Azimuth thrusters are electric podded drive systems, which are
mounted on a 360 degree rotating shaft under the ship. There is no rudder
required in an azimuth system and hence, the underwater dynamics are improved
which not only increases manoeuvrability, but azimuth thrusters also include
the advantages of combined engine systems. Tugs and supply boats, where precise
directional control is required, often in tight spots, where the propeller could be rotated around a
360 degree horizontal axis.
This required some quite complex shafting and bearings with the
propulsion shaft having to be aligned from a horizontal axis, to a vertical
axis (around which the unit rotates) to the horizontal axis of the propeller
itself. The principle of what might be called “EURoedynamic?EUR” positioning,
with total control of a vessel?EUR(TM)s movements, independent of external
assistance from tugs is very attractive to cruise ship operators, and thus has emerged
the development of the “EURoepodded?EUR” propulsion unit, which are very large
azimuthing propulsion systems in which the whole propulsive power of big ships
can be fully directional.
Cruise ships often have to get into confined ports where tug
assistance is not necessary, or even lay off a port where the water is too deep
to anchor. The total manoeuvrability which is available from azimuthing “EURoepods”
is hugely appreciated. Moreover, the giant rudders and separate steering gears
which would normally be fitted to such ships are no longer necessary, and it
may be possible to dispense with some of the lateral thrusters which would be
required for a conventionally propelled cruise ship.
There are two major variants, based on the location of the
motor:
1. Mechanical transmission:
where the motor is inside the ship
and power gets transmitted to the propeller via bevel gears. The motor may be
either a directly mechanically connected diesel engine, or an electrical motor
getting its power from generators run by an electricity producing engines
(usually diesel engines) elsewhere in the ship.
2. Electrical transmission:
where the electrical motor is in the
pod itself, directly connected to the propeller without gearboxes. The energy
used to drive the motor in the pod is produced by machinery inside the vessel,
usually by diesel engines or gas turbines which drive electric generators, in a
system comparable to that used by diesel-electric locomotives.
ABB Azipod was the first
product using this technology. The Azipod propulsion system improves the
steering behaviour. It can be built for pushing or pulling operation, and low
or high speeds. When Azipod units are installed in the stern and bow, the ship
can do sideways manoeuvres (or azimuthing) the ship can go astern by changing
the direction of rotation of the propeller or by rotating the azimuth angle 360
degrees. Additional manoeuvrability may be attained by changing the azimuth
elevation. Using azimuth thrusters, the crash stop distance can be halved
compared to conventional propeller systems.
WHAT IS AZIMUTH THRUSTER
Reviewed by HODO
on
February 27, 2018
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