WARMING UP OF PROPULSION TURBINE• Warming up depends on age and design of turbine, and type of ship.

• All main valves between boiler and HP turbine upto main warming valves are opened while gland steam, auxiliary heating and manoeuvring valves are shut.

• Heating rate should be controlled so that inlet temperature of the LP turbine reaches to 75oC after one hour. If the turning gear was in use then now it may be disengaged.

• Gland steam of pressure 0.35~0.5 bar is used and vacuum is raised rapidly, turbine may be turned a few revolutions on steam. This must be done in ahead direction unless astern becomes essential to prevent mooring difficulties.

WARMING UP OF PROPULSION TURBINE (CONTD.-1)• The warming through valve is now closed and ahead manoeuvring

valves opened slightly. Turbine should be turned under steam at two minutes intervals for 15 minutes. Vacuum should be maintained at 0.34

bar.

• Drainage is very important to avoid distortion. All drains must be kept clear and should not be closed until the turbine has been rotating for several minutes.

• Auxiliary exhaust steam entering main condenser should be reduced to minimum at stand by periods.

• During prolonged astern running, LP turbine expansion indicators should be closely watched and it’s casing temperature should not exceed 250oC and exhaust space should not exceed 120oC.

STARTING PROCEDURE OF COPT• Check the oil level in sump, drain off any water.

• Start the priming lub oil pump for turbine.

• Turn the turbine by hand using a lever.

• Start cooling water to condenser and lub oil cooler.

• Start up the vacuum through steam ejectors.

• Close the drains for casing, exhaust, and steam inlet valve.

• Open the exhaust valve of turbine.

STARTING PROCEDURE OF COPT (CONTD.-1)• Open the gland steam to a low pressure and warming up valve.

• Start up condensate pump and maintain water level .

• Switch on alarm panel and reset any existing alarm.

• Try out lub oil low pressure and high back pressure trips and remote and local emergency stops.

• When turbine has sufficiently warmed up, throttle open the main steam valve and run turbine at 200 RPM for about 5 minutes.

STARTING PROCEDURE OF COPT (CONTD.-2)• Gradually open the steam valve until governor takes

over control, open the steam valve full. • Hand over the controls to Cargo Control Room. • Monitor steam chest, exhaust and gland steam and lub

oil pressures.

• Monitor turbine bearing and pump bearings temperatures.

GOVERNING OF STEAM TURBINES

• The speed of the turbine is controlled either by varying the steam pressure or by varying steam flow.

• The speed of turbine may be controlled by throttling, which is the simplest method

• Throttling is associated by reduction of pressure at constant enthalpy.

• The flow of steam may be controlled by grouping of nozzles and each group is controlled by it’s valve.

• Hybrid control is a combination of throttle valve control and nozzle valve control. One nozzle group is controlled by throttle valve and remainder by nozzle valves.

GOVERNING OF STEAM TURBINES (CONTD.-1)

• Bypass control is used for obtaining extra power when full pressure is applied to the first stage.

• The bypass valve takes steam from first stage to the later stage where area is large and extra power can be obtained.

• Steam pressure is controlled from the governor valve.

• In the simplest form the turbine may have just one nozzle.

• In extreme case nozzles may be arranged all around in which case the turbine will have balances and high torque.

EXPANSION OF STEAM TURBINES

EXPANSION OF STEAM TURBINES (CONTD.-1)• The expansion arrangement shown above is for a high pressure turbine.

This allows the casing to expand axially from the gear box end and radially.

• Two sliding feet support below the casing centre line have axial keys for location.

• Four support palms are provided of which two aft do not permit axial movement whereas two forward allow axial movement and are connected to horizontal extensions of the casing joints.

• Rotor position relative to casing is controlled by the thrust bearing at the forward end.

• Internal rings correctly dimensioned and fitted in thrust bearing ensures no further adjustment.

