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Crewman Company – Cranes


Overhead cranes, also known as bridge cranes are one type of material handling equipment designed to meet the lifting requirements of medium and heavy industry needs.  An overhead crane is a crane with a lifting hoist traveling along the cane bridge between parallel runways.

An overhead bridge crane can be configured in a single girder overhead crane or double girder overhead crane design. In simple terms, a bridge girder, or beam, is the support structure that allows the trolley and hoist to move from side-to-side along the bridge. The trolley is used to precisely position the hoist prior to raising or lowering a load.

To a degree, both single and double girder cranes are equal in strength and durability. Single girder bridge cranes distinct itself from double girder bridge configuration mainly in terms of hook height, which is height your electric hoist can lift above the ground.

Due to the placement of electric hoist, the double girder crane offers more hook height, which is installed on the top of double girders rather than hung under the single girder.  

A single girder bridge crane is usually designed for the lifts under 20 tons, span less than 31.5m, or the requirement for crane services classification is under A7 and A8. 

The overhead bridge consists of one girder beam supported on each side by an end truck. The electric trolley and hoist commonly run on the bottom flange of the bridge, often called single girder underhung overhead crane. The single girder underhung crane is less expensive because of the following reasons:

  • Only one beam girder is needed to move the trolley and hoist
  • Lower cost in freight.
  • Easy installation
  • Hoist and trolley design is easier than those of double girder overhead crane.