Ratchting motor 88HR overloaded

Dear All;


Our GE Gas Turbine frame 5 stopped and ratcheting mechanism was initiated normally, 01 Hours after, we got alarm ratchet trouble due to ratcheting pump not cutting off after time that should be off, other alarm hydraulic ratchet motor overload alarm (L49HR_ALM) initiated from MCC to MARR VIe Control system.


Alarms ratchet trouble (L30HRX-ALM) and hydraulic ratchet motor overload (L49HR_ALM) were persisting for more than 2 Hours and protection relay not breaking the circuit to stop the motor when an electrical overload happen and per consequence burn out the switch in a relay.

After checking electric circuit for ratcheting motor 88 HR, I didn't find any logic to stop the motor when overloading occurred.

My question is, why overload protection for 88HR is not there and on the other motors like 88QA, 88HQ the overload protection is there.

Similar for DC lube oil emergency motor 88QE, no protection in case of overload.

Regards
 

Attachments

Dear All;


Our GE Gas Turbine frame 5 stopped and ratcheting mechanism was initiated normally, 01 Hours after, we got alarm ratchet trouble due to ratcheting pump not cutting off after time that should be off, other alarm hydraulic ratchet motor overload alarm (L49HR_ALM) initiated from MCC to MARR VIe Control system.


Alarms ratchet trouble (L30HRX-ALM) and hydraulic ratchet motor overload (L49HR_ALM) were persisting for more than 2 Hours and protection relay not breaking the circuit to stop the motor when an electrical overload happen and per consequence burn out the switch in a relay.

After checking electric circuit for ratcheting motor 88 HR, I didn't find any logic to stop the motor when overloading occurred.

My question is, why overload protection for 88HR is not there and on the other motors like 88QA, 88HQ the overload protection is there.

Similar for DC lube oil emergency motor 88QE, no protection in case of overload.

Regards
Hello

Whitout to be able to check your MCC drawings & Mark6e app code /program that will be difficult to give you some answer..

Do you mean that protection relay did not worked properly to get the Motor/pump 88HR in safe position...


James
 
Hello

Whitout to be able to check your MCC drawings & Mark6e app code /program that will be difficult to give you some answer..

Do you mean that protection relay did not worked properly to get the Motor/pump 88HR in safe position...


James
Dear James;

My concern is . Why the ratcheting and Emergency lube oil motors 88HR and 88 QE not stopped by contactor relays when are overloaded .
Why electric circuits of 88HQ and 88QE are not equipped with overload contactor to stop in case of overload.
on the other hands, other auxiliaries motors like 88QA, 88HQ, 88BA... are equipped with contractors to stop the motors in case of overload.

Regards
 
Dear James;

My concern is . Why the ratcheting and Emergency lube oil motors 88HR and 88 QE not stopped by contactor relays when are overloaded .
Why electric circuits of 88HQ and 88QE are not equipped with overload contactor to stop in case of overload.
on the other hands, other auxiliaries motors like 88QA, 88HQ, 88BA... are equipped with contractors to stop the motors in case of overload.

Regards
Dear Djafer ,

Thank you for your replying...
Yes i understood your concern as you mentionned it on the first post...

88HR you mean in the first statement ( plz reread the line...)

Again I would look on schematic drawing and O&M manuals from GE to get the answer...
 
88HR is equipped with DC motor , protection controls on overload would be slightly different than AC motor protection philosophy ..

You can share schematic here then we can have better overview and add notes/comments to support you!
 
Djafer-QP,

We don’t know how old your GE-design Frame 5 heavy duty gas turbine is, only that it has a Mark VIe turbine control system. We also don’t know if your unit was packaged and sold by GE or by one of its licensed packagers (BHEL; John Brown; Nuovo Pignone; etc.).

