The document discusses shaft turning gear, which rotates the turbine shaft and other equipment at low speed after shutdown to ensure uniform cooling. This prevents issues like bending. It is also used to slowly break inertia during cold starts. There are two main types: hydraulic and manual. The hydraulic type uses a hydraulic motor supplied with lube oil to rotate the shaft at 120 rpm. It has an engaging mechanism that uses oil pressure to move a drive pinion into mesh with a gear rim to engage the turning gear. The manual type uses a hand-operated mechanism to manually rotate the shaft.

1. Turning Gear
Presented by
Abdullah Al Mamun
SDE (MMD)
Sirajganj 225MW CCPP (Unit-01)

2. Shaft Turning Gear
• After the turbine-generator has been shut down, the line of shafting
(gas turbine and generator) is transferred to turning gear mode and
rotated at low speed. This flow of air forced through the gas turbine
by the blading ensures uniform cool down of the machine.
• The turning gear rotates the turbine shaft and other accessory
equipment to make sure that there is uniform cool down of the shaft.
Otherwise it can result in sagging or bending of the turbine rotor.
During turbine starting also it is first put on the turning gear to break
the inertia slowly, if it's a cold start.

3. Shaft Turning Gear
• Turning gear speed is selected so as to ensure both sufficient air
throughput for uniform cooldown of the casing and to prevent blade
clattering.
• For mechanical design reasons, the turbine blades are seated loosely
in the rotor disk slots at room temperature. At very low shaft speeds
the blade roots shift slightly in their slots and clatter audibly. Above a
certain speed, centrifugal force firmly seats the blade roots.

4. Types of Turning Gear
• Hydraulic Turning Gear
• Manual Turning Gear

5. Hydraulic Turning Gear
• Jacking oil is supplied to the hydraulic motor and the swingarm
actuator. During operation of the gas turbine with the jacking oil
pump shut down, the hydraulic motor is supplied with lube oil via
swing check valve MBV35AA201 to prevent damage that is typical of
extended equipment standstills.

6. Construction Of Hydraulic Turning Gear

7. Construction Of Hydraulic Turning Gear

8. Hydraulic Motor

9. Technical Data
Parameter Value
Breakaway moment (ML) 880 Nm
Turn speed (nT) 120 rpm
Weight 200 KG

10. Engaging Mechanism
• The drive pinion (9) is mounted on a
swing arm (8).
• To shift the drive pinion (9) inward, oil
pressure is applied to the engaging
cylinder (6).
• The motion of the engaging cylinder
piston causes the swingarm and the
attached drive pinion (9) to move toward
the gear rim on the intermediate shaft,
meshing the drive pinion (9) with the
shaft gear rim.
• When the shaft turning gear is not in
operation, the engaging cylinder is not
pressurized and the swingarm is held in
the disengaged position by the spring (7).

12. Manual Turning Gear

13. Manual Turning Gear