DECK EQUIPMENT
MacGregor cranes reduce environmental impact
M
acGregor’s new GLE electric cranes are based on proven designs but combine
improved operability with less environmental impact. They inherit the characteristics of the established GL series, except that all movements – luffing, slewing and hoisting – are electrically driven. By avoiding the energy transfer between electric
drives and hydraulics the new all-electric system offers lower power consumption. In turn this means lower running costs, less vibration and much lower noise levels. For the operator the new all-electric crane
offers significant benefits in terms of improved operational efficiency. Operations are more precise, with smoother acceleration and decelerations. Under part loads, line speeds are notably faster and it is easier to achieve faster cycle times. Improved load cycle performance can be summarised as:
• • •
The ramp-time for each motion will be based on the load, optimising crane response time
Crane operation will be step-less with maximum speed based on the load and outreach only The electric crane can keep the load in an exact
position even with the brake open which makes it easy to handle the load.
• In extreme high temperatures the crane system will automatically de-rate the performance to avoid downtime due to overheating
• Optimum power control and lower power consumption.
Other improvements include the fact that no
starting current peak will occur – this results in lower generator requirements; overload protection is more accurate, based on load cell and measurement of the torque of the electric motor; and it is possible to measure the load constantly even if the hoisting brake is closed. By using a frequency controlled drive solution
on all motions it is possible to monitor data that is helpful for predicting the ‘health’ of the crane system. With this information it will be possible in the future to predict the ‘health’ of the crane at any time. ‘The benefits of improved operational efficiency
will result in an overall through-life economic benefit,’ said Hans Sahlin, cranes sales manager.
Scan Brasil – an ice-classed multipurpose ro-ro/lo-lo carrier has two 240tonne Liebherr cranes that can combine to handle loads of up to 480tonnes. The models in question are a pair of CBB 240(75)/11(33) cranes with Liebherr’s Litronic control system.
• An unobstructed view of the working area thanks to the improved position of the first jib bracket.
• These cranes also have Litronic, Liebherr’s proprietary crane control and management system, which controls crane motion to ensure the best possible performance and protection for the crane.
The Litronic control system also records data
about all of the individual components in loads handled by the crane, along with alarm signals and failures as well as peak values, and the lifetime of components can thus be analysed, preventative maintenance undertaken, and spare parts supply can be established. The Litronic control system also has a number
of optional features, including an anti-collision mode, automatic tandem operation, and remote control of crane operation for improved operational safety. As Liebherr also noted, the operation of
anti-heeling systems onboard a vessel can be supported through the control system whereby the total moment of all cranes can be calculated in relation to the vessel’s longitudinal axis, depending on the load and working radius of each crane. This information is displayed on the vessel’s bridge.
Huge mast crane for DP Perhaps the most notable recent delivery made by well-known heavylift crane maker Huisman- Itrec, of the Netherlands, was a 3000 short ton heavy lift mast crane for Sapura 3000, a DP pipelay and heavy lift vessel that is being built for Malaysian company Sapura Crest Petroleum in Singapore.
In August 2005 offshore contractor Acergy
and SapuraCrest Petroleum entered into an agreement to form a 50:50 joint venture to own and operate the Sapura 3000 jointly. The vessel is designed to be the most advanced deepwater construction ship in the fast-growing Asia Pacific offshore market. The vessel was built in China and following
outfitting in Singapore is scheduled to be in service mid-2007. With a length overall of 151m, a mast crane with a 3000 short ton lift capacity and a large clear work deck area, this dynamically positioned vessel is ideally suited to conventional shallow water pipelay, very deepwater construction projects and topside installations. Its capabilities will include conventional S-lay for shallow water and steep S-lay or J-lay for deepwater and steel catenary riser installation, into water depths beyond 2000m, depending on pipe specification. Huisman Itrec is supplying all of the lifting
and pipelay equipment for the vessel and is, in part, responsible for the design of the automation and drive system for the ship itself, onboard which almost all key items of equipment will be electrically driven. Traditionally, cranes and winches have been
driven by hydraulics or direct current, mainly in order to be to be able to generate high levels of torque, but due to advances in electro-technology a rapid change is taking place with more frequent use of frequency-controlled motors. Nowadays, almost every Huisman crane is
driven by asynchronous three-phase motors, controlled by a frequency converter. To distribute energy properly and to suppress the inevitable harmonic distortion a 12-pulse transformer is used with a rectifier of 3000kVA, which creates a direct current bus of 930Volts out of the ship's net, and virtually all drive systems are fed from this bus. One particularly special feature of this crane is
Huisman Itrec in The Netherlands is supplying a huge 3000ton crane for Sapura 3000.
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that the boom can rotate full circle, unlike other mast cranes built until now, all of which have a fixed winch frame. This being the case, a smart
THE NAVAL ARCHITECT FEBRUARY 2007
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