1. SECTOR REPORT
JUNE 201636 LIFT & HOIST INTERNATIONAL • LIFTANDHOIST.COM
THE rapid pace of globalisation is
transforming the shipbuilding business
to new heights these days. In this study,
particular attention has been paid to
the various types of level luffing crane
designs available, that impact most
significantly on shipbuilding operations.
This paper also throws light on
establishing the investment cost of each
type first—its “cost-to build”—and then
its operational efficiency, i.e. the speed,
accuracy, and downtime of each crane
type, are also investigated.
The load path during level luffing
requires the height of the boom head
sheave and its distance from the load
to remain constant so the load travels
horizontally. The advantages of level
luffing are that the crane’s hoist does
not have to make adjustments to
allow for the vertical movement of the
hook or load; and more importantly,
the luffing mechanism must only raise
the deadweight of the boom so no
additional work (in the mechanical
sense of the word) is required, and no
unnecessary energy is used.
There are three types of cranes
generally used: goose-neck level luffing
crane, single-jib crane with normal
luffing and single jib crane with level
luffing. The evaluation criteria when
choosing a crane are: its rating;
its operational criteria and the the
investment criteria
Rating: For these types of crane no
internationally accepted standard exist
for assessing the rating. They cannot
be assessed by its highest load carrying
capacity, though in American terms such
as an “A ton crane,” are used, which
are only useful while comparing exactly
the same type of crane. On the other
hand Europeans would like to define the
“Load Moment”. At ‘X’ m radius ‘A’ ton
capacity crane is represented as ‘AX’
t-m, and at ‘Y’ m radius ‘B’ ton capacity
crane is represented as ‘BY’ T-m. So, it is
clear that the European ratings are not
directly proportional to the American.
Operational Criteria: Operationally
a crane is assessed by its speed and
accuracy. Further, the efficiency of
design can be measured in terms of the
energy it consumes in achieving these
primary goals.
Investment Criteria: The actual cost
incurred to install a crane is considered
to be the principle criteria for selection
of a crane though technically the duty
of the crane plays an important role
for selection. Maintenance and running
cost must also be appraised while
selecting the most suited crane. Many
organisations specify a crane merely
on the basis of maximum load to be
handled, even though the lift may be
performed once every few months
or once in a year. It would be more
economical to select a set of two cranes,
which may perform at least double and
can jointly can handle the maximum
load whenever required.
The decisive figure in initial crane
investment is the estimated job-hour
cost. Based on this figure, an appropriate
duty-mix can be developed.
CHOICE 1
Goose Neck/Double boom
vs Single boom
Straight single boom cranes have
traditionally been used in Asia and the
US, while the double boom cranes have
a large population in Europe. During
1980s and 1990s in the worldwide
shipyard market, all new cranes have
been single boom cranes. The double
boom cranes have been built in Europe
at a higher price aimed at earning
foreign currencies. As part of philosophy
of offering the best solution for client’s
applications, general recommendations
are one over the other once we
understand what clients actually need
and how the cranes will be used.
The main operational features of a
straight boom crane are:
1. Mother boom is one part only;
2. Winch mechanism as standard:
Loads are lifted through winch, hence
crane capacity and winch capacity
are the same;
3. Loads are lifted through hook linked
to winch with a wire rope system;
4. Hook can be raised and lowered
through wire rope system; and
5. Hook can also be raised and lowered
through mother boom luffing.
The double boom cranes are
available in different types for different
purposes. Normal double boom cranes
are used for handling all types of
cargo, from container handling to the
LEVEL LUFFING CRANE
Mukulesh Debnath, assistant general manager at McNally Bharat Engineering Co.,
investigates the selection process for a crane used in a shipbuilding yard.
MARINE CRANES
About the author
Mukulesh Debnath
was born in Kolkata,
India, on December
11, 1973. He is a
B.Eng (Civil), M.Eng
(Structural) and PhD.
Gathering
experience in heavy engineering
companies in 2008, he joined
McNally Bharat Engineering Co. Ltd
as assistant general manager. He
is an expert in health inspection of
steel structures and port handling
equipment. He has also designed port
handling equipment and has expertise
in their fabrication and erection.
He has published nine
international journal papers and given
many papers in various national and
international conference proceedings.
