rms EMPRESS OF BRITAIN, 1930, Cold Starting
Canadian Pacific Steamships Ltd., Builders: John Brown, Clydebank
Canadian Pacific Steamships Ltd., Builders: John Brown, Clydebank
by Stephen Carey, editing by Earl of Cruise
rms EMPRESS OF BRITAIN - own collection
1 Overview of the machinery spaces
1.1 Boiler rooms
The ship is (or was) a quadruple screw Canadian
Pacific liner fitted with two Scotch fire-tube boilers at 200lb/in2,
one Johnson water-tube boiler and eight Yarrow 5-drum water-tube boilers,
operating at 425lb/in2, 725°F
superheated. In SI units this converts
to 13.8bar saturated (198°C) for the
Scotch boilers, and 29bar, 385°C
superheated. At 29bar the saturated
temperature is 234°C, so the
boilers operate at 151°C superheat.
The boilers are arranged in 2 boiler rooms,
one forward and one aft, separated by oil fuel tanks.
In the forward boiler room are the 2 Scotch
boilers, the Johnson boiler and two Yarrow boilers. In the aft boiler room are the remaining 6
Yarrow boilers. A profile and plan of
the boiler rooms is shown at Figure 15.
1.2 Oil bunkers
The boiler oil fuel bunkers are arranged
between the forward and after boiler rooms, and comprise 4 storage and 4
settling tanks. The latter separate oil
from water and other solids by gravity, and are regularly sludged to remove the
water prior to it being pumped to the boiler oil-firing apparatus. The oil-firing or burner pumps are arranged
between each pair of Yarrow boilers.
The 4 main steam pipes run the length of the
boiler rooms to the bulkhead stops in the centre engineroom for distribution to
the engines and auxiliaries.
1.3 Diesel fuel bunkers
Diesel fuel for the generators is stored in double
bottom tanks under the generator room.
The fuel from these tanks is drawn via the diesel transfer pumps located
midships and discharged into service tanks on the forward bulkhead of the
diesel generator room (aft of the after boiler room). There does not seem to be a diesel purifier
on the ship drawings, so presumably the reasonably clean bunker fuel was passed
to settling tanks to drain off the water – probably the two tanks shown on the
port outboard side – before being pumped to the service tanks. From there filtration would clean the fuel of
any other solid impurities prior to injection into the cylinders.
1.4 Propulsion engines
The propulsion system differs from the older
vessels in this series as the turbines are arranged for triple expansion in
each turbine set. The turbine sets each
comprise an hp, lp and ip turbine working each shaft. Astern turbines are fitted on the inner two
shafts only, the outer shafts being ahead running only. The reason for this is that the 2/3 of the
vessel’s propulsive power is provided by the inner sets of turbines working
together, with 1/3 power delivered by the two wing turbine sets operating
together.
The vessel is innovative in that she is
designed for transatlantic service on 4 shafts at maximum power in the winter
months, and for summer cruising on the inner turbine sets, with the propellers
removed from the outboard shafts. The
cruising speed of 18knots is achieved at about half the consumption of all 4
shafts running together, a very economical design.
The ship has a very comprehensive redundant
system for running the turbines together or in isolation, but we will explain
the normal triple-expansion arrangement later.
1.5 Main steam piping (see Figure 1)
Each bank of three boilers in the after
boiler room supply a steam line (2 lines in all) and two steam lines from the
forward boiler room carrying the combined output of the three forward boilers.
Steam from these four main steam pipes passes
through the diesel generator room and enters the forward engineroom via
bulkhead stop valves operated by Brown’s engines and governors from the
turbines, which shut off the steam supply in the event of turbine overspeed.
From the stop valves, the outer steam pipes
pass to the two turbine sets in the forward engineroom, the inner two pipes
pass through the forward engineroom to the bulkhead stops on the after
engineroom bulkhead. From the stop
valves on both the forward and after engineroom bulkheads, the steam passes to
the turbine manoeuvring valves in each section.
The steam passes through each turbine stage
and finally exits to the condensers from the lp turbine exhausts.
This exhaust steam from the low-pressure
turbines is directed to the four vacuum condensers, situated under each of the
four turbine sets, where it is condensed into feed water and pumped back into
the boilers.
Manoeuvring from ahead to astern is carried
out solely using the forward engineroom ahead and astern turbines, with the
wing turbines – which do not have astern turbines - used for working up to full
speed on North Atlantic service. The
turbines may be isolated in case of breakdown.
