A real option - alternative lifting methods

In virtually all areas of industry, so-called alternative lifting methods, often strand jacks and hydraulic telescoping gantries, are accepted as the best option over conventional lifting, assembly and installation methods using cranes. International Cranes & Specialized Transport looks at examples of recent projects around the world.

Strand jacks are often the first choice on jobs where conventional cranes are unsuitable. This was the case on a project in Italy where strand jacks were chosen for the installation of a new arch bridge crossing a highway near Reggio Emilia in the north of the country. Cimolai Construzioni Metalliche was contracted to construct the bridge. This Italian steel structure company was responsible for the supply and installation of the arched roof structure on the Olympic Stadium in Athens for the 2004 Olympics and a similar method was used on the Italian job.

Cimolai contracted Fagioli PSC to carry out the bridge installation work. It was done in two phases. First, to prevent disruption to road traffic, the bridge deck was launched from a construction site next to the highway. For the same reason the arch, pre-assembled in six sections, was positioned on top of the bridge while the sequential launching process continued. The four central arch sections were temporarily pinned together at three points.

Next to the new bridge deck assembly and its four central arch sections three temporary towers were erected. Cantilever beams were placed on top to install the strand jacks. The central tower was equipped with a set of two L180 strand jacks, each with 12 parts of cable to give a safe working load of 180 tonnes per jack. In practice these jacks would lift a maximum of 150 tonnes. On each outer tower were two L300 strand jacks, each with 19 parts of cable for a safe working load of 290 tonnes per jack, of which 206 tonnes was used. Power packs were positioned on top of each tower.

With the strands connected at each side of the arch structure at the pivot points, first both mid sections were raised, followed by both outer sections. Once the arch had taken its final shape, it was lifted to its final elevation. Gaps remaining between the outer sections and the arch sections installed at both ends of the bridge were filled by lifting in the remaining arch sections using a mobile crane. Once those were in place the arch, suspended from the three towers, was lowered to make the arch self-supporting. The temporary pivoting pin connections were locked out. This method also allowed pre-assembly of the hanger wires to the arch sections before lifting. In this way the complicated and time consuming wire-by-wire installation method, while working at height, was almost eliminated.

Stranding on a bridge

In California, US, another bridge is taking shape using strand jack technology. The new San Francisco Oakland Bay Bridge, spanning the bay named after the cities at either end, requires installation of two 2,000 US ton (1,800 tonne) transition spans. The steel spans connect the yet to be built suspension bridge with the concrete Skyway at the Oakland side.

To lift the 300 foot long and 75 foot wide (90 x 23 m) sections to a height of approximately 200 feet (60 m) above water, Bigge Crane & Rigging in San Leandro, CA, engineered a detailed plan using computer controlled Hydrospex strand jacks. Bigge represents Dutch specialist manufacturer Hydrospex in the Americas. On top of the end of the concrete Skyway Bigge installed a pair of 60 foot (18 m) girders, cantilevered 28 feet (8.5 m) off the bridge deck. On top, and above the water, a platform was positioned housing two 365 ton (331 tonne) capacity Hydrospex strand jacks on either girder. Each jack has 31 strands and each strand has a diameter of 0.62 inches (15.7 mm). At the other, San Fransico, end no bridge construction was available yet. Temporary steel support towers were, therefore, positioned in the water at either side of the span to be lifted. Bigge provided two girders spanning 125 feet (38 m) across both towers. Again, a platform was installed on top housing four strand jacks. The platforms are capable of synchronised shifting by 8 inches (200 mm) in either longitudinal or transverse direction to allow installation of each bridge span within 1/32 inch (0.8 mm) tolerance.

At the time of writing, Bigge had installed the first span for the eastbound carriageway. It delivered the span on a barge, a process that included rotating the span through 90 degrees, using Bigge's special Scheuerle SPMTs, to fit the barge in between the final and temporary obstacles of the new bridge. Once the span was lifted to the required height in a computer synchronised lift, the temporary support towers were installed. At the Skyway side a pre-assembled tower was skidded underneath from the side, while at the other end the temporary tower was skidded in longitudinally. The westbound span will be installed in June.

Strands in industry

A recent industrial application for strand jacks was on a project to reline a blast furnace at the China Steel Corporation (CSC) facility in Kaohsiung, Taiwan. CSC has four blast furnaces on its main site in Kaohsiung producing a total of 24,000 tonnes of iron per day. Every 10 to 15 years each furnace needs to be re-lined, a process involving complete replacement of the furnace line.

