GT frame 9E machine start on DC turning

We have a GE Frame 9E machine.

Wanted to know if the machine can be started with DC turning gear mechanism (considering unavailability of AC turning motor). Will the starting motor not get overloaded considering that with DC turning gear, the speed is 0.25 rpm vis-a-vis 6 rpm during AC turning.
 
Thank you for that reply.

But what I meant to say was that, if a dc turning motor is operating, can you start the turbine. Start up vide dc turning motor in case of non availability of ac turning motor. Is it possible.
 
Have you looked at the HP rating of the Starter vs the turning gear . I don't have a control spec. handy, do you have one? Do you understand what Horse Power is?? Try starting your car with a rubber band instead of the Starter !!
 
What glenmorangie said. I think. I don't really understand the scenario; and I've never seen both an AC and a DC turning gear motor on a GE-design Frame 9E heavy duty gas turbine. (GE Belfort does ... unusual things from time to time (for no other than simply because they can).)

As glenmorangie said, a DC turning gear motor would typically be used for rotating the turbine-generator shaft if it was hot/warm and the AC turning gear motor was unavailable.

And, we would really need to see the programming in the Mark* to be able to say if it would be permissible to do in the Mark* turbine control system. You seem to be saying that to start the GE-design Frame 9E heavy duty gas turbine you are referring to that it has to be on turning gear; is that correct? Can you not start the unit from zero speed? Is it a START-CHECK for the shaft to be spinning on AC turning gear (above some value of RPM)?

Every GE-design Frame 9E heavy duty gas turbine I've every worked on can be started from zero speed (contrary to popular belief on many sites). The recommendation to be on turning gear for some time before a START is initiated is to remove any bow from the rotor if it has been sitting at rest (zero speed) for more than a couple of days. I have even STARTed Frame 9E units that have been sitting for four or five days without being on turning gear for any period of time--from zero speed--and, while the vibration was high during acceleration (above the alarm setpoint), it did not exceed the trip setpoint.

glenmorangie has been in the biz for more years than I and has a LOT more experience than I. He has contributed and continues to contribute to the body of knowledge on this site. Personally, I have benefitted from his knowledge, experience and contributions over the years. While I realize that English is probably not your first language, your question is unclear. And the answer really is: Can the unit be STARTed from zero speed using the HMI? Is there some START-CHECK permissive that requires the unit to be on AC turning gear (at or near AC turning gear speed) in order to be able to initiate a START (without forcing something)? Has the unit ever been STARTed from zero speed (warm or cold) using the HMI? If so, then the DC turning gear wouldn't be required, it would seem. Again, most often the recommendation is to put the unit on turning gear for some short period of time before initiating a START to try to reduce any bow in the axial compressor rotor section to reduce the likelihood of high vibration during STARTing. Personally, I have never seen a Frame 9E unit that had to be on turning gear (above zero speed) to be STARTed. BUT, again: GE Belfort does some ... unusual things, they do them just because they can. So, if you don't know the answer to this question it probably can be found by looking in the programming of the Mark*.

Or maybe even--an amazing possibility, actually!--it might be explained in the Operations & Maintenance Manual, perhaps in the Starting Means System Descripton tab!

If you know the answers to the questions I have asked, please write back to let us (and others who are reading this thread, and others who will in the future) know.

Blessed day!
 
Hi CSA, I'm fairly familiar with this system. It has a large AC Starting motor (Maybe 800-1000 HP 5-10Kv) and a small turning gear motor through a small gearbox that will be used to rotate the shaft on cooldown, it will cut in before the shaft comes to rest and keeps the shaft rotating at a very low speed. From this it is pretty obvious that this small motor can not be used to start the turbine from rest.
I wish people would read and understand their P&ID's and read the Control Spec. before starting to guess and get into trouble
 
glenmorangie,

One of my main questions is: Can the unit be started from zero speed without being on turning gear (COOLDOWN)? Or, does it have to be on turning gear (presumably AC turning gear, because he says the RPM on AC turning gear is approximately 6 RPM)?

