Torque Convertor Operation

C

Thread Starter

Control

Hi!

I work in a Natural Combined Cycle Plant Power which have MS9001E, Frame9E and Mark V control. I'm operator in Control Room. Our GTs use Voith Coupline for start mean. I want to learn about Torque Convertor. How operates? How works TM88 Motor, 33LIM Switches and during start up What is position of blades? Thank you..
 
Great questions (no high-level maths required to answer them!)!

A torque converter is a means for controlling the amount of torque being transmitted from one device to another. In your case, a starting means (electric induction motor running at a relatively constant speed) is required to accelerate the turbine-generator shaft from zero speed up to approximately 60% of rated speed. We can't just directly couple the induction motor to the turbine shaft--the size of the motor and the inrush current required to break the turbine-generator shaft away would be enormous. The motor would be very expensive, and the in-rush current would cause a very large draw on the grid supplying the motor mains power supply.

A torque converter is essentially a hydraulic pump (driven by the starting means motor) and hydraulic pump (driving the turbine-generator shaft). So, the coupling between the starting means and the turbine-generator shaft is hydraulic and has "slip"--the ability of the two shafts to rotate at speeds independent of each other.

Now, by varying the positions of some control vanes (like variable turbine nozzles) we can also control how much torque is transmitted from the starting means to the turbine-generator shaft. Closing the torque converter control vanes (some call them "guide vanes") reduces the amount of torque being transmitted; opening the torque converter control vanes increases the amount of torque being transmitted.

The position of the torque converter control vanes is controlled by means of a 3-phase fractional horsepower, reversing motor, 88TM. Rotating 88TM in one direction opens the control vanes; rotating it in the other direction closes them.

Finally, there are limit switches that are adjusted to provide the desired speed or torque. These switches are adjusted to levels which should be listed in the Control Specification-System Settings document provided with every Speedtronic turbine control system and specific to every turbine. The limit switches (several of them depending on the configuration) are wired to the 88TM motor starter, and or the Speedtronic turbine control system. Also, a couple of the limit switches are usually used internally in the Torque Converter's Torque Adjustor Drive Mechanism (which 88TM drives to change control vane position) to set end of travel limits.

You will need to look at the Control Specification drawing for your site to find the torque adjustor limit switch settings for your site (speed, or starting motor current (which is directly proportional to torque), or whatever the setpoints are defined as).

Usually, when the unit is started from zero speed or Cooldown, the torque convertor control vanes are set to near maximum to transmit as much torque as possible from the starting means induction motor to the turbine generator shaft to accelerate the unit up to purge combustible gases from the turbine and exhaust (including the stack and the HRSG (Heat Recovery Steam Generator--boiler). Shortly after the induction motor is started and hopefully has reached rated speed, the torque converter is pressurized by the energization of a solenoid (usually 20TU-1). This pressurization of the torque converter means that the output of the hydraulic pump side of the torque converter is connected to the hydraulic motor side of the torque converter, and that torque from the induction motor is being transmitted to the turbine-generator shaft.

At most sites, the purge is done at a "high" speed (approximately 20% or so) in order to shorten the amount of time to purge combustible gases from the unit, HRSG and exhaust.

After the purge time is complete, the torque converter is de-pressurized by de-energizing 20TU-1; this stops the transmission of torque and the turbine-generator shaft speed starts to decelerate. At this same time the torque converter control vanes are repositioned to a lower setting.

Once the unit coasts down to approximately 9.5% speed, the torque converter is again pressurized and the turbine-generator shaft should begin to accelerate slowly. As the speed increases to greater than 10%, fuel is admitted to the machine and the spark plugs are energized. Shortly after flame is detected, the torque converter control vanes are opened, usually to near maximum to help assist with accelerating the unit (there is insufficient torque from the hot combustion gases to accelerate the turbine-generator shaft without an assist from the starting means through the torque converter).

Once the turbine-generator shaft speed reaches approximately 60%, the torque converter is again de-pressurized to stop the transmission of torque. The induction motor usually continues to run for between 2 and 5 minutes to cool the motor. (During purging and acceleration, the induction motor may be producing as much as 150-160% of rated torque! This causes the motor to become very warm, and this "cranking motor cooldown" period, as it's called, helps to more quickly cool the motor just by spinning it without transmitting any torque. Don't worry, though; these motors have a very high insulation class rating, usually Class F, and since they aren't used at 150-160% of rated current for extended periods of time they still last many years with normal maintenance. They are all usually protected by dedicated protective relays which monitor winding temperature and/or stator current to protect the motor against severe damage.)

