Today is...
Wednesday, April 25, 2018
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
A demonstration of EtherCAT control of linear motors using the CTC EtherCAT master.
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Starting means turbine shaft fail to break turbine away
When we try to put the machine to turning we get the following trip "Starting means turbine shaft fail to break turbine away"
2 out of 2 members thought this post was helpful...

On 31st August we shutdown the plant because of a planned outage of Gas for 4 days. Gas Turbine was given a shutdown command and was then put to cool down mode normally. Turbine was kept on turning (100~112 RPM) till the morning of September 3. At that time, wheelspace temperatures were well before 100C.

On September 3, we planned to do the offline washing and for that we had to put the turbine to 0 speed. The offline washing command was given but starting motor did not take the command. All the permissives were checked but starting motor did not take any command.
Again cool down sequence was selected and instead of washing, we tried to put the turbine on turning again.

Now here are the findings. Test gauge was installed on torque converter and its pressure is normal (16 bar). A jaw type fixture was installed on turbine coupling in aux compartment and turbine was tried to rotate with hydraulic jack and it was turning normally. Again starting command was given to motor and it was not able to break the torque.

Turbine was then put to turning but giving the starting command by apply the force with hydraulic jack at the same time. Turbine was kept at turning for 6 hours and was stopped again and tried to put on turning again without jack but again same alarm appeared that turbine shaft failed to break away.

Now the problem is, starting command is given, Starting motor run for 50 seconds and turbine shaft failed to break away. We have checked different possible things but did not find any problem. Can you please guide what should we check?

I have all the details and we have checked different things. Its just I am not sure what details to be posted at the moment. Please let me know if you need another detail to troubleshoot the problem.

2 out of 2 members thought this post was helpful...

This problem haunted me for quite some time long time ago. Thank god it was solved then ;)

I was trying to understand your problem but I'm not sure whether the starting motor did turn on during your attempts. Some of the things to check as follows:

(i) If the starting motor did not run when start command is given, check the start check permissive on your HMI (I assume). If all start check permissive is met, check the electrical supply to the motor. Ensure that the 6.6kV (I assume) breaker is turned on and the motor protection panel is also energized.

(ii) If the starting motor did run when the start command is given, check the torque adjuster motor breaker at MCC. Ensure that the breaker is in not overload. Reset the breaker and try to operate the motor manually. Put the selector to HAND and push RAISE/ LOWER to see whether the motor operates. If the motor did not operate, check the control circuit and torque converter actuator motor. You informed that the pressure gauge at the torque converter did register 16 bars. Does the pressure raise gradually to 16 bars after start command is given or does it go to 16 bars at instant?

So many things could go wrong and cause a unit to fail to break away. However if no work was carried out to the unit before the failure and the unit never had any problems previously to breakaway, my only assumption would be the breaker for the torque adjuster motor ;)

Check those things up and if possible check the calibration of limit switches at the torque converter actuator. Good luck!!

Hello,

Thank you for replying. You asked to check two things.

1- If the starting Motor is running?
Yes it is as we can see starting motor going to its rated RPM and its current variation accordingly. In-fact the trip we are getting is "Starting means turbine shaft fail to break turbine away" which only appears if starting motor is running for 50 seconds and no RPMs are detected for Turbine.

2- If the motor for torque convert angle adjustment is working.
We have tried to put the torque convertor on manual and have operated that motor. It is working fine and the fact that starting motor amperes change based on the angle shows that the vanes angles are actually changing.

3- The pressure stays 0 for first 5 seconds when the starting motor amperes are maximum and then the pressure gradually moves from 0 to around 19 bars. At this point we put the torque convertor angle to auto and it angle changes from 16 to 66 degrees. At that point the pressure drops from 19 bars to 16 bars and stays there until the starting motor trips.

Another thing is that when we use the hydraulic jack at coupling to break the starting torque, and then give the starting command, it is able to take the turbine to 110 RPMs and then at turning, turning motor amperes are normal and this torque convertor pressure is around 7 bars.

Please let me know if any other information is required.

Hi,

May I know if the torque converter uses solenoid valves. What is your turbine model and the control system it operated on?

Yes our torque convertor uses SOV to actuate dump valves. However there seems to be no issues with it as the pressure at test gauge point of torque convertor is 16 - 19 bars depending on the torque convertor angle.

Our turbine is GE Frame 9171 E (Non DLN) with Mark VI as its control system.

Please let me know if you have any other question?

