Sometimes Jacking Oil Pumps (to lift the shaft) are provided to Steam Turbine & Generator and some times only to Generator.

On what basis do we decide to provide the Jacking Oil?

Is it the mass of the shaft?

 

premkumar,

It's the mass of the shaft and the type/design of bearings and shaft journals. For example, horizontal tilting pad bearings usually need a little "help" at low speed and for turning gear operation. Journal bearings can be designed such that they don't require jacking/lift oil, but again it does also depend on the weight (mass) of the shaft and the space available for the journals and bearings. If the design of the bearing/journal is such that a sufficient oil wedge/lubrication can't be established to prevent bearing/journal damage during low-speed and/or turning gear operation then the decision is usually made by the manufacturer to add a jacking/lift oil system to the turbine and/or generator.

>On what basis do we decide to provide the Jacking Oil?

Since we don't know much about your position/experience, I presume you are writing from an operations/technical perspective. I don't believe operators decide when to provide jacking/lift oil; that's done by the turbine- and/or generator manufacturer(s). And, the unit control system should automatically start/stop the jacking/lift oil pump(s) as appropriate.

Hope this helps!

 

Yes, I was asking regarding the basis on which the Turbine/generator manufacturer decide on providing the Jacking Oil System for the lift.

Ok, thank you.

 

Yes, I was asking regarding the basis on which the Turbine/generator manufacturer decide on providing the Jacking Oil System for the lift.

Ok, thank you.

It is because the blades in Steam Turbines are extremely close to each other(even closer than on those in Gas Turbines)
so the minimum lift from the jacking oil would make them come even closer and potentially damage the system. Thats why you see even large ST's have jacking oil only to the Generator