In the event of a total blackout on a 600Mw thermal power plant, I would obviously lose my CCW to the Turbine bearings, but the DC pump would kick in and allow the machine to coast down to allow manual barring of the shaft. My worry is, how would the heat on the HIP shaft affect the bearing journals, assuming the shaft is still around the 550 degrees mark? I am considering an emergency header tank for a feed to the coolers but in all my years on power generation, I have never come across such a system.
Appreciate any feedback in advance.
Without seeing your logic I can't say that your machine will operate like other GE machines I have worked with. But that being said, the other GE machines I have worked on have logic that will run the DC pump every 16 minutes, for 3 minutes, once the shaft is at zero speed if any bearing metal temperature is greater than 150 degf. I have experienced several black plant events with that caused this logic to be executed. The temperature and volume of the lube oil tank allows oil to be delivered to the bearing areas without additional cooling from closed loop coolers or fin fan coolers. Our black plant events have been fairly short but I would think that there is enough volume in the tank to keep oil temperatures low enough to provide cooling during this time to keep bearing temperatures less than 350 degf which is the lowest melting point of babbit bearing material that I am aware of.
Hope this helps. If you provided more info as the make and model of turbine this would help us better understand what type and vintage of machine you are dealing with.