For cruising operations in the summer months,
the outboard engines are not used, the shafts having their propellers removed
to reduce drag. This results in a
significant reduction in fuel consumption at the expense of unnecessary speed,
the latter only being required on the North Atlantic run.
Regulating valves, driven by worm and
quadrant gear via spindles operated from the starting and manoeuvring platform,
admit steam to the engines as required by the telegraph orders.
Figure 1 rms EMPRESS OF BRITAIN Plan of steam piping in enginerooms
1.6 Gearboxes
Unlike the previous two turbine-driven ships,
which were direct drive owing to the slower speed of the turbines with
low-pressure saturated steam, this vessel has single reduction gearing via four
gearboxes, one for each shaft, to cope with the speed of the turbines under
superheated high pressure steam conditions.
1.7 Electrical power generation
i Emergency generating sets
The vessel is fitted with two emergency diesel
generators of 75kW each for emergency lighting, wireless telegraphy as well as
some power circuits. These machines
could be used to cold start, providing the emergency switchboard has a
connection for the FD fans, but with main diesel generators available, this is
unlikely.
The generators, when running under loss of
main power, have a charging capability for the main and ‘panic’ battery banks.
The generators are electric start, so the
engineers would start these machines and put them on the board, at the same
time opening the shore power breaker.
Once the engines are started and put on the
board, the various circuits required for starting the main generators are
energised, up to the capacity of the emergency switchboard.
Figure 2 rms EMPRESS OF BRITAIN Emergency generator set
ii Emergency switchboard
Attached to this board are the emergency distribution
circuits. On this age of ship these are
generally confined to -
- Emergency lighting (throughout the ship)
- Transient lighting (control panels and operating
stations)
- Wireless telegraphy
- Small power (probably ventilation fans for
accommodation and other hotel services)
- Battery charging (main and “panic” banks)
Figure 3 rms EMPRESS OF BRITAIN Emergency switchboard
Figure 4 rms EMPRESS OF BRITAIN Emergency distribution system
iii Main diesel generating sets
The
vessel is fitted with four 450kW 225Vdc diesel generators situated in the
generator room between the after boiler room and the forward engineroom. These are large crosshead type engines, single-acting
and with blast (air) injection, as opposed to the modern methods of fuel
injection. A photo of one of the engines
is shown below.
Figure 5 rms EMPRESS OF BRITAIN One of the diesel generating sets
iv Turbo-Generator sets
In addition, there are two single-reduction
geared turbo-generators driven by BTH steam turbine prime movers at 6000rev/min,
each of 800kW 225Vdc. These sets are
situated on turbine flats, one either side of the forward engineroom bulkhead,
arranged longitudinally. The main and
auxiliary switchboards are situated in a switchboard room on E Deck, above the
diesel generator room.
Steam at a pressure of 375lb/in2 and
700F is fed to the turbines and exhaust steam is directed in port or at start
up to the auxiliary condensers. At sea
the exhaust steam is directed to the feed heaters to extract the remaining
energy from the exhaust steam and deliver it to the feed heating system. This configuration gives a total installed
power of 3.4MWdc, with adequate stand-by redundancy.
Without knowing the actual full load of the
vessel, the redundancy could be 2x100%, i.e. one turbine and two diesels (1.25MW)
or 4 diesels (1.8MW) or two turbines (1.6MW).
This sounds a reasonable load for such a ship, but the arrangement could
be any permutations depending on the load.
Whilst cruising on the centre shafts, the propulsion load would be less
and therefore the electrical load would also be less, though if air
conditioning was fitted for summer cruising, the additional load could take up
the reserve.
2. Starting the main diesel generating sets
Unlike the other ships in the series, the
fitting of main diesel generating sets only requires sufficient starting air to
get the main power up and running, so there is no need to start firing boilers
at this stage using the emergency sets.
If starting air is not available, the auxiliary starting air compressor
is started off the emergency supply and the starting air bottles charged
up. The main diesels are fitted with an
engine-driven seawater cooling pump for the jackets and oil coolers; not really
a good idea as seawater is highly corrosive, especially so at the running
temperature of a diesel. Nowadays
engines are cooled by a central fresh water system, which is in turn cooled by
raw seawater.
