Konecranes will provide five modernised enhanced security cranes – that will not collapse when carrying a sensitive load or during certain seismic events.

These comprise two 150t (2 x 75t) cranes (which can be used in tandem to lift a 300t load) and three 12.5t cranes. The larger cranes are referred to as “A type” cranes and the smaller as “B type” cranes. This is purely a means of categorisation and not a reflection on performance or quality. Enhanced security features include strengthening to withstand a seismic event and also decreasing capacity of the B type cranes from 30t cranes to 12.5t cranes to increase safety margins.

All five cranes will be ready by the end of 2006 or early 2007 with construction being a staggered process with the smaller B type cranes currently being commissioned with final hand over around Christmas 2006.

The upper A cranes have a 58.84m span with double 75t trolleys and cabins, weighing approximately 310t. The lower B cranes have a 57m span with single trolleys and no cabins and weigh approximately 105t.

In order to meet the stringent safety requirements for nuclear related facilities, a periodic review was undertaken by BAE Systems to ensure that the existing construction of the cranes would meet modern nuclear safety requirements.

The safety review showed a shortfall against the new requirements and the cranes needed strengthening. The original cranes were supplied by JH Carruthers, now part of Konecranes UK, in 1984. The original designer, coincidentally, still works for Konecranes UK.

The original main hoist rope drums on the type A cranes were for multi-layering of the ropes. However, the new drums will be single layered to protect the ropes and provide better speed control in tandem lifting. PLC Control systems incorporate hard wired backup systems for safety, and the cranes have monitoring systems designed to trip the system in the event of an emergency.

Three independent braking systems can be employed on the main hoists, with one set acting on the rope drum in an emergency. In addition to the hard wired back up systems, additional safety features also include accurate load monitoring.

The basic structure of the cranes will remain but will be specially strengthened, the cranes will have new trolleys, cabins and new electrics, long and cross travel drives, hoists and controls. The trolleys are so designed that the units will not detach from the girder in the event of a fault – including a seismic occurrence.