One last thing to note with respect to these large induction motors used for starting means on Frame 9Es: They should only be started 2-1/2 times per hour. Because they are medium voltage motors (meaning 2-6KV), and because they are induction motors, they draw large amounts of inrush current which causes the rotors--and stators--to get very warm very quickly. So, the number of starts per hour is supposed to be limited to protect against overheating caused by high inrush currents. Some of the motor protective relays actually count the number of starts and prevent more than 2 or 3 starts per hour.

The 1/2 start per hour number means that if the first start was done with a "cold" induction motor (one that hasn't been started or run within approximately 18-24 hours), as many as three starts in one hour can be attempted without causing damage to the motor. If, the motor had been started and run within 18-24 hours of the first start attempt in one hour, only one more start in that hour should be attempted to protect the motor. Again, some--but not all--motor protective relays actually "count" the number of starts-per-hour and will limit the number of starts if necessary. If the relay on the starting motor at your site does not, then it's up to the operators and their supervisors to keep track of the number of starts-per-hour, and how long since the last start/run, to protect the motor.

Now, the manuals provided with the turbine-generator should have some system descriptions, one for each of the major systems on the unit and auxiliaries. These are helpful in understanding the systems and how they, and their components, operate.

Also, there is always a set of P&IDs provided with every GE-design heavy duty gas turbine. Having these in the control room and available for the operators and technicians to view and familiarize themselves with, is critical to good, efficient plant operation. And, having a copy of the Control Specification-System Settings document in the control room is also beneficial. There is one other document which is very helpful: the Device Summary. It contains the setpoints of many field devices and instruments on the turbine, generator and auxiliaries. For example, if the Speedtronic panel annunciates "L.O. TEMP HIGH", it doesn't usually tell you what the alarm setpoint is. You can, once you become familiar with the machine and the documents, find that the L.O. Temp. High Switch, 26QA-1, is set at approx. 74 deg C.

Hope this helps! Learn to find and use the available documentation--and when you have questions after you've consulted them, feel free to ask here!
 
> have you considered reading the manual?

Bob,

Believe it or not, I've been to tens of sites where the manuals are locked away and not available to operators <b>OR</b> technicians.

Sad but true.

When you ask why, you just get a shrug of the shoulders. When you ask the supervisors with the keys, "Why?" they just get angry and refuse to answer. As a former GE employee and even more recently I've been refused access to the manuals on more than one occasion.

Must be they are considered to be a Pandora's Box.

And, in fairness, most GE manuals don't provide the level of information most people seek. They do include the manufacturer's instruction books, but they don't provide the specifics of how the equipment is actually being used on the unit--which is what most people want to know.

So, "reading the fine manual" doesn't always result in obtaining the desired (or required) information.
 
Hi!

You are right..

I often read manuals but usually not enough to my understanding. In fact I asking this question because we have a problem that relation with cooldown. The rotor, while cooldown (21 to 100 rpm) cycle, turnover rate from 100rpm to 21rpm is dropping fast. Approximately 20 minute. Why?

Thank you..
 
Hi!

WHEN DID THIS PROBLEM START?

WHAT HAVE YOU DONE TO TRY TO TROUBLESHOOT AND RESOLVE THE PROBLEM?

WHAT WERE THE RESULTS OF YOUR TROUBLESHOOTING?

Has it been occurring since commissioning?

Did it start after a maintenance outage?

You should know that newer GE-design heavy duty gas turbines do not use "slowroll" via the torque converter as was done for many years. We can't know that unless you tell us, and then we can provide more information.

Was something done to the Torque Adjustor Limit Switch settings prior to this problem?

What is the L.O. Header temperature when Cooldown starts?

What is L.O. Header temperature when the RPM drops below 25 RPM?

You said this is a combined cycle power plant. Where does the Cooling Water for the turbine L.O. Coolers come from? Is the flow of Cooling Water to the turbine L.O. Coolers reduced or shut off when the unit goes on Cooldown?

During a recent maintenance outage, were the turbine and/or generator bearings replaced with new (or refurbished) bearings?

If the bearings were replaced, were they aligned after replacement (usually using a laser alignment tool/process)?

If the bearings were replaced, was the unit re-aligned to the generator and the accessory gear?

When you ask a question like this, try to provide as much information as you can. If someone unknown to you says, "My watch isn't working; do you know why?" how would you respond? Help us help you by telling us as much as you know about the problem, when it started, and what the results of any of your troubleshooting and resolution efforts were, and try to anticipate questions you might be asked.

