient temps were around 30 degrees) and compartment temps were around 30 degrees. Just like most people on this thread, we attempted to rotate the turbine manually through a hydraulic jack during which we heard an abnormal sound which seemed to originate from the compressor, and when we inspected the first stage blades from the IGV compartment we observed rubbing marks. We turned the rotor intermittently for a few hrs until clearance was achieved, and just like many other commenters on this thread, we applied force on the rotor through a manual jack and gave the start command, after which turning gear was engaged successfully.

It's unclear why this happened after the turbine had undergone a completely normal shutdown and only faced this issue during offline washing.

 

@mechengg,

Yes; it's unclear. EITHER there was some kind of rub/interference in the axial compressor section (the longest and heaviest part of the machine's rotor) OR there was some kind of issue with the Voith torque converter and/or solenoid (20TU-1). It's doubtful you will know what the problem was unless it occurs again--which is what you're probably trying to avoid.

You initially wrote in your first post: "... We are suspecting that due to low temperatures in the turbine compartment and high rotor temperature, there was rubbing inside the compressor which was preventing the rotor from rotating...." If the machine was shut down normally and went on cooldown ("turning gear") for about 24 hours before the off-line water wash was initiated then there should NOT have been a high temperature differential between the axial compressor casing and the axial compressor rotor. (The turbine section of the machine's shaft is very short compared to the axial compressor section and doesn't usually experience rubs.)

We still don't know how old/young the machine at your installation is, what kind of generator it has (hydrogen-cooled or air-cooled) and precisely what kind of "turning gear" mechanism you are referring to. I am only familiar with cooldown systems on GE-design Frame 9E machines that use the torque converter to turn the turbine rotor at around 50 RPM during cooldown (the starting means would have a 20TU-2 solenoid for this) OR machines that use a hydraulic ratchet mechanism to periodically turn the machine rotor during cooldown (usually used only with air-cooled generators which have a much heavier and longer generator rotor). The air-cooled generator rotors often have some kind of "lift oil" or "jacking oil" system to help get the generator up off the bearings during starting--and maybe there was some kind of issue with that system and was preventing the starting means from breaking the shaft away from zero speed when trying to re-start the machine after the detergent soak.

Without seeing photos of the damage you say you observed of the first-stage axial compressor blades we can't see what you saw. And, because that end of the axial compressor rotor is VERY near the #1 bearing the likelihood of it rubbing. Where did the rub marks you observed appear--on the tips of the blades or ???

You're not giving us much to work with, and your intentions are good--but since the machine was re-started and is running now there's not much anyone can do unless the problem occurs again. If you have archived data from some kind of "historian" feature you can look at the wheelspace temperatures and see what they were at the time the off-line water wash was started and that would give you some kind of idea of what the internal machine temperatures were--though not precisely in the axial compressor area where rubs would most generally occur. MOST (but not all) machines have a strong "draft" (air flow) through the IGVs and the axial compressor and the combustion section and the turbine section and the exhaust and exhaust stack (and any "boiler" which the machine might be exhausting into). It's this draft (air flow) that would do most of the cooling of the machine and the axial compressor DURING cooldown.

Those are about the most likely causes for an inability to start the machine after the detergent soak based on the most recent information provided. And, still--without more information you are going to have a difficult time saying with any degree of certainty precisely what the problem was. We don't know if the machine shaft turned using the hydraulic jack on the first attempt or the fourth attempt. We don't know how old the machine is, or when the torque converter was last refurbished (if ever).

And this IS a controls-related form--and you are asking a question that is primarily mechanical in nature. We have provided the most likely possible causes for a machine we don't have a lot of information about. (Contrary to false popular belief EVERY GE-design heavy duty gas turbine--even Frame 9E machines--are NOT exactly alike, especially the auxiliary equipment systems provided with the machines (such as the starting means, cooldown method, and generator type.) And unless there was a problem with the system solenoids, the torque converter guide vane actuator/motor starter, or the lift oil/jacking oil pumps or lift oil/jacking oil pressure/flow control there's not a lot of other controls issues. We don't know what alarms were annunciated when the machine couldn't be rotated. We don't know what Diagnostic Alarms (we presume the machine has a digitial GE turbine control system) were annunciated when the machine couldn't be rotated (you know--the alarms everyone ignores). But, this is most likely NOT a controls-related issue and without a lot more information and some actionable data (graphs; photos; etc.) there's not a lot more we can offer.