In general, GE heavy duty gas turbine controls philosophy, especially for legacy units with an Accessory Gear drive, is to only alarm on electric motor (AC or DC) overload—not to trip the electric motor. The alarm alerts a conscious, trained operator to a motor overload which needs a quick investigation and resolution in order to prevent damage to the electric motor or worse, to the turbine and/or generator or auxiliaries. If the problem is serious, the operator can decide the course of action which might include shutting the unit down or tripping it. If the power being produced by the unit is critical at that time, then the operator can decide to let the motor burn up to keep producing power. (In the early days of GE heavy duty gas turbine production, there were very few electric motors required for normal running operation because the Accessory Gear drove the Main L.O. Pump and the Main Hydraulic Pump and the Cooling Water Pump and even the Cooling Water Fans!) And the DC L.O. Pump was considered to be critical but also “sacrificial” as a last means of protecting the unit bearings.

The Hydraulic Ratchet pump motor was also considered to be critical and sacrificial—and, again, the decision to stop the ratchet pump was left to the trained operator to determine if it was absolutely necessary to try to keep the ratchet working or open the motor’s main DC breaker to save the motor. (Yes—the ratchet is important, but if the rotor is hot or warm and it can’t be turned after a period of approximately 20-30 minutes then the ratchet should be stopped anyway, but the Auxiliary L.O. Pump should be kept running to supply L.O. to the bearings to cool them while waiting for the rotor to cool before re-starting the ratchet mechanism.)

Over decades GE has used more and more electric motors and relied less and less on the Accessory Gear drive, but the philosophy of only alarming on an electric motor overload and letting the operator investigate and decide if the motor should be stopped hasn’t changed much. The “problem” is that many people believe that whenever an electric motor overload occurs on any process or application the motor should automatically be stopped and they believe that should also be the same for electric power generation equipment as well. The cost of an electric motor might be nothing compared to what might happen if the power being produced is suddenly lost (think of people with ventilators keeping them breathing, or getting stuck between floors on an elevator or unable to use a bridge raised to allow ship traffic to pass that can’t be lowered without electricity).

Some purchasers of GE-design heavy duty gas turbines have demanded that electric motors be automatically stopped on overload. Some packagers of GE-design heavy duty gas turbines have decided to automatically shut down some, or even all, electric motors on overload. When there is a redundant motor/pump available it can automatically be started—but what if there isn’t a redundant motor/pump?

It’s all a matter of philosophy, and, really that involves operator (and operations supervisor and maintenance personnel and their supervisors and plant management and ownership!!!) training and understanding, as well. The operator should be capable of investigating and deciding the course of action given the operating circumstances and situation. That’s how the unit is most reliable. If the turbine control system, without a LOT of information it can’t process, makes the decision to shut the motor down then that can have very serious immediate and knock-on consequences. If power is critical, the cost of a motor or a relay (did you really mean contractor??) is nothing in the bigger picture. Damaged bearings—that’s a huge deal. But do you want the motor starter relay logic deciding to shut the motor down and possibly damaging the unit bearings when there wasn’t really an overload, just a loose connection???

Okay, so the relay/contactor was damaged or destroyed. Things like that are going to happen on occasion. Is the underlying problem the lack of spare parts, or the lack of training, or the lack of maintenance? What caused the overload—a damaged pump? What damaged the pump?

People want to rely on automation (the control “system”) to protect equipment under every condition and still be reliable all the time. (That’s what the sales people say the automated control system can do, right??!?!!) But the technology just isn’t really that “smart” yet (no matter what the sales people say or the marketing people write). We still need people. When the turbine control system can do everything, where will we people find work?

Tell us why the overload condition occurred. Tell us if the site had the spare part(s) to repair or replace the failed relay/contactor. (It would be great if you posted a picture of the failed part.)

A power plant can’t be reliably operated without people (though there’s at least one OEM who thinks autonomous power plants are coming soon!). People need to be trained and understand the equipment they are operating. It would be great if GE documented their heavy duty gas turbine control philosophy, also, but they didn’t and probably never will. But, thinking, reasoning experienced people (often more than one, working as a team...) should be able to discern these kinds of things based on training, familiarization, knowledge and experience.

All things a motor starter or even a digital control system can’t do—and won’t be able to do for at least another decade or two. Thinking, reasoning, rational human beings have to be involved in a reliable power plant.

