The shipping industry is increasingly aware of the benefits of system integration. As a result, more suppliers are offering complete power and propulsion packages to the marine market in order to provide optimised solutions that improve efficiency and minimise operating costs and the environmental impact of exhaust emissions. Caterpillar Marine Power Systems has been proactive in this approach and has experience in the provision of integrated propulsion systems, using its own equipment and specialist equipment supply partners, with which it maintains close links.
Caterpillar says it can provide propulsion systems to meet specific customer requirements with scope including engines, gearboxes, couplings, propellers and controls. Because design responsibility is from a single source, equipment can be accurately matched to provide optimum efficiency, and supply of the equipment can be co-ordinated to ensure efficiency of installation.
The company points out that the traditional approach to equipment selection is based on meeting key requirements of a vessel’s specification, such as bollard pull and sea speed capabilities. In looking at overall needs, however, it becomes obvious that only a small proportion of the vessel’s operating time may be spent working at specified design conditions.
By looking at the operating profile of each vessel, propulsion systems can be specified that are better optimised for the full range of ship conditions. New technology is also now available to assist with the design and optimising process, and advances in hybrid propulsion equipment offer system designers far more flexibility to achieve key specification requirements. Where at one time main propulsion engines needed to be capable of meeting the maximum propeller power requirements on their own, auxiliary motors can now be added to the shaft line to augment power by using the ship’s electrical generators, feeding the motors through power electronics equipment.
For many vessels, the move from traditional mechanical propulsion drives to diesel-electric systems has proved a major benefit and Caterpillar Marine has recently announced an order for its first comprehensive diesel-electric propulsion system for two newbuild Chinese liftboats. The company will supply complete propulsion packages to Jiangsu Dajing Heavy Industry Co, where the vessels are under construction. Each vessel will be equipped with diesel-electric systems using four electric drive Cat Propulsion MTA-523 1500kW azimuth thrusters driven with power supplied from eight Cat C32 generator sets.
“As a comprehensive power and propulsion solutions provider for the marine industry, we are pleased to continue to integrate our full portfolio of offerings in our customers’ operations,” said Wang Xiaohua, Caterpillar Propulsion sales manager. “China remains an area of strategic importance for us and this particular order is significant because it is the first time in China that we have supplied a full diesel-electric propulsion solution, including engines, propulsion systems and main switchboards.”
The vessels, which have planned deliveries during the summer of 2016, have been designed by Shanghai Bestway Marine Technology Development Co and are being built for Mekers Offshore Co. In addition to engines and thrusters, the Caterpillar scope of supply will cover major electrical items for the propulsion package including main switchboards, power management systems, transformers and variable frequency drives. Monitoring and alarm systems will also be provided, as will uninterruptible power supply equipment.
The C32 marine generator sets for the application are powered by V12, four-stroke diesels of 32l displacement which run at 1,800 rpm. Emissions comply with IMO Tier II limits and the units, which are available at 830kW and 940kW electrical output, can accept 100 per cent load application in a single step. Features include water-cooled turbochargers and exhaust manifold and a separate circuit aftercooler system. The engines are electronically controlled and provide facilities for remote monitoring.
Cat Propulsion MTA azimuth thrusters can be specified with either fixed or controllable pitch propellers and in Z or L drive configuration. Blades and hub can be provided in stainless steel or bronze material and either electric or hydraulic power options are available for turning systems. Dual full-capacity lubricating oil pumps are fitted to give redundancy in operation and oil is fed to the hubs of controllable pitch propellers from the hydraulic system, which also features two full capacity pumps. Oil condition monitoring is included, with information fed to the bridge control panel for continuous display.
In order to maximise thruster efficiency, the thruster design also includes a mechanism to enable the movement of the centre of the nozzle to coincide with the centre line of the propeller. The result is a regular and even clearance between propeller and nozzle, which also reduces operational wear. The nozzle itself is designed for ease of fitting and removal, which saves time during both initial installation and service work.
Cat Propulsion continues to see strong demand for its propulsion products and announced in December 2015 that it had secured a further contract with Seattle, USA-based Harley Marine Services for tug propulsion. The scope of supply includes four Cat 3516 marine propulsion engines and four Cat Propulsion Marine MTA-T azimuth thrusters, designed and rated for tug operation. These systems will power two newbuild harbour tugs under construction at Diversified Marine in Portland, with engines and thrusters planned for delivery in mid 2016 to support vessel deliveries in early 2017.
Each tug will have two Cat 3516 engines installed, each delivering 1,920kW of power which will be fed to the two MTA thrusters, fitted with 2.4m diameter propellers. The MTA 524-T units for this application represent a new version of existing MTA designs, optimised for tug applications. They include features to maximise bollard pull capabilities and increase manoeuvrability and will be fitted with custom-made fixed pitch propellers and a steering and lubrication system driven from a power take-off.
“Much of Harley Marine’s fleet is powered by Cat engines and, with the construction of these two new vessels, they are adding our tug-specific propulsion solution as well,” said Emil Cerdier, sales manager for Cat Propulsion. “Getting a complete package from one supplier simplifies the design, installation, and service support, allowing Harley Marine to rely on the Cat dealer network as a single point of contact for the entire powertrain system.”