Short answer
A single girder crane suits up to 20 tonnes and 25 m span for standard use; it is lighter and cheaper. A double girder crane is required beyond that, for intensive duty, large spans, process cranes or when lifting height must be maximised.
Structure and principle
A single girder crane rests on one main girder carried by two end carriages; the hoist runs under the girder. A double girder crane uses two parallel girders with a top-running trolley, bringing the hook closer to the roof and accepting heavier mechanisms.
Capacity and span
At Abra Vinç, single girder covers 1 to 20 tonnes with recommended spans under 25 m. Double girder covers 1 to 250 tonnes and large spans. Between 10 and 20 tonnes both are possible: duty cycle and lifting height then decide.
Duty and service class
A crane used a few times a day for maintenance is a light FEM class: single girder is enough. A crane integrated into production, handling loads continuously, is an intensive class: double girder, or a process crane, is designed for it.
Lifting height
In a low building, a low-headroom single girder is often the best option. In a tall building where hook travel must be maximised, double girder gains 30 to 60 cm of usable height thanks to the top-running trolley.
Total cost
Single girder is cheaper to buy, lighter on the structure and simpler to maintain. Double girder costs more but lasts longer in intensive service and accepts options: auxiliary hook, anti-collision, load cell, synchronised control.
