Overview of Jacking oil system:

Purpose:

The jacking oil system performs the following purposes:

•  Prevents metal to metal contact in the journal bearings by producing a hydrostatic oil film when the rotational shaft speed is too low to create a continuous hydrodynamic oil film.
•  Reduces the break away torque during run-up of the steam turbine rotor.

Function:

 This is reached by the following functions:

• Generates jacking oil pressure and flow.
• Guides and distributes jacking oil to the steam turbine journal bearings. 
• Drains the jacking oil into the bearing pedestal

Components:

 The following components are needed as a minimum:

• Jacking oil pump

• Pressure limiting valve

• Flow control valves

• Forwarding and distribution piping

• Lube oil tank

Principle:

1.The jacking oil system protects the turbines journal bearings during start-up and shut-down. The shaft of the steam turbine rests on the journal bearings.

2.Before the shaft is turned, jacking oil is supplied to the bearings to lift the shaft so that it floats on an oil film rather than on the metal surface of the bearings.

3.The jacking oil pump supplies the jacking oil system. This pump is an axial piston type, which is located on the lube oil tank. The Lube oil system feeds the jacking oil pump from downstream of the lube oil filter. A common AC motor drives both the jacking oil and turning gear pump

 

4.A pressure limiting valve maintains the pressure in the jacking oil system in accordance with the operating data. The oil passes through a flow control valve before entering each bearing. It drains into the bearing pedestal and flows back to the lube oil tank through the drain pipe lines, together with lube oil returning from the lube oil system.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hydrostatic Turning Gear :

Purpose:

 The turning gear system performs the following functions:

• Continuously turns the rotor at low speed before start up and after shut-down.
• Ventilation, caused by the blades, prevents bending due to temperature differences between top and bottom, caused by natural convection after stand still of the hot turbine. 
• Avoids the rubbing of blading and seal strips due to rotor bending during restart.

Function:

This is reached by the following functions:

•  Pressure generation (motor / hand)
• Pressure control
• Engaging / disengaging of turning gear
• Turning of rotor
• Hydraulic control

Components:

 Therefore the following components are needed as a minimum:

• Turning gear pump
• Hydro motor with drive pinion
• Sliding piston
• Control solenoid valves (creep speed, rotary, engaging) 
•  Pressure control and reducing valves
• Hand pump