US research vessel Roger Revelle is undergoing a refit at Portland, Oregon, where the pumpjet has been replaced with a retractable thruster
Research vessel Roger Revelle, named after a US scientist and researcher who was among the pioneers of global warming research, is undergoing a major midlife extension at the Vigor shipyard in Portland, Oregon.
The one-year refit involves replacement of all gensets, switchgear, drives and propulsion motors. In addition, Roger Revelle is receiving a new retractable bow thruster and transducer gondola. The original pumpjet thruster is being replaced by a ZF retractable azimuth thruster. The enhancements will enable the ship to map the ocean floor in sharper detail.
The ballast, firemain, potable water, A/C chiller, sewage and refrigeration systems are being replaced. Cranes, overhead lighting and various maintenance upgrades will also be made. The refit will extend the life of the vessel another 25 years, according to the shipyard.
The 273 ft-long research ship usually spends more than 250 days at sea a year. The refit is intended to bolster US Navy and national oceanographic research.
Roger Revelle (AGOR 24) is a general-purpose oceanographic research vessel constructed by Halter Marine Inc. and was delivered to the Office of Naval Research (ONR) for operation by the Scripps Institution of Oceanography in 1996. The ship hosts scientists supported by US federal, state, and other agencies. Vigor Shipyard is performing the US$52M refit, which is sponsored by ONR, Scripps and the National Science Foundation.
R/V Roger Revelle is one of six major oceanographic research vessels owned by the US Navy and operated within the University-National Oceanographic Laboratory System shared-use facility. The National Science Foundation is the primary US federal agency supporting research across all fields of science and engineering.
Among the key scientific equipment onboard is a Hydrographic Doppler Sonar System (HDSS), a hull-mounted long-range dual-frequency (50-140 kHz) Doppler sonar that measures current shear at high resolutions. A Kongsberg Dynamic Positioning system DP-0S1 provides station-keeping capabilities.
Other notable features of Roger Revelle include an EM122 deep-water multibeam mapping system featuring redundant motion sensors for failover protection, an X-band radar that measures surface wave properties, and an advanced computer network with wired and wireless access for all scientists.
Three ship-service diesel generators 600VAC @ 1,500 kW are dedicated for propulsion, while three others at 700 kW are for propulsion or ship-service power. With a length of 273 ft and a beam 52 ft, the 20-year-old vessel’s features included dual LIPS z-drive thrusters and a 1,180 hp azimuth waterjet.
Changing out the pumpjet with a ZF retractable azimuth thruster has been completed. The extendable/retractable azimuth thruster technology improves station-keeping performance and low-speed maneuverability, according to ZF representatives.
The vessel is receiving a 1,100 hp ZF Marine ZF AT 5011 RT TT-FP L-Drive Retractable Thruster. The telescopic design allows the device to extend downward from the hull, where it can operate as an azimuth thruster, rotating 360 degrees. When retracted, it operates as a standard tunnel thruster. In the upper retracted position, the thruster is completely stowed away inside the hull.
The result is a multi-functional solution that provides traditional bow maneuvering in port or in shallow waters while increasing station-keeping performance of the vessel at sea. Operational control of the unit is provided by ZF ThrusterCommand electronic controls. ZF Marine will be supplying the same system for Roger Revelle’s sister-ship, R/V Atlantis, during that vessel’s mid-life refit scheduled to start in 2020.
The retractable azimuth thruster comes in two configurations: Z and L drive. In the Z drive the drive motor is horizontally mounted resulting in a Z-shaped shafting, whereas in L the motor is vertically mounted. In the Z drive, there is either a telescopic cardan shaft or a gear coupling that disengages from the thruster before it is retracted.
The ’combination mode’ allows the retractable thruster to be used as a transverse tunnel thruster in its upper retracted position. The outer well is equipped with a connection for tunnel.
Major engineering work went into the retrofit ahead of time, since the thruster project involved structural changes, say ZF representatives. All the preliminary engineering work and drawings were contracted to Glosten, a Seattle-based engineering firm. Once that was done, the shipyard took charge of planning the project and the production drawings.
The removal of the pumpjet and replacement with the retractable azimuth thruster took nearly two months. The thruster room structure had to be reconfigured. “Some bulkheads and girders were redone and the sideshell was cut open. New structural members were installed so the entire assembly, as well as the associated equipment such as the control panel and hydraulics, were able to be installed,” says Gaston Doucet, ZF Marine’s business development and sales manager - commercial thruster products.
The mechanical systems of the thruster have been tested. The hydraulic system for deploying the thruster has also been tested. Further testing will happen during sea trials.
The azimuth thruster can be controlled at four locations: locally at the thruster room, at the bridge, as well as at the two bridge wings. “Testing the control unit involves ensuring that all the control units are communicating with each other. Each of the control stations can throttle the rpm as well as direct the thruster to any desired direction in its extended mode,” says Mr Doucet. "The DP system can also take control for station-keeping and low speed maneuverability during scientific mission operations."
5.5 MW thrusters power largest crane vessel
In what could be a world first, four 5,500 kW thrusters have been specified for the world’s largest crane vessel.
Sleipnir is a semi-submersible crane vessel fitted with two cranes, each with a lifting capacity of 10,000 metric tonnes. Wärtsilä WST-65U thrusters have been installed on the aft, forming the main propulsion unit. The unit can generate ship speeds of 12.2 knots, which makes the heavy-duty ship capable of long voyages.
Wärtsilä has supplied the entire thruster system for the vessel: four forward and four aft. The aft and forward thrusters are interchangeable. The Wärtsilä WST-65U are underwater mountable too. This means they can be changed out at sea if drydocking of the vessel is not necessary. “There are not too many drydocks in the world that can handle this type of vessel,” says Wärtsilä marine director, thrusters and propulsion control systems, Lauri Tiainen. “The thrusters can be demounted and mounted back if maintenance is required. This feature ensures there is continuity of operations of the vessel."
The forward-aft interchangeability feature helps in spare parts inventory management, adds Mr Tiainen. The eight-degrees tilted propeller shaft solution also reduces the interaction between the thrusters and the hull, and boosts efficiency.
The forward thrusters are retractable, allowing the ship to navigate shallower waters.
The thrusters are equipped with Wärtsilä anti-pollution face-type shaft seals. Wärtsilä also supplied auxiliaries for steering and lubrication, the control units, and its Propulsion Condition Monitoring Service (PCMS). “Predictive maintenance can help to optimise uptime and maintenance regimes. With this system, it is not only possible to predict failures but any kind of wearing down, too, so maintenance can be planned,” says Mr Tiainen.