BAB I
UDARA
START MESIN INDUK
(Main Engine of Starting System)
Untuk mesin induk diatas kapal, baik diesel 4-tak maupun
2-tak digunakan udara untuk start engine, udara ini diproduksi dari air
compressor dan ditampung di bejana udara (air reservoir). Tekanan kerja untuk
udara start ini dimulai dari tekanan 25 - 30 bar. Menurut SOLAS, bahwa untuk
mesin digerakkan langsung tanpa reduction gear (gear box) harus dapat distart
12 kali tanpa mengisi lagi, sedangkan untuk mesin -mesin dengan gear box dapat distart
6 kali.
1. Bagian
- bagian utama dari penataan udara start dan fungsinya masing-masing :
- Bejana udara (air reservoir) berfungsi sebagai tabung pengumpul udara.
- Main starting valve berfungsi sebagai katup penyalur untuk pembagi ke masing - masing cylinder head dan penyalur udara untuk start.
- Distributor valve berfungsi sebagai pembagi pada katup udara start (air starting valve) yang bekerja menggunakan plunger.
- Air starting valve berfungsi sebagai katup supply udara di cylinder head untuk menggerakkan piston kebawah pada saat langkah expansi (baik diesel 4 tak maupun 2 tak)
2. Prinsip
kerjanya
Untuk
start engine baik pada saat kapal berangkat ataupun saat olah gerak,
dilaksanakan sebagai berikut :
- Udara dari bejana udara minimal 17 kg/cm2 (17 bar) karena bila tekanan udara dibawahnya, maka udara tersebut tidak mampu menekan piston kebawah.
- Katup tekan di bejana udara dibuka penuh, maka udara akan keluar ke main starting valve. Setelah udara tersebut direduksi tekanannya hingga ± 10 bar.
- Bila handle start ditekan kebawah, maka udara keluar dari system sebagian masuk dulu ke distributor valve dan sebagian lagi ke cylinder head air starting valve. Udara start ini diatur oleh distributor valve dengan tekanan 10 bar mana yang bekerja pada proses expansi (hanya ada 1 silinder yang bekerja) melalui plunyer yang dihubungkan dengan firing ordernya (misalnya motor diesel 4 tak adalah -.1-5-3-6-2-4).
- Distributor valve mengatur plunyer yang bekerja dan udara ini langsung menggerakkan piston melalui air starting valve di cylinder head. Udara supply ini diperoleh dari bejana udara. Jadi udara tersebut melaksanakan kerja parallel, disamping mengatur ke distributor valve sekaligus untuk udara start mendorong piston kebawah pada tekanan minimal 7 bar sesuai tekanan dalam botol angin.
Kesimpulan
- Untuk membuka air starting valve menggunakan udara reduksi yang mengatur distributor valve.
- Setelah air starting valve terbuka, maka udara start dengan tekanan sesuai pada tekanan kerja dibotol angina masuk silinder motor melalui air starting valve yang terbuka untuk mendorong piston kebawah (TMB), sehingga mesin dapat dijalankan. (ON).
ENGINE
STARTING
Valves
(63) and (64) are de-activated, the puncture
valves of the F.O. pumps are vented, and fuel injection is started. After
a time delay of about 1 second, valves (26) and (27) are vented.
After a time delay of
about 6 seconds valves (10) and (92) are
vented. Hereby the speed' setting air signal to the governor is changed from
the pre-speed setting signal to the normal speed setting signal set by the
regulating handle via the regulating valve (62).
This 6-second time
delay enables the governor to stabilize the engine at slow level RPM before
regulating to a higher or lower RPM.
Start in ASTERN
direction follows the same procedure.
If
the engine has been stopped for a long term, it is recommended to TURN the
engine at least one revolution before starting.
1. Emergency Control from Emergency Console
on Engine
In
case of break-down of the normal pneumatic manoeuvring system, or the governor,
the engine can be operated from the emergency console on the engine.
Changing-over
from NORMAL to EMERGENCY is carried out by turning e change over handwheel
anti-clockwise, whereby the governor is disconnected from the fuel pumps,
and the regulating handwheel on the emergency console is connected to them.
Furthermore, valve (100) has to be changed from NORMAL to EMERGENCY. Before
changing-over this valve, it has to be checked that valve (105) is in the
required position (AHEAD or ASTERN).
Start
is carried out as follows: Before the start, set the regulating handle to START
position (start index). By pressing down the valve (101), the engine starts air
running. When starting level RPM has been reached, release the valve (101), and
the engine will run on fuel. Speed regulation during fuel running is made by
regulating the handle watching the tachometer. When stopping the engine, press
down the valve (102).
Reversing
is carried out by activating valve (105), which reverses the displaceable
rollers for the fuel pumps as well as the starting air distributor. Reversing
is only possible when the valve (102) is activated.
2. Manoeuvring
After completion of
the above-mentioned preparations, the engine is ready for starting.
Plate 70302.
The
following modes of control are available:
A. Automatic
Control from Bridge
B. Manual
Control from Control Room
C. Emergency
Control from Emergency Console on Engine
A. Automatic
Control from Bridge
Valve (80) in the
control console must be changed to BRIDGE CONTROL position.
