Starting Motor inability to break turbine away during a Compressor Off-line Water Wash.

I would like your professional opinion on this problem that we had a couple of weeks ago. We were carrying out Off-Line Compressor Water Wash, when the turbine couldn’t break away, even though the unit was in crank mode and the starting motor was running. Subsequently, several attempts to put the unit on crank mode proved futile. The torque converter guide vane angle, which was originally 68 degrees was increased, but still the starting motor was unable to break the turbine away, even though the input shaft of the torque converter was turning, the output shaft was not turning. The adjuster motor and transmitter feedback were tested and they were working okay. The fill/drain solenoid, 20TU_1 and its limit switch, 33TC_1 were both working well. It seemed as though there was no problem with the torque converter and that, it was the gas turbine shaft that had all of a sudden gained more weight and therefore, the inability of the starting motor and torque converter to turn it. This situation was resolved only after we manually turned the gas turbine shaft, with the help of a jig, two revolutions. The shaft finally broke away with the same torque converter guide vane angle of 68 degrees. Have you experienced this problem before and what is the root-cause of it?
Kwabena, I am not perfectly familiar with the 9E since I am in the USA. Does your unit have hydraulic ratchet cylinders to break the turbine from a standstill? (Normally used on air cooled generators) Or does it depend on the torque converter itself to break the shaft away from a standstill? (Normally used on H2 cooled generators with lift oil)
MIKEVI is correct--the generator rotors of air-cooled generators are VERY heavy compared to hydrogen-cooled generator rotors and an assist from a ratchet mechanism is very often necessary to break the turbine-generator shaft away from zero speed.

I have no personal experience with 9E air-cooled generators, but I have heard that some of them require lift oil (sometimes called jacking oil) during starting and low-speed operation. The bearing design and size of some of these generators is such that they need oil pressure under the rotor shaft in the bearing to lift the shaft off the bearing and make it easier to turn as well as to protect the bearing and shaft during low-speed operation (starting; acceleration; deceleration).

Kwabena, you haven't provided us with any details about the configuration of the turbine-generator and how it is controlled (type of cooldown mechanism (turning gear or hydraulic ratchet, for example), and the type of generator and whether it requires lift (jacking) oil or not. We don't know if the jacking oil system is or was working correctly at the time of this incident.

Without more information, we can't confidently say anything more.
Thank you very much for your response. Our generator is a Brush Generator and it is air-cooled by the end fans and the air is water-cooled by four radiators. Yes, the generator has a bearing lift oil pump that lifts up the generator rotor due to its weight. Our investigations so far have proven that the bearing lift oil pump works perfectly. The two pressure switches on it are giving us indication that the pressures at both the drive and non-drive ends of the generator are okay. We have even gone further to use a pressure gauge to ascertain the discharge pressure of the bearing lift oil pump.
Additionally, our gas turbine uses the cranking/starting motor and the torque converter to turn the gas turbine shaft from zero speed or turning gear. On these occasions, the bearing lift oil pump motor works okay. Yesterday, the gas turbine was started from zero speed and sent to base load and still running at base load, however, the problem is still there. Kindly assist us.
Thank you once again!
“…Yesterday, the gas turbine was started from zero speed and sent to base load and still running at base load, however, the problem is still there….”


The remaining problem at present seems to be your inability to understand why the unit would not CRANK after the water wash as the unit was apparently started without any issues yesterday—and the same procedure/auxiliaries is/are used for STARTing in AUTO or REMOTE as are used for CRANK and FIRE. We have provided all possible scenarios—except for one: a possible problem with 20TU-1 when the unit was attempting to be CRANKed after the Off-Line Water Wash. That would be the only other possible cause I could think of that would prevent the transfer of torque from the starting motor through the torque converter to the turbine-generator shaft.

What would have been a good indication that the torque converter was transmitting torque would have been to monitor the current (amperage) being drawn by the starting motor during the CRANK attempt. Usually, starting motors draw approximately 160-170% of rated current during starting from zero speed—even when the ratchet mechanism is working property, which was apparently not being monitored during the failed CRANK attempt along with the operation of 20TU-1. I am unfamiliar with 33TC-1 and it’s purpose and you didn’t say how it and 20TU-1 was tested.

