Warming-through a steam turbine
First open all the turbine-casing and main steam-line drain valves and
ensure that all the steam control valves at the manoeuvring station and
around the turbine are closed. All bled steam-line drain valves should be
opened. Start the lubricating oil pump and see that the oil is flowing
freely to each bearing and gear sprayer, venting off air if necessary and
check that the gravity tank is overflowing.
Obtain clearance from the bridge to turn the shaft. Engage the
turning gear and rotate the turbines in each direction.
Start the sea water circulating pump for the main condenser. Then
start the condensate extraction pump with the air ejector recirculation
valve wide open.
Fig: Energy conversion in a steam turbine
Open the manoeuvring valve bypass or 'warming
through' valve, if fitted. This allows a small quantity of steam to pass
through the turbine and heat it. Raising a small vacuum in the
condenser will assist this warming through. The turbines should be
continuously turned with the turning gear until a temperature of about
75°C is reached at the LP turbine inlet after about one hour. The
expansion arrangements on the turbine to allow freedom of movement
should be checked.
Gland sealing steam should now be partially opened up and the
vacuum increased. The turning gear should now be disengaged.
Short blasts of steam are now admitted to the turbine through the
main valve to spin the propeller about one revolution. This should be
repeated about every three to five minutes for a period of 15 to 30
minutes. The vacuum can now be raised to its operational value and also
the gland steam pressure. The turbines are now ready for use.
While waiting for the first movements from the bridge, and between
movements, the turbine must be turned ahead once every five minutes
by steam blasts. If there is any delay gland steam and the vacuum should
Once warmed through, the turbine rotor must not remain stationary
more than a few minutes at a time because the rotor could sag or distort,
which would lead to failure, if not regularly rotated.
Astern operation involves admitting steam to the astern turbines.
Where any considerable period of astern running occurs turbine
temperatures, noise levels, bearings, etc., must be closely observed. The
turbine manufacturer may set a time limit of about 30 minutes on
continuous running astern.
Emergency astern operation
If, when travelling at full speed ahead, an order for an emergency stop
or astern movement is required then safe operating procedures must be
Ahead steam is shut off, probably by the use of an emergency trip, and
the astern steam valve is partly opened to admit a gradually increasing
amount of steam. The turbine can thus be brought quickly to a stopped
condition and if required can then be operated astern.
The stopping of the turbine or its astern operation will occur about 10
to 15 minutes before a similar state will occur for the ship. The use of
emergency procedures can lead to serious damage in the turbine,
gearbox or boilers.
Manoeuvring revolutions are usually about 80% of the full away or full
speed condition. Once the full away command is received the turbine
can gradually be brought up to full power operation, a process taking
one to two hours. This will also involve bringing into use turboalternators
which use steam removed or 'bled' at some stage from the
Checks should be made on expansion arrangements, drains should be
checked to be closed, the condensate recircuiation valve after the air
ejector should be closed, and the astern steam valves tightly closed,
Prior to arriving at a port the bridge should provide one to two hours'
notice to enable the turbines to be brought down to manoeuvring
revolutions. A diesel alternator will have to be started, the turboalternator
shut down, and all the full away procedure done in reverse
Related Info: Impulse steam turbine and reaction steam turbine
Turbine control and protection
Various turbine gearing -Epicyclic gearing,Helical gearing,Flexible coupling &Turning gear
Marine machineries - Useful tags
Marine diesel engines
||Steam generating plant
||Air conditioning system
||Emergency power supply
||Exhaust gas heat exchangers
||Feed extraction pump
|| Four stroke engines
|| Fuel injector
|| Fuel oil system
|| Fuel oil treatment
Lub oil filters
MAN B&W engine
Oily water separator
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Piston & piston rings
Sewage treatment plant
Starting air system
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Drydocking & major repairs
Deck machineries & cargo gears
|| Control and instrumentation
||Engine room safety