And, don't forget to take a few minutes to tell us if the information provided is useful or not, and if you were able to resolve the problem using the information provided, or how you were able to resolve the problem. "Feedback is the most important contribution!"(c) here at control.com. Many others read these posts, and it's helpful to others to know if you found the information and help provided was useful or not, and if you were able to resolve the problem, and how.

And if you use the 'Search' feature of control.com, you will find many threads with information you will probably find useful. And, I'm certain the most useful threads and information you will find will be those with feedback from the original poster letting others know if the information was helpful or not.

We're always willing to provide more information if you need, or to clarify issues or answer questions (we DON'T deal in doubts!). But, we can provide more helpful and concise answers when you provide as much information as possible in your original post or when asking a question about a problem you are experiencing.

And, please answer all the questions asked--even if you think they are irrelevant. Sometimes we ask a lot of questions, but usually when we have very little information to work from. Again, help us help you.
 
<b>CORRECTION</b>

This sentence from the above post is incorrect:

>A torque converter is essentially a
>hydraulic pump (driven by the starting
>means motor) and hydraulic pump (driving
>the turbine-generator shaft).

It should have read:

A torque converter is essentially a hydraulic pump (driven by the starting means motor) and hydraulic <b>motor</b> (driving the turbine-generator shaft).

Apologies for any confusion.

 
Hi!

Thanks you for your answer..

I think this problem started after replacing of the old Torque Convertor unite with a new. Old unite was VOITH (siemens) but new unite is AUMA.

I think the switches was readjust because new switches was different.

There is closed-loop cooler system at our site for L.O. The water is cooled by fans. When reached Water temp. 59 C the water cooling pump runs while Cold Down cycle. Usually Oil Temp. is high. What could be ideal oil temp. while Cool Down cycle?
 
Hi!

I have never seen an AUMA Torque Converter, but I have seen AUMA Torque Adjustor mechanisms used on Voith torque converters. Functionally, the AUMA mechanism is identical to the Siemens mechanism, but there are some small differences.

Adjustment of the limit switches is very important and is probably the likely cause of your problem(s).

L.O. temp should not be less than approximately 27 deg C (80 deg F). Cold L.O. increases the resistance in the turbine and generator bearings. Ideally, it should be maintained at normal operating temperature (approx. 52 deg C, 125 Deg F).

Here's something you can try to see if it helps the issue (presuming the L.O. Temp is sufficient and all other parameters are good). There is a handle on the side of the Torque Adjustor mechanism and a handwheel on the top of the Torque Adjustor. Cast into the handwheel rim are arrows for OPEN and CLOSE. Turning the handwheel in the OPEN direction will open the control vanes in the torque converter and increase the amount of torque being transmitted.

So, first make sure you know which direction to turn the handwheel to OPEN the control vanes. Then, while the unit is on slowroll (Cooldown) below 100 RPM), push the handle on the side of the Torque Adjustor mechanism down and hold it in the down position and turn the handwheel in the OPEN direction. You must hold the handle down while turning the handwheel in order for the manual mechanism to engage to open the torque converter control vanes. This will effectively bypass the limit switch setting for slowroll/cooldown, but it's only a temporary bypassing of the limit switch.

Try opening the control vanes half a turn of the handwheel and observe the effect. It won't be immediate, but you should see something. It would be best if you were plotting TNH while doing this to see the change in speed. It may take a minute or two to see any effect. And, you may need to turn the hand-wheel in the open direction another half-turn after a few minutes. And possibly even another half-turn after a few more minutes. Patience is the key.

The turbine-generator shaft is very heavy and it has a lot of inertia, and the amount of torque being transmitted while on slowroll/Cooldown is minimal. It is really only enough to maintain RPM above about 20-25 RPM and that's about all. It can sometimes accelerate the shaft a few RPM, but not much, especially if the L.O. Temp is cool (less than approximately 40 deg C).

If you are successful in keeping the rotor spinning at whatever RPM it was spinning at before the Torque Adjustor/Torque Converter was changed, then you need to have your maintenance technician remove the cover of the Torque Adjustor Mechanism and adjust the appropriate limit switch to the current position. You can do this when the shaft is spinning on slowroll/Cooldown--no problem. I can't tell you which limit switch to adjust without being on site and able to see the mechanism and the wiring and limit switches and the Torque Adjustor motor starter wiring diagram.