Either 20TU-1 wasn’t working properly OR the ratchet mechanism wasn’t working properly OR the generator bearing lift oil system wasn’t working properly. All of these are required for the unit to break away from zero speed during STARTing and CRANKing

If the starting motor was drawing normal starting current while trying to break the shaft away from zero speed the 20TU-1 was working properly but the ratchet system was not—for some unknown reason. Unless there were Process- and/or Diagnostic Alarms that were being annunciated but not told of in the original post that indicated problems there’s nothing more we can add to your understanding of what might have caused the inability to CRANK based on the information provided.
It’s doubtful we’ll ever know what prevented breaking the turbine-generator shaft away from zero speed that day. Again, we have provided the information we can about the system as we know it. Please know that GE Belfort are proven experts at over-complicating systems that have worked well for decades, so without being able to examine the Starting Means P&ID there’s little more we can add.

One more thing. Manually turning the turbine-generator shaft as you described could have caused very serious damage to the axial compressor had there been contact between the rotating blades and the compressor casing and/or between the stationary blades and the compressor shaft or some foreign object had made its way into the compressor during washing/rinsing (for example a water wash spray nozzle had come loose and was drawn into the compressor and gotten lodged somewhere preventing rotation. Applying force to manually rotate the shaft could cause the serious damage to the compressor had something broken. I, personally, saw the effects of this very same action taken to manually rotate a shaft that was hot and had sagged resulting in contact of rotating compressor blades and compressor casing. Instead of waiting for the compressor to cool—in that case—the site management panicked and used hydraulic jacks to force the rotation which led to broken compressor blades, almost USD 1 million to repair, lost electrical power generation revenue for several months and lost revenue from steam production for that period, also. If the normal starting system can’t break the turbine-generator shaft away from zero speed then the reason needs to be understood before using other methods to force the shaft to rotate. In my personal opinion you were extremely lucky with your I’ll-advised and hasty decision to force the shaft to rotate without fully investigating the reasons why it couldn’t be rotated with the normal system method. Very lucky indeed—because a very assumption was made: that the inability to rotate was the result of some failure of a system or component and NOT something physically preventing rotation.

Blessed day.
Kwabena, thank you very much for clarifying the type of unit and auxiliaries you have. CSA has done a great job in explaining some of the possibilities that could have caused the issue. With the successful start it is impossible to say what the issue was, and you won't have a chance to investigate further until the next time the unit is offline.
Just to repeat a few things.
Sufficient torque is needed from the starting motor and torque converter to rotate the unit. Monitoring the starting motor current is the best way to determine if torque is being applied by the starting motor. If the torque converter is not filled with oil, then motor current will be very low. Secondly if the torque converter guide vanes are not positioned properly then again the starting motor current will be low, normal breakaway and high speed cranking current is ~150% of rated motor current.
Secondly the ratchet mechanism is needed to start the shaft rotating from zero speed.
I would suggest that during the next startup there are staff monitoring the starting motor current, ratchet pressure switches, and actual output shaft from the torque converter or gearbox to try and determine what part of the system might be starting to fail. The Voith torque converters have been pretty reliable in my experience. If this unit is a high starts unit the one way clutch that is part of the ratchet mechanism may be starting to fail.
For now I would say you can only make a good list of items that can be monitored during the next start to narrow down what might be contributing to the issue.
Thank you very much CSA and MIKEVI.
I believe that I have to bring some clarity on the problem. The problem has been with us for about two years now. You see, we are able to start, crank, run and operate the gas turbine successfully from zero speed or turning gear speed of 120rpm without any problem.
The problem only arises when we want to carry out an Offline compressor water wash. That is, after we have selected "Water Wash" on the Mark VI HMI screen. The cranking motor turns, but physically and on the HMI, the gas turbine shaft fails to turn. Then, the Alarm of "Turbine failure to break away" is annunciated on the HMI.
We have also checked the starting current of the cranking motor during one of the instances when the problem was occurring and it was 150% times the rated current as indicated in the GE control specification for our unit, however, we can do it again.
The limit switch, 33TC_1 is the limit switch that makes when the fill / drain solenoid picks and opens the directional control valve to allow lube oil into the torque converter. Should it fail to respond, Mark VI gives you a "torque converter trouble" alarm on the HMI.
The manual turning of the gas turbine shaft with a hydraulic jig is necessitated in order to allow us to correct the problem and run the unit or in some cases carry out the water wash, but this time around, start the crank first (in this case, L14HRZ will not be equal to zero, so it is forced to a One to deceive the control system that we are at zero speed, in order for it to allow us get the permissive carry out the water wash.
I must emphasize that the problem only occurs when we select "Water Wash". Besides, that we are okay. The unit operates well without any problem.

This is clarity that is lacking and would have been helpful in the first post.