Hope the helps.
 
Djafer-QP,

As ConrolsGuy25 said we would need to see the motor starter schematic for 88QA and 88HQ and 88BA to be sure. OR, perhaps whoever provided the package or the control system upgrade, modified the application code in the Mark VIe to stop some AC electric motors when an overload for that particular motor was detected. There are a couple of ways motors could be stopped in the event of an overload, but, it's probably not going to be the case that DC electric motors will be stopped automatically.

It would really be helpful to many people if you would post a picture of the failed "relay" (I suspect it's actually a contactor, which is a "high-current" relay of sorts). AND, it would also be helpful if you could tell us what caused the overload condition. It might have even been failed contacts of the "relay" (contactor??) which were welded closed and wouldn't allow them to be opened--and that often occurs when the contacts have not been checked/replaced periodically as they should be.... Or, maybe the mechanism bound up mechanically, or an arc chute came apart (another component of a contactor that should be inspected and replaced as necessary).

Again, GE has several decades (approximately seven (7)) of building and configuring and protecting heavy duty gas turbines. They are all about reliability--that's the name of the game. Is there going to be a condition, or three, they can't anticipate (such as lack of maintenance, or a worn/failed pump or coupling or ???) that wasn't anticipated? Sure; yes. But, knowledgeable, conscious operators trained and experienced to respond to alarms in a proper manner and time will be able to protect against many failures--but not all. And, just because other manufacturers shut down electric motors when an overload occurs doesn't mean every manufacturer has to. Remember: GE has to warrant these machines for at least the first year of operation after commissioning. They also want to keep selling machines--and if their machines are deemed unreliable, they ain't gonna sell too many of them.

GE machines are really remarkably resilient and robust--and I'm speaking particularly of the Frame 5s, and Frame 6Bs and Frame 7B/E-class machines (not so much the F-class machines). Especially Frame 5s--there are literally thousands of them in operation around the world, some for nearly seven (7) decades! Some with the original Fuel Regulator turbine control systems (which had VERY LITTLE analog electronics, and huge rows of electro-mechanical relays. And a part of that is because of the turbine control systems and the controls philosophies used to control and protect them. BUT, the control systems and controls philosophies can't protect against every eventuality. But, their philosophy of alarming-only on electric motor overload has contributed to their record of reliability.

Think about your Frame 5 (if it has an Accessory Gear drive). It has an AC Auxiliary L.O. Pump, and it seems yours is new enough it also has an AC Auxiliary Hydraulic Pump. It also has Accessory Gear-driven L.O. and Hydraulic Pumps. When the unit is starting, it uses the AC motor-drive pumps to get it started spinning and even all the way up to approximately 95% speed. After that, it runs on the Accessory Gear-driven pumps. Let's say you NEED to start that unit--the power is critically necessary. And, during starting the AC motor-driven Aux. L.O. Pump develops an overload. Do you want that pump to automatically stop? Especially if the unit is still at zero speed, or is at low speed? That might prevent the unit from starting. If the contactor burns up, or the motor, even, burns up--if the unit gets to a speed that the Accessory Gear-driven pumps can supply the pressure and flow necessary to get the unit synchronized and keep it running to produce that critical and necessary power--isn't that a reasonable trade-off? So, if the operator is alerted to an overload by an alarm, and is allowed to decide what action to take then it's possible that even if the motor is damaged or destroyed the unit will still start and that power that is so critical and necessary will be available to those who need it.

Or, let's say during starting at zero speed or low speed a wire comes loose causing the "appearance" of an Aux L.O. Pump motor overload and that causes the motor to be stopped and the unit NOT to get on-line and produce power. Is that "reliable"?

