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48 Hrs Load Profile for GE 7EA Cool Down
looking for 48 Hrs load profile table for GE 7EA machine cool down.

looking for 48 Hrs load profile table for during the GE 7EA machine cool down.

Because for the GE 7EA 88HR motor 125V DC power battery capacity is
covered more then 48 Hrs?

Please Help

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

lemo,

Are you asking if the 125 VDC battery--without AC power available for charging the battery--can operate the hydraulic ratchet system for as long as 48 hours?

Because, when the hydraulic ratchet is operating there has to be lube oil supply to the bearings, and if there is no AC supply to the unit then the turbine control system will start and stop the DC Emergency L.O. Pump motor every time the ratchet pump operates--so approximately every three minutes or so for as long as a full ratchet sequence (forward, retraction, initial start of another forward stroke).

So, without AC power for the unit (I'm presuming you're talking about a "black" condition where there is NO AC power for any auxiliaries--not just the 125 VDC battery charger) the battery has to supply both the hydraulic ratchet pump motor AND the DC Emer L.O. Pump motor during cooldown. (Lube oil flow to the bearing is required for lubrication, AND for cooling the bearings so that the heat from the shaft doesn't cause the bearing materials to soften or melt. That's why the Aux. L.O. pump (usually) runs continuously during cooldown (ratchet) operation--to keep oil flowing to the bearings to remove the heat from the bearings and the shaft. If the Aux. L.O. Pump isn't available, then the DC Emergency L.O. Pump is cycled, both to provide lubrication when the shaft is being turned and to help cool the bearings as much as possible.)

And, why 48 hours? Even in most desert environments, GE-design Frame 7EA heavy duty gas turbines will reach internal temperatures that will allow the ratchet system to be disabled (OFF) in less than 48 hours. The key is to get the highest wheelspace temperature down to less than approximately 200 deg F--because bearing material begins to soften and melt at approximately 300 deg F, so by getting the highest wheelspace temp down to 200 deg F or below the #2 and #2 bearings should be safe to stop L.O. flow, and the axial compressor rotor should also be cool enough to stop cooldown operation.

"Load" (unless we're talking about battery load) usually refers to generator load, and there's no generator load during cooldown (ratchet) operation. So, the question is not very clear; can you be more specific, please?

>>>CORRECTION<<<
>The key is to get
>the highest wheelspace temperature down to less than
>approximately 200 deg F--because bearing material begins to
>soften and melt at approximately 300 deg F, so by getting
>the highest wheelspace temp down to 200 deg F or below the
>#2 and #3 bearings should be safe to stop L.O. flow, and the
>axial compressor rotor should also be cool enough to stop
>cooldown operation.

By CuriousOne on 28 July, 2017 - 10:30 pm

I did not think a 7EA could ratchet on DC.

Some Customers were absolutely furious when they learned the 7EA units with air--cooled generators did not have a D.C. Ratchet Pump, so GE retrofitted some units and made it a very expensive option for others, which some Customers purchased (but not many).

There was several people who believed every 7EA should have a ratchet and were working "in the bay" and unofficially to make it affordable and simple. Since we don't know the vintage of this particular unit, it's possible the dream of DC hydraulic ratchet pumps for 7EAs came to fruition. Which would be a good thing.

Or, maybe someone (the original poster) is thinking of designing their own DC hydraulic ratchet system and is look for information. The hydraulic flow rates and pressures required for units with air-cooled generators are significantly higher than those for GE-design Frame 5s and -6s, and the power (current) requirements for such a system would likely require a larger, or even a second, and larger, battery. But since we didn't get much in the way of information about what the original poster was going to use the information for, we're all pretty much guessing--aren't we?

Isn't this good crack?