Dorman Long Technology (DLT) got the US$2.4 million project as heavy lift sub-contractor and construction consultant to CSC for the installation of the new furnace line. The 3,115 tonnes of components were delivered to the slag pit in eight segments each weighing up to 477 tonnes.

Each segment was delivered by self propelled modular trailers onto two lifting beams in the slag pit, which were then lifted 14 m to the level of the skid track using eight DL-C125 climbing jacks. After lifting, each segment was skidded 98 m into the furnace house through a temporary opening created in the side of the building.

Once inside the furnace house each segment was lifted and aligned for welding using strand jacks on two levels. Eight DL-S185 (185 tonne capacity) strand jacks were used at the lower level and eight DL-S418 (418 tonne) strand jacks at high level.

All were monitored and automatically synchronised using the recently developed DL-P40 computer control system. Computer control was critical to the success of these operations, explains David Dyer, DLT managing director, to keep the loads evenly balanced between the ring of eight jacks at each level and to be able to finely adjust the welding gaps between segments to between 1 and 3 mm all around the joint.

All eight segments were lifted, skidded and aligned for welding over a period of 24 days. Lifting of the first segment to final positioning of the last one in the furnace house required 34 separate lifting and skidding operations achieved through 24 hour working and close co-ordination with the other subcontractors. The total furnace shutdown period was 94 days.

Energy industry

Alternative lifting methods also find extensive application in the construction of chemical and petrochemical complexes around the world. One example is the installation by Belgian specialist Sarens of a CO₂ absorber vessel. The vessel is part of the EG LNG project under construction in Bioko, Equatorial Guinea, Africa. Sarens is providing heavy transport and installation services on the project for all equipment to be set over 25 tonnes, including heavy lifts of 350, 460 and the 662 tonne absorber vessel.

To install the 37 m long and 5.5 m diameter vessel Sarens used its Sartower lift system, which offers lifting capacity up to 1,000 tonnes per tower, depending on the height and type of guying used. In this case a configuration of two towers, each 44 m high, was installed either side of the foundation of the absorber vessel. The Sartower configuration for this lift required limited guying, using two relatively short lattice boom sections in longitudinal direction and stabilising one tower transversely, enabling the complete Sartower set-up to fit well in the relatively small location.

Lifting trunnions either side of the vessel were rigged to a free swivelling lifting beam. That beam was attached to a cross girder beam supported by the hydro-mechanical push-up system fitted in both tower sections. The push-up motion was activated and controlled from ground level. In this way, and with the support of a tailing crawler crane, the CO₂absorber vessel was installed.

The operation follows the installation of a 1,350 tonne reactor at a Total Refinery in Gonfreville, France, using a similar but higher Sartower set up. Sarens is also using its Sartower system on a project in the Port of Rotterdam. It involves the jacking, by four Sartowers, and the moving, on 68 axle lines of Kamag SPMT, of 12 ship-to-shore container cranes each weighing 1,300 tonnes.

Power generation

Alternative lifting methods are often used on the construction and maintenance of power plants. An example was provided by international specialist Mammoet's Dubai location. The task was to move and install three sets of gas turbines and generators at the Al Aweer power station in Dubai, Middle East. The gas turbines were supplied from Germany, while the generators were manufactured in the US. The equipment was moved, one at the time, from Jebel Ali Port to Dubai, loaded on a 12 axle line Cometto modular trailer, a distance of some 65 km.

The first load to arrive on site was a 190 tonne gas turbine. Mammoet's installation method involved positioning the trailer with load in line of the foundation. The crew set up Mammoet's J&R Engineering Lift-n- Lock hydraulic gantry system. A set of two portals was installed on a track. For additional safety Mammoet provided its gantry system with additional stabilisers to increase sideways stability. In addition, the system was equipped with side shift for accurate positioning. Once the gas turbine was lifted free from the trailer and cleared the foundation of the yet-to-be-installed generator, it was moved backwards and lowered over its final foundations. The 230 tonne generator was moved and installed in the same way the day after.

Meanwhile, further East, J&R hydraulic gantries have also found application in power plant installation work. UTOC Corporation, the Tokyo, Japan-based heavy transport and lifting company, used an 800 tonne capacity 1600 Series Lift-n- Lock hydraulic gantry in the installation of a 320 tonne transformer at Kawasaki Power Station in Kawasaki. The Fuki Electrical Systems Corporation built transformer was both 8 m long and wide and measured almost 10 m high.

