Ships of the Year

SHIPS OF THE YEAR
cargo pumps have a capacity of 12 x 250
cubic metres per hour at 12 bar.
The Excello has a diesel-electric machinery
with podded propulsion – so far quite a
rare arrangement in a cargo ship. The first
vessel in the fleet to be equipped with this
type of propulsion was the Prospero, delivered
in 2000. Mr Nilsson says that a decisive
advantage when the company went for
this solution was the compact size of the
engine room.
A diesel-electric machinery
with podded propulsion
increased the contract price
by eight per cent.
“A diesel-electric machinery with podded
propulsion increased the contract price by
approximately eight per cent compared to
a conventional machinery arrangement but
it means about five per cent more cargo
capacity”, he stresses.
“Another advantage is the outstanding
manoeuvrability, which means less need
for tugs.”
Propulsion is provided by two ABB
Compact Azipod electric main propulsion
and steering devices with an output of
3,200 kW each. On the sister vessel Evinco
there was one pod, but two units mean better
manoeuvrability and improved redundancy.
Both vessels are built to the DAT
(Double Acting Tanker) concept and moves
stern first in difficult ice conditions.
Four generators
Electrical power on the Excello is generated
by four ABB generators. As prime
movers there are three diesel engines of the
type Wärtsilä 6L32 with an output of 3,000
kW each and one of the type Wärtsilä 4L20
with an output of 720 kW. Normally one
of the large engines is running during discharging
of cargo and the small engine during
loading. At sea two of the large engines
provide sufficient power both in ballast
and loaded conditions. If the maximum
speed of 14.5 knots would be required
all of the three large engines are running.
The Wärtsilä 32 engines are equipped with
common rail, enabling operations on low
load down to 20 per cent without generating
smoke and soot.
Mr Nilsson says that four main engines
also provide additional flexibility.
“Service and overhaul of one of the
engines is possible even underway, which
is not the case with a conventional machinery
and only one main engine. Another
advantage is that the same engines provide
energy for both propulsion and cargo handling,
which means less engines to serve.”
Mr Nilsson points out that the large
capacity for generating electrical power
means that there is a virtually unlimited
power supply when discharging. The efficient
inert gas plant from Unitor has a
capacity of 2,500 cubic metres per hour
and includes three Atlas Copco compressors
of 330 kW each.
“I doubt that a conventional tanker
could operate such a plant and simultaneously
use the cargo discharging pumps on
maximum power. I think that we are able
to reach a total discharging power of 3,500
kW, which indeed is far from the maximum
installed power of 9,700 kW”, Mr Nilsson
thinks.
Extensive automation
The machinery is started from the bridge. In
just a couple of seconds the power management
system starts at least one large engine
and the ship is ready for manoeuvring.
“This is a safety issue as it is possible
to leave the quay fast if there for example
36 SCANDINAVIAN SHIPPING GAZETTE • DECEMBER 19, 2008