Nickel helps save Leicester bridge

Metalock Engineering has been using its cast iron metal stitching expertise to repair and refurbish parapet panels, copings and cornices on the Old West Bridge that carries three lanes of traffic out of the centre of Leicester, UK. The Grade II listed wrought- and cast-iron bridge is one half of a dual carriageway, another bridge having been constructed alongside some 25 years ago. The Old West Bridge, on the A47, was surveyed four years ago and found to be in need of extensive repair and refurbishment. Traffic vibration had caused damage to the wrought-iron support beams and the cast iron decorative arches, parapets and copings.
Dew Construction was contracted by Leicester City Council to undertake the repairs and refurbishment of the main structural elements. Dew brought in Metalock Engineering, with whom the company had worked on two other bridges in Leicester, to carry out the cast iron repairs, a task in which Metalock has specialist expertise. The Metalock process is accepted as a method of repairing cracked and broken castings across a wide range of industries. One of the main advantages of the process is that it is heat-free and can be carried out in-situ or one of the company’s workshops. Apertures are jig drilled across the crack to accept multi-dumbell shaped keys manufactured from a ductile high tensile nickel alloy. The keys are peened into the apertures to become integral with the parent metal. Holes are then drilled and tapped along the line of the fracture and filled with studs, each one positioned to overlap its neighbour. This combination of keys and studs produces a rigid and pressure tight repair and final peening and hand dressing completes the operation. Once the repair has been dressed, a primer applied and finish painted it is practically undetectable. Where pieces of cast iron section were missing from decorative plaques and panels on the bridge, Metalock machined replacements from cast iron blanks and stitched them into place to restore the original design.

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