SELF CLOSING EMERGENCY STOP VALVE

• This valve closes automatically and shuts off the steam supply to the turbine in following conditions:-

• Loss of lubricating oil pressure• Turbine over speed• Excessive axial rotor travel• Low condenser vacuum

• This valve can be closed manually by:-

• Handwheel• Emergency hand control• Deck manual control

SELF CLOSING EMERGENCY STOP VALVE (CONTD.)

• To open this valve, supply valve lever is first pressed followed by turning of hand wheel. Supply valve lever admits steam through ball and supply valve to the left side of the piston.

• Piston is loosely fitted in cylinder due to which steam also passes on the back side of the piston and keeps the piston balanced under spring force.

• Valve is held in open position by a catch on supply valve lever.

• If oil pressure or vacuum drops, steam on the back side of the piston will be drained resulting in closure of valve by the force of steam on the left side of piston.

SELF CLOSING EMERGENCY STOP VALVE (CONTD.-1)

LOW VACUUM TRIP

LOW VACUUM TRIP• To protect the condenser from over pressure this device is

equipped.

• Increase of pressure on the diaphragm top due to decrease in vacuum or hand release from deck causes downward movement.

• Through the linkage the valve opens and leads the steam to drain, which closes the emergency stop valve.

• The gear works equally well by releasing oil pressure and functioning on the control valve in similar way to other oil operated trips.

OVERSPEED & AXIAL MOVEMENT TRIP MECHANISM

OVERSPEED & AXIAL MOVEMENT TRIP MECHANISM

• In this position, oil in annular space D is allowed to discharge through port J and the steam valve shuts.

• Tripping speed can be varied by nut B. To reset the valve, catch spindle is pulled by knob K.

• In case of excessive axial movement of rotor, control bush N moves with rotor but index bush E remains in place. Oil trapped in annulus G is released through annulus H which stops the turbine.

EMERGENCY OVERSPEED TRIP

EMERGENCY OVERSPEED TRIP (CONTINUED)

• Speed control governor consists of a non rotating oil supply tube and rotating assembly of cantilever arms.

• The cantilever arms hold a ball valve at their free ends.

• As the speed increases, cantilever arms move radially outwards, opening the ball valve and allowing oil to escape and drain.

• This in turn reduces oil pressure which acts upon the servomechanism and would close the steam supply.

GOVERNOR SERVOMOTOR

GOVERNOR SERVOMOTOR (CONTINUED)• When turbine is not running, governor output is maximum and

steam valve has full opening with servo-piston completely up.

• As steam is admitted to turbine, governor starts rotating with fly weights moving outwards resulting in upward actuator movement.

• As pilot valve is connected with linkage, it moves up and supplies oil on top of servo-piston. Servo-piston starts moving down draining oil from bottom side and closing the steam valve simultaneously.

• When desired speed is achieved, pilot valve will block both oil ports and maintain the desired speed.

• Any change in load / speed will be corrected automatically.

TURBINE CLEARANCE GAUGES

TURBINE CLEARANCE GAUGES (CONTINUED)• For smooth operation of turbines, clearances have to be

maintained within close tolerances.

• Finger piece gauge along-with feeler gauge is used to measure the wear of thrust bearing which will be reflected as the shaft’s excessive axial movement. This is checked when the turbine is stopped.

• Poker gauge also measures the wear of thrust bearing and excessive axial movement of shaft. This can be used when the turbine is at rest and also when it is running. The reading is given on a fixed scale.

TURBINE CLEARANCE GAUGES (CONTINUED)

• Casing axial position indicator describes about the expansion of casing directly on a scale.

• Bridge gauge is used to measure the wear of journal bearing or the drop of rotor.

• This is obtained after removing the upper half of bearing and placing the depth gauge on top of rotor.

• Wear will be obtained by comparing present reading with original reading.

ENERGY LOSSES & METHODS OF IMPROVEMENT

• We can see that only 32% heat is available for useful work.

• Remaining 68% goes as waste, of which 57% goes in condenser and 11% in boiler.

• Following methods may be applied to reduce losses:-

• Use of cross compound turbine plant.

• Use of complex cycle with regenerative feed heating and reheating.

• Scoop intake of condenser C.W.

• Improved automation, leading to online control.