A basic guide to the structure and function of a bow thruster (1)

Installation of the bow thruster

In general, the side thruster is a lateral thruster placed in the bow and tail pipes. The thrusters installed at the front end are called the bow thrusters, and the thrusters set at the rear end are called the stern thrusters.
The requirements for the number of thrusters installed depend on the length of the vessel and the cargo capacity.

For the installation of side thrusters, the following are essential:

• The thruster compartment, also known as the bow thruster room, should be easily accessible to the crew from the open deck

• The thrusters of most seagoing vessels use electric motors, which are heat-generating machinery, so they must be placed in a dry and well-ventilated area.

• The bow thruster room should be equipped with a high bilge water alarm device, and there should be an indication in the engine control room and the wheelhouse.

• The thruster chamber should be well-lit

• There should be at least one emergency light source in the thruster room.

• If more than one control panel is installed, ensure that the thruster is operated from only one control panel at a time.

• The thruster room should not store flammable materials in the motor area.

• Tunnels or conduits containing propellers must be installed perpendicular to the ship's axle in all directions.

• The propeller should not extend the catheter

• The grille rods can be installed at both ends of the tunnel, or not (considering how much debris the bottom of the ship will encounter during navigation). The number of rods should be kept to a minimum, as they tend to reduce thrust and the overall performance of the bow thruster (or stern thruster).

• Sharp edges on the grid bar should be avoided. For grids mounted perpendicular to the direction of the bow wave, the trapezoidal shape without sharpness is a good design choice

• The design and location of the thruster channels should not interfere with the flow of water under the hull or should not increase hull resistance

• Ensure that the materials used in the installed thrusters do not contaminate the existing equipment inside the ship, such as the steering linkage.

Construction and work of the bow thruster

The bow and tail thrusters are placed in tunnels on both sides of the ship. There are two such tunnels in the bow and stern.

The thrusters absorb the suction from one side and spray it to the other side of the ship, causing the ship to move in the opposite direction. This can be operated in two directions, i.e. port to starboard and starboard to port.

The bow thruster is placed below the ship's waterline. For this purpose, the bow thrust chamber should be checked regularly for water accumulation.

The bow and stern thrusters can be electric, hydraulic, or diesel-driven. However, the most commonly used is electric thrusters, which, like hydraulically driven thrusters, have a lot of leakage problems. In addition, diesel-powered bow thrusters require more maintenance.
The thrusters used are usually of the CPP type, i.e. they can change the direction of thrust by moving the blades on the propeller hub.
Inside the blade-bearing boss is a movable shaft (operated by hydraulic oil), also known as a hydraulic pod motor to drive the thruster.
As soon as the signal is given to change the pitch, hydraulic oil is supplied to operate the inner shaft (located inside the boss) to change the angle of the blades of the thruster.

The motor shaft drives the thruster shaft by means of a pinion device. The gasket is set inside the motor housing to contain the water in the tunnel.

The thruster assembly consists of the following components:

• Electric motor with safety relay

• Elastic coupling between motor and thruster

• Mounting and housing of the electric motor

• Connect the flange to the shaft

• Motor housing sealed

• Tailpiece with shaft seal

• bearing

• transmission shaft

• Zinc anode

• There are fences at both ends of the tunnel

Operation of the bow thruster

The bow thruster consisted of an electric motor mounted directly above the thruster using a worm gear device. The motor runs at a constant speed and adjusts the controllable pitch blades whenever thrust or direction needs to be changed.

These blades move, and the pitch of the paddle is changed with the help of hydraulic oil, which moves the hub on which the blades are mounted. Since the thruster is a controllable pitch type, it can be operated continuously, and the pitch can be adjusted to zero when thrust is not required.

The bridge controls the thrusters and gives directions remotely. In the event of a remote failure, there is a manual station in the thruster room for changing the pitch and can be operated from there.

Typically, the hydraulic valve block that controls the pitch of the blades is operated in the BT chamber to change the blade angle in case of an emergency.

When the bow thrusters operate alone and give a signal on the port side to maneuver the pitch, the thrust will turn the ship from the front to starboard.

Similarly, when the bow thruster is operated separately and gives a starboard pitch signal, the thrust will cause the ship to turn from the front to the port side.

When the stern and bow thrusters are operated simultaneously on the same side, the ship will move laterally to the opposite side.

As shown in the image above, the bow and stern thrusters provide excellent maneuverability for the vessel.