Flat-tops Take Over The World
4/22/2009
Published on April 18th, 2008
What started as a way-out alternative by a few maverick tower crane manufacturers
has now become so popular that it is the default position for some new manufacturers,
reports Heinz-Gert Kessel.
When Linden produced the 8000 series, in 1975, its sophisticated modular design
astonished many in the crane industry. Despite the groundbreaking design, the
crisis hit demand for high capacity tower cranes.
Comansa took over the design rights and expanded the crane range, focussing more
on smaller 100-200t class cranes, for which there was broader demand. It was Franc
Jost who rediscovered the flat-top saddle jib crane concept, realising it in 1990 with
BKT in an erection and transport friendly manner as the 80tm city crane. During his
time with Terex-Comedil of Italy, and later on at his own Germany-based company
Jost set further milestones in the development of flat-top cranes, extending their
capacity range into the 700tm class.
in their range. Some traditional market leaders, like Liebherr and Wolff of Germany
and Potain of France, see this crane breed as an addition to their traditional saddle
jib crane line. For them, flat-tops are increasingly important, particularly in the city
class range and up to the 300tm class.
Big flat-tops
Some manufacturers see declining benefits in the flat top crane design when it is
applied to high capacity cranes, arguing that an overall jib section profile above 2.80m
and the high weight of the jib cause logistical problems in many countries. Other
companies though point out that sectional upper crane rigging is far more flexible than
conventional high capacity crane design.
For example ZS, based in Nanjing, China, is delivering real giants for the domestic
power station construction industry. The ZSC60300 boasts a maximum capacity of 80t
at 25m radius in 8 fall operation mode. Even at a radius of 60m, the 2,000tm class flat-top crane can still lift 30t. The ZSC70240 even provides a tip load of 24t at 70m radius.
In Europe, the Linden 8000s delivered to Poland in 1978 are still among the biggest flat-top cranes ever built. At the moment one unit is operated by crane rental specialist
Sarens at the Bełchatów power station construction site in Poland, where it is working
with a 58m jib. On a 5.8m x 5.8m mast the crane reaches a free standing height of
148m and can lift 50t at 16.6m radius.
The Linden 8000s at Bełchatów was used first on the construction of a stair tower for
the plant's boiler house. The crane has now been transferred to the cooling tower site,
where it will reach an under hook height of 198m, only anchored two times at 108m and
160m height using a guying system. The Linden self jib dismantling device will climb
down the crane inside the finished hyperbolic concrete structure.
Latest trends
The growing success of the new Liebherr EC-B range is based on the crane's
sophisticated assembling technology and the 20% greater load capacity available
on the Litronic version at the touch of a button. The youngest member of the new light
weight flat-top crane series is the 30EC-B2.5, following the 30LC city crane. At 30m
jib-end 1t can be handled. While the counterjib of the small city crane only carries
the ballast plates, the trolley winch is unusually located aside the jib foot, along with
the hoisting winch. This facilitates aerial rigging by helicopter. No module is heavier
than 1.5t.
In the medium capacity class, the Terex-Comedil CTT231 moves away from the
original Jost design features in the traditional Terex-Comedil flat-top crane line.
Instead of the massive hammerhead-like first jib section on the top of the tower,
only a compact tower head is used as the connection point for the flat counterjib,
which is fitted with pendants. The compact hoisting unit can be left in place on the
counterjib during transportation. Depending on the assistant crane’s capacity,
the complete upper crane with maximum 70m jib and 10t or 12t maximum load
can be installed in four lifts.
maximum jib length. Just carrying the ballast, the compact counterjib can be folded
for reducing transport length. At the back of the slewing unit the machinery platform
is located under the counterjib, in the same way as on the ancient Peiner KL series
cranes, providing direct access by the cabin platform.
Raimondi has a long tradition in flat-top city cranes. It extended its line into the
higher capacity class by introducing the MRT243. Its extraordinary trapezoidal
boom foot shape permits reduction of wind force and gives the long pendant free
78m boom the required rigidity and torsion fluidity. Tip load is 2t while maximum
capacity is 16t. The crane can be installed in a 95m free standing version. A minimum
boom length of only 24m demonstrates the flexibility of the crane design to cope with
narrow site conditions.
With the export market in mind, Spain-based Saez has some long jib flat-top cranes
in the pipeline. The TLS8024 will be available in a 24t version with 80m boom and 2.6t
tip load capacity in September 2008, while the smaller TLS7516 with 16t maximum
capacity and 3t at 75m is said to have been on the testing ground in March 2008.
Following Jost’s flat-top crane design principle, DKT recently manufactured the
massive DT912-40 with 40t maximum capacity and 7.5t maximum load at 80m radius.
Like the modern Jost tower cranes, the DT912-40 is equipped with a side mounted
control unit made up of a comfortable cabin and a walk-in electric cabinet.
The latest compact flat-top crane concept developed by Jost is the JT132.8. This
has a side mounted retractable cabin unit which can be left in place for transportation.
A licensed copy of the crane, the JT140-8, is manufactured by Shenyang Peter’s
in China, delivering flat-top cranes in Jost design to the Asian market.
Meanwhile, in Europe, the first fruits of the Jost's co-operation with Netherlands-based Kranenbouw are visible. According to Frank Crombe, the Dutch company is
specialising their manufacturing capacity on the middle size class M series Jost
flat-top cranes.
At the time of writing a JT312 with 64kW hoist (instead of the standard 45kW unit)
was assembled at Kranenbouw for a high rise construction project in the UK. The
crane has a maximum jib length of 80m with 1.8t tip load. In one year, already about
25 units of the 300tm class crane have been delivered.
Growing building activities have supported the development of BCT (Baltic Cranes
Technologies), based in Vilnius, Lithuania. Besides many second hand Zeppelin flat-top tower cranes, new BCT80 cranes are to be found in the booming construction
market of Lithuania. Besides minor updates, the BCT80 follows the design principle
of the Zeppelin ZBK80. The 80tm version representing the roots of Franc Jost’s flat-top crane development. BCT offers a BCT140 with 60m jib and 8t maximum capacity,
showing substantial design improvements on the Zeppelin ZBK132.
San Marco International of Italy offers a flat-top city crane range up to 67.5m radius
with 1.6t tip load. The cranes follow the Italian city crane design with the trolley and
reeved hook parked at the so-called 'trolley jib' on the complete tower head.
This means the complete upper crane can be installed in two lifts without needing
to reeve the hoist rope.
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