The engines are therefore self-contained,
with the fuel supply being gravity fed from the diesel oil service tanks
mounted on the generator room forward bulkhead.
Once the engine turns over on air and fires, the cooling and lube oil
systems start as they are also engine-driven.
A compressor on one end of the engine shaft generates compressed air for
the blast injection. The scavenge air
compressor (an early method of increasing the combustion air pressure prior to
the advent of turbo-charging) is mounted on the other end to balance the forces
and reduce vibration.
Main power is then available and the main
breakers are closed onto the main switchboard.
At this stage, all the power required for
starting the ship is available, with a turbo-generator being started once steam
is available. As the main switchboard
seems to be split with a turbo-generator and two diesels on each side of the
board (see Figure
7), we will only start two diesels (port inner and
outer) to give us 900kW of power available.
Below is a section through the diesel engine space showing the arrangement
of the engines 4 abreast, diesel tanks, air compressor and diesel transfer
pumps. Of interest are the spare
crankshaft and armature, probably carried for when the ship is cruising far
from her home ports.
Figure 6 rms EMPRESS OF BRITAIN Selection through auxilliary ER, looking forward
2.1 Main Switchboard distribution
The main switchboard is divided into sections
in order to distribute the power to the various areas of the ship. Most of the auxiliaries are electric drive
and the breakers for these can be seen on the board. On Direct Current the breakers for the
generators (all six are shown on the diagram) can be put straight on to the
board (with the shunt field regulator wound right down) - there is no need to
synchronise as with an alternating current system. The shunt field regulator is then wound up to
share the load with the other generators on the board. The board has two sections split by a bus-tie
breaker, which bears out the 2x100% redundancy in that a turbine generator is
seen on each side, paired with two diesel generators.
Of interest is the size of the Shore Power at
1,000A, corresponding to 225kW, and the 1500A Galley breakers corresponding to 337.5kW
– quite a large galley load as expected on a passenger ship of this size. If AC power had been available in 1931, the
electrical current load with a 3-phase 440V 60Hz supply would have been
considerably less, as the required power would result in a much lower current
and therefore a much reduced cable size and volt drop. For the same galley power of 337.5kW on an AC
supply, the current would be around 553A, approximately 37% of the dc current
shown.
An interesting note in a 1927 marine engineering
book states, “There is no foreseeable future for alternating current in
ships”. Fortunately, marine engineers
are forever endeavouring to achieve greater power and economy from the
machinery they design, have ignored that statement and alternating current is
now the standard in ships.
Figure 7 rms EMPRESS OF BRITAIN Main switchboard distribution
3 Firing up the boilers
We now have power available for the engineers
start the forced draught fans from the main switchboard.
Once the air is established the firemen start
an oil-fuel unit (electric drive) and light up the boilers, assuming there is
sufficient water level. If there isn’t
sufficient level, there are two sets of electrically driven auxiliary feed
pumps in the forward boiler room, which can be used to establish a level in all
the required boilers. It is likely that
there is also an electric “cold-start” feed pump in the engineroom, but this is
not shown on the drawings.
Once lit, dampers adjust the boiler draft and
the fires start to heat the water in the water-tube boilers. Water-tube boilers are much more efficient
and faster starting than fire-tube, but would still take around 7-10 hours to
raise steam to manoeuvring pressure from cold.
Firing boilers is carried out in stages to avoid thermal shock to the
tubes and boiler drums, with the superheater starting valve open, along with
the vents on top of the drums to dispel any air. Additionally the main stop on the first boiler
(usually furthest away, so in the forward boiler room) is open in order to
drain the main steam lines as pressure is raised.
As the pressure rises and steam is issuing
from the steam drum vents they are closed, with the superheater starting valve
left open to ensure a steam path through the superheater banks to avoid
damaging the tubes.
As steam is raised on the boiler which has
its main stop valve open, the drains along the whole length of the main steam
lines to the enginerooms are opened up to drain any condensate, as liquid
entering the turbine machinery can cause damage.
4 Main condensers and seawater circulating pumps
Once steam is raised and up to sufficient
pressure to start a turbo generator (around 375lb/in2) at the main
stops, the bulkhead stop valves to the main steam lines in the enginerooms are
opened to drain condensate from the lines serving the turbo-generators. The remaining main stop valves of the boilers
required to start a turbo-generator are cracked open to the main steam pipe and
the piping and valve drains opened to clear the lines of condensate, which can
damage reciprocating and turbine machinery.