So, what happens when a CRANK is initiated at other times when an Off-line Water Wash is not or has not been performed? Does the unit CRANK as it should? What happens when you select FIRE and initiate a START? Does the unit CRANK and perform the purge as it should?

Is this necessary to get the unit to CRANK during the initial wash of the compressor? And, also during rinsing? It's VERY hard to imagine having to do this manual rotating of the shaft for every Off-Line Water Wash cycle/operation. This is just NOT right.

Why doesn't L14HRZ go to a logic "1" during an Off-line Water Wash?

Is there something in the logic/application code that prevents the hydraulic ratchet from starting when Off-Line Water Washing is enabled?

How does the unit get put on Cooldown (turning gear) from zero speed? Is the starting motor and hydraulic ratchet necessary to break the shaft away from zero speed when initiating Cooldown from zero speed? And is there a SSS clucth that engages the turning gear motor mechanism to keep the shaft turning at 120 RPM after the starting motor is shut down?

If this is peculiar to Off-Line Washing, then it's likely that the GE Belfort crew have struck again--needlessly overcomplicating matters and missing something very important in the process. (It wouldn't be the first time, and it won't be their last, either. It's in their culture.) It would be helpful to know how "automated" the process of Off-line Water Washing is. But, this probably isn't necessary to know the exact details. If I had to hazard a guess, I'd say it's something to do with the generator bearing lift oil pump/flow not being properly established during cranking when performing an Off-Line Water Wash--but that's just a guess.

The other clue here is the reference to L14HRZ that you mentioned. Can you provide the Control Constants for L14HR (TNK14HR1 and -2, for example)?

To really answer your question definitively, though, it would be necessary to see the program running in the Mark* at your site.
Sorry for the late response. The problem with the starting motor's inability to break the turbine away reoccurred last Saturday and we were battling with it once again. This time around, the unit was not in water wash mode, but on turning gear. There was a momentarily power disruption, which resulted in the turning gear motor going off. As a consequence, the unit slow-rolled to standstill and therefore had to be put on turning gear again, with the help of the starting motor. Unfortunately, we were unable to do so, because we once again experienced the failure of the turbine to break away problem. It is important to add that our unit's starting motor and turning gear motor share the same shaft (They have a common shaft, hence you need the starting motor to break the inertia, before the turning gear motor can take over. Turning gear speed is 120rpm).
Since we couldn't put the unit on turning gear, we allowed 48hours to elapse and then attempted to put the unit on turning gear once more. The first attempt was unsuccessful, however, after the 30-minute starting motor lockout, we changed the torque converter guide vane angle from 68 degrees to 72 degrees and this time, the attempt was successful. We also measured the starting motor's current for the first and second attempts and they were 120A and 125A respectively.

As for the L14HRZ signal, it is one of the permissive signals for starting the offline compressor water wash. This is because the unit must be at standstill (zero speed) before you can carry out an offline compressor water wash. That is why when were crank the unit before selecting water wash, we force the signal from a Zero to a One, in order to deceive Mark VI that we are at zero speed, so that it allows us to carry out the water wash.

I would also like to quickly add that, our unit doesn't have an SSS Clutch.

The bearing lift oil pump pressure has been checked again for both the drive end and the non-drive end of the generator and it was 1750psi, which I believe is very good.

During our last inspection, which was in 2016, the OEM for the Torque Converter came over to our site to work on the torque converter. He basically replaced the bearings and serviced the torque converter. I would like to know if it was necessary to re-commission the starting means system after that work? I mean, was there the need to re-adjust the settings for the torque converter limit switches?

Lastly, we have also observed that the auxiliary lube oil pump's header pressure is between 4 Bar and 4.4 Bar, but used to be between 5 Bar and 5.5 Bar. The quality of the lube oil has also deteriorated considerably, according to the tests carried out by our station Chemist.
Waiting patiently for your reply.
Thank you!

Thanks for the information; it should be very helpful (though without being able to see the Starting Means P&ID I personally have a difficult time visualizing the turning gear mechanism....).

I presume you didn't have to manually rotate the turbine-generator shaft this time.?.?.? You just waited for the starting motor lock-out relay to reset and changed the torque converter guide vane angle (manually???)?

Here is what I think of when I think of L14HRZ:


If this isn't what the L14HRZ rung looks like at your site on your machine, it would be very helpful if you could send a snippet or CLEAR photo of the L14HRZ rung in the Mark* at your site.

Let's start with L14HR. L14HR is a logic "1" when the shaft is at Rest--when it's at zero speed (or just before it hits zero speed--a couple of RPM, I can't remember the setpoint). [The "R" in HR stands for at Rest.}

The above rung L14HRZ says that when L14HR IS NOT a logic "1" then L14HRZ WILL BE a logic "1".

