Wave compensation technology broadens the scope of application for fl oating cranes

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13 Φεβ 2012 (πριν από 5 χρόνια και 9 μήνες)

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CRANE OPERATIONS The Dutch company Barge Master BV has created a solution that provides more time to carry out operations when using offshore fl oating cranes. Wim Boogert, sales manager for Offshore Technology at Bosch Rexroth BV, describes the required wave compensation technology that offsets lifting, rolling and tilting movements with a moving platform between the crane and the hull.

Wave compensation technology
broadens the scope of
application for fl oating cranes
CRANE OPERATIONS
The Dutch company Barge Master BV has created a solution that pro-
vides more time to carry out operations when using offshore fl oating cranes. Wim Boogert,
sales manager for Offshore Technology at Bosch Rexroth BV, describes the required wave
compensation technology that offsets lifting, rolling and tilting movements with a moving
platform between the crane and the hull.
I
n the past, jack-up fl oating
cranes were used on a regu-
lar basis to install offshore
wind energy plants. They have
extendable legs that push into
the sea bed. The cranes lift
and lower big loads, without
being largely affected by the
sea swell. However, the area
that they can operate in is
limited to relatively shallow
waters with a stable sea bed.
The running costs for these
vehicles are very high, and
increase even further due to
the need of moving the jack-
up fl oating cranes to and fro
between the harbour and the
area of operation.
Standard fl oating cranes are a
much more cost-effective op-
tion. However, they can only
be used in very calm waters
– even those with the latest
technology. It only takes gentle
swaying of two to three degrees
for the top of the laden crane
to move 4 to 5m, which would
also put the crew at a certain
risk. In order to fi nd a solution
to this problem, Martijn Kop-
pert founded the Dutch com-
pany Barge Master BV, together
with Jan-Paul van der Bos.
Current standard fl oating
cranes start having problems
with wave heights of as little
as 30cm, and safe operation
can no longer be guaranteed
from this point. The particular
challenge for Barge Master was
the fact that there had been
no product on the market de-
signed to carry out this type of
effi cient wave compensation
process. The start-up business
could not implement this kind
of development alone, and
brought the idea to Rexroth’s
Marine and Offshore branch
management team. The ob-
jective was to develop a com-
plete solution with all of the
necessary control and drive
technologies and third-party
components.
The wave compensation technology
from Bosch Rexroth increases the
scope of application for standard
fl oating cranes up to signifi cant wave
heights of 1.5m
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OFFSHORE INSTALLATION
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Wave compensation
lowers costs
Floating cranes hold loads over
a very large and fl at hull, and
this makes them very sensitive
to motion of the sea. Large
waves in particular, which even
on calm days occur frequently
at sea, quickly tip the crane off
balance. The wave compensa-
tion technology designed by
Bosch Rexroth offsets the lift-
ing, rolling and tilting move-
ments by means of a moving
platform between the crane
and the hull. This solution
offers a key advantage by be-
ing suitable for use with both
standard ships and standard
cranes, therefore resulting in a
decrease in manufacturing and
operating costs.
This wave compensation tech-
nology is currently designed
for cranes weighing about
400 tonnes and having a cargo
load of up to 160 tonnes. Three
vertically mounted hydraulic
cylinders connect the crane
to the ship with ball-bearing
joints. Integrated fl exible con-
necting rods freeze the remain-
ing three degrees of freedom
in order to allow the cylinder
movements to compensate for
the sea swell.
The key factor of this solution is
the control system for hard- and
software developed by Rexroth.
Special sensors, known as mo-
tion reference units, record data
from the ship’s movements.
They detect linear and angular
accelerations and positions.
The control system uses this
data to calculate the target val-
ues for the cylinder speeds and
positions, in order to maintain
the stability of the platform by
the compensation of move-
ments. In accordance with the
data from the control system,
the motion controls close the
control loop decentrally via
servo valves, thus enabling the
cylinders to move in a precise
and dynamic manner.
The cylinders have one passive
area of operation to compen-
sate for the total static load
and two active areas of opera-
tion for push and pull in or-
der to offset dynamic forces.
The passive offset takes places
via a primary cylinder, fi lled
with oil and nitrogen. With a
maximum stroke of 2500mm
and an external diameter of
559mm, the cylinders reach a
maximum speed of 0.82m/s.
The CEC 2.2 solution devel-
oped by Rexroth protects the
hydraulic cylinders from cor-
rosion. A watertight shielded
valve block is fi tted to each cyl-
inder. Along with the valves,
two HNC100-3x motion con-
trols and sensors, this valve
block regulates the cylinder
movements in accordance
with the data from the control
system. The integrated CIMS
distance measurement system
transmits highly accurate data
regarding the actual current
position of the piston rod.
A hydraulic unit with three mo-
tors, each with two hydraulic
pumps, generates a maximum
total output of approximately
1.5 MW and supplies the neces-
sary volume fl ow for the cylin-
der movements with an active
maximum force of 1670 kN.
A piston accumulator also
supplies pressure for the peak
loads.
A high level of redundancy en-
sures operation in the event of
a component failure. Rexroth
has integrated three distance
measurement sensors and two
motion controls with sensor
valves at each cylinder. If a mo-
tor pump unit fails, the motion
controls supply a suffi ciently ef-
fective volume fl ow to ensure at
least a limited level of operation.
The PLC controls are equipped
with two processors each.
Stability in waves
Barge Master covers three de-
grees of freedom via existing
anchoring technologies or a dy-
namic positioning system. Wave
compensation technology sig-
nifi cantly broadens the scope of
application for standard fl oating
cranes. Even in the event of ir-
regular swell, with wave heights
of up to 1.5m and a frequency
of six to 12 seconds, about 95%
of the movements are balanced
out, and the crane is kept in a
stable position.
From the idea and simulation
up to testing with a model and
the production of a prototype,
Barge Master BV has worked
in collaboration with its sys-
tems and development partner
Rexroth to develop a solution
that considerably increases the
scope of application for fl oat-
ing cranes. The solution is suit-
able for all standard ships and
cranes, and therefore reduces
manufacturing and operating
costs for offshore work.
Rexroth was able to simulate
the complete drive and control
system on a computer as early
as the project planning stage.
At the beginning of 2011, the
Maritime Research Institute
Netherlands (MARIN) con-
fi rmed the effi ciency of the
wave compensation technol-
ogy for the fi rst time outside
of computer models, based on
extensive testing with a 1:18
model. In January 2011, the
creation of the fi rst fl oating
crane with Barge Master was
started. Rexroth is supplying
the pre-fabricated drive and
control system to the shipyard
and putting it into operation.
The C400 Barge Master will
be ready for operation in the
middle of 2012, and will sig-
nifi cantly widen the scope of
application for fl oating cranes.
At the same time, Barge Master
will be starting to market the
solution for standard ships and
cranes.
The wave compensation technology from Rexroth offsets motions in all six degrees of freedom thanks to a moving platform
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