We have frame 5 gas turbine during the shut down the rachet system does not rotate the rotor at standstill but after period about 4 hours when the wheel space temp come down the rachet starts rotating the rotor smoothly

 

When the issue/problem started if so ??

What is programmed on app code for this unit?

 

When the issue/problem started if so ??

What is programmed on app code for this unit?

After install referbished thermal block and mentain the all systems

 

@AhmedSaeed2332,

What turbine control system is used on the GE-design Frame 5 heavy duty gas turbine?

How old is the machine?

USUALLY, for most GE-design Frame 5 and 6B heavy duty gas turbines a failure to rotate the shaft after reaching zero speed results in the turbine control system (if it's a GE Mark* turbine control system) continuously trying to rotate the shaft (without success). There is usually some kind of Process Alarm to indicate a failure to reach or return to some ratchet self-sequencer position (end of forward stroke or end of retraction stroke). What Cooldown-related Process Alarms are annunciated and active during the period when the ratchet mechanism can't rotate the shaft?

As ControlsGuy25 asked, when did this problem start? After a maintenance outage? After a trip from load? How long has this problem existed/persisted?

What has been done at site to troubleshoot and resolve the problem?

Are the Turbine Compartment doors closed when the unit is at zero speed? (IF the Turbine Compartment doors are NOT closed and remain closed (except for quick visual inspections) when the machine reaches zero and attempts to rotate the machine shaft the turbine shell (and even the axial compressor casing!) will cool faster than the internal components and cause a "rub" which the forces of the ratchet mechanism can't overcome (even when the ratchet filter and pump are clean and in good working order).

Is the Turbine Compartment vent fan running when the unit reaches zero speed and attempts to rotate the machine shaft?

Have you visually verified the jaw clutch is closed when the machine reaches zero speed and attempts to rotate the machine shaft? [NOTE: All of my comments in this post refer to a GE-design machine with a hydraulic self-sequencer, a small metal block which monitors and controls the flow of high-pressure oil to the ratchet pistons (and to the jaw clutch closing cylinders for machines equipped with a jaw clutch). There many older Frame 5s which did not use a self-sequencer and operate slightly differently from a mechanical standpoint.]

When was the last time the filter of the hydraulic ratchet system was changed? There usually ISN'T a differential pressure gauge or switch on the filter to alert operators/technicians the filter is dirty and needs to be changed so it's often overlooked. ALSO, there usually isn't a pressure gauge on the discharge of the Hydraulic Ratchet Pump to indicate the pump pressure. (Both of these gauges are good to add during the next maintenance outage--and add them to the rounds list the outside operators make when the machine is on Cooldown to monitor differential pressure and pump discharge pressure).

 

After install referbished thermal block and mentain the all systems

This unit with capacity 20 mw and now is running.The problem is during the stopping.

 

How many times has this problem occured on shutdown--and how soon after this problem was the machine re-started?

 

@AhmedSaeed2332,

What turbine control system is used on the GE-design Frame 5 heavy duty gas turbine?

How old is the machine?

USUALLY, for most GE-design Frame 5 and 6B heavy duty gas turbines a failure to rotate the shaft after reaching zero speed results in the turbine control system (if it's a GE Mark* turbine control system) continuously trying to rotate the shaft (without success). There is usually some kind of Process Alarm to indicate a failure to reach or return to some ratchet self-sequencer position (end of forward stroke or end of retraction stroke). What Cooldown-related Process Alarms are annunciated and active during the period when the ratchet mechanism can't rotate the shaft?

As ControlsGuy25 asked, when did this problem start? After a maintenance outage? After a trip from load? How long has this problem existed/persisted?

What has been done at site to troubleshoot and resolve the problem?

Are the Turbine Compartment doors closed when the unit is at zero speed? (IF the Turbine Compartment doors are NOT closed and remain closed (except for quick visual inspections) when the machine reaches zero and attempts to rotate the machine shaft the turbine shell (and even the axial compressor casing!) will cool faster than the internal components and cause a "rub" which the forces of the ratchet mechanism can't overcome (even when the ratchet filter and pump are clean and in good working order).

Is the Turbine Compartment vent fan running when the unit reaches zero speed and attempts to rotate the machine shaft?

Have you visually verified the jaw clutch is closed when the machine reaches zero speed and attempts to rotate the machine shaft? [NOTE: All of my comments in this post refer to a GE-design machine with a hydraulic self-sequencer, a small metal block which monitors and controls the flow of high-pressure oil to the ratchet pistons (and to the jaw clutch closing cylinders for machines equipped with a jaw clutch). There many older Frame 5s which did not use a self-sequencer and operate slightly differently from a mechanical standpoint.]

When was the last time the filter of the hydraulic ratchet system was changed? There usually ISN'T a differential pressure gauge or switch on the filter to alert operators/technicians the filter is dirty and needs to be changed so it's often overlooked. ALSO, there usually isn't a pressure gauge on the discharge of the Hydraulic Ratchet Pump to indicate the pump pressure. (Both of these gauges are good to add during the next maintenance outage--and add them to the rounds list the outside operators make when the machine is on Cooldown to monitor differential pressure and pump discharge pressure).