All of the above means when the shaft is at Rest (at zero speed) L14HR will be a logic "1" and L14HRZ WILL NOT be a logic "1"--it will be a logic "0". Or, said another way, when the shaft IS NOT at Rest L14HRZ WILL BE a logic "1".

You wrote above:

" As for the L14HRZ signal, it is one of the permissive signals for starting the offline compressor water wash. This is because the unit must be at standstill (zero speed) before you can carry out an offline compressor water wash. That is why when were crank the unit before selecting water wash, we force the signal from a Zero to a One, in order to deceive Mark VI that we are at zero speed, so that it allows us to carry out the water wash."

So there's something wrong here--if the unit has to be at rest (zero speed) to start the off-line compressor water wash and it's looking for L14HRZ to be a logic "1" to indicate the unit is at rest (zero speed) AND if the L14HRZ rung in your Mark* is like the one above, then it will never start when the unit is at rest. I think that's a boo-boo in the software--if the software needs to see the unit at zero speed (at rest) to start the off-line compressor water wash then it SHOULD NOT be looking at L14HRZ--it should be looking at L14HR....!

And, since you are forcing L14HRZ to a logic "1" you know (or should know) that EVERY occurrence of L14HRZ in the entire program (application code) causes the contacts associated with the coil L14HRZ to change state--NOT just the one contact in the off-line water wash permissive to start rung. So, this could be affecting other rungs/functions that look at L14HRZ as well.

Enough about L14HRZ and off-line water washing. We would really like to see the entire .m6b file for your unit, or at least all of the off-line water wash sequencing, but that's probably not going to happen.

I am only familiar with Voith torque converters, and I've never worked on one with an analog position indicator as yours seem to have. I have a very difficult time understanding how the unit can START and CRANK when off-line water washing is not enabled/active and have such problems when it is enabled. (Actually, I can; the application code (program) was written by GE Belfort. So it's needlessly complicated, bloated and has a few "bugs.") So, this is one difficulty for me in trying to get my head around this problem.

I don't know which bearings were replaced or what "service" was done to the torque converter. If it's the Voith I'm familiar with, in my personal opinion I would say that, yes, the torque converter limit switches should have at the very least been verified to be correct. BUT, if they weren't correct I would also expect that you wouldn't just have problems with breaking the shaft away when off-line water washing, but ALSO when STARTing or CRANKing when off-line water washing wasn't enabled. (Because in my experience with the Voith torque converters I've worked with the same limit switch settings are used for ALL STARTing/CRANKing operations--including off-line compressor water washing operations.)

Do you know how much current the starting motor draws when it's being started to run up to FSNL (Full Speed-No Load)? 100-125% speed seems a little low, in my experience with Voith torque converters for Frame 9Es and Frame 7EAs. If the starting motor current during a "normal" START is higher, then I would suggest there is something amiss with the fill/drain solenoid operation (20TU-1). (I'm presuming because the unit has a turning gear motor there is no 20TU-2--but without being able to view the Starting Means P&ID I am at a disadvantage.)

Anyway, that's about all I can add. I think the software is a victim of GE Belfort engineering--it would not be the first--and it will NOT be the last. BUT, that is based on the information provided, and not being able to see the application code (program) running in the Mark*. AND, not being able to see the Starting Means P&ID.

There's another possible scenario which may be at play here ... Again, you wrote:

"As for the L14HRZ signal, it is one of the permissive signals for starting the offline compressor water wash. This is because the unit must be at standstill (zero speed) before you can carry out an offline compressor water wash. That is why when were crank the unit before selecting water wash, we force the signal from a Zero to a One, in order to deceive Mark VI that we are at zero speed, so that it allows us to carry out the water wash."

You made a couple of statements that are conflicting if they are correct as written. The first one is: "...the unit must be at standstill (zero speed) before you can carry out an off-line compressor water wash." The second one is: "...before selecting water wash, we force the signal [L14HRZ] from Zero to a One, ... so that it allows us to carry out the water wash." MAYBE the GE Belfort logic wants the unit NOT to be at zero speed WHEN you select/enable the off-line water wash .?.?.?

But, actually, the more I read your posts the more confused I become. Because NOW you seem to be saying that even when the unit WASN'T being washed (off-line) it was not possible to break the shaft away from zero speed with the cranking motor.

