Feature 4 | CRanes & CaRgo handlIng
areas. For one-side operation, a reduced
travel speed is used – lower than normal
high speed, but higher than low speed.
The operator can also use low speed in a
high speed area, but never high speed in
low speed area. Motor rpm, and therefore
panel speed, is controlled by VFD. In
heeled conditions the VFD brake resistor
keeps the speed at the correct level.
Because of the VFD, the initial slow
speed gives a much higher driving force
(i.e. torque) compared with the normal
speed mode needed during one-side
a schematic of speed and torque (opening)
operation (in heeled condition).
Panel position monitoring improves
hatch opening/closing operations: the Position control is based on absolute condition analysis with planned
operator does not need to see the actual encoders. Whenever there is a problem maintenance based upon equipment
position of a panel when positioning is in position control, the system goes into maintenance protocols, Cargotec can now
required (e.g. for one-side operation) and ‘safety mode’. This operating mode allows offer seamless service solutions.
different automatic stop features are used. panel to be driven, but only at low speed.
In two-panel arrangements both panels If electrical power cannot be used, panels Conclusions
have their own actuator. Both actuators are can be operated with the same emergency It is clear that the future will bring stricter
controlled by separate VFDs. This enables equipment usually used in all MacGregor measures to protect the environment,
separate speed control for each panel. It hatch cover systems. which the shipping and shipbuilding
is possible to operate just one side. This industries will have to comply with. But,
separate speed control feature is also used Remote diagnostics ‘green’ solutions are not just ways of
for one side operation. Remote diagnostics technology has conforming with legislation or improving
advanced to a stage where it is now practical a company’s image – they make economic
Improved feedback to relay parameters of equipment operation sense.
to operator to a central point for analysis, monitoring The shipbuilding process also needs to
A four-digit display and four indicating equipment condition wherever the ship be made more effective, and one way of
LEDs are included in the Portable happens to be. Electric drives are ideal for achieving this is to move work from the
Operating Unit (POU) for operator this. By using all-electric components it is building dock to a workshop – such as a
feedback. LEDs indicate with two colours possible to provide continual diagnostic supplier’s own factory – where there is a
(red and green) and different blinking data for analysis round the clock. better environment and a concentration
of VFD and encoder status to operator. Using the latest diagnostics tools it is of skills.
This also improves diagnostics for now possible to offer real-time equipment Finally, shipowners today need to
maintenance. The four-digit display shows condition analysis and reporting via be more effective than ever. Remote
simple text messages about operations to telephone or satellite communication diagnostics technology makes this
the operator. Confirmations of certain media. In combining the equipment possible. NA
operation sequences are also required,
and are shown on the POU display. These
a schematic
confirmation texts are used to improve
of number of
equipment safety, especially in one side
revolutions (i.e.
operation.
positions) and
In the main control cabinet traditional
travel speed
lamps are used for feedback and system
areas.
status.
Redundancy features
Some redundancy has been enabled in the
control system design. For instance if one
of the deck PLCs is broken, the panel can
be driven directly from VFD operating
panel. It is also possible to manually
cross-connect motors between VFDs.
68 The Naval Architect February 2010
NA Feb10 - p65+p66+
p68.indd 68 02/02/2010 15:38:29
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