An under-running overhead crane, also called an underslung crane, hangs from the bottom flange of the runway beams instead of riding on top of them. It is a common choice for workshops, assembly lines and maintenance bays where floor space matters.
This guide explains how it differs from a top-running crane, where it fits and what to check first.
How under-running and top-running cranes differ
A top-running crane rides on rails fixed to the top of the runway beams. An under-running crane has wheels that run on the lower flange of the beams, so the crane hangs below them.
The runway beams of an under-running crane are usually fixed to the roof structure, so no separate columns or floor-level rails are needed for the crane itself.
Benefits
- Clear floor. No crane columns or rails take up floor space.
- Good use of building height. The crane works in the space below the roof structure, which suits lower buildings.
- Flexible layouts. Tracks can include curves and switches, and several bridges can share a runway.
- Simple installation. A lighter system is often quicker to install than a top-running crane with its own supports.
- Smooth, accurate travel with inverter (VFD) control and suitable control options.
Where they are used
- Production workshops and assembly lines.
- Maintenance bays and garages.
- Warehouses and logistics areas.
- Fabrication plants.
Limits to know about
- The roof structure carries the crane and the load, so it must be checked by a structural engineer.
- Under-running cranes are usually chosen for light to medium loads. For heavy loads, wide spans or heavy duty, a top-running double girder crane is generally the better choice.
- The runway beam profile limits the wheel loads, so capacity and span are linked.
What to check before you choose
- Roof or building structure: can it carry the runway beams and the wheel loads?
- Capacity and duty class to FEM or ISO 4301.
- Span, runway length and hook height.
- Layout: straight track or curves and switches.
- Control: pendant or radio remote control.
- Environment: indoor or outdoor, temperature and dust.
How CESAN can help
CESAN builds under-running and top-running overhead cranes, with single girder cranes up to 32 t and double girder cranes up to 250 t. Our engineers will tell you which design fits your building and your duty, and CESAN handles installation and commissioning on site.
Send us your requirements
To recommend a design we need the capacity, span, runway length, hook height, duty, building structure details and control method. Send them through the enquiry form and our engineers will reply with a technical and budgetary assessment.
See our overhead cranes and the guide single girder vs double girder.