Retractable Azimuth Thruster

Brunvoll's Retractable Azimuth Thrusters provide manoeuvring capabilities that extend the operational weather window of the vessel, increasing capacity, flexibility, productivity and safety. Options for afloat service possibilities.

Direct power transmission using a vertical top-mounted electric motor eliminates the need for special shaft and quick-release coupling arrangements when the thruster is lowered into and retracted from the working position. This solution also eliminates the need for gearboxes to connect the prime mover to the thruster – resulting in better total efficiency.

Design principle with valuable customer features

  • Shaped like a long column, installed vertically in the thruster compartment
  • Lowered into operating position and retracted into the hull by means of hydraulically operated lifting equipment
  • When Thruster is retracted, it is mechanically locked by means of spring loaded locking devices and the hull opening will be closed by a flush-plate attached to the bottom of the propeller nozzle
  • Delivered with azimuth arrangement as well as retracting arrangement and guiding column in pre-assembled condition fitted on the tank top/sea chest integration plate
  • This arrangement will allow for easy installation/integration of the complete Thruster Unit
  • When in lowered operating position the thruster unit is "locked" and pre-loaded in this position by means of the hydraulic lifting/lowering actuators
  • When the thruster is in operating position but not turning, the azimuth movement is locked by mechanical brakes
  • The stem housing is moving through a combined sealing box and bearing housing which is mounted to the tank top/sea chest integration plate
Brunvoll’s Retractable Azimuth Thrusters are products of years of experience. They have proven their worth in a variety of demanding applications, from research vessels and coast guard vessels to offshore supply vessels and shuttle tankers operating in the harsh climate of the North Atlantic. They have even proved invaluable for auxiliary and emergency «take home» propulsion.

Subsea Unit designed for heavy duty operations and low life cycle cost

  • Robust design, generous dimensions, and attention to details make for trouble-free performance.
  • Brunvoll focuses on excellent technical solutions to ensure that our thruster units can handle all the challenges of the marine environment.
  • Replaceable propeller blade bearing liners
  • Propeller blades are replaceable inside the nozzle
  • Various propeller blade materials and designs available
  • Controllable pitch propeller and fixed pitch propeller versions available

Advanced multiple sealing system

  • An advanced multiple sealing system is used for the propeller shaft to provide an ideal environment for the working parts
  • Non-polluting sealing solutions available for use of Environmentally Acceptable Lubricants (EAL). Limited amounts of EAL required
  • The design complies with US EPA Vessel General Permit (VGP)

Starter characteristics

Direct On-Line starter

Starting current:

5-10x Nominal motor current (IN)

Pros:

Low price and high starting torque

Cons:

High in-rush current

Description:

The Direct On-Line (DOL) starter consists of a contactor and a protection device such as a circuit breaker. The contactor is energized when the start button is pressed, and the full line voltage is connected to the motor. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Star-Delta starter

Starting current:

2-3x Nominal motor current (IN)

Pros:

In-rush current reduced with approx. 60% compared with DOL

Cons:

Reduced starting torque

Description:

The star-delta starter method applies reduced voltage to the motor, thus reducing current, during startup. This method requires that both ends of motor winding terminals are available. When connected in star each winding has less voltage (1 / √3 ~ 60%), and thus will have reduced starting current and torque. When full speed is reached the motor is connected in delta, having full torque available. Propeller pitch can be increased, and load applied when motor is connected in delta. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Auto-Transformer

Starting current:

2-3x Nominal motor current (IN)

Pros:

In-rush current reduced with approx. 60% compared with DOL

Cons:

Reduced starting torque

Description:

Auto-Transformer also applies reduced voltage in steps to the motor during startup. The transformer voltage ratio can be designed to the application, typically having a 50-70% motor voltage during startup. The motor consumes less current at a lower starting voltage. For example, with a 50% tap on the Auto-Transformer, the motor draws half its rated current, or about 25% of what it would draw with a DOL starter. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Electronic soft starter

Starting current:

2-2,5x Nominal motor current (IN)

Pros:

In-rush current reduced 

Cons:

Reduced starting torque.
Based on electronics

Description:

An electronic soft starter is a starting device that controls the way electricity is provided to the motor by using active switching devices such as thyristors. The device works in both in-line and in-delta configuration modes in three-phase motors. 

This starting method is ramping up the motor voltage in the starting sequence resulting in a reduced start-up current, allowing for a smooth and surge-free increase in motor torque. The voltage dips, stress, and wear and tear on the mechanical parts are all reduced as a result. Due to the thyristors there will be harmonic distortion of the current, and the influence on system voltage will depend on starting current and system impedance. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Frequency converter starter

Starting current:

0,5x Nominal motor current (IN)

Pros:

In-rush current reduced.
Full speed and torque control

Cons:

THD generated, filters required.
Based on electronics

Description:

This is an electronic-controlled approach for starting asynchronous motors smoothly. It controls the frequency and current for the motor with electronics inverter circuits, avoiding large startup current. The thruster system's mechanical parts will be protected from high load because of the smooth start-up, and the this will also reduce the load on generators during startup compared to line-starter options. Depending on required performance torque and current may be below nominal values during startup. This is the high-end solution for the starting the thrusters, giving benefits such as smooth start, better energy economy, reduced wear and tear and process optimization.  Other benefits include motor speed stability during load changes and a longer motor life overall. Motor is started with propeller in zero pitch position (IZP).

Frequency converter starters may have different interface towards the main switchboard where 6-pulse rectifier is the most common, but both 12/24 pulse and Active Frontend (AFE) are used.6-pulse starters are the most common type, widely used due to the compact design and availability.The disadvantage with the 6-pulse starter is the increased THD during startup, particularly in smaller power system with large thrusters this might be an issue. 

To mitigate the THD a 12 or 24 pulse transformer and rectifier may be chosen, typically used for larger thrusters in larger ships. 
Frequency converter starters with active front end guarantees sinusoidal current and does not require a transformer. The AFE rectifier and LCL filter is more spacious than the 6-pulse rectifier and is suitable for high end solutions and ships with relatively small power system compared to thruster power.

Click the images to enlarge

Complete system deliveries

One source - one responsibility

For optimal performance Brunvoll takes responsibility for delivering complete systems and for providing support throughout the lifetime; from design, production, installation and commissioning, through daily operation.

Ask us for a complete thruster system including:

  • Electric drive motor, asynchronous or Permanent Magnet type
  • Starter or VFD for the motor
  • BruCon Control, Alarm and Monitoring system
  • BruCon Joystick and DP

Compile your vessel from Brunvoll's  product range

The wide product range of Brunvoll gives a unique configuration flexibility of integrated propulsion, manoeuvring and automation systems, see Propulsion Systems.

RETRACTABLE AZIMUTH THRUSTERS

MODEL PROPELLER DIAMETER MM POWER RANGE KW
AR 63 1 650 500 - 800
AR 80 2 100 1 000 - 1500
AR 100 2 600 1 800 - 2 500
AR 115 2 900 2 500 - 3 500
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Technical Information

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Contact

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Joar Heggset

Joar Heggset

Sales Manager, Brunvoll AS

+47 916 30 640
joar.heggset@brunvoll.no
Montserrat Lugrís López

Montserrat Lugrís López

Sales Manager, Brunvoll AS

+47 906 28 360
montse.lugris@brunvoll.no

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