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.
DAFTAR PUSTAKA
BAKAR, A, MT.,M.Mar.E, (2011), Mesin Penggerak Utama, Pustaka : Politeknik Ilmu Pelayaran Makassar.
Instruction Manual Book for Main Engine Pustaka : Mitsubshi Engineering.,Co.Ltd, Osaka
Nurdin, H, ( 2000), Mesin Penggerak Utama, Pustaka : Jakarta.
Penulis
ARDIANSYAH AB
