![PCS05[1] Electric wire rope hoists](http://www.cranerefurbishment.co.za/wp-content/uploads2/2012/12/PCS051.jpg)
Electrical Wire Rope Hoist used in crane industry
The principle difference between single and double girder cranes is the hook height (how far above the floor your hoist will lift). Double girder cranes provide better hook height.
Double girder cranes can provide more lift, because the hoist is placed between the cross girders rather than under them. Therefore, the depth of the cross girder is gained in switching to double girders.