Gantry pivotal in Chile’s plant construction

By Niamh Marriott03 November 2021

Engineered Rigging worked on one of the largest construction projects in Chile by designing a rigging solution for the dismantling of a large-scale construction crane inside of a tunnel.

Central location
When completed, the facility will have a capacity of 530 megawatts

The Alto Maipo Hydropower plant is being built in San José de Maipo, an area strategically located 50 kilometers southeast of Santiago, the center of Chile’s power grid, home to 7 million people. With 44 per cent of the country’s citizens living in Santiago, the Alto Maipo will be an important energy source for the city and surrounding areas. When completed, the facility will have a capacity of 530 megawatts and is expected to generate approximately 2,350 gigawatt hours of electricity annually.

Construction of the hydroelectric facility began in 2013 and is expected to be completed by the end of 2021. The project includes the construction of two power plants, the Alfalfal II (264 megawatts) and the Las Lajas (267 megawatts), tunnels, four inverted siphons to cross streams, two forebays, and associated facilities, as well as 31 kilometres of new access roads, four new bridges, and 17 km of 110/220 kilovolt (kV) power transmission lines. The total investment of the Alto Maipo project is $3 billion dollars (US).

Tunnels and shafts

The Vienna-based European construction group Strabag was awarded a first partial contract for the construction of 74 kilometres of tunnels and shafts, as well as caverns, excavations, civil works, and the installation of hydro-mechanical structures. As construction of one of the tunnels of the Alfalfal II plant was nearing completion, Strabag needed to dismantle and remove an overhead construction crane that weighed 80 tons, was 8 meters high and 9 meters long.

The Enerpac Super Boom Lift SBL500 hydraulic gantry system was used for the project

Given the massive size of the crane and restricted space for manoeuvring inside of the tunnel, Engineered Rigging was consulted for a rigging solution. Their heavy lifting experts recommended the Enerpac Super Boom Lift SBL500 hydraulic gantry system for the project.

With a retracted height of just over 3 meters, the gantry easily fit under the construction crane. At its third-stage height of more than 8.5 meters, the gantry was then able to reach the full height of the crane.

With a capacity of 337 tons at its maximum height, the SBL500 safely supported the 80-ton crane while the crane’s legs were removed. The crane was then lowered and trolleyed out of the tunnel on the gantry. The gantry’s trolley capabilities the crane to be moved 23 meters through the tunnel to the exit. Once outside of the tunnel, the crane was safely dismantled at ground height.

Planning

Three weeks of planning were more than enough to coordinate the project, which included the study of the work area, logistics for transporting the heavy lifting equipment, and medical examinations so that technical personnel were certified and authorised to work on the project. Five heavy lifting specialists completed the assembly, supervision, execution, and disassembly of the SBL500 equipment.

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