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Contractors World 2010 Volume 1 Issue 4
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[United Kingdom - Innovative Solutions to Overcome Challenges at Nuclear Facility . . .cont]
Caption: Elevated view of the Evaporator D site, showing existing facility on the left
A Stand-Alone Structure
The whole structure is being erected on a heavily reinforced concrete slab that incorporates a containment wall around the edges. Construction of the building foundations started in May 2009. The final foundation concrete pour took place in August 2009. In total five pours were undertaken with 1661 m³ of concrete poured. It is reinforced with some 1,000 tonnes of steel.
Normally such concrete and steel structures use tower cranes to shift incoming supplies and assist in handling concrete forms, reinforcing steel, concrete etc. However, with the imposed restrictions, there was insufficient space in which to place a standard tower crane, so Costain opted for two truck-mounted self-erecting tower cranes hired through K-Lift.
The contractors had to justify to the client why this option was being taken instead of the alternative solution which would have been to hire mobile cranes as and when required.
The cranes on site are:
• Spierings SK599-AT5 with a load capacity 117 tonnes and maximum load 9000kg (up to 13m). Tip load is 1900kg and maximum radius 35m. Lifting height is 22.8m
• Spierings SK2400-AT7 with a load capacity of 269 tonnes and a maximum load of 18.000kg (up to 15.7m). Tip load 5000kg and maximum working radius of 42m. Lifting height is 3 m.
The cranes are modified with limiters to restrict their use. Both are also fitted with SMIE AC243 anti-collision and zoning systems connected wirelessly.
Although SMIE systems are often used on tower cranes, it is unusual for them to be fitted to mobile or self-erecting tower cranes. Sellafield site Construction Managers are familiar with the SMIE system as it has been used in the past on different phases of construction.
Even so, the construction team had to be satisfied that the system would provide the necessary protection to eliminate any risk to the adjacent structures. Tests were done on the cranes at the K-Lift facility in Manchester, UK.
First time for SMIE systems on truck mounted self-erecting cranes
This is the first time that SMIE has installed systems on the Spiering cranes and they worked with the manufacturers who had to modify some software to provide an interface with the cranes PLC. Although self-erecting cranes can be operated remotely, on this particular project the crane is being operated from within the cab where the SMIE display monitor is positioned.
As a rule, SMIE work closely with all the leading manufacturers to ensure that the integrity and accuracy of the anti-collision and zoning systems working in conjunction with the crane manufactures’ built in monitoring systems and the various configurations in which cranes today can be erected.
The only precaution that is necessary for the correct operation of the SMIE system is to ensure that, after the crane has been removed for servicing or other purposes, it is repositioned on carefully marked locators; otherwise the zoning and other settings need to be reconfigured.
Beth Willoughby, one of the Costain project management team told Contractors World that the use of such cranes was not only unusual but a first on this site. However, the restrictions put on the cranes meant that they had insufficient capacity to handle heavy steel forms as would normally be used on such a project.
The SMIE AC243 anti-collision and zoning system as fitted
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Publisher: Roger Lindley
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