A common misconception is that double girder cranes are more durable! Per the industry standards , both single and double girder cranes are equally rigid, strong and durable. This is because single girder cranes use much stronger girders than double girder overhead cranes. The difference between single and double girder cranes is the effective lifting height. Generally, double girder cranes provide better lifting height. Single girder cranes cost less in many ways, only one cross girder is required, trolley is simpler, installation is quicker and runway beams cost less due to the lighter crane dead weight. The building costs are also lower.
However. not every crane can be a single girder eot crane. Generally if the crane is more than 15 ton or the span is more than 30m. a double girder crane is a better solution.
The advantages and limitations of Single / double girder cranes are as follows:
Single Girder Cranes
- Single girder bridge cranes generally have a maximum span between 6 meters to 30meters with a maximum lift of up to 15 meters.
- They can handle 1-15 tonnes with bridge speeds approaching a maximum of 40meter per minute (mpm), trolley speeds of approximately 20mpm, and hoist speeds ranging from 3 to 7mpm.
- They are candidates for light to moderate service and are cost effective for use as a standby (infrequently used) crane.
- Single girder cranes reduce the total crane cost on crane components, runway structure and building.
- Difficult to maintained due to under running hoist and unavailable of platform with crane in compare to double girder crane
Double Girder Cranes
- Double girder cranes are faster, with maximum bridge speeds, trolley speeds and hoist speeds
- They are useful cranes for a variety of usage levels ranging from infrequent, intermittent use to continuous severe service. They can lift up to 200tons.
- These can be utilized at any capacity where extremely high hook lift is required because the hook can be pulled up between the girders.
- They are also highly suitable where the crane needs to be fitted with walkways, crane lights, cabs,
- Easy to Maintenance because of attached full length platform and top running hoist on girder.