Cold repair of cracks at London memorial

Edited by the Engineeringtalk editorial team Jun 4, 2001

Metalock Engineering was called in early in the restoration programme of London's Albert memorial to assess whether the Metalock process could be successfully used to repair the damaged castings

The 134-year old Albert Memorial standing opposite The Albert Hall in London has been recently restored to its former glory by English Heritage.

The memorial is constructed from elaborate cast iron sections, up to 75mm thick, clad in lead and decorated with bronze and mosaics.

There is also wrought iron, early mild steel, copper and gold.

The lead in places is 20mm thick.

In the original design there was no provision for the lead to expand, and being constrained it buckled in hot weather.

Eventually, the buckled areas cracked and split and let water into the cast iron core leading to corrosion over the years.

Corrosion jacked up the lead even more which increased the cracking.

Parts of the cast iron core were severely corroded and in some areas there were cracks.

These might have been the result of settlement over the years.

Due to these problems, English Heritage was given the task of restoring the edifice in the late eighties and giving it a 60-year life.

After many delays, the project was started in 1994 and completed in 1998.

To provide protection whilst the work was being carried out over 300 tonnes of steel scaffold tube and fittings were used for what became Europe's largest ever free-standing scaffold building covered in steel and plastic sheeting.

The memorial was systematically dismantled and the degree of necessary repair to individual elements and sub-assemblies assessed.

The aim was to retain as much of the original material as possible and this meant that badly damaged cast iron sections would be cut out, a replacement section made and fixed back on to the original to restore the overall element.

A system for cold repairing cracks and broken castings is the Metalock process and Coventry firm Metalock Engineering was called in by the contractors DGT Steel and Cladding early in the restoration programme to assess whether the process could be successfully used to repair the damaged castings and provide the 60-year life required.

The answer was positive and by the time the programme was completed Metalock had carried out nearly 100 metres of cold repairs and metal stitching of new and old castings.

Additionally, there was a considerable amount of fusion welding work which the company also undertakes.

The Metalock process is accepted as the method of repairing cracked and broken castings across a wide range of industries in a multitude of applications.

The process is carried out either in situ or in one of Metalock's workshops.

It is an entirely heat-free process, the materials used have a high tensile strength casting rigidity is restored and pressure-tight joints assured.

To effect a repair or join two components, apertures(closely drilled holes) are jig drilled across the crack/joint to accept Metalock keys which are fitted and peened into the apertures to become integral with the parent metal.

Holes are drilled and tapped along the fracture or joint line and filled with studs positioned to overlap its neighbour.

The combination of keys and studs produce a pressure-tight repair which is completed by a final peening and dressing.

Due to the nature of the work involved in restoring the memorial, components were transferred to Metalock's Dartford works to facilitate efficient repairs.

Following casting repairs, all components were cleaned and red lead painted before the lead claddings were put back with improved slip joints enabling expansion and contraction without causing splits.

At the time the memorial was originally designed and constructed the knowledge regarding reaction between dissimilar metals and the considerable difference in expansion coefficients was not as extensive as it is today.

As a result a wide range of different materials were used which over the years had caused severe damage due to insufficient protection at the interfaces.

This has now been remedied and the expertise from a host of different engineering disciplines has resulted in a successfully restored memorial.