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The works on the Liverpool-St Helens project included the demolition of a pair of MAN type gasholders together with additional in-ground holders and other ancillary works. The MAN holders comprised of a 60m high holder located beside Network Rail running lines adjacent to the former Herculaneum Dock in Liverpool and a 90m high holder in the centre of St Helens. Both tanks were approximately 50m in diameter.
The MAN type holder is significantly different to the more conventional holders which are normally associated with gasworks. The tank shell is of a fixed volume and the storage displacement is controlled by a floating piston running on column guides within the tank.
The tight site constraints compelled deconstruction of the tanks in a reverse sequence to the construction; this required roof mounted cranes on a circular track which allowed sections of shell plate and column to be cut free and lowered to the ground. The craneage system is supported on the roof which is cut free and floated down with the piston to allow sequential deconstruction to progress.
Andun designed the tethered crane system to allow for the deconstruction works on the Liverpool holder. The crane system was also used at St Helens which additionally required a novel system of lowering the roof following significant damage to the piston which prevented it being raised.