Start
in AHEAD direction
During engine stopped condition the solenoid valve (84)
is activated. When the bridge telegraph handle is moved from STOP to a position
in the AHEAD field, the solenoid valves (86) and (90) are automatically
energized:
The pneumatic manoeuvring system gives a pre-speed
setting signal (about 2.0 bar) to the governor, whose terminal lever turns to a
certain position.
As the puncture valves of the F.O.
pumps are activated also during START.
Valve (26) supplies pilot air to the starting air
distributor.
When
the starting level RPM has been reached, valves (90) and (84) are de-energized,
the puncture valves of the F.O. pumps are
vented, and fuel injection is started.
After
about 6 seconds, the pre-speed setting signal will change to the speed setting
set by the bridge telegraph.
This
delay enables the governor to stabilize the engine at slow level RPM before changing
to a higher or lower speed setting.
Repeated
Start: If the engine fails the first start, a new start
attempt (repeated start) will take place automatically after an interval of
about 6 seconds. After 3 start attempts, the system locks. In the event of
repeated start, the limitations in the governor are automatically cancelled,
and the governor will effect a higher index on the fuel pumps. In order
to re-set the start locking, the telegraph handle must be set back to STOP.
Reversing:
(from
AHEAD to ASTERN)
The bridge telegraph handle is moved to the wanted field
in the ASTEN range. When engine revolutions are higher than the reversing
level, solenoid valve (84) is activated, and the fuel pumps brought to FUEL OFF
by the puncture valves. Also the valve (88) reverses the
starting air distributor by activating the reversing cylinder (57), and the
displaceable rollers by activating the reversing cylinders (13).
When
engine revolutions reach the reversing level or are below the reversing level,
solenoid valves (90) is activated.
As
soon as the starting air distributor is reversed, valve (56) will allow the
starting signal from valve (90) to pass, and activate the ball valves for
starting air.
The engine will stop
and start rotating in ASTERN direction. The sequence will continue as described
under "Start in AHEAD direction".
B.
Manual
Control from Control Room
Valve
(80) in the manoeuvring console has to be changed to ENGINE ROOM position.
Start in AHEAD direction
Place the telegraph handle in AHEAD position, whereby the
AHEAD valve (70) in the telegraph is activated.
An
air signal is led via the double non-return valve (29), the signal is divided
in two, one signal will change the position of valve (10), the other signal is
led via the valves (55) and (50) to the valve (37). The signal can pass the
valve (55) only when the distributor position is at AHEAD.
As
long as the regulating handle is in a position between STOP and START
inclusive, valve (64) is activated and leads an air signal to
activate
valves (38) and (117).
Valves
(10) and (11) supply air for reversing of the displaceable rollers of the
individual fuel pumps, and air for reversing the sir cylinder (57) for the
starting air distributor.
The
regulating handle is now placed in START position, and the valve (63) is
activated. This leads an air signal to valve (31) via the valve (37), and then
to valves (26) and (27).
Valve (92) leads a speed-setting air signal (about
2.0 bar) to the governor (42) whose terminal lever turns to a certain position.
As also the puncture valves of the F.O. pumps
are activated at START.
By
the activation of valves (26) and (27), the starting air is led to the
distributor and the engine starts to run by air. When the RPM level for
starting has been reached, the regulating handle is moved to a position in the
FUEL SUPPLY area.
Valves (63) and (64) are de-activated, the puncture valves of the F.O. pumps are vented,
and fuel injection is started.After a time delay of about 1 second,
valves (26) and (27) are vented.
After a time delay of
about 6 seconds valves (10) and (67) are vented. Hereby the speed setting air
signal to the governor is changed from the pre-speed setting signal to the
normal speed setting signal set by the regulating handle via the regulating
valve (62).
This 6-second time
delay enables the governor to stabilize the engine at slow level RPM before
regulating to a higher or lower RPM.
Start in ASTERN
direction follows the same procedure.
If
the engine has been stopped for 30 minutes or more, it is recommended to TURN
the engine at least one revolution before starting.
C.
Emergency
Control from Emergency Console on Engine
In
case of break-down of the normal pneumatic manoeuvring system, or the governor,
the engine can be operated from the emergency console on the engine.
Changing-over
from NORMAL to EMERGENCY is carried out by turning the. change over handwheel
anti-clockwise, whereby the governor is disconnected from the fuel pumps, and
the regulating handwheel on the emergency console is connected to them.
Furthermore, valve (100) has to be changed from NORMAL to EMERGENCY. Before
changing-over this valve, it has to be checked that valve (105) is in the
required position (AHEAD or ASTERN).
Start is carried out
as follows: Before the start, set the regulating handle to START position
(start index). By pressing down the valve (101), the engine starts air running.
When starting level RPM has been reached, release the valve. (101), and the
engine will run on fuel. Speed regulation during fuel running is made by
regulating the handle watching the tachometer. When stopping the engine, press
down the valve (102,).
Reversing is carried
out by activating valve (105), which reverses the displaceable rollers for the
fuel pumps as well as the starting air distributor. Reversing is only possible
when the valve (102) is activated.