Once steam is raised and is used, it has to
be returned to the boilers via the feed system.
It is not very clear from the simplified feed drawing in the book how
the feed system actually works regarding the exhausts from the turbo main feed
pumps (TMFP) or the exhausts from the turbo-generators. It can be reasonably assumed however, that
the auxiliary condenser situated on the starboard side of the forward boiler
room is both too far away and not large enough to handle either of the exhausts
from this machinery as in the earlier ships in this series, so the main
condensers will need to be put into service.
As a more modern ship, the main seawater
circulating pumps are electric drive, and there are 3 sets of 2 of these
fitted,
- one pair either side of the forward
engineroom thrust blocks
- one pair either side of the forward
engineroom underneath the turbo-generators
- one pair inboard of the centre shafting in
the after engineroom.
The
main circulating pumps for the inner shaft turbines are started and supply
seawater to the condensers under each turbine set, with the discharge sent
overboard. At the same time, and to
achieve the vacuum in the condenser by removing air and other non-condensables,
there are steam driven air ejectors fitted to all four turbine sets, the
forward engine room sets placed either side of the forward end of the turbines,
the after set inboard of the centre shafts in the after engineroom, serving the
two wing turbine condensers. These ejectors
use steam through a venturi arrangement to create a vacuum in the condensers.
Figure 8 rms EMPRESS OF BRITAIN One of the main SW circulating pumps and it´s starter (aft ER)
5 Starting a turbo-generator
We are now ready to start a turbo-generator
and will start the port turbo-generator, to serve with the two portside diesel
already on the board in accordance with the electrical schematic.
The exhaust from the turbine is opened to the
main condensers. As the turbo-generators
are in the forward engineroom, it is likely that the condensers under the inner
shaft turbines are used, not the after engineroom condensers, though there may
be bypass lines. The seawater passing
through these condensers condenses the exhaust steam into water, thereby
dropping its pressure and creating a vacuum.
Without this the turbine would trip on high exhaust backpressure, as the
exhaust steam has nowhere to go.
The turbine bearings are lubricated with oil,
so the stand-by LO pump is started and lubricating and control oil pressures
established. The control oil is used to
shut down the turbine in the event of LO pressure failure by holding open the
control valve whilst the pressure is maintained. Once the turbine is running, a shaft-driven
pump maintains the oil pressure. The oil
system is supplied with oil coolers and filters to maintain the temperature and
cleanliness within normal limits.
With all the lines drained to the turbine,
the stop valve is opened and the control valve drained through. Steam is now available right up to the
turbine inlet, and opening the throttle valve will allow the turbine to turn,
slowly gathering speed until it as full revolutions. The turbine sets incorporate single-reduction
gearing to reduce the electrical generator end speed to suit the supply
voltage.
The turbine control valve should now allow
itself to stay open unaided, held by the governor oil supply from the control
oil system. Speed control is therefore
automatic via the governor and the throttle valve. Usually the turbine trip is now tested, by
closing off the control oil to the throttle valve; loss of control oil pressure
should trip the valve. Once proved, the
system is reset and in operation.
Once up to speed, the generator main
switchboard breaker is closed and the shunt field regulator adjusted to share
the load with the two diesels. There is
now 1.7MW of power available for getting the ship underway.
As we are now consuming steam, we will also need
to start the main feed pumps to supply the boilers with feed water as required. The steam that is consumed by the
turbo-generator is being condensed as above into the condenser hotwell, and the
condensate extraction pumps (called “Pervac” pumps in the drawings) under the
condensers are started in order to maintain the correct condenser hotwell water
level. The feedwater and condensate
system is explained below.
6 The feed water and condensate system (see Figure 8)
The feed and condensate system is designed to
extract the maximum energy from the steam and return the heated feed back to
the boilers at the maximum design temperature.
Steam from the condensers that has condensed
into the hotwells under the condensers is returned to the boilers via two feed
heaters using the sets of condensate pumps (called “Pervac” pumps on the
drawing) located in a well below the tanktop and outboard of the lp turbines. These pumps deliver the condensate via the Drains Coolers located at the forward
end of the engineroom between the Forced LO pumps and their starters on the
forward bulkhead. These drains coolers
are fed with exhaust steam from the Primary Feed Heaters, mounted outboard in
each diesel generator room, and this exhaust heats the feedwater passing
through the shell and tube heating elements.