I don't recall exactly how large (HP) the cranking motors on the Frame 9Es that I worked on were, but they were probably around 900 HP if I recall correctly. The required current for breaking the shaft away from zero speed at the voltage the motor was operating at was around 150%-160% of nameplate rated current. A LOT of people cringe when they hear that number--but it only occurs for the acceleration to purge speed and during purging and also during acceleration after firing--which is not a long time for the motor, which usually has Class F insulation and a high duty factor rating, also. You are saying that the unit at your site broke away with 120-125A (Amperes), and we don't know what the motor nameplate rating is (HP AND current).

So, it's simply not clear to me what the configuration is, and it would be helpful to see drawings and know nameplate ratings--AND to see the operating instructions for Off-Line Compressor Water Washing provided by GE Belfort as well as the programming of the Mark*. But, my guess at this point is: the GE Belfort Bunch has struck again. Based on the informaton provided. Either there's some flaws in the application code (programming) OR there is some problem with the torque converter limit switch settings (I had heard that GE Belfort were using the analog position feedback for controlling the torque converter output, but, then I've also heard they were using actual starting motor current feedback for the same thing--you gotta love the GE Belfort Bunch--NOT!!!).

I think without being able to see drawings and the application code and having some other important (to me) information I'm going to have to sit the rest of this thread out. Sorry. When it comes to GE Belfort, I am easily confused and amazed, and often disturbed. One of the things one could almost always count on with GE Schenectady or GE Greenville is that they developed schemes and tested them and used them for years--decades, even. It made for understanding and explaining and troubleshooting much easier. GE Belfort believes their way is always better, and they are free to change anything from one machine to the next as they see fit. And, they do. Often. BUT, without the proper consideration and testing. "If it ain't broke, break it!" seems to be GE Belfort's model and mode of operation. In all reality, they should be helping you troubleshoot this and fix this since you seem to have said this off-line water wash cranking problem has been around for a LONG time, possibly since commissioning.

Best of luck! Please write back to let us know what you discover and how you resolve the problem! A LOT of people read these posts and learn from and apply the knowledge they gain from reading about how problems are resolved. "Feedback is the most important contribution!" (c) here at
I guess I can't resist....


This is pretty common logic from GE USA; probably not anything like GE Belfort's sequencing. L83BW is a logic "1" when CRANK is selected (L43C is a logic "1"), Off-line Water is selected (L43BW is a logic "1"), a START is initiated (L1X is a logic "1"), the unit is NOT at zero speed (L14HRZ is a logic "0"), and it latches through the L4Y contact and remains a logic "1" until 1 second after L4 changes to a logic "0" (L4Y goes to a logic "1") AND L43BW changes to a logic "1" (Off-line Water Wash is selected OFF).

It would be very interesting to see the equivalent GE Belfort rung in use at your site....

Because, basically, the above rung says that CRANK has to be selected AND the unit has to be ABOVE (NOT at) zero speed (for L14HRZ to be a logic "0" to CLOSE the Normally Closed contacts in the rung above), AND a START has to be active (L1X is a logic "1"). So, with L43BW a logic "1" when the unit is at zero speed, as soon as a START is initiated AND the unit goes above zero speed (when L14HRZ goes to a logic "1") the unit will automatically go into Off-Line Water Washing mode.

I have seen this perceived problem before--operators, supervisors and Plant Management thinking the unit should (MUST) display Off-Line Water Wash Selected BEFORE initiating a START.... When it can't and won't indicate the Off-Line Water Wash function is enabled and active until AFTER the unit is STARTed while in CRANK mode.