I know that when GE changed to air-cooled generators the increased weight of the generator rotor was a problem (particularly for units with the "slow-roll" COOLDOWN using the torque converter and Aux. L.O. Pump discharge pressure). I don't know if the starting means motor had any difficulty breaking the shaft away from zero speed without an assist from the torque converter when they changed to air-cooled generators, but I seem to recall it wasn't a problem without the ratchet to break the unit away from zero speed--only on cooldown, so a hydraulic ratchet was added, and in GE Belfort's case, because they ALWAYS have a better idea, they switched to a turning gear....

So, if you know the answer to the above question, I would be much obliged!

Thanks!!!
 
I don't think it is an AC Turning Motor it is an AC Starting Motor which should have the HP capability to Crank the machine itself to Firing Speed and on up.
Can MOB please look for a Control Spec. to help or go look at the nameplate data for the Starter.
 
Awaiting inputs from CSA
CSA questioning glenmorangie to allow idiots to start a turbine without a proper AC turning gear motor that allows the proper cooldown sequence after turbine is shutdown.

My answer is SURE start it. The cranking motor protection relay may need to have the protection settings changed. GO FOR IT.

All this from the question of a poster that only wanted to know if the cranking motor can start the thing from near zero speed.

Is this a trick question??????????????
 
Curious_One,

Ehhhh, ..., Uhhhh, ...., The question was--yet again--from a person who believes that EVERY GE-design Frame 9E 9E heavy duty gas turbine is like EVERY OTHER GE-design Frame 9E heavy duty gas turbine. Yes; they all suck and squeeze and burn and blow--but the auxiliaries can be VERY different and most people, especially those with little experience, DO NOT seem to understand that.

But, PLEASE, remember: We all have to (and had to) start somewhere. Am I tired of the non-stop number of questions about Droop Speed Control? You bet! Could I end it very quickly with a white paper or a wiki or by editing the wikipedia article that perjured from Control.com? Sure. Do I have the time? No. Do I have the editors and proof-readers to make it a solid piece of writing which could stand the test of time? No. (But I'm working on it; trust me.)

Anyway, MOB, the original poster, could do a MUCH better job of presenting supporting documentation--like a P&ID for the Starting Means system. Not everyone has access to a scanner and can scan and attach a .pdf file to a post without some help.

But, insulting people who are trying to build their knowledge and experience? People who, while they may be trying to settle a control room bet or dispute--are still trying to find the correct answer to their question, however poorly formed or supported.

What can we do? What we shouldn't be doing is insulting them. I always begin every class I teach with, "There is no such thing as a dumb question. Just a dumb answer. There may be a poor time to ask a particular question, or a poor setting, but every question is a valuable one." If the person who was my unofficial mentor when I was just getting started in Mark* turbine controls and GE-design heavy duty gas turbines thought of my questions as dumb questions--I never knew it. He patiently took the time to have me follow him around the unit and answer my questions by showing the devices and the compartments and the equipment. He didn't know a darn thing about Mark IV--but he knew EVERYTHING about GE-design Frame 5 heavy duty gas turbines and auxiliaries, and both gas fuel and diesel fuel and Mark I and Mark II. I knew how to spell Mark IV, and that was about it. He taught me to read Piping Schematics and P&IDs, and Device Summaries, and Generator Control Elementaries, and Parts Lists. And all patiently, and while listening to more than a few "dumb questions." I am eternally grateful to that man, and that's one of the reasons I do this--to try to repay his kindness and support and friendship. I wouldn't be where I am without him, and I try--though sometimes I fail--to honor his memory and treat every question as though it was well-formed and appropriately timed.

Please, keep the insults to a minimum. If you want a forum with ONLY experienced people, this isn't it. (And I don't know where you'll find it, either.)

Thanks for your support.

Blessed day.
 
CAN IT, OR CAN'T IT, BE STARTED FROM ZERO SPEED? THAT IS THE QUESTION WHICH ANSWERS THE ORIGINAL POSTER'S (UNASKED BUT CRITICAL) QUESTION.

