Double Girder or Single Girder Cranes
Girder Stength
A common misconception is that double girder bridge cranes are more durable. Based on the CMAA (Crane Manufacturers Association of America) specifications, both single and double girder cranes are equally rigid, strong, and durable. This is because single girder cranes use much stronger cross girders than double girder cranes, and single girder cranes have lateral bracing.
The Difference is in Hook Height
The principle difference between single and double girder cranes is hook height (how far above the floor your hoist will lift). Double girder cranes provide better hook height. Double girders typically allow 18-36 inches higher lift.
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. |
 |
Cost Considerations
Single girder cranes may cost less for several reasons:
- Only one cross girder is required
- The trolley is simpler
- Fright expenses are reduced
- Installation is faster
- Runway beams are lighter
Not all cranes should be designed with a single girder...
Single girder cranes have been built in spans over 100 feet and capacities of over 100 tons but typically cost effective engineering dictates that single girder cranes be considered as per the chart.
Cost Effective Single Girder Cranes |
Capacity (Tons) |
Max. Span (Feet) |
0-7.5 |
80 |
10 |
75 |
15 |
65 |
20 |
60 |
25 |
55 |
30 |
50 |
35 |
45 |
Ultra Low Headroom (ULH) trolleys
Double girder cranes typically have the hoist and trolley riding on top of the cross girders. As an option, we can provide a trolley that rides between the cross girders. This may be appropriate if:
- maximum hook height is required
- your cross girders, as well as your hoist, must be the max height above the floor
- you must minimize the distance above your runway beam
- you need the crane to be more compact
|