Is that what's going on at your site? Thinking that Off-Line Water Wash MUST be displayed (enabled/active) BEFORE START is initiated? (I'm presuming the application code is similar to if not exactly like what's been shown in this response (L83BW) and previously (L14HRZ).)
CSA, I am very happy with the interest that you have in our problem. I believe that I haven't been clear in my earlier submissions, so I well endeavour to be very clear this time around.
First of all, This unit has commissioned in 2009 and has been running very well with high availability and reliability since. The water wash system has also been operating very well with no hitch until last two years.
The compressor offline water wash's normal sequence is that you L14HRZ should be a "One" in order for you to get one of the permissive for the water wash. Our rung is different from the rung you depicted in your post. On ours, the functional block is a move block and L14HR is moved to L14HRZ, which means when L14HR is a "One", L14HRZ also becomes a "One". L14HR is not an input to any water wash block and therefore the pins for it in the toolbox do not have water wash included, however, for L14HRZ, it is an input to a water wash functional block and therefore its pins in toolbox has water wash included. This clearly indicates that the water wash can only be carried out at zero speed and not on turning gear speed or crank speed.
Now, because of the problem we have breaking the turbine away from zero speed, we have resorted to cranking the unit from turning gear and then selecting water wash. This process is at variance with the water wash procedure and therefore the water wash system ( such as Inlet guide vane opening fully to 84 degrees, both exhaust frame blowers running, 20TW_1 opening, etc) would not work. This is because of the zero speed permissive. In order for us to still carry out the water wash, we trick Mark VI to think that the unit is at rest by forcing the signal L14HRZ. Mind you, this is an abnormal operation!!
About the problem of the starting motor's inability to break the turbine shaft away, we used to think that it only occurs when we want to carry out an offline water wash, because previously, it mostly occurred whenever we isolated the unit for the water wash and selected Water Wash Start on the HMI. However, I wanted to also add that there have been a few occasions when the problem occurred even though we were not carrying out water wash, such as, last Saturday's incident. Where the unit was on turning gear and due to a power disruption, the turning gear motor went off and the gas turbine shaft slow rolled to stand still. Every attempt to use the starting motor to bring the unit back on turning gear (as has always been the practice) proved futile.
The unit's starting motor rating is 1000KW, 6.6KV, which means the rated current is about 100A. When we attempted to put the unit again on turning gear (always with the help of the starting motor, because they share the same shaft) after allowing the shaft to naturally cool down and straighten over a 48-hour period, we measured the current readings of the starting motor and it was 120A and the gas turbine shaft failed to break away. We then changed the torque converter guide vane angle by changing the control constant tmkgv in the Mark VI toolbox from 68degrees to 72 degrees. This time around the gas turbine shaft was able break away and the starting motor current reading had increased to 125A.
I hope this is clearer and it helps with the analysis. You have been very helpful and your post have been very insightful and invigorating. Thank you!

One's smartphone can be used to take a CLEAR photo of the rung in question and then you can attach it to a reply here and we can SEE the rung and know what it looks like. NORMALLY a suffix of 'Z' on a signal name means the signal (in this case L14HRZ) is the INVERSE of its namesake (in this case L14HR).

Here is a snippet of a Mark VI L14HRZ MOVE function block (rung) from a Mark VI software I have:


You see that tilde in front of the G1\L14HR signal name? That tilde means it is INVERTED--in other words the input to the SRC parameter of the MOVE block is Normally Closed. (If there isn't a tilde next to the signal name the input is Normally Open.) The function block (rung) above is exactly equivalent to the L14HRZ rung I copied from a Mark V software. The L14HR signal is Normally Closed ("inverted").

So, take a CLEAR photo of the MOVE block in your application code, and attach it to the response. THEN we can see what you see. It's not that difficult. And, while you're at it, take a photo of the rung where you believe L14HRZ needs to be a logic "1" to get the Off-line Water Wash active.

L14HRZ--since it is a "function" of L14HR (it's just an inverted function!) and NOTHING else--is an indication of the state of L14HR (which is a logic "1" when the shaft is at Rest). L14HRZ is an INVERSE function of L14HR--meaning when L14HR is a logic "0" L14HRZ will be a logic "1" and when L14HR is a logic " L14HRZ will be a logic "0". L14HRZ is the OPPOSITE of the state of L14HR. It can be said many different ways--but, when correctly written, L14HRZ is an indication of the state of L14HR, and therefore the state of the shaft (in terms of speed, even if the speed is zero).

In the programming I described, Off-Line Water Washing IS NOT carried out at zero speed--it's not even enabled at zero speed. It can be selected at any time (L43BW goes to a logic "1") BUT L83BW, the signal that enables Off-line Water Washing CAN'T go to logic "1" until AFTER the unit breaks away from zero speed (when L14HR goes to a logic "0"--and L14HR goes to a logic "1"). People insist that the HMI display MUST indicate Off-Line Water Washing BEFORE they initiate a START--and that's just NOT possible until L83BW goes to a logic "1"--which IS NOT until AFTER the shaft is turning. The operator can select Off-line Water Wash either BEFORE initiating a START or AFTER initiating a START, but in either case nothing is going to really happen until AFTER the shaft is turning after a START is initiated. Full Stop. Period. That's been the case for decades in logical, rational GE programming.

You wrote: " This clearly indicates that the water wash can only be carried out at zero speed and not on turning gear speed or crank speed." And I respectfully submit that IS NOT true or correct. At zero speed, any water/detergent sprayed into the compressor inlet (bellmouth) isn't going to go very far into the axial compressor.... And it's for THAT reason that the machine HAS to be spinning when performing an Off-Line Compressor Water Wash.