The unit is from 1980, The problem is existed after first start since 3 months and we did nothing to solve the problem. The doors are open mostely
The fan is working when it at zero speed
4 or 5 times has stopped and restart after 7 hours when rachet run at least 20 times the unit is running right now
The only problem is the rachet does not rotate directly it is trying three times and each attempt rotate 10 degree then go to die after the wheel space goes down to 380c the rachet starts and rotates the rotor dmothely every 3 mins
The jow is working well
Do you all think there is problem inside the thermal block sush as blades or bearing issue?

 

@AhmedSaeed2332,

Poor clearances inside the "thermal block" could be the problem, or just part of the problem. (Everyone wants to find A single "smoking gun" to blame 'the problem' on.) A problem is with this line of thinking you will basically have to take the machine apart to prove or disprove this theory.

HOWEVER, the machine most likely has borescope inspection ports that could be used to insert a borescope to have a reasonably good inspection to see if there are rub marks--which would most likely be the result of continued attempts to ratchet the machine during the time when the wheelspaces temperature remain elevated after a shutdown.

We don't know how often the machine has been stopped and had this ratchet problem (we know it's been about three months but we don't know how many times the machine has experienced this problem), and I would expect any rubs have been "rubbed out" by this point, which should be discernible by borescope inspection.

Further, if the rubs in the machine were severe enough it's reasonable to expect the vibration levels in the machine would also have increased since the maintenance outage, and we don't know if that has happened or not.

It's not uncommon after a maintenance outage where the rotor has been removed and/or the nozzle blocks and/or the buckets and/or the bearings were replaced. But, again, I would expect that any rubs which were occurring from the beginning of this problem have been well worn and not so much of a problem any more. And, it's NOT just turbine shrouds and buckets it can be axial compressor blades and casing as well. We also don't know how old the axial compressor rotor is in the machine and what condition it is in.

It's also not uncommon for new bearings to be tight after new replacements but that usually causes elevated bearing metal temperatures, bearing drain temperatures and/or elevated vibration levels until the time the bearing gets "worn in."

If the rotor was removed, it's customary to have an internal and external alignment performed. There are multiple types of internal alignments, some are better than others. And we don't know that was done or how it was done.

So, you've visually examined the jaw clutch to be sure it is closed and remains closed during the attempted ratchet operations. Because, it's not uncommon for the jaw clutch to partially open during a ratchet operation; that's why at the end of the ratchet retraction stroke a Mark* turbine control system goes into a partial forward stroke to make sure the clutch stays engaged during the time between ratchet strokes. Older machines with worn bearings and journals will often have the jaw clutch open nearly completely during a forward ratchet stroke, and in some cases even open fully--especially if the jaw clutch closing cylinders aren't working well and keeping the jaw clutch closed.

And if the jaw clutch limit switch isn't working or adjusted properly that could contribute to the problem.

It is NOT recommended to operate the turbine with the Turbine Compartment doors closed--primarily because the fire protection system (extinguishing agent) won't work properly if discharge. The doors have to be closed to contain the extinguishing agent inside and build up a high concentration to reduce the oxygen in the compartment to extinguish the fire. It's not safe and I imagine the company insuring the machine wouldn't be very happy to find out if there was a fire and it was not contained that the machine was operated with the Turbine Compartment doors. (They might not even pay the claim.)

But, don't rule out the hydraulic ratchet pump--and motor--and the self-sequencer. Usually, on machines of that vintage, the hydraulic ratchet pump motor is a DC motor which has brushes which have to be replaced from time to time. The hydraulic ratchet pump usually draws unfiltered oil from the L.O. reservoir and over time they wear out and need to be replaced or refurbished. (And we don't know what the L.O. condition is.) And, there's that issue of the hydraulic ratchet filter. Because there's usually no differential pressure gauge on the filter they usually don't get changed as often as they should be, and that causes the filter to rupture and dump dirt and debris into the system, including the self-sequencer and ratchet pistons and jaw clutch closing cylinders.

So, several things to consider and verify and methods to use to start ruling out what's NOT the cause. Often, troubleshooting is a process of elimination, meaning that you make and prioritize a list of as many of the possible causes of the problem and then start with the most likely cause and start troubleshooting. If that's not determined to be the cause, then move to the next most likely cause, and so forth until the cause(s) are identified and resolved.

If you don't have confidence in the crew and supervision that performed the most recent outage, then you could put more emphasis on mechanical issues. But, only you know what was done and how it was done. You should have some kind of report that usually lists specified clearance ranges for various parts of the machine AND what the as-found and as-left clearances were that can be used in this analysis.

Leaving the Turbine Compartment doors open is strongly discouraged, primarily for the fire protection reason but also for the uneven cooling issues which can be caused because ambient air is cooling the casings faster than the internal thermal block components (including the axial compressor--it IS the longest part of the machine shaft!).

