Tower cranes: luffing it up
By Christian Shelton12 November 2018
New large luffing jib tower crane models are entering the high rise and general construction markets around the world. Heinz-Gert Kessel reports
All over the world a growing number of midtown high-rise projects above 300 metres are under development. To shorten construction time and improve build quality, larger precast and prefabricated modules are becoming common. As these modules get larger and become more complicated their weight rises dramatically. Prefabricated pre-finished volumetric construction (PPVC) is particularly popular in Asia. Large and heavy concrete modules weighing between 40 and 60 tonnes have to be handled. This calls for space-saving, high capacity tower cranes as an alternative to conventional mobile cranes.
Industrial or infrastructure applications, for example, wind turbine construction or high bridge pylon construction, add to the demand for larger cranes with higher load moments. These tend to be for a capacity of 80 tonnes or more at short radius. Manufacturing costs, short erection time and safety reasons mean fixed ballast designs are used.
The 400 to 500 tonne-metre load moment class has been a standard in skyscraper construction for years. It is now a crowded market. Leading tower crane designers have shifted their focus to the 700 to 1,000 tonne-metre load moment class.
In this class the first European frequency converter-controlled electric alternative to diesel Favelle Favco hydraulic luffers was the Wolffkran 700B, introduced at Bauma 2010. It was then followed in 2015 by the Liebherr 710HC-L.
A primary design feature of the 700B is a connecting block bringing together a lightweight folding counter jib, folding tower head section and triangular jib up to 70 m.
In addition to easy erection, connecting the jib above the back edge of the slewing ring allows a short minimum operating radius. Luffing and hoisting winches are on separate transport and erection modules bolted on top of the counter jib. Standard is a mix of concrete and steel ballast giving an 8.9 m tail radius. All steel ballast in the US version can reduce tail radius to 7.4 m. In the USA columns often have to be lifted off the street early in the morning before rush hour. During the day they are tailed and placed into position using an assist winch and fly jib.
Wolffkran 700B in standard version with a mix of concrete and steel ballast giving 8.9 m tail radius
On the power
Zoomlion used Wolffkran machinery deck design features on its luffing jib crane range, such as on the L630-50 and LH630-5 models, for example. These are diesel and electric versions of the same model. It is common practice among Chinese manufacturers to cope with poor power supply on construction sites or to benefit from the freedom of electricity supply to a crane working at extreme heights on ultra-tall towers.
An L630-50 electric and an LH800-63 diesel-hydraulic Zoomlion luffing jib crane working at a skyscraper construction site with two falls of rope
Standard tail radius is 9.4 m and 8.4 m on the short version while jib length is restricted to 60 m.
A current design trend followed by this crane is to minimise the number of falls of rope. It lifts 25 tonnes on one fall and the 50 tonnes maximum with two parts of line. Capacity at the 60 m maximum radius is 9.5 tonnes. Its tower is 2.50 x 2.5 m with a 63.05 m free standing height.
Soon to be delivered from Zoomlion is the giant LH3350-120, a 120 tonne capacity internal climbing diesel hydraulic luffer. Fellow Chinese tower crane manufacturers Yongmao and Zhong Sheng Construction Machinery (ZS) are following Favelle Favco design principles with a compact split machinery deck and diesel hydraulic or electric winches. Yongmao recently delivered a 100 tonne STL2400 for the Haikou Tower 1 project in Hainan Province.
Down the capacity scale is the Yongmao STL660C, which has an economical alternative to steel ballast. Arranging the four ballast blocks around the machinery deck allows a tail radius of 8.5 m and reduces ballast height compared with the typical stack of concrete blocks on top of the machinery deck. Diesel and electric versions are available, both with one or two fall operation and a capacity of 32 or 50 tonnes.
As with many Chinese crane manufacturers, Yongmao offers electric versions as well as diesel-hydraulic in the same capacity class. In this case the STL1000 with 50 tonnes capacity and 25 tonne single line pull has standard steel ballast
Yongmao diesel-hydraulic STL660C with a new 46 tonne concrete ballast arrangement used as internal climbing crane in Taiwan
High line pull and fast hoisting speed is essential for mega skyscraper construction. Liebherr designed its 710HC-L as an electric crane to offer just that but, at the same time, to consider the environment, reduce operating costs and increase safety.