I caution you strongly: DO NOT TURN THE HANDWHEEL IN THE CLOSE DIRECTION WHILE ON SLOWROLL/COOLDOWN (i.e., when 20TU-2 is energized). The Torque Adjustor mechanism can be damaged by trying to close the control vanes while torque is being transmitted. And, especially do not turn the handwheel in the CLOSE direction when 20TU-1 is energized (and don't use the Torque Adjustor motor starters LOWER P/B to close the torque converter control vanes while 20TU-1 is energized (such as during starting, purging, accelerating). Much more torque is being transmitted during starting, purging and acceleration and the possibility of damaging the torque converter control vane mechanism is much higher. Opening the control vanes while torque is being transmitted is fine; closing them is not recommended.

Finally, if your experiment is successful but it's not possible to have someone adjust the limit switch at the time of testing, just record the number of turns of the handwheel and you can adjust the limit switch later, even when the unit is not on slowroll/Cooldown. Just make sure the Torque Adjustor mechanism is in the position it would normally be in while on slowroll/Cooldown and then manually open the handwheel the number of turns determined from the test and make the limit switch adjustment.

And, if you can't make the adjustment to the limit switch at the time of testing, when you START the unit again, nothing will change--the Torque Adjustor will operate just as it did before the testing because you only temporarily bypassed the limit switch for your test--no permanent changes were made. Just remember to hold the handle down before and while turning the handwheel.

So, the test is benign in nature and is simple and doesn't affect any current settings.

When you release the handle on the side of the Torque Adjustor mechanism it will automatically disengage the manual mechanism, and the next time the unit is STARTed, the electrical mechanism will operate normally. You don't have to do anything else when you are finished with the test--just release the handle on the side of the Torque Adjustor mechanism. (Remember, don't turn the handwheel in the CLOSE direction while on slowroll/Cooldown, i.e., while 20TU-2 is energized, and especially not when 20TU-1 is energized!)

Please write back to let us know how you fare. Remember, it's best to have some kind of trend or graph or plot of TNH running while performing the test. You will need to disable the fire protection system while someone is in the Accessory Compartment manually operating the Torque Adjustor mechanism.
 
<b><pre><i>Teaching Moment</b></pre></i>
For anyone reading this post, this is a perfect ("textbook") example of the majority of problems for just about any system or piece of equipment experiencing problems. Something changed. After something changed problems were experienced. The problems are likely related to what was changed just before the problems started.

Also, when asking for help with problems (whether speaking directly with someone, or writing to a forum like this) one should always provide as much information as possible about <b>when the problem started and what changed or occurred just before the problem started.</b>

We could have saved a lot of back-and-forth here had we known the unit has been operating for some time with no slowroll/Cooldown problems, and the torque converter (or at least the Torque Adjustor mechanism of the torque converter) was replaced, and then problems started occurring.

Whenever troubleshooting a problem with a machine or piece of equipment that has been working for some time with no problems and then begins experiencing problems, the <b>FIRST</b> question that should always be asked is:

<b>When did this problem start?</b>

Followed immediately by:

<b>What changed or occurred before the problem started?</b>

Now, the mechanical department and the technician who disconnected/reconnected the wiring to the Torque Adjustor mechanism in this case will always say, "We did everything just right, and any problem is NOT related to the work we did. It's that $%&#ed Speedtronic panel! Just look at all the wiring and blinking lights inside that panel--it has to be the Speedtronic panel!" But, as we have learned time and time and time and time and time and time again, it's not usually the Speedtronic panel (or the electro-hydraulic servo-valve, or the LVDT feedback calibration) that's the problem.

End of teaching moment.

We return you to your normally scheduled programming.
 
This is the wonderful simple words description of the operating sequence & explained by wonderful man. The CSA.

Thanks lot. Once Again..

Earlier in this thread, the CSA also said that "Reading Manual" does not provide the detail & clear operating & working sequence. I don't know why but this is happening.

Besides having basic engineering knowledge,Every owner/user wants to know that what is happening & <b>Why</b> this is happening, whenever the command is given. How this control constant value is selected.

I have seen the cases when a fresh engineer can not come to understand What makes the control system to declare the machine is at base load by reading just manual.
 
Hi!
i want to ask about torque converter (using Voith Type EL 10 z FT) :
- how to set limit switch for get optimum output torque converter?

I've some problem with torque converter. when i start gas turbine, the flame loss and then the temperature in motor cranking is so hot.
can u help me to solve my problem? thanks..
 
Hi!

