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Crane TypeUnderslung (Low-Headroom) Crane
The way to use every bit of space in buildings with a low ceiling and narrow column spacing.
How it works
In an underslung crane, the bridge runs below the runway rather than above it. The runway itself is hung from the building's roof structure by hangers, so there's no need for column brackets or a separate rail-support system.
The biggest gain from this arrangement is building height: the crane's vertical footprint shrinks, leaving more lifting height under the same roof.
Cantilevered reach
In an underslung crane, the bridge can be extended beyond the runway. This lets the hook reach benches along the wall or an adjacent area — zones that are out of reach in a classic arrangement resting on column brackets.
Under the same roof, more than one underslung crane can be arranged on separate runways, running independently.
What to watch for
| Topic | What to check |
|---|---|
| Roof structure | Structurally verify the trusses and purlins can carry the hanger loads |
| Hanger points | Load is planned to spread across the support structure, not a single point |
| Tonnage | Generally low to moderate |
| Building height | Lower than a classic arrangement — the main advantage here |
| Cantilever | Reach beyond the runway is possible |
| Deflection | Roof deflection can affect crane motion; it's factored into the calculation |
Technical terms
| Term | What it means |
|---|---|
| Purlin | A secondary beam spanning between roof trusses that carries the roof load. |
| Hanger | The support member connecting the runway to the roof structure. |
| Building height demand | The vertical dimension the crane occupies from the top of the runway to the hook's highest position. |
| Deflection | The downward sag of a girder under load. |
Frequently asked questions
Can an underslung crane be installed in any building?
No. The roof structure has to carry the crane and load weight. If the structural check comes back negative, either the structure is reinforced or a legged/cantilevered arrangement is used instead.
How is it different from a monorail?
A monorail has a single rail, and the load only travels along that one line. In an underslung overhead crane the bridge spans between two runways, so the whole area can be covered.