Feature 4 | Cranes & Cargo handling
mechanical parts used in MacGregor mechanism. The mechanism converts the hatch covers are closed at sea, allowing
equipment. Therefore, any new mechanical rotation (torque) into a vertical movement. free relative movements between ship’s
parts will be proven designs with the same When closing, the mechanism lowers hull and hatch covers
reliability as existing components. the covers and pushes them together to
•
the modular configuration means that
In operating cylinders there is achieve the correct amount of rubber installation and repairs can be done
basically only one part – the actuator compression and tightness. independently and replacements are
part connected to the cargo equipment The MacRack, therefore, makes separate easy
structure or hull structure. If the cylinder hatch cover lifters obsolete. This reduces
•
automatic locking when closed, but with
is replaced by electric screwjacks, such a maintenance work for the shipowner, and a manual release
mechanical interface will be the same, so the shipyard’s installation work is also
•
for shipyards the standard interface’s big
parts reliability remains the same. simpler because fewer components need to benefit is speeding up the ship design
Electric design involved replacing be installed on the coaming. A significant process.
hydraulic valves with electrical contactors feature of this side-rolling system is that
and Variable Frequency Drives (VFD) the actuators are installed on the hatch The control system
for speed control. Each item has a local sides only. There the drive unit is well The electric control system enables
electrical contactor cabinet for the start and protected from cargo spills during loading automatic speed control; allows
control of the electric motors. This cabinet and discharging. Detailed technical checks independent panel control – meaning
replaces all operational valves found in the as well as prototype tests have been carried that panels can be driven separately;
hydraulic system. The contactors can be out, and a patent is pending. improves feedback to the operator; and
manually operated, offering the same first The panels are kept in the closed has automatic operation and safety
line of redundancy operation provided by position by an automatic lock (with a features. Redundancy is also to some
the hydraulic valves with manual opening/ manual release). For intermediate stops extent achieved with the control system
closing. the panels are held by the built-in brake design.
The electric motors are either controlled on the motors. With the opening/closing The control system uses bus
by inverters or by variable frequency movement, auto-cleats are activated in the communication (e.g. CANopen, Profibus,
converters, when speed adjustment is same way as for the Roll-up-Roll system. Profinet, DeviceNet) between system
needed. A further advantage of VFD is that This new system incorporates a components, thus reducing cabling
at a low speed the torque can be higher. number of mechanical as well as electrical work on board and as an option allows
Electronic control design addressed innovations: information to be shared with external
overload protection and other control
•
the drive and lifting systems are systems as well.
functions that are carried out by security combined
valves and control valves in the hydraulic
•
automatic cleating (as in Roll-up-Roll) automatic speed control
system, replacing them with similar is foreseen Panel position is monitored by continuous
functions in the electrically operated
•
initial lifting is practically straight up measuring principle (absolute encoder).
system. enabling the use of a standard seal all In specific panel positions the control
around the hatch cover panel system automatically allows high speed
drive and lifter
•
the motor and its mounting are panel travel. Low speed movement is used
Large bulk carriers are in most cases disconnected from the panel when the near the end positions and in high torque
equipped with side-rolling hatch covers
and there are two types of drive for
a schematic of the
opening or closing them: chain drive or
Macrack control
rack-and-pinion drive.
system.
For both drive options there are
two ways of lifting the panels before
side-rolling: pot lifts (which can also be
described as hydraulic jacks, or wheel
lifters), or ‘Roll-up-Roll’ lifters.
With the pot lifts, cleating is performed
by manual quick-acting cleats or by
hydraulic cleats. The Roll-up-Roll system
enables automatic cleating to be adopted.
The new MacGregor solution, the
MacRack, is at the same time a rack-and-
pinion drive and a lifter system. When
opening hatch covers the lifting force
needed is achieved by the MacRack lever
66 The Naval Architect February 2010
NA Feb10 - p65+p66+
p68.indd 66 02/02/2010 15:37:03
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76