Electric cranes mean no refuelling every few days, no risk of large hydraulic oil spillage, no risk of fire from flammable substances spewed on the machinery deck, and noise is at least 10 dBA lower. Electric tower cranes help comply with the emissions standards of today’s inner city sites while moment and overload functions can be controlled by the LMI. Sophisticated steering systems also allow less overall power consumption and horizontal load path and integrated monitoring systems can be used for anti-collision systems.
Liebherr designed the 710 HC-L so that it could recovered by just using a Liebherr 200DR 5/10, the 10 tonne capacity derrick. It avoids the extra steps of different sizes of the recovery cranes.
Competing Favelle Favco and Cornell diesel hydraulic luffers in this class meant only one or two fall operation would be accepted by high rise steel workers. Three fall operation was abandoned, partly due to a high risk of the hoist ropes twisting when operating at heights above 100 m. To help maximise rope life the design uses as few sheaves as possible between the hoisting winch and the jib tip section.
A short tail radius was required on the 710 HC-L so the hoist winch had to be placed on a second level above the centralised switchgear cabinet. Liebherr chose a 2 x 110 kw dual motor drive for 64 tonnes on two falls and 32 tonnes on one. Speed is up to 194 m/min in single line mode. The new 24 HC tower system allows 74.8 m free standing capacity on a 2.42 x 2.42 m tower with 30 m jib. All crane components, including the slewing ring support, fit into standard containers.
The all-new J780PA from Spanish manufacturer Jaso shares some design features with the Liebherr 710HC-L, for example, the machinery double deck. Its maximum jib length is 5 m longer at 70 m. The machinery deck is narrow and designed in two pieces to ease erection and reduce rigging load weight. It has one motor in parallel to the drum and the electrical cabinets are deep in the structure and well protected from bad weather. For erection the heaviest item can be reduced to 10 tonnes.
Double deck counterjib of the all new Jaso J780PA with one hoisting motor on top positioned parallel to the drum to save space
A new 220 kW winch will be available, providing 28 tonnes on a single line pull and a 310 m/min maximum lifting speed. Its capacity of 75 tonnes makes it the strongest European-designed electric tower crane in its class in three fall mode.
Just one hoist motor is needed to reduce overall power consumption and optimise output according to requirements. In this way power consumption is minimised when the required power for speed is less, for example, when the crane is working at a low hook height at the start of a project. The load moment functions are controlled by the LMI and also electromechanically, in both cases managed by electronic safety controllers.
Jaso has developed a gearbox where a constant input speed can provide multiple output speeds selected by the crane driver according to job requirements. On a one part line a slim line hook block is used. With two and three fall operation a semi-automatic change is possible. Unlike the Liebherr, the bridle and luffing rope on the Jaso are pre-installed on the counter jib to speed up erection.
The hoist rope runs inside the boom to reduce sway and to avoid relative movement between the hook and jib end when luffing. To minimise the size of the erection crane the counter jib and the A-frame are each split into two erection and transport units. Transport dimensions are optimised so a crane with 70 m jib and 37.8 m free standing tower can be shipped in 14 HC 40 foot containers and one FR40.
Maximum freestanding tower height is 86.1 m with a combined TSP20 and TSP24m tower system. Standard parking radius of the jib is 15 to 20 m which is impressive for this crane size and it can be further reduced with a parking device fixing the jib to the A-frame. Its full steel ballast means a lower centre of gravity and less wind load area. Tail radius is 9.5 m. A fly jib with a 9 tonne line pull will also be available.
In contrast to Wolff and Liebherr the Jaso crane’s winch is on the machinery deck for easy erection. In addition to the 75 tonne J780PA.75, a 132 kW version with 16 tonne line pull is available.
The first J780PA.64 was put to work on the prestigious Ribbon project at Darling Harbour in Sydney, Australia. It was rigged in 2.5 days under cramped site conditions on a 52.8 m free standing tower with a 60 m jib.
