There is a til from ge (til 1420-2r1) which can be applied to the gas turbines frame 5-6-and 9. This til is not valid for the turbines and controls supplied after 2003. The title is Lube oil Logic enhancement.

I have to implement the logic in a markv idos. the turbine is frame6 monoshaft which drives a generator. Pratically there was a gas turbine in which the ELOP was stopping automatically during a shut down where the a.c. was lost and also the speed pickups where lost,, and let's add that even 3 pressure switch where not good calibrated.The consequence was damamged bearings

my solution was to take the signal L14HR and let it in a timer of 30 min and the resulting signal i would put it in the L4qez logic instead of the L14hr. Did somebody implemented already this logic somewhere??

Thanks in Advanced

 

The question posted was not fully clear - especially the 30 min timer. But if your speed probes 77 NH-1, 2, 3 have gone bad then how does the system sense L14HR = 1, which you are talking about. Mention in more detial your query

 

ok sorry i will be more clear,better you know all the story.

the emrgency dc lube oil pump operates in the event of loss of ac power supply to the electrically operated lube oil main pumps or failure of the main mechanichal lube oil pump.This causes a loss of lube oil pressure, and initiates the emergency lube oil pump operation.

The operation of the emergency lube oil pump is also controlled by the speed pickups. Upon zero speed detection the dc pump is stopped due to a perceived turbine shaft standstill condition.

However, an event was reported in which the loss of speed signal caused the DC lube oil pump to stop its operation while the turbine shaft was still rotating. This caused extensive damage to the bearings.

Ge has developed a new control software to enhance the operation of the dc lube oil pump. The new control software extends the operation of the dc pump by 30 min following a turbine trip due to loss of ac power or loss of lube oil pressure.

This enhancement ensures that even if the speed pick up signal is lost, the dc pump will maintain adeguate lube oil flow through the bearings untill the unit is safely brought down at zero speed. The 30 min is an estimated maximum required time to decelerate the unit from rated speed to zero speed.

Now my ladder diagram is as following:
FIRST LINE:

L14HA NOT L63QL2A NOT L63QT2A NOT L63QT2B--L4QEZ

L72QEZ IN OR WITH L14HA

SECOND LINE GOING TO L4QEZ:
L14HR NOT L1X NOT L4 NOT L20CSX

that is the logic which i have.
My solution was, as i wrote in the previus email, that in case you are running with the turbine and suddenly you have an abnormal shutdown as mentioned above, where you lose all including speed pickups. so imagine the machine in which the 3 pressure switches are not working properly showing healthy conditions even if it is not true. the pick up are lost, we are going down the l14HA, and the pump stops, while it is needed.

My solution was to take the l14HR and let it in a timer of 30 min. create a signal for example l14HRDEL In the output of the timer and insert this signal in the logic showed above replacing the L14HR.

My question was: Can work?
Do you have any suggestions to make it better?
to answer the question above, i think that if the speed pickup signals are lost automatically even if we are at FSNL you will see the signal L14HR=1 because TNH will be suddenly less then 0.06%

Thanks

 

" GE has developed new control software to enhance the operation of the DC lube oil pump. The new control software extends the operation of the DC lube oil pump by 30 minutes following a turbine trip due to loss of AC power or loss of lube oil pressure.

This enhancement ensures that even if the speed pickup signal is lost, the DC pump will maintain adequate lube oil flow though the bearings until the unit is safely brought down to zero speed. The 30 minutes is an estimated maximum time required to decelerate the unit from rated speed to zero speed"

I have quoted from the TIL above as I think you are a little confused. What GE are saying is that they want 88QE to run for 30 mins. from the time of trip, not from 14HR pickup. I haven't implemented the change here, but I would think that a 30 min. timer initiated by L4 should be able to be installed somehow to keep 88QE running for 30 mins. after a trip. Without seeing your software I couldn't do better than that but if you can send me at least your L4QEZ software to [email protected], we can maybe take it a bit further.

 

I don't know if it helps but Other OEM's have started to replace the DC motor for back-up purpose of critical drives. One solution used is called UMD and utilizes the often existing battery backup to run the standard installed AC motor for the lube oil pump and other auxillary systems in emergency mode. Solid state technology with instant transfer from mains to battery supply when variations or disturbances occur in the power supply. No speed drops during mains outage are recorded.