These kinds of things have all been considered and taken into account when configuring and programming the machine. If a small manufacturing plant has a conveyor mechanism driven by an AC motor and that conveyor mechanism jams and the motor overloads and is damaged or destroyed, the loss of that motor--economically--might be very large for the company. The cost of the motor might be high enough the company hadn't purchased a spare. So, shutting the motor down automatically on overload might save the company a LOT of money and production, too. A 25 MW turbine-generator is not the same thing. It shouldn't be considered or treated as the same thing. A motor is small potatoes; a "relay" (contactor??) is even less costly (probably). It's all relative. And, it's NOT all the same.

I, for one, am EXTREMLY interested to know the details of this failure. It can be a very good lesson for many--maybe even myself. I'm making some presumptions, because you didn't supply many details (and may have used an incorrect term for the failed part). But, the answer to your question is still the same: The typical GE heavy duty gas turbine controls philosophy is NOT to automatically shut off critical pump motors when an overload is detected. That decision is left to the operator to investigate and take appropriate action for the situation and circumstances at that time. Maybe the power being produced by that unit isn't absolutely necessary and critical at that moment--but maybe it is. The turbine control system can't know that--only an operator (and/or his/her supervisor) can--and can use that information to form the decision about the course of action to be taken. Sometimes, things happen very quickly (it doesn't seem to in this case--but we don't have a LOT of information).

It's possible to please some of people all the time, but it's not possible to please all of the people all the time. GE's heavy duty gas turbine control philosophies are designed to make the units as reliable as possible under the widest range of conditions. But that doesn't mean every possible condition.

Again, I hope this helps.
 
Dear James;

My concern is . Why the ratcheting and Emergency lube oil motors 88HR and 88 QE not stopped by contactor relays when are overloaded .
Why electric circuits of 88HQ and 88QE are not equipped with overload contactor to stop in case of overload.
on the other hands, other auxiliaries motors like 88QA, 88HQ, 88BA... are equipped with contractors to stop the motors in case of overload.

Regards
Dear Djafer,


Is there kind of ground fault or unbalanced suppply power on the 125VDC bus ...since the screenshots that you shared showing Battery 125VDC Ground Fault alarm & DC POWER SUPPLY Undervoltage
....
 
Djafer-QP,

As ConrolsGuy25 said we would need to see the motor starter schematic for 88QA and 88HQ and 88BA to be sure. OR, perhaps whoever provided the package or the control system upgrade, modified the application code in the Mark VIe to stop some AC electric motors when an overload for that particular motor was detected. There are a couple of ways motors could be stopped in the event of an overload, but, it's probably not going to be the case that DC electric motors will be stopped automatically.

It would really be helpful to many people if you would post a picture of the failed "relay" (I suspect it's actually a contactor, which is a "high-current" relay of sorts). AND, it would also be helpful if you could tell us what caused the overload condition. It might have even been failed contacts of the "relay" (contactor??) which were welded closed and wouldn't allow them to be opened--and that often occurs when the contacts have not been checked/replaced periodically as they should be.... Or, maybe the mechanism bound up mechanically, or an arc chute came apart (another component of a contactor that should be inspected and replaced as necessary).

Again, GE has several decades (approximately seven (7)) of building and configuring and protecting heavy duty gas turbines. They are all about reliability--that's the name of the game. Is there going to be a condition, or three, they can't anticipate (such as lack of maintenance, or a worn/failed pump or coupling or ???) that wasn't anticipated? Sure; yes. But, knowledgeable, conscious operators trained and experienced to respond to alarms in a proper manner and time will be able to protect against many failures--but not all. And, just because other manufacturers shut down electric motors when an overload occurs doesn't mean every manufacturer has to. Remember: GE has to warrant these machines for at least the first year of operation after commissioning. They also want to keep selling machines--and if their machines are deemed unreliable, they ain't gonna sell too many of them.

GE machines are really remarkably resilient and robust--and I'm speaking particularly of the Frame 5s, and Frame 6Bs and Frame 7B/E-class machines (not so much the F-class machines). Especially Frame 5s--there are literally thousands of them in operation around the world, some for nearly seven (7) decades! Some with the original Fuel Regulator turbine control systems (which had VERY LITTLE analog electronics, and huge rows of electro-mechanical relays. And a part of that is because of the turbine control systems and the controls philosophies used to control and protect them. BUT, the control systems and controls philosophies can't protect against every eventuality. But, their philosophy of alarming-only on electric motor overload has contributed to their record of reliability.