Top view of the wide hoisting winch platform in front of the Comansa LCL700 turntable
On Comansa’s LCL700, a unique design feature in the 700 tonne-metre class is the placement of the hoisting winch in front of the deck. The idea is to allow a more direct path for the hoist rope to the jib tip section and to reduce the space requirement at the back of the machinery deck. From the side mounted operator cabin the driver has a direct view of the hosting winch, giving visual additional control. The large 200 kW winch with its motor and gearbox, however, puts a wide structure in front of the slewing ring which could require longer tie-in supports when the crane is climbing alongside a building.
In addition, when the crane is delivered without a hoist rope the erectors have to pull the rope all the way up to the drum under the jib. Temporary holders along the jib have to be used. The size of the crane means the hook block is not rigged already reeved together with the hoisting drum as happens with smaller Comansa luffers. The LCL700, however, is delivered from the factory with pre-assembled luffing reeving which reduces erection time.
Installing the top section of the Jaso J780PA A-frame
An assist winch can be used to install the auxiliary ropes of the jib and the reeving pulleys without needing a truck crane. With concrete ballast tail radius is 9.5 m and with steel it is just 8.7 m. Change over from 64 tonne double fall to 32 tonne single fall operation is done mechanically. Maximum lifting speed is 170 m/min. A freestanding tower height of 69.8 m can be achieved using the 2.5 x 2.5 m D36 tower system.
Towers for wind
After entering the wind turbine construction market, manufacturer Krøll Cranes in Denmark adapted three of its K1650L models for general construction work. They were put to work on a massive Jurong Town Corporation Logistic Hub industrial logistic park project. Changes to the cranes included downgrading the capacity of 135 tonnes to 64 tonnes and transforming the typical jib nose for wind turbine installation into a light weight standard jib end section.
After minor modifications of the upper crane design, reducing the number of falls and replacing the boom nose with a standard jib end section for two fall operation, the Krøll K1650L becomes a versatile heavy lifter for precast concrete construction in Singapore
This general construction crane version delivered by local Krøll agent Buildmart Industries benefits from a high line pull of 32 tonnes and the fast rigging and easy transport devices originally developed for the wind turbine tower construction crane version. An example is the reeving of the luffing winch which remains installed during transport for the luffing winch located at the rear legs of the A-frame.
The walk-in electrical cabinet is integrated into the rear part of the machinery deck. A tail radius of 8.5 m is achieved by using 120 tonne steel counter weights and integrating the luffing winch into the A-frame. The split arrangement of the machinery deck is similar to cranes from sister company Favelle Favco. A semi-automatic fast change of the reeving between two-fall operation for 64 tonnes and one fall operation for 32 tonnes follows the design developed by Krøll for its K100L.
With respect to moderate project heights a 160 kW hoisting winch is used, offering a maximum lifting speed of 100 m/min.
An alternative is a 300 kW unit for up to 200 m/min in single fall operation for ultra-high construction projects. The lifting capacity could also be easily adapted to 96 tonnes with three part lines and 135 tonnes on four part lines.
The 4 x 4 m M40 tower can be dismantled into pieces for easy transportation. It is somewhat lighter than the monoblock M33 tower system on the wind turbine construction version. Both construction versions will allow 110 m freestanding tower height. The cranes are working on a 40 m freestanding tower and can lift 42 tonne beams at 35 m reach.
In addition to introducing a new ergonomic cabin, Favelle Favco has updated the M860D, now called M860DX. It has a redesigned jib head section and is available with 32 tonnes capacity on one fall, 64 tonnes on two falls and 96 tonnes on three falls. Lifting capacity has being significantly improved, from 7.1 tonnes at the 70 m maximum radius to 9.5 tonnes. Maximum lifting speed is 196.6 m/min. A 12 tonne capacity fly jib is an option on the M860DX. Its maximum freestanding height on the standard tower system is 64 m. Tail radius is 9 m with steel ballast blocks for easy handling.
