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Shutdown of Gas Turbines 9E, 88QV
Question about shut down of gas turbines 9E

During shut down of the gas turbines 9E, the shaft is turned by the turning gear at speed 120 rpm. when 88qv trip its good or no? Please any one could clarify.

bil07,

ANY motor tripping should be cause for concern.

88QV is driving the Lube Oil Mist Eliminator fan, which draws lube oil mist from the Lube Oil Reservoir and drain piping, condenses the vapours, and prevents (to the extent possible) hydrocarbon vapors from being discharged into the atmosphere (causes pollution, a fire hazard, and makes a mess, generally).

Without the vacuum created by the Lube Oil Mist eliminator fan the vapours have now way to exit the Lube Oil system, and can build up creating an even greater hazard (risk of explosion/fire).

Why is the Mist Eliminator fan motor tripping? Are bearings (motor bearings; fan bearing(s)) failing or failed? In general the Mist Eliminator fan motor is relatively small, and it's difficult to imagine a condition where the suction created by the fan would exceed the motor's thermal overload rating.

Is there a problem with the motor thermal protection? Have you measured the motor's current draw with a clamp-on ammeter to see how much current is being drawn when the unit is on cooldown, versus when it's running? (You didn't mention problems with the fan motor tripping when the unit is running....)

Finally, GE-Belfort, which has been given responsibility for GE-design Frame 9Es in the past few years, is famous for over-complicating systems which worked just fine for decades. (Why? Because they can.) If you can post the Lube Oil system P&ID to a web-hosting site or a site like DropBox or Google Drive or OneDrive and then post the link to this thread we could review the system drawing and possibly make some comments. It's possible they have added some solenoid or motor-drive dampers or some such crap which is causing a problem for the Mist Eliminator fan motor when the unit is on cooldown--but without being able to see the P&ID for your site we can't say for sure.

Hope this helps!

thanks csa,

my gas turbine 9e belfort! dln1 in coldown 88TG AND 88QB running BUT 88QV1/88QV2 stopping its god !!!

bil07,

Sorry to hear you have a Belfort-packaged GE-design Frame 9E. It's a great turbine, but when Belfort gets involved the auxiliaries can be a mess.

I think you meant to say that when the unit is on cooldown 88TG (the turning gear motor) and 88QA (the Aux. L.O. Pump) are running, but in your first post you said 88QV was tripping. Do you mean that 88QV-1 & -2 are automatically shut down ("turned off") when the unit goes on cooldown? If so, you really need to speak with GE-Belfort to understand their intent and their safety assessment of the situation.

In GE-speak, "tripping" means an emergency shutdown of a piece of equipment or a motor. I know, in some parts of the world, "tripping" is used to mean stopping or turning-off either manually or automatically. But, that's really a perversion of the word, and is not a very accurate description. If the L.O. Mist Eliminators are automatically stopped (shut down; turned off) by the turbine control system when the unit is on cooldown, that's different than if their are "tripped"--such as by a thermal overload relay--to stop the operation of the motor to protect the motor and/or the fans. I interpreted your statement to mean the motors were being stopped because of some emergency condition (such as a thermal overload).

Again, if the L.O. Mist Eliminator fans are being automatically stopped when the unit goes on cooldown, that probably (not certainly, but probably) means that the engineers at GE-Belfort have determined (rightly or wrongly) that the L.O. Mist Eliminators are not necessary for safe operation of the unit when it is on cooldown.

Personally, I would agree with that assessment--if the unit were put on cooldown from a cold conditions (after being at zero speed for some time, the unit internal temperatures having reached ambient temperature, and the L.O. in the reservoir having cooled to near ambient temperature). HOWEVER, if the unit was shut down by the operator or tripped (because of some emergency condition) and the L.O. in the reservoir is hot (probably near 80 deg C or so), and the unit is going on cooldown and will operate for many hours on cooldown, I would say the L.O. Mist Eliminators are necessary for safe operation. But, that's based on a typical design of the L.O. system, where the only vent path for L.O. vapours is through the L.O. Mist Eliminator vessel, and the vapours are drawn through the vessel by the L.O. Mist Eliminator fan. This provides ventilation (and some slight cooling) of the L.O. Reservoir and drain piping, as well as condensation of the L.O. vapours.

I surmise GE-Belfort is trying to reduce parasitic electrical loads during cooldown to help reduce costs of operation. But, only they can address the issue of unit safety if the L.O. Mist Eliminator fans are not running during cooldown when the unit and L.O. are hot after a shutdown or trip.

Hope this helps!

0 out of 1 members thought this post was helpful...

thanks.

but when turbin 9e in mode coldown its problem when 88qv trips! but 88TG and 88QB running or stop all 88TG AND 88QB then 88qv tripped.

bil07,

I'm sorry, but you are not clear with your problem statement. And, what is 88QB? Is it a second AC motor-drive L.O. Pump that only operates when the unit is on Cooldown? I am familiar with 88QA--the Auxiliary L.O. Pump, and some machines without an accessory gear have an 88QA-2, or 88QB, but without being able to see you L.O. P&ID I don't know what 88QB is or does.

