Tower cranes: A tailored solution
By Laura Hatton13 September 2013
Japan’s IHI uses experience gained from a long history to offer customised jib cranes that are individually designed and manufactured to address the requirements of each customer. Heinz-Gert Kessel reports...
Most people outside Japan in the crane industry probably know IHI as a manufacturer of crawler cranes and maybe also as one of port and shipyard lifting equipment. Less well known is that tower cranes are also significant in its crane range.
The Japanese IHI group has expanded its business into various fields over the years, beginning with shipbuilding in 1853 then, using its mechanical engineering experience, developing industrial plant systems and equipment, including blast furnaces, power generation plant and LNG storage plant. Current expansion is in the area of aero-engines and aerospace.
IHI Corporation, formerly known as Ishikawajima-Harima Heavy Industries, is still one of the larger heavy industries groups in Japan. Its material handling systems range from general purpose industrial cranes like overhead and jib cranes, sea to shore cranes and construction cranes, to bulk handling systems for the power and steel industries and even automated storage and car parking systems.
In 2007 all the material handling and parking systems businesses in the IHI group were put into Ishikawajima Transport Machinery Co.,Ltd., also called Ishikawajima Unpan Kikai (IUK). Later in 2009, IUK was renamed IHI Transport Machinery Co., Ltd.
The development of climbing tower cranes for high-rise construction can be traced back to 1966. That was when the first two Kure KTK-200W floor climbing cranes were raising the 147 metre Kasumigaseki Building in Tokyo. A patented climbing system, of jacking the machinery platform of the crane alongside the new crane mast sections being inserted through the slewing ring, became a characteristic basic design feature for nearly all Japanese climbing cranes.
Tower crane applications in Japan have specific requirements. An example is high wind resistance of up to 55 m/sec to withstand typhoons. Another is strict safety requirements concerning earthquake resistance. A luffing boom design is used to cope with neighbourhood oversailing restrictions and there is a move to raise efficiency of construction machines by using sophisticated control systems. Combining all the above has led to development of a specialized breed of rigid and high technology construction climbing cranes for the domestic market.
In 1963 building height restriction permits were opened up in Tokyo, which meant the development of a high rise building construction industry in Japan where KTK (Kure Tower Krane) internal climbing cranes found a ready market. When the crane manufacturing division of Kure Shipbuilding & Engineering was integrated into IHI in 1968, these floor climbing construction tower crane were known as JCC (jib climbing cranes) series cranes. Capacity was increased over the years from 200 tonne-metres in 1966 to 70 tonnes capacity and 1,500 tonne-metre units in 1990.
Outside Japan tower crane manufacturing has become a more and more modular series production process, with runs of generally at least 10 similar units. These are designed to meet, as closely as is reasonably possible, a universal set of rental company requirements. Tower crane production in Japan, however, differs significantly. Annual production at IHI is between about 10 and 30 cranes. The company’s Yasuura Works delivers around 70 to 80 % of all climbing cranes manufactured in Japan.
While many climbing cranes were supplied during the “bubble economy” era in Japan, the market has shrunk since the early 1990s. Rising popularity of prefabricated units and steel structures being used for high rise building construction has made the 500 to 700 tonne-metre capacity class the best seller, according to Ito Tadashi, IHI overseas sales department manager. For apartment building projects, where there is more work with precast concrete elements, the 300 tonne-metre class crane is in demand. For 2013 IHI secured contracts of 12 new units and, during IC’s visit in February, three cranes were in fabrication while a new prototype in the 500 tonne-metre class was on the test pad.
In contrast to Europe, where tower rental crane companies are dominating the market, in Japan many cranes are designed in close relationship with the customer, often general construction companies which buy the cranes to integrate them into their own fleet, to address their special building project requirements and their individual ideas of crane application. Only since the late 1990s have lease companies established by construction companies also been purchasing tower cranes.
