Harbour Tug

Kapal tunda adalah kapal yang dapat digunakan untuk melakukan manuver / pergerakan, utamanya menarik atau mendorong kapal lainnya di pelabuhan, laut lepas atau melalui sungai atau terusan. Kapal tunda digunakan pula untuk menarik tongkang, kapal rusak, dan peralatan lainnya.

Kapal tunda memiliki tenaga yang besar bila dibandingkan dengan ukurannya. Kapal tunda zaman dulu menggunakan mesin uap, saat ini menggunakan mesin diesel. Mesin Induk kapal tunda biasanya berkekuatan antara 750 sampai 5000 tenaga kuda (500 s.d. 3500 kW), tetapi kapal yang lebih besar (digunakan di laut lepas) dapat berkekuatan sampai 25 000 tenaga kuda (20 000 kW). Kebanyakan mesin yang digunakan sama dengan mesin kereta api, tetapi di kapal menggerakkan

baling-baling. Dan untuk keselamatan biasanya digunakan minimum dua buah mesin induk.
Kapal tunda memiliki kemampuan manuver yang tinggi, tergantung dari unit penggerak. Kapal Tunda dengan penggerak konvensional memiliki baling-baling di belakang, efisien untuk menarik kapal dari pelabuhan ke pelabuhan lainnya. Jenis penggerak lainnya sering disebut Schottel propulsion system (azimuth thruster/Z-peller) di mana baling-baling di bawah kapal dapat bergerak 360° atau sistem propulsi Voith-Schneider yang menggunakan semacam pisau di bawah kapal yang dapat membuat kapal berputar 360°.

Jenis kapal tunda

Kapal tunda konvensional / Towing or Pusher Tug
Kapal tunda serbaguna / Utility Tug
Kapal tunda pelabuhan / Harbour Tug

diantara ke tiga system yg termodern dan tercanggi ada di harbour tug, dan kapal supply modern atau yg mengunakan system Dinamic position system mesinnyapun hampir sama hanya mereka di lengkapi lebih bow truster. dalam DP system saat berkerja bisa menjalankan 5 mesin pengerak baling baling. kembali ke tug boat propulsion. yg kita bahas di topik ini.

Tugboat propulsion

Tugboat engines typically produce 500 to 2,500 kW (~ 680 to 3,400 hp), but larger boats (used in deep waters) can have power ratings up to 20,000 kW (~ 27,200 hp) and usually have an extreme power:tonnage-ratio (normal cargo and passenger ships have a P:T-ratio (in kW:GRT) of 0.35 to 1.20, whereas large tugs typically are 2.20 to 4.50 and small harbour-tugs 4.0 to 9.5). The engines are often the same as those used in railroad locomotives, but typically drive the propeller mechanically instead of converting the engine output to power electric motors, as is common for railroad engines. For safety, tugboats' engines often feature two of each critical part for redundancy
A tugboat's power is typically stated by its engine's horsepower and its overall bollard pull.
Diagram with components namedTugboats are highly maneuverable, and various propulsion systems have been developed to increase maneuverability and increase safety. The earliest tugs were fitted with paddle wheels, but these were soon replaced by propeller-driven tugs. Kort nozzles have been added to increase thrust per kW/hp. This was followed by the nozzle-rudder, which omitted the need for a conventional rudder. The cycloidal propeller was developed prior to World War II and was occasionally used in tugs because of its maneuverability. After World War II it was also linked to safety due to the development of the Voith Water Tractor, a tugboat configuration which could not be pulled over by its tow. In the late 1950s, the Z-drive or (azimuth thruster) was developed. Although sometimes referred to as the Schottel system, many brands exist: Schottel, Z-Peller, Duckpeller, Thrustmaster, Ulstein, Wärtsilä, etc. The propulsion systems are used on tugboats designed for tasks such as ship docking and marine construction. Conventional propeller/rudder configurations are more efficient for port-to-port towing.
The Kort nozzle is a sturdy cylindrical structure around a special propeller having minimum clearance between the propeller blades and the inner wall of the Kort nozzle. The thrust:power ratio is enhanced because the water approaches the propeller in a linear configuration and exits the nozzle the same way. The Kort nozzle is named after its inventor, but many brands exist.
A recent Dutch innovation is the Carousel Tug, winner of the Maritime Innovation Award at the Dutch Maritime Innovation Awards Gala in 2006[1]. The Carousel Tug adds a pair of interlocking rings to the body of the tug, the inner ring attached to the boat, with the outer ring attached to the towed ship by winch or towing hook. Since the towing point rotates freely, the tug is very difficult to capsize.
The Voith Schneider propeller (VSP), also known as a cycloidal drive is a specialized marine propulsion system. It is highly maneuverable, being able to change the direction of its thrust almost instantaneously. It is widely used on tugs and ferries.
From a circular plate, rotating around a vertical axis, a circular array of vertical blades (in the shape of hydrofoils) protrude out of the bottom of the ship. Each blade can rotate itself around a vertical axis. The internal gear changes the angle of attack of the blades in sync with the rotation of the plate, so that each blade can provide thrust in any direction, very similar to the collective pitch control and cyclic in a helicopter.

Scope kerja dari harbou tug cukup banyak tergangtung dari permintaan pencarter. salah satu pelayanan yg di berikan sebagai berikut:
Typical services provided include:

1. Berthing, unberthing, handling of vessels and tankers including VLCCs, ULCCs, FPSO, FSO and LNG.
2. Positioning of oil rigs for jack-up / down or leg joining operations.
3. Loading and unloading of vessels, rigs and project cargoes from semi-submersible heavy lift ships.
4. Towing of floating cranes and barges.
5. Standby duties at disabled vessels.
6. Shifting of immobilized ships at anchorages.

7. Ship to ship transfer operations.
8. Tow out and load out of offshore structures and platforms.
9. SPM mooring and unmooring operations.
10. Firefighting (FiFi Class 1)
11. Anti-pollution clean up
12. Ship escort for safe passage via Malacca and Singapore Straits
13. Towage to neighboring ports

sebagai tambahan informasi , harbour tug saat ini yg banyak beroperasi di pelbuhanpelabuhan besar biasanya mengunakan system tractor dan ASD tug. dari dua jenis ini perusahaan pelayaran seperti "SVITZER, SMIT, LAMNALCO, PSA, DP WORD, IRSAD, DLL. banyak mengunaakan mesin type ASD tug.