From the outlet of the drains coolers the
feed water is passed to the suction of the Turbo
Main Feed Pumps (TMFP), which are arranged in two sets of two pumps,
outboard at the forward end of the engineroom.
The TMFP then delivers the feed in series
through the Primary and Secondary Feed Heaters before delivery to the boiler
feed control valves. The secondary heaters
are also situated outboard in the diesel generator room, forward of the primary
units.
The Secondary
Heater is heated by bled steam from a turbine stage at 110lb/in2(a),
140F superheat and exhausts to the Primary Heater, along with some auxiliary
drains.
The Primary
Heater is also fed from a turbine stage at 30lb/in2(a) as well
as the exhaust from the Secondary Heater mentioned above, and exhausts to the
Drains Cooler as above, which in turn drains to the feed tanks mounted either
side on the forward bulkhead.
Appropriate recirculating piping is supplied to return feed water back
to the hotwell depending on boiler load conditions.
Of special
note in the feed arrangements for the forward engineroom (the after engineroom
is similar) are the Scotch boilers.
These have a set of feed pumps that draw from the Auxiliary Feed Tank
and discharge through the Auxiliary Feed Heater, termed “Greasy Exhaust Heater”
in the feed diagram. Auxiliary drains go
to this tank via the Auxiliary Condenser.
From the heater, the water is directed to the Scotch boilers, and the
“clean steam” so generated is delivered at 200lb/in2 to a turbine
stage. A line from this clean steam pipe
also leads to the auxiliary drains cooler, which supplies the heating medium
for the feed heater, whose drains are returned to the Auxiliary Feed Tank. All this equipment is situated outboard of
the starboard Scotch boiler in the forward boiler room. One can’t help wondering what these
contaminated drains do to the internals of the Scotch boilers, but it is
assumed that there is some kind of Observation Tank and filter to separate any
oily drains.
With everything up and running, steam is
raised on all the boilers required for leaving port. 
Figure 9 rms EMPRESS OF BRITAIN The feed water and condensate system
7 Starting the main engines
We now have more than enough power for firing
all the boilers necessary for starting the main engines and getting the
enginerooms ready for sea.
First we have to get the propulsion exhaust
steam and feed systems arranged in a similar way to that of the generators,
with each turbine set more or less similar.
As the turbine sets are triple expansion, steam passes through each of the
hp, ip and lp stages and exhausts to the main condensers underneath the
turbines. For manoeuvring out of port,
only the forward engineroom sets are used, as they have astern turbines
configured in the set. The wing shaft
turbines are ahead capable only, and are therefore used to work up to full
speed on a transatlantic passage, and would be kept warmed through on “steam
spinning” until required. For cruising
the outer shafts have the propellers removed, so the turbines are not used for
this period, though the rotors will be turned regularly on the turning gear to
avoid sag.
7.1 Main engines (forward engine room)
By
this time the engineers (we assume we are not doing this on our own) will have
engaged the electric turning gear motors on all four shafts, as well as
starting the turbine motor-driven forced lube oil pumps arranged in sets of
three pumps forward of each of the two forward engineroom turbine sets. The oil filters and coolers are arranged aft
of the pumps.
Figure 10 rms EMPRESS OF BRITAIN The forced LO pumps in the forward (L) and aft (R) enginerooms
The engines are kept turning until required
for use, whence the gear is withdrawn to avoid damage to it in the event of
starting a turbine with it engaged.
Gland steam is assumed to have been fitted (no mention in the Engineer
& Shipbuilder reprint) and will be started up to extract leakage steam from
the turbine shaft glands, and condense it back to the hotwell drains. At this stage the turning gear is removed and
the engines turned on “steam spinning” ahead and astern to ensure all
condensate is drained and the turbines are ready for manoeuvring.
The turbines are kept warmed through ready
for manoeuvring and working up to speed on passage, with manoeuvring steam
admitted to the hp turbines with the drains full open until proved clear. In series, the exhaust steam from hp turbine
exhausts via the ip turbines and into the lp turbine sets. At first the main steam bulkhead stop valves
are cracked open until everything is warmed through, whence they can be fully
opened.
Once the turbine drains are emitting steam,
we can call the bridge and ask if the propellers are clear for a slow turn
ahead and astern on both inner shafts.