Think about your Frame 5 (if it has an Accessory Gear drive). It has an AC Auxiliary L.O. Pump, and it seems yours is new enough it also has an AC Auxiliary Hydraulic Pump. It also has Accessory Gear-driven L.O. and Hydraulic Pumps. When the unit is starting, it uses the AC motor-drive pumps to get it started spinning and even all the way up to approximately 95% speed. After that, it runs on the Accessory Gear-driven pumps. Let's say you NEED to start that unit--the power is critically necessary. And, during starting the AC motor-driven Aux. L.O. Pump develops an overload. Do you want that pump to automatically stop? Especially if the unit is still at zero speed, or is at low speed? That might prevent the unit from starting. If the contactor burns up, or the motor, even, burns up--if the unit gets to a speed that the Accessory Gear-driven pumps can supply the pressure and flow necessary to get the unit synchronized and keep it running to produce that critical and necessary power--isn't that a reasonable trade-off? So, if the operator is alerted to an overload by an alarm, and is allowed to decide what action to take then it's possible that even if the motor is damaged or destroyed the unit will still start and that power that is so critical and necessary will be available to those who need it.

Or, let's say during starting at zero speed or low speed a wire comes loose causing the "appearance" of an Aux L.O. Pump motor overload and that causes the motor to be stopped and the unit NOT to get on-line and produce power. Is that "reliable"?

These kinds of things have all been considered and taken into account when configuring and programming the machine. If a small manufacturing plant has a conveyor mechanism driven by an AC motor and that conveyor mechanism jams and the motor overloads and is damaged or destroyed, the loss of that motor--economically--might be very large for the company. The cost of the motor might be high enough the company hadn't purchased a spare. So, shutting the motor down automatically on overload might save the company a LOT of money and production, too. A 25 MW turbine-generator is not the same thing. It shouldn't be considered or treated as the same thing. A motor is small potatoes; a "relay" (contactor??) is even less costly (probably). It's all relative. And, it's NOT all the same.

I, for one, am EXTREMLY interested to know the details of this failure. It can be a very good lesson for many--maybe even myself. I'm making some presumptions, because you didn't supply many details (and may have used an incorrect term for the failed part). But, the answer to your question is still the same: The typical GE heavy duty gas turbine controls philosophy is NOT to automatically shut off critical pump motors when an overload is detected. That decision is left to the operator to investigate and take appropriate action for the situation and circumstances at that time. Maybe the power being produced by that unit isn't absolutely necessary and critical at that moment--but maybe it is. The turbine control system can't know that--only an operator (and/or his/her supervisor) can--and can use that information to form the decision about the course of action to be taken. Sometimes, things happen very quickly (it doesn't seem to in this case--but we don't have a LOT of information).

It's possible to please some of people all the time, but it's not possible to please all of the people all the time. GE's heavy duty gas turbine control philosophies are designed to make the units as reliable as possible under the widest range of conditions. But that doesn't mean every possible condition.

Again, I hope this helps.
Many thanks CSA and ConrolsGuy25

This is happen to GE frame 5, compressor driver. the system was upgraded from MARK V to Mark Vie on 2015.

The detail why 88HR overloaded will be shared with you soon.

Below snap shots from the schematics, the first one is similar for both Ratchet pump and Emergency lube oil pump denotes it has only command contacts in auto mode to stop the motor and no over load relay contact in series. Where as in the second one below, for Auxilliary lube oil pump relay contact KF is in series with contactor coil.



1615056503741.png












Contactor circuit for Aux . lube oil pump :
1615056644882.png
 

Attachments

Thanks for sharing this schematic...

Even it is bit difficult to get a clear reading...WHERE this K4 "overload contacts " "not sure of the number/tag 4 as it is hard to read " come from ...
 
CSA has done his best to explain control Philosophy== is the study of general and fundamental questions .