Quoting from a previous reply to this thread:

>..., when asking for help with
>problems (whether speaking directly with
>someone, or writing to a forum like
>this) one should always provide as much
>information as possible about <b>when
>the problem started and what changed or
>occurred just before the problem
>started.</b>

So, <b>when did this problem start?</b> After a maintenance outage? After the fuel control valve LVDTs were "re-calibrated"? After the torque converter was refurbished?

What has been done to try to troubleshoot the problem?

What were the results of the troubleshooting?

There were several different schemes used to control the torque converter output, and we don't have any idea which one is in use at your site. We don't know which version of Speedtronic turbine control panel is being used at your site. We also don't know what fuel you are trying to start the turbine with (natural gas or distillate). The description of the torque converter you provided is not sufficient; and you are not adjusting limit switches of the torque converter, rather limit switches of the Torque Adjustor Drive Motor, 88TM-1.

I will tell you this: Once the warm-up time is complete after flame has been established if the actual acceleration rate is too high then fuel will be cut back to minimum (FSRMIN, a calculated value) and if that's too low for the air flowing through the machine at that condition flame will be lost. And if the starting motor is producing a lot of torque (meaning it's drawing a lot of amps) then that's a good sign that the acceleration rate is too high.

The high-voltage starting motors used on most GE-design heavy duty Frame 7E/EA and Frame 9E gas turbines operate at 150-160% of rated power during acceleration. That can be seen by observing the amount of current flowing through the starting motor's windings during acceleration and comparing that to the motor's nameplate. Torque (power) is directly proportional to current draw.

Adjusting the limit switches is not an easy task. One needs to know how the Torque Adjustor Drive Motor actuator works and how the limit switches are adjusted--it's not normally intuitive. One needs to know how the limit switches are wired to the Torque Adjustor Motor motor starter control circuit and if any limit switches are wired to the Speedtronic. One needs to be prepared and have at least three people with two-way radios: one stationed at the Torque Adjustor Drive Motor, one observing the starting motor current, and one at the Speedtronic panel to force logic and observe speed.

The turbine has to be "cranking" during any limit switch adjustment, so it's noisy and hot in the Accessory Compartment. And it takes a great deal of patience, and usually about 1-2 hours to do it the first time, sometimes more. A lot of planning needs to be done to limit the number of starts on the starting motor, otherwise the process can take several hours (all the adjustments can be done with a single start if it is planned well in advance and everyone knows what's going to happen and is PATIENT).

Typically there are only two limit switches (out of several) that require adjustment: "Min" torque and "Max" torque. Presuming the unit firing speed (TNK14HM1) is 10%, the "Min" torque limit switch is to be set for 10% turbine shaft speed, +2%, -0%--which means, 10% minimum, and 12% maximum, not less then 10%. The "Max" torque limit switch is to be set for 150-160% of rated starting motor nameplate current--note this is NOT expressed in percent of turbine shaft speed; the turbine shaft speed will be whatever it will be at 150-160% of rated starting motor nameplate current.

Sometimes there is a third limit switch that is connected to the Speedtronic for "purge" torque, which is usually just slightly below the "Max" torque value of starting motor current.

One must force L20TU1X (or whatever the signal name is at your site) to a logic "1" and logic "0" during the procedure. <b>DO NOT</b> lower the torque while the starting motor is running and supplying torque to the shaft (when 20T-1 is energized) or you can damage the torque adjustor mechanism. So, this is why a lot of planning needs to be done and good coordination between the person adjusting the limit switches and the person forcing logic.

I recommend you observe operation of the torque adjustor mechanism when the turbine is at rest and not on cooldown by opening the cover of the mechanism and having someone raise and lower the setting from the motor starter while it's in MANual control. There are many limit switches in the actuator, and you need to identify which limit switches are used in your scheme and would be adjusted, if necessary.

Do this while the unit is not running, when it's not so noisy and hot in the compartment. Make a drawing of the mechanism and put some arrows and notes on it so that you can remember what to do when it is hot and noisy when you are trying to adjust the switches. Read the torque adjustor manufacturer's instructions to determine how to adjust the limit switches--it is NOT intuitive.

A step-by-step procedure could only be provided if we knew the details about your unit and how it's configured. You need to reason this through and develop a procedure that's specific to your site and then prepare for the adjustment in preparation for actually making the adjustments.

I recommend you operate the unit first, in CRANK mode, and determine the actual setting of the limit switches before making any adjustment--in other words, determine the "as-found" condition and then determine if any adjustment needs to be made. You might avoid a lot of work if the limit switches do not really need adjustment.

Again, there's a lot we don't know about this problem, specifically when it started. The more information you can provide in your original post the more concise the replies you receive will be.
 
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