Yes or no. It can or it can't. If it can't, then can it only be started at 6 RPM when the AC turning gear motor is running? And, if it can't be started from the DC turning gear motor (when the shaft IS spinning, just not very fast), why can't it? Would the Starting Means P&ID answer that question? Is it something to do with the DC turning gear engagement mechanism? Why isn't it the same as the AC turning gear mechanism's engagement mechanism? OHHH--I'm forgetting, this is a GE Belfort unit, isn't it???? That explains a lot.

And nothing at the same time.

The original poster mentioned two (2) turning gear motors--which would be typical of GE Belfort. One AC, that turned the shaft at 6 RPM, and one DC, that turned the shaft at 0.25 RPM. Neither of those sound like the AC high-horsepower starting motor.

Does the AC high horsepower starting motor spin the shaft at six RPM during cooldown? Or is that a separate 440 VAC turning gear motor and engagement mechanism?

And can the unit be started from zero speed--or does it have to be (must it be) on turning gear to start?

I have been to sites that INSIST the unit MUST BE on cooldown at least 4 hours before every START. And, then I tell them to START the unit with it at zero speed--and they FREAK OUT. But, guess what? It starts!!! If it's been sitting for several days, the vibrations are higher than normal. But the unit DOES NOT have to be on turning gear (cooldown) for any period of time before being STARTED. It's a RECOMMENDATION--NOT a START-CHECK permissive. If it's an emergency and the unit needs to be started as quickly as possible--it can be done. Might it trip on high vibration? It depends on how long it's been at zero speed. Can they run the unit on cooldown a couple of hours every day even if they don't start it to keep the rotor straight? Yes. (But, then I've been to sites who think the unit MUST BE on cooldown for some time before EVERY start--but they don't want to incur the electrical costs associated with running cooldown for an hour or two every day, and they can't always put the unit on cooldown before being called to star the unit.... And they want a solution for their problem--which is their problem: They don't want to pay for electrical costs associated with keeping the rotor straight when the unit doesn't run for days or weeks at a time.)

It's a crazy world. Either it can or it can't be started from zero speed. That would negate the need for EITHER turning gear motor to be running prior to a START. But, of course, the original poster didn't think to ask this question--because he and his colleagues and supervisors ALL BELIEVE the unit MUST BE on cooldown prior to EVERY start. And they haven't looked at the START-CHECK display to see if that's true or not. Or the sequencing/CSP/application code.
 
I apolgize to ANYONE or EVERYONE I might of offended.

My point was why would a EXPERT try to drag information out of another EXPERT than had “Tapped Out”.

My explanation of my obvious poor behavior is as follows:

With nearly four decades of experience in steam and gas turbine startups, shutdowns, outages, I have experienced many times that management has simply “willed” that a machine should start regardless of inpending disaster.

Going together not coming apart. Outage is over. Overbudget. The list could go on forever.

What do you need to force to start this machine say management ? NOT what will be the result of the FORCE if something goes wrong.

Starting a gas turbine with a known problem with the turning gear is a recipe for locked rotor.

The ANSWER is YES: The machine will start from zero speed. The question should be: SHOULD YOU.

In the future, I will refrain from posting on issues that raise my emotion level to the end of outage level from the past.
 
I apolgize to ANYONE or EVERYONE I might of offended.

My point was why would a EXPERT try to drag information out of another EXPERT than had “Tapped Out”.

My explanation of my obvious poor behavior is as follows:

With nearly four decades of experience in steam and gas turbine startups, shutdowns, outages, I have experienced many times that management has simply “willed” that a machine should start regardless of inpending disaster.

Going together not coming apart. Outage is over. Overbudget. The list could go on forever.

What do you need to force to start this machine say management ? NOT what will be the result of the FORCE if something goes wrong.

Starting a gas turbine with a known problem with the turning gear is a recipe for locked rotor.

The ANSWER is YES: The machine will start from zero speed. The question should be: SHOULD YOU.

