Leg up for a big lift

22 March 2013

The temporary support structure played a critical role in replacing a 195 tonne crane at an active nuclear power plant.

Replacing the 195-tonne gantry bridge crane in an active nuclear power plant is no easy feat. When the Goesgen plant in Switzerland had to undergo the swap out in the generator building the owner opted for the construction of a massive temporary support structure to ensure the safety of the station.

Formwork specialist RMD Kwikform supplied specialist contractor VSL Heavy Lifting with a bespoke solution, involving the construction of 26m high Megashor shoring towers.

The huge gantry crane, which was contained within the generator building at the nuclear power plant had to be safely supported as it was lowered 20m down to ground level and placed onto a transport vehicle. To remove the crane safely, the 26m high temporary towers had to be compatible with VSL's high level lifting platform and strand jacking equipment, particularly as the process had to be reversed when the new crane was lifted into position.

This was a logistically challenging project that required 128t of standard and specially fabricated equipment, including header beams and nodes, to be moved from the formwork suppliers UK headquarters to the site in Switzerland. Rigorous safety requirements also needed to be met throughout the project.

VSL project manager Rolf Oesch said: "This was a demanding project that was made more challenging by its setting at a nuclear power plant. With this in mind, we demanded a solution to provide support to the 195t crane that met a very specific set of criteria. This included pre-design solution modelling and an overall high level of experience from the team. The design also had to be compatible with the heavy lifting solution we devised for the project, involving our strand jacking technology and a high level lifting platform, that would be used to lower and raise the crane.

"RMD Kwikform supplied expertise to work alongside us to maintain the high standards of health and safety required for the project. An on-site demonstrator assisted with pre-assembly and installation of the Megashor towers, in addition checking the erected equipment. Another positive aspect of [the formwork] was its modular design, as it could be simply assembled in-situ. This was a very important consideration when working with such a vast quantity of material."

To extract the crane from the generator building, a large slot was inserted in the concrete wall at the end of the building. The temporary towers were then erected against the gable end wall in specific positions, allowing the lifting equipment to be bolted to them securely. The running rail of the gantry crane could then be extended, allowing the 195t piece of equipment to be rolled out of the building and onto the tower structure. This required very precise calculations and siting of equipment, as if the crane fell or slipped, it could damage the surrounding structures that are integral to the continued operation of the active nuclear power plant.

Adam Fixter, senior project engineer at RMD Kwikform said: "In total we supplied 900 linear metres of Megashor, 1.1km of steel Superslim beams and approximately 2.5km of flat braces to the site in Goesgen. That equated to seven trailer loads of equipment, meaning that planning had to be absolutely precise to ensure the materials arrived in an order that suited the pre-assembly sequence."

"It was vital for us to recognise the importance of integration between the two teams and the engineering support required to assist in the erection process. Here RMD Kwikform supplied key staff to the project who supported the core erection teams, providing training and checking."

To prevent any unauthorised access to the Megashor towers anti vandalism walls had been installed.
The Megashor towers with the strand jack units on top lifting the new crane
Nuclear Power Plant Go¨sgen showing the assembly of the Megashor towers on temporary baseplates
Nuclear Power Plant Go¨sgen with the lowering of the old crane