Once this is given, the turbine manoeuvring valves are set to the ahead
position (with the astern isolator closed) and the main steam regulating
control valve cracked open at the starting platform at the forward end of the
turbine room. Each engine turns ahead at
low revs. After a few turns of the
shafts ahead the regulating valve is closed and the astern isolator opened to
allow steam to the astern turbines on each shaft. Again the regulating valve is cracked open
and the astern hp turbine turns, with its exhaust to the ip astern turbine and
the ip exhaust to the lp astern turbines.
The shafts turn astern for a few revs at low speed.
We are about ready to go, and test the
communications between the engineroom, boiler rooms and bridge so that we are
ready for sea service. Around the same
time an engineer is dispatched to the steering engine room to warm start the
steering motors and test the rudder from midships to 30 degrees port, back to
30 degrees starboard then returning to midships.
Figure 11 rms EMPRESS OF BRITAIN Gauge panel at forward end of the turbines
8 Getting under way
In
response to the bridge signals on the engineroom telegraphs, the ahead/astern turbine
sets are manoeuvred accordingly as above and the ship departs her berth and
heads for the open sea.
8.1 High-pressure and intermediate-pressure turbines
Once the ship is up to full ahead, and prior
to full away, the steam is now passing from the boilers to the main steam
lines, through the hp turbines, into the lp turbines, then the lp turbines and
finally exhausting to the condensers, from where it is returned to the boilers
as above in a closed feed cycle.
On transatlantic service, the after engineroom
is now engaged and the outboard turbines and feed system put into service. Full power can now be worked up once full
away is rung on the telegraphs.
8.2 The starting plattforms
The
main engines and some of the auxiliaries such as the steering gear are started
from the Starting Platforms, of which there are one for each engineroom.
Figure 12 rms EMPRESS OF BRITAIN The forward ER starting plattform
At the after end of the platform are the
turbine manoeuvring valves, where the engineers stand facing the engines –
looking aft. The three main wheels shown
are the Astern Master Valve (sometimes called the Astern Isolator), which
physically stops astern steam being applied if the ahead wheel is open. Next is the Astern Manoeuvring Valve which,
providing the Master Valve is open, applies steam to the astern turbines. The outboard wheel is the Ahead Manoeuvring
Valve, which turns the ahead turbines.
Once Full Away rings off stand-by, the ahead valve is gradually opened
up until the turbines are at full speed ahead.
Various telegraphs are also shown for both engines and boiler rooms.
The Water Spray Controls shown are for
manually spraying water into the condenser to force the water level and improve
the vacuum when manoeuvring.
On the forward bulkhead are the isolators for
the after engineroom steam system, and the Forced LO control panels above the
drains coolers, shown in the photo below.
Figure 13 rms EMPRESS OF BRITAIN Speed regulators and ammeters for FL pumps
8.3 Aft engineroom starting plattform
Figure 14 rms EMPRESS OF BRITAIN Aft ER / engine room starting plattform
As
the after engineroom turbines are not used during manoeuvring, the controls
here are much simplified. A voice pipe
from the forward starting platform relays orders as required to the after
personnel. As the after engineroom
handles the outboard engines – which do not have astern running – the engines
are brought up to speed once full away is rung, but opening the main steam
shutoff valves either side of the drains cooler. Telegraphs, revolution counters, feed gauges
and a FL Pump panel similar to the forward station are provided.
Plates from the
publication “Ocean Liners of the Past,
Empress of Britain (1931)
(With notes to explain the various items of
equipment fitted)
Figure 15 rms EMPRESS OF BRITAIN Elevation and plan of boiler rooms up to the ER bulkhead
9 Profile and plan of boiler rooms
On the view in Figure 15 can be seen the extent of the forward
and aft boiler rooms. The Yarrow boilers
are installed 6 in the after boiler room, and the remaining 2 in the forward
boiler room.
Also shown in the forward boiler room are the
two Scotch boilers either side of the innovative Johnson boiler in the centre.
9.1 Uptakes
The
uptakes can clearly be seen, illustrating that the forward two funnels on this
vessel served the boilers with the aft funnel serving as a ventilation shaft
and engine hatch over the enginerooms.
9.2 Fuel oil tanks
Between
the two boiler rooms are the boiler fuel oil tanks, consisting of four storage
tanks and four settling tanks, with an access way between. Situated in the access way are the watertight
door hydraulic pumps.