A remarkable improvement of the JCC series cranes was the 1969 introduction of a safe, easy and fast hydraulic climbing system. It was for the JCC200H and followed the tricky conventional wire rope operated climbing mechanism used until then. In addition, the constant 4 line fall operation mode become standard. That meant no risk of the hook rope twisting due to a tandem hoisting drum where one hook rope is stored as S-laid on one drum and the other being Z-laid. The hoisting motor operates both drums’ ropes so the speed is doubled, unlike on conventional European-designed tower cranes.
A further milestone in reducing overall construction times is the JCC-V series introduced by IHI in 2000. Major improvements included the following:
* Crane component weight reduced by 13 to 17 %.
* Erection procedure is facilitated and speeded up by using more pin connections, which also reduced the number of bolts by 20 %.
* Free standing tower height extended from 30 to 45 m. Instead of the tubular mast sections connected by 48 screws a square mast section with just 40 connecting screws became standard.
* A patented complex and expensive floating sheave block (FSB) provides optimum accuracy level luffing and minimises load sway by reducing the deflection of the jib. Improved accuracy is specially requested for the installation of welded steel structures now generally being used for high rise construction. In addition, the unique luffing rope reeving concept reduces the power requirement for jib movement.
* Inverter-controlled drives for all movements, a monitoring system with touch sensitive display, and an internet-based remote maintenance function add to the versatility of the JCC-V series cranes.
For the prestigious 634 m high Skytree Tower project in Tokyo, in 2009 IHI supplied three JCC-V720AH climbing cranes and one JCC-V600, which further pushed the borders of crane design. The appendix AH stands for Advanced and High Lift, indicating the custom-designed extra features for this spectacular ultra-high climbing crane application in Japan. Offering a capacity of 32 tonnes at 22.5 m radius, a hook height of 420 m can be achieved at 30 m/min under full load.
Where the cranes had to operate at extreme height they were proved to withstand 100 m/s wind speed with a mast system 15 % more rigid than the standard type. In addition, the cranes had to be installed close to one another. Booms had to be stored at a steep angle in the out of service position. An patented jib restriction device, made up of a second luffing winch held back the jib acting against the main luffing winch with the jib parked, was developed by IHI. It also adds to the luffing capacity when the jib is raised. Using the Slewing Assist Function (S AF) the cranes were synchronised and moved by on board computer systems in the out of service condition to orientate all the jibs in the same direction following changing wind directions. Under working condition a GPS-based three dimensional collision-avoidance system fulfilled the contractor’s safety requirements.
To increase productivity, by simplifying and optimising the structure, and to reduce construction time, Japanese construction companies are awaiting further improvements in crane design. In response, at the end of 2012, IHI announced the JCC-TS series, where TS stands for the key design concept Time Shortening of Construction. The first example of this breed, a new series of climbing jib cranes, is the JCC-TS500 with a capacity of 20 tonnes up to 26.5 m radius and with a tip load of 10.5 tonnes at 42 m outreach.
The main improvements on the TS series JCC-TS500 include the following:
A simplified floating sheave block design to allow simple rope reeving and use of the same pendant ropes for all jib lengths. In addition, one truck load of crane equipment is eliminated, reducing the transportation costs, while retaining the benefits of accurate mechanical level luffing on the JCC-V series.
The square size of the mast system is restricted to 1.90 x 1.90 m, as it is for most Japanese tower cranes. It allows the mast sections to be climbed through the turntable. Maximum free standing height was again extended, to 51 m, achieved by combining 9, 7.5 and 6 m newly designed mono block mast sections with integrated large holes for the climbing operation.
A second hydraulic pump will be used during the climbing procedure to double the speed of retracting the hydraulic ram when it is not loaded. Time for the whole climbing sequence will be about two thirds of the original.
The already short floor climbing time of Japanese tower cranes is reduced further on. Originally the mast will be jacked in full length through the slewing ring before the machinery deck of the crane has to climb alongside the mast to its top to restart work. On the TS-series the crane upper will rest on outriggers while the whole crane, including mast, will be jacked through the climbing cage at the crane base section to allow floor climbing in one climbing process instead of two phases. The same mast sections are used for internal and external climbing as the ratio of external and floor climbing application in Japan is still 1:2.
