thrusters
››› Register of Shipping. Steeprop claims that they will be the most powerful mechanical azimuth propulsors in the world at their time of delivery. The first shipset was planned to be delivered to the shipyard in Vyborg as this issue went to press the following two shipsets three months and six months later.
Sensing problems saves cash Like all rotating or reciprocating machinery, thrusters are subject to wear and require regular maintenance. Being outside of the hull in most instances they are also exposed to other risks of damage, making them exactly the type of machinery that will benefit from continuous monitoring and this has been recognised by some makers and third party specialists.
Wärtsilä is an example of a manufacturer that has applied condition monitoring across the full range of its products from engines to propellers and has been providing a service for its thrusters for around five years now. The company’s Propulsion Condition Monitoring Service (PCMS) began as a retrofit option but is now standard on most of its thruster supply contracts. PCMS is not limited to thrusters alone and can also be used on podded systems – which some consider to be different from thrusters – and to conventional controllable pitch propellers. Within the system, accelerometers are used to monitor the condition of mechanical parts, such as gears and bearings and can also detect, for example, blade damage. A single PCMS system is devoted to each thruster or other propulsion component and can process up to 16 accelerometers simultaneously. Lubrication and hydraulic oils are monitored by measuring temperature, the oil-water saturation and any oil contamination.
On a ship with many thrusters and perhaps a conventional propeller/rudder also in operation, the system gathers and shows information from all the PCMS cabinets on the vessel. It can give real-time and trend values and advise the operator in case of irregularities. It has been developed to detect the operational states by real- time comparisons of parameters from multiple sources. For example, the vibration measurements are linked to the operational condition of the vessel. If an operational state causes severe vibration, the PCMS will advise how to rectify the situation. Each day a data package of the day’s monitoring is sent to Wärtsilä’s Condition Based Maintenance centre. There the data is automatically processed and, in the event of irregularities, the propulsion specialist will
70 I Marine Propulsion I April/May 2014
CMT’s thruster monitor checks a number of parameters to detect vibration and other faults (credit: CMT)
take action. Once a month, the customer receives a PCMS report describing the condition of his equipment. Most data analysis is automated.
Although the system can identify major problems and alert operators to take instant action to prevent damage, its main benefit is identifying problems that build gradually and allow appropriate action to be planned and implemented before a catastrophic failure takes place.
Having the system on a vessel can also allow for extended time between overhauls and in some instances allow five-yearly visual inspections required by class to be waived. A similar service is offered by the German third party specialist Condition Monitoring Technologies (CMT). Being independent, CMT’s service is not confined to one manufacturer’s products but can cover all brands and types of thruster providing a useful option for ships that have equipment from different makers installed on board. The CMT service operates in the same way as Wärtsilä’s PCMS, monitoring oil
ZF Marine Krimpen has been designated as the Global Competence Centre for commercial azimuth thruster technology within ZF’s Marine Business Unit. The Dutch company produces a wide range of steerable and transverse thrusters, covering a range between 100kW and 2,000kW, with electric, diesel or hydraulic drive systems. Among its latest deliveries is Anna-B, which it describes as a versatile multi- purpose workboat with dynamic positioning capabilities. It is powered by four ZF thrusters, with no conventional
temperature and condition and using sensors to detect vibration caused by wear or other system fault or damage. The fully automated system is said to be ideal for both newbuildings and retrofits as it can be easily combined with any existing thruster and ship management systems to create a single master system. CMT’s system is also approved by leading class societies as meeting their condition-based maintenance (CBM) requirements and can therefore contribute to operating costs by removing the need for scheduled overhauls. Services and systems providing condition monitoring of thrusters are not confined to the two companies mentioned, as most leading thruster makers offer some degree of condition monitoring. Major manufacturers, especially those that have products other than thrusters that also benefit from CBM regimes, will provide the type of shore-based expert analysis service described above. For smaller organisations, it may be left for ships crews and the manufacturer’s service engineers to interpret data retained on board.
ZF Marine lifts Krimpen’s profile
shaft installations or tunnel thrusters. At the bow are two shallow draught thrusters, type ZF SDT 4010 FP, each rated at 250kW, which are driven by electric motors and a drive system specially built by ZF Marine Krimpen. At the stern are two well-mounted azimuth thrusters, type ZF AT 6311 WM-FP, of 1,140kW each and driven by Caterpillar engines.
The vessel has dynamic positioning capabilities, which will be described in more detail in a dynamic positioning feature in the next issue of Marine Propulsion. MP
www.mpropulsion.com
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