GE is "burn it down" to save the turbine. Alarm and warn operator of adverse conditions and allow operator to correct adverse condition.

A motor overload condition can mean many things. If one has knowledge of 3 phase motors and motor starters, one would know that a "heater" as I call it can fail over time. The "heater" is a thermal coil that monitors current and can trip the overload circuit.

I have witnessed overload alarms and investigated the alarm to find a single phase of the "heater" burned/open.

Since your alarm is oil related, I will share. Aux LO pump overload...still on ratchet....need cooldown.
Investigation: find Aux LO pump still operating yet on only 2 phases.
Go find parts because if I shut of Aux LO pump will not restart on 2 phases.
Parts found. Start Emergency LO pump and shutdown Aux LO pump and replace part.
Start Aux LO pump and stop Emergency LO pump.

Pat self on back.
 
Thanks for sharing this schematic...

Even it is bit difficult to get a clear reading...WHERE this K4 "overload contacts " "not sure of the number/tag 4 as it is hard to read " come from ...
Dear ControlGuy25.
What's GE default for DC motors (88HR & 88QE) overload. should be equipped with overload protection contactor to stop the motors in case of overload.

Regards
 
Dear ControlGuy25.
What's GE default for DC motors (88HR & 88QE) overload. should be equipped with overload protection contactor to stop the motors in case of overload.

Regards
Dear Djafer,

You at least did not repsond to my question about 125V DC BUS Ground fault....

According to my colleague yes there should be protection to stop 88HR motor pump in case of overload.

Now We do not know the Supplier /vendor who packaged this unit...

At GEEPE for a frame 6B my colleague(a Power plant shift engineer) just confirmed me that there is kind of protection on their unit ...

Plz Give us reponses to our questions so we can give better advises...

Regards,
James
 
I confirm that there is thermal overload relay in the control/protection circuit of the 88HR

This RELAY tag is 49HR1

Now again we still do not know if teh packager of this unit or engineering team did not add this in your 88HR circuit diagram....

Thanks for your reply

James
 
I confirm that there is thermal overload relay in the control/protection circuit of the 88HR

This RELAY tag is 49HR1

Now again we still do not know if teh packager of this unit or engineering team did not add this in your 88HR circuit diagram....

Thanks for your reply

James
Dear James;

As per electrical team, unit commissioned 10 years before and no body know why the did not add this protection in circuit diagram.

Overload protection for Motor AC/DC is depend of what they agreed during engineering / Commissioning of gas turbines.

As per CSA :

In general, GE heavy duty gas turbine controls philosophy, especially for legacy units with an Accessory Gear drive, is to only alarm on electric motor DC overload not to trip the electric motor. The alarm alerts a conscious, operator to a motor overload which needs a quick investigation and resolution in order to prevent damage to the electric motor. If the problem is serious, the operator can decide the course of action which might include shutting the unit down or tripping it, then the operator can decide to let the motor burn up to keep gas production process on line.

The Hydraulic Ratchet pump motor was also considered as critical and sacrificial, the decision to stop the ratchet pump was left to the operator to determine if it was absolutely necessary to try to keep the ratchet working or open the motor’s main DC breaker to save the motor. The ratchet is important, but if the rotor is hot or warm and it can’t be turned after a period of approximately 20-30 minutes then the ratchet should be stopped anyway, but the Auxiliary L.O. Pump should be kept running to supply L.O. to the bearings to cool them while waiting for the rotor to cool before re-starting the ratchet mechanism.

the philosophy of only alarming on an electric motor overload and letting the operator investigate and decide if the motor should be stopped or no.
 
Dear Djafer,

Thank you for your statements...

Again you still did not respond on 125VDC ground fault....okay no problem ....i

I also do not know the reason why they did not add this protection on that mentionned Motor...

Will post here some schematics from GEEPE where you will find that the 49 protection is implemented on 88HR...

James
 
Djafer,

As i Asked you before...

Can you just reply on that DC ground fault ...is it real or o not ( intempestive alarms)...

So we can speak same language..

Regards,
James
 
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