I am making some assumptions since I have not seen your turbine. I will assume you are using a Voith torque converter for starting and break away means. I do not know how many hours and starts are on your machine but it does sound like a possible problem with the ratchet assembly. I would be verifying correct hydraulic system pressure. Verify that that the torque converter fill valve and lube oil supply pressures are normal. Monitor the status of the ratchet pressure switches in MKVI logic. This will indicate if the ratchet stroke is happening. If the ratchet stroke is happening but there is no movement of the shaft then I would suspect a failure of the ratchet clutch assembly.

Hello,
Thanks for your reply.

Our Gas turbine uses Voith torque converter and the Gas Turbine is around 2 years old. Total running hours are around 13,000.

Can you please tell which ratchet assembly you are referring to?
The Lube Oil pressure of the system is normal and also the pressure at torque convertor test gauge moves up to 19 bar as starting motor reaches 3000 RPM and decreases to 16 bar as the torque convertor reaches its maximum value.

Also can you explain this point? "Monitor the status of the ratchet pressure switches in MKVI logic"?? Where are these switches? What is their Tag etc?

I am still not sure what is a ratchet pressure? If you can explain it a bit, I would monitor it and would let you know about it.

Umar,

I would suggest monitoring the status of ratchet pressure switch L63HR2F which should be the ratchet forward stroke pressure switch, and L63HRF1 which should be the return stroke pressure switch. Also monitor L20HRX which is the command to the ratchet stroke solenoid valve.

Trend all these signals while attempting to start the unit. You should see L20HRX go true which indicates the unit is calling for a ratchet stroke. Monitor the state of L20HRF1 and L20HRF2. They should change state as the ratchet system strokes forward to rotate the shaft, and then change again as the ratchet returns to its at rest state. If all this appears to work correctly then I would suspect a problem in the mechanical portion of the torque converter ratchet system.

Please refer to your device summary for the location of these pressure switches and solenoids. The switches are mounted on the torque converter hydraulic cylinders. These switches have been known to fail and could be the problem for the failure to break away.

I've checked the Device Summary, P&ID of Starting Means and the GT Logic (m6b) for these signals and devices and have found no trace of either the SOV (L20HRX) or the pressure switches (L63HRF1 & L63HRF2).
Our turbine is GE 917E NDLN Dual Fuel (Diesel and LOW BTU Gas). The torque converter installed is of VOITH with a drain valve at bottom and a motorized link on the top to change the torque converter angle.

Umar/MIKEVI,

First of all, this topic was covered in a previous thread (use the control.com 'Search' feature)--very nearly identical. The original poster (and apparently his company) did not want to believe that the torque converter was the problem, but it was ultimately found to have been incorrectly rebuilt, if I recall correctly, causing it to not transmit sufficient torque.

MIKEVI, the addition of a ratchet to Frame 7Es/EAs and Frame 9Es is something of a recent development and began with the switch from hydrogen-cooled generators to air-cooled generators. The air-cooled generator rotors required much more torque to break them away from zero speed, and so was one of two reasons to add hydraulic ratchets to the units.

The second reason was also related to the air-cooled generators, though it was primarily the tilting pad bearings used in the air-cooled generators (the hydrogen-cooled generators used journal bearings). Prior to switch to air-cooled generators a method called "slow-rool" Cooldown was used to keep the shaft spinning at approximately 30-50 RPM by forcing some Aux. L.O. Pump discharge pressure/flow through the torque converter--sort of a "turning gear" but without the gear. But the additional force required because of tilting pad bearings was too much for the slow-roll method, and so this was the second reason the hydraulic ratchet was added.

So, while the 7EAs at your site may have hydraulic ratchets all similar Frame 7E/EAs and Frame 9Es do not have hydraulic ratchets.

Umar, torque converters do wear out over time. It's also entirely possible that the torque adjustor mechanism limit switches may require adjustment. And, as was the case in the similar thread even if the torque converter was recently rebuilt it may not have been done properly.

Have you tried using the manual handwheel on the torque converter to open the torque converter fully (past the purge or accelerate torque limit switch setting)? You will have to depress the handle on the side of the torque adjustor mechanism to engage the handwheel and then turn it in the OPEN direction (marked on the handle)? You can do this immediately prior to starting the turbine.

But, again, torque converters do wear out, and torque adjustor limit switch settings do change over time. Has anyone tried "adjusting" them recently.?.?.?

Hello CSA, Thank you very much for a useful post.

Our Gas Turbine is almost new as the running hours are around 12000 hours. There has been no maintenance/inspection on torque since commissioning.

We overruled the Torque Converter problem by following facts.

1- When turbine is rolled with the help of manual jacking, the starting motor is able to role the turbine as initial torque was broken by manual jack. Now when the starting motor cut out and turning motor engages, it roll the turbine at around 120 RPM. At this rpm, the torque converter angle is 44 degrees which was the case before too.

