W?rtsil? Underwater Mountable Thrusters

The Wärtsilä underwater mountable thrusters with designation WST-U are part of a series that comes with several added features, such as an increased power range, an 8° tilted propeller gearbox, and the Wärtsilä Thruster Nozzle providing a superior and reliable DP performance. The underwater mountable thrusters from the LMT series are available for the lower part of the power range.

    • The Wärtsilä Underwater Mountable Thruster series is designed for use with semi-submersible drilling rigs, drillships and other vessels, such as semi-submersible accommodation rigs, crane vessels and pipe layers, requiring thrusters that can be mounted while the vessel is afloat.
    • The underwater mountable series has a high maximum power output of up to 6500 kW, which makes it favourable for use also on large offshore construction vessels (OCVs). The large propellers provide high thrust values to ensure high dynamic positioning (DP) capability. The series consists of six types, ranging from around 2000 kW to a maximum 6500 kW. With a choice in propeller diameters and different power levels, the Wärtsilä Underwater Mountable Thruster series can offer a tailor-made solution to meet customer requirements regarding, for example, bollard pull or vessel propeller size limitations. Each thruster type has several options to accommodate project specific requirements. 
    Example configurations



    ·         6 x WST-55U at 5500 kW

    ·         3900 mm FP propeller in nozzle

    ·         8° tilted propeller shaft

    ·         Diesel-electric

    ·         L-drive


    Semi-submersible drilling rig


    ·         8 x WST-55U at 4500 kW

    ·         3900 mm FP propeller in nozzle

    ·         8° tilted propeller shaft

    ·         Diesel-electric

    ·         L-drive

    Semi-submersible drilling rig 

    Key benefits
    • Exchangeable underwater for vessels that do not have access to dry docking facilities
    • High bollard thrust and propulsion efficiency
    • Effective DP operations thanks to the 8° tilted propeller shaft or 3° tilted nozzle
    • Electric L-drive up to 6500 kW
    • High reliability
    • Wide power range
    • Compact and light design
    • Easy installation

    Effective DP operations
    The three largest thrusters within the Wärtsilä Underwater Mountable Thruster series feature an 8 degree tilted propeller shaft and nozzle, which direct the propeller jet away from the hull and other thrusters. In addition to reducing hull interaction losses, this also greatly reduces interaction between the thrusters, thus making the so-called ‘forbidden zones’ considerably smaller. The overall gain in effective bollard pull thrust for dynamic positioning operations is about 15% when compared to conventional units.

    Effective DP operations
    Effective DP operations 2
    Effective DP operations 4
    Effective DP operations 3

    High efficiency

    The Wärtsilä Underwater Mountable Thruster series features the Wärtsilä thruster nozzle to provide excellent bollard pull performance.

    First class reliability

    Each component and aspect of the underwater mountable thruster series has been selected to achieve a high level of reliability. With the Wärtsilä PCMS (Propulsion Condition Monitoring Service), the reliability and availability of the thruster can be improved even further. As this service is recognized by the main marine class societies, the thruster overhaul intervals can be extended according to the condition of the equipment.

    Compact and with less weight

    Detailed FEM analyses have been made to optimize the strength of the components so as to keep the overall weight as low as possible. Compact dimensions result in less space requirements in the thruster room and more payload capacity for the vessel.

    Technical Info
    Main technical data
    Weights and Dimensions
    Weight and dimensions
    Power ranges
    Wärtsilä Underater mountable thrusters
    Weight and dimensions 2
    The Wärtsilä Retractable Underwater Mountable Thruster (WST-65RU) has been designed to meet the needs of large offshore vessels (OCVs) as well as semi-submersible rigs and drill ships. 

    With the power output of 5500kW it is typically designed for vessels that require thrusters that can be retracted during transit or while entering shallow waters. The thrusters can be mounted or de-mounted while the vessel is afloat. Additionally, the ability to retract and deploy the thruster enables an increased level of operational flexibility. 

    The thrusters feature a unique combination of retractable and underwater mountable functionality. 

    The WST-65RU is based on the WST-65U underwater mountable thruster which has been designed with performance and reliability as key requirements. The eight degree tilted propeller shaft solution is a feature of the Wärtsilä Underwater Mountable Thruster that reduces the interaction between the thrusters and hull significantly, thereby enhancing the dynamic positioning performance of the vessel. The thrusters are equipped with Wärtsilä Oceanguard anti-pollution face type seals, which have been selected primarily because of the challenging environments in which these thrusters will operate. 

    In combination with Wärtsilä PCMS (Propulsion Condition Monitoring Service) downtime and maintenance costs can be minimized.

    Key benefits:

    • Optimised thrust enabling effective DP operations
    • Retractable
    • Thruster outboard part can be exchanged without dry docking the vessel
    • A telescopic shaft allows a static mounting of the E-motor and ease
    • Integrated solution provides smallest possible area footprint and overall lighter construction
    • Based on proved recognizable technology and in-house propeller design know-how
    WST-65 RU_1
    WST-65 RU_2

    Press releases

    Product hologram


    W?rtsil?’s next generation underwater mountable thrusters: efficient and easy to install

    W?rtsil?’s next generation underwater mountable thrusters, with their 8° tilted propeller shaft, set a new standard in thruster propulsion performance and reliability.
    16 April 2014
    • In Detail article

    New W?rtsil? thrusters – Keeping drilling...

    The new W?rtsil? LMT-3510 thruster...
    17 May 2013
    • In Detail article

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