You say the water washing worked well until a couple of years ago. What was the procedure you used for Off-Line Compressor Water Washing before it stopped working? Did you have to force anything?

All the Off-Line Compressor Water Washing programming I have seen on GE-design heavy duty gas turbines REQUIRES the unit to be CRANKing during the procedure. The unit MASTER CONTROL is put in CRANK mode, a START is initiated, and Off-line Water Washing is selected--this sets L43BW to a logic "1" and once the shaft breaks away from zero speed (L14HRZ goes to a logic "1") then the sequence is begun. Yes, the IGVs open and there is a permissive to manually open the motor-operated Water Wash Valve (20TW-1). Sometimes there is a signal from the Mark* to start the Water Wash Skid, and sometimes it has to be manually started. The unit goes to purge speed and then drops back to about 10-12% speed for the duration of the washing. The operator then selects STOP, and the unit coasts down to zero speed, and the "soak" period is begun.

When the soak is complete, the operator again initiates a START with the unit in CRANK mode, and this time (because L43BW remained a logic "1") the water wash sequence starts, opening the IGVs and allowing the motor-operated Water Wash Valve to be opened and rinse water is injected into the axial compressor inlet (bellmouth). The unit goes up to purge speed, then drops back down to about 10-12% speed for the remainder of the rinsing period. Once the rinse water is deemed clear enough, the operator again selects STOP AND Off-Line Water Wash OFF and the unit coasts down to zero speed and the work of restoring the valves to their normal running position is begun.

Some sites had clever commissioning engineers who modified the programming to make it a little more automated, but all that really succeeded in doing was causing confusion for people who tried to understand or explain how it worked later....

I'm going to say again: In my personal experience, especially with an air-cooled generator, GE-design Frame 9Es (and Frame 7EAs) require about 150-160% of rated starting motor nameplate torque to break the shaft away from zero speed reliably and repeatedly. Sure, depending on oil temperature and machine condition (how long the bearings have been in service; how hot the axial compressor is; torque converter condition (age; adjustment); etc.) it is possible to break the shaft away from zero speed with 130-140% of rated starting motor nameplate torque--but it doesn't always happen reliably. I've seen machines that had new bearings (turbine and generator) installed during a maintenance outage that were so tight the torque converter had to be "bumped up" to get the shaft to break away from zero speed. Sometimes this had to be done for three or four months, depending on how the machine was operated and how many times it is normally started.

By any chance, did this problem with the inability to break the shaft away from zero speed begin sometime AFTER the torque converter was "serviced"??? Because, this would likely explain a lot--about the inability to break the shaft away from zero speed. If the torque converter limit switches weren't checked adjusted after the "service" then that could be a part of the problem.

You mention the L.O. quality isn't very good. Dirty L.O. flowing through the torque converter at the pressures and flows required for starting/accelerating could certainly cause wear and erosion in the torque converter. There is usually a strainer in the suction of the torque converter--and it could also be full of dirt and debris, robbing the torque converter of oil flow and reducing its effectiveness and torque transmission. The current being drawn by the starting motor is a DIRECT reflection of the amount of torque the starting motor is producing. If it's not producing normal torque, the current drawn by the starting motor will be lower than normal.

SOMETHING CHANGED about two years ago--your job is to remember, or find out what. I don't recall precisely the Section/Sub-Section number of the Control Specification that usually lists the approximately starting motor torque (in percent of rated) but usually there IS a sub-section which does list this value for GE-design Frame 9Es (and 7EAs). And, it's almost ALWAYS 150-160% of rated--for a starting motor rated at 100A, that would be 150-160A (because current is directly proportional to torque production (this is pretty true of almost EVERY electric motor)).

PLEASE take a CLEAR photo of the rungs (function blocks) for L14HRZ and whatever the rung is for enabling (NOT selecting--so NOT L43BW) Off-line Water Washing and attach them to your next response to this thread. Off-Line Water Washing IS NOT done at zero speed; it's done WHILE the unit is spinning. Whether it is enabled at zero speed or when the unit is CRANKing is immaterial. But, in my personal experience, it will ONLY be enabled (L83BW) will ONLY be set to logic "1") when L14HRZ is a logic "1"--which is when L14HR is NOT a logic "1".


