Most people specifying a crane for the first time are choosing between configurations they have only seen from the floor. Here is what separates them, what the parts are called, and the one thing that decides service life more than the brand on the hoist.
What an overhead crane actually is
An overhead crane — bridge crane, or grua viajera in Mexico — is lifting equipment mounted on the building structure that moves load without using the floor. That is the difference from a forklift or a mobile crane: it does not compete for working space or for the aisles, and it reaches points no wheeled equipment can.
It works in three movements, and its whole anatomy comes from them. The bridge travels the length of the bay on the runway beams. The trolley crosses the bridge from side to side. The hoist raises and lowers the load. Those three axes together are what let it reach any point in the area it covers — and why a crane misaligned in just one of them compromises the entire system.
What changes from one type to the next is where that structure is carried from: the building columns, its own legs on a floor rail, or a single column.
The five configurations
- Single girder bridge crane. One bridge beam, hoist running underneath. Lighter, cheaper, lower headroom demand. The right answer for most maintenance and light production duty.
- Double girder bridge crane. Two beams with the trolley riding on top. Higher capacity, better hook height, and room to mount walkways and service platforms. This is what heavy stamping and steel handling use.
- Gantry crane. The bridge rides on legs at floor level instead of on an elevated runway — for yards, bays without adequate columns, or where you cannot load the building structure.
- Semi-gantry. One side on a runway beam, one side on a leg. Useful when only half the bay can take the load.
- Monorail. A single fixed beam with a hoist, no bridge travel. For repetitive movement along one line — a press-to-press transfer, a loading point.
The parts, by name
- Bridge — the beam or beams that span the bay and carry the load across it.
- Trolley — the carriage that travels along the bridge with the hoist on it.
- Hoist — the lifting unit: motor, drum, rope or chain, hook and brake.
- Runway beam and rail — the elevated track the bridge travels on, carried by the building columns or by its own structure.
- End trucks — the wheeled assemblies at each end of the bridge that ride the rail.
- Festoon or conductor bar — how power follows the crane along its travel.
- Controls — pendant, radio or cab, with the drives and limit switches behind them.
What actually decides service life
Not the brand. Runway alignment.
A rail that is out of level, out of gauge or out of straight makes the crane fight the structure on every pass. Wheels wear on one flange, the end trucks skew, the motors work harder than they should, and the building takes loads it was never meant to carry. We have seen cranes rebuilt twice on a runway nobody ever surveyed.
Before you replace a crane that "keeps failing", have the runway surveyed. It is frequently the cheaper answer.
What the law asks for in Mexico
NOM-006-STPS-2023 governs material handling equipment on Mexican plant floors. In practice it means periodic inspection, load testing and signed records kept on site. A foreign-owned plant is held to it exactly like anyone else, and an inspector will ask for the paperwork before they ask about the crane.
Choosing well, and keeping it that way
Choosing the right type keeps you from overpaying or coming up short. Installing it to the exact geometry keeps it from wearing out early. Maintaining it to the standard keeps it from stopping the plant — and from getting you fined. The three are the same job seen across time: the right crane, correctly set on its runway and inspected point by point, is the one that does not fail with the load in the air.
If you already know which crane your bay needs, the next step is the install — erection, relocation and runway leveling with our own crew, girder alignment and load testing, on projects from 1 to 60 tons. If the crane is already running, what applies is a maintenance program under NOM-006-STPS-2023: a 66-point inspection with signed reports.
Either way, tell us the capacity, the span of the bay and the plant location, and you get the scope back.
Common questions
Single or double girder?
Capacity, span and the hook height you need. Below roughly 10 tons on a moderate span, single girder is usually enough; above that, or where you need maximum lift under the roof, double girder earns its cost.
Can you increase the capacity of an existing crane?
Sometimes — it depends on the bridge, the end trucks and, above all, on what the runway and the building columns can take. That is a calculation, not an opinion, and we do it before quoting.
Do you supply cranes or only install them?
Both. We build and install overhead cranes, and we service equipment from any manufacturer. More than 100 bridge cranes put into service.