Best of luck! A lot of people read these threads--now (when it's new) but also later when people are searching the "archives" of past threads for answers to their questions. So, if you can please write to let us know what you found and how you resolved the problem--it can be really helpful to many people. This kind of feedback is one of the things that makes Control.com such a useful forum. Help us to keep it useful, and use the Search feature at the top of every Control.com Forum page to search for past threads which may provide helpful information for this and other questions you may have.

Tchau!

 

@AhmedSaeed2332,

Poor clearances inside the "thermal block" could be the problem, or just part of the problem. (Everyone wants to find A single "smoking gun" to blame 'the problem' on.) A problem is with this line of thinking you will basically have to take the machine apart to prove or disprove this theory.

HOWEVER, the machine most likely has borescope inspection ports that could be used to insert a borescope to have a reasonably good inspection to see if there are rub marks--which would most likely be the result of continued attempts to ratchet the machine during the time when the wheelspaces temperature remain elevated after a shutdown.

We don't know how often the machine has been stopped and had this ratchet problem (we know it's been about three months but we don't know how many times the machine has experienced this problem), and I would expect any rubs have been "rubbed out" by this point, which should be discernible by borescope inspection.

Further, if the rubs in the machine were severe enough it's reasonable to expect the vibration levels in the machine would also have increased since the maintenance outage, and we don't know if that has happened or not.

It's not uncommon after a maintenance outage where the rotor has been removed and/or the nozzle blocks and/or the buckets and/or the bearings were replaced. But, again, I would expect that any rubs which were occurring from the beginning of this problem have been well worn and not so much of a problem any more. And, it's NOT just turbine shrouds and buckets it can be axial compressor blades and casing as well. We also don't know how old the axial compressor rotor is in the machine and what condition it is in.

It's also not uncommon for new bearings to be tight after new replacements but that usually causes elevated bearing metal temperatures, bearing drain temperatures and/or elevated vibration levels until the time the bearing gets "worn in."

If the rotor was removed, it's customary to have an internal and external alignment performed. There are multiple types of internal alignments, some are better than others. And we don't know that was done or how it was done.

So, you've visually examined the jaw clutch to be sure it is closed and remains closed during the attempted ratchet operations. Because, it's not uncommon for the jaw clutch to partially open during a ratchet operation; that's why at the end of the ratchet retraction stroke a Mark* turbine control system goes into a partial forward stroke to make sure the clutch stays engaged during the time between ratchet strokes. Older machines with worn bearings and journals will often have the jaw clutch open nearly completely during a forward ratchet stroke, and in some cases even open fully--especially if the jaw clutch closing cylinders aren't working well and keeping the jaw clutch closed.

And if the jaw clutch limit switch isn't working or adjusted properly that could contribute to the problem.

It is NOT recommended to operate the turbine with the Turbine Compartment doors closed--primarily because the fire protection system (extinguishing agent) won't work properly if discharge. The doors have to be closed to contain the extinguishing agent inside and build up a high concentration to reduce the oxygen in the compartment to extinguish the fire. It's not safe and I imagine the company insuring the machine wouldn't be very happy to find out if there was a fire and it was not contained that the machine was operated with the Turbine Compartment doors. (They might not even pay the claim.)

But, don't rule out the hydraulic ratchet pump--and motor--and the self-sequencer. Usually, on machines of that vintage, the hydraulic ratchet pump motor is a DC motor which has brushes which have to be replaced from time to time. The hydraulic ratchet pump usually draws unfiltered oil from the L.O. reservoir and over time they wear out and need to be replaced or refurbished. (And we don't know what the L.O. condition is.) And, there's that issue of the hydraulic ratchet filter. Because there's usually no differential pressure gauge on the filter they usually don't get changed as often as they should be, and that causes the filter to rupture and dump dirt and debris into the system, including the self-sequencer and ratchet pistons and jaw clutch closing cylinders.

So, several things to consider and verify and methods to use to start ruling out what's NOT the cause. Often, troubleshooting is a process of elimination, meaning that you make and prioritize a list of as many of the possible causes of the problem and then start with the most likely cause and start troubleshooting. If that's not determined to be the cause, then move to the next most likely cause, and so forth until the cause(s) are identified and resolved.

If you don't have confidence in the crew and supervision that performed the most recent outage, then you could put more emphasis on mechanical issues. But, only you know what was done and how it was done. You should have some kind of report that usually lists specified clearance ranges for various parts of the machine AND what the as-found and as-left clearances were that can be used in this analysis.

Leaving the Turbine Compartment doors open is strongly discouraged, primarily for the fire protection reason but also for the uneven cooling issues which can be caused because ambient air is cooling the casings faster than the internal thermal block components (including the axial compressor--it IS the longest part of the machine shaft!).

Best of luck! A lot of people read these threads--now (when it's new) but also later when people are searching the "archives" of past threads for answers to their questions. So, if you can please write to let us know what you found and how you resolved the problem--it can be really helpful to many people. This kind of feedback is one of the things that makes Control.com such a useful forum. Help us to keep it useful, and use the Search feature at the top of every Control.com Forum page to search for past threads which may provide helpful information for this and other questions you may have.

Tchau!

As you mentioned I am trying to solve the problem as soon as I finish I will inform you about the reason and solutions to keep it useful for the followers
Many thanks
Regards