2- As the starting motor starts and increase its RPM to 3000, the pressure at the test gauge point of torque converter reaches upto 19 bars and then drops to 16 bars as the torque converter angle increases.

3- We usually start the turbine with torque converter angle at 16 degree and after the current on starting motor is normalized (after 15 seconds) we put the torque converter angle on auto and it increases up to 66 degrees. However in one of the start we tried to start the turbine with torque converter angle at 44 degree. In that particular start, instead of starting motor tripping on above alarm, it tripped with indication of motor overload. This means that the angle link system is working fine.

4- We have tested and tried to change the angle from local as well. It is working fine and with changing angle on local, its indication change on MCC also.

5- In one of the start, when the torque converter angle reaches up to 66 degree on auto, we put it on manual and took it up to 74 degrees but no gain.

6- Since we have to put unit back into service, instead of using GE arrangement of jacking, we made our own jacking arrangement in a way that which can break the initial torque and at the same time it can be removed during first 2-3 revolutions of turbine. We were able to do so and after keeping the machine on turning for 6 hours, we moved on to the firing of Gas Turbine. Gas Turbine went to cranking speed, stayed there for 15 minutes during purge cycle, came back to firing speed, fired successfully and starting motor took the machine up to 60% RPM successfully. Now during all this torque converter was functional and we did not see any of the abnormal behavior by torque converter.

Now does torque converter required maximum torque from 0 to 2 RPM?

Please let me know if I can provide any other details to have this issue solved.

CSA/UMAR,

CSA, thanks again for the education, always more to see and learn out there, especially in this business.

UMAR, sorry for sending you the incorrect formation. Thankfully there are others out there like CSA to help teach us both! I hope that when the turbine is down again you will have more time to diagnose your problem and report your findings back here.

Hey MIKEVI,

What other findings should I take? We have taken a lot of observations and those might not be here yet. May be you can share more of your thoughts and I will see if I have answers those or not. If not I would try to take those observations the next time unit is down.

Thanks for the reply.

Looks like something is not working properly in your torque converter. Please ask the OEM to give it a check to confirm.

Was the torque adjuster actuator limit switches checked for calibration? If those switches are fine, then it might be the torque converter being the culprit as you able to breakaway the turbine with assistance from the hydraulic jacks.

What was the starting motor current when you tried your tests?

We have come across a same problem in same unit (GE9171, Mark VI) after 14,000 running hrs. Does anybody get a answer?

Torque converters do wear out and do require refurbishment. If the site uses the cranking motor for forced cooldown and/or off-line water washing this, too, can accelerate the wear in the torque converter.

Also, it's common for the Torque Adjustor Drive mechanism limit switches to require adjustment and/or replacement. I presume the starting means at your site uses a 3-phase fractional horsepower with a brake mechanism to open and close the variable torque adjustor guide vanes. I am also presuming the unit does not have a Hydraulic Ratchet mechanism for cooldown operation.

Usually, the Torque Adjustor guide vanes are opened and closed by pulsing the Torque Adjustor Drive motor contactors (one for Open and one for Close) with relay outputs from the Speedtronic. The Torque Adjustor Drive mechanism has adjustable limit switches which are used to set the ends of travel for Min Torque and Max Torque, and sometimes for "Purge" torque (usually slightly below Max Torque). So, the Speedtronic relay outputs and the Torque Adjustor Drive mechanism limit switches are connected to the motor starter control circuit. There are also over-torque limit switches in the Torque Adjustor Drive mechanism to protect the mechanism from being driven into mechanical stops which would damage the mechanism.

You should be sure the Speedtronic relay output to Open (RAISE) the torque output of the torque converter is actually driving the Torque Adjustor Drive mechanism to the Max Torque position. The turbine should be at zero speed; it's not necessary to have the Aux. L.O. Pump running for the test. Force the Torque Adjustor Drive mechanism RAISE relay output to a logic "1" (usually signal name L4TMR) while someone is observing the motor starter to see it be energized in the RAISE condition and that the pointer on the Torque Adjustor Mechanism moves to the OPEN position. (It may not go all the way to the fully open position, as the setpoint of the switch may stop it from going fully open.) Force the RAISE logic signal to "0" and then force the LOWER logic (usually L4TML) to "1" and the MCC observer should see the starter energized in the LOWER direction, and the person at the Torque Adjustor Drive mechanism should see the indicator moving towards the closed position (it may not go all the way to the closed position because the limit switch setpoint may not allow it to go fully closed). This would prove the Torque Adjustor Drive mechanism is working properly. (Unforce all logic signals at this point.)