All-new Favelle Favco M860DX surpasses the capacity of the well-known M860D
On the One Vanderbilt project in New York, USA, Favelle Favco M760Ds were installed very close together inside the central building core. The standard tail radius is 8.20 m but it was reduced to 7.63 m with a combination of long steel counterweight plates hanging at the rear, and one ballast block connected under the machinery deck. The crane provides 32/64 tonnes capacity in single and two fall operation. Maximum radius is 70 m and the auxiliary 12 tonne single fall hook makes it 74.37 m.
Diesel hydraulic cranes still dominate the Favelle Favco range but environmental concerns promote electric cranes. In many cities like New York a shortage of electricity requires large power pack type diesel site generators to run the cranes which is more negative in terms of pollution. While a diesel hydraulic crane might require 600 litres a week a typical generator for an equivalent electric tower crane alternative can quickly reach 2,000 litres.
Two custom-built Favelle Favco M760Ds with reduced tail radius of 7.63 m to fit into the concrete core of the One Vanderbilt project in New York, USA
Favelle Favco is responding to the trend towards electric cranes by combining Krøll drive components with its own proven machinery split deck design. Dynamic retarder systems are incorporated to cope with the reverse power problem. An example is the MK440 E with a 25 tonne main hoist and 10 tonne fly winch. In two fall condition the capacity reaches 50 tonnes. Due to the compact machinery deck with 7.15 m tail radius the walk-in electrical cabinet is part of the side mounted enlarged driver cabin unit.
Another customer-orientated design modification, developed mainly for the Chinese market, is where 5.5 tonne standard concrete block stacks replace the typical Favelle Favco compact steel ballast plates on cranes of the new F series. Largest so far is the M600F with 50/25 tonnes capacity in one or two fall mode. Maximum boom radius is 62.6 m and the tail radius is 8.4 m.
Japanese manufacturer IHI has developed its new TS series with higher capacity models and delivered the first 27 tonne capacity JCC-TS750 units. Rope reeving has been simplified by decreasing the number of sheaves and pendant ropes. In addition, the sheaves are larger in diameter than, for example, the former JCC-V600 model. IHI says these design changes will increase the life of the wire rope by 95 %.
A new cabin with a walk-in electrical cabinet is another feature making the crane more compact. As on European-style cranes the freestanding tower height and boom length are increased. The new re-inforced compact 1.9 x 1.9 m K4 tower system gives a freestanding height of 50.35 m. It is 20 % smaller and 10 % stronger, IHI says. At the maximum radius of 52 m capacity is 7.5 tonnes. Tail radius is 8 m.
A cluster of all new IHI JCC-TS750s working in Tokyo, Japan
Interior view of the new IHI comfort cabin with large windows for a better view to the side and to the crane foot
As is typical for Japanese tower cranes the 132 kW hoisting winch is operated in constant four fall configuration and gives a maximum lifting speed of 114.7 m/min. For easy dismantling by recovery derrick the largest part of the machinery deck weighs 11 tonnes. To speed up erection the slewing ring with slewing ring support and central part of the machinery deck can be transported as one unit 3.29 m wide and 3.20 m high. A new larger TS series crane to replace the JCC-V900 in the 1,000 tonne-metre class is on the drawing board.
Also from Japan, Kitagawa sets new standards in its home market with the JCL1000NK. Thanks to the new MS25 tower system combined with the standard M23 system of the same 2.05 x 2.05 m dimensions, a free standing height of 56 m can be achieved. It is a compact crane with 6.7 m tail radius and lifts 33 tonnes. Capacity at the maximum 45 m radius still 16 tonnes.
An inside view of the Kitagawa JCL1000NK ergonomic crane driver cabin with a large hook camera monitor and a multi-functional touchscreen
For easy dismantling by a roof-mounted recovery derrick all components of the upper crane can be split to pieces weighing a maximum of 10 tonnes. As is typical for Japanese tower cranes the tower system is rigid and no counterweight is needed. The standard 145 kW hoisting winch allows a hoisting speed of 102 m/min.