The tail radius of the machinery deck has been reduced to 7.10 m to cope with increasingly restricted construction sites.
A mechanical device for detecting the sway angle of a suspended load is mounted at the boom head to allow fitment of a sensor-based sway control system. There is a simultaneous control system for vibration suppression and shock free load positioning in accordance with the length of the hoist line. A control system for tandem lifting operation by two cranes makes use of remote signals sent by the hook blocks of the engaged cranes to the board computer of the lead crane. This synchronized crane control avoids side pull on the load which may be caused by the long distance between operator and load.
Auto-tracking cameras and a remote monitoring system add to the new level of high functionality. All information and machinery dates are collected on one large touch panel display to assist the crane driver of the TS-series climbing crane. Such assistant control devices can in Europe only be found in advanced port crane solutions. By using the capacity of the inverter more effectively the lifting speed for the mid-range loads have being improved.
Testing and development
The two first JCC-TS500s will be tested under construction job conditions by the end of 2013. A smaller model, the 15 tonne capacity JCC-TS300 and a bigger model, the 25 tonne TC-700, will complete the new series. Both will follow similar design principles to the existing models.
The preference for floor climbing tower cranes led to the development of specialized roof mounted assist cranes to bring down the climbing crane after topping out. IHI offers three sizes of disassembly cranes, which can be combined to bring down even the largest JCC-V series IHI climbing crane. The largest unit is the JCC-V190SK with a lifting capacity of 16 tonnes at 12m radius. Smallest is the JCC-V10SK, which handles 1 tonne at 10 m radius.
Unique to IHI disassembly cranes is their climbing mechanism. A small crane mast can be inserted through the machinery deck by the crane itself and the upper crane can be jacked alongside this short tower. The resulting extra height of the luffing jib crane is a benefit when optimising the hook height to reach the A-frame of the floor climbing crane that is being dismantled. By this means the boom foot of the JCC-V190SK will be raised to 13.4 m above the building roof.
To reduce the required under hook height for an assist crane to remove the JCC-V190SK, a special rigging frame can be connected with the base boom section. By operating the luffing rope connected to the rigging frame, the A-frame can be raised or folded by the crane itself. Roof space is often restricted so IHI disassembling cranes can have a folding boom to reduce the dismantling space. All crane components can be split down into units to be picked and removed from the roof by the next smaller lifting device or by hand.
While IHI climbing cranes are so far produced only for the very special domestic market, customised jib cranes are delivered all over the world. For the shipbuilding industry IHI has developed a standard rope balanced level luffing crane concept. It boasts unique design features to improve exact load placement. Deflection of the boom caused by a load at long radius can increase the lifting radius. Here it is compensated for by the deflection on the two slim front tubes of the A-frame. In addition, the application of high tensile steel for the tubes forming the boom reduces dead weight.
All electrical, drive and control components are covered inside the spacious machinery deck to allow easy access. Also following these design principles are the rail mounted single boom shipyard cranes in the JC-N series with up to 300 tonnes capacity and 65 m working radius.
Individual crane designs are also developed for specific sites. Two portal mounted JC-300 and JC-600 travelling single boom cranes were delivered to Siberia for operation in a temperature range from -40 to +40 degrees Celsius. Special adaptations for cold weather included load moment indicators in separate heated boxes inside the specially insulated crane driver’s cabins.
Another example of a specially built crane is a land-based super heavy lift fixed slewing crane being erected in Angola, Africa, at the time of writing in mid 2013. The large lightweight ringer crane ordered by the Paenal Yard rotates around a central pylon on rail mounted carriers supporting the front of the triangular high frame portal of a heavy lift jib crane. The 2,500 tonne capacity crane will be used to lift modules for the offshore oil and gas industry. While the high frame portal is fabricated in Korea, the jib, made from high tensile steel tube, is welded in Japan. Using that steel means less weight, which reduces the load to the foundation and means cheaper installation. It also makes it viable to manufacture the main crane components in Japan.