Download - BS4 Tjedan10 Reversing_part1
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 1/31
Essential reading:
SPINĈIĆ, A., PRITCHARD, B., An English Textbook For
Marine Engineers 2 ., Pomorski fakultet, Rijeka 2009.LUZER, J., SPINĈIĆ, A., Gramatička vježbenica engleskog
jezika za pomorce, Pomorski fakultet, Rijeka 2003.
Tomislav Skračić, MA
Undergraduate English
Course for
MARINE ENGINEERS
4th Semester
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 2/31
Lesson 9
REVERSING
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 3/31
Lesson 9
Reversing
KEY WORDS
gearbox - kutija mjenjaĉa, reduktor, kopĉa
direct reversing - direktno prekretni
retiming angle - kut podešavanja
dog coupling - zupĉasta spojka
rest (n.) - mirovanjestop segments - graniĉni segmenti axially - uzdužno
slide the camshaft axially - uzdužno pomicati bregastu osovinu klizanjem
tappet roller - valjak podizaĉa
inclined surface - kosa površina
follower rollers - kotaĉići vodilice podizaĉa displacement (n.) - premještanje
hydraulic ram - hidrauliĉni klip
pneumatic control - kontrola s tlakom zraka
rotating vane - rotaciono krilo
relief pipe - ispusna cijev
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 4/31
VESSELS MAY MOVE:
Ahead
Astern
Sideways (Athwarthships)
Lesson 9
Reversing
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 5/31
Vessels may change the direction of movement(ahead to astern and vice-versa) by means of:
1) Controllable pitch propeller (CPP)
2) Direct reversing
3) Reversing gearbox
Lesson 9
Reversing
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 6/31
Controllable pitch propeller (CPP)
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 7/31
A controllable-pitch propeller is made up of a boss
with separate blades mounted into it. An internal
mechanism enables the blades to be moved.
Where CPP is in use there is no requirement toreverse the main engine.
1) Controllable pitch propeller (CPP)
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 8/31
Controllable pitch propeller (CPP)
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 9/31
The engine must be started in reverse and the fuelinjection timing must be changed.
Reversing is easier in 2-stroke engines.
In 4-stroke engines, the position of the camshaft to
the crankshaft is changed by a servomotor .
The camshaft is slided axially, bringing into use a
different set of cams.
2) Direct reversing
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 10/31
Direct reversing
- arrangements
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 11/31
Lost motion
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 12/31
The fuel pump cam and lost-motion clutch
arrangement is shown in the Figure above. The
shaping of the cam results in a period of pumping
about 10° of fuel injection before TDC and about 5°
after TDC. A period of dwell then occurs when thefuel pump plunger does not move.
A fully reversible cam will be symmetrical about
this point, as shown. The angular period between the
TDC points for ahead and astern running will be the'lost motion' required for astern running. The lost-
motion clutch or servo motor uses a rotating vane
which is attached to the camshaft but can move in
relation to the camshaft drive from the crankshaft. Thevane is shown held in the ahead operating position by
Direct reversing - arrangements
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 13/31
When oil is supplied under pressure through the drain,
the vane will rotate through the lost-motion angular
distance to change the fuel timing for astern
operation. The starting air system is retimed, either
by this camshaft movement or by a directional airsupply being admitted to the starting air distributor, to
reposition the cams. Exhaust timing or poppet valves
will have their own lost-motion clutch or servo motor
for astern timing.
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 14/31
Lost motion clutch
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 15/31
1) The auxiliary blowers, where manually operated,should be started.
2) Fuel is shut off from the engine.
3) Blasts of compressed air may be used to slow the
engine down.
4) When the engine is stopped the direction handle is
positioned astern.
5) Compressed air is admitted to turn the engine astern and fuel is admitted to accelerate the engine. The
compressed air supply will then cease.
Engine reversing procedure
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 16/31
Where the shaft speed of a medium-speed dieselengine is not suitable for direct reversing, e.g. where a
low speed drive for a propeller is required, a
gearbox must be provided. Between the engine and
gearbox it is usual to fit some form of flexible coupling to dampen out vibrations. There is also often a need for
a clutch to disconnect the engine from the gearbox.
The engine itself is not reversed if the reversing gears
are incorporated.
3) Reversing gearbox
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 17/31
Gearbox
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 18/31
Gearbox
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 19/31
The gearing arrangement used to reduce the medium-
speed engine drive down to suitable propeller
revolutions is always single reduction and usually single
helical. Reduction ratios range from about 2:1 to 4:1
on modern installations.
Gearbox
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 20/31
Couplings
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 21/31
Elastic or flexible couplings allow slight misalignmentand damp out or remove torque variations from theengine. The coupling may in addition function
as aclutch or disconnecting device.
Couplings may be mechanical, electrical, hydraulic or pneumatic in operation. It is usual to combine thefunction of clutch with a coupling and this is notreadily possible with the mechanical coupling.
Couplings
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 22/31
Couplings
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 23/31
Hydraulic couplings
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 24/31
The hydraulic or fluid coupling uses oil to connect
the driving section or impeller with the driven section
or runner . No wear will thus take place between these
two, and the clutch operates smoothly. The runner and
impeller have pockets that face each other which arefilled with oil as they rotate. The engine driven impeller
provides kinetic energy to the oil which transmits the
drive to the runner. Thrust bearings must be provided
on either side of the coupling because of the axialthrust developed by this coupling.
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 25/31
A clutch is a device to connect or separate a drivingunit from the unit it drives. With two enginesconnected to a gearbox a clutch enables one or bothengines to be run, and facilitates reversing of the
engine.
Clutch
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 26/31
Clutches
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 27/31
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 28/31
The turning gear or turning engine is a reversible
electric motor which drives a worm gear which can be
connected with the toothed flywheel to turn a large
diesel. A slow-speed drive is thus provided to enable
positioning of the engine parts for overhaul purposes.The turning gear is also used to turn the engine one
or two revolutions prior to starting. This is a safety
check to ensure that the engine is free to turn and that
no water has collected in the cylinders. The indicatorcocks must always be open when the turning gear is
operated.
Turning gear
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 29/31
a) R & D Marine has developed a wide ____________ offlexible couplings to fit all major installations.
b) The R & D flexible couplings reduce engine ____________,vibration transmission and are designed to accept propeller
____________.c) The couplings are made from a polyester elastomer which is
not affected by ____________, diesel and lubrication fluids.
d) Installation is quick and easy as the R & D coupling requiresno ____________ and comes supplied with bolts to connectbetween the two existing shaft ____________.
e) Checking alignment on installation and during ____________ checks is quick and easy using the red coneheaded bolt.
Exercise 1 – Fill the gaps with the suitable expressions:
flanges, machining, noise, range, salt water, service,
thrust.
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 30/31
a) R & D Marine has developed a wide range of flexiblecouplings to fit all major installations.
b) The R & D flexible couplings reduce engine noise, vibrationtransmission and are designed to accept propeller thrust.
c) The couplings are made from a polyester elastomer which isnot affected by salt water, diesel and lubrication fluids.
d) Installation is quick and easy as the R & D coupling requiresno machining and comes supplied with bolts to connectbetween the two existing shaft flanges.
e) Checking alignment on installation and during service checks is quick and easy using the red cone headed bolt.
Exercise 1 – KEY
8/11/2019 BS4 Tjedan10 Reversing_part1
http://slidepdf.com/reader/full/bs4-tjedan10-reversingpart1 31/31