Feature 4
MacRack side-rolling hatch covers are a
greener solution
Cargotec has developed a second generation of fully electrically-operated
MacGregor side-rolling hatch covers following its success with the E-Roll
system. Torbjörn Dahl and T. Laakso of Cargotec Marine, Finland describe
the system.
D
evelopment of the electric-drive improvements were needed. A for hydraulic power packs and valve
side-rolling hatch cover started development project focusing on the stacks, and replacing hydraulic pipework
in 2001 in response to the safety, technical limitations and cost of with electric cables. Cables can be
Japanese car industry’s ambition to make electric drives has now resulted in the installed by less-skilled personnel than
its supply chain as ‘green’ as possible. The launch of ‘MacRack’ that employs an the mechanics needed for hydraulic
answer to this challenge was to launch the enhanced control system and just one pipework. More electrical cabinets with
‘E-Roll’ side-rolling hatch cover system. electric motor per hatch cover panel. motor control functions will be required,
E-Roll’s components and control but most of the skilled electrical work is
system were essentially developed from Introduction inside these cabinets and is done by the
scratch because similar systems for the Ship operators and shipyards increasingly supplier in a workshop ashore. The net
marine and bulk carrier environments appreciate that environmentally-friendly effect is to, therefore, minimise work
did not exist. After extensive tests and a ships are competitive. Electric drives offer onboard by moving it ashore – giving
lengthy component selection process, the them many advantages compared with slightly higher equipment costs, but
first orders were signed in 2006. Ten ships hydraulic versions, such as: hydraulic oil lower installation costs.
using E-Roll systems are in service but leakages are eliminated; there is no need Comparing the costs for electric and
this number is growing rapidly: another to fit hydraulic pipework onboard; electric hydraulic drives shows that these are
21 shipsets of equipment are on order and drives are easy to monitor and maintain; basically the same overall. However for
about 20 more are in the pipeline. and electric drives offer energy savings. individual items or systems the cost of an
As with all first-generation technology, Having identified a need in the electric drive should not be higher than its
market for cargo systems that use hydraulic counterpart.
Advantages of an electric drive environmentally-friendly electric drives Hydraulic drives need power packs
compared to hydraulic systems several years ago, Cargotec’s development using electrically-driven pumps. These
policy for electrically operated MacGregor pumps are not 100% efficient, and systems
For the shipowner: systems had three main aims. Compared with the variable-displacement pumps
•fast and easy to operate with hydraulic drives the electric-drive used for most cargo systems also consume
•no pollution from hydraulic oil versions had to be more environmentally- power in idle. This could result in a higher
•maintenance friendly with friendly, have equal or better performance electrical consumption compared with
simplified inspections and cost the same or less direct electric drives.
•operation position is not limited For some years, many shipowners
•cost savings, initially and during have tried to minimise the use of General Design
ship’s lifetime hydraulic oil onboard. One reason for The electric-drive design work covered
•energy saving as no continuous this is that certification (ISO 14001 for three areas: mechanical design, electric
running example) requires them to minimise design, and electronic control design.
•no cold climate sensitivity the environmental impact of their Hydraulically operated mechanisms
•high reliability operations. can be replaced with electrically operated
•easy to monitor Oil should not leak from hydraulic- versions. Such a device can be divided into
drive equipment that is properly designed, two main parts: the mechanical part and
For the shipyard: maintained and uses quality components. the actuator part.
•installation friendly (plug and play) However, simply not using hydraulics The mechanical part is in most cases the
•no pump and hydraulic pipes to fit removes the pollution risk entirely, as same whether hydraulically or electrically
•no system to flush well as the possible risk of hydraulic oil operated. However, if design changes
•no hydraulic control stand damaging cargo which could be an issue are required for some sizes/types, the
installation required for some ship types. new mechanical parts will be designed
•cost benefits A major difference when adopting according to the same criteria and
electric drives is eliminating the need safety factors applied to all other similar
The Naval Architect February 2010 65
NA Feb10 - p65+p66+p68.indd 65 02/02/2010 15:35:56
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