You keep using stopping and tripping--as if they are interchangeable words/terms--and they are not, in GE-speak. Tripping implies an emergency shutdown because some condition was detected that required the process to be terminated. Stopping refers to a normal automatically-initiated shutdown, such as when a process or sequence ends.

You should probably go back to the packager of the turbine and auxiliaries and explain what you believe is happening and ask why it is happening, and if it should be happening.

You could try giving us a little sequence of events during coastdown from flame-out to cooldown. Say, flameout at 9.27% speed; unit continues to coast down in speed while 88QA and 88QV-1 and 88QV-2 are all running; at 14HC (300 rpm) 88TG starts and cooldown operation sequence is in progress. At what point do 88QV-1 &-2 shut down? Are they shut down by the turbine control system, or because of some problem like thermal overload, or ??? Does the unit continue to remain on cooldown (turning gear)? What is 88QB and when does it start and stop?

In the past, on non-GE-Belfort machines, whenever a L.O. pump (Main or Auxiliary) was running the L.O. Mist Eliminator(s) also ran. That was during starting, acceleration, loaded operation, shutdown and cooldown. If the unit was put on cooldown in preparation for a start the L.O. Mist Eliminator(s) would start as soon as the Aux. L.O. Pump started, and continued to run when the Aux. L.O. dropped out at 14HS (95% speed) and would continue to run when the Aux. L.O. Pump would start during a shutdown/trip when speed dropped below 15HS (94.5% speed) and all the way down to cooldown and would remain running as long as the unit was on cooldown (to provide oil to the bearings for cooling and lubrication while the shaft is spinning on cooldown).

Again, it's possible GE-Belfort have devised some kind of means to contain L.O. vapors when the unit is on cooldown and shut down (automatically) the L.O. Mist Eliminators to reduce electrical consumption when the unit is on cooldown--that's about all I can surmise they might have done.

If any auxiliary pump motor TRIPS while operating there should be a Process Alarm to alert a conscious operator to the condition. ARE THERE ANY ALARMS WHEN AN AUXILIARY MOTOR TRIPS WHILE RUNNING ON COOLDOWN? AND IF SO, WHAT IS/ARE THE ALARM(S)?

If you want help you have to provide the answers to the questions. To make it easier I will list the questions:

-What is 88QB and when does it normally start and stop?
-Are there any Process (and Diagnostic) Alarms annunciated when cooldown is in operation?
-If there are alarms (Process and/or Diagnostic) Alarms annunciated when cooldown is in operation, what are they, specifically? List the time/date and the associated alarm text messages for all alarms annunciated just prior to and during cooldown operation.
-What is the L.O. Tank Temperature when cooldown starts? (The signal name is usually ltot, or LTOT, or ltot1 or something similar.)
-What is the L.O. Header Temperature when cooldown starts? (The signal name is usually ltth1, or LTTH1, or something similar.) What does the L.O. Header Temperature do after 15 minutes of cooldown operation; 30 minutes of cooldown operation; 60 minutes of cooldown operation; 240 minutes of cooldown operation?
-When, exactly (in time after the unit reaches cooldown speed) does 88QV-1 and/or -2 stop?
-What happens when 88QV-1 and/or -2 stops when the unit is on cooldown? Does 88TG then also stop? Does 88QB also stop?

Without answers to these questions, it will be virtually impossible to understand what is actually happening, and why it might be happening.

Please write back with more, clearer information!

Thanks

88QV-1 &-2 shut down? because of some problem like thermal overload,
88QB1: pump selectively burying generator.
It's good in cool down gas turbine 9e running 88TG AND 88QA.

bil07,

>88QV-1 &-2 shut down? because of some problem like thermal
>overload,

A thermal overload of an electric motor is caused when the mechanical load the motor is requiring more amps than the thermal overload is designed for. So the question is: Why does the mechanical load for the L.O. Mist Eliminator vent fan(s) increase when the unit is on cooldown?

So, that brings up another question: When did this problem start? Has it been ongoing since commissioning, or did it start--maybe after a maintenance outage? How long has it been since the Mist Eliminators were examined/cleaned? Is there any visible vapour/mist coming out of the Mist Eliminator(s) when the unit is on cooldown?

>88QB1: pump selectively burying generator.

What the heck does "burying generator" mean?

>It's good in cool down gas turbine 9e running 88TG AND 88QA.

When does 88QB run? Is 88QB some kind of lift oil or "jacking oil" pump for the generator bearings to provide extra lift to keep the bearings from being damaged at low speed, so it runs during cooldown?

If the L.O. Mist Eliminators were working after commissioning and for some time, then something has to have changed to cause the problem. Think back to when the problem started, and then try to remember what happened just before the problem started.

And get a clamp-on ammeter and measure the current drawn by the Mist Eliminator fans when the unit is running at rated speed, and then when it goes on cooldown (just before they trip).

And if the vent fan motors are tripping, there SHOULD BE Process Alarms to indicate either the individual fans are tripping or there is a Aux. Motor Overload (which means it could be any one of several motors with the thermal overloads wired in series). I have to believe GE-Belfort has wired each individual thermal overload to the Mark* to provide motor-specific overload Process Alarms (they always complained the GE-USA packages didn't!).