Wärtsilä Underwater Mountable Thrusters

• 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

Drillship
·         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

• 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.

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.

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.