9.3 Oil fuel units
Between each pair of Yarrow boilers can be
seen an oil-fuel unit. There is also one
unit inboard of the port Scotch boiler which serves the two boilers. Either this unit or more likely the one shown
adjacent to the evaporators on the port side would supply the Johnson boiler.
These units contain supply pumps, which draw
from the settling tanks, then pass the fuel through strainers and filters to
clean it before supplying it to the boiler burners.
9.4 Other auxilliary units
The Scotch boilers are used to evaporate raw
feed water, the steam produced being passed to an intermediate stage of the
main turbines. In the forward boiler
room can be seen two evaporators to make feedwater from seawater, and also a
distiller for producing feed water from condensed steam and/or fresh
water. An auxiliary condenser, pumps and
feed tank for serving the Scotch boilers is shown on the starboard side.
In the aft boiler room is an Oily Water
Separator, used to clean bilge water before discharge overboard. These were early units which made a token
attempt to clean the water, compared to the strict regulations nowadays on
marine pollution as published by the MARPOL guide which limits overboard
discharges to 15ppm oil in water.
Figure 17 rms EMPRESS OF BRITAIN Elevation of engine rooms
Figure 18 rms EMPRESS OF BRITAIN Plan of engine rooms
10 Elevation and plan of the enginerooms
The views in Figure 17 and Figure 12 show the forward and after enginerooms.
10.1 Diesel generator room
Starting at the forward end of the Diesel
Generator Room are the diesel service
tanks (treated fuel from the settling tanks located between the two boiler
rooms) plus some other smaller day tanks.
These supply clean fuel for the engines.
Next are the engines themselves, with the
Primary and Secondary Feed Heaters shown.
Note the spare generator crankshaft, which in
modern ships is not a capital spare item.
In 1931 perhaps even on a transatlantic voyage, the steam engineers
didn’t trust a diesel generator; this is often the case with steam engineers
even today!
10.2 Forward engine room
Passing through the door at the after end of
the diesel generator room, we enter the forward engineroom.
On the forward bulkheads can be seen the
feedwater tanks (called Hotwell tanks on the drawing), the Forced LO pumps and
their attendant oil coolers.
Above is the starting platform, the drains
coolers (against the forward bulkhead), air ejectors and the entrance to the
switchboard room over the diesel generator room. Also shown is a manoeuvring gear stand and
above this space the forced LO gravity tank which supplies LO by gravity if the
forced LO pumps fail, timed to give enough LO for the turbines to run down.
Moving aft, the turbine sets, condensers,
“Pervac Pumps” situated in a well, three General Service pumps and a distilled
water header tank are shown.
Under the turbines in the double bottom are
the Forced Lube drain tanks, and cofferdams.
The turbine thrust blocks are shown, as are
the centre shaftlines exiting through the watertight bulkhead into the after
engineroom.
Above the machinery can be seen ventilation fans
for the enginerooms.
10.3 Aft engine room
In this room are the wing turbines,
condensers and auxiliaries for the turbine operation.
Starting at the forward bulkhead, the inner
shafts can be seen exiting through the bulkhead and passing through the space.
On the centreline is the hotwell tank (feed
tank), Drains Cooler and Feedwater Filters.
Outboard are two distilled water tanks, one on each side. Either side of the centreline are the Primary
and Secondary Feed Heaters for the after feed system.
Moving aft are the outer shaft wing turbines,
on the centreline are the TMFP for the after feed system and between the inner
shafts are the steam air ejectors, the “Pervac” pumps (condensate pumps) and a
Fresh Water pump.
Aft of these and still within the inner
shafts are the Forced Lube pumps mounted on the FL tank on the centreline, the
two main seawater circulating pumps and two general service pumps. Above is a switchboard.
Mounted outboard of the engineroom are two
calorifiers for heating domestic water and two swimming pool filtration units
on the port after bulkhead.
From this area, the four shafts exit to the
shaft tunnels.
10.4 Shafting and propellers
The two inner propulsion shafts are arranged
in the shaft tunnels and exit the ship via the stern tubes. There are several intermediate bearings
(Plummer Blocks) along the length of the shafting, which are splash lubricated.
The outer pair of shafts exit the hull in pods
which are supported by shaft brackets to the hull structure.
Figure 19 Shaft of a large liner
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