What is a single girder overhead crane?
A single girder overhead crane is an electric overhead travelling (EOT) bridge crane built around a single bridge beam that spans the bay, supported on an end carriage at each side that runs along an elevated runway. The hoist and trolley run along the lower flange of that one beam, with the hook hanging beneath. It is the simplest and lightest bridge crane configuration, which makes it the most cost-effective choice for the majority of workshop and light-to-medium industrial lifting tasks.
Sorian designs, manufactures and installs single girder overhead cranes to AS 1418, with capacity, span and duty class matched to your application. The hoist itself — typically an electric wire-rope or chain hoist — is supplied to suit the duty and integrated into the crane.
How a single girder bridge works
The bridge beam can be a rolled I-beam or H-beam (universal beam) on lighter, shorter-span cranes, but most single girder overhead cranes use a fabricated box girder — a welded steel box that gives the best stiffness-to-weight ratio and controls deflection over longer spans and higher duty. Because the trolley is an underslung or monorail-style unit running on the bottom flange, the whole assembly is light: less steel in the bridge, smaller end carriages, and lower wheel loads transmitted into the runway and supporting structure.
That low weight is the central advantage. A lighter crane means a lighter runway, which means less load imposed on the building columns and roof structure — often decisive when a crane is being added to an existing building that wasn't originally designed for heavy overhead loads.
Single girder overhead crane — typical specifications
The ranges below are typical for the crane type across the industry, not fixed product limits. Final configuration is always confirmed by engineering calculation against AS 1418.
| Capacity (MRC) | 500 kg to ~20 t. |
| Span | Economical to roughly 20–22 m. Beyond this, deflection and bridge weight push toward a double-girder configuration. |
| Duty class | A2–A5 typical (per AS 1418 / ISO mechanism groups); A6 achievable with careful design. |
| Hook height (under-hook) | Lower than an equivalent double girder — the trolley and hoist hang below the beam, consuming headroom. |
| Runway / wheel loads | Lower than double girder — runway and building structure can often be lighter. |
| Relative cost | Typically 20–40% less than an equivalent-capacity double girder under ~20 t. |
| Auxiliary hoist | Generally not feasible — a second hoist usually requires a double-girder bridge. |
When a single girder overhead crane is the right choice
- Capacity around 20 tonnes or under — covers most workshop and light-industrial duties.
- Span up to ~20 m — typical of small to mid-size manufacturing bays.
- Moderate duty (A2–A4) — intermittent use, not running near rated load all day.
- Hook height isn't critical — you have adequate clearance below the runway.
- Cost-sensitive procurement — the same lifting capability for lower capital cost.
- Existing building with light overhead structure — lower crane and runway weight reduces load on columns and roof steel.
The classic case: a 5 t crane on a 15 m span in a fabrication shop, running perhaps 30 lifts a day at A3 duty. A single girder overhead crane is unambiguously the right answer there.
Limitations to be aware of
- Capacity ceiling — above ~20 t the single beam becomes structurally inefficient; double girder takes over.
- Reduced under-hook height — the hanging trolley costs headroom you may need for tall loads.
- Span and deflection — beyond ~20–22 m, controlling deflection drives the beam size up quickly.
- No practical auxiliary hoist — a second, smaller hook generally isn't feasible on one beam.
- Limited top-side maintenance access — there's no between-beam walkway; the trolley is serviced from below.
If several of these constraints apply to your application, a double-girder configuration is usually the better engineering decision — see the comparison links below.
Standards and in-service compliance
Single girder overhead cranes are designed and manufactured to AS 1418 (the cranes, hoists and winches series), with the duty class selected to match the expected load spectrum and number of operating cycles. Once installed, in-service inspection and maintenance follow AS 2550. Selecting the correct duty class up front is what determines the design life — under-specifying a crane that will be worked hard is a false economy.
Talk to an engineer
Sorian designs, manufactures and installs single girder overhead cranes engineered to AS 1418 — and we'll tell you honestly when a double-girder configuration would serve you better. Send through your span, capacity (MRC), duty cycle and available headroom and we'll come back with a configuration recommendation.
Frequently asked questions
What is a single girder overhead crane?
A single girder overhead crane is an EOT bridge crane that uses one bridge beam spanning the bay, with the hoist trolley running along the beam's lower flange. It is the lightest, lowest-cost bridge crane configuration and suits capacities up to around 20 tonnes.
What is the maximum capacity of a single girder overhead crane?
Single girder overhead cranes are typically used up to about 20 tonnes MRC. Above that, the single beam becomes structurally inefficient and a double-girder configuration is normally required.
Is a single girder crane cheaper than a double girder crane?
Yes. For capacities under about 20 tonnes, a single girder overhead crane is typically 20–40% cheaper than an equivalent-capacity double girder, because it uses less steel, smaller end carriages and a lighter runway. Above that capacity the cost gap closes and double girder is often the only sensible choice.
When should I choose a double girder instead?
Choose a double girder when you need capacity above ~20 tonnes, spans beyond ~22 m, high duty class (A5+), maximum under-hook height, an auxiliary hoist, or a maintenance walkway. Below those thresholds a single girder overhead crane usually does the job for less.