Double girder

 Double Girder Crane , Simply speaking main beams of a double girder crane are two. Secondly, double girder crane has two types: QD and LH, trolley are running on the double girder for both types, nevertheless, QD trolley uses a winch as lifting mechanism while LH trolley uses hoists, see below comparison picture:

 Applications: Double girder normally used in heavy duty load(above 20 ton) and long time operation(8 hours or above)