Lifting girdles manufactured for nuclear decommissioning
Corus Process Engineering (CPE), part of Corus Northern Engineering Services (CNES) has completed the manufacture and assembly of two 6m diameter steel lifting girdles that will be used to remove the 400 tonne heat exchangers from the reactors at Calder Hall nuclear power plant in Cumbria.
Each reactor has four vertically mounted heat exchangers. These are located externally to the reactor building and were clad for insulation and weather protection. The heat exchangers weigh around 400 tonnes and measure 27m in length with a diameter of 5.5m. This will represent the largest ever lift in the UK nuclear industry. CPE delivered the lifting girdles to its customer Nuvia Limited (formerly NUKEM Limited) at the end of February 2008, one of several contractors chosen by Sellafield Limited to decommission the Calder Hall site. Part of Nuvia’s responsibility was to design lifting girdles and cradles to enable the heat exchangers to be lifted, tailed and transported to a lay down area. The lifting girdles were required to lift and tail the vessels, which required CNES’ fabrication and machining experience.
The lifting girdles were manufactured and assembled in Scunthorpe between August 2007 and February 2008. The manufacturing process for the carbon steel girdles involved profile cutting and rolling the circular shapes, machining and flux cored arc welding the interfaces between the two girdle halves, assembly, stress relieving, finish machining, painting and delivery.
The components were manufactured on a large horizontal boring machine and two spider structures were constructed to brace the two halves of the girdle during fabrication. Each half has a trunnion fitted at 90° to the joint face, which necessitated boring a hole in the fabrication, manufacturing and fitting the trunnion to the required tolerance. The girdles were then stress relieved and finish machined on the joint faces. The fitted bolts used to fasten the two halves together measured almost 1m in length with a diameter of 115mm.
Steve Snowden, Production Control Engineer at CNES Structural Workshops commented: ‘Nuvia selected CPE because it trusted us and felt confident that we possessed the necessary technical expertise to carry out the job. We could also handle the front-end engineering that was required, plus provide all the traceability, method statements and other quality assurance-related factors that were key to the project. We also understand all the health and safety related regulations that are always our highest priority and we have the necessary fabrication, machining and surface treatment expertise to carry out the work to the required standards.’