In the future, I will refrain from posting on issues that raise my emotion level to the end of outage level from the past.
ps the small motor is your breakaway motor the other is for proper cooldown
 
Curious_One,

Thank you for the information! It is MUCH appreciated!!!

So, you're saying the DC turning gear motor is normally for the express purpose of assisting the AC high-horsepower starting motor and torque converter with breaking the turbine-generator shaft away from zero speed. So, the AC high-horsepower starting motor and torque converter--by themselves--are not enough to break the turbine-generator shaft away from zero speed during starting?

I am fully aware that a GE-design Frame 9E heavy duty gas turbine axial compressor is MUCH larger than a GE-design Frame 6B heavy duty gas turbine axial compressor rotor or a GE-design Frame 7EA heavy duty gas turbine axial compressor rotor--but BOTH those machines use ratchets, which only rotate the turbine-generator shaft approximately 45 degrees (1/8th of a turn) every three minutes--and that's enough to prevent a bowed rotor when shutdown or tripped from load when the axial compressor rotor (and turbine rotor) are hot. Would not a turning gear operating at 0.25 RPM be just as good at preventing a bowed rotor?

Or cannot the DC turning gear motor/mechanism be operated continuously for emergency cooldown purposes?

I have not seen nor experienced every version of GE-design heavy duty gas turbine and associated auxiliaries. And, GE Belfort are hell-bent on trying any and every perversion of tried and true auxiliaries--just because they can.

Anyway, let's talk about what we tell people when their ratchet mechanism or turning gear motor/mechanism (cooldown mechanism) fails--and they can't restore cooldown within 20-30 minutes? We tell them to keep the Aux. L.O. Pump running (to keep oil flowing to the bearings to keep them cool!), abort the cooldown (ratchet or turning gear or whatever) and wait. Wait at least 24 hours. It's HELL for most people--who have been told that the rotor MUST BE on cooldown or it will bow. But, it's the tried and true way for GE-design heavy duty gas turbines.

I only know of one GE-design heavy duty gas turbine rotor that was damaged when the cooldown mechanism failed and couldn't be restored. And that was a self-inflicted, USD 600,000.00 mistake (NOT counting the lost generation or the lost steam sales to the host facility next door). The Plant Manager was hell-bent on getting the rotor turned/turning. It had been shut down for about 2 hours, from a Base Load run of several hours, so the machine was well and hot. And, in that two hours the axial compressor rotor bowed and the compressor rotor blades came into contact with the compressor casing. Well, they kept trying to START the machine with the AC high-horsepower starting motor--but the rotor WOULD NOT turn.

Instead of just leaving the machine alone, with the Aux. L.O. Pump motor running, he sent some mechanics out to the Load Compartment, to remove the coupling guard and place a hydraulic bottle jack under one of the coupling bolt nuts and apply a LOT of pressure (30 tons if I recall correctly). Then they initiated a START with the AC high-horsepower starting motor--and guess what--the rotor turned. For about 20 seconds, then it froze up again. And it made a horrible noise when it stopped turning. And, still they kept trying to turn the rotor.... But, it wouldn't turn.

A borescope the next morning revealed that the compressor from about the fifth stage to about the 14th stage was destroyed. One of the compressor blades which had been in contact with the compressor casing had liberated (broken off) and destroyed several downstream stages. Three months and USD600,000.00 later the unit was restored to service. (This happened in the 1980s, so things weren't quite as expensive as they are today.)

I have encountered COUNTLESS GE-design heavy duty gas turbines that have had cooldown problems--and not a one of them EVER required repair or replacement (except the one described above). They bow, and because the metal is only in the elastic range of its capability once it starts to cool it starts to straighten. Does it ever return to fully straight by itself? No. But, with cooldown (once restored), and CRANKing, and FIREing the shaft WILL return to straight and can be used reliably for MANY more years.

Is it the worst thing if a GE-design heavy duty gas turbine can't be put on or kept on cooldown for the proper length of time? NO. All it requires is patience, and the knowledge that with time and cooldown and cranking and firing all things will be fine. UNLESS one tries to force the issue with a hydraulic jack; it will turn, but the results will be catastrophic. And costly.