The function block (rung) above is from the Mark VI software I have. There are two additional permissives (L69TWW and L3WATID) that just try to ensure the unit isn't being washed when the ambient temperature is too cold and the water being used to wash the axial compressor is at minimum temperature--otherwise it's the same as the rung I posted earlier (from a Mark V). The A parameter signal (L43BW) can be selected ANY time--either BEFORE the unit is STARTed in CRANK or after; it doesn't make a difference. In this case the unit won't start washing until the unit gets above L14HT--and that's 100 RPM, if I recall correctly; so just replace L14HT in the block (rung) above with L14HRZ--it's essentially the same.

(I have a suspicion the GE Belfort sequencing is probably a little different.... I don't know why I suspect that, but I do.)

Send the CLEAR photos.


As I've written, most people are shocked (no pun intended) to hear of the starting motor drawing 150-160% of rated current during CRANKing and acceleration. And, since your site has been in operation for years and it doesn't sound like there is any past record of the current drawn by the starting motor during CRANKing and acceleration it is probably shocking for you and others at your site to even contemplate this much current on a regular basis. Most of the induction electric motors used as starting motors for GE-design heavy duty gas turbines have very good winding insulation (Class F), and have a high service factor/duty rating. These motors aren't operated at currents like this all day, every day--only during CRANKing and acceleration. Specifically, during purging and acceleration--usually. In fact, usually when the starting motor is "de-coupled" from the turbine-generator shaft (by de-energizing the torque converter fill/drain solenoid, 20TU-1) there is some sequencing that keeps the motor running for a minute or two or three with no load (the ampere draw during this time is around 50-60% of rated) just to cool the motor after acceleration.

So, if you or someone at your site is having heartburn and anxiety over the current values I have posted--it's understandable. But, if you speak with GE and get answers from knowledgeable engineers (not field service people--unless they have many years of experience) you will probably find the values are pretty typical and customary and ordinary.

Many large air-cooled generators use different types of generator rotor bearing--not journal type bearings. AND, since you have confirmed the Brush generator at your site employs bearing lift oil ("jacking oil") to provide a means of ensuring the rotor is NOT in contact with the bearing material during break-away and low speed operation that is a further indicator of the amount of torque required from the starting means to break the turbine-generator shaft away from zero speed.

I can't speak to why your problem of breaking the shaft away from zero speed seems to be more common when performing an Off-Line Compressor Water Wash, but the fact that it also happens during other STARTs as well can certainly indicate the amount of torque being provided by the torque converter to break the shaft away from zero speed is marginal. The torque adjustor mechanisms I have worked on that were provided with Voith torque converters (Siemens and Auma) were German marvels of engineering. They had brakes to make sure the motor STOPPED when it was supposed to stop. They had very intricate adjusting mechanisms (which took some familiarization!) which were extremely precisely adjustable. And, to my knowledge they didn't drift (change setting over time). I'm not saying it can't happen (drift)--I'm saying I've never experienced it AND based on the construction it just didn't seem like it was even possible to happen.

By opening the torque adjustor mechanism "manually" you are increasing the amount of oil flowing through the torque converter (from the hydraulic pump to the hydraulic motor)--which requires more current from the starting motor. Not knowing what was done or how it was done by the torque converter service person it's impossible to say if it could have resulted in lower current draw/reduced torque output. I will say that I have been told--and experienced--that manually CLOSING the torque converter guide vanes (with the hand-wheel and manual engagement mechanism) while transmitting torque (when the starting motor is running AND 20TU-1 is energized) CAN and WILL damage the torque adjustor mechanism (which is like a fragile rack and pinion mechanism) in the torque coverter (not the motor-operated torque adjustor mechanism with the limit switches and position indicator). It bends the rack mechanism, and it doesn't take a lot of force to be bent such that it won't work reliably.

So, I'm NOT saying the application code (programming/configuration) in the Mark VI is right or wrong. But I am saying that based on my personal experience and the current values you have provided that it's entirely possible that the starting motor is not providing sufficient torque to break the shaft away from zero speed because the torque adjustor is not adjusted correctly, or something has changed since it did work correctly, and it needs to be verified for proper adjustment/operation.

Anyway, best of luck! Please continue to write back to let us know what you find. It would also be helpful to know if PRIOR to this break-away problem if it was always necessary to force something to get the Off-Line Water Wash sequence to work properly.

Send CLEAR photos of function blocks ("rungs")--please.

we are facing the poblem "sarting means turb shaft fail to break turbine away" ,the crank motor fail to rotate the shaft and we do all solution except manually rotate the shaft ,all parameters are healthy ok .please we need help to rotate the shaft .
We are thinking to rotate it manually after more than 20 attempts . what we can do that?