Almost every overhead crane enquiry starts in the same place. You know roughly what you need to lift and how wide the building is, but not whether the answer is a single girder or a double girder crane. The choice affects the price, the hook height you end up with, and how the crane copes with the duty you put through it.
What the Difference Actually Is
On a single girder crane, one bridge beam spans the building and the hoist runs along the bottom flange of that beam. The design is simpler, there is less steel in the bridge, and the loads transferred into the runway and columns are lower.
On a double girder crane, two bridge beams run parallel and the hoist trolley sits on rails on top of them. That arrangement carries more load, tolerates longer spans without deflection, and lets the hook travel higher because it is no longer hanging below the beam.
Both are true overhead travelling cranes. Both run on a fixed runway. The difference is where the hoist sits, and almost everything else follows from that.
Hook Height: The Factor Most Buyers Miss
The specification that catches people out is not capacity. It is hook height.
On a single girder crane the hoist hangs below the bridge, so the top of the hook’s travel is limited by the depth of the beam plus the hoist itself. On a double girder crane the trolley sits between and above the girders, which recovers a meaningful amount of lift height in the same building.
If your building is tight under the roof and you need every millimetre of lift, that difference can decide the configuration on its own. It is also why low-headroom hoist arrangements exist, and why the useful question is never “how high is the building” but “how high does the hook need to go”.
Work upward from the load. Measure the tallest item you need to lift, add the slings or lifting beam, add clearance over whatever it must pass above, and that is your required height of lift.
Capacity and Span
Capacity and span interact. A crane that is comfortable at 5 tons over a 10 m span behaves differently at 5 tons over a 25 m span, because the longer bridge deflects more and needs more steel to control it.
As a rough guide, single girder designs cover light to medium duty across short and moderate spans very economically. As capacity and span climb together, the single girder solution needs so much steel to stay stiff that a double girder becomes both better engineered and, at some point, cheaper.
JGS Lifting supplies overhead cranes from 250 kg to 100 tons and above, in both configurations, so the recommendation is driven by the application rather than by what is on the shelf.
Duty Cycle Matters More Than Peak Load
A crane that lifts its rated load twice a day is doing a completely different job from one lifting near capacity every few minutes on a production line, even though the number on the nameplate is the same.
Duty cycle covers how often the crane lifts, how heavy the average lift is compared with the maximum, how far it travels, and how many hours a day it runs. A high duty application wears out an under-specified crane quickly, and the cost of that shows up as downtime rather than as a line on the original quote.
Where the duty is heavy, or where the load has to be rotated on its axis during the lift, the double girder configuration is generally the correct answer.
Head-to-Head Comparison
| Factor | Single Girder | Double Girder |
|---|---|---|
| Hoist position | Below the bridge beam | On a trolley above two beams |
| Usable hook height | Lower for the same building | Higher for the same building |
| Typical duty | Light to medium | Medium to heavy |
| Long spans | Needs more steel to stay stiff | Handles longer spans comfortably |
| Rotating a load on its axis | Limited | Well suited |
| Runway and column loads | Lower | Higher |
| Relative capital cost | Lower | Higher |
| Maintenance access | Access from below | Walkways possible on larger cranes |
Which One Suits Your Application
Choose a single girder crane when the duty is light to medium, headroom above the crane is not your binding constraint, the span is short to moderate, and capital cost matters. Workshops, maintenance bays, smaller fabrication shops and warehouse handling usually sit here.
Choose a double girder crane when you need maximum hook height in a fixed building, the span is long, the capacity is high, the duty cycle is heavy, or the process requires the load to be rotated or handled with a specialised below-hook attachment. Foundries, heavy fabrication, steel handling and production lines usually sit here.
If you are torn, the deciding question is usually hook height, then duty cycle, then span. Capacity alone rarely settles it.
Getting an Accurate Quote
A useful crane quote needs three numbers before anything else:
Span is the width of the building, measured between the runway rails rather than wall to wall.
Height of lift is how far the hook must travel, worked out from the load upward as described above.
Load capacity is the heaviest item you will lift, including the slings, lifting beam or magnet.
Beyond those, JGS reviews productivity targets, duty cycle, working environment, lifting functionality and budget before recommending a configuration. A crane specified against a real duty cycle costs less over ten years than one specified against a peak load alone.
Not sure which configuration your building needs?
Send us three numbers and we can put a basic crane quote together: the span of your workshop, the height of lift you need, and the load capacity. Our technical sales team will confirm the configuration against your duty cycle, environment and budget rather than quoting the cheapest steel that meets the number.
Request an overhead crane quote
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