If the Torque Adjustor Drive mechanism is opening (RAISEing) and closing (LOWERing) the variable torque converter guide vanes, then it's most likely a worn torque converter OR the limit switch for the Max Torque (and/or Purge Torque, if so equipped) may need to be adjusted. Before making any adjustments, do the following test. The turbine should be at zero speed; it's not necessary to have the Aux. L.O. Pump running for the test. Force the RAISE logic (L4TMR) to "1"; the Torque Adjustor mechanism will go to the Max (or Purge) Torque position. Leave the logic signal forced to "1". Push down on the handle on the Torque Adjustor mechanism (to engage the Manual Handwheel) and turn the Torque Adjustor Mechanism Manual Handwheel in the OPEN direction (the direction arrow is cast into the handweel) approximately 1 full turn. DO NOT TURN the handwheel if it has encountered a mechanical stop! The handwheel should turn relatively easily; you must hold the handle down while turning the handwheel, and it may take a half-turn of the handwheel for the mechanism to engage for the indicator to start moving in the open direction, so you may have to turn the handwheel more than one turn to get a full turn with the manual mechanism engaged.

At this point, leave the Torque Adjustor mechanism in this position. Leave the RAISE logic signal forced to "1". Put the turbine in CRANK mode and inititate a START. The cranking motor should start and after a short time delay the shaft should start turning. This would indicate the Torque Adjustor mechanism Max. Torque limit switch (and the Purge Torque limit switch, if so equipped) need to be adjusted because of wear in the torque converter. This also means the torque converter is going to need to be refurbished soon.

Once the shaft starts turning and the unit gets above approximately 10% speed (300 RPM), unforce the torque converter raise logic.

Again, if the above tests prove the Torque Adjustor Drive Mechanism and its motor starter circuit are working properly by the relay outputs from the Speedtronic, and if the shaft breaks away from zero speed by increasing the opening of the variable torque converter guide vanes then it's a pretty safe bet the torque converter needs to be refurbished.

All of the above presumes the turbine-generator shaft bearings are in good condition, the unit did not suffer a trip from load while the rotor was hot and failed to go on cooldown for the appropriate amount of time, the turbine bearing L.O. header pressure is as it should be, the strainer of the Torque Converter is working as it should be, the Torque Converter fill/drain solenoid 20TU-1 is working correctly, and the valves in the oil supply to the torque converter are in the proper positions. (Refer to the Starting Means P&ID.)

There have been several related threads on control.com, even one in which a recently refurbished torque converter was not properly refurbished (or the Torque Adjustor mechanism limit switches were not properly adjusted after the refurbished torque converter was installed). But, a failure to break the shaft away from zero speed usually means a worn torque converter or improperly adjusted Torque Adjustor mechanism limit switches.

If the unit has a hydraulic ratchet mechanism, that means the torque converter requires a "bump" from the hydraulic ratchet mechanism to help break the shaft away from zero speed. So, if the unit at your site has a hydraulic ratchet mechanism you will have to be sure the hydraulic ratchet mechanism is working properly to help break the shaft away from zero speed.

Please write back to let us know what you find and how you proceed.

1 out of 1 members thought this post was helpful...

Umar and KP,

Is there in your gas turbine what we call lift oil pumps for generator shaft (88QB)? and Bently Nevada Proximity detectors on generator shaft?

If yes, maybe the lift oil pressure is not enought to lift the generator shaft, and by experience (in our 9E gas turbine) this is due to flexible(s) feeding the bearings or pads with about 240 bars and witch can present a leakage.

If yes, you can read the Bently Nevada proximity detectors values; In our case the variation between when 88QB is stopped and when it's runing is about 0.2 to 0.3 mils.

Be sure that 88QA is also runing.

I wish this helps

Regards

Controman makes an excellent point!

Be sure to check the lift or "jacking" oil pump flow, if your machine uses it. And the best way to do this is with the B-N proximity probes if they're installed.

This kind of information--about your machine and its configuration is very important to provide in your post. While every Frame 9E sucks and squeezes and burns and blows, the auxiliaries and the generator can be very different and yet still produce the same amount of power. So, the more you tell us about your machine--and what you've done to try to troubleshoot the problem and the results of your troubleshooting--the better and faster and more concise the response will be.

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.

By tony salman on 20 April, 2013 - 8:30 am

Dear All

i read all experience share that is good notes. but i think the problem get from lube oil tank level switch. because in logic the level switch cutting three signal first, one turning gear, second crank motor, third lifting pump. may be the level reach critical level and when the turning gear stopped the level is ok . when start again the level reach low. please check the indicator and switch level and check the feedback of crank motor 52cr, may be have lose in wire or breaker problem. good luck

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.

No.

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?

1 out of 2 members thought this post was helpful...

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.