propulsion
sub-assemblies can be used to create different types of the same size of thruster: modular thrusters for weld-in, bolt-in or can- mounted installations; retractable thrusters; containerised thrusters; and underwater (de) mountable thrusters.
All these types are available with power ratings
up to 7,000kW and supplied with either fixed pitch or controllable pitch propellers. Nozzles are commonly specified in DP applications to increase thrust but thrusters without nozzles can be supplied for specific duties. Wärtsilä’s propulsion condition monitoring service provides the operator with real-time advice and periodic operational feedback and reports on thruster condition. A reliability- centred maintenance strategy can be applied to give prognoses of current and future reliability, maximise the installation’s availability and reduce total life-cycle costs.
An integrated and flexible condition-based maintenance (CBM) system for propulsion and positioning thrusters was recently introduced by Gothenburg-based SKF. SKF Monitoring addresses a trend to integrate existing separate systems and combines all required information in one installation for integration with both thruster and ship management systems. The solutions are fully scalable and further key machinery can be conveniently added to the same monitoring platform and system. SKF Monitoring is applicable by vessel operators as well as thruster manufacturers to newbuilding and retrofit installations, and is reportedly suitable for all makes and types of thruster. The system can support operators in meeting classification society CBM requirements and provides the basis for proactive maintenance and operational decisions based on actual thruster condition. The benefits include extended class survey intervals, reduced need for drydocking, lower risk of failures and enhanced vessel reliability.
SKF’s proven range of condition monitoring
products and services are exploited in the system, including online technology for vibration, lubricant and data monitoring. The company offers
turnkey installation, commissioning,
remote data analysis and reporting services, along with suggested reliability improvements based on the monitored results. Kittiwake’s ThrusterSCAN online condition monitoring system for azimuthing thrusters has been refined with input and support from Transocean, whose eight-thruster Development Driller III rig will benefit from an installation. Continuous monitoring of wear debris, water ingress and lube oil quality will provide early warning of thruster component damage, lubricant degradation and seal leaks or failures. Information is also derived to help optimise
thruster operating parameters and effectively manage overhaul schedules. Real-time feedback
66 I Offshore Support Journal I June 2012
Voith’s Linear Jet will debut on a wind turbine support vessel
ensures that any changes are highlighted as they start to occur, rather than at scheduled inspections when it may be too late to heed the warning and initiate remedial measures. A wide range of azimuth propulsors from Finnish specialist Steerprop includes a core programme of models with ratings from 800kW to 7,000kW in open or ducted propeller configurations. Each design is based on a common template but customised and optimised to the individual application. Ducted models can be fitted with a 19A-type Kort nozzle or with Steerprop’s high efficiency HJ3-type nozzle. Azimuthing can be affected by electrical or hydraulic systems. References
for this product line include
Bourbon’s GPA254L anchor-handling tug/supply vessels, each equipped with three 1,685kW Steerprop SP 20 D propulsors, and the group’s GPA654M platform supply vessels (PSVs) built by Sinopacific Shipbuilding in China with outfits of three 843kW SP 10 L propulsors. Where fuel efficiency at high speeds is critical or where propeller diameter is limited by external factors and exceptional manoeuvrability is required, Steerprop offers its contra- rotating propeller (CRP) designs. These Dual- End propulsors with ice- or debris-reinforced propellers are recommended for vessels deployed in icy or shallow waters, the Steerprop CRP range covering input ratings from 800kW to 20MW. Among the references, the ROV survey vessel
Edda Fonn operates in the Norwegian Sea with twin 2,200kW SP 35 CRP propulsors. High efficiency, low noise levels and virtually non- existent vibration and cavitation are claimed for Dual-End CRP solutions. Addressing applications dictating high power and extreme reliability, such as icebreaking, Steerprop’s ARC series is offered with ratings from 800kW to 16MW in any ice-class. Further evolution has resulted in the ECO CRP unit, available with ratings from 5,000kW to 20MW,
which combines the hydrodynamic qualities, redundancy and reliability of Steerprop’s Dual- End CRP and ARC designs.
Norwegian specialist Brunvoll will gain valuable experience for offshore projects from a rim-drive thruster (RDT) installation on the road ferry Eiksund, which was retrofitted with twin RDTs, one at each end of the double-ended vessel. The units in this system benefit from an innovative electric drive solution from Inpower AS, with thruster speed controlled directly by the speed of the diesel generators. RDTs can be applied in
diverse thruster
applications based on a variable speed electric drive, such as azimuthing main or auxiliary propulsion thrusters, retractable azimuth thrusters, tunnel thrusters and combined tunnel and azimuth thrusters.
Schottel’s thruster and propulsor programme continues to attract offshore industry business. A pair of SRP 2020 FP Rudderpropellers drive US-based Aries Marine’s diesel-electric PSV Betty Pfankuch, a sister to Dwight S Ramsay and one of a growing number of STX-designed Tiger-shark class vessels. The thrusters incorporate fixed pitch propellers turning in 19A Kort nozzles to deliver a maximum speed of 14 knots and a cruising speed of 10 knots with only two of the four Cummins QSK60-driven main diesel gensets running. Since the ZF group acquired the Dutch thruster specialist HRP at the end of 2009, ZF Services Espana – working in conjunction with specialists from HRP (now known as ZF Marine Krimpen) – has vigorously promoted the HRP programme in Spain and Portugal.
A number of orders secured include retractable thrusters for a quartet of 50m-long offshore standby vessels booked at the Astilleros Balenciaga yard in north east Spain by the Aberdeen-based Craig group. The thrusters, with 19A nozzles, are driven by 380kW motors running at 1,200 rpm via 12-pulse frequency converters. OSJ
www.osjonline.com
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