End of life

Applications for alternative lifting systems are also found at the other end of a power station's life. British Nuclear Fuels (BNFL) in the UK contracted Claxton International to help with the decommissioning of the Trawsfynydd nuclear power station in North Wales. The project involved the design and construction of the Claxton Boiler Lift Rig (CBLR) to be used in the dismantling of 12 reactor boilers each weighing 1,000 tonnes.

Trawsfynydd is in Snowdonia National Park and presented the BNFL decommissioning engineers with a unique challenge. The solution is to reduce the height of the two reactor buildings by half and then construct a more aesthetically pleasing building over the top as a long term storage facility.

The twelve boilers, each 40 m high and 5.5 m in diameter, are to be reduced in height by cutting them into manageable sections that can then be re-stacked within the new height limits. The work has to be done internally without removing the roof of the building. BNFL's brief to Claxton International was to design and build a system that would be used to handle these cut sections in the two main reactor buildings R1 and R2.

The challenges

Problems facing the Claxton design team included the fact that when the power station was constructed the 12 boilers were positioned and then the building was built around them. A difficulty was that the outer boilers were very close to the outer walls of the building. The original concept was to design a fixed RMG (rail mounted gantry) type crane that would straddle the boilers but it was impossible to get over the boilers at the end with a central lift due to their proximity to the walls.

Another problem was the existing 10 tonne odd-leg service gantry crane (one of four also supplied by Claxton), which works the full length of the reactor building. This crane is above the 40 m floor level with its top carriage only 75 mm from the roof beams. The proposed four point gantry for the heavy lifts needed to work in the same space as the odd-leg crane. With the two cranes virtually on the same track, both with a clearance of 75 mm from roof beams, one crane had to pass over or under the other.

The second problem was how to centralise the gantry over the end reactor boilers. Restrictions on the design were imposed by the stability of the base support. At the full extent of the long travel to its end stops the proposed concept gantry would be approx 700 mm off centre over the boilers.

Another problem was how to support the 45 m long track for the lifting gantry. The gantry had to travel on a series of 9.3 m long runway beams, each of which would be supported by a 400 mm wide wall, leaving an unsupported span of 8.9 m at each track joint 40 m up in the air.

The solution

Claxton's solution is a specially designed telescopic gantry crane. To overcome the difficulties of the service crane and the boiler lift rig working in the same space, the CBLR (Claxton Boiler Lift Rig) was designed to telescope down from its working height to allow the 10 tonne service crane to pass overhead, after which the CBLR extends again, back into position.

Centralising the hoist block of the CBLR over the end boilers was done in a way that Claxton says had not been tried before. When the CBLR travels along the runway track to the end stop position in either direction, i.e. east or west, a system comes into play that was designed to allow the hoist unit to travel 700 mm further in the direction of long travel, even though the rig has stopped following activation of the long travel limit switches.

A pair of independent hydraulic power packs are used for tower extension, long travel, hoist side shift and hoist down shift, while the hoist winch is electric. Long travel speed is 350 mm/min and side shift or cross travel speed is 1,000 mm/min. Hoist speed can be varied between 0 and 700 mm/min. Load monitoring is via two independent Kruger systems - one analogue and one digital with large LED readouts.

Each leg of the gantry is hydraulically driven in a pair from each of the two power packs by Eaton hydraulic motors through Bonfiglioli 190:1 reduction gearboxes. Laser guidance and automatic adjustment of oil flow is to ensure both sides of the gantry remain parallel during long travel. All motions are by single lever control.

The main components of the CBLR are a 600 tonne capacity Lift Systems 34PT600LX Power Tower hydraulic gantry, which supports the header beam assemblies and the interconnecting winch system link beams carrying the specially designed EMCE hoist unit. On the winch is 404 m of 40 mm diameter Diepa D1315CZ 1960 grade hoist rope. A 300 tonne working load limit, four-sheave, hook block carries eight falls of rope that gives a lift height of around 43 m.

The CBLR will be located at the 40 m floor level in each of the two reactor buildings. The boilers will be cut from the top into sections, each weighing around 100 tonnes. As each section is removed from the top of the boiler the CBLR will raise the section clear of the 40 m floor level using the winch assembly, before travelling along the runway track to a position over an “Interspace” made through all the lower floor levels. At this point the sections will be re-stacked. The operator will use the side-shift and down-shift functions to accurately position each section.

Following its construction in the UK the complete CBLR assembly, including the track, was tested and certified by BNFL and Claxton prior to dispatch to Trawsfynydd.

Around the world these non-crane methods of lifting are proving increasingly to be real alternatives to conventional approaches. This is likely to continue as alternative lifting methods, in the hands of creative professionals, prove to be geared for many ingenious and cost effective solutions in all segments of construction. •