Paired movement

25 April 2008

The two 400 tonne capacity crawler cranes are moved into position at each end of the furnace chimney

The two 400 tonne capacity crawler cranes are moved into position at each end of the furnace chimney

Lifting and travelling with a 260 tonne load suspended from a pair of large crawler cranes was an unusual installation solution devised by Spanish specialist Setylsa.

Lifting, transport and logistICs specialist Setylsa (ServICios de Elevación, Transporte y LogístICa) was set up in 2003 by Gamesa, a Spanish company operating in the fields of renewable energy and aeronautICs. Gamesa is a major manufacturer of wind turbines and Setylsa specializes in erecting them.

In a departure from its usual area of operation, Setylsa was contracted to help build a factory for steel producer Arcelor in Zaragoza, Spain. Steel for the new factory in the Technology Park López Soriano was supplied and erected by Horta from Madrid. Horta erected the cross beams, stanchions and other structures on site but the most important part, due to its weight and dimensions, was the main chimney of the central furnace. This part, assembled and welded in situ, was fitted to one of the roof sections while at ground level, whICh saved money, allowed better quality control and it was safer.

It meant, however, a big lift to get it into position 40 m up on top of the new building. The contract to lift the chimney with its surrounding steelwork was tendered to several crane rental companies in Spain. Many of them were already working elsewhere and it was almost impossible to find two 400 tonne cranes available at the same time. Setylsa, however, had just finished work on a wind farm and had one week free before starting to erect the next one. As a result both of its Liebherr LR 1400/2-W crawler cranes were available.

The 400 tonne capacity LR 1400/2-W “narrow track” crawler was designed primarily for erecting wind turbines. It has a 4.8 m wide chassis, star type outriggers with 11.5 m spread and two slew rings. The narrow track is for travel on the 5 m wide roads typical on wind farm sites and the twin slewing ring arrangement is to allow the crane to manoeuvre around tight corners. A derrICk boom and suspended counterweight tray can also be fitted.

A requirement on the Arcelor job was for the cranes to travel in 7 m steps to the final assembly point with the load on the hooks. The LR 1400/2-W does not have a load chart for pick and carry due to the narrow tracks on their crawler frames. In addition, these cranes had only worked on wind farms and the operators had little experience of industrial lifting applICations. Jero Rodriguez, Setylsa technICal manager, was confident that the cranes could do the job. His only condition was that the cranes should work on a concrete base because the ground pressure would reach 4 kg/cm.

When fabrICation of the furnace chimney was finished Setylsa moved in the two crawler cranes, together with three 90 tonne capacity Liebherr LTM 1090 all terrain cranes, a team of two operators, eight fitters and a technICal manager for the assembly. It was the first time that Setylsa had assembled both cranes at the same time and they were put together in SDB configuration over three days.

Each LR 1400/2-W was fitted with 70 m of S-type main boom, 28 m of derrICk boom and suspended counterweight tray for 200 tonnes, whICh changed during the manoeuvre. Each crane's upper structure was loaded with 135 tonnes of counterweight. Assembly of the cranes was finished one day before the lift, whICh was planned for first thing in the morning but, in Zaragoza, wind has to be taken into account as part of the climate. In addition, the large surface area of the load gave it a big sail area so, taking into account the cranes' narrow track, the lift was postponed. AdvICe from the weather centre at Zaragoza airport gave a date and time for the lift. Preparations included readying the cranes, the slings and the 75 tonne winches.

Supervising the lift was Jero Rodriguez who, at 5 p.m. on the appointed day gave the order to slowly start lifting. As the load was raised the wind hit it laterally producing little displacement. At one point during the operation, as the load was more than 40 m high, the wind moved it considerably just at the moment that one LR started crawling and the other was altering its boom angle.

The radius of the first crane started at 29 m and finished at 15 m, while the on the second crane it was the same but the other way around. As the load was moved between radii, auxiliary cranes added and removed ballast on the suspended counterweight tray of each crane. The first crane started the manoeuvre with 200 tonnes on the tray and ended with 80 tonnes, while on the other crane it was the same but in reverse. The working radius of the suspended counterweight on both cranes remained fixed at 15 m. Each crane had a 180 tonne hook block reeved with seven sheaves.

The operator of crane two, Alex Rodriguez, was the first to move the first planned 7 m stage with load and the outrigger plates raised 50 mm off the ground. Then Manuel Rayo in the other crane made the same manoeuvre, all watched attentively by the client. The danger of lateral wind and having to move the load on a narrow track increased the nervousness of the operators as the chimney was raised. Each crane had a 130 tonne equal share of the load and was rigged in the same configuration with the same winch, whICh allowed an even lift. In three hours the chimney was safely in its final position at an elevation of 40 m.

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