Introduction
Most crane purchases go wrong not because the buyer chose a bad product, but because they chose the right product for the wrong application. A double girder crane installed where a single girder would have worked wastes capital. A single girder crane pushed into a heavy-duty cycle fails early — and that failure costs more than the money saved upfront.
This guide cuts through the noise. You will get a clear structural breakdown, a side-by-side comparison, application-specific recommendations, and a final decision checklist you can apply to your facility today. Whether you are outfitting a fabrication shop or a steel mill, the answer becomes straightforward once you understand what each crane type is actually designed to do.
What Is the Difference Between Single Girder and Double Girder Cranes?
Single Girder Crane
A single girder crane uses one main bridge beam. The hoist and trolley run along the lower flange of that beam, which positions the hook below the bridge structure. This design keeps the crane compact, light, and cost-efficient.
Double Girder Crane
A double girder crane uses two parallel main beams set apart. The trolley rides on top of the rails fixed between both beams — not below them. This shifts the hook position upward, delivering significantly more hook height for the same runway elevation.
Side-by-Side Comparison
| Feature | Single Girder | Double Girder |
| Lifting Capacity | Up to 15–20 tonnes | 10 to 250+ tonnes |
| Span Range | Economical up to ~20–22 m | 5 m to 35 m+ |
| Hook Height | Limited (hoist hangs below beam) | Higher (trolley sits on top) |
| Duty Class | A2–A5 | A5–A8 |
| Runway Load | Lower | Higher |
| Maintenance Access | From below only | Walkway access possible |
| Auxiliary Hoist | Typically not feasible | Easily accommodated |
| Cost (Supply + Install) | 20–40% less than equivalent DG | Higher capex |
When Single Girder Makes Sense
Single girder is the right call when your operation stays within these parameters:
- Capacity at or under 15 tonnes — covers most workshop and light industrial needs
- Span of 20 metres or less — avoids deflection problems that come with longer beams
- Duty class A2–A4 — moderate use, not running near rated load continuously
- Adequate headroom — hook height isn’t a constraint in your bay
- Tight procurement budget — same lifting performance at significantly lower cost
- Existing building with light overhead structure — a lighter crane puts less load on the runway and the building itself
A concrete example: a 5-tonne crane in a 15-metre span fabrication shop running 30 lifts per day at A3 duty. Single girder, without question.
When Double Girder Makes Sense
Push past any one of these thresholds and double girder becomes the engineering answer:
- Capacity above 15 tonnes — single girder becomes structurally limited
- Span over 22 metres — beam deflection at long spans demands two beams
- Duty class A5 and above — high-cycle operations need the structural redundancy
- Maximum hook height required — double girder gains 0.5–1.5 metres of under-hook height versus single girder at the same runway level
- Auxiliary hoist needed — a secondary hoist on the same trolley is standard on double girder; it doesn’t fit single girder
- Maintenance walkway required — the space between the two beams carries a walkway for safe top-level access
A real-world case: a 25-tonne crane in a 28-metre steel mill bay running at A7 duty, with an auxiliary 5-tonne hoist and the hook needing to clear coiled product on the floor. Single girder is not an option here.
Key Factors to Consider Before Choosing
Work through these six factors in sequence before committing to a configuration.
- Load weight and lift frequency — how heavy is the load, and how many lifts per shift?
- Hook height requirement — does the load need to clear fixed equipment, mezzanines, or floor-stored material?
- Bay span and travel length — what is the actual distance between runway rails?
- Duty class — match the crane’s design class to the actual working intensity, not a rough estimate
- Building structure — what wheel loads can your existing columns and roof structure carry?
- Future expansion — upgrading from single to double girder later is effectively buying a new crane; factor in where capacity might grow
Common Mistakes Buyers Make
Over-specifying by default. Many specifications are written as “double girder” as a blanket standard. If your application is 5 tonnes at A3 duty over a 14-metre span, that default costs real money without adding performance.
Under-specifying to save on capex. Forcing a 15-tonne operation into a single girder crane with a tight duty cycle shortens its design life and brings forward the replacement cost — often exceeding the initial saving.
Skipping the grey zone analysis. Capacities between 10 and 15 tonnes sit in a range where both configurations are technically feasible. The right answer comes from looking at span, duty class, hook height, and auxiliary hoist requirements together — not any single factor alone.
FAQs
Can a single girder crane be upgraded to a double girder later?
Generally no. The runway, end carriages, drives, and electrical systems are all sized for the original configuration. Upgrading is effectively a full crane replacement. If capacity growth is likely, design for it from the start.
Which crane type is better for high-frequency production environments?
Double girder. Its structural design distributes load across two beams, handles high duty cycles (A5–A8) reliably, and supports longer service intervals without compromising performance.
Does double girder always mean higher total cost?
Higher upfront, yes — typically 20–40% more for equivalent capacity. But for heavy-duty operations, double girder delivers a lower lifecycle cost through longer design life, better load distribution, and less frequent replacement.
Which crane is better when headroom is limited?
Single girder with a low-headroom hoist. The under-running trolley configuration keeps the total bridge depth compact, leaving more usable lift height within a constrained bay.
Conclusion
The choice between single and double girder is not a preference — it is an engineering outcome. Match the crane to your actual capacity, span, duty cycle, and hook height requirements, and the right configuration becomes clear.
At Heben Cranes, we design and supply both single girder and double girder overhead cranes built for real industrial demands. Every recommendation we make starts with your actual application data — span, capacity, duty class, and headroom — not a catalogue default. If you are at the decision stage or want a second opinion on an existing spec, reach out to our engineering team at hebencranes.com. We will give you a configuration recommendation in writing, backed by the numbers.