There are three types
of crane generally
used: goose-neck level
luffing crane, single-
jib crane with normal
luffing and single
jib crane with level
luffing.

2. MARINE CRANES
38 LIFT & HOIST INTERNATIONAL • LIFTANDHOIST.COM JUNE 2016
SECTOR REPORT
unloading of bulk and scrap materials.
Kangaroo cranes are mostly used for
bulk unloading and balance cranes are
developed for bulk and scrap metal
handling in the recycling industry. The
double boom crane has a more complex
construction, then a single boom crane
due to its main and auxiliary boom
and pivoting points, but has the main
advantage of an almost horizontal
path of the load during luffing. This level
luffing gives more precise and simplified
positioning of the load or grab, which in
turn enables the crane to handle more
loads which leads to higher production
rates. They are used for handling all
sorts of cargo, from general cargo, bulk
and scrap materials, to containers, and
have SWL’s reaching up to 250t with
outreaches from 8m up to 70m.
CHOICE 2
Level luffing or normal luffing
cranes used in shipyards may be
classified in three categories, according
to its capacity:
1. The Heavy Duty Crane: This type
of crane lifts load in the capacity
starting from 25t upto 200t. Such
lifts are required occasionally and
never used on a continuous basis. In
general, such lifts are purely hoisting
with little need for simultaneous
luffing.
2. The Medium Duty Crane: The load
range for this type of crane is 15t to
60t. This type of lifting range is very
common in shipyards. Since these
types of cranes are characteristically
used in fitting-out berth/jetty, the
loads may have to be fairly accurately
placed. Accurate movements will
be required in both vertical and
horizontal direction.
3. Light Duty Crane: The load range of
low duty cranes are in the range of 5t
to 25t. These cranes are highly mobile
and work in conjunction with heavy-
duty crane.
The double-boom crane has a more complex
construction than a single boom crane due to its
main and auxiliary boom and pivoting points,
but it has the main advantage of an almost
horizontal path of the load during luffing.
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3. JUNE 2016 LIFT & HOIST INTERNATIONAL • LIFTANDHOIST.COM 39
SECTOR REPORT
Since heavy lifts are performed slowly in
hoisting and luffing, and very careful movement is
required, speed will never be an essential feature
in heavy-duty operation. The advantages offered
by level luffing cranes may not be required. For
heavy duty cranes normal luffing offers perfectly
adequate performance at appreciably lower cost.
However, fitting out a crane of medium capacity
provides a benefit from its ability to move loads
horizontally with speed and accuracy.
When the load path is obstructed and the
load is required to move around obstructions,
then a level luffing type crane plays an important
role. The light duty crane performs horizontal
movements many times during the day, and
as such, the level luffing version of the crane is
most preferable. When the light crane performs
a vertical load movement, then a normal luffing
crane is good enough.
So the recommendations are as follows:
Normal luffing for heavy duty lifts; Level luffing
for medium duty lifts; and Normal/level luffing as
appropriate for light duty lifts.
Crane types:
Goose-Neck Level Luffing Crane:
The “gooseneck” crane, sometimes
known as the double-boom or
double-lever boom crane, is the
best known means of achieving
level luffing. In principle, the
goose-neck crane consists of three
booms, two of which are hinged
to the main slewing element of
the crane. The strut boom, which
is also called the main boom or
compression boom, is hinged at its
top-most end to the fly boom.
The quadrilateral formed by the
three booms and the structure of
the crane is constructed so that
when the main boom is raised
or lowered, the outer end of the
fly boom remains at a constant
height.The end effect is that the
hook/load remains at a constant
height, and perfectly horizontal.
The Single-Jib Crane with
Normal Luffing:
The single jib slew crane consists
of a single jib hinged to the main
slewing structure of the crane.
The jib is raised and lowered by
a simple rope, which passes over
a pulley at the top-most point of
the main structure. The hoist rope
uses the four-fall, simple-reeving
system. Using this rope system,
level luffing cannot be achieved.
Single Jib Level Luffing Crane:
This crane is constructed in the
same way as a single-jib crane. The
difference is that a 2-fall, three-
reeving hoist rope system is used.
In fact, this system acts as a “rope
store” or “rope compensator“
taking in and paying out rope
as necessary to achieve a close
approximation to level luffing.
The goose-neck crane consists of three
booms, two are hinged to the crane’s
main slewing element.
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