Do I condone starting a machine without a working cooldown mechanism/system? No. Could I use the DC turning gear motor in an emergency if necessary? Sure--with some logic forcing--and some luck. (One of my favorite sayings has been (for decades), "I'd rather be lucky than good!" Another one is, "The harder I work the luckier I get." Put the two together, and, it's a recipe for success.)

Again, MANY sincere thanks for the information! I would LOVE to see the Starting Means P&ID AND the Starting Means System Description for that unit. But, alas. It is not to be.

But from your description, the unit CAN be started from "zero speed"--because if the DC turning gear motor is to be used to break the shaft away from "zero speed" (0.25 RPM) and it's working, then the unit can be started. If the AC turning gear motor/mechanism isn't working, should it be started? That's what Managers get paid the BIG BUCKS to decide. At that point, it's the "science" of Risk Management that comes into play. And, that' what Plant Managers are paid handsomely to do: Manage risk. (Of course I jest when I call Risk Management a science; it's really just a throw of the dice. But all risks come with rewards, and possible consequences. Risk Management is about understanding which is more valuable for the given conditions/situation.

And, we are just the technicians/engineers who advise--and perform as told.
 
On a 7EA with a BRUSH generator with 2 generator lift oil switches set to 450 psi according to device list are not required to start the turbine.

Just try to start one without the lift oil permissive.

I agree with you on your observations and experience. Yet, as a EXPERT, which your are. I cannot agree with you to start/stop anything without TOTAL knowledge of the CSP, PID drawings, etc.

I totally understand Risk Management. Understanding is not agreement.

Like glenmorangie, I prefer to "Tap Out". The original poster will disappear without a trace and you and I will be left without answers.

Tomorrow will be a glorious day. I hope.
 
Curious_One,

I worked with a man many years ago who had a VERY difficult time turning over operation to the operators at a plant. (I actually did more than one commissioning with him.) He just had no confidence that they knew how to operate the unit--and we all know that's the case at most new power plants. Hell, experienced operators melt away into the woodwork when a controls retrofit/upgrade is done--they think START doesn't mean START, and AUTO doesn't mean AUTO, and RAISE- or LOWER SPEED/LOAD don't do the same thing they did before. And, they don't want to be told what to do--but they're afraid to do what they've done before, too. It's almost comical.

If you think one has to know EVERY bit of code and logic before starting a machine, no one should be operating a machine. No one.

As engineers/technicians, especially engineers/technicians that have the responsibility to commission new turbine-generators which are under warranty by the OEM, we are probably more frightened than anyone about proper operation (well most, anyway; not all, but that's a different thread...!).

Yeah, I should have said if the unit is under manufacturer's warranty or an LTSA you should be asking this question of the warrantor or the LTSA provider. And, maybe the reason the question (poorly worded as it was) was meant to get a "second opinion" because there was some clarification required or needed.

If you tap out--no tap backs!

I have my answer. Right or wrong, I have it. I have formulated my own answer without the benefit of seeing the programming for the Mark* or the P&ID for the Starting Means system. It may be right, or it may be wrong. But it was based on the information provided by the original poster (scarce as it was), and our exchanges, Curious_One. The original poster (if he's even still following this thread) can use my answer as he sees fit, or not.

Operators, and Operations Supervisors, and Plant Managers, and Plant Engineers should be capable of looking at the START-CHECK permissive display and referring to the P&IDs and the System Descriptions in the Operations & Maintenance Manuals and making some informed decisions. We won't know what the original poster's duties or responsibilities are, or even what prompted the question. Without more information, there's nothing more can be done.

Blessed day.
 
How about helping out here, ControlsGuy25? You've all the GE Belfort experience and contacts.
Hi All,

Yes CSA I am also familiar with GE Belfort equipments/controls philosophy...
The thing is that I am on well desserved vacations at the moments...
Will try to add/give support at least in two days when I will be back to home /work hopefully.

Stay blessed..
Cheers.
Controls Guy25.
 
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