To reduce erection weight the climbing frame of this Kitagawa JCL1000NK can be split into an 8.8 tonne upper part and 6.7 tonne lower
Kitagawa introduced a simplified and variable hook reeving system on its small JCL105SK which it will apply to larger cranes. Changing between two and four or two to six falls can be done completely by remote control. On the drawing board are customised cranes for wind turbine construction as well as an improved version in the 1,200 tonne-metre class for high rise construction. In this case the JCL1200GK will use the same compact 2.05 x 2.05 m tower system but capacity on four falls increases to 40 tonnes up to 29 m radius while 20 tonnes can be lifted in two fall operation up to 46 m radius. A new 300 kW hoist will allow lifting speeds of 200 m/s and tail radius is kept within 8 m.
The GK (Global Kitagawa) series with improved performance, plus new transport and rigging conditions, may find a ready world market by combining the unique design features of Japanese tower cranes with the requirements of European standards.
New Comansa flat top
Spanish tower crane manufacturer Comansa is expanding its range of high capacity tower cranes with a new flat-top model: the 21LC1050. Three versions of the new crane will be available with maximum load capacities of 25, 37.5 and 50 tonnes.
The 21LC1050 and can be erected with reach of between 30 and 80 metres, with configurations available every five metres. An optional jib configuration is also available, enabling a reach of 85 metres.
Comansa says the new crane will be particularly suited to large industrial and mining applications, as well as the construction of heavy prefabricated buildings and steel structures.
The 21LC1050’s slewing design is similar to its 21LC750 and 21LC660 cranes where the jib and counter jib join directly to the slewing part. This allows fast and safe assembly, says Comansa.
The 21LC1050 also shares a large part of the jib and counter jib sections with Comansa’s smaller 21LC750 and 21LC660 models.
A number of different counter jib configurations are also possible, as the counter jib comprises five modular elements that enable up to six different configurations. For example, when the crane is assembled with its maximum 80 metre range, the counter jib radius is 31 m; this can be reduced to 27 m when the range is 50 m; or to 21 m when the reach is 30 metres. The counter jib radius can be reduced by another 0.9 metres in all its configurations by using steel counterweights, which are offered as an optional extra.
The 21LC1050 is erected on a new 2.5-metre-wide D36B tower section which is compatible with Comansa’s other mast sections of the same width. With fixing angles the 21LC1050 can reach a freestanding height of 73.3 metres; when combined with larger width sections, this increases to over 98 m.
The 21LC1050’s hoist cable is just 20 mm in diameter, enabling the drums to have a high cable capacity. The standard hoist is a 65 kW mechanism with the capacity for 720 metres of cable. It can reach speeds of up to 166 metres per minute in the 25 t and 37.5 t versions of the crane and 83 metres per minute in the 50 t version. For projects in which it is necessary to reach speeds of up to 300 metres per minute, 110 kW and 132 kW are available. In addition, drums can be issued with Lebus drums with a capacity for 1,570 metres of cable.
The crane can be switched between using a single or double trolley system, and has automatic reeving change. The single system provides improved tip loading capacity and can reach higher lifting speeds, says Comansa. With the double trolley system the crane can work with heavier loads.
New tower crane and factory
USA-headquartered crane manufacturer Manitowoc is launching the Potain MCT 565 topless tower crane. It will be sold in all markets that currently receive cranes from the Potain factory in China.
According to Manitowoc, the MCT 565 is the largest topless crane being built at its factory in Zhanjiangang, China, and it has increased capacity options to reflect the growing scale of projects in the region. It will be at officially launched at Bauma China in November 2018.
The MCT 565 will be available in three versions, offering maximum capacities of 20, 25, and 32 tonnes. All three have a maximum jib length of 80 metres. They feature a compact design that enables easy transport, claims Manitowoc, with the basic crane being able to be shipped in nine containers. The crane needs two days for erection and has one of the best load charts in its class, the company adds.
The crane has already been shown to a group of 40 potential customers from across the Asia-Pacific region.
Manitowoc has also opened a new factory in the Indian city of Chakan. The new factory replaces the company’s old facility in Prune, India. Although the new factory is smaller in size, it will have the same manufacturing capacity. The factory produces Potain MCT 85 and MC 125 cranes for customers in India, as well as surrounding markets such as Sri Lanka, Bangladesh and Nepal. Production at the factory started in the first quarter of this year.
Manitowoc’s new Potain factory in India