The treatment facility comprised of a number of dipping tanks in a 30m long line.

The crane system would need to lift a large cage containing production items from the floor to a height above the tanks and then travel along the line of tanks lowering the cage into any particular tank and releasing it. The crane would also have to recover and relocate the cage after treatment.

There were various constraints involved and Knowsley Engineering were particularly concerned that the system should make maximum use of the very limited headroom and the tight space available around the treatment tanks.

It was decided that a completely freestanding gantry system would be installed and that two cranes would be supplied each to carry a load of up to 5t.

Headroom was very tight so special twin hoist double girder cranes were designed with each crane having the twin electric chain hoists mounted in fixed positions and suspended from brackets above the double girders.

Purpose-made lifting frames were designed to be suspended from the hoists and to easily locate on the lifting lugs of the cages. It was also decided that the system should be radio remote controlled with pendant plug-in backup and that two hand sets would be provided.

Each handset has a change over switch so that the hoists can be operated in tandem or independently.

The controls feature ‘monitored tandem lift’ as an additional safety feature in accordance with the very latest standards. If one hoist fails to